Hypoxia-induced autophagy increased resistance to Vemurafenib treatment on sensitive, but not resistant melanoma cells

CRISTIAN FALCON; CUELLO FEDERICO; CELIA NOEMÍ PEREZ; SERGIO ALVAREZ

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2019

SAIC

Melanoma is the most aggressive type of skin cancer. Although recent therapies have shown animpressive success, unfortunately patients develop resistance after a short period of disease control.Autophagy has been indicated as a mechanism of resistance in tumor cells. Autophagy is a processregulated by numerous factors, including hypoxia, a distinctive feature of the tumor microenvironment.Our hypothesis is that hypoxia or prolonged treatment with Vemurafenib (PLX, BRAF inhibitor)augment autophagy that in turn further increases PLX resistance. To this end, we cultured Lu1205human melanoma cells with or without CoCl2 during 24h to induce hypoxic condition that wasconfirmed by HIF-1α expression. Certainly, CoCl2 treatment increased LC3BII level, a marker ofautophagy, but it did not affect Lu1205 cell viability. To investigate the role of hypoxia in PLX resistance,Lu1205 cells were cultured in presence or absence of CoCl2 during 24h and then treated with PLX foranother 24h. As assessed by MTT assay, cells that were pre-treated with CoCl2 were more resistant to Vf(5-10μM). Interestingly, the inhibition of autophagy with NH4Cl diminished this resistance. Hypoxia didmodify the ability of PLX to reduce pERK1/2 and decreased the pAKT levels induced by this BRAFinhibitor. Moreover, Lu1205 cells with acquired resistance to Vf generated in our lab showed increasedsurvival and higher levels of LC3BII and pERK1/2 than sensitive cells when were treated with PLX. Onthe other hand, Hx or PLX-induced resistant cells transferred this resistant condition through solublemediators released to culture media. Altogether, these results suggest that hypoxia promotes a preresistantcell state with increased autophagy that enhances the develop of PLX resistance. Moreover, thismechanism is exacerbated in cells with acquired PLX resistance by long period treatment.