In vivo toxicity of phenothiazines to cells of a transplantable tumor

Treatment of cancer with antipsychotic medications: Pushing the boundaries of schizophrenia and cancer

Over a century ago, the phenothiazine dye, methylene blue, was discovered to have both antipsychotic and anti-cancer effects. In the 20th-century, the first phenothiazine antipsychotic, chlorpromazine, was found to inhibit cancer. During the years of elucidating the pharmacology of the phenothiazines, reserpine, an antipsychotic with a long historical background, was likewise discovered to have anti-cancer properties. Research on the effects of antipsychotics on cancer continued slowly until the 21st century when efforts to repurpose antipsychotics for cancer treatment accelerated. This review examines the history of these developments, and identifies which antipsychotics might treat cancer, and which cancers might be treated by antipsychotics. The review also describes the molecular mechanisms through which antipsychotics may inhibit cancer. Although the overlap of molecular pathways between schizophrenia and cancer have been known or suspected for many years, no comprehensive review of the subject has appeared in the psychiatric literature to assess the significance of these similarities. This review fills that gap and discusses what, if any, significance the similarities have regarding the etiology of schizophrenia.

Systematic discovery of multicomponent therapeutics

Multicomponent therapies, originating through deliberate mixing of drugs in a clinical setting, through happenstance, and through rational design, have a successful history in a number of areas of medicine, including cancer, infectious diseases, and CNS disorders. We have developed a high-throughput screening method for identifying effective combinations of therapeutic compounds. We report here that systematic screening of combinations of small molecules reveals unexpected interactions between compounds, presumably due to interactions between the pathways on which they act. Through systematic screening of approximately 120,000 different two-component combinations of reference-listed drugs, we identified potential multicomponent therapeutics, including (i) fungistatic and analgesic agents that together generate fungicidal activity in drug-resistant Candida albicans, yet do not significantly affect human cells, (ii) glucocorticoid and antiplatelet agents that together suppress the production of tumor necrosis factor-alpha in human primary peripheral blood mononu-clear cells, and (iii) antipsychotic and antiprotozoal agents that do not exhibit significant antitumor activity alone, yet together prevent the growth of tumors in mice. Systematic combination screening may ultimately be useful for exploring the connectivity of biological pathways and, when performed with reference-listed drugs, may result in the discovery of new combination drug regimens.

Chemical radiosensitizers in cancer therapy

The development of effective low-LET radiation therapy for cancer has been hindered by the lack of consistent differential responses to radiation between tumor and normal tissues. One major difference between many solid tumors and the surrounding normal stroma is the presence of hypoxic foci in solid tumors due to the inadequate supply of nutritional needs as a result of the breakdown of microvasculature. Consequently, failure of conventional radiotherapy and local recurrences are in part attributed to the radioresistant hypoxic cell populations, present in the tumor. Local cure/control rates of a tumor can be increased only by an effective increase in the radiation dose. At the same time, an increase in such a dose would damage the oxic normal stroma, more than the hypoxic tumor cells. Hence, specific modification of tumor radiosensitivity by the use of chemical radiosensitizers, in combination with conventional radiotherapy, is an attractive alternative. Many clinicians and radiotherapists are skeptical about the outcome of using radiosensitizers in patients. Nevertheless, a vast amount of information is currently available regarding the first- and second-generation radiosensitizers both in murine and in human tumors. As a result, it is hoped that eventually a radiosensitizing drug would be discovered/synthesized that will overcome the drawbacks so far encountered in their use in the clinic. In this article, the development of chemical radiosensitizers since the early sixties, the basis for their selection, their mechanism(s) of action, and the results obtained with the various groups of radiosensitizers are reviewed.

Antitumor effects of ketoconazole and trifluoperazine in murine T-cell lymphomas

In vitro and in vivo antitumor effects of ketoconazole (KTZ), trifluoperazine (TFP), and combinations of both drugs were examined in cell lines established from radiation leukemia virus (RadLV)-induced T-cell lymphomas. KTZ inhibited [3H]-thymidine incorporation in the tumor cells in vitro; 50% inhibition of DNA synthesis was observed at concentrations of 4-7 micrograms/ml. [3H]-thymidine uptake in bone-marrow and spleen cells prepared from healthy mice was also inhibited by KTZ, but 50% inhibition was observed only at a concentration of 50 micrograms/ml. Stimulation of spleen cells with concanavalin A led to an increase in their sensitivity to the inhibition of DNA synthesis by KTZ. The tumor-cell lines varied in their sensitivity to the inhibition of DNA synthesis by TFP, and the effects of TFP on DNA synthesis in bone-marrow and spleen cells were similar to those observed in the tumor cells. Synergistic, additive, or less than additive effects of the drug combinations on the inhibition of DNA synthesis in vitro were observed both in tumor cells and in bone-marrow cells. In vivo experiments were conducted on groups of C57BL/6 (B6) mice that were inoculated s.c. with tumor cells and then treated with i.p. injections of KTZ, TFP or both. Control groups were injected with phosphate-buffered saline (PBS). Each of the drugs alone as well as their combinations caused a significant delay in the appearance of palpable tumors, a decrease in tumor size, and a marked prolongation of survival. The concentrations of the drugs used in in vivo experiments did not affect the WBC counts in the peripheral blood of healthy mice. KTZ is currently used for the treatment of prostatic cancer because of its inhibitory effect on testosterone biosynthesis. The results of the present study indicate the hormone-independent chemotherapeutic potential of KTZ, TFP, and combinations of the two drugs.