Figure 8.

Depletion of SPHK1 induces increased expression of STAT1 and activates type I and type II interferon signaling. (A) Depletion of SPHK1 expression in parental and CSCs of HCC38 and MDA-MB-468 induced expression of total STAT1, pSTAT1, and IRF9. Expression of total STAT2 and pSTAT2 was unchanged. (B,C) Knockdown of SPHK1 induced type I and II interferon transcriptional activities. HCC38 and MDA-MB-468 parental and CSCs were co-transfected with the SPHK1 shRNA IFN-stimulated response element (ISRE) or gamma-activated sequences (GAS) luciferase reporter constructs. Luciferase activities were determined at 48 h after transfection. Bars represent the means ± s.d. of three independent experiments. Asterisks (*) indicate statistical significance compared with non-silencing (NS) control cells (p < 0.01, Student’s t-test).