MEK inhibitors, such as trametinib, have shown therapeutic potential in head and neck squamous cell carcinoma (HNSCC). However, the factors influencing cancer cell sensitivity and resistance to MEK inhibition remain poorly understood. In our study, we observed that MEK inhibition significantly reduced the expression of MYC, a transcription factor critical for the therapeutic response. MYC overexpression markedly enhanced the sensitivity of HNSCC cells to trametinib, as evidenced by delayed wound healing and reduced colony formation. Cell cycle analysis revealed that trametinib induced a G1 phase arrest, whereas MYC overexpression accelerated cell cycle progression, with a reduced induction of p27 and p21 and diminished decreases in E2F1 and phospho-Ser2/5 levels. Flow cytometry and protein analyses demonstrated that MYC overexpression amplified trametinib-induced apoptosis and DNA damage, as evidenced by elevated levels of pro-apoptotic markers (p53, cleaved PARP, and BIM) and γH2AX. In vivo xenograft models confirmed these findings, showing increased sensitivity to trametinib in MYC-overexpressing tumors. Moreover, MEK inhibition increased autophagy in HNSCC cells, a factor critical for therapeutic resistance. Inhibiting trametinib-induced autophagy further enhanced apoptotic cell death. These findings suggest that MYC expression and autophagy play crucial roles in HNSCC's response to MEK inhibition. Combining trametinib with autophagy inhibition may improve therapeutic outcomes in HNSCC.
Keywords: HNSCC; MEK inhibition; MYC; autophagy; trametinib.