Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0677930 (primary tumor)
 20,210 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Many Experimental and human tumor cell lines have been previously described as being dependent upon exogenous methionine for their in vitro proliferation. The rationale of the experiments described herein was to decrease the in vivo growth of malignant tumors by reducing the exogenous methionine available in diets fed to Wistar AG rats bearing the highly metastatic rhabdomyosarcoma, RMS-J1. The methionine content in the diet was reduced either by replacing casein (diet 1) with soybean protein (diet 4), or by lowering the amount of soybean protein in the diet (from 23 g/100 g to 12 g/100g) (diet 5), or by using a crystalline amino acid-defined mixture as the source of protein (diet 7). In the latter diet homocysteine replaced methionine and allowed the survival of the animals. Diet 4 significantly reduced the mean number of lung metastases without affecting the primary tumor growth. Treatment of RMS-J1 bearing rats with diet 5 led to the decrease of pulmonary invasion (78 and 21 median lung metastases, respectively, in control and treated groups). This diminished metastatic dissemination resulted from the reduced methionine consumption: the lowered casein content in diet 3 (10 g/100 g) as compared to diet 1 (23 g) did not alter primary tumor growth or the amplitude of lung invasion. Moreover, the addition of methionine to diet 5 prevented the diminution of the median number of lung metastases. Replacement of methionine with homocysteine in the crystalline amino acid-defined mixture (diet 7) fed to RMS-J1 bearing rats led to a limited retardation of primary tumor growth (less than 10%) and to a significant decrease in pulmonary invasion: the median number of pulmonary metastases was 28 and 9 for control and treated rats respectively.
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PMID:Decreased rat rhabdomyosarcoma pulmonary metastases in response to a low methionine diet. 367 75

A large proportion of human tumor-derived cell lines and primary tumor cells show methionine-dependent growth. This phenomenon refers to the ability of cells to grow in media containing methionine and the inability of cells to grow in media supplemented with methionine's precursor, homocysteine (Hcy). Methionine can be formed by two different pathways, the recycling pathway and the salvage pathway. To discover the basis for methionine-dependent growth, we have analyzed 12 tumor cell lines and 2 non-tumor-derived cell lines for defects in two key genes in different methionine synthetic pathways. We found little evidence that defects in methionine synthase expression or mutations in the MS gene are correlated with methionine-dependent growth. However, we did find a correlation between methionine-dependent growth and defects in expression of methylthioadenosine phosphorylase (MTAP), a key enzyme in the salvage pathway. Three of the four cell lines lacking detectable MTAP protein were unable to grow in Hcy-containing media, whereas all six of the MTAP-positive cell lines tested showed strong growth. However, when we introduced MTAP cDNA into MTAP-deficient MCF-7 cells, the resulting cell line was still defective in growth on Hcy, although it could now grow on the salvage pathway precursor methylthioadenosine. These findings indicate that salvage pathway defects are not causally related to methionine-dependent growth.
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PMID:Defects in methylthioadenosine phosphorylase are associated with but not responsible for methionine-dependent tumor cell growth. 1103