Cytostatic and reverse-transforming therapies of cancer - a brief review and future prospects

Selenium, calcium channel blockers, and cancer risk--the Yin and Yang of apoptosis?

It is increasingly clear that apoptosis plays a crucial role in the promotional phase of cancer development. Initiated pre-neoplastic clones in rat liver experience a high rate of apoptosis, and this rate has an important impact on the survival and growth of these clones. Suppression of apoptosis appears to be a universal property of cancer promoters, suggesting conversely that agents which inhibit cancer induction during the promotional phase increase the rate of apoptosis in initiated cells. Modulation of apoptosis is a likely explanation for recent striking evidence that use of calcium channel blockers substantially increases, whereas supplemental selenium substantially decreases, human cancer incidence. Non-genotoxic measures which are likely to upregulate apoptosis in pre-neoplastic/neoplastic cells--and thus may be useful in prevention and/or therapy--include selenium, retinoids/carotenoids, green tea polyphenols, caloric restriction, downregulation of IGF-I activity, high-dose tamoxifen and other protein kinase C antagonists, withdrawal or blockade of trophic hormones, isoflavones, limonene, vitamin D and cholecalciferol analogs, dietary fiber/sodium butyrate, hyperthermia, benzaldehyde derivatives, and creatine.

Integration of allogeneic lymphocyte immunotherapy with short-course chemotherapy and hypoenergic hyperthermia: a "triple-threat" treatment for disseminated cancer

A strategy for treatment of disseminated cancer is proposed which unites short-course chemotherapy, local hyperthermia, and allogeneic lymphocyte immunotherapy, designed and timed so as to optimize their synergistic interactions. Short-course chemotherapy potentiates allogeneic lymphocyte immunotherapy, and in turn is potentiated by subsequent courses of local hyperthermia. Response to hyperthermia can be enhanced by measures which selectively inhibit tumor blood flow, impair tumor energy metabolism, and produce tumor acidification; these include induction of prolonged hyperglycemia, and administration of selectively activated "hypoenergic" agents which inhibit or uncouple tumor respiration. It is anticipated that these methods will enable a significant advance in the control of metastasized solid tumors.

Rationale for a novel immunotherapy of cancer with allogeneic lymphocyte infusion

A simple method of cancer immunotherapy has been developed which achieves marked objective response in 20-30% of patients with disseminated disease. Each course consists of a low dose of chemotherapy followed two days later by intravenous infusion of allogeneic lymphocytes. Courses are repeated on a monthly basis as needed. The function of the chemotherapy--too mild to significantly influence tumor growth directly--appears to be depletion of suppressor T cells, which sensitizes the patient to the immunostimulant action ("allogeneic effect") of the subsequently infused lymphocytes. The rationale for this method is discussed in the context of a review of past attempts at lymphocyte immunotherapy. We are now attempting to improve response rates by combatting anergy with nutritional immunopotentiators, and by preventing prostaglandin-mediated or -dependent immunosuppression with prostaglandin synthetase inhibition. By understanding and counteracting the various specific and general means by which a growing tumor induces host tolerance, it should prove possible to achieve immune-mediated tumor regression in a high proportion of patients. Best results may be seen when allogeneic lymphocyte therapy is initiated at an earlier stage of the disease, and is used in conjunction with surgery, radiotherapy, short-course intensive chemotherapy, or hyperthermia-based methods.