Melanoma is an aggressive disease that accounts for approximately 75% of skin cancer-related deaths.,Historically, treatment options for patients with advanced stage melanoma have been limited by modest response rates and failure to improve overall survival.,The treatment landscape for advanced stage melanoma was revolutionized in 2011 with the approval of ipilimumab and vemurafenib, both of which improved overall survival in phase III clinical trials.,More recently, the targeted inhibitors dabrafenib and trametinib have demonstrated similar therapeutic profiles.,To (a) discuss emerging treatment options for advanced melanoma, specifically ilpilimumab, vemurafenib, dabrafenib, and trametinib, in the context of their mechanisms of action and their potential for long-term improvement in patient outcome, and (b) to consider the impact of these agents on the current treatment landscape.,A literature search was conducted to collect data from clinical trials involving ipilimumab, vemurafenib, dabrafenib, and trametinib.,Emphasis was placed on outcome measures related to long-term clinical benefit.,Ipilimumab, a fully human monoclonal antibody, exploits the natural ability of the immune system to eradicate primary cancer cells.,It inhibits the binding of cytotoxic T-lymphocyte antigen-4 to its ligands, thereby potentiating T-cell response and antitumor immunity.,In a phase III clinical trial, ipilimumab at 3 mg/kg improved overall survival in previously treated patients with metastatic melanoma.,Components of the mitogen-activated protein kinase (MAPK) pathway are particularly relevant in melanoma and have been targeted by small molecular inhibitors.,Vemurafenib and dabrafenib inhibit the BRAF V600 mutation, which prevents oncogenic activities such as uncheck proliferation and evasion of immune response.,Data from phase III clinical trials suggest that both vemurafenib and dabrafenib improve patient outcomes, with vemurafenib showing an overall survival benefit and dabrafenib showing improved median progression-free survival.,The targeted-therapy approach in melanoma continued to gain momentum with the development of trametinib, which inhibits the MEK protein, the only known substrate of the BRAF V600 protein.,Inhibition of MEK leads to decreased cell signaling and proliferation in cancer cells.,In phase III trials, trametinib demonstrated significant improvement in median progression-free survival and median overall survival compared with chemotherapy treatment, making this treatment a valuable addition to the current armamentarium.,The adverse events associated with these new treatments are generally tolerable and mild to moderate in severity; however, care should be taken when selecting a therapy, since the specific adverse events associated with these treatments are unique, and serious events have been reported.,The immunotherapy ipilimumab and the MAPK-targeted inhibitors vemurafenib, dabrafenib, and trametinib have forever changed the treatment landscape for melanoma.,Indeed, these new therapies have demonstrated long-term improvement in patient outcome, a benefit not afforded by traditional therapeutics.,Important research continues on the molecular basis of melanoma, and new targets are likely to emerge.,Other areas of work include optimization of sequencing and/or combination of current treatments, which may increase the number of patients who experience clinical benefit.
Treatment of advanced melanoma has been improved with the advent of the BRAF inhibitors.,However, a limitation to such treatment is the occurrence of resistance.,Several mechanisms have been identified to be responsible for the development of resistance, either MEK-dependent or MEK-independent.,In order to overcome resistance due to reactivation of MEK signaling, MEK inhibitors are being clinically developed with promising results.,However, also in this case resistance inevitably occurs.,It has been recently reported that ErbB3, a member of the EGFR receptor family, may be involved in the establishment of drug resistance.,Three melanoma cell lines were tested: LOX IMVI (BRAF V600E), MST-L (BRAF V600R) and WM266 (BRAF V600D).,Phosphorylation of Receptor Tyrosine Kinases (RTKs) was assessed by an RTK array.,Western blot analysis was performed on total protein extracts using anti-ErbB3, anti-AKT and anti-ERK 1/2 antibodies.,The expression of neuregulin after vemurafenib treatment was assessed by Real Time PCR and Western blotting.,The growth inhibitory effects of vemurafenib, GSK1120212b and/or anti-ErbB3 mAbs were evaluated by in vitro colony formation assays.,In the present study we demonstrate that ErbB3 is the main RTK undergoing rapidly hyperphosphorylation upon either treatment with a BRAF inhibitor or with a MEK inhibitor in a panel of melanoma cell lines harboring a variety of V600BRAF mutations and that this results in a strong activation of phospho-AKT.,Importantly, ErbB3 activation is fully abrogated by the simultaneous use of anti-ErbB3 monoclonal antibodies, which are also shown to potently synergize with BRAF inhibitors in the inactivation of both AKT and ERK pathways and in the inhibition of melanoma cell growth.,We show that upregulation of phospho-ErbB3 is due to an autocrine loop involving increased transcription and production of neuregulin by melanoma cells.,On the basis of these results, we propose that initial co-treatment with BRAF and/or MEK inhibitors and anti-ErbB3 antibodies should be pursued as a strategy to reduce the ErbB3-dependent feedback survival mechanism and enhance duration of clinical response.