With the advent of gene therapy, scientists and researchers now believe it should be possible to create prostate-targeted vaccines that would cause an immune response to search for, locate, and destroy prostate cancer.

Provenge, also known as APC8015, is a prostate cancer vaccine approved for use by the FDA in 2010.

APC or antigen presenting cells are involved in the initiation and expansion of cellular immune responses to carrier and virus-infected cells. Dendritic cells, the most potent APCs, are trained to detect cancer cells by exposure to the target (Valone et al., 2001). Dendritic cells potentiate the effectiveness of the initiation of T-cell and B-cell (lymphocytes) mediated immune responses. Provenge activates these cells to mount a more effective immune response against prostate cancer.

APCs do not kill cancer cells; rather, they alert effector cells, like T-cells, to the presence of cancer. T-cells are the immune system’s attack cells, and thus they attack and destroy the cancer cells. Provenge consists of autologous dendritic cells loaded with PA2024, a fusion protein consisting of human prostatic acid phosphatase (PAP) coupled to a targeting molecule, granulocyte-macrophage colony-stimulating factor (GM-CSF). PAP is a tissue-specific antigen that is expressed only by normal prostate cells and is in greater than 90 percent of cancer cells of the prostate. GM-CSF is a cytokine, which regulates the survival, proliferation, and differentiation of granulocyte (white blood cells) and macrophage progenitors (cells that destroy other cells by “eating” them) and which are a potent stimulator of dendritic cells (Rini and Small, 2001).
Potential adverse effects can occur during the collection of dendritic cell precursors (leukopheresis) and during and after reinfusion of Provenge. During apheresis, patients may experience citrate toxicity (numbness and tingling around the mouth and hands) and, rarely, arrhythmias due to low calcium secondary to anticoagulants used during apheresis. In addition, hypovolemia (decrease in the volume of circulating blood) and low blood pressure may occur, as well as pain, bruising, and infection at the venous catheter site. Reinfusion can be complicated by chills, fevers, muscle ache, pain, and fatigue (Burch et al., 2000). In addition to apheresis or infusion- related incidents, there is the theoretical possibility that patients may experience prostatitis due to the induction of an immune response to PAP; therefore, the PSA may rise without disease progression.

In the future, Provenge may be used to delay the need for androgen- deprivation therapy. It is hoped that Provenge will be given to prostate cancer patients at high risk of developing a recurrence or at the first detection to enhance the immune system’s ability to eradicate cancer cells in the microscopic stage before development of a tumor.