The human lung adenocarcinoma cell line A549 is known to be resistant to tumor necrosis factor alpha (TNF-α)-mediated tumor cell lysis in spite of the expression of 55 kDa TNF receptor (TNF-R55) mRNA and its cell surface protein. In this study, we investigated the mechanism of TNF-α resistance and the role of two types of TNF receptors (TNF-R55 and TNF-R75 (75 kDa TNF receptor)). TNF-R55 or TNF-R75 cDNA was transfected into A549 cells. In addition, a C-terminal deletion mutant of TNF-R75 which lacks the intracellular domain of TNF-R75 was also transfected into A549 cells. We assessed the TNF-α-mediated tumor cell lysis of these transfected clones, and found that the cytotoxic effect increased in transfected clones highly expressing TNF-R55, but not in low-expression clones. As for TNF-R75, the cytotoxic effect of TNF-α was observed in TNF-R75-transfected clones even when expression was low. Furthermore, the cytotoxic effect was also observed in clones transfected with the deletion mutant of TNF-R75, as well as the complete TNF-R75. These results indicate that a certain level of expression of TNF-R55 is necessary for obtaining TNF-α-mediated tumor cell lysis in the absence of TNF-R75. On the other hand, the expression of TNF-R75 strongly induces TNF-α-mediated cytotoxicity through TNF-R55 in the absence of an intracellular signal via TNF-R75.
|Number of pages||8|
|Journal||Japanese Journal of Cancer Research|
|Publication status||Published - 05-1998|
All Science Journal Classification (ASJC) codes
- Cancer Research