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Propolis and related polyphenolic compounds ; their relevance on host resistance and interaction with chemotherapy

Flavonoids are known to affect proliferation, differentiation and apoptosis in cancer cells and may play an important role in cancer chemoprevention.Chemoprevention includes: inhibition, delay or reverse the process of carcinogenesis and/or inhibition of proliferation of already established tumor cell. Chemoprevention via nontoxic agents could be one aproch for decreasing the incidence of cancer and its growth. Many naturally occuring agents have shown chemopreventive potential in a variety of bioassay systems and animal models. In the present study, results clearly demonstrated that combination of chemotherapeutic agents with polyphenolic/flavonoid components found in propolis, vegetables, fruits, and plant-derived beverages, having no side effects in animals, could reduce the dose of chemotherapeutic agents and improve anticancer activities in different type of murine tumors such as mammary carcinoma, and Echrlich ascites tumor. Their chemopreventive activity in animal models and cell cultures are likely to be the result of their ability to inhibit DNA synthesis in tumor cells, their capability to induce apoptosis of tumor cells, and their property to activate macrophage to produce factors capable to regulate the function of B-, T- and NK-cells, respectively. These findings suggest that propolis preparation and related flavonoids may enhance anticancer efficacy of chemotherapeutics and reduce cytotoxicity to immunocompetent cells. Pretreatment with flavonoids, both in vitro and in vivo, sensitizes cancer cell to growth inhibition and apoptosis induced by chemotherapeutic agents. It is likely that flavonoids by inhibition of P-gp activity increase the accumulation of chemotherapeutic in P-gp expressing cancer cells render accumulation of chemotherapeutic in cancer cell which results in altered absorption/bioavailability of these drugs after coadministration of flavonoids with cytostatic drug. These findings suggest that polyphenolic/flavonoid components may serve as a potent adjunct to chemotherapy in the treatment of cancers. However, further in-depth studies including clinical trials are needed to fully evaluate the value of flavonoids in combination with chemotherapeutic agents for the treatment of human cancers.

Propolis, Flavonoids, Chemoterapeutics, Multidrug resistance, Tumor

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