Kawano Y, et al. - In view of the findings that activating mutations of the epidermal growth factor receptor gene (EGFR) are oncogenic drivers in non–small cell lung cancer (NSCLC), this work was performed to assess whether ligand-independent EGFR signaling conferred by EGFR mutation triggers ROS generation in NSCLC cells. Results suggested role of CD44 v in redox adaptation and thus it seemed a potential target for treatment in CD44 v^high EGFR-mutated NSCLC cells.

Methods

• For this work, HEK293T cells were transfected with an expression vector for mutant EGFR.
• Using flow cytometry, researchers evaluated the expression of CD44 variant (CD44 v) isoforms in NSCLC cell lines.
• By RNA interference, cells were depleted of CD44 v and assayed for ROS and glutathione (GSH) levels.
• Evaluation of the effect of CD44 v on cisplatin sensitivity was performed in vitro with the MTS assay.

Results

• In transfected HEK293T cells, EGFR signaling due to EGFR mutation increased ROS levels.
• There appeared an inverse correlation of the expression of CD44 v isoforms with basal ROS levels in EGFR mutation–positive NSCLC cell lines.
• In EGFR-mutated NSCLC cells, knockdown of CD44 v induced depletion of intracellular GSH and increased ROS levels that express CD44 v at a high level (CD44 v^high).
• In addition, depletion of GSH by treatment with buthionine-[S, R]-sulfoximine induced marked accumulation of ROS and enhanced the cytotoxicity of cisplatin in CD44 vhigh EGFR-mutated NSCLC cells but not in corresponding CD44 vlow cells.
• Treatment with the antioxidant N-acetyl-L-cysteine prevented this enhancement of cisplatin cytotoxicity by GSH depletion.
• Knockdown of CD44 v also increased cisplatin cytotoxicity in CD44 v^high EGFR mutation–positive NSCLC cells but not in CD44 v^low cells.