BMX, a specific HDAC8 inhibitor, with TMZ for advanced CRC therapy: a novel synergic effect to elicit p53-, β-catenin- and MGMT-dependent apoptotic cell death

Background: Despite advances in treatment, patients with refractory colorectal cancer (CRC) still have poor long-term survival, so there is a need for more effective therapeutic options. Methods: To evaluate the HDAC8 inhibition efficacy as a CRC treatment, we examined the effects of various HDAC8 inhibitors (HDAC8i), including BMX (NBM-T-L-BMX-OS01) in combination with temozolomide (TMZ) or other standard CRC drugs on p53 mutated HT29 cells, as well as wild-type p53 HCT116 and RKO cells. Results: We showed that HDAC8i with TMZ cotreatment resulted in HT29 arrest in the S and G2/M phase, whereas HCT116 and RKO arrest in the G0/G1 phase was accompanied by high sub-G1. Subsequently, this combination approach upregulated p53-mediated MGMT inhibition, leading to apoptosis. Furthermore, we observed the cotreatment also enabled triggering of cell senescence and decreased expression of stem cell biomarkers. Mechanistically, we found down-expression levels of β-catenin, cyclin D1 and c-Myc via GSK3β/β-catenin signaling. Intriguingly, autophagy also contributes to cell death under the opposite status of β-catenin/p62 axis, suggesting that there exists a negative feedback regulation between Wnt/β-catenin and autophagy. Consistently, the Gene Set Enrichment Analysis (GSEA) indicated both apoptotic and autophagy biomarkers in HT29 and RKO were upregulated after treating with BMX. Conclusions: BMX may act as a HDAC8 eraser and in combination with reframed-TMZ generates a remarkable synergic effect, providing a novel therapeutic target for various CRCs. [MediaObject not available: see fulltext.].