Agarose-selected variants of two human tumor cell lines exhibit altered methionine auxotrophy

✍ Scribed by Robert G. Liteplo; Sheridan E. Hipwell

• Publisher: John Wiley and Sons
• Year: 1989
• Tongue: English
• Weight: 779 KB
• Volume: 141
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041410328

✦ Synopsis

Our aim was to determine if the selection of human tumor cells with enhanced anchorage-independent growth capacity was associated with alterations in methionine auxotrophy. Cells with an increased ability to form colonies on soft agarose were selected from human melanoma (MeWo) and neuroepithel ioma (SK-N-MC) cell lines. In contrast to their respective parental lines, a high proportion of the agarose-selected variants were completely unable to proliferate in methionine-free medium containing its immediate precursor homocysteine. The variants exhibited no significant change in their total DNA 5-methylcytosine content and showed no stimulation of either RNA or DNA synthesis upon the addition of homocysteine when the cells were cultured in methionine-free medium. These variants were unable to synthesize ['HIS-adenosylmethionine from 13H]adenine and homocysteine. The failure to detect the accumulation of [3H]Sadenosylmethionine in these variant lines was not likely due to the enhanced turnover of S-adenosylmethionine but rather to a reduced ability to synthesize methionine from homocysteine and .!-methyltetrahydrofolic acid. These results support our hypothesis that alterations in the metabolism of methionine and/or intracellular transmethylating activities may contribute to, or be associated with, the autonomous growth of malignant human tumor cells.