Fig. 7: MITF is activated in response to palbociclib and is elevated in tumors from palbociclib-resistant breast cancer patients.

a MCF-7 cells were collected after indicated treatments and then subjected to qPCR and immunoblotting to examine expression levels of genes as indicated (n = 3 independent experiments). b Expression of MITF in primary breast cancers from patients at stages of baseline (BL), 1 month after endocrine treatment (C1D1), 3 months after endocrine and palbociclib treatment (C1D15), and 12 weeks after endocrine and palbociclib treatment (Surgery) in the NeoPalAna trial (n represents the number of patient biopsies, noted in each graph). Box plots with centerline = median, box = 25th–75th percentile, and whiskers = 5th–95th percentile, outliers = open circles, tests are two-tailed. c Boxplots of MITF expression in palbociclib-sensitive and resistant patient groups at indicated stages. Box plots with centerline = median, box = 25th–75th percentile, and whiskers = 5th–95th percentile, outliers = open circles, tests are two-tailed. d GSEA profiling to show the enrichment of the MITF signature geneset in the C1D15 group vs. the C1D1 group. NES score and p values determined by GSEA software. e Palbociclib-resistant and sensitive breast cancer PDX lines were collected and subjected to immunoblotting for proteins as indicated. f Surface plots (left) and synergy matrix (right) to exhibit the synergy between palbociclib and ML329 in palbociclib-resistant PDX WHIM37AR (n = 3 independent experiments). g GSEA profiling to show the enrichment of the CREB geneset in the Surgery group vs. C1D1 group. h GSEA profiling to show the enrichment of CREB geneset in MCF-7 PR cells vs. MCF-7 cells. i MCF-7 and T-47D cells were collected and then subjected to immunoblotting for indicated proteins. j, k MCF-7 PR cells were collected and then subjected to immunoblotting for indicated proteins. (n = 3 independent experiments). l Cell viability was examined in MCF-7 PR cells treated with chemicals as indicated (n = 3 independent experiments). m Schematic of how O-GlcNAcylation of MITF contributes palbociclib resistance in breast cancer cells. See text for details. **p ≤ 0.01, *p ≤ 0.05. All error bars are expressed as mean ± SEM. Two-tailed Student’s t tests were employed for statistical evaluation. Source data are provided as a Source Data file.