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

Abstract

Purpose Our previous work suggested that HER3 inhibition sensitizes HNSCC to EGFR inhibition with cetuximab. This study aimed to define the role of HER3 in cetuximab resistance and the anti-tumor mechanisms of EGFR/HER3 dual targeting in HNSCC. Experimental Design 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. Results 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 PI3K/AKT and ERK signaling pathways and HNSCC cell growth more effectively than each antibody alone. HER3 knockdown reduced HER2 activation and re-sensitized cells to cetuximab. Cetuximab-resistant xenografts and PDX models revealed greater efficacy of dual EGFR and HER3 inhibition compared to single antibodies. In PDX tissue samples, cetuximab induced HER3 expression and MM-121 reduced AKT activity. Conclusion 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.

MET activation confers resistance to cetuximab, and prevents HER2 and HER3 upregulation in head and neck cancer

“…[24][25][26][27][28][29] However, in cetuximab-treated SNU1076 cells, MET activation reduced the phosphorylation levels of both HER2 and HER3 (Fig. As expected, we observed an increase of phosphorylated HER2 and HER3, which are known to be elevated in response to cetuximab in different types of cancer, including in HNSCC.…”

“…[3][4][5][12][13][14] Cetuximab inhibits tumor cell growth by preventing ligand binding to the extracellular domain of EGFR, thereby preventing the dimerization and auto-phosphorylation of this receptor and the subsequent activation of the signaling pathways downstream of EGFR. [24][25][26] The activation of the HER2/HER3 feedback loop in response to anti-EGFR therapies has also been reported in other cancers such as lung, breast and colorectal cancers. [19][20][21][22] An additional common resistance mechanism to cetuximab is reactivation of signaling pathways due to upregulation and activation of alternative RTKs, which termed as a compensatory activation loop [reviewed in Ref.…”

“…[19][20][21][22] An additional common resistance mechanism to cetuximab is reactivation of signaling pathways due to upregulation and activation of alternative RTKs, which termed as a compensatory activation loop [reviewed in Ref. 30,31 Nonetheless, despite the intensive work showing HER2/HER3 activation of a compensatory feedback loop in response to EGFR inhibitors, [24][25][26][27][28][29] the molecular machinery that regulates their expression in this context has not yet been identified. One of the major compensatory feedback loops is the upregulation and activation of the tyrosine kinases, human epidermal growth factor receptors 2 and 3 (HER2 and HER3, respectively).…”

Inhibition of SLC1A5 sensitizes colorectal cancer to cetuximab

“…7 Publications have shown that the amplification or increased level of MET, ERBB2 or ERBB3 contributes to consecutive activation of the downstream signaling of EGFR, leading to tumor resistance to EGFR-targeted treatment, while targeting them resensitizes tumor to cetuximab. 7 Publications have shown that the amplification or increased level of MET, ERBB2 or ERBB3 contributes to consecutive activation of the downstream signaling of EGFR, leading to tumor resistance to EGFR-targeted treatment, while targeting them resensitizes tumor to cetuximab.…”

“…2,3 Combined application of cetuximab and conventional chemotherapy reduced the risk of progression of patients with mCRC. 7,8 Therefore, it is of clinical significance to investigate potential strategy to improve the CRC response to cetuximab. Moreover, not all mCRC patients with RAS-wild type (WT) respond to cetuximab treatment, and even some patients with initial response may acquire resistance later after the treatment.…”