The BET inhibitor JQ1 suppresses tumor survival by ABCB5-mediated autophagy in uveal melanoma

Abstract

Uveal melanoma (UM), the most common adult ocular tumor, is aggressive and resistant to treatment, posing threat to patients' lives. The novel, effective therapies and the exploration of chemosensitizer for UM are imperative. The anticancer efficacy was evaluated with and without JQ1 treatment or ABCB5 gene silencing or overexpression. RNA sequencing identified downstream effectors in JQ1-treated cells. Integrated analysis of The Cancer Genome Atlas data (TCGA) and immunohistochemistry (IHC) revealed the oncogenic role of ABCB5. Functional analyses of JQ1 and defective ABCB5 were conducted using flow cytometry, transmission electron microscopy (TEM), IHC and western blot. The effects of JQ1 were validated in a heterotopic tumor model derived from OCM-1 cells. JQ1 inhibited cell proliferation, migration and invasion, induced cell cycle arrest and promoted apoptosis. JQ1 also suppressed the survival of UM in heterotopic tumor model. RNA sequencing indicated that JQ1 down-regulated the expressions of ABCB5 and autophagy-related genes, which was confirmed in vitro and in vivo by western blot. ABCB5, a marker associated with cancer stem cells and chemo-resistance, exhibited heightened expression in UM tissues, linked to immune infiltration. Notably, disrupting ABCB5 expression impeded UM cell proliferation and interfered with autophagy. Moreover, the overexpression of ABCB5 promoted cell proliferation, migration and invasion, and rescued autophagy related gene expression. Of note, JQ1 enhanced the sensitivity of OCM-1 cells to chemotherapy. Thus JQ1 inhibits UM survival via ABCB5-mediated autophagy and enhances chemo-sensitivity, suggesting potential for BET-based approaches in UM clinical management.

Keywords: ABCB5; Autophagy; Chemoresistance; JQ1; Uveal melanoma.