Figure 6.

Overexpression of SPHK1 promotes mammosphere formation, but does not affect the proportion of stem-like cells in parental cultures. (A,B) SPHK1 was overexpressed in HCC38 and MDA-MB-468 prior to mammosphere formation assays. The number of mammospheres was counted for each subline and the mammosphere forming efficiency (MFE) determined as the proportion of mammosphere-forming cells relative to the number of single cells seeded. Results are expressed as normalized ratios against the MFE of the vector control cells. Representative phase contrast microscope images are shown. (C) Overexpression of SPHK1 in parental HCC38 and MDA-MB-468 has no effect on the proportion of CD44⁺/CD24^low/- cells. Bars represent the means ± s.d. of three independent experiments. Asterisks (*) indicate statistical significance compared with vector (Vec) control cells (p < 0.01, Student’s t-test).