PRMT5抑制后KRAS突变型结直肠癌中的自噬改变

Introduction: The KRAS mutation is found in 45% of Colorectal Cancer (CRC) patients. Evidence indicates upregulation of Protein Arginine Methyltransferase 5 (PRMT5) expression in 75% of KRAS-mutated CRC patient tumor samples and suggesting PRMT5 as a surrogate therapeutic target for KRAS Mutant CRC treatment. The exact mechanism of crosstalk between PRMT5 and mutant KRAS is poorly understood. This study evaluates the mechanism of autophagy induction under PRMT5 inhibition and the possible apoptotic transition. Methodology: Four CRC cell lines, HCT116, SW640 (KRAS mutant), HKE3, and LIM2405 (KRAS wild type), were treated with three inhibitors, EPZ015666 (EPZ), GSK3326595 (GSK), and AMG-193 (AMG), each at 0.5 µM, 1 µM, and 10 µM, and assessed at 24 h and 48 h. Western blot analysis was conducted for ATG5, BECLIN1, BRG1, LC3B, ULK1, and ACTIN (housekeeping) to quantify autophagy regulation. Fold-change values and p-values were used to determine significance, and comparisons were made across drug, dose, time point, and KRAS mutation status. Results: All three PRMT5 inhibitors elicited the autophagy pathway, with varying temporal and dose‐dependent effects. EPZ showed autophagy induction at most doses at 24 h, yet regulation fluctuated over further timepoints, suggesting induction without any clear shift toward either sustained flux or apoptosis. GSK demonstrated mild early induction at 24 h, which was followed by marked reductions. Notably, at 0.5 µM concentration, ULK1 (p=0.002) and BECLIN1 (p=0.023) were significantly downregulated at 48 h, suggesting that an initial trigger of the pathway is followed by autophagy collapse. AMG caused the highest activation with strong induction (Fold Change>2.5, p=0.045), observed at 48 h at concentrations of 1 and 10 µM; however, the absence of significant increases to LC3B suggests impaired flux and a transition toward apoptosis. EPZ and GSK both also demonstrated BECLIN1-independent initiation of autophagy across early doses and timepoints. Conclusion: Across four CRC lines, PRMT5 inhibition enhanced autophagy signaling, significantly in KRAS-mutant backgrounds. AMG consistently caused the strongest activation across early and late autophagy markers, indicating potent disruption of PRMT5-regulated stress-response circuits. We are currently investigating the onset of apoptosis under these treatment conditions by western blotting and gene expression by transcriptomics. This work aims to identify therapeutic targets within the autophagy-apoptosis axis to improve PRMT5 inhibitor-mediated cancer cell killing.