Hypoxia-Driven Mechanism of Vemurafenib Resistance in Melanoma

Abstract

Melanoma is molecularly and structurally heterogeneous, with some tumor cells existing under hypoxic conditions. Our cell growth assays showed that under controlled hypoxic conditions, BRAF(V600E) melanoma cells rapidly became resistant to vemurafenib. By employing both a three-dimensional (3D) spheroid model and a two-dimensional (2D) hypoxic culture system to model hypoxia in vivo, we identified upregulation of HGF/MET signaling as a major mechanism associated with vemurafenib resistance as compared to 2D standard tissue culture in ambient air. We further confirmed that the upregulation of HGF/MET signaling was evident in drug-resistant melanoma patient tissues and mouse xenografts. Pharmacologic inhibition of the c-Met/Akt pathway restored the sensitivity of melanoma spheroids or 2D hypoxic cultures to vemurafenib.

3D tumor spheroids as in vitro models to mimic in vivo human solid tumors resistance to therapeutic drugs

“…upregulation. In addition, Qin et al (2016) also observed that melanoma spheroids composed of A375 cells presented a higher HIF-1α and VEGF expression than the same cells cultured in 2D and demonstrated that this metabolic variation can impact on cells sensitivity to vemurafenib.…”

“…highly expressed in hypoxic regions of the spheroids(Gong et al, 2015;Qin et al, 2016) Terashima et al (2016). In addition,Qin et al (2016) also observed that melanoma spheroids composed of A375 cells presented a higher HIF-1α and VEGF expression than the same cells cultured in 2D and demonstrated that this metabolic variation can impact on cells sensitivity to vemurafenib.In literature, it was also reported that HIF-1 regulates the expression of several antiapoptotic factors (e.g., Bak, Bax, Bcl-xL, Bcl-2, Bid, Mcl-1, NF-κB, p53, and survivin;Masoud & Li, 2015;Rohwer & Cramer, 2011). In addition,Qin et al (2016) also observed that melanoma spheroids composed of A375 cells presented a higher HIF-1α and VEGF expression than the same cells cultured in 2D and demonstrated that this metabolic variation can impact on cells sensitivity to vemurafenib.In literature, it was also reported that HIF-1 regulates the expression of several antiapoptotic factors (e.g., Bak, Bax, Bcl-xL, Bcl-2, Bid, Mcl-1, NF-κB, p53, and survivin;Masoud & Li, 2015;Rohwer & Cramer, 2011).…”

“…The vascular endothelial growth factor (VEGF) can also have a crucial role in the cells' drug resistance, and its expression can also be influenced by the HIF expression (Krock, Skuli, & Simon, 2011). In fact, the data available in the literature demonstrates that VEGF is highly expressed in hypoxic regions of the spheroids (Gong et al, 2015;Qin et al, 2016). Terashima et al (2016) noticed that the KYSE-70 esophageal cancer cells of spheroids, in comparison with those cells cultured in monolayers, present a twofold higher level of VEGF messenger RNA (mRNA), which was mediated by the HIF-1α…”

“…highly expressed in hypoxic regions of the spheroids(Gong et al, 2015;Qin et al, 2016) Terashima et al (2016). noticed that the KYSE-70 esophageal cancer cells of spheroids, in comparison with those cells cultured in monolayers, present a twofold higher level of VEGF messenger RNA (mRNA), which was mediated by the HIF-1αupregulation.…”

Bad company: Microenvironmentally mediated resistance to targeted therapy in melanoma

“…The expression of the ROR2 receptor induces a 10‐fold decrease in sensitivity to BRAF inhibition, with this population being induced via the upregulation of WNT5a, which stabilizes HIF‐1α levels during hypoxic conditions via increased SIAH2 expression (O'Connell et al, ). Recent studies using 3D melanoma spheroid models have also found that hypoxia‐driven upregulation of HGF/MET plays an important role in vemurafenib resistance and is prevalent in drug‐resistant melanoma patients and xenograft models (Qin et al, ). Together, the various studies strongly suggest that resistance to targeted therapy in melanoma can be driven by hypoxia.…”