Early full-term pregnancy affords lifetime protection against the development of @entity0 . Parity-induced protection can be reproduced in a carcinogen-induced @entity35 mammary @entity189 model, but the molecular mechanisms of this protection against carcinogenic stimuli in @entity35 mammary glands have not been fully characterized. To gain a better understanding of these molecular mechanisms, we used an oligonucleotide microarray to examine gene expression in parous and age-matched virgin ( @entity9624 ) mammary glands of Lewis @entity35 before and after carcinogen ( @entity7044 ; @entity7045 ) treatment. Parous mammary glands before @entity7045 treatment showed up-regulation of multiple differentiation-related genes, such as whey acidic protein (Wap), @entity52448 ( @entity52448 ), casein gamma (Csng), @entity5752 ( @entity5752 ), @entity1096 ( @entity1096 ) and @entity70257 ( @entity70257 ). Also, parous mammary glands before @entity7045 treatment exhibited down-regulation of growth-related genes such as @entity975 (Reg3a), @entity36705 ( @entity36705 ), @entity5100 ( @entity5100 ) and @entity12561 ( @entity12561 ). After @entity7045 treatment, @entity9624 mammary glands exhibited up-regulation of growth-related genes, such as @entity36705 , cell division cycle 2 homolog A (Cdc2a), @entity5100 , @entity12561 , stathmin 1 (Stmn1) and homeobox, msh-like 1 (Msx1), whereas expression of these genes remained low in parous mammary glands. @entity9624 mammary glands also exhibited marked up-regulation of Cdc2a and Stmn1 in response to @entity7045 . After @entity7045 treatment, the PCNA labeling index increased significantly in @entity9624 mammary epithelial cells (13.7+/-1.1%), but remained low in parous mammary glands (3.6+/-0.4%). The response of @entity9624 mammary glands to carcinogenic stimuli includes up-regulation of growth-related genes and increased cell proliferation. The lack of a similar response in parous mammary glands may explain parity-induced protection against @entity5 development.

Parous mammary glands exhibit distinct alterations in gene expression and proliferation responsiveness to carcinogenic stimuli in Lewis XXXX .

@entity5752 :: ('3929', 'Gene') :: ['lipopolysaccharide binding protein', 'Lbp'] @entity7045 :: ('CHEBI:50102', 'Chemical') :: ['MNU'] @entity975 :: ('5068', 'Gene') :: ['regenerating islet-derived 3 alpha'] @entity0 :: ('MESH:D001943', 'Disease') :: ['breast cancer'] @entity12561 :: ('3487', 'Gene') :: ['insulin-like growth factor binding protein 4', 'Igfbp4'] @entity52448 :: ('1447', 'Gene') :: ['casein beta', 'Csn2'] @entity9624 :: ('12271', 'Species') :: ['AMV'] @entity70257 :: ('644076', 'Gene') :: ['Glycam1', 'glycosylation-dependent cell adhesion molecule 1'] @entity5 :: ('MESH:D009369', 'Disease') :: ['mammary tumor'] @entity189 :: ('MESH:D002277', 'Disease') :: ['carcinoma'] @entity5100 :: ('3481', 'Gene') :: ['insulin-like growth factor 2', 'Igf2'] @entity1096 :: ('6696', 'Gene') :: ['secreted phosphoprotein 1', 'Spp1'] @entity7044 :: ('MESH:D008770', 'Chemical') :: ['N-methyl-N-nitrosourea'] @entity35 :: ('10116', 'Species') :: ['rats', 'rat'] @entity36705 :: ('10232', 'Gene') :: ['Msln', 'mesothelin']
@entity35 :: (10116,Species) :: ['rats']
