Expression and activity of EGFR in human cutaneous melanoma cell lines and influence of vemurafenib on the EGFR pathway

Abstract

Data regarding the expression of epidermal growth factor receptor (EGFR) in melanoma and its role in the tumor biology are conflicting. In BRAF V600-mutant melanomas, the expression of EGFR has been associated with acquired resistance to BRAF inhibitors. In this study, we assessed EGFR expression and downstream signaling activity in a panel of melanoma cell lines and we investigated the effects of the BRAF inhibitor vemurafenib on expression of EGFR and its downstream effectors in a subgroup of BRAF-mutant melanoma cells. Three out of 10 melanoma cell lines expressed EGFR. Downstream signaling via ERK and AKT was responsive to either stimulation by EGF or inhibition by erlotinib. Constitutive activation of ERK occurred in all the cell lines investigated whereas constitutive activation of AKT only in three cell lines. Constitutive activation of ERK and AKT was independent from EGFR expression. Vemurafenib did not affect EGFR expression in general, but it increased EGFR phosphorylation in the cell line SkMel5. Induced EGFR phosphorylation was sensitive to treatment with erlotinib. Vemurafenib efficiently blocked ERK activation in all the BRAF-mutant cell lines tested, whereas its effects on AKT activation were dissimilar in the different cell lines. Our data suggest that EGFR is functional but usually inactive in EGFR high-expressing cell lines. Basal EGFR expression unlikely represents a biomarker for predicting the sensitivity to vemurafenib in melanoma, but EGFR activation might represent a mechanism of vemurafenib resistance in a subset of melanoma cells.

MITF Modulates Therapeutic Resistance through EGFR Signaling

“…Our data is also consonant with a recent report that high EGFR expressing cells often lack EGFR activation, presumably due to lack of ligands, and are still sensitive to BRAFi; thus, EGFR levels alone cannot be used as a biomarker of vemurafenib resistance(Gross et al ., 2014). Our results also suggest that ligand measurement in blood or other body fluid might be an eventual method to predict drug resistance clinically.…”

Treatment of Vemurafenib-Resistant SKMEL-28 Melanoma Cells with Paclitaxel

“…We also showed that SKMEL-28 R cells resisted to vemurafenib via overexpression of EGFR, pTyrosine1173-EGFR, pThr308-AKT and pSer473-AKT. These results are in accordance with previous reports (Chen et al, 2012;Gross et al, 2014). Vemurafenib-induced pAKTs were inhibited by MK-2206, an AKT inhibitor or by paclitaxel or by combined MK-2206 and paclitaxel (Figure 5a).…”

“…Normally EGFR expression level in SKMEL-28 is quite low however it is overexpressed in acquired resistance to vemurafenib cells (Prahallad et al, 201;Gross et al, 2014). Therefore we decided to investigate the role of EGFR and phosphorylated EGFR (pEGFR) in regulating of pAKT.…”

Potential therapeutic targets of epithelial–mesenchymal transition in melanoma

“…Increased ERK phosphorylation in wild-type BRAF melanoma cell lines has been observed, reducing cell adherence and increasing migration after vemurafenib treatment [107]. In SK-MEL-24 and MEL-HO cell lines, AKT phosphorylation increased after treatment with vemurafenib, while AKT activation decreased in SK-MEL-28, Colo800, and IPC298 BRAF wild-type cells [108]. One challenge associated with BRAF-targeted treatment is the tendency for melanoma to develop resistance to treatment.…”