Figure 2: MITF loss occurs in acquired resistance in vitro and in vivo.
From: Low MITF/AXL ratio predicts early resistance to multiple targeted drugs in melanoma
(a) Treatment-naïve BRAF mutant melanoma cells were under constant treatment with PLX4720 until resistance was achieved. Crystal violet staining confirmed resistance to 3 μM PLX4720 in resistant cells in comparison with their sensitive counterparts. (b) Immunoblot of sensitive (S) and resistant (R) melanoma cells showed expression of MITF and MITF-regulated proteins. HSP90 served as a loading control. (c) MITF mRNA expression was measured by qRT–PCR in treatment-naïve and resistant melanoma cell lines normalized to RPL13 mRNA expression. Error bars denote s.d. for technical replicates. (d) Human melanoma biopsies (obtained from patients before vemurafenib treatment (pre) and after relapse had occurred (post)) were stained for MITF. Tumour 2 was from a patient with distinct relapsed tumour clones. Scale bars, 200 μm. (e) MITF-M mRNA was measured in human biopsies before vemurafenib treatment (pre) and after relapse had occurred (post) from two different patients. Values were normalized to GAPDH mRNA expression. P values, by paired Student’s t-test across triplicates, were only shown for samples for which MITF mRNA expression dropped. Error bars denote s.d. for technical triplicates.
