We investigated the anti-tumour effects and the underlying molecular mechanisms of a new oral histone deacetylase inhibitor (HDACi), chidamide, in NK/T cell lymphoma (NKTCL), a rare and highly aggressive non-Hodgkin lymphoma with poor outcomes. SNT-8 and SNK-10 NKTCL cell lines were exposed to different concentrations of chidamide for the indicated time. The treated cells were analysed for cell proliferation, cell cycle progression, and cell apoptosis. Proteins in the AKT/mTOR and MAPK signalling pathways and the DNA damage response (DDR) cell cycle checkpoint pathway were measured by Western blotting. Chidamide inhibited cell proliferation in a dose- and time-dependent manner, arrested cell cycle progression at the G0/G1 phase, and induced apoptosis in the NKTCL cell lines. In addition, we found that chidamide suppressed the phosphorylation levels of proteins in the AKT/mTOR and MAPK signalling pathways and activated the DDR cell cycle checkpoint pathway, that is, the ATM-Chk2-p53-p21 pathway. Expression of EBV genes was also assessed by Real-Time PCR. Chidamide induced EBV lytic-phase gene expression in EBV-positive NKTCL. Our results provide evidence that chidamide shows antitumour effects by inhibiting the AKT/mTOR and MAPK signalling pathways and activating the ATM-Chk2-p53-p21 signalling pathway in vitro.
Keywords: Cell cycle checkpoint pathway; Chidamide; DNA damage response; NK/T cell lymphoma.