Figure 6

Inhibiting epidermal growth factor receptor (EGFR) suppresses the growth of basal-like breast cancer cells. (a) Inhibition of EGFR with Iressa (0.25, 0.5, 1 and 2 μM) blocks the growth of basal-like breast cancer cells by up to 40% when the cells were treated for 72 h (0.5 μM P = 0.02, 1 μM P = 0.02, 2 μM P = 0.07). Each experiment was performed in replicates of six on two separate occasions. (b) Anchorage-independent growth was measured by counting colonies formed after 4 weeks exposure to Iressa or vehicle control. Representative images of colonies following each treatment are shown, with average colony number/well shown underneath. The ability to form colonies was completely lost in the presence of concentrations of Iressa as low as 0.25 μM in SUM149 cells. (c) The ability of HCC1937 cells to form colonies was not effected by Iressa alone; however, knockdown of YB-1 significantly reduced the number of colonies (P < 0.001). The addition of Iressa further reduced the number of colonies. This was highly significant at all concentrations (P < 0.001). Statistical analysis carried out using students t-test; *P < 0.05, **P < 0.01.