Calpain inhibitor II induces caspase-dependent apoptosis in human acute lymphoblastic leukemia and non-Hodgkin's lymphoma cells as well as some solid tumor cells.
Calpain is a calcium-dependent cysteine protease that is implicated in calcium-dependent cell death, and calpain inhibitors are generally considered as inhibitors of apoptosis. To the contrary, in the present study, we found that calpain inhibitor II (CPI-2) triggers rapid apoptosis in acute lymphoblastic leukemia (ALL) and non-Hodgkin's lymphoma (NHL) cells. All target cell lines were killed by CPI-2, including: ALL-1, a multidrug-resistant BCR-ABL fusion transcript-positive t(9;22) pro-B ALL cell line; RS4;11, a highly radiation-resistant MLL-AF4 fusion transcript-positive t(4;11) pre-pre B ALL cell line; RAMOS, a highly radiation-resistant and p53-deficient Burkitt's lymphoma cell line; DAUDI, a Burkitt's leukemia/lymphoma cell line; NALM-6, a pre-B ALL cell line; and JURKAT and MOLT-3, two T-lineage ALL/NHL cell lines. CPI-2-induced apoptosis in LYN-deficient and BTK-deficient subclones of the DT-40 lymphoma B cell line as effectively as it did in wild-type DT-40 cells. Thus, CPI-2-induced apoptosis is not dependent on the protein tyrosine kinases LYN or BTK. Notably, caspase inhibitor I effectively inhibited CPI-2-induced apoptosis, suggesting that the inhibition of a CPI-2-susceptible protease results in caspase activation, leading to apoptosis in ALL/NHL cells. Unlike the high calpain-expressing ALL/NHL cell lines, myeloid leukemia cell lines HL-60/AML, K562/CML, and U937/AMML, or solid tumor cell lines BT-20/breast cancer, PC-3/prostate cancer, U373/glioblastoma, and HeLa/epitheloid cancer, were not susceptible to the cytotoxicity of CPI-2. Taken together, our results identify calpain as a new molecular target for the treatment of ALL and NHL. CPI-2 and its analogues represent a promising new class of antileukemia/lymphoma agents that deserves further development.
Zhu
D M
DM
Parker Hughes Cancer Center, Wayne Hughes Institute, Roseville, Minnesota 55113, USA.
Uckun
F M
FM
D000077329:Agammaglobulinaemia Tyrosine Kinase; D017209:Apoptosis; D020169:Caspases / Q000378:metabolism*; D002469:Cell Separation; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D019169:Jurkat Cells; D020014:K562 Cells; D008228:Lymphoma, Non-Hodgkin / Q000378:metabolism*; D018613:Microscopy, Confocal; D009842:Oligopeptides / Q000096:biosynthesis*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D013997:Time Factors; D014407:Tumor Cells, Cultured; D020298:U937 Cells; D019061:src-Family Kinases / Q000378:metabolism
D007074:Immunoglobulin G; D009842:Oligopeptides; C069861:calpain inhibitor 2; D004247:DNA; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; C000625949:BTK protein, human; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D020169:Caspases; D016650:Fluorescein-5-isothiocyanate