[Proc Amer Assoc Cancer Res, Volume 45, 2004]
Cellular, Molecular, and Tumor Biology 100: Activation of Apoptosis by Novel Therapeutic Agents
Gemcitabine-induced apoptosis enhanced by cyclin D1 overexpression and reduced by INK4A protein in human gastric cancer cells
Chih-Chun Liu and
Far Eastern Memorial Hospital, Taipei, Taiwan Republic of China, National Taiwan University College of Medicine, Taipei, Taiwan Republic of China, National Taiwan University Hospital, Taipei, Taiwan Republic of China
Exploration of molecular determinants for chemosensitivity is the key element of individualized cancer therapy. Cyclin D1 is a major G1-phase cyclin, together with the CDK4/6, which mediates phosphorylation and functional inactivation of Rb protein. Cyclin D1 overexpression has been demonstrated in a variety of cancers; however, its biologic significance in cancer therapy remains unclear. We have demonstrated that cyclin D1 overexpression may play important roles in differential chemosensitivity of gastric cancer cells. Compared human gastric cancer cells (NCI-N87) with stably transfected cells (N87-D1), which have 3-fold overexpression of cyclin D1, the IC50 for gemcitabine (2-2-difluorodeoxycytidine, dFdC) was more than 1-log lower in N87-D1 (3.1±1.7 nM) than N87 cells (58.6±23.7 nM) by MTT colorimetric cytotoxicity assay. Gemcitabine-induced apoptosis in N87 and N87-D1 cells was shown in both PARP (poly ADP-ribose polymerase) cleavage assay by Western blotting and Annexin-V-FITC apoptosis detection by flowcytometry. The threshold concentration of gemcitabine for PARP cleavage was 5 nM and 500 nM for N87-D1 and N87, respectively. We purified the transducible INK4a protein (p16), a CDK inhibitor of cyclin D-dependent CDK4/6, and transduced into gastric cancer cells. The INK4a-transduced N87 cells readily conferred gemcitabine resistance. Our data demonstrated that gemcitabine can induce apoptosis in gastric cancer cells, and gemcitabine-induced apoptosis is enhanced by cyclin D1 overexpression and reduced by INK4a protein. Further studies for potential clinical use of gemcitabine in individualized chemotherapy for gastric cancer are warranted. (Supported by grants of National Science Council, Taiwan, NSC92-2314-B-418-008).
Copyright © 2004 by the American Association for Cancer Research.