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Targeted Therapies for Prostate Cancer Tutorial

New Approaches Under Investigation in Clinical Trials

In This Section:

 

Targeting angiogenesis in prostate cancer

Researchers running clinical trials are finding new ways to target prostate cancer. These experimental approaches have not yet been approved by the FDA, so clinical trials may be the only opportunity for patients to access them at present.

Shown is an image of two clinical researchers in a laboratory. Screen text reads: Clinical trials may be the only opportunity for patients to access new treatments.

Blocking angiogenesis, although still investigational, is another viable strategy for cancer therapy. Targeted therapies such as Avastin (generic drug name bevacizumab), Revlimid (generic drug name lenalidomide), and Thalomid (generic drug name thalidomide) interfere with specific molecules involved in angiogenesis, interrupting the essential blood supply to prostate tumors.

Shown is the edge of a blood vessel running across the top of the screen. The rest of the screen is filled with a layer of pink normal cells and a cluster of green cells labeled 'Prostate Cancer'. Branching off from the main blood vessel is an auxiliary blood vessel labeled 'Angiogenesis.' The auxiliary blood vessel is providing the blood supply essential for the survival of the cancer cell cluster. Screen text reads: Blocking angiogenesis is another viable strategy for cancer therapy.

Also under investigation is Celebrex (generic drug name celecoxib), which may stop the growth of tumor cells by blocking some necessary enzymes and by blocking blood flow to the tumor.

Shown is the edge of a blood vessel running across the top of the screen. The rest of the screen is filled with a layer of pink normal cells and a cluster of green cells labeled 'Prostate Cancer'. A red X labeled 'Angiogenesis' indicates that the formation of blood vessels is blocked. As a result, several of the cancer cells have fragmented into small gray vesicles, indicating that they have undergone apoptosis. Title on the left side of the screen reads: Targeted therapies under investigation. The bulleted list reads: Avastin, Revlimid, Thalomid, Celebrex.

 

Testing a Poxvirus therapeutic vaccine

Researchers running clinical trials are finding new ways to target prostate cancer. These experimental approaches have not yet been approved by the FDA, so clinical trials may be the only opportunity for patients to access them at present.

Shown are two healthcare providers looking at images on a computer screen. Screen text reads: Clinical trials may be the only opportunity for patients to access them at present.

A cancer vaccine, Prostvac™ (generic drug name PSA-TRICOM), made with two forms of Poxvirus that do not cause disease in humans, is being tested in Phase II and Phase III clinical trials as treatment for castration-resistant prostate cancer.

Shown is a group of cancer patients labeled 'Volunteer Cancer Patients.' The screen title reads: Prostvac™ is being tested in phase II and phase III clinical trials as treatment for castration-resistant prostate cancer. Boxes at the bottom of the screen read 'Phase II' and 'Phase III.'

Prostvac™ contains recombinant viruses that have been altered in the laboratory to express prostate-specific antigen, or PSA, a protein found mainly in prostate cells.

Shown are illustrations of several Poxviruses. Screen text reads: Prostvac™ contains recombinant viruses that have been altered in the laboratory to express prostate-specific antigen, or PSA, a protein found mainly in prostate cells.

The recombinant virus infects cells at the injection site, causing them to express PSA.

Shown is a close-up of a man's upper left chest, shoulder, and arm. A silhouette of the circulatory system is shown within the body. A syringe injecting a Poxvirus therapeutic vaccine into the arm results in an area of infection that triggers an immune response.

This PSA is then taken up and processed by antigen-presenting cells, including dendritic cells, which present antigens to killer T cells. The killer T cells respond by destroying cells that express PSA.

Shown is a dendritic cell that has processed the PSA antigen and is presenting pieces of it to a killer T cell. The killer T cell now recognizes PSA as a foreign protein.

Shown are three killer T cells activated to recognize PSA as foreign. The killer T cells are shown surrounding a cancer cell that expresses PSA, and the cancer cell is being destroyed. The cancer cell, its PSA antigen, and the killer T cells are all labeled.

More Information:

Prostvac

A Phase I study of PROSTVAC ™ and Ipilimumab (anti-CTLA4 antibody) demonstrated the utility of this approach.

 

Testing ways to regulate the immune response of therapeutic vaccines

Adding specific cytokines or antibodies to regulate the action of therapeutic vaccines is being tested in clinical trials.

Sometimes it is important to heighten the reactivity of a cancer vaccine. Interleukin 15 (Il-15) is a cytokine that is being tested in combination with other experimental treatments to do this. This molecule can further activate natural killer cells and T cells without activating the regulatory immune cells that normally signal for an immune response to draw to a close.

Shown on the left is an outline of a male body with a lymphatic system and prostate cancer. A therapeutic vaccine carrying the cytokine Interleukin 15 has been administered. On the right is an inset circle coming from the groin area showing a layer of pink normal cells with an embedded mass of green cancer cells. Three activated killer T cells are shown recognizing the cancer cells as foreign. Screen title is: Cytokines. Text at the bottom of the screen is 'Interleukin 15 can further activate natural killer cells and T cells.'

Other times it is necessary to extend the length of time that a vaccine can target cancer cells. Clinical researchers do this by adding anti-CTLA4 antibody to protocols. Anti-CTLA4 slows down the regulatory immune cells that usually signal for the immune response to end.

Shown on the left is an outline of a male body with a lymphatic system and prostate cancer. A therapeutic vaccine carrying anti-CTLA4 antibody has been administered. On the right is an inset circle coming from the groin area showing a layer of pink normal cells with an embedded mass of black, dying cancer cells. Two immune cells are shown destroying the cancer cells. Screen title is: Antibodies. Text across the bottom of the screen is: Anti-CTLA4 slows down the immune response to allow the vaccine time to work.

Self Test

Questions

  1. What are some other experimental targeted approaches being investigated for their potential as future prostate cancer treatments?
    1. Agents that disrupt the blood supply to the prostate cancer.
    2. Recombinant viruses that increase the PSA signal so killer cells can attack the cancer.
    3. Cytokines or antibodies to prolong the immune response once it starts.
    4. All of the above.

Answers

  1. How does docetaxel target prostate cancer?
    1. Agents that disrupt the blood supply to the prostate cancer. There is a better answer.
    2. Recombinant viruses that increase the PSA signal so killer cells can attack the cancer. There is a better answer.
    3. Cytokines or antibodies to prolong the immune response once it starts. There is a better answer.
    4. All of the above. Correct.