CD44 inhibition attenuates EGFR signaling and enhances cisplatin sensitivity in human EGFR wild-type non-small-cell lung cancer cells

Cluster of differentiation 44 (CD44) as a transmembrane glycoprotein is found to be expressed in non-small cell lung cancer (NSCLC), is significantly associated with NSLC progression, metastasis and drug resistance. This study aimed to explore whether CD44 inhibition improves the sensitivity of epidermal growth factor receptor (EGFR) wild-type NSCLC cells to cisplatin and how it affects wild-type EGFR in NSCLC cells. Small interfering RNA was used to knockdown CD44 expression in EGFR wild-type NSCLC cell line H460. Results suggested that CD44 downregulation reduced cell growth, promoted G(0)/G(1) cell cycle arrest and induced cell apoptosis in H460 cells and these effects were evidently enhanced when in combination with cisplatin. Deactivation of EGFR signaling pathway including EGFR phosphorylation and its downstream molecules, targets ERK, AKT1 and SRC which were also observed in CD44-silenced H460 cells with or without EGF stimulation. Furthermore, the CD44 expression level was positively correlated with wild-type EGFR level in human lung adenocarcinoma tissues and CD44 inhibition significantly accelerated the degradation of EGFR, indicating that enhanced sensitivity of H460 cells to cisplatin by downregulation of CD44 might be due to EGFR degradation. This study demonstrated that suppression of CD44 deactivated EGFR signals in NSCLC cells with wild-type EGFR, thereby contributing to the inhibition of cell proliferation and the reinforcement of cisplatin sensitivity. It is suggested that downregulation of CD44 could be a novel potential therapeutic strategy for the treatment of EGFR wild-type NSCLC.