Combination of antibodies directed against different ErbB3 surface epitopes prevents the establishment of resistance to BRAF/MEK inhibitors in melanoma

Abstract

Patients with metastatic melanoma bearing V600 mutations in BRAF oncogene clinically benefit from the treatment with BRAF inhibitors alone or in combination with MEK inhibitors. However, a limitation to such treatment is the occurrence of resistance. Tackling the adaptive changes helping cells survive from drug treatment may offer new therapeutic opportunities. Very recently the ErbB3 receptor has been shown to act as a central node promoting survival of BRAF mutated melanoma. In this paper we first demonstrate that ErbB3/AKT hyperphosphorylation occurs in BRAF mutated melanoma cell lines following exposure to BRAF and/or MEK inhibitors. This strongly correlates with increased transcriptional activation of its ligand neuregulin. Anti-ErbB3 antibodies impair the establishment of de novo cell resistance to BRAF inhibition in vitro. In order to more potently ablate ErbB3 activity we used a combination of two anti-ErbB3 antibodies directed against distinct epitopes of its extracellular domain. These two antibodies in combo with BRAF/MEK inhibitors potently inhibit in vitro cell growth and tumor regrowth after drug withdrawal in an in vivo xenograft model. Importantly, residual tumor masses from mice treated by the antibodies and BRAF/ERK inhibitors combo are characterized almost exclusively by large necrotic areas with limited residual areas of tumor growth. Taken together, our findings support the concept that triple therapy directed against BRAF/MEK/ErbB3 may be able to provide durable control of BRAF mutated metastatic melanoma.

MITF depletion elevates expression levels of ERBB3 receptor and its cognate ligand NRG1-beta in melanoma

“…Our data is supported by previous studies showing that both ERBB3 expression and phosphorylation can be elevated after MAPK inhibitor treatment [15–20]. Hyper-activation of the PI3K/AKT pathway due to increased NRG1-beta/ERBB3 pathway signaling has previously been reported to be responsible for acquired drug resistance in BRAFV600 melanomas [15, 17]. However, also low MITF/AXL and MITF/EGFR ratios have been suggested to be involved in early resistance to vemurafenib in a subset of melanomas [12, 13].…”

miR-579-3p controls melanoma progression and resistance to target therapy

“…S1). Finally, we decided to measure miR-579-3p expression in three BRAF mutated melanoma cell lines resistant to vemurafenib recently derived in our laboratory (18). miR-579-3p expression was strongly down-regulated in resistant M14, A375 (both BRAF V600E), and WM266 (BRAF V600D) compared with wild-type cells (Fig.…”

“…We and others, for example, have demonstrated that the ErbB3 receptor is a key player in the development of resistance to therapies in melanoma (16,17). This receptor is involved in the activation of an early feedback survival loop upon melanoma cell exposure to BRAF and MEK inhibitors, and monoclonal antibodies directed against ErbB3 act synergistically in combination with BRAF and MEK inhibitors to impair the development of drug resistance (16,18). In this paper, to investigate the possible role of the epigenetic or posttranscriptional changes in the establishment of drug resistance, we demonstrate that miRNAs could be novel and important effectors.…”

Future perspectives in melanoma research

“…Hyperactivation of ERBB3 receptor through phosporylation has been observed as an early feedback survival loop both in vitro and in vivo in response to RAF/MEK inhibition. This activation can be abrogated by anti-ERBB3 antibodies preventing the establishment of resistance to BRAF/MEK inhibitors in melanomas [23]. The feedback survival loop is promoted by increased autocrine production of EGFR ligand neuregulin, whose increased level of gene expression has been observed after BRAFi treatment in several cell lines and its secretion occurs shortly after melanoma cell exposure to BRAFi [24].…”