Fig. 2

Identification of CXCR4 as a crucial gene mediating palbociclib resistance in breast cancer. a Heatmap showing the differential expression genes related to pathways in cancer, determined by RNA-sequencing in palbociclib-resistance than parental MCF-7 cells. (Fold change > 2, p value < 0.05). The p values were determined by negative binomial generalized linear models. b RT-qPCR showing the mRNA level of CXCR4 and CXCL12 in parental and palbociclib-resistance MCF-7 and T47D cells. c Western blotting showing the protein expression of CXCR4 and CXCL12 in parental and palbociclib-resistance MCF-7 and T47D cells. GAPDH as a loading control. Representative images of three biologically independent experiments were shown. d–e Palbociclib-resistance MCF-7 cells were transfected with NC or one of the two siRNAs targeting CXCR4 and then were treated with palbociclib for   5 days (d) or 2 weeks (e). MTT assay (d) and Colony formation assay (e) showing the cell viability with different concentration of palbociclib treatment in control and CXCR4 knocked-down cells. f–g MCF-7 cells were transfected with plasmid vector carried with CXCR4 sequence and then were treated with palbociclib for 5 days (f) or 2 weeks (g). MTT assay (f) and Colony formation assay (g) showing the cell viability with different concentration of palbociclib treatment in control and CXCR4-overexpressed cells.  For e, g, representative images of at the left panel and statistical analysis at the right panel. For b–g, n = 3 biologically independent experiments, the p values were calculated by Student’s t-test for two group comparison and one-way ANOVAs for multiple groups, ***p < 0.001, **p < 0.01