Figure 1: Overexpressed MITF protects cells against ERK inhibition.
From: Low MITF/AXL ratio predicts early resistance to multiple targeted drugs in melanoma
(a) An insertional mutagenesis screen was performed using the VBIM system. A BRAF mutant melanoma cell line of low passage (04.07) was infected with three VBIM vectors (SD1–3; to cover the three reading frames) and treated with 1 μM of the ERK inhibitor SCH772984. Drug-resistant clones were established and analysed for FLAG-tagged proteins resulting from the integration of the viral cassettes. (b) Integration of the VBIM cassettes resulted in MITF overexpression in six independent ERKi-resistant clones, as shown by qRT–PCR, compared with parental 04.07 cells. Note that only clones derived from separate plates were considered as independent clones. Error bars denote s.d. for technical replicates. (c) Lentiviral overexpression of MITF resulted in increased resistance to long-term ERK inhibition in three independent BRAF mutant melanoma cell lines as shown by crystal violet staining. (d) Immunoblot of 04.07 cells confirmed MITF overexpression and inactivation of ERK after inhibitor treatment. HSP90 served as a loading control.
