The integrin-linked kinase-associated phosphatase (ILKAP) is a regulatory hub of ovarian cancer cell susceptibility to platinum drugs

Abstract

BackgroundPlatinum drugs are the most powerful chemotherapeutic agents in the treatment of ovarian cancer. We demonstrated previously that unexpectedly ovarian cancer cells are sensitised to cisplatin (CDDP) by the hepatocyte growth factor (HGF), usually considered an anti-apoptotic factor. MethodsWe used quantitative polymerase chain reaction and Western blot analysis to evaluate gene and protein expression, immunofluorescence to evaluate protein localisation and functional assays to measure cell viability and apoptosis. ResultsIn ovarian cancer cells, CDDP induced the phosphorylation, i.e. the activation, of the p90RSK. Surprisingly, a 48-h-long cell pre-treatment with HGF reverted this activation. HGF pre-treatment also resulted in the increased expression of the integrin-linked kinase (ILK)-associated phosphatase (ILKAP) that dephosphorylated the p90RSK. Conversely, CDDP down-modulated ILKAP expression. This impaired CDDP efficacy, as ILKAP silencing protected cells from CDDP-induced death. In line, the biochemical inhibition of the p90RSK or the combined silencing of the most expressed RSK isoforms, namely RSK1 and RSK2, increased the efficacy of CDDP. However, p90RSK inhibition was not sufficient to revert cell protection from death after ILKAP suppression, because of the simultaneous increased activity of the anti-apoptotic kinases ILK and ILK substrate AKT, which were both dephosphorylated, i.e. negatively regulated, by ILKAP. Only the combined inhibition of p90RSK and ILK reverted the effect of ILKAP suppression. ConclusionsAs RSKs, ILK and AKT are vital kinases for ovarian cancer onset and progression, data suggest that ILKAP is a regulatory hub of ovarian cancer cell survival by controlling the activation of these kinases.