Fig. 1

Downregulation of miR-146a is associated with resistance to BRAF/MEKi in melanoma cell lines and its manipulation affects drug response and TRAIL-induced apoptosis. a Venn diagram illustrating common miR associated with BRAF/MEKi resistance in GSE141314, GSE67635 and GSE68841 datasets. b miR-146a shows significant downregulation in melanoma resistant cells (R) compared with their sensitive counterparts (S). logFC: log₂ Fold Change. P-value obtained from differential expression analysis performed with limma package. c Inverse correlation between miR-146a expression levels and IC50 values of combined BRAF/MEKi in melanoma cell lines (Spearman analysis). d Forced expression of miR-146a (+m-miR-146a) increases the effects of BRAF/MEKi treatment in LM16R, LM69 and LM70 cell lines, as shown by reduced cell growth and increased cell cytotoxicity and apoptosis, evaluated by CCK8, LDH and caspase 8 and 3/7 activity. LM69 and LM70 short term melanoma cultures were generated from treatment resistant melanoma lesions surgically excised from two patients. Based on qRT-PCR results, upon transfection miR-146a levels were up to 70-fold higher (range 76–1223) than the levels detectable in cells transfected with control oligos. Data are plotted as fold increase compared to cells transfected with mimic negative control. _*: p < 0.05, _**: p < 0.01, _***: p < 0.0001 by Student’s unpaired t test. e Forced expression of miR-146a increased the effect of treatment with sTRAIL. f Positive correlation between the levels of miR-146a expression and of activated caspase 3/7 induced by sTRAIL treatment (Spearman analysis). RLU: Relative Light Unit. Results shown are representative of 2 experiments performed in triplicate (d, e)