Long non-coding RNA AFAP1-AS1 promotes alternative splicing of AXIN2 by facilitating SRSFs phase separation to induce drug resistance in lung adenocarcinoma

Lung cancer currently holds the highest global incidence and mortality rates among malignant tumors, with lung adenocarcinoma being the most prevalent and deadly subtype. Chemotherapy and targeted therapy remain the standard treatments for lung adenocarcinoma, but tumor resistance continues to be a significant clinical challenge. In this study, we identified that the long non-coding RNA actin filament associated protein 1 antisense RNA 1 (AFAP1-AS1), which is highly expressed in lung adenocarcinoma, regulates RNA alternative splicing by recruiting splicing factors such as serine and arginine rich splicing factor 1 and 3 (SRSF1 and SRSF3), promoting their liquid-liquid phase separation. Among the affected splicing events, the exon 7 skipping of the key regulatory gene AXIN2, involved in the Wnt/β-catenin signaling pathway, is most notably regulated by AFAP1-AS1, resulting in the translation of a truncated AXIN2 isoform (AXIN2-S). This isoform facilitates the accumulation of β-catenin in the nucleus and the persistent activation of Wnt/β-catenin signaling pathway, ultimately contributing to drug resistance in lung adenocarcinoma. Our work uncovers a novel function of AFAP1-AS1 in regulating RNA alternative splicing through the modulation of splicing factors phase separation. This mechanism highlights an unrecognized pathway by which AFAP1-AS1 promotes drug resistance in lung adenocarcinoma, suggesting that AFAP1-AS1 and its regulated splicing events may serve as potential biomarkers or therapeutic targets for the treatment of lung adenocarcinoma.