Figure 9. CoREST complex inhibition promotes a response to BRAFi therapy in BRAFi-R melanoma through DUSP1 upregulation.

(A) Western blot analysis of 1205Lu-R and 451Lu-R melanoma cells treated with DMSO, 5 μM PLX4032 alone, 2.5 μM corin alone, or 2.5 μM corin plus 5 μM PLX4032 for 24 hours. Western blots were run contemporaneously with the exception of DUSP1. DUSP1 expression in 1205Lu-R and 451Lu-R cells was evaluated on separate Western blots, as denoted by the separating dotted line. Quantification of the relative expression of p-p38 (active) versus p38 (total) protein expression relative to the DMSO control is shown below each p-p38 band. (B and C) Quantification of DUSP1, -4, -5, and -6 mRNA expression levels (RT-qPCR) in BRAFi-S (S) versus BRAFi-R (R) 451Lu (B) and 1205Lu (C) melanoma cells (n = 3). *P < 0.05, **P < 0.01, ***P < 0.001 and ****P < 0.0001, by 2-tailed, unpaired t test. (D) DUSP1 expression levels (RT-qPCR) in 451Lu-R, 1205Lu-R, SkMel28-R, and A375-R melanoma cells treated with DMSO or 2.5 μM corin for 2, 4, 8, or 24 hours. *P < 0.05 and ***P < 0.001, by 1-way ANOVA with Tukey’s test. (E) Proliferation of 1205Lu-R melanoma cells overexpressing DUSP1 versus control (Ctrl) vector, treated with increasing doses of PLX4032 for 72 hours. *P < 0.05 and **P < 0.01, by 2-way ANOVA with Tukey’s test. The morphology of 1205Lu-R melanoma cells following vector control (top) or DUSP1 overexpression (bottom) is depicted on the right. Representative images shown. Scale bar: 100 μm. (F) Quantification of DUSP1 expression in normal skin (n = 7), benign nevi (n = 18), and malignant melanoma (n = 44) tissues from patients. Data were generated using microarray data from Talantov et al. (61). ***P < 0.001 and ****P < 0.0001, by 1-way ANOVA with Tukey’s test. (G) Kaplan-Meier curves illustrating the correlation of DUSP1/RCOR1 expression in patients’ tumor specimens (split at the median) and overall survival using data obtained from TCGA melanoma database (https://portal.gdc.cancer.gov).