Effect of CD26 inhibition on CXCL12-induced migration. Chemotaxis assays induced by CXCL12 were performed comparing the control untreated Sca-1⁺c-kit⁺lin^— mBM cells (A) and Sca-1⁺c-kit^—lin^— mBM (B) cells to Diprotin A–treated cells. (A) CXCL12 induced a normal dose-dependent migratory response in untreated Sca-1⁺c-kit⁺lin^— mBM cells (•). Treatment with 5 mM Diprotin A (Ile-Pro-Ile) was observed to enhance the migratory response of Sca-1⁺c-kit⁺lin^— mBM cells to CXCL12 (▪, P = .03, n = 8). The enhancement with Diprotin A treatment is equivalent to a 1.7-fold increase in total cell migration in response to 200 ng/mL and 400 ng/mL CXCL12 and 2-fold at 100 ng/mL CXCL12. (B) CXCL12 induced a normal dose-dependent migratory response in Sca-1⁺c-kit^—lin^— mBM cells (•). Treatment with Diprotin A (▪) also enhanced the migratory response of cells to CXCL12 (n = 8, P = .02). The enhancement with Diprotin A treatment is equivalent to a 2-fold increase in total cell migration in response to 200 ng/mL and 400 ng/mL CXCL12 and 2.5-fold at 100 ng/mL. Error bars represent SEMs.