AHCYL1 mediates the tumor-promoting effect of PREX2 in non-small cell lung carcinoma

<b>Rationale:</b> As the most common form of lung cancer, non-small cell lung cancer (NSCLC) is still a challenging disease. Even though molecular-targeted drugs have greatly benefited NSCLC patients, the limited number of effective targets and the emergence of drug resistance necessitate further research to identify new candidates and improve clinical outcomes. Phosphatidylinositol-3,4,5-triphosphate-dependent RAC exchange factor-2 (PREX2) is highly expressed in multiple cancer types and poses high mutation frequency in lung cancer. However, the study of PREX2 in lung cancer, especially NSCLC, is few and unclear, thus, the role of PREX2 and the regulatory mechanism of PREX2 in NSCLC is worthy of further investigation. <b>Methods:</b> To determine the tumor-promoting effects of PREX2 in NSCLC, we established PREX2 knockdown NSCLC cells, then assessed cell growth in <i>vitro</i> and in cell-derived xenograft (CDX) mouse model. Furtherly, we used the urethane-induced lung carcinogenesis mouse model to confirm the significance of PREX2 <i>in vivo</i>. Additionally, we identified AHCYL1 as a novel PREX2-interacting protein through pull-down assay and liquid chromatography with tandem mass spectrometry (LC-MS/MS) and investigated the mechanisms of PREX2 GEF activity regulated by AHCYL1 using various molecular biology assays, including western blotting, <i>in vitro</i> GEF assay and active RAC1 pull-down assay. <b>Results:</b> Our study suggests that PREX2 and AHCYL1 both promote NSCLC cell growth and proves that AHCYL1 enhances the GEF activity of PREX2 by alleviating the mutual inhibition between PREX2 and PTEN. Consequently, AHCYL1 intensifies the tumor-promoting effects of PREX2 in NSCLC. <b>Conclusion:</b> Overall, our results indicate that PREX2 and AHCYL1 promote lung cancer development and reveal a novel regulatory mechanism of PREX2 GEF activity by AHCYL1, which will contribute to the understanding of NSCLC pathogenesis and offer new targets and strategies for the diagnosis and treatment of NSCLC.