Saponins as chemosensitizing substances that improve effectiveness and selectivity of anticancer drug-Minireview of in vitro studies.

Triterpene saponins (saponosides) are found in higher plants and display a wide range of biological and pharmacological activities. The antitumor effects of saponins have been proved by their cytotoxic, cytostatic, proapoptotic, and anti-invasive effects in many cellular models. Saponins hold great potential for being developed into chemopreventive and chemotherapeutic drugs. A promising way of reducing the adverse effects of chemotherapy without attenuating its efficiency is provided by the combined application of chemotherapeutic agents and saponosides in subtoxic concentrations. Until recently, saponosides were primarily used as adjuvants that enhance the effect of vaccines. In cancer therapy, saponins are applied in combination with immunotoxins because they increase the selectivity of given immunotoxins against cancer cells and therefore inure normal cells to the cytotoxic effects of immunotoxins. Significantly, certain saponins have been identified that drastically enhance the efficacy of many chemotherapeutic agents, including cisplatin, paclitaxel, doxorubicin, docetaxel, mitoxantrone, and cyclophosphamide. Moreover, saponins used in combination therapy enhance the sensitivity of chemoresistant tumor cells to clinically used chemotherapeutic agents. This review sheds light on the molecular mechanisms underlying cancer co-treatment with saponins and chemotherapy, with a particular focus on modulation of the cell signaling pathways associated with the promotion and progression of cancer cell proliferation, apoptosis, and metastasis.