Roles of SK-1/S1P2 signaling in the regulation of Bcr-Abl1 expression and drug resistance in human LAMA-4 CML cells. (A) The mRNA levels of S1P2 and SK-1 were measured (and normalized to the levels of rRNA) using Q-PCR in parental LAMA-4 and drug-resistant LAMA-4/IMA cells. (B) Bcr-Abl1 (total) and P-Bcr-Abl1 (Y245) were examined in LAMA-4 and LAMA-4/IMA (first and second panels lanes 1 and 2, respectively) cells using Western blotting. Actin was used as a loading control (third panel). (C-D). Effects of knockdown of SK-1 and/or S1P2 using siRNAs on imatinib-induced growth inhibition (C) or Bcr-Abl1 (total) and P-Bcr-Abl1 expression (D first and second panels lanes 2-4) compared with controls (lane 1) in LAMA-4/IMA cells were determined using trypan blue exclusion and Western blotting, respectively. These experiments were performed in duplicates, and error bars represent SD. *P < .05 was considered significant. In panels B and D, relative expression levels of Bcr-Abl1 or P-Bcr-Abl1 (normalized to actin levels) are shown below each lane.