ADAR1 promotes cisplatin resistance in intrahepatic cholangiocarcinoma by regulating BRCA2 expression through A-to-I editing manner.

Aberrant A-to-I RNA editing, mediated by ADAR1 has been found to be associated with increased tumourigenesis and the development of chemotherapy resistance in various types of cancer. Intrahepatic cholangiocarcinoma (iCCA) is a highly aggressive malignancy with a poor prognosis, and overcoming chemotherapy resistance poses a significant clinical challenge. This study aimed to clarify the roles of ADAR1 in tumour resistance to cisplatin in iCCA. We discovered that ADAR1 expression is elevated in iCCA patients, particularly in those resistant to cisplatin, and associated with poor clinical outcomes. Downregulation of ADAR1 can increase the sensitivity of iCCA cells to cisplatin treatment, whereas its overexpression has the inverse effect. By integrating RNA sequencing and Sanger sequencing, we identified BRCA2, a critical DNA damage repair gene, as a downstream target of ADAR1 in iCCA. ADAR1 mediates the A-to-I editing in BRCA2 3'UTR, inhibiting miR-3157-5p binding, consequently increasing BRCA2 mRNA and protein levels. Furthermore, ADAR1 enhances cellular DNA damage repair ability and facilitates cisplatin resistance in iCCA cells. Combining ADAR1 targeting with cisplatin treatment markedly enhances the anticancer efficacy of cisplatin. In conclusion, ADAR1 promotes tumour progression and cisplatin resistance of iCCA. ADAR1 targeting could inform the development of innovative combination therapies for iCCA.

CSNK2A1 confers gemcitabine resistance to pancreatic ductal adenocarcinoma via inducing autophagy.

Gemcitabine, a pivotal chemotherapeutic agent for pancreatic ductal adenocarcinoma (PDAC), frequently encounters drug resistance, posing a significant clinical challenge with implications for PDAC patient prognosis. In this study, employing an integrated approach involving bioinformatic analyses from multiple databases, we unveil CSNK2A1 as a key regulatory factor. The patient-derived xenograft (PDX) model further substantiates the critical role of CSNK2A1 in gemcitabine resistance within the context of PDAC. Additionally, targeted silencing of CSNK2A1 expression significantly enhances sensitivity of PDAC cells to gemcitabine treatment. Mechanistically, CSNK2A1's transcriptional regulation is mediated by H3K27 acetylation in PDAC. Moreover, we identify CSNK2A1 as a pivotal activator of autophagy, and enhanced autophagy drives gemcitabine resistance. Silmitasertib, an established CSNK2A1 inhibitor, can effectively inhibit autophagy. Notably, the combinatorial treatment of Silmitasertib with gemcitabine demonstrates remarkable efficacy in treating PDAC. In summary, our study reveals CSNK2A1 as a potent predictive factor for gemcitabine resistance in PDAC. Moreover, targeted CSNK2A1 inhibition by Silmitasertib represents a promising therapeutic strategy to restore gemcitabine sensitivity in PDAC, offering hope for improved clinical outcomes.

Imatinib facilitates gemcitabine sensitivity by targeting epigenetically activated PDGFC signaling in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is a malignant tumor with poor prognosis. Gemcitabine-based chemotherapy has become one of the main modalities of its management. However, gemcitabine resistance frequently occurs, leading to failure of PDAC therapy. Platelet-derived growth factors (PDGFs) and their receptors play important roles in cancer progression and chemoresistance. We aimed to investigate the biological function and therapeutic significance of platelet-derived growth factor C (PDGFC) in drug-resistant PDAC. Our study showed that PDGFC was abnormally highly expressed in gemcitabine-resistant PDAC. Silencing PDGFC expression can enhance the therapeutic effect of gemcitabine on PDAC. Mechanistically, the transcription of PDGFC is mediated by H3K27 acetylation, and PDGFC promotes gemcitabine resistance by activating the PDGFR-PI3K-AKT signaling pathway. The PDGFR inhibitor imatinib inhibits the PDGFR pathway. Imatinib and gemcitabine have a synergistic effect on the treatment of PDAC, and imatinib can significantly enhance the anti-tumor effect of gemcitabine in a drug-resistant PDAC patient-derived xenograft model. In conclusion, PDGFC is a potential predictor of gemcitabine-resistant PDAC. Imatinib inhibits PDGFR activation to promote gemcitabine sensitivity in PDAC. Combined modality regimen of imatinib and gemcitabine is likely to translate into clinical trial for the treatment of PDGFC-associated gemcitabine-resistant patients.

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 (m6 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 m6 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 m6 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.

METTL3 promotes intrahepatic cholangiocarcinoma progression by regulating IFIT2 expression in an m6A-YTHDF2-dependent manner.

N6-methyladenosine (m6A) RNA methylation has recently been found involving in regulatory mechanism of the tumor progression. Our aim was to explore the biological function and clinical significance of the m6A methyltransferase METTL3 in intrahepatic cholangiocarcinoma (ICC). In this study, we revealed that METTL3 was upregulated and predicted poor prognosis of patients with ICC. Multivariate regression analysis demonstrated that METTL3 expression was an independent predictor for overall survival in patients with ICC. Moreover, METTL3 knockdown inhibited ICC progression, while METTL3 overexpression showed the opposite effect. METTL3 inhibitor STM2457 also showed anti-tumor effect in ICC. Mechanistically, METTL3 transcription was driven by H3K4me3 activation. Upregulation of METTL3 mediated m6A modification of IFIT2 mRNA and accelerated IFIT2 mRNA decay in a YTHDF2-dependent manner, which promoted the development of ICC and lead to poorer prognosis. In summary, our findings revealed that H3K4me3 activation-driven METTL3 transcription promotes ICC progression by YTHDF2-mediated IFIT2 mRNA degradation, suggesting that METTL3 may serve as a potential target for human ICC therapy.