Elucidating the role of RBM10 in brain metastasis of EGFR19del lung adenocarcinoma.

e20501 Background: The EGFR mutation was detected in 66.3% of Asian patients with lung adenocarcinoma. Among these mutations, EGFR 19del exhibited the highest sensitivity and best response. However, it is worth noting that patients with EGFR 19del have a high cumulative incidence of brain metastases, which contributes significantly to treatment failure. Based on previous WES analysis of primary lung cancer cases and their corresponding brain metastases, RBM10 co-mutation was observed in four out of ten cases with EGFR 19del mutation, leading to decreased expression levels of RBM10. These findings suggest a potential role for RBM10 in modulating the development of brain metastases in patients with EGFR 19del lung cancer. Methods: To investigate the role of RBM10 in brain metastasis, we performed RNA-seq on the PC9 cell line to identify metabolic pathways and genes associated with RBM10 and brain metastasis. Additionally, the brain metastasis model was established by injecting PC9 cells into the left ventricle of nude mice, and the ability of PC9 cells to form brain metastases after knocking down RBM10 was confirmed through two rounds of in vivo screening using the PC9 cell line. Lipidomics analysis further validated that RBM10 affects key metabolite production. Clip-seq and RNA-seq were employed to analyze how RBM10 regulates sphingolipid metabolism. Finally, we identified key targets affecting blood-brain barrier function within the sphingolipid metabolism pathway and verified their ability to inhibit brain metastasis using both in vitro and in vivo models. Results: RNA-seq results demonstrated the regulatory role of RBM10 in the sphingolipid metabolism pathway, specifically in GALC regulation. In vitro and in vivo models revealed an enhanced brain metastasis ability of the PC9shRBM10 group. Lipidomics analysis revealed that the knockdown of RBM10 resulted in a reduction in ceramide and an elevation in SPH. Integrated RNA-seq and Clip-seq analyses demonstrated that the splicing regulation on GALC was attenuated upon RBM10 knockdown, leading to an increase in GALC expression. Furthermore, this perturbation enhanced the downstream sphingosine-1-phosphate signalling axis (SPH-SK1/2-S1P), consequently promoting increased S1P production and elevated blood-brain barrier permeability. Finally, fingolimod, an S1P inhibitor, was employed to validate its efficacy in inhibiting brain metastasis; moreover, a combination therapy comprising osimertinib and fingolimod exhibited superior capacity for suppressing brain metastasis. Conclusions: This study aims to elucidate the regulatory mechanism underlying the impact of RBM10 on sphingolipid metabolism in brain metastasis of EGFR 19del lung adenocarcinoma, to identify novel therapeutic targets for preventing brain metastasis in patients exhibiting EGFR 19del lung adenocarcinoma with low RBM10 expression.