Figure 2: miR-30c corresponds to and regulates chemoresistance of breast cancer cells.

(a-b) Association of Log2-transformed miR-30c expression (fold) with the survival (log2-transformed AUC) of breast cancer cell lines (n=6, T47D, MCF-7, MDA-MB-231, BT20, HCC70 and HCC38) in response to paclitaxel (Taxol) at 0.1–50 nM (a) and doxorubicin at 1–500 nM (b). A linear correlation test P=0.04 for both association studies. (c) Log2-transformed expression levels of miR-30c in MDA-MB-231 cells 48 h after oligo transfections, measured by real-time PCR. P=2.47E-12 by a Student’s t-test (n=3). Error bars represent the s.d. of the mean. (d,e) Cell survival of MDA-MB-231 cells after transient transfection of scrambled control and mature miR-30c oligos, upon 72-h exposure to different doses of paclitaxel (Taxol, d) and doxorubicin (Doxo, e). Student’s t-test P=0.00022 (0.5 nM), 0.00014 (1.0 nM) and 0.00191 (10 nM) for Taxol treatment, and P=0.00802 (10 nM) and 0.00212 (100 nM) for Doxo treatment, comparing 30c samples with Scr samples (n=6). Error bars: s.d.(f) No significant effect of transient transfection of miR-30c on the growth rate of MDA-MD-231 cells, compared with a mock transfection control and a scrambled RNA mimic control. Error bars: s.d. (g) miR-30c sensitized the drug response of BT-20 breast cancer cells to 48-h treatment of doxorubicin (100 nM) and paclitaxel (Taxol, 10 nM). When comparing 30c with controls, Student’s t-test P=5.52E-07 (mock) and 0.0003 (Scr) for Doxo, P=0.0066 (mock) and 0.0009 (Scr) for Taxol (n=5). Error bars: s.d. (h) Representative flow profiles of BT20 breast cancer cell DNA content upon 24-h treatment of paclitaxel (Taxol, 10 nM) or doxorubicin (Doxo, 100 nM). The gated sub-G1 population represents early apoptotic cells. The s.d. values of the mean are shown.