Analyzing expression and phosphorylation of the EGF receptor in HNSCC

Abstract

Overexpression of the epidermal growth factor receptor (EGFR) in head and neck squamous cell carcinomas (HNSCC) is considered to cause increased EGFR activity, which adds to tumorigenicity and therapy resistance. Since it is still unclear, whether EGFR expression is indeed associated with increased activity in HNSCC, we analyzed the relationship between EGFR expression and auto-phosphorylation as a surrogate marker for activity. We used a tissue micro array, fresh frozen HNSCC tumor and corresponding normal tissue samples and a large panel of HNSCC cell lines. While we observed substantial overexpression only in approximately 20% of HNSCC, we also observed strong discrepancies between EGFR protein expression and auto-phosphorylation in HNSCC cell lines as well as in tumor specimens using Western blot and SH2-profiling; for the majority of HNSCC EGFR expression therefore seems not to be correlated with EGFR auto-phosphorylation. Blocking of EGFR activity by cetuximab and erlotinib points to increased EGFR activity in samples with increased basal auto-phosphorylation. However, we could also identify cells with low basal phosphorylation but relevant EGFR activity. In summary, our data demonstrate that EGFR expression and activity are not well correlated. Therefore EGFR positivity is no reliable surrogate marker for EGFR activity, arguing the need for alternative biomarkers or functional predictive tests.

Primary chemoradiation with cisplatin versus cetuximab for locally advanced head and neck cancer: a retrospective cohort study

“…Expression of the EGFR gene was also significantly lower in HPV-positive HNSCC, consistent with prior reports [19]. However, EGFR expression has not been shown to be predictive of clinical benefit for anti EGFR therapy in SCCHN, which may be related to the lack of correlation between EGFR expression and autophosphorylation activity [20,21].…”

Cetuximab-induced natural killer cell cytotoxicity in head and neck squamous cell carcinoma cell lines: investigation of the role of cetuximab sensitivity and HPV status

“…Other in vitro studies report varying results. While some studies do not observe a correlation, 37 others describe a correlation between EGFR expression and cetuximab-mediated ADCC. 32 , 38 Clinical reports show discordant results as well 39 , 40 and therefore EGFR expression is currently not a recognised predictive biomarker for cetuximab treatment in HNSCC.…”

Diagnostic and prognostic potential of the proteomic profiling of serum-derived extracellular vesicles in prostate cancer

“…To this end, we evaluated the expression of the epithelial-growth factor receptor (EGFR) and one of its phosphorylated forms (EGFR_pY1068) in A431, an epithelial squamous carcinoma cell line, and in human PCa-derived activated fibroblasts (CAFs). Indeed, EGFR is expressed at high levels by A431 (1–2 ×10 6 receptors per cell [ 38 , 39 ]) while being low to undetectable in fibroblasts [ 40 ]. EVs were isolated from culture media and mixed in scaling percentages for RPPA analysis.…”