Figure 3.
MELK inhibition reduces mammosphere formation efficiency in high-MELK-expressing MDA-MB-231 cells. (A) Treatment with the MELK inhibitor OTSSP167 significantly reduced mammosphere formation efficiency in unsorted cells (n = 3, p = 0.0049), ALDH+ cancer stem cells (n = 3, p = 0.0008), and CD44+/CD24− cancer stem cells (n = 3, p = 0.00282). Each condition was normalized to unsorted cells. (B) Representative images of mammospheres for each sorted group under control and the treatment conditions at 10× magnification. (C) Doxycycline (Dox)-inducible shRNA against MELK (shMELK) in CD44+/CD24− MDA-MB-231 cells significantly reduced mammosphere formation efficiency (MFE) after induction (n = 5, p = 2.4 × 10−5), with no significant change observed in cells expressing control shRNA (shControl, n = 5, p = 0.239). (D) Representative photographs of mammospheres formed in shMELK and shControl conditions at 10× magnification. Data represent the mean of independent experiments, with error bars indicating SEM. Statistical comparisons were performed using a 2-sided Student’s t-test. ** p < 0.01, *** p < 0.001, NS p ≥ 0.05. Images were taken at 10× magnification.