Assessment of the activities of anti-apoptotic and apoptotic proteins in response to OPN in GIST. (A) Western blotting analysis of the total protein extracts from GIST882, GIST48B, and GIST62 cell lysates. Knockdown assessment of OPN by siRNA in GIST882 cell line was also demonstrated in the lower panel. (B) Quantitation of the western blots by using β-actin as the control, demonstrating increased activities of the anti-apoptotic proteins, Mcl-1 and XIAP, with concomitant suppressed activities of apoptotic proteins Bak, after OPN administration in a dose-dependent manner in imatinib-sensitive GIST882. There were also increased activities of CD44 cleavage and β-catenin (upper). Similar effects of OPN in promoting the expression of β-catenin and Mcl-1 were also noted in imatinib-resistant GIST48B and GIST62 (Columns, mean of results in triplicate; bars, SD. *, P <0.05).