YTHDF2 promotes intrahepatic cholangiocarcinoma progression and desensitises cisplatin treatment by increasing CDKN1B mRNA degradation

BACKGROUND: Intrahepatic cholangiocarcinoma (ICC) is an aggressive cancer with exceedingly poor prognosis, and chemoresistance is a huge challenge for treatment. N6‐methyladenosine (m(6)A) modification plays an important role in the progression and chemoresistance of cancers. We aimed to investigate the oncogenic function and therapeutic significance of the m(6)A binding protein, YTH domain family 2 (YTHDF2), in ICC progression and cisplatin‐based chemotherapy. METHODS: Several independent data sets were used to assess the expression of YTHDF2 in ICC, particularly in chemoresistant ICC. Knockdown and overexpression were used to evaluate the effects of YTHDF2 on tumourigenesis and cisplatin response in ICC. Multi‐omics sequencing was performed to identify target genes. RIP, dual luciferase reporter, RNA stability experiment and loss‐of‐function assays were conducted to study the mechanisms underlying the oncogenic function of YTHDF2. Furthermore, patient‐derived xenograft (PDX) model was established to determine the effect of combination treatment of YTHDF2 siRNA and cisplatin in ICC. RESULTS: Our study showed that YTHDF2 was upregulated in ICC tissues, particularly in chemoresistant ICC tissues, and correlated with poor prognosis. Furthermore, silencing YTHDF2 led to inhibited proliferation, promoted apoptosis and G0/G1 cell cycle arrest. Its downregulation also enhanced DNA damage and sensitised ICC cells to cisplatin. YTHDF2 overexpression exerted the opposite results. Integration analysis using RNA‐seq, MeRIP‐seq and anti‐YTHDF2 RIP‐seq elucidated the role of YTHDF2 in tumourigenesis and cisplatin‐desensitising function by promoting the degradation of cyclin‐dependent kinase inhibitor 1B (CDKN1B) mRNA in an m(6)A‐dependent manner. Downregulation of CDKN1B increased the YTHDF2 silencing‐induced influence on tumourigenesis and cisplatin response to ICC. In addition, the combination treatment of YTHDF2 siRNA and cisplatin significantly enhanced the anti‐tumour effect of cisplatin in a chemoresistant ICC PDX model. CONCLUSIONS: YTHDF2 exhibits tumour oncogenic and cisplatin‐desensitising properties, which may offer insight into the development of novel combination therapeutic strategies for ICC.