Fig. 1
Breast cancer cells exhibit altruistic cooperation. A In situ hybridization for miR-125b or U6 in FFPE breast cancer tissues from patients with (n=26) or without (n=27) neoadjuvant taxane treatment. B Staining for miR-125b in MDA-MB-231miR-125bprom-EGFP cells. Left: stained cells with or without docetaxel exposure. Red triangles: cells with high miR-125b. Right: quantification of miR-125b expression. C Left: Higher magnification of (A). Right: Quantification of percentage of cells with miR-125b vs. U6 expression for 24 miR-125b+ patient samples from (A). D Schema showing how “Relative Survival (RSα)” and “Relative Fitness (RFα)” were measured (See “Methods” and Supplementary Note 1). E-G Bar charts depicting ratio of heterogeneous vs. homogeneous total cell count in early post-treatment for indicated breast cancer cell lines. H-J Bar charts depicting RSα ratio for indicated breast cancer cell lines. K-M Box plots of RFα for “heterogeneous” group of indicated breast cancer cell lines (except cells exposed to 5 and 20nM docetaxel, which did not survive past 3 weeks). N Percentage change in tumor size for MCF-7 xenograft of “homogeneous” or “heterogeneous” study, with or without docetaxel treatment. O Bar chart depicting RSα ratio, xenograft mice from (N), with or without docetaxel exposure. P Box plot of RFα for “heterogeneous” xenograft tumor, with or without docetaxel treatment. Dot: single section read; dots of same colour: sections imaged from same animal. Q Representative images of xenograft tumor biopsy from “homogeneous” and “heterogeneous” group. Black arrows: cells stained positive Mi/EGFP. R Matrix for classifying social behaviour based on RS and RF (See Supplementary Note 1). S Viability of MDA-MB-231miR-125bprom-EGFP cells of cultures of Mi/EGFPHigh and Mi/EGFPLow pure and mixed culture. Red dashed lines show the expected cell viabilities of mixed culture under hypothesis H0 (Upper, without docetaxel) or H1 (Lower, with 5 nM docetaxel). Without docetaxel, cell viability for mixed culture is not significantly different from H0 (two-tailed, T= -0.7241, degree of freedom = 2, P = 0.5442). With docetaxel, cell viability was significantly greater than H1 (two-tailed, T= 4.9884, degree of freedom = 2, P = 0.0379), indicating cooperative effect of minority Mi/EGFPHigh cells in promoting population-wide survival. Experiment repeated three times, representative set shown (B). Data are mean ± s.d. from three independent biological sets of three technical replicates (E-M). n = six independent animals (N), from which three were analyzed for (O), and remaining three for (P,Q). Statistical analysis was performed using Chi-square test (A), two-tailed Mann Whitney U test (B), two-tailed one sample t-test against 1.0 (E-M, P), two-tailed unpaired t-test (N) and one-way ANOVA with post-hoc Tukey HSD (S). NT: no treatment; DTX: docetaxel treatment. Exact P values are shown