The influence of oracin on reduction and toxicity of doxorubicin in hepatocytes and mammary epithelial cells MCF-10A.

The ways, how to increase effectiveness of doxorubicin (DOX) in cancer cells and decrease its toxicity in normal cells, have been intensively studied. In breast cancer cells MCF-7, isoquinoline derivative oracin (ORC) inhibited DOX reduction and increased DOX antiproliferative effect. The aim of this study was to test the influence of ORC on the reduction of DOX and its toxicity in hepatocytes and non-tumourous breast cells. The kinetics of DOX reduction was measured in cytosols from rat liver, human liver and human mammary epithelial cells MCF-10A. Activity and expression of carbonyl reductase 1 (CBR1) were assayed using menadione as a substrate and western blot analysis. End-point tests of viability served for study of cytotoxicity of DOX, ORC and DOX+ORC combinations in rat hepatocytes and MCF-10A cells. The inhibitory effect of ORC on DOX reductases was almost none in MCF-10A cells and mild in liver. CBR1 expression and activity was lower in non-tumourous MCF-10A cells than in cancer MCF-7 cells. Cytotoxicity tests showed that DOX+ORC combinations had significantly lower toxicity than DOX alone in MCF-10A cells as well as in hepatocytes. ORC significantly decreases DOX toxicity in MCF-10A and in hepatocytes. Therefore, concomitant use of ORC and DOX may protect normal cells against DOX toxicity.

The effectiveness of oracin in enhancing the cytotoxicity of doxorubicin through the inhibition of doxorubicin deactivation in breast cancer MCF7 cells.

The maximal therapeutic doses of the cytostatic drug doxorubicin (DOX) are strictly limited by the development of systemic toxicity, especially cardiotoxicity. The inhibition of DOX-metabolizing enzymes within cancer cells is possible strategy to improve DOX efficacy. In breast cancer cells (MCF7), DOX is effectively deactivated by carbonyl reduction. The aim of the present study was to test whether isoquinoline derivative oracin (ORC) is able to inhibit DOX reductases and to enhance DOX cytotoxic efficacy. The kinetics studies of DOX reduction in MCF7 cytosolic fractions were evaluated using high-performance liquid chromatography. The cytotoxicity of DOX, ORC, and DOX+ORC combinations was assayed using cell-viability tests and caspases activities and monitored using xCELLigence System for real-time cell analysis. ORC significantly inhibited DOX reduction in MCF7 cytosol. Competitive inhibition was found. The viability was significantly lower in cells treated with ORC+DOX combinations in comparison to cells treated with DOX alone. Significant enhancement of DOX cytotoxicity was achieved already with 0.5 µM ORC. DOX together with ORC was able to kill about 55% cells more than DOX alone. ORC significantly increases DOX efficacy in MCF7 cells probably due to the inhibition of DOX reductases.