Biological response modifiers in cancer.

We have seen a surge in the use of immunotherapy for the treatment of cancer. Biological response modifiers can act passively by enhancing the immunologic response to tumor cells or actively by altering the differentiation/growth of tumor cells. Active immunotherapy with cytokines such as interferons (IFNs) and interleukins (IL-2) is a form of nonspecific active immune stimulation. The use of IL-2 has recently been approved by the United States Food and Drug Administration (FDA) for the treatment of renal cell carcinoma and metastatic colorectal cancer. Considerable success has been achieved with the use of immunotherapy, especially in the area of passive immunotherapy using monoclonal antibodies--in particular, radiolabeled monoclonal antibodies. In addition to the various monoclonal antibodies that have been used in clinical trials, other strategies such as the use of antiangiogenic agents and matrix metalloprotease inhibitors (MMPIs) have also met with some success. Recently, the FDA approved bevacizumab, an anti-vascular endothelial growth factor (VEGF) agent, for the treatment of metastatic melanoma. This review also sheds light on the various angiogenesis inhibitors in clinical trials, the increasing use of thalidomide in cancer, and the upcoming potential cancer vaccines designed to activate cell-mediated immune responses against tumor antigens.