Abstract

Background N 6 -methyladenosine (m 6 A) is the most abundant post-transcriptional modification, and METTL16 has recently emerged as a pivotal m 6 A methyltransferase in cancer. Cholesterol metabolic reprogramming and aberrant MAPK signaling sustain the malignant initiation and progression of colorectal cancer (CRC). However, whether - and how - m 6 A regulation, particularly by METTL16, interfaces with cholesterol metabolism and downstream oncogenic signaling in CRC remains unknown. Methods Differential expression of METTL16 in CRC was identified through bioinformatic analyses and validated by qRT-PCR, immunoblotting, and immunohistochemistry (IHC). The functional role of METTL16 in CRC progression was examined using in vitro assays and xenograft models. To identify downstream targets, RNA-seq and MeRIP-seq were performed, revealing MSMO1 as a METTL16-regulated gene. The mechanistic basis of the METTL16–MSMO1 axis was investigated through immunoprecipitation-Mass Spectrometry (IP-MS), co-immunoprecipitation (Co-IP), RNA immunoprecipitation (RIP), MeRIP-qPCR, and RNA stability assays. Cholesterol metabolism analyses were conducted to further characterize the metabolic consequences of METTL16–MSMO1 regulation. Results METTL16 was significantly upregulated in CRC and correlated with poor clinical outcomes. Mechanistically, METTL16 enhanced m 6 A modification of MSMO1, stabilizing its transcript via IGF2BP2 and disrupting intracellular cholesterol homeostasis, which triggered ER stress and activated MAPK-p38/ NF-κB signaling by promoting TAK1/TAB complex formation and TAK1 autophosphorylation, thereby driving CRC progression. Additionally, elevated cholesterol levels further reshaped global m 6 A methylation patterns and altered methyltransferase expression, suggesting a reciprocal feedback loop between cholesterol metabolism and epigenetic regulation. Conclusions These findings underscore the critical role of the METTL16–MSMO1 axis in driving cholesterol metabolic r