|Budget Amount *help
¥7,700,000 (Direct Cost: ¥7,700,000)
Fiscal Year 1997: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1996: ¥6,100,000 (Direct Cost: ¥6,100,000)
We have investigated the molecular mechanism of cell death induced by 5-fluoro-2'-deoxyuridine (FUdR). FUdR caused cell death to induce dNTP pool imbalance and following DNA double strand breaks in mouse mammary tumor FM3A cells. We observed that protease inhibitors (such as TLCK,TPCK,PMSF,p-APMSF,Pefabloc SC,and Z-Asp-CH_2-DCB) blocked intracellular acidification, DNA fragmentation, and FUdR-induced cell death. We also revealed that FUdR-induced death of FM3A cells was found to be associated with an increased expression of cellular c-jun and c-fos genes. The increases in these gene expressions was mediated through the protein kinase C-dependent pathway. Blockage of the expression with the use of antisense oligodeoxynucleotide for c-jun delayd the cell death. These findings suggest that the activation of c-jun and c-fos genes, which encode transcription factors participating in cell proliferation, plays a role in FUdR-induced cell death. We have also found that mode of cell death induced by FUdR changed in wild-type F28-7 clone of FM3A cells after six-month culture. In the original stocked F28-7 clone, FUdR-induced cell death was accompanied by necrosis-like cell swelling and DNA fragmentation to 100-200 kbp with no evidence of associated oligonucleosomal DNA fragmentation. In subclone F28-7-A isolated from F28-7 cells which were cultured for six months, apoptotic bodies and nucleosomal DNA-ladder fragments were observed. Furthemore, we revealed additional findings that at 24 h after treatment with FUdR,caspase-3-like activity increased 24-fold in F28-7 cells and 5.3-fold in F28-7-A cells. Inhibitors of caspases and serine proteases suppressed FUdR-induced cell death and the increase in caspase-3-like activity in both clones. Investigation of differences in mode of cell death between these clones would be important to elucidate the molecular mechanism of pivotal role in deciding subsequent fates of cells toward either apoptosis or necrosis.