ALKBH5-HOXA10 loop-mediated JAK2 m6A demethylation and cisplatin resistance in epithelial ovarian cancer

Abstract

Background Chemotherapy resistance remains a barrier to improving the prognosis of epithelial ovarian cancer (EOC). ALKBH5 has recently been shown to be one of the RNA N6-methyladenosine (m6A) demethyltransferases associated with various cancers, but its role in cancer therapeutic resistance remains unclear. This study aimed to investigate the role of AlkB homolog 5 (ALKBH5) in cisplatin-resistant EOC. Methods Functional assays were performed both in vitro and in vivo. RNA sequencing (RNA-seq), m6A-modified RNA immunoprecipitation sequencing (MeRIP-seq), chromatin immunoprecipitation, RNA immunoprecipitation, and luciferase reporter and actinomycin-D assays were performed to investigate RNA/RNA interaction and m6A modification of the ALKBH5-HOXA10 loop. Results ALKBH5 was upregulated in cisplatin-resistant EOC and promoted cancer cell cisplatin resistance both in vivo and in vitro. Notably, HOXA10 formed a loop with ALKBH5 and was found to be the upstream transcription factor of ALKBH5. HOXA10 overexpression also facilitated EOC cell chemoresistance both in vivo and in vitro. Collective results of MeRIP-seq and RNA-seq showed that JAK2 is the m6A-modified gene targeted by ALKBH5. The JAK2/STAT3 signaling pathway was activated by overexpression of the ALKBH5-HOXA10 loop, resulting in EOC chemoresistance. Cell sensitivity to cisplatin was rescued by ALKBH5 and HOXA10 knockdown or inhibition of the JAK2/STAT3 signaling pathway in EOC cells overexpressing ALKBH5-HOXA10. Conclusions The ALKBH5-HOXA10 loop jointly activates the JAK2/STAT3 signaling pathway by mediating JAK2 m6A demethylation, promoting EOC resistance to cisplatin. Thus, inhibition of the expression of the ALKBH5-HOXA10 loop may be a potential strategy to overcome cisplatin resistance in EOC.

Emerging role of m6A methylation modification in ovarian cancer

“…Similar to other tumours, the levels of RNA m6A modification are also dynamically modulated by these three regulator types in OC. Abnormal expression of m6A regulators predicts poor prognosis of OC patients and is involved in proliferation, invasion, metastasis and resistance via m6A-dependent and m6A-independent activity in OC [ 37 , 39 , 40 , 76 – 82 ]. Figure 1 shows the pathological roles and underlying mechanisms of m6A regulators in OC and will be discussed below.…”

“…In relation to human noncancer research, FTO possesses the ability to promote fat formation and obesity, and ALKBH5 participates in spermatogenesis, trophoblast invasion and ossification [ 93 , 94 ]. In OC, dysregulation of ALKBH5 and FTO takes part in proliferation, apoptosis, migration, drug resistance, cancer stem cell development and tumour autophagy, contributing to the relapse of OC patients [ 39 , 77 – 79 , 95 ] (Table 2 ). In other types of cancer, ALKBH5 and FTO also participate in many pathological and biological activities, referring to proliferation, apoptosis, migration, invasion and metastasis [ 93 , 94 ].…”

“…Drug resistance to platinum and PARPis inevitably emerges, remaining a clinical hurdle because of unraveled underlying mechanisms. Nie et al showed that ALKBH5 mRNA and protein expression upregulated in platinum-resistant EOC cells or samples, demonstrated by qRT–PCR, WB and IHC assays [ 39 ]. Moreover, CCK-8 and EdU assays indicated that ALKBH5 boosted proliferation and hindered apoptosis in A2780 and HO8910 cells (two EOC cell lines), which were confirmed in vivo through animal studies using xenograft mouse models [ 39 ].…”

“…Nie et al showed that ALKBH5 mRNA and protein expression upregulated in platinum-resistant EOC cells or samples, demonstrated by qRT–PCR, WB and IHC assays [ 39 ]. Moreover, CCK-8 and EdU assays indicated that ALKBH5 boosted proliferation and hindered apoptosis in A2780 and HO8910 cells (two EOC cell lines), which were confirmed in vivo through animal studies using xenograft mouse models [ 39 ]. Then, transcriptional analysis verified the presence of a homeobox A10 (HOXA10)-ALKBH5 loop involved in chemoresistance in EOC cells, which was confirmed by correlation analysis between ALKBH5 and HOXA10 expressions based on 483 EOCs in TCGA database [ 39 ].…”

“…alkB homologue 5, RNA demethylase (ALKBH5), an m6A demethylase, can orchestrate m6A levels in the 3′UTR of programmed cell death-1 ligand-1 ( PD-L1 ) mRNA, stabilize PD-L1 expression in intrahepatic cholangiocarcinoma (ICC), thus sensitize tumour cells to anti-PD1 immunotherapy [ 38 ]. There is also evidence for drug resistance modulation by ALKBH5 in OC [ 39 ]. Nie reported that upregulated ALKBH5 in OC decodes the m6A modification of Janus kinase 2 ( JAK2 ) and stabilizes JAK2 mRNA, subsequently contributing to cisplatin resistance, which is part of the standard adjuvant chemotherapy regimen [ 41 ].…”