Endoglin as a predictive biomarker for pemetrexed sensitivity in non-small-cell lung cancer

Objective: Based on our previous research, which demonstrated that elevated plasma endoglin (ENG) levels in lung cancer patients were associated with a better prognosis, increased sensitivity to pemetrexed, and enhanced tumor suppression, this study aims to validate these findings at the cellular level. The focus is on membrane and extracellular ENG and their influence on drug response and tumor cell behavior in non-small cell lung cancer (NSCLC) cells. Methods: The correlation between ENG expression and pemetrexed-induced cytotoxicity in eight human non-squamous subtype NSCLC cell lines was analyzed. ENG in A549 and H1975 cells was knocked down using shRNA. MTT assay, cell cycle assay, western blot analysis, and boyden chamber assay were used to detect the effect of ENG on pemetrexed-induced cytotoxicity, cell cycle distribution, and cell migration. Results: The expression of membrane ENG was positively correlated with pemetrexed-induced cytotoxicity in human NSCLC cells. Compared to pemetrexed-sensitive A549 cells, the A549/a400 (pemetrexed-resistant subline) cells exhibited a reduced accumulation of cells in the S phase, making them less susceptible to cell death. ENG knockdown also alleviated pemetrexed-induced S phase arrest and regulated G1/S phase-related proteins (p53, p21, CDK2, and Cyclin A). Additionally, co-treatment with recombinant ENG enhanced pemetrexed-induced migration inhibition in the sensitive cel1 line and cytotoxicity in the resistance cell line. Conclusion: The present results strengthened our prior clinical findings, showing that higher membrane ENG expression enhances pemetrexed-induced cytotoxicity and S phase arrest, which may involve the ENG-p21 pathway. Additionally, microenvironmental ENG enhanced the anti-migration of pemetrexed. These findings highlight the potential of ENG as a biomarker and therapeutic target, opening new avenues to improve the outcomes of non-squamous cell NSCLC treatment.