KRAS mutants confer platinum resistance by regulating ALKBH5 posttranslational modifications in lung cancer
Fang Yu, Shikan Zheng, Chunjie Yu, Sanhui Gao, Zuqi Shen, Rukiye Nar, Zhexin Liu, Shuang Huang, Lizi Wu, Tongjun Gu, Zhijian Qian
Fang Yu, Shikan Zheng, Chunjie Yu, Sanhui Gao, Zuqi Shen, Rukiye Nar, Zhexin Liu, Shuang Huang, Lizi Wu, Tongjun Gu, Zhijian Qian
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Research Article Cell biology Oncology

KRAS mutants confer platinum resistance by regulating ALKBH5 posttranslational modifications in lung cancer

Abstract

Constitutively active mutations of KRAS are prevalent in non–small cell lung cancer (NSCLC). However, the relationship between these mutations and resistance to platinum-based chemotherapy and the underlying mechanisms remain elusive. In this study, we demonstrate that KRAS mutants confer resistance to platinum in NSCLC. Mechanistically, KRAS mutants mediate platinum resistance in NSCLC cells by activating ERK/JNK signaling, which inhibits AlkB homolog 5 (ALKBH5) N6-methyladenosine (m6A) demethylase activity by regulating posttranslational modifications (PTMs) of ALKBH5. Consequently, the KRAS mutant leads to a global increase in m6A methylation of mRNAs, particularly damage-specific DNA-binding protein 2 (DDB2) and XPC, which are essential for nucleotide excision repair. This methylation stabilized the mRNA of these 2 genes, thus enhancing NSCLC cells’ capability to repair platinum-induced DNA damage and avoid apoptosis, thereby contributing to drug resistance. Furthermore, blocking KRAS-mutant–induced m6A methylation, either by overexpressing a SUMOylation-deficient mutant of ALKBH5 or by inhibiting methyltransferase-like 3 (METTL3) pharmacologically, significantly sensitizes KRAS-mutant NSCLC cells to platinum drugs in vitro and in vivo. Collectively, our study uncovers a mechanism that mediates KRAS-mutant–induced chemoresistance in NSCLC cells by activating DNA repair through the modulation of the ERK/JNK/ALKBH5 PTM-induced m6A modification in DNA damage repair–related genes.

Authors

Fang Yu, Shikan Zheng, Chunjie Yu, Sanhui Gao, Zuqi Shen, Rukiye Nar, Zhexin Liu, Shuang Huang, Lizi Wu, Tongjun Gu, Zhijian Qian

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Figure 4

Global transcriptomic and epitranscriptomic analyses identified NER-related genes including DDB2 and XPC are key downstream target genes of the KRAS mutant.

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Global transcriptomic and epitranscriptomic analyses identified NER-rela...
(A) Volcano figure showing the differentially expressed genes induced by KRAS G12V overexpression in NCI-H522 cells. (B) GO analysis of the differentially expressed genes induced by KRAS G12V overexpression. (C) GSEA plot showing enrichment of gene sets of DNA damage repair and KRAS signaling in KRAS G12V–overexpressed NCI-H522 cells. (D) Heatmap showing the increased gene list of DNA damage repair–related genes induced by KRAS G12V overexpression shown in C. (E) Distribution of genes identified by m6A-seq with significant changes in both mRNA m6A methylation and overall expression induced by KRAS G12V overexpression. (F) Venn diagram shows the overlapped genes with both significant expression and m6A alterations upon KRAS G12V overexpression. (G) GO analysis of KRAS G12V downstream target genes in an m6A-dependent manner, identified by integrative analysis of RNA-Seq and m6A-Seq data in NCI-H522 cells. (H and I) RNA-Seq and m6A-Seq peak visualization of DDB2 and XPC transcripts in empty vector– and KRAS G12V–overexpressed NCI-H522 cells. (J and K) qRT-PCR analysis suggests that KRAS G12V overexpression–mediated upregulation of DDB2 and XPC could be rescued by METTL3 KD. (L and M) MeRIP analyses suggest that KRAS G12V overexpression–induced upregulation of m6A methylation levels of DDB2 and XPC transcripts is blocked by METTL3 depletion. In J–M, data are presented as mean ± SD, with ordinary 1-way ANOVA with Dunnett’s multiple-comparison test used. **P < 0.01; ***P < 0.001; ****P < 0.0001.