Linked Life Data

9500451

Source:http://linkedlifedata.com/resource/pubmed/id/9500451

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
5
pubmed:dateCreated
1998-3-25
pubmed:abstractText
Dehydroepiandrosterone (DHEA), the major steroid precursor of androgens and estrogens produced in peripheral tissues in primates, is an effective chemopreventive agent in the N-methyl-N-nitrosourea (MNU)-induced rat mammary tumor model. Dietary DHEA (5-600 ppm; 600 mg/kg diet) was administered beginning 1 week before MNU and administered continually throughout the duration of the experiment. The highest dose of DHEA (600 ppm) significantly decreased tumor incidence from 95 to 45% and increased tumor latency and decreased tumor multiplicity from 4.1 to 0.5 tumors/rat. Lower doses of DHEA (5, 24, and 120 ppm) were also effective, decreasing tumor multiplicity by 28, 40, and 55%, respectively, increasing tumor latency in a dose-dependent manner but only minimally affecting final tumor incidence. DHEA in the diet caused a dose-dependent increase in serum levels of DHEA. The 120-ppm dietary dose of DHEA resulted in serum levels of DHEA of approximately 42 pmol/ml levels, similar to those seen in young humans. When we examined whole mounts of mammary glands derived from rats exposed to higher levels of DHEA (600 ppm), we observed a striking increase in lobular development. The doses of DHEA used in these studies (< or =600 ppm) had minimal effects on the induction of fatty acid CoA synthetase, a peroxisome-associated enzyme. In contrast, a dose of 2000 ppm substantially increased levels of peroxisome-associated fatty acid CoA synthetase. The varied and striking efficacy of DHEA was achieved in the absence of any significant effect on body weight gain in the treated rats. Furthermore, tumors from rats treated with MNU alone or rats treated with MNU plus DHEA were examined for the presence of mutations in the Ha-Ras oncogene. There was a slight decrease in the percentage of tumors bearing Ha-Ras mutations in tumors derived from MNU-control rats as contrasted with tumors from MNU-DHEA (120 and 600 ppm)-treated rats. Based on the striking chemopreventive efficacy of continual exposure to DHEA, we examined the effects of more limited exposure to DHEA. Rats were treated with DHEA for a period of 7 weeks immediately before and after MNU injection. Rats were then placed on the control diet for the ensuing 15 weeks. Even this limited exposure to DHEA for a period of 7 weeks profoundly decreased final tumor incidence and multiplicity. Additionally, we examined the effects of intermittent dosing with DHEA. Rats were treated alternatively at 3-week intervals either with diet containing DHEA or with control diet. It was found that this intermittent dosing with DHEA also substantially inhibited the formation of mammary tumors.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0008-5472
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
58
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
921-6
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Modulation of methylnitrosourea-induced breast cancer in Sprague Dawley rats by dehydroepiandrosterone: dose-dependent inhibition, effects of limited exposure, effects on peroxisomal enzymes, and lack of effects on levels of Ha-Ras mutations.
pubmed:affiliation
National Cancer Institute, Bethesda, Maryland 20892, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't