Signaling via ErbB2 and ErbB3 Associates with Resistance and Epidermal Growth Factor Receptor (EGFR) Amplification with Sensitivity to EGFR Inhibitor Gefitinib in Head and Neck Squamous Cell Carcinoma Cells

Abstract

Purpose: The epidermal growth factor receptor (EGFR) inhibitor gefitinib (Iressa) has shown antitumor activity in clinical trials against cancers, such as non^small cell lung cancer and head and neck squamous cell carcinoma (HNSCC). Research on non^small cell lung cancer has elucidated factors that may predict response to gefitinib. Less is known about molecular markers that may predict response to gefitinib in HNSCC patients. Experimental Design: We analyzed possible associations of responsiveness to gefitinib with molecular markers of the EGFR/ErbB receptor family signaling pathway using 10 established HNSCC lines in vitro. IC 50 of gefitinib sensitivity was determined using clonogenic survival assays. ErbB signaling was assessed byWestern and real-time reverse transcription-PCR analyses of EGFR, ErbB2, ErbB3, and ErbB4 expression levels as well as by phosphorylation analysis of pEGFR, pErbB2, pErbB3, pAkt, and pErk. EGFR sequences encoding kinase domain and EGFR gene copy numbers were determined by cDNA sequencing and real-time PCR, respectively. Finally, responsiveness to gefitinib was compared with responsiveness to the anti-EGFR antibody cetuximab (Erbitux). Results: Expression levels of pErbB2 (P = 0.02) and total ErbB3 protein (P = 0.02) associated with resistance to gefitinib. Combining gefitinib with pertuzumab (Omnitarg), an antibody targeting ErbB2 heterodimerization, provided additional growth-inhibitory effect over gefitinib alone on relatively gefitinib-resistant HNSCC cell lines. The same markers did not predict resistance to cetuximab. In contrast, a similar trend suggesting association between EGFR gene copy number and drug sensitivity was observed for both gefitinib (P = 0.0498) and cetuximab (P = 0.053). No activating EGFR mutations were identified. Conclusions: EGFR amplification may predict sensitivity to gefitinib in HNSCC. However, other EGFR/ErbB receptor family members than EGFR may contribute to resistance to gefitinib. ErbB2 and ErbB3 may have potential as predictive markers and as therapeutic targets for combination therapy in treatment of HNSCC with gefitinib.

The ERBB3 receptor in cancer and cancer gene therapy

“…353 Coexpression of ERBB3 with EGFR and ERBB2 348 or of ERBB2 and ERBB3 349 related to poor prognosis, and expression of ERBB3 was correlated with resistance to the EGFR inhibitor gefitinib. 354 Increases in ERBB3 along with EGFR and ERBB2 were also reported for papillary carcinoma of thyroid. 355,356 Involvement of ERBB3 in oral cancer was confirmed in a rat model, where Erbb3 protein was increased in carcinogen-induced oral carcinomas.…”

Studies on the inhibition of feline EGFR in squamous cell carcinoma: Enhancement of radiosensitivity and rescue of resistance to small molecule inhibitors

“…44 This supports the theory that overexpressing EGFR cell lines are more likely to respond to EGFR targeting therapy. 45 In these cell lines combination treatments are thought to act synergistically because the cell lines utilize EGFR pathways like the PI3K and MAPK pathways to counteract the effect of radiation. 19 When these pathways are blocked, the cells become more sensitive to radiation.…”

Mechanisms of acquired resistance to cetuximab: role of HER (ErbB) family members

“…These findings are consistent with several recent reports that suggest HER3 plays an important role in regulating tumor response to EGFR or HER2 targeting agents. Erjala et al (2006) demonstrated a correlation between HER3 expression and gefitinib resistance. Similarly, Fujimoto et al (2005) pointed to HER3 as a potentially important mediator of EGFR inhibition by gefitinib in NSCLC cells.…”