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HER3 Targeting Sensitizes HNSCC to Cetuximab by Reducing HER3 Activity and HER2/HER3 Dimerization: Evidence from Cell Line and Patient-Derived Xenograft Models.

ABSTRACT: Our previous work suggested that HER3 inhibition sensitizes head and neck squamous cell carcinoma (HNSCC) to EGFR inhibition with cetuximab. This study aimed to define the role of HER3 in cetuximab resistance and the antitumor mechanisms of EGFR/HER3 dual targeting in HNSCC.We treated cetuximab-resistant HNSCC UMSCC1-C and parental UMSCC1-P cell lines with anti-EGFR antibody cetuximab, anti-HER3 antibody MM-121, and their combination. We assessed activities of HER2, HER3, and downstream signaling pathways by Western blotting and cell growth by sulforhodamine B (SRB) and colony formation assays. HER3-specific shRNA was used to confirm the role of HER3 in cetuximab response. The combined efficacy and alterations in biomarkers were evaluated in UMSCC1-C xenograft and patient-derived xenograft (PDX) models.Cetuximab treatment induced HER3 activation and HER2/HER3 dimerization in HNSCC cell lines. Combined treatment with cetuximab and MM-121 blocked EGFR and HER3 activities and inhibited the PI3K/AKT and ERK signaling pathways and HNSCC cell growth more effectively than each antibody alone. HER3 knockdown reduced HER2 activation and resensitized cells to cetuximab. Cetuximab-resistant xenografts and PDX models revealed greater efficacy of dual EGFR and HER3 inhibition compared with single antibodies. In PDX tissue samples, cetuximab induced HER3 expression and MM-121 reduced AKT activity.Clinically relevant PDX models demonstrate that dual targeting of EGFR and HER3 is superior to EGFR targeting alone in HNSCC. Our study illustrates the upregulation of HER3 by cetuximab as one mechanism underlying resistance to EGFR inhibition in HNSCC, supporting further clinical investigations using multiple targeting strategies in patients who have failed cetuximab-based therapy. Clin Cancer Res; 23(3); 677-86. ©2016 AACR.

SUBMITTER: Wang D

PROVIDER: S-EPMC5199640 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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HER3 Targeting Sensitizes HNSCC to Cetuximab by Reducing HER3 Activity and HER2/HER3 Dimerization: Evidence from Cell Line and Patient-Derived Xenograft Models.

Wang Dongsheng D Qian Guoqing G Zhang Hongzheng H Magliocca Kelly R KR Nannapaneni Sreenivas S Amin A R M Ruhul AR Rossi Michael M Patel Mihir M El-Deiry Mark M Wadsworth J Trad JT Chen Zhengjia Z Khuri Fadlo R FR Shin Dong M DM Saba Nabil F NF Chen Zhuo G ZG

Clinical cancer research : an official journal of the American Association for Cancer Research 20160629 3

<h4>Purpose</h4>Our previous work suggested that HER3 inhibition sensitizes head and neck squamous cell carcinoma (HNSCC) to EGFR inhibition with cetuximab. This study aimed to define the role of HER3 in cetuximab resistance and the antitumor mechanisms of EGFR/HER3 dual targeting in HNSCC.<h4>Experimental design</h4>We treated cetuximab-resistant HNSCC UMSCC1-C and parental UMSCC1-P cell lines with anti-EGFR antibody cetuximab, anti-HER3 antibody MM-121, and their combination. We assessed activ ...[more]

PMID: 27358485

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Project description:IntroductionThe human epidermal growth factor receptor 2 (HER2) receptor tyrosine kinase (RTK) oncogene is an attractive therapeutic target for the treatment of HER2-addicted tumors. Although lapatinib, an FDA-approved small-molecule HER2 and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), represents a significant therapeutic advancement in the treatment of HER2+ breast cancers, responses to lapatinib have not been durable. Consequently, elucidation of mechanisms of acquired therapeutic resistance to HER-directed therapies is of critical importance.MethodsUsing a functional protein-pathway activation mapping strategy, along with targeted genomic knockdowns applied to a series of isogenic-matched pairs of lapatinib-sensitive and resistant cell lines, we now report an unexpected mechanism of acquired resistance to lapatinib and similar TKIs.ResultsThe signaling analysis revealed that whereas HER2 was appropriately inhibited in lapatinib-resistant cells, EGFR tyrosine phosphorylation was incompletely inhibited. Using a targeted molecular knockdown approach to interrogate the causal molecular underpinnings of EGFR-persistent activation, we found that lapatinib-resistant cells were no longer oncogene addicted to HER2-HER3-PI3K signaling, as seen in the parental lapatinib-sensitive cell lines, but instead were dependent on a heregulin (HRG)-driven HER3-EGFR-PI3K-PDK1 signaling axis. Two FDA-approved EGFR TKIs could not overcome HRG-HER3-mediated activation of EGFR, or reverse lapatinib resistance. The ability to overcome EGFR-mediated acquired therapeutic resistance to lapatinib was demonstrated through molecular knockdown of EGFR and treatment with the irreversible pan-HER TKI neratinib, which blocked HRG-dependent phosphorylation of HER3 and EGFR, resulting in apoptosis of resistant cells. In addition, whereas HRG reversed lapatinib-mediated antitumor effects in parental HER2+ breast cancer cells, neratinib was comparatively resistant to the effects of HRG in parental cells. Finally, we showed that HRG expression is an independent negative predictor of clinical outcome in HER2+ breast cancers, providing potential clinical relevance to our findings.ConclusionsMolecular analysis of acquired therapeutic resistance to lapatinib identified a new resistance mechanism based on incomplete and "leaky" inhibition of EGFR by lapatinib. The selective pressure applied by incomplete inhibition of the EGFR drug target resulted in selection of ligand-driven feedback that sustained EGFR activation in the face of constant exposure to the drug. Inadequate target inhibition driven by a ligand-mediated autocrine feedback loop may represent a broader mechanism of therapeutic resistance to HER TKIs and suggests adopting a different strategy for selecting more effective TKIs to advance into the clinic.

Dataset Information

HER3 Targeting Sensitizes HNSCC to Cetuximab by Reducing HER3 Activity and HER2/HER3 Dimerization: Evidence from Cell Line and Patient-Derived Xenograft Models.

Publications

HER3 Targeting Sensitizes HNSCC to Cetuximab by Reducing HER3 Activity and HER2/HER3 Dimerization: Evidence from Cell Line and Patient-Derived Xenograft Models.

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