Positive Feedback Loop of Histone Lactylation‐Driven HNRNPC Promotes Autophagy to Confer Pancreatic Ductal Adenocarcinoma Gemcitabine Resistance

Abstract Gemcitabine resistance remains a primary determinant of poor survival outcomes in pancreatic ductal adenocarcinoma (PDAC) patients, underscoring the urgent need to elucidate its molecular mechanisms and develop effective countermeasures. Here, gemcitabine‐resistant pancreatic cancer cell lines and patient‐derived xenograft (PDX) models are established, followed by high‐throughput sequencing, which identified heterogeneous nuclear ribonucleoprotein C (HNRNPC) as a significantly upregulated factor in chemoresistant tumors. Silencing of HNRNPC expression substantially restores sensitivity to gemcitabine treatment in vitro and vivo. Mechanistically, multi‐omics analysis reveals that histone H3 lysine18 lactylation (H3K18la) drives HNRNPC overexpression. HNRNPC stabilizes TNF receptor‐associated factor 6 (TRAF6) transcripts in an N6‐methyladenosine(m6A) ‐dependent manner, thereby activating autophagy to mediate gemcitabine resistance. Concurrently, HNRNPC orchestrates a metabolic reprogramming cascade by similarly stabilizing aldehyde dehydrogenase 1 family member A3 (ALDH1A3) mRNA, which enhances glycolysis and H3K18la levels, establishing a self‐reinforcing histone lactylation‐HNRNPC positive feedback loop. Notably, pharmacological inhibition of ALDH1A3 using 673A effectively disrupted this regulatory circuit and exerts a synergistic effect with gemcitabine in PDX. These findings not only delineate a histone lactylation‐driven positive feedback loop sustaining chemoresistance through HNRNPC‐mediated autophagy activation, but also develop the potential of 673A as a promising clinical candidate for overcoming gemcitabine resistance in PDAC treatment.