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National Cancer Institute Fact Sheet
  • Reviewed: 11/15/2011

Cancer Vaccines

Key Points

  • Cancer vaccines are designed to boost the body’s natural ability to protect itself, through the immune system, from dangers posed by damaged or abnormal cells such as cancer cells.
  • The U.S. Food and Drug Administration (FDA) has approved two types of vaccines to prevent cancer: vaccines against the hepatitis B virus, which can cause liver cancer, and vaccines against human papillomavirus types 16 and 18, which are responsible for about 70 percent of cervical cancer cases.
  • The FDA has approved one cancer treatment vaccine for certain men with metastatic prostate cancer.
  • Researchers are developing treatment vaccines against many types of cancer and testing them in clinical trials.

  1. What are vaccines?

    Vaccines are medicines that boost the immune system's natural ability to protect the body against “foreign invaders,” mainly infectious agents, that may cause disease.

    The immune system is a complex network of organs, tissues, and specialized cells that act collectively to defend the body. When an infectious microbe invades the body, the immune system recognizes it as foreign, destroys it, and “remembers” it to prevent another infection should the microbe invade the body again in the future. Vaccines take advantage of this response.

    Traditional vaccines usually contain harmless versions of microbes—killed or weakened microbes, or parts of microbes—that do not cause disease but are able to stimulate an immune response against the microbes. When the immune system encounters these substances through vaccination, it responds to them, eliminates them from the body, and develops a memory of them. This vaccine-induced memory enables the immune system to act quickly to protect the body if it becomes infected by the same microbes in the future.

    The immune system’s role in defending against disease-causing microbes has long been recognized. Scientists have also discovered that the immune system can protect the body against threats posed by certain damaged, diseased, or abnormal cells, including cancer cells(1).

  2. How do vaccines stimulate the immune system?

    White blood cells, or leukocytes, play the main role in immune responses. These cells carry out the many tasks required to protect the body against disease-causing microbes and abnormal cells.

    Some types of leukocytes patrol the circulation, seeking foreign invaders and diseased, damaged, or dead cells. These white blood cells provide a general—or nonspecific—level of immune protection.

    Other types of leukocytes, known as lymphocytes, provide targeted protection against specific threats, whether from a specific microbe or a diseased or abnormal cell. The most important groups of lymphocytes responsible for carrying out immune responses against such threats are B cells and cytotoxic (cell-killing) T cells.

    B cells make antibodies, which are large secreted proteins that bind to, inactivate, and help destroy foreign invaders or abnormal cells. Most preventive vaccines, including those aimed at hepatitis B virus (HBV) and human papillomavirus (HPV), stimulate the production of antibodies that bind to specific, targeted microbes and block their ability to cause infection. Cytotoxic T cells, which are also known as killer T cells, kill infected or abnormal cells by releasing toxic chemicals or by prompting the cells to self-destruct (a process known as apoptosis).

    Other types of lymphocytes and leukocytes play supporting roles to ensure that B cells and killer T cells do their jobs effectively. These supporting cells include helper T cells and dendritic cells, which help activate killer T cells and enable them to recognize specific threats.

    Cancer treatment vaccines are designed to work by activating B cells and killer T cells and directing them to recognize and act against specific types of cancer. They do this by introducing one or more molecules known as antigens into the body, usually by injection. An antigen is a substance that stimulates a specific immune response. An antigen can be a protein or another type of molecule found on the surface of or inside a cell.

    Microbes are recognized by the immune system as a potential threat that should be destroyed because they carry foreign or “non-self” antigens. In contrast, normal cells in the body have antigens that identify them as “self.” Self antigens tell the immune system that normal cells are not a threat and should be ignored (2).

    Cancer cells can carry both self antigens and cancer-associated antigens. The cancer-associated antigens mark the cancer cells as abnormal, or foreign, and can cause B cells and killer T cells to mount an attack against them.

    Cancer cells may also make much larger amounts of certain self antigens than normal cells. Because of their high abundance, these self antigens may be viewed by the immune system as being foreign and, therefore, may trigger an immune response against the cancer cells (1–6).

  3. What are cancer vaccines?

    Cancer vaccines are medicines that belong to a class of substances known as biological response modifiers. Biological response modifiers work by stimulating or restoring the immune system’s ability to fight infections and disease. There are two broad types of cancer vaccines:

    • Preventive (or prophylactic) vaccines, which are intended to prevent cancer from developing in healthy people; and

    • Treatment (or therapeutic) vaccines, which are intended to treat an existing cancer by strengthening the body’s natural defenses against the cancer (7).

    Two types of cancer preventive vaccines are available in the United States (see Question 5), and one cancer treatment vaccine has recently become available (see Question 8).

  4. How do cancer preventive vaccines work?

    Cancer preventive vaccines target infectious agents that cause or contribute to the development of cancer (8). They are similar to traditional vaccines, which help prevent infectious diseases, such as measles or polio, by protecting the body against infection. Both cancer preventive vaccines and traditional vaccines are based on antigens that are carried by infectious agents and that are relatively easy for the immune system to recognize as foreign.

  5. What cancer preventive vaccines are approved in the United States?

    The U.S. Food and Drug Administration (FDA) has approved two vaccines, Gardasil® and Cervarix®, that protect against infection by the two types of HPV—types 16 and 18—that cause approximately 70 percent of all cases of cervical cancer worldwide. At least 17 other types of HPV are responsible for the remaining 30 percent of cervical cancer cases (9). HPV types 16 and/or 18 also cause some vaginal, vulvar, anal, penile, and oropharyngeal cancers (10).

    In addition, Gardasil protects against infection by two additional HPV types, 6 and 11, which are responsible for about 90 percent of all cases of genital warts in males and females but do not cause cervical cancer.

    Gardasil, manufactured by Merck & Company, is based on HPV antigens that are proteins. These proteins are used in the laboratory to make four different types of “virus-like particles,” or VLPs, that correspond to HPV types 6, 11, 16, and 18. The four types of VLPs are then combined to make the vaccine. Because Gardasil targets four HPV types, it is called a quadrivalent vaccine (11). In contrast with traditional vaccines, which are often composed of weakened whole microbes, VLPs are not infectious. However, the VLPs in Gardasil are still able to stimulate the production of antibodies against HPV types 6, 11, 16, and 18.

    Cervarix, manufactured by GlaxoSmithKline, is a bivalent vaccine. It is composed of VLPs made with proteins from HPV types 16 and 18. In addition, there is some initial evidence that Cervarix provides partial protection against a few additional HPV types that can cause cancer. However, more studies will be needed to understand the magnitude and impact of this effect.

    Gardasil is approved for use in females to prevent cervical cancer and some vulvar and vaginal cancers caused by HPV types 16 and 18, and for use in males and females to prevent anal cancer and precancerous anal lesions caused by these HPV types. Gardasil is also approved for use in males and females to prevent genital warts caused by HPV types 6 and 11. The vaccine is approved for these uses in females and males ages 9 to 26. Cervarix is approved for use in females ages 9 to 25 to prevent cervical cancer caused by HPV types 16 and 18.

    The FDA has also approved a cancer preventive vaccine that protects against HBV infection. Chronic HBV infection can lead to liver cancer. The original HBV vaccine was approved in 1981, making it the first cancer preventive vaccine to be successfully developed and marketed. Today, most children in the United States are vaccinated against HBV shortly after birth (12).

  6. Have other microbes been associated with cancer?

    Many scientists believe that microbes cause or contribute to between 15 percent and 25 percent of all cancers diagnosed worldwide each year, with the percentage being lower in developed than developing countries (4, 8, 13).

    The International Agency for Research on Cancer (IARC) has classified several microbes as carcinogenic (causing or contributing to the development of cancer in people), including HPV and HBV (14). These infectious agents—bacteria, viruses, and parasites—and the cancer types with which they are most strongly associated are listed in the table below.

    Infectious AgentsType of
    Organism
    		Associated Cancers
    hepatitis B virus (HBV)virushepatocellular carcinoma (a type of liver cancer)
    hepatitis C virus (HCV)virushepatocellular carcinoma (a type of liver cancer)
    human papillomavirus (HPV) types 16 and 18, as well as other HPV typesvirus

    cervical cancer; vaginal cancer; vulvar cancer; oropharyngeal cancer (cancers of the base of the tongue, tonsils, or upper throat); anal cancer; penile cancer; squamous cell carcinoma of the skin

    Epstein-Barr virusvirusBurkitt lymphoma; non-Hodgkin lymphoma; Hodgkin lymphoma; nasopharyngeal carcinoma (cancer of the upper part of the throat behind the nose)
    Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV8)virusKaposi sarcoma
    human T-cell lymphotropic virus type 1 (HTLV1)virusadult T-cell leukemia/lymphoma
    Helicobacter pyloribacteriumstomach cancer; mucosa-associated lymphoid tissue (MALT) lymphoma
    schistosomes (Schistosoma hematobium)parasitebladder cancer
    liver flukes (Opisthorchis viverrini)parasitecholangiocarcinoma (a type of liver cancer)

  7. How are cancer treatment vaccines designed to work?

    Cancer treatment vaccines are designed to treat cancers that have already developed. They are intended to delay or stop cancer cell growth; to cause tumor shrinkage; to prevent cancer from coming back; or to eliminate cancer cells that have not been killed by other forms of treatment.

    Developing effective cancer treatment vaccines requires a detailed understanding of how immune system cells and cancer cells interact. The immune system often does not “see” cancer cells as dangerous or foreign, as it generally does with microbes. Therefore, the immune system does not mount a strong attack against the cancer cells.

    Several factors may make it difficult for the immune system to target growing cancers for destruction. Most important, cancer cells carry normal self antigens in addition to specific cancer-associated antigens. Furthermore, cancer cells sometimes undergo genetic changes that may lead to the loss of cancer-associated antigens. Finally, cancer cells can produce chemical messages that suppress anticancer immune responses by killer T cells. As a result, even when the immune system recognizes a growing cancer as a threat, the cancer may still escape a strong attack by the immune system (15).

    Producing effective treatment vaccines has proven much more difficult and challenging than developing cancer preventive vaccines (16). To be effective, cancer treatment vaccines must achieve two goals. First, like traditional vaccines and cancer preventive vaccines, cancer treatment vaccines must stimulate specific immune responses against the correct target. Second, the immune responses must be powerful enough to overcome the barriers that cancer cells use to protect themselves from attack by B cells and killer T cells. Recent advances in understanding how cancer cells escape recognition and attack by the immune system are now giving researchers the knowledge required to design cancer treatment vaccines that can accomplish both goals (17, 18).

  8. Has the FDA approved any cancer treatment vaccines?

    In April 2010, the FDA approved the first cancer treatment vaccine. This vaccine, sipuleucel-T (Provenge®, manufactured by Dendreon), is approved for use in some men with metastatic prostate cancer. It is designed to stimulate an immune response to prostatic acid phosphatase (PAP), an antigen that is found on most prostate cancer cells. In a clinical trial, sipuleucel-T increased the survival of men with a certain type of metastatic prostate cancer by about 4 months (19).

    Unlike some other cancer treatment vaccines under development, sipuleucel-T is customized to each patient. The vaccine is created by isolating immune system cells called antigen-presenting cells (APCs) from a patient’s blood through a procedure called leukapheresis. The APCs are sent to Dendreon, where they are cultured with a protein called PAP-GM-CSF. This protein consists of PAP linked to another protein called granulocyte-macrophage colony-stimulating factor (GM-CSF). The latter protein stimulates the immune system and enhances antigen presentation.

    APC cells cultured with PAP-GM-CSF constitute the active component of sipuleucel-T. Each patient’s cells are returned to the patient’s treating physician and infused into the patient. Patients receive three treatments, usually 2 weeks apart, with each round of treatment requiring the same manufacturing process. Although the precise mechanism of action of sipuleucel-T is not known, it appears that the APCs that have taken up PAP-GM-CSF stimulate T cells of the immune system to kill tumor cells that express PAP.

  9. What types of vaccines are being studied in clinical trials?

    Vaccines to prevent HPV infection and to treat several types of cancer are being studied in clinical trials.

    The list below shows the types of cancer that are being targeted in active cancer prevention or treatment clinical trials using vaccines. If you are accessing this fact sheet online, the cancer names are links to search results from NCI’s clinical trials database 1.

    Active Clinical Trials of Cancer Treatment Vaccines by Type of Cancer:
    Active Clinical Trials of Cancer Preventive Vaccines by Type of Cancer:

  10. How are cancer vaccines made?

    All cancer preventive vaccines approved by the FDA to date have been made using antigens from microbes that cause or contribute to the development of cancer. These include antigens from HBV and specific types of HPV (see Question 5). These antigens are proteins that help make up the outer surface of the viruses. Because only part of these microbes is used, the resulting vaccines are not infectious and, therefore, cannot cause disease.

    Researchers are also creating synthetic versions of antigens in the laboratory for use in cancer preventive vaccines. In doing this, they often modify the chemical structure of the antigens to stimulate immune responses that are stronger than those caused by the original antigens.

    Similarly, cancer treatment vaccines are made using antigens from cancer cells or modified versions of them. Antigens that have been used thus far include proteins, carbohydrates (sugars), glycoproteins or glycopeptides (carbohydrate-protein combinations), and gangliosides (carbohydrate-lipid combinations).

    Cancer treatment vaccines are also being developed using weakened or killed cancer cells that carry a specific cancer-associated antigen or immune cells that are modified to express such an antigen. These cells can come from a patient himself or herself (called an autologous vaccine, such as sipuleucel-T) or from another patient (called an allogeneic vaccine).

    Other types of cancer treatment vaccines are made using molecules of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) that contain the genetic instructions for cancer-associated antigens. The DNA or RNA can be injected alone into a patient as a “naked nucleic acid” vaccine, or researchers can insert the DNA or RNA into a harmless virus. After the naked nucleic acid or virus is injected into the body, the DNA or RNA is taken up by cells, which begin to manufacture the tumor-associated antigens. Researchers hope that the cells will make enough of the tumor-associated antigens to stimulate a strong immune response.

    Scientists have identified a large number of cancer-associated antigens, several of which are now being used to make experimental cancer treatment vaccines. Some of these antigens are found on or in many or most types of cancer cells. Others are unique to specific cancer types (1, 5, 6, 18–22).

  11. Can researchers add ingredients to cancer vaccines to make them work better?

    Antigens and the substances discussed in Question 10 are often not strong enough inducers of the immune response to make effective cancer treatment vaccines. Researchers often add extra ingredients, known as adjuvants, to treatment vaccines. These substances serve to boost immune responses that have been set in motion by exposure to antigens or other means. Patients undergoing experimental treatment with a cancer vaccine sometimes receive adjuvants separately from the vaccine itself (23).

    Adjuvants used for cancer vaccines come from many different sources. Some microbes, such as the bacterium Bacillus Calmette-Guérin (BCG) originally used as a vaccine against tuberculosis, can serve as adjuvants (24). Substances produced by bacteria, such as Detox B, are also frequently used. Biological products derived from nonmicrobial organisms can be used as adjuvants, too. One example is keyhole limpet hemocyanin (KLH), which is a large protein produced by a sea animal. Attaching antigens to KLH has been shown to increase their ability to stimulate immune responses. Even some nonbiological substances, such as an emulsified oil known as montanide ISA–51, can be used as adjuvants.

    Natural or synthetic cytokines can also be used as adjuvants. Cytokines are substances that are naturally produced by white blood cells to regulate and fine-tune immune responses. Some cytokines increase the activity of B cells and killer T cells, whereas other cytokines suppress the activities of these cells. Cytokines frequently used in cancer treatment vaccines or given together with them include interleukin 2 (IL2, also known as aldesleukin), interferon alpha (INF–a), and GM–CSF, also known as sargramostim (see Question 8).

  12. Do cancer vaccines have side effects?

    Vaccines intended to prevent or treat cancer appear to have safety profiles comparable to those of traditional vaccines (6). However, the side effects of cancer vaccines can vary among vaccine formulations and from one person to another.

    The most commonly reported side effect of cancer vaccines is inflammation at the site of injection, including redness, pain, swelling, warming of the skin, itchiness, and occasionally a rash.

    People sometimes experience flu-like symptoms after receiving a cancer vaccine, including fever, chills, weakness, dizziness, nausea or vomiting, muscle ache, fatigue, headache, and occasional breathing difficulties. Blood pressure may also be affected.

    Other, more serious health problems have been reported in smaller numbers of people after receiving a cancer vaccine. These problems may or may not have been caused by the vaccine. The reported problems have included asthma, appendicitis, pelvic inflammatory disease, and certain autoimmune diseases, including arthritis and systemic lupus erythematosus.

    Vaccines, like any other medication affecting the immune system, can cause adverse effects that may prove life threatening. For example, severe hypersensitivity (allergic) reactions to specific vaccine ingredients have occurred following vaccination. However, such severe reactions are quite rare.

  13. Can cancer treatment vaccines be combined with other types of cancer therapy?

    Yes. In many of the clinical trials of cancer treatment vaccines that are now under way, vaccines are being given with other forms of cancer therapy. Therapies that have been combined with cancer treatment vaccines include surgery, chemotherapy, radiation therapy, and some forms of targeted therapy, including therapies that are intended to boost immune system responses against cancer.

    Several studies have suggested that cancer treatment vaccines may be most effective when given in combination with other forms of cancer therapy (21, 25). In addition, in some clinical trials, cancer treatment vaccines have appeared to increase the effectiveness of other cancer therapies (21, 25).

    Additional evidence suggests that surgical removal of large tumors may enhance the effectiveness of cancer treatment vaccines (25). In patients with extensive disease, the immune system may be overwhelmed by the cancer. Surgical removal of the tumor may make it easier for the body to develop an effective immune response.

    Researchers are also designing clinical trials to answer questions such as whether a specific cancer treatment vaccine works best when it is administered before chemotherapy, after chemotherapy, or at the same time as chemotherapy. Answers to such questions may not only provide information about how best to use a specific cancer treatment vaccine but also reveal additional basic principles to guide the future development of combination therapies involving vaccines.

  14. What additional research is under way?

    Although researchers have identified many cancer-associated antigens, these molecules vary widely in their capacity to stimulate a strong anticancer immune response. Two major areas of research aimed at developing better cancer treatment vaccines involve the identification of novel cancer-associated antigens that may prove more effective in stimulating immune responses than the already known antigens and the development of methods to enhance the ability of cancer-associated antigens to stimulate the immune system. Research is also under way to determine how to combine multiple antigens within a single cancer treatment vaccine to produce optimal anticancer immune responses (26).

    Perhaps the most promising avenue of cancer vaccine research is aimed at better understanding the basic biology underlying how immune system cells and cancer cells interact. New technologies are being created as part of this effort. For example, a new type of imaging technology allows researchers to observe killer T cells and cancer cells interacting inside the body (27).

    Researchers are also trying to identify the mechanisms by which cancer cells evade or suppress anticancer immune responses. A better understanding of how cancer cells manipulate the immune system could lead to the development of new drugs that block those processes and thereby improve the effectiveness of cancer treatment vaccines (28). For example, some cancer cells produce chemical signals that attract white blood cells known as regulatory T cells, or Tregs, to a tumor site. Tregs often release cytokines that suppress the activity of nearby killer T cells (21, 29). The combination of a cancer treatment vaccine with a drug that would block the negative effects of one or more of these suppressive cytokines on killer T cells might improve the vaccine’s effectiveness in generating potent killer T cell antitumor responses.

Selected References
  1. Pardoll DM. Cancer immunology. In: Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKenna WG, editors. Abeloff's Clinical Oncology. 4th ed. Philadelphia: Churchill Livingstone, 2008.
  2. Murphy KM, Travers P, Walport M, editors. Janeway's Immunobiology. 7th ed. New York: Garland Science, 2007.
  3. Waldmann TA. Effective cancer therapy through immunomodulation. Annual Review of Medicine 2006;  57:65–81. [PubMed Abstract] 18
  4. Emens LA. Cancer vaccines: on the threshold of success. Expert Opinion on Emerging Drugs 2008; 13(2):295–308. [PubMed Abstract] 19
  5. Sioud M. An overview of the immune system and technical advances in tumor antigen discovery and validation. Methods in Molecular Biology 2007; 360:277–318. [PubMed Abstract] 20
  6. Pazdur MP, Jones JL. Vaccines: an innovative approach to treating cancer. Journal of Infusion Nursing 2007; 30(3):173–178. [PubMed Abstract] 21
  7. Lollini PL, Cavallo F, Nanni P, Forni G. Vaccines for tumour prevention. Nature Reviews Cancer 2006; 6(3):204–216. [PubMed Abstract] 22
  8. Frazer IH, Lowy DR, Schiller JT. Prevention of cancer through immunization: prospects and challenges for the 21st century. European Journal of Immunology 2007; 37(Suppl 1):S148–S155. [PubMed Abstract] 23
  9. Doorbar J. Molecular biology of human papillomavirus infection and cervical cancer. Clinical Science 2006; 110(5):525–541. [PubMed Abstract] 24
  10. Parkin DM. The global health burden of infection-associated cancers in the year 2002. International Journal of Cancer 2006; 118(12):3030–3044. [PubMed Abstract] 25
  11. Lowy DR, Schiller JT. Prophylactic human papillomavirus vaccines. Journal of Clinical Investigation 2006; 116(5):1167–1173. [PubMed Abstract] 26
  12. U.S. Centers for Disease Control and Prevention. A comprehensive immunization strategy to eliminate transmission of hepatitis B virus infection in the United States: recommendations of the Advisory Committee on Immunization Practices (ACIP) Part 1: immunization of infants, children, and adolescents. Morbidity and Mortality Weekly Report 2005; 54(No. RR–16):1–31. [PubMed Abstract] 27
  13. Mueller NE. Cancers caused by infections: unequal burdens. Cancer Epidemiology, Biomarkers & Prevention 2003; 12(3):237s. [PubMed Abstract] 28
  14. International Agency for Research on Cancer (2011). Agents Classified by the IARC Monographs 29 Notificación de salida 30, Volumes 1–100. Retrieved November 15, 2011.
  15. Rivoltini L, Canese P, Huber V, et al. Escape strategies and reasons for failure in the interaction between tumour cells and the immune system: how can we tilt the balance towards immune-mediated cancer control? Expert Opinion on Biological Therapy 2005; 5(4):463–476. [PubMed Abstract] 31
  16. Rosenberg SA, Yang JC, Restifo NP. Cancer immunotherapy: moving beyond current vaccines. Nature Medicine 2004; 10(9):909–915. [PubMed Abstract] 32
  17. Renkvist N, Castelli C, Robbins PF, Parmiani G. A listing of human tumor antigens recognized by T cells. Cancer Immunology and Immunotherapy 2001; 50(1):3–15. [PubMed Abstract] 33
  18. Parmiani G, Russo V, Marrari A, et al. Universal and stemness-related tumor antigens: potential use in cancer immunotherapy. Clinical Cancer Research 2007; 13(19):5675–5679. [PubMed Abstract] 34
  19. Kantoff PW, Higano CS, Shore ND, et al. Sipuleucel-T immunotherapy for castration-resistant prostate cancer. New England Journal of Medicine 2010; 363(5):411–422. [PubMed Abstract] 35
  20. Parmiani G, De Filippo A, Novellino L, Castelli C. Unique human tumor antigens: immunobiology and use in clinical trials. The Journal of Immunology 2007; 178(4):1975–1979. [PubMed Abstract] 36
  21. Finn OJ. Cancer immunology. The New England Journal of Medicine 2008; 358(25):2704–2715. [PubMed Abstract] 37
  22. Curigliano G, Spitaleri G, Dettori M, et al. Vaccine immunotherapy in breast cancer treatment: promising, but still early. Expert Review of Anticancer Therapy 2007; 7(9):1225–1241. [PubMed Abstract] 38
  23. Chiarella P, Massi E, De Robertis M, Signori E, Fazio VM. Adjuvants in vaccines and for immunisation: current trends. Expert Opinion on Biological Therapy 2007; 7(10):1551–1562. [PubMed Abstract] 39
  24. Herr HW, Morales A. History of Bacillus Calmette-Guérin and bladder cancer: an immunotherapy success story. The Journal of Urology 2008; 179(1):53–56. [PubMed Abstract] 40
  25. Emens LA. Chemotherapy and tumor immunity: an unexpected collaboration. Frontiers in Bioscience 2008; 13:249–257. [PubMed Abstract] 41
  26. Schlom J, Arlen PM, Gulley JL. Cancer vaccines: moving beyond current paradigms. Clinical Cancer Research 2007; 13(13):3776–3782. [PubMed Abstract] 42
  27. Ng LG, Mrass P, Kinjyo I, Reiner SL, Weninger W. Two-photon imaging of effector T-cell behavior: lessons from a tumor model. Immunological Reviews 2008; 221:147–162. [PubMed Abstract] 43
  28. Garnett CT, Greiner JW, Tsang KY, et al. TRICOM vector based cancer vaccines. Current Pharmaceutical Design 2006; 12(3):351–361. [PubMed Abstract] 44
  29. Zou W. Regulatory T cells, tumour immunity and immunotherapy. Nature Reviews Immunology 2006; 6(4):295–307. [PubMed Abstract] 45
Related Resources


Glossary Terms

adverse effect (AD-vers eh-FEKT)
An unexpected medical problem that happens during treatment with a drug or other therapy. Adverse effects do not have to be caused by the drug or therapy, and they may be mild, moderate, or severe. Also called adverse event.
aldesleukin (AL-des-LOO-kin)
A drug used to treat some types of cancer. It is a form of interleukin-2, a cytokine made by leukocytes (white blood cells), that is made in the laboratory. Aldesleukin increases the activity and growth of white blood cells called T lymphocytes and B lymphocytes. It is a type of biological response modifier. Also called Proleukin and recombinant human interleukin-2.
allogeneic (A-loh-jeh-NAY-ik)
Taken from different individuals of the same species. Also called allogenic.
anal (AY-nul)
Having to do with the anus. The anus is the opening of the rectum (last part of the large intestine) to the outside of the body.
antibody (AN-tee-BAH-dee)
A protein made by plasma cells (a type of white blood cell) in response to an antigen (a substance that causes the body to make a specific immune response). Each antibody can bind to only one specific antigen. The purpose of this binding is to help destroy the antigen. Some antibodies destroy antigens directly. Others make it easier for white blood cells to destroy the antigen.
antigen (AN-tih-jen)
Any substance that causes the body to make a specific immune response.
apoptosis (A-pop-TOH-sis)
A type of cell death in which a series of molecular steps in a cell leads to its death. This is the body’s normal way of getting rid of unneeded or abnormal cells. The process of apoptosis may be blocked in cancer cells. Also called programmed cell death.
autologous (aw-TAH-luh-gus)
Taken from an individual's own tissues, cells, or DNA.
B cell (… sel)
A type of immune cell that makes proteins called antibodies, which bind to microorganisms and other foreign substances, and help fight infections. A B cell is a type of white blood cell. Also called B lymphocyte.
bacillus Calmette-Guérin (buh-SIH-lus KAL-met-gay-rin)
A weakened form of the bacterium Mycobacterium bovis (bacillus Calmette-Guérin) that does not cause disease. Bacillus Calmette-Guérin is used in a solution to stimulate the immune system in the treatment of bladder cancer and as a vaccine to prevent tuberculosis. Also called BCG.
bacteria (bak-TEER-ee-uh)
A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. The singular of bacteria is bacterium.
biological response modifier therapy (BY-oh-LAH-jih-kul reh-SPONTS MAH-dih-FY-er THAYR-uh-pee)
Treatment to boost or restore the ability of the immune system to fight cancer, infections, and other diseases. Also used to lessen certain side effects that may be caused by some cancer treatments. Agents used in biological response modifier therapy include monoclonal antibodies, growth factors, and vaccines. These agents may also have a direct antitumor effect. Also called biological therapy, biotherapy, BRM therapy, and immunotherapy.
bladder cancer (BLA-der KAN-ser)
Cancer that forms in tissues of the bladder (the organ that stores urine). Most bladder cancers are transitional cell carcinomas (cancer that begins in cells that normally make up the inner lining of the bladder). Other types include squamous cell carcinoma (cancer that begins in thin, flat cells) and adenocarcinoma (cancer that begins in cells that make and release mucus and other fluids). The cells that form squamous cell carcinoma and adenocarcinoma develop in the inner lining of the bladder as a result of chronic irritation and inflammation.
Burkitt lymphoma (BER-kit lim-FOH-muh)
An aggressive (fast-growing) type of B-cell non-Hodgkin lymphoma that occurs most often in children and young adults. The disease may affect the jaw, central nervous system, bowel, kidneys, ovaries, or other organs. There are three main types of Burkitt lymphoma (sporadic, endemic, and immunodeficiency related). Sporadic Burkitt lymphoma occurs throughout the world, and endemic Burkitt lymphoma occurs in Africa. Immunodeficiency-related Burkitt lymphoma is most often seen in AIDS patients.
cancer (KAN-ser)
A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is a cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord. Also called malignancy.
carbohydrate (KAR-boh-HY-drayt)
A sugar molecule. Carbohydrates can be small and simple (for example, glucose) or they can be large and complex (for example, polysaccharides such as starch, chitin or cellulose).
cell (sel)
The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
Cervarix (SER-vuh-rix)
A vaccine used to prevent cervical cancer caused by human papillomaviruses (HPV) types 16 and 18. It is also used to prevent lesions that are caused by these viruses and that can lead to cervical, vulvar, or vaginal cancer. Cervarix is used in females aged 10-25 years. It is also being studied in the treatment of other medical conditions. It is a type of bivalent vaccine. Also called GSK-580299, HPV 16/18 L1 VLP/AS04 VAC, human papillomavirus 16/18 L1 virus-like particle/AS04 vaccine, and recombinant human papillomavirus bivalent vaccine.
cervical cancer (SER-vih-kul KAN-ser)
Cancer that forms in tissues of the cervix (the organ connecting the uterus and vagina). It is usually a slow-growing cancer that may not have symptoms but can be found with regular Pap tests (a procedure in which cells are scraped from the cervix and looked at under a microscope). Cervical cancer is almost always caused by human papillomavirus (HPV) infection.
chemotherapy (KEE-moh-THAYR-uh-pee)
Treatment with drugs that kill cancer cells.
cholangiocarcinoma (koh-LAN-jee-oh-KAR-sih-NOH-muh)
A rare type of cancer that develops in cells that line the bile ducts in the liver. Cancer that forms where the right and left ducts meet is called Klatskin tumor.
chronic (KRAH-nik)
A disease or condition that persists or progresses over a long period of time.
circulation (ser-kyoo-LAY-shun)
In the body, the flow of blood through the heart and blood vessels, and the flow of lymph through the lymph vessels.
cytokine (SY-toh-kine)
A substance that is made by cells of the immune system. Some cytokines can boost the immune response and others can suppress it. Cytokines can also be made in the laboratory by recombinant DNA technology and used in the treatment of various diseases, including cancer.
cytotoxic T cell (SY-toh-TOK-sik ... sel)
A type of immune cell that can kill certain cells, including foreign cells, cancer cells, and cells infected with a virus. Cytotoxic T cells can be separated from other blood cells, grown in the laboratory, and then given to a patient to kill cancer cells. A cytotoxic T cell is a type of white blood cell and a type of lymphocyte. Also called cytotoxic T lymphocyte and killer T cell.
dendritic cell (den-DRIH-tik sel)
A special type of immune cell that is found in tissues, such as the skin, and boosts immune responses by showing antigens on its surface to other cells of the immune system. A dendritic cell is a type of phagocyte and a type of antigen-presenting cell (APC).
deoxyribonucleic acid (dee-OK-see-RY-boh-noo-KLAY-ik A-sid)
The molecules inside cells that carry genetic information and pass it from one generation to the next. Also called DNA.
Epstein-Barr virus (ep-stine-BAR VY-rus)
A common virus that remains dormant in most people. It causes infectious mononucleosis and has been associated with certain cancers, including Burkitt lymphoma, immunoblastic lymphoma, and nasopharyngeal carcinoma. Also called EBV.
ganglioside (GANG-glee-uh-SIDE)
A complex molecule that contains both lipids (fats) and carbohydrates (sugars) and is found in the plasma (outer) membrane of many kinds of cells. Several different types of gangliosides have been identified.
Gardasil (GAR-duh-sil)
A vaccine used to prevent anal, cervical, vulvar, and vaginal cancer caused by human papillomavirus (HPV) types 16 and 18 and genital warts caused by HPV types 6 and 11. It is also used to prevent lesions that are caused by these viruses and that can lead to anal, cervical, vulvar, or vaginal cancer. Gardasil is used in males and females aged 9-26 years. Gardasil is being studied in the treatment of other medical conditions. Also called quadrivalent human papillomavirus (types 6, 11, 16, and 18) recombinant vaccine and recombinant human papillomavirus quadrivalent vaccine.
granulocyte-macrophage colony-stimulating factor (GRAN-yoo-loh-SITE-MA-kroh-FAYJ KAH-luh-nee-STIM-yoo-LAY-ting FAK-ter)
A substance that helps make more white blood cells, especially granulocytes, macrophages, and cells that become platelets. It is a cytokine that is a type of hematopoietic (blood-forming) agent. Also called GM-CSF and sargramostim.
Helicobacter pylori (HEEL-ih-koh-BAK-ter py-LOR-ee)
A type of bacterium that causes inflammation and ulcers in the stomach or small intestine. People with Helicobacter pylori infections may be more likely to develop cancer in the stomach, including MALT (mucosa-associated lymphoid tissue) lymphoma. Also called H. pylori.
helper T cell (HEL-per … sel)
A type of immune cell that stimulates killer T cells, macrophages, and B cells to make immune responses. A helper T cell is a type of white blood cell and a type of lymphocyte. Also called CD4-positive T lymphocyte.
hepatitis B virus (HEH-puh-TY-tis ... VY-rus)
A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through the blood and other body fluids. Different ways the virus is spread include sharing needles with an infected person and being stuck accidentally by a needle contaminated with the virus. Infants born to infected mothers may also become infected with the virus. Although many patients who are infected with hepatitis B virus may not have symptoms, long-term infection may lead to cirrhosis (scarring of the liver) and liver cancer. Also called HBV.
hepatitis C virus (HEH-puh-TY-tis ... VY-rus)
A virus that causes hepatitis (inflammation of the liver). It is carried and passed to others through the blood and other body fluids. Different ways the virus is spread include sharing needles with an infected person and being stuck accidentally by a needle contaminated with the virus. Infants born to infected mothers may also become infected with the virus. Although patients who are infected with hepatitis C virus may not have symptoms, long-term infection may lead to cirrhosis (scarring of the liver) and liver cancer. These patients may also have an increased risk for certain types of non-Hodgkin lymphoma. Also called HCV.
hepatocellular carcinoma (heh-PA-toh-SEL-yoo-ler KAR-sih-NOH-muh)
A type of adenocarcinoma and the most common type of liver tumor.
Hodgkin lymphoma (HOJ-kin lim-FOH-muh)
A cancer of the immune system that is marked by the presence of a type of cell called the Reed-Sternberg cell. The two major types of Hodgkin lymphoma are classical Hodgkin lymphoma and nodular lymphocyte-predominant Hodgkin lymphoma. Symptoms include the painless enlargement of lymph nodes, spleen, or other immune tissue. Other symptoms include fever, weight loss, fatigue, or night sweats. Also called Hodgkin disease.
human herpesvirus 8 (HYOO-mun HER-peez-VY-rus...)
A type of herpesvirus that may cause Kaposi sarcoma (a rare cancer that can cause skin lesions) and a type of lymphoma (cancer that begins in the lymph system), especially in patients who have a weak immune system. Also called HHV8, Kaposi sarcoma-associated herpesvirus, and KSHV.
human papillomavirus (HYOO-mun PA-pih-LOH-muh-VY-rus)
A type of virus that can cause abnormal tissue growth (for example, warts) and other changes to cells. Infection for a long time with certain types of human papillomavirus can cause cervical cancer. Human papillomavirus may also play a role in some other types of cancer, such as anal, vaginal, vulvar, penile, oropharyngeal, and squamous cell skin cancers. Also called HPV.
human T-cell lymphotropic virus type 1 (HYOO-mun T-sel LIM-foh-TROH-pik VY-rus...)
A type of virus that infects T cells (a type of white blood cell) and can cause leukemia and lymphoma. Human T-cell lymphotropic virus type 1 is spread by sharing syringes or needles, through blood transfusions or sexual contact, and from mother to child during birth or breast-feeding. Also called HTLV-1 and human T-cell leukemia virus type 1.
hypersensitivity (HY-per-SEN-sih-tih-vih-tee)
An exaggerated response by the immune system to a drug or other substance.
immune response (ih-MYOON reh-SPONTS)
The activity of the immune system against foreign substances (antigens).
immune system (ih-MYOON SIS-tem)
The complex group of organs and cells that defends the body against infections and other diseases.
interferon alfa-2b (in-ter-FEER-on AL-fuh …)
A drug used to treat some infections caused by viruses and several types of cancer. These include hairy cell leukemia, melanoma, and follicular lymphoma. It is a form of interferon alfa (a substance normally made by cells of the immune system) that is made in the laboratory. It is a type of biological response modifier. Also called IFN alpha-2B, Intron A, and recombinant interferon alfa-2b.
interleukin (in-ter-LOO-kin)
One of a group of related proteins made by leukocytes (white blood cells) and other cells in the body. Interleukins regulate immune responses. Interleukins made in the laboratory are used as biological response modifiers to boost the immune system in cancer therapy. An interleukin is a type of cytokine. Also called IL.
Kaposi sarcoma-associated herpesvirus (kuh-POH-zee sar-KOH-muh-uh-SOH-see-ay-ted HER-peez-VY-rus)
A type of herpesvirus that may cause Kaposi sarcoma (a rare cancer that can cause skin lesions) and a type of lymphoma (cancer that begins in the lymph system), especially in patients who have a weak immune system. Also called HHV8, human herpesvirus 8, and KSHV.
keyhole limpet hemocyanin (KEE-hole LIM-pet HEE-moh-SY-uh-nin)
A substance taken from a marine organism that may be linked to a specific antigen to boost the immune response to that antigen. Keyhole limpet hemocyanin is being studied as a way to increase the immune response to cancer vaccines. It is a type of immune modulator. Also called KLH.
leukapheresis (LOO-kuh-feh-REE-sis)
Removal of the blood to collect specific blood cells. The remaining blood is returned to the body.
leukocyte (LOO-koh-site)
A type of immune cell. Most leukocytes are made in the bone marrow and are found in the blood and lymph tissue. Leukocytes help the body fight infections and other diseases. Granulocytes, monocytes, and lymphocytes are leukocytes. Also called WBC and white blood cell.
lipid (LIH-pid)
Fat.
liver cancer (LIH-ver KAN-ser)
Primary liver cancer is cancer that forms in the tissues of the liver. Secondary liver cancer is cancer that spreads to the liver from another part of the body.
lymphocyte (LIM-foh-site)
A type of immune cell that is made in the bone marrow and is found in the blood and in lymph tissue. The two main types of lymphocytes are B lymphocytes and T lymphocytes. B lymphocytes make antibodies, and T lymphocytes help kill tumor cells and help control immune responses. A lymphocyte is a type of white blood cell.
metastatic (meh-tuh-STA-tik)
Having to do with metastasis, which is the spread of cancer from the primary site (place where it started) to other places in the body.
nasopharynx (NAY-zoh-FAYR-inx)
The upper part of the throat behind the nose. An opening on each side of the nasopharynx leads into the ear.
non-Hodgkin lymphoma (non-HOJ-kin lim-FOH-muh)
Any of a large group of cancers of lymphocytes (white blood cells). Non-Hodgkin lymphomas can occur at any age and are often marked by lymph nodes that are larger than normal, fever, and weight loss. There are many different types of non-Hodgkin lymphoma. These types can be divided into aggressive (fast-growing) and indolent (slow-growing) types, and they can be formed from either B-cells or T-cells. B-cell non-Hodgkin lymphomas include Burkitt lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), diffuse large B-cell lymphoma, follicular lymphoma, immunoblastic large cell lymphoma, precursor B-lymphoblastic lymphoma, and mantle cell lymphoma. T-cell non-Hodgkin lymphomas include mycosis fungoides, anaplastic large cell lymphoma, and precursor T-lymphoblastic lymphoma. Lymphomas that occur after bone marrow or stem cell transplantation are usually B-cell non-Hodgkin lymphomas. Prognosis and treatment depend on the stage and type of disease. Also called NHL.
organ (OR-gun)
A part of the body that performs a specific function. For example, the heart is an organ.
oropharyngeal cancer (OR-oh-fuh-RIN-jee-ul KAN-ser)
Cancer that forms in tissues of the oropharynx (the part of the throat at the back of the mouth, including the soft palate, the base of the tongue, and the tonsils). Most oropharyngeal cancers are squamous cell carcinomas (cancer that begins in flat cells lining the oropharynx).
penis (PEE-nis)
An external male reproductive organ. It contains a tube called the urethra, which carries semen and urine to the outside of the body.
precancerous (pree-KAN-seh-rus)
A term used to describe a condition that may (or is likely to) become cancer. Also called premalignant.
prophylactic (PROH-fih-LAK-tik)
In medicine, something that prevents or protects.
prostate cancer (PROS-tayt KAN-ser)
Cancer that forms in tissues of the prostate (a gland in the male reproductive system found below the bladder and in front of the rectum). Prostate cancer usually occurs in older men.
prostatic acid phosphatase (prah-STA-tik A-sid FOS-fuh-tays)
An enzyme produced by the prostate. It may be found in increased amounts in men who have prostate cancer. Also called PAP.
protein (PROH-teen)
A molecule made up of amino acids that are needed for the body to function properly. Proteins are the basis of body structures such as skin and hair and of substances such as enzymes, cytokines, and antibodies.
Provenge (PROH-venj)
A drug used to treat prostate cancer that has spread. It is made from immune system cells collected from a patient with prostate cancer. The cells are treated with a protein that is made by combining a protein found on prostate cancer cells with a growth factor. When the cells are injected back into the patient, they may stimulate T cells to kill prostate cancer cells. Provenge is a type of vaccine and a type of cellular adoptive immunotherapy. Also called APC8015 and sipuleucel-T.
radiation therapy (RAY-dee-AY-shun THAYR-uh-pee)
The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Also called irradiation and radiotherapy.
ribonucleic acid (RY-boh-noo-KLAY-ik A-sid)
One of two types of nucleic acid made by cells. Ribonucleic acid contains information that has been copied from DNA (the other type of nucleic acid). Cells make several different forms of ribonucleic acid, and each form has a specific job in the cell. Many forms of ribonucleic acid have functions related to making proteins. Ribonucleic acid is also the genetic material of some viruses instead of DNA. Ribonucleic acid can be made in the laboratory and used in research studies. Also called RNA.
sargramostim (sar-GRA-moh-stim)
A substance that helps make more white blood cells, especially granulocytes, macrophages, and cells that become platelets. It is a cytokine that is a type of hematopoietic (blood-forming) agent. Also called GM-CSF and granulocyte-macrophage colony-stimulating factor.
sipuleucel-T (SY-puh-LOO-sel...)
A drug used to treat prostate cancer that has spread. It is made from immune system cells collected from a patient with prostate cancer. The cells are treated with a protein that is made by combining a protein found on prostate cancer cells with a growth factor. When the cells are injected back into the patient, they may stimulate T cells to kill prostate cancer cells. Sipuleucel-T is a type of vaccine and a type of cellular adoptive immunotherapy. Also called APC8015 and Provenge.
stomach cancer (STUH-muk KAN-ser)
Cancer that forms in tissues lining the stomach. Also called gastric cancer.
surgery (SER-juh-ree)
A procedure to remove or repair a part of the body or to find out whether disease is present. An operation.
synthetic (sin-THEH-tik)
Having to do with substances that are man-made instead of taken from nature.
systemic lupus erythematosus (sis-TEH-mik LOO-pus AYR-ih-THEE-muh-TOH-sus)
A chronic, inflammatory, connective tissue disease that can affect the joints and many organs, including the skin, heart, lungs, kidneys, and nervous system. It can cause many different symptoms; however, not everyone with systemic lupus erythematosus has all of the symptoms. Also called lupus and SLE.
T cell (... sel)
A type of immune cell that can attack foreign cells, cancer cells, and cells infected with a virus. T cells can also help control immune responses. A T cell is a type of white blood cell. Also called T lymphocyte and thymocyte.
targeted therapy (TAR-geh-ted THAYR-uh-pee)
A type of treatment that uses drugs or other substances, such as monoclonal antibodies, to identify and attack specific cancer cells. Targeted therapy may have fewer side effects than other types of cancer treatments.
therapeutic (THAYR-uh-PYOO-tik)
Having to do with treating disease and helping healing take place.
tissue (TIH-shoo)
A group or layer of cells that work together to perform a specific function.
tuberculosis (too-BER-kyoo-LOH-sis)
A disease caused by a specific type of bacteria that spreads from one person to another through the air. Tuberculosis can affect many parts of the body, but most often affects the lungs. A person may not have symptoms of tuberculosis for years, but they may appear when the patient becomes ill with a serious condition like diabetes, AIDS, or cancer. Tuberculosis can usually be treated and cured with antibiotics. Also called TB.
tumor (TOO-mer)
An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancer), or malignant (cancer). Also called neoplasm.
vaccination (VAK-sih-NAY-shun)
Treatment with a vaccine.
vaginal (VA-jih-nul)
Having to do with the vagina (the birth canal).
virus (VY-rus)
In medicine, a very simple microorganism that infects cells and may cause disease. Because viruses can multiply only inside infected cells, they are not considered to be alive.
vulva (VUL-vuh)
The external female genital organs, including the clitoris, vaginal lips, and the opening to the vagina.
white blood cell (hwite blud sel)
A type of immune cell. Most white blood cells are made in the bone marrow and are found in the blood and lymph tissue. White blood cells help the body fight infections and other diseases. Granulocytes, monocytes, and lymphocytes are white blood cells. Also called leukocyte and WBC.

Table of Links

1http://www.cancer.gov/clinicaltrials/search
2http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38767&format =1&tt=1
3http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38958&format =1&tt=1
4http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38832&format =1&tt=1
5http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=37892&tt=1&a mp;format=1
6http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=41646&tt=1&format=1
7http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38140&format =1&tt=1
8http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=41557&idtype=5&
diagnosis=41186&format=1&tt=1
9http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=41557&idtype=5&
diagnosis=40209&format=1&tt=1
10http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38833&format =1&tt=1
11http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=42947&format =1&tt=1
12http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38957&tt=1&format=1
13http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=41487&format =1&tt=1
14http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=38782&&f ormat=1&tt=1
15http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=40461&format =1&tt=1
16http://www.cancer.gov/search/clinicaltrialslink?id=491925&idtype=5&diag
nosis=37892&forma t=1&tt=4
17http://www.cancer.gov/search/clinicaltrialslink?id=41557&idtype=5&diagn
osis=40461&tt=4&format=1
18http://www.ncbi.nlm.nih.gov/pubmed/16409137
19http://www.ncbi.nlm.nih.gov/pubmed/18537522
20http://www.ncbi.nlm.nih.gov/pubmed/17172735
21http://www.ncbi.nlm.nih.gov/pubmed/17505219
22http://www.ncbi.nlm.nih.gov/pubmed/16498443
23http://www.ncbi.nlm.nih.gov/pubmed/17972339
24http://www.ncbi.nlm.nih.gov/pubmed/16597322
25http://www.ncbi.nlm.nih.gov/pubmed/16404738
26http://www.ncbi.nlm.nih.gov/pubmed/16670757
27http://www.ncbi.nlm.nih.gov/pubmed/16371945
28http://www.ncbi.nlm.nih.gov/pubmed/12646517
29http://monographs.iarc.fr/ENG/Classification/ClassificationsGroupOrder.pdf
30http://www.cancer.gov/espanol/global/politicas/page8
31http://www.ncbi.nlm.nih.gov/pubmed/15934826
32http://www.ncbi.nlm.nih.gov/pubmed/15340416
33http://www.ncbi.nlm.nih.gov/pubmed/11315507
34http://www.ncbi.nlm.nih.gov/pubmed/17908956
35http://www.ncbi.nlm.nih.gov/pubmed/20818862
36http://www.ncbi.nlm.nih.gov/pubmed/17277099
37http://www.ncbi.nlm.nih.gov/pubmed/18565863
38http://www.ncbi.nlm.nih.gov/pubmed/17892423
39http://www.ncbi.nlm.nih.gov/pubmed/17916047
40http://www.ncbi.nlm.nih.gov/pubmed/17997439
41http://www.ncbi.nlm.nih.gov/pubmed/17981543
42http://www.ncbi.nlm.nih.gov/pubmed/17606707
43http://www.ncbi.nlm.nih.gov/pubmed/18275480
44http://www.ncbi.nlm.nih.gov/pubmed/16454749
45http://www.ncbi.nlm.nih.gov/pubmed/16557261
46http://www.cancer.gov/cancertopics/factsheet/Therapy/biological
47http://www.cancer.gov/cancertopics/factsheet/prevention/HPV-vaccine
48http://www.cancer.gov/clinicaltrials/learningabout/Taking-Part-in-Cancer-Treatm
ent-Research-Studies
49http://www.cancer.gov/cancertopics/understandingcancer/HPV-vaccine
50http://www.cancer.gov/cancertopics/understandingcancer/immunesystem