Immunizing against breast cancer: a new swing for an old sword.

Therapeutic potential of vaccination has been explored in many clinical trials involving patients with breast cancer. A large variety of cancer immunogens have been tested. The majority of clinical vaccination studies have been carried out in patients with metastatic breast cancer, characterized by extremely aggressive malignant tumors, resistant to all standard cytotoxic treatments and with longest-lasting disease. With active specific immunotherapy, tumor-associated antigens coupled to appropriate adjuvant can elicit a powerful antitumor responses. The potential advantages of therapeutic cancer vaccines are that they can augment an established immunogenic response to the tumor (which is generally weak in breast cancer), they target specific tumor antigens (although there are few), they are potentially non-toxic, they can be combined with conventional therapies and/or other immunotherapies, and they elicit immunologic memory to prevent recurrence of the tumor. It is unclear whether therapeutic vaccines for cancer prolong survival. Data of clinical activity have been observed by using vaccines targeting HER-2/neu protein, human telomerase reverse transcriptase, carcinoembryonic antigen (CEA), and carbohydrate antigen given after stem cell rescue. A better understanding of the relation between innate and adaptive immune responses, and of the immune escape mechanisms employed by tumor cells, the discovery of mechanisms underlying immunological tolerance, and acknowledgment of the importance of both cell-mediated and humoral adaptive immunity for the control of tumour growth are necessary for leading to a more comprehensive immunotherapeutic approach in breast cancer.