Reduced Availability of Endogenously Synthesized Methionine for S-adenosylmethionine Formation in Methionine-Dependent Cancer Cells

Methionine (Met) dependence--i.e., the inability of cultured cells to grow when Met is replaced by its immediate precursor homocysteine (Met-Hcy+medium)--is a frequent component of the oncogenically transformed phenotype. Normal cells, on the other hand, grow in this medium. There have been reports...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1982-07, Vol.79 (14), p.4248-4251
Main Authors: Coalson, Dennis W., Mecham, James O., Stern, Peter H., Hoffman, Robert M.
Format: Article
Language:English
Subjects:
Amino acids
Biochemistry
Cell Division
Cell growth
Cell Line
Cell lines
Cell Transformation, Viral
Cellular metabolism
Cultured cells
Diploidy
Homocysteine - metabolism
Humans
Logarithms
Methionine - metabolism
Neoplasms, Experimental - metabolism
Ratios
S-Adenosylhomocysteine - metabolism
S-Adenosylmethionine - biosynthesis
Simian virus 40
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Summary:Methionine (Met) dependence--i.e., the inability of cultured cells to grow when Met is replaced by its immediate precursor homocysteine (Met-Hcy+medium)--is a frequent component of the oncogenically transformed phenotype. Normal cells, on the other hand, grow in this medium. There have been reports [Hoffman, R. M. & Erbe, R. W. (1976) Proc. Natl. Acad. Sci. USA 73, 1523-1527; Hoffman, R. M., Jacobsen, S. J. & Erbe, R. W. (1978) Biochem. Biophys. Res. Commun. 82, 228-234] of normal or higher rates of Met biosynthesis in Met-dependent cells and a postulation that Met-dependent cells are deficient in utilization of endogenously synthesized Met as opposed to exogenously supplied Met. To answer the critical question of what biochemical reaction(s) requires preformed Met in Met-dependent cells, we labeled cells with Met-free [35S]Hcy or [35S]Met and determined the levels of Met, S-adenosylmethionine (AdoMet), and S-adenosylhomocysteine (AdoHcy). We report here experiments that demonstrate that Met-dependent cells synthesize a normal amount of endogenously synthesized Met and are deficient in utilizing this Met for AdoMet synthesis. In contrast, exogenously supplied Met is utilized normally for AdoMet biosynthesis. The ratio of AdoMet to AdoHcy is low in Met-dependent cells growing in Met-Hcy+medium but is normal in Met+Hcy-medium. We determined that the low AdoMet/AdoHcy ratio probably limits growth of Met-dependent cells in Met-Hcy+medium.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.79.14.4248