EFFECT OF HEAT-SHOCK ON EXPRESSION OF TRANSFORMING-GROWTH-FACTOR BETA-1 MESSENGER-RNA IN TUMOR-CELLS

To address the question about the reasons for nonuniform action of hyp erthermia on the growth behaviour of different tumor cells, we studied the expression of mRNA for transforming growth factor (TGF) pi in the heat-shocked human lung carcinoma A-549 cells and human fibrosarcoma MT-1080 cells. We used these cells in our study because of the growth inhibiting action TGF-beta 1 on A-549 cells and its growth stimulating action on MT-1080 cells. We supposed that hyperthermia could act diff erentially on the expression of TGF-beta 1 mRNA in these tumor cells. We found an increase in the level of TGF-beta 1 mRNA expression in hea t-treated (44 degrees C, 30 min) A-549 cells. Such action was revealed 48 h after the discontinuation of hyperthermia action on the cells cu ltured in a serum-supplemented medium and was not observed when the ce lls were cultured in a serum-free medium. This effect was opposite in case of MT-1080 cells. Here, the stimulation of TGF-beta 1 mRNA expres sion under the action of a heat shock could be seen only when the cell s were cultured in a serum-free medium but not when the cells were cul tured in a serum-supplemented medium. It should be also noted that the level of expression of TGF-beta 1 mRNA was much higher in HT-1080 fib rosarcoma cells than in A549 carcinoma cells and this corresponds to t he ability of TGF-beta 1 to stimulate growth in MT-1080 cells. The dat a obtained suggest that various patterns of the growth behaviour of tu mor cells under the hyperthermia action could be partly explained by a differential effect of this treatment on the expression of TGF-beta 1 as well as the provision of these cells with some cytokines present i n the extracellular medium.