Leisha A. Emens, M.D.

Funded by the Kay Yow Cancer Fund

Current therapies fail to cure 40% of breast cancer patients, who relapse and die from drug-resistant disease. Immune-based therapies work differently than drugs that destroy tumor cells directly by recruiting the patient’s own immune system to seek out and kill tumor cells. Immune-based therapies are not limited by drug resistance, are highly specific, and typically have few side effects. Importantly, they uniquely result in a durable therapeutic impact due to memory. Immune-based therapy includes vaccines and antibodies. Vaccines activate long-lasting T cells that kill existing cancers, and can remember to kill tumors should they arise again. Antibodies target proteins such as HER-2 on cancer cells, and immune cells bind these antibodies to kill tumors. Herceptin^R is a HER-2-specific antibody that significantly improves the survival of patients with early and metastatic HER-2^hi breast cancer.

Because tumors arise from the patient’s own tissues, the immune system sees them as “self” rather than as dangerous invaders (like an infection). A special type of regulatory T cell (Treg) keeps the immune system from recognizing “self”, and prevents tumor immunity. Low doses of the chemotherapy drug cyclophosphamide (CY) can reduce Tregs in breast cancer patients, sparing the good T cells needed to fight cancer. HER-2-specific antibodies can supercharge our cell-based vaccine by forming a bridge between HER-2 on the vaccine cells and host dendritic cells. Antibody-supercharged dendritic cells generate more killer/memory T cells of higher quality than dendritic cells alone. Our ongoing analysis of T cells from patients treated with CY, Herceptin and vaccine suggests that the T cells are of higher quality. We continue to test this strategy in patients with HER-2^lo metastatic breast cancer, where Herceptin does not fight breast cancer directly. We have enrolled about 65% of the planned 60 patients. Our integrated clinical studies will identify the most active combination vaccine regimen to test for preventing relapse patients with early breast cancer, regardless of HER-2 expression level.