Fig. 1
Low BCL-XL expression in melanoma biases the pro-survival pool towards MCL1. a–c RNA-sequencing mRNA expression data obtained from the Cancer Cell Line Encyclopaedia for MCL1 (a) BCL-XL (BCL2L1) (b) and MCL1:BCL-XL ratio (c) in colorectal cancer (CRC), melanoma, non-small cell lung cancer (NSCLC) and pancreatic tumour cells. Expression values are reads per kilobase million (RPKM) and are presented on a log2 scale. Black lines indicate median values. d, e Seven CRC (left) and seven melanoma (right) cell lines were cultured for 24 h before lysis and western blotting with the indicated antibodies. Quantification (e) of MCL1 and BCL-XL levels relative to A375 cells was performed by quantitative western blotting with fluorescently labelled secondary antibodies. f, g MCL1 (f) and BCL-XL (g) expression were quantified absolutely in CRC, melanoma, NSCLC and pancreatic tumour cell lines using recombinant protein standards and quantitative western blotting with fluorescently labelled secondary antibodies. Each point represents mean expression in a cell line from three independent experiments and is expressed in fmol per µg of total cellular protein (fmol µg−1). Black lines indicate median values. h Ratio of MCL1 to BCL-XL protein calculated from f and g, with black lines indicating median values. i Seven CRC (left) and seven melanoma (right) patient-derived xenograft (PDX) tumours were homogenised in lysis buffer and western blotted with the indicated antibodies. j, k Absolute quantification of MCL1 (j) and BCL-XL (k) expression in CRC and melanoma PDX tumour samples using recombinant protein standards and quantitative western blotting with fluorescently labelled secondary antibodies. Each point represents mean expression in a cell line from at least five technical replicates and is expressed in fmol per µg of total cellular protein (fmol µg−1). Black lines indicate median values. l Ratio of MCL1 to BCL-XL protein calculated from (j) and (k), with black lines indicating median values. Results (e–h, j–l) are the mean of three or more independent experiments, and error bars indicate SD. P ≤ 0.0001 (****), P ≤ 0.001 (***), P ≤ 0.01 (**), P ≤ 0.05 (*), ns (not significant) as determined by Kruskal–Wallis and Dunn’s multiple comparisons tests (a–c, f–h) or two-tailed Mann–Whitney test (j–l)
