A novel anti-Thy-1 (CD90) monoclonal antibody induces apoptosis in mouse malignant T-lymphoma cells in spite of inducing bcl-2 expression.
Mouse malignant T-lymphoma CS-21 cells can survive and proliferate in vitro when co-cultured with CA-12 stromal cells isolated from lymph nodes, but CS-21 cells undergo apoptotic cell death with DNA fragmentation when cultured alone. We immunized rats with CS-21 cells and raised monoclonal antibodies (MAbs) that recognized Thy-1 (CD90) or CD45 protein. The majority of these MAbs were able to inhibit the adhesion and apoptosis of CS-21 cells. When anti-Thy-1 MAbs were examined for their recognition site on Thy-1 glycoprotein, one of them, MCS-34, was found to recognize both Thy-1.1 and Thy-1.2. In addition, MCS-34, just like the anti-Thy-1 MAb G7, recognized the Thy-1A epitope. G7 was known to induce apoptosis in some T-cell hybridomas and in thymocytes. In CS-21 cells, however, G7 could not induce apoptosis, but MCS-34 could. Interestingly, MCS-34 enhanced the expression of bcl-2 protein, in spite of its ability to induce apoptosis. Upon examining the apoptosis-inducing mechanisms of MCS-34, we found that it promoted a sustained increase in cytoplasmic-free calcium in CS-21 cells. Calcium ionophore A23187 was also found to induce apoptosis in a dose-dependent manner. These results indicate that a sustained increase in cytoplasmic-free calcium by MCS-34 induces apoptosis in CS-21 cells in spite of bcl-2 protein expression.
Fujita
N
N
Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
Kato
Y
Y
Naito
M
M
Tsuruo
T
T
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D015870:Gene Expression; D007167:Immunotherapy; D016399:Lymphoma, T-Cell / Q000473:pathology / Q000628:therapy*; D051379:Mice; D008806:Mice, Inbred AKR; D008810:Mice, Inbred C57BL; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018800:Thy-1 Antigens / Q000276:immunology*; D051028:bcl-2-Associated X Protein
D000911:Antibodies, Monoclonal; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D018800:Thy-1 Antigens; D051028:bcl-2-Associated X Protein; D002118:Calcium