Melanoma Research

Clinical trials are investigating exciting new treatments for skin cancer and melanoma. Gene therapy research for melanoma is an especially vital and encouraging branch of ongoing clinical trials.

Gene therapy research attempts to introduce genetic material into cancerous melanocytes making them more “visible” to the immune system. Alternately, genetic material may be added to a tumor that makes the skin cancer cells more vulnerable to the effects of chemotherapy or other medication.

The Search for a Melanoma Vaccine

Most people are familiar with vaccines. Vaccines for measles, meningitis and chicken pox protect people from those diseases. A melanoma vaccine would not be preventive. Instead, the treatment would be used to prevent the disease from recurring after surgical treatment, or aid the immune system in recognizing a tumor that is already present but has gone unnoticed.

The human immune system is not very good at telling the difference between cancerous and healthy tissue. For a cancer vaccine to work, the treatment must make it easier for the immune system to tell the two types of tissue apart.

Four main types of cancer vaccine are currently under investigation in clinical trials. Researchers hope that these studies will lead to an FDA-approved melanoma vaccine in the near future.

Antigen Vaccine: An antigen vaccine takes proteins from melanoma cells or healthy melanocytes. These proteins, or antigens, can trigger immune responses. The antigens are combined with substances that also trigger the immune system. Once reintroduced into the body, the modified antigens are targeted by the immune system and destroyed. In theory, this teaches the immune system to target the same antigens in cancerous tissue.

Proteins under investigation for antigen vaccines include tyrosinase, gp100, MART-1 peptides, and tyrosinase-related protein-2 (TRP-2).

Dendritic Cell Vaccine: Dendritic cells are white blood cells (WBC) that play an important role in the immune system. Melanoma antigens are gathered from the tumor and exposed to the patient’s own dendritic cells in petri dishes. Once the dendritic cells “learn” to perceive the antigens as a threat, they are reintroduced into the bloodstream. There, the WBCs activate immune “T” cells, which multiply and destroy cancer cells containing the antigens.

DNA Vaccine: Strands of DNA from melanoma cells are reproduced in the laboratory and serve as antigens for antigen-presenting cells (APCs). The antigen-infected APCs are then reintroduced into the body, where they present the DNA antigens to the immune system. In this way, the immune system recognizes the DNA as “bad,” and can then go on to attack the melanoma cells that harbor the same ‘bad” DNA.

Whole Cell Vaccine: Whole cell vaccines were the first type of cancer vaccines evaluated in clinical trials, and several vaccines may receive FDA approval over the next few years. Dead tumor cells are removed either from the patient of from another person and provide many different antigens that can be used to train the immune system.

Clinical trials have proven that some people live longer when treated with modified whole cells. Material taken from the patient’s own tumor produces the best response, but such “individualized” treatment is quite expensive.

Current Gene Therapy Research: Allovectin-7

Allovectin-7 is an experimental medication that stimulates the immune system in a way that is slightly different from the vaccines discussed above. Allovectin-7 is injected directly into the tumor, where it causes melanoma tumors to express a gene known as HLA-B7. Because HLA-B7 is not usually found in humans, research suggests that its presence may cause tumor cells to trigger the immune system, in effect bringing about their own destruction.

Resources

American Cancer Society. (nd). New treatments on horizon for melanoma. Retrieved May 22, 2003, from www.cancer.org/docroot/NWS/content/NWS_1_1x_New_Treatments_On_Horizon_For_Melanoma.asp.

American Cancer Society. (nd). What’s new in melanoma research and treatment? Retrieved May 21, 2003, fromwww.cancer.org/docroot/cri/content/cri_2_4_6x_whats_new_in_melanoma_research_and_treatment_50.asp.

National Cancer Institute. (2003). Cancer vaccine fact sheet. Retrieved May 22, 2003, from www.cancer.gov/newscenter/pressreleases/cancervaccines.

Vical. (nd). Allovectin-7. Retrieved May 22, 2003, from www.vical.com/products/allovectin7.htm.