HSP27 DOWNREGULATION THROUGH ATR/CHK1 PATHWAY INCREASES CISPLATIN SENSITIVITY IN HUMAN COLON CANCER CELLS

CAYADO-GUTIÉRREZ, N.; REDONDO, A.; CUELLO CARRIÓN, F. D.; LOSSINO, A. D.; FANELLI, M. A.; VARGAS ROIG, L. M.; NADIN, S. B.

Mendoza

Congreso; XL Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2022

Sociedad de Biología de Cuyo

Hsp27 is a molecular chaperone with a widely described anti-apoptotic role. Hsp27 is overexpressed in many types of cancer and has been related to cisplatin (cPt) resistance. The heat shock proteins have also been implicated in DNA repair pathways. Previously, we reported that Hsp27 interacts with DNA mismatch repair (MMR) proteins in colorectal cancer cells. cPt has been reported to induce DNA damage response (DDR) through activation of ATR/CHK1 pathway, whose function is to regulate cell cycle progression, to promote DNA repair and apoptosis. Accordingly, Hsp27 has become an attractive therapeutic target. This study aims to investigate Hsp27 and ATR/CHK1 pathway relationship in cPt-exposed human colon cancer cell lines: HCT116+ch2 (MMR deficient, MMR-) and HCT116+ch3 (MMR proficient, MMR+). Hsp27 was downregulated with OGX427 before cPt treatment and ATR was inhibited by VE-821 (VE). Cells were incubated with 10 μM cPt for 24 h and collected at time 0 (immediately after cPt treatment, T0), 3 (T3), 9 (T9) and 24 (T24) h posttreatments. DNA damage was evaluated by comet assay and the expression of Hsp27, pHsp27 (Ser78) pCHK1 (Ser345), γH2AX (Ser139) using western blot. Hsp27 nuclear colocalization with CHK1 was demonstrated in cPt-treated MMR-/+ cells. Combined therapy with cPt+OGX427 or cPt+VE reduced cell viability (CCK8), particularly after cPt+VE in MMR- cells (p<0.01). High pHsp27 levels were detected in MMR- cells at T3. Interestingly, cPt+VE augmented γH2AX expression in both cell lines (T0), but it decreased during recovery (p<0.01). Cleaved PARP1 and activated caspase-3 were upregulated by cPt+VE, particularly in MMR+ cells, showing elevated DNA damage (p<0.01). Conversely, DNA damage decreased (p<0.05) and senescence was induced (T9, p<0.001) specially in MMR- cells. Hsp27 modulation through VE combining with cPt could be a promising tool to improve cPt-chemosensitivity in MMR- tumors.