Apoptosis of tumor cells induced by mutant and wild type TNFª²¦Á

    LI Yaoª²Chen, CHENG Biª²Zhen, LI Kangª²Sheng

    Department of Microbiology and Immunology, Medical College Shantou University, Shantou, 515031 China

    ¡¾Abstract¡¿ AIM: To compare the apoptosisª²induced ability of recombinant human mutant type 471 rhTNFª²¦Á (mt 471rhTNFª²¦Á) with that of wild type rhTNFª²¦Á (wt rhTNFª²¦Á) and to study the apoptotic mechanism induced by mt 471rhTNFª²¦Á. METHODS: The apoptosis of ZR75ª²1 cells, a breast cancer cell line, induced by mt 471rhTNFª²¦Á or wt rhTNFª²¦Á was analyzed and compared by 20 g/L agarose gel electrophoresis and flow cytometry techniques. The activation profiles of nuclear factor NFª²¦ÊB in ZR75ª²1 cells untreated and treated by mt 471rhTNFª²¦Á or wt rhTNFª²¦Á were detected using Trans AMTM NFª²¦ÊB p65 kit based on ELISA for further study of the apoptotic mechanism induced by mt 471rhTNFª²¦Á. RESULTS: The results from 20 g/L agarose gel electrophoresis of genomic DNA indicated that ZR75ª²1 cells treated by mt 471rhTNFª²¦Á provided a typical apoptotic ladder pattern of DNA fragmentation, whereas weakened ladders were observed in ZR75ª²1 cells treated by wt rhTNFª²¦Á. Flow cytometry showed that the cell apoptotic rate in mt 471rhTNFª²¦Á treated group was 43%, but 25% in wt rhTNFª²¦Á treated group. The mt 471rhTNFª²¦Á held a strong apoptosisª²inducible ability. The results of DNAª²binding activity of NFª²¦ÊB showed that NFª²¦ÊB activation induced by wt rhTNFª²¦Á was significantly higher than that of mt 471rhTNFª²¦Á when the protein concentration of mt 471rhTNFª²¦Á or wt rhTNFª²¦Á reached 50 ¦Ìg/L (P=0.002). CONCLUSION: The apoptosisª²induced ability of mt 471rhTNFª²¦Á is superior to that of wt rhTNFª²¦Á. One of the possible reasons for the enhanced apoptosisª²induced ability may be that NFª²¦ÊB activation is inhibited in tumor cells treated with mt 471rhTNFª²¦Á. ......