American Association for Cancer Research
10780432ccr121555-sup-rfig2.pdf (36.33 kB)

Supplementary Figure 2 from c-Src Activation Mediates Erlotinib Resistance in Head and Neck Cancer by Stimulating c-Met

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journal contribution
posted on 2023-03-31, 18:08 authored by Laura P. Stabile, Guoqing He, Vivian Wai Yan Lui, Sufi M. Thomas, Cassandra Henry, Christopher T. Gubish, Sonali Joyce, Kelly M. Quesnelle, Jill M. Siegfried, Jennifer R. Grandis

PDF file - 36K, After 48 hrs of incubation, the conditioned media was harvested from normal lung fibroblasts (NLFB, positive control), 201T lung tumor cells (negative control), VC-2, and DA-Src-5 cell lines. Each conditioned medium sample was concentrated from 4ml to 500μl. ELISA was performed with the Quantikine� Immunoassay Kit of human HGF. HGF concentration in the media was normalized to its respective protein concentration from total cell lysates. Each reaction was performed in triplicate.



Purpose: Strategies to inhibit the EGF receptor (EGFR) using the tyrosine kinase inhibitor erlotinib have been associated with limited clinical efficacy in head and neck squamous cell carcinoma (HNSCC). Co-activation of alternative kinases may contribute to erlotinib resistance.Experimental Design: We generated HNSCC cells expressing dominant-active c-Src (DA-Src) to determine the contribution of c-Src activation to erlotinib response.Results: Expression of DA-Src conferred resistance to erlotinib in vitro and in vivo compared with vector-transfected control cells. Phospho-Met was strongly upregulated by DA-Src, and DA-Src cells did not produce hepatocyte growth factor (HGF). Knockdown of c-Met enhanced sensitivity to erlotinib in DA-Src cells in vitro, as did combining a c-Met or c-Src inhibitor with erlotinib. Inhibiting EGFR resulted in minimal reduction of phospho-Met in DA-Src cells, whereas complete phospho-Met inhibition was achieved by inhibiting c-Src. A c-Met inhibitor significantly sensitized DA-Src tumors to erlotinib in vivo, resulting in reduced Ki67 labeling and increased apoptosis. In parental cells, knockdown of endogenous c-Src enhanced sensitivity to erlotinib, whereas treatment with HGF to directly induce phospho-Met resulted in erlotinib resistance. The level of endogenous phospho-c-Src in HNSCC cell lines was also significantly correlated with erlotinib resistance.Conclusions: Ligand-independent activation of c-Met contributes specifically to erlotinib resistance, not cetuximab resistance, in HNSCC with activated c-Src, where c-Met activation is more dependent on c-Src than on EGFR, providing an alternate survival pathway. Addition of a c-Met or c-Src inhibitor to erlotinib may increase efficacy of EGFR inhibition in patients with activated c-Src. Clin Cancer Res; 19(2); 380–92. ©2012 AACR.

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