Experimental Oncology Differential expression of TIS21 and TIS1 genes in the various organs of Balb/c mice,thymic carcinoma tissues and human cancer cell lines

As a part of a series of investigations on the functions of TIS21 and TIS1 genes, we measuredin vivo 12-O-tetradecanoylphorbol-13-acetate (TPA) inducibility of primary response genes (TIS21, TIS8 and TIS1) in the Balb/c mice and the changes of TIS gene expression in thymic carcinoma tissues and A549 and NCIH69 human lung cancer cell lines.In vivo induction of the TIS genes (TIS21, –8 and –1) by intraperitoneal injection of TPA was dramatic only at the needle contact site,i.e. in the abdominal muscle, not in the thigh muscle. Expression of TIS21 and TIS1 in the Balb/c mice thymus, lung, stomach and spleen was very strong (Lim IK et al. 1994a), regardless of TPA injection. Thymic carcinoma tissues developed in SV40-T-antigen-containing transgenic mice did not express TIS21 and TIS1, and expressed TIS8 weakly. Interestingly, induction of TIS21 expression was obliterated in the human lung cancer cells; A549 cells completely lost the ability to express TIS21 after a combined treatment of TPA and cycloheximide. We also measured the induction of TIS genes by TPA and/or cycloheximide in Raw264.7 mouse macrophage cells and U937 human histiocytic lymphoma cells. However, the induction profile was quite different; repressed and deregulated expression in the U937 cells as compared to rapid and transient induction of TIS genes in the Raw264.7 cells. These data may suggest a repressed expression of TIS21 and TIS1 in the cancer tissue and cells derived from the organs that constitutively express TIS21 in mice and in human cancer cells.Abbreviations TPA 12-O-tetradecanoylphorbol-13-acetate - PBS phosphate-buffered saline - FBS fetal bovine serum