Dietary soybean isolate and methionine supplementation affect mammary tumor progression in rats.
The effect of feeding soybean protein isolate (SBP) diet or soybean protein isolate diet supplemented with 0.7% DL-methionine (SBP + Met) on mammary tumor progression was investigated. Sprague-Dawley female rats were fed from weaning a 20% casein (CAS) diet supplemented with 0.3% DL-methionine (AIN-76) and injected via jugular vein with N-nitrosomethylurea (NMU, 40 mg/kg body weight) at 7 wk of age. Five weeks after NMU treatment, animals were divided into the three isoenergetic, isoprotein diet groups: CAS (25 rats); SBP (26 rats) and SBP + Met (25 rats). First palpable mammary tumors were evident 8, 9 and 13 wk and the mean latency period was 13.30 +/- 1.23, 16.70 +/- 1.32 and 17.82 +/- 1.28 wk after NMU treatment in the CAS, SBP + Met and SBP diet groups, respectively. Tumor incidence was 80% in the CAS group compared with 42.3% in the SBP group (P = 0.01). Methionine supplementation increased tumor incidence to 64%. Total number and total weight of tumors was greater in the CAS group compared with either SBP + Met or SBP groups: 41 vs. 28 or 21 tumors and 97.28 g vs. 27.87 or 32.46 g, respectively. These data indicate that SBP diet, low in methionine content, fed 5 wk after carcinogen exposure significantly repressed mammary tumor progression. Methionine supplementation increased the number of animals with tumors but not the mean tumor weight.
Hawrylewicz
E J
EJ
Department of Research, Mercy Hospital and Medical Center, Chicago, IL 60616.
Huang
H H
HH
Blair
W H
WH
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002273:Carcinogens / Q000008:administration & dosage; D002364:Caseins / Q000009:adverse effects; D004032:Diet; D005260:Female; D007275:Injections, Intravenous; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000517:prevention & control*; D008715:Methionine / Q000008:administration & dosage; D008770:Methylnitrosourea / Q000633:toxicity; D051381:Rats; D011919:Rats, Inbred Strains; D013025:Glycine max
D002273:Carcinogens; D002364:Caseins; D008770:Methylnitrosourea; D008715:Methionine