Supplementary Methods Supplementary Table Captions and legends for Supplementary Figures S1 -S11; Supplementary Table S1: Differentially regulated genes in both cisplatin-resistant and -sensitive phenotypes after cisplatin treatment (fold change > 1.5, P < 0.05); Supplementary Table S2: Baseline characteristics of the head and neck squamous cell carcinoma (HNSCC)population, classified according to the p-ERK1/2 scoring.
ARTICLE ABSTRACTGenomic analyses of squamous cell carcinoma (SCC) have yet to yield significant strategies against pathway activation to improve treatment. Platinum-based chemotherapy remains the mainstay of treatment for SCC of different histotypes either as a single-agent or alongside other chemotherapeutic drugs or radiotherapy; however, resistance inevitably emerges, which limits the duration of treatment response. To elucidate mechanisms that mediate resistance to cisplatin, we compared drug-induced perturbations to gene and protein expression between cisplatin-sensitive and -resistant SCC cells, and identified MAPK–ERK pathway upregulation and activation in drug-resistant cells. ERK-induced resistance appeared to be activated by Son of Sevenless (SOS) upstream, and mediated through Bim degradation downstream. Clinically, elevated p-ERK expression was associated with shorter disease-free survival in patients with locally advanced head and neck SCC treated with concurrent chemoradiation. Inhibition of MEK/ERK, but not that of EGFR or RAF, augmented cisplatin sensitivity in vitro and demonstrated efficacy and tolerability in vivo. Collectively, these findings suggest that inhibition of the activated SOS–MAPK–ERK pathway may augment patient responses to cisplatin treatment. Mol Cancer Ther; 14(7); 1750–60. ©2015 AACR.