Inhibition of hsp27 and hsp40 potentiates 5-fluorouracil and carboplatin mediated cell killing in hepatoma cells

Heat shock proteins (Hsps) modulate several cellular functions and are ubiquitously present in cell. Here, we investigated alterations in the expression of Hsps and explored functional consequences of the same. Moreover, effect of quercetin (Qctn), an inhibitor of Hsps, on chemotherapeutic drugs treatment in hepatoma cells Hep3B and HepG2 was investigated. We for the first time report that 5-fluorouracil (5-FU) and carboplatin specifically induce expression of Hsp40 in addition to Hsp27 in Hep3B and HepG2 cells. Induction of Hsps following exposure to sub lethal dose of drugs is a cellular challenge to survival. However, under lethal environmental conditions with reduced cell viability, cells fail to sustain the induction of survival proteins, Hsp27 and Hsp40. Though Qctn itself, to certain extent is cytotoxic to cells, it potentiates the pro-apoptotic action of 5- FU and carboplatin, by inhibiting expression of Hsps. The increased cell killing correlates with decreased levels of procaspase-3. Furthermore, siRNA mediated knockdown of Hsp27 and Hsp40 diminishes survival of drugs exposed cells. Altogether, our data provides clear evidence that Hsp27 and 40 promote cell survival and inhibition of their expression does not allow cells to adapt to drug exposure and survive. Collectively, our novel findings on compelling action of 5-FU or carboplatin following knockdown of Hsp40 and that of Hsp27 highlights their strategic implications towards an effective therapy against HCC.