PTPN1 and B-cell chronic lymphocytic leukemia: Evidently, PTP1B can be cleaved by the Ca2 + −dependent neutral protease calpain in both platelet agonist-induced aggregation and intestinal epithelial cells [33, 46], and troglitazone, a PTP1B activator, can inhibit STAT3 phosphorylation and augment p53 expression in chronic lymphocytic leukemia (CLL) B cells [47].