CS1 up-regulates c-maf transactivation in MM cells. (A) Transcriptional and protein changes of CS1, c-maf, and cyclin D2 in CS1-overexpressing U266CS1 and CS1null OPM2 MM cells. The representative probe sets for each gene were used for mRNA expression analysis (P < .003), with confirmation of protein levels by immunoblotting using specific Abs. (B) Transcriptional changes of other c-maf-transactivation targets in U266 versus U266CS1 or OPM2 versus CS1null OPM2 cells (P < .003). Fold changes of listed target mRNA in these cells are shown in Table 1. (C) Integrin β7 expression is enhanced in U266CS1 versus U266 cells, as analyzed by flow cytometry. (D) Top panel: VEGF secretion by U266CS1 or U266 cells, alone or in the presence or absence of BMSCs, as well as in BMSCs alone. Experiments were done in triplicate; error bars represent SE. Fold increase in VEGF induced by MM cell adhesion to BMSCs is shown in the bottom panel. P < .03.