Enzastaurin specifically inhibits phosphorylation of signaling molecules downstream of PKC. (A) Enzastaurin specifically inhibits TPA-triggered phosphorylation of signaling molecules downstream of PKC. MM.1S cells were processed as described in Figure 1A and immunoblots of cytosolic, membrane, and nuclear fractions were probed with indicated antibodies. (B) Enzastaurin inhibits PKC signaling sequelae in MM cells triggered by BMSC-secreted growth factors and cytokines, as well as costimulation with the extracellular matrix protein fibronectin together with IL-6 or VEGF. Enzastaurin-treated (3 hours) or untreated MM.1S cells were stimulated with conditioned medium from the BMSC line HS-5 (supernatant [SN]), with both VEGF (100 ng/mL) and fibronectin (10 μg/mL; VEGF/FN), or with IL-6 (50 ng/mL) and fibronectin (10 μg/mL; IL-6/FN). Immunoblots were probed with indicated antibodies. (C) Enzastaurin inhibits PKC signaling sequelae in MM cells triggered by MM patient serum (BM-serum). Enzastaurin-treated (3 hours) or untreated MM.1S cells were stimulated with serum from MM patient BM. Immunoblots were probed with indicated antibodies.