PHASE SYNCHRONIZATION STUDY OF THE HUMAN GASTRIC-CANCER LINE HGT-1

The growth of the human gastric cancer cell line HGT-1 is regulated by a gastrin-like peptide through an autocrine process. In order to anal yse the mechanism of action of this peptide, a study at different step s of the cell cycle was considered; so, a blocking of this cell line b y thymidine or hydroxy-urea was studied by cytofluorimetry. In normal growth conditions in 10 % FCS medium, 57 % of the cells were in G0/G1 phase and 31 % in S phase. A treatment with 2 mM hydroxy-urea followed by 4 hours in 10 % FCS medium led to 85 % of the cells in S phase. By successive treatments with thymidine and hydroxy-urea followed by 1 h our in 10 % FCS medium, 2 peaks of S phase corresponding to 86 % of th e cells were observed; after 24 hours, cells were distributed as found for the unconfluent cell line, whatever the treatment. On the other h and, the thymidine kinase activity of unconfluent cells which was rela tively elevated as compared to other cell lines (278 mU/mg protein), w as increased by synchronisation with hydroxyurea followed by 1 hour in 10 % SVF medium (338 mU/mg protein); after 8 hours in 10 % FCS medium , this activity decreased at the value observed for cells treated with thymidine followed by 1 hour in 10 % FCS medium (214 mU/mg protein). In conclusion, a synchronisation either by thymidine or by hydroxy-ure a, led to a blocking of the HGT-1 cell line at different steps of the cell cycle, leading to a better knowledge of its autocrine growth regu lation.