miRNA profiling in mammospheres. An oligonucleotide array was used for comparing the miRNA expression between mammospheres (MMO) and parental MCF7 cells. A. Scatter plot of 2 technical replicates showing a significant correlation for all miRNA probes. B. Unsupervised clustering distinguishing MMO from parental MCF7 cells and from MMO plated in attachment conditions (DIFF MMO). C. Scatter plot comparing MMO and MCF7 parental cells. Upregulated and downregulated miRNAs are shown in red. Green dots represent miRNAs significantly downregulated in MMO after class comparison analysis (no miRNA was significantly upregulated in MMO). D. Cluster and heat-map analyses are shown for the MMO/MCF7 comparison. miRNAs significantly downregulated in MMO match the miRNAs represented in green in Figure 1C. E. Two miRNAs from the previous analysis (miR-30a and miR-26a) were validated using TaqMan probes in independent samples. F. miR-30a expression was studied in an unrelated breast cancer cell line, 4T1. Mammospheres derived from 4T1 cells expressed significantly lower levels of miR-30a. P value under 0.05 (two-tailed student t test) is represented with an asterisk (*).