POLYAMINE CONTENT AND ONCOGENE EXPRESSION IN HEPATOMA-CELLS IN CULTURE DURING METHIONINE DEPRIVATION AND REFEEDING

From an hepatocarcinoma cell line (LFCL.2A), unable to grow in a cultu re medium in which methionine was replaced by L-homocysteine, we had p reviously isolated revertant clones presenting a low growth rate, a lo ss of tumorigenicity and an inhibition of transcription of three oncog enes: c-Ki-ras, c-Ha-ras and c-myc. Here we showed that long-term depr ivation of methionine led to a depletion of spermine, while putrescine and spermidine contents remained unchanged. When the revertant cells were shifted in a medium containing methionine, the oncogene transcrip tion (except the p53 gene) started very rapidly in parallel with an in crease in the putrescine content. By contrast, spermidine and spermine contents decreased during the first hours but were not significantly different from control values after numerous subcultures in methionine -containing medium.