Biomedical subjects

Michael C Velarde

Publications and source records attributed to Michael C Velarde.

6 recordsLinked to original sources

PubMed2005

Progesterone receptor transactivation of the secretory leukocyte protease inhibitor gene in Ishikawa endometrial epithelial cells involves recruitment of Krüppel-like factor 9/basic transcription element binding protein-1.

Progesterone receptor (PR), a ligand-inducible transcription factor, mediates the physiological actions of progesterone (P) through two distinct isoforms, PR-A and PR-B, and numerous nuclear coregulators. We previously demonstrated that basic transcription element binding protein-1 (BTEB1), a transcription factor of the Krüppel-like family, is a functional PR-interacting protein, based on the subfertility phenotype and reduced P sensitivity of uterine PR target genes, on BTEB1 null mutation. Here we examined the role of BTEB1 in PR-mediated signaling in endometrial epithelial cells using Ishikawa human endocarcinoma cells and the P-responsive secretory leukocyte protease inhibitor (SLPI) gene. Treatment of Ishikawa cells with P for 24 h increased SLPI and BTEB1 transcript levels without similar effects on PR expression. P induction was abolished by the PR antagonist RU486, whereas knockdown of BTEB1 with short interfering RNA reduced P-responsive BTEB1 but not SLPI expression to basal levels. Forced expression of BTEB1, either by stable or transient transfections of BTEB1 expression constructs in endometrial carcinoma cells, enhanced SLPI promoter activity. Chromatin immunoprecipitation with anti-BTEB1 antibody demonstrated BTEB1 recruitment to the proximal GC-rich containing SLPI promoter region (-97 to -86) in human endometrial carcinoma (Hec1A) cells overexpressing BTEB1. In Ishikawa cells, recruitment of BTEB1 to the proximal, GC-rich region and the distal, progesterone-responsive element-like containing region (-635 to -514) was P dependent and was accompanied by corecruitment of PR and the PR coactivator cAMP-response element binding protein-binding protein. PR-B, rather than PR-A isoform, preferentially associated with BTEB1 in the GC-rich region, whereas both PR isoforms were recruited to the progesterone-responsive element-like site along with BTEB1. Our findings define a novel pathway for BTEB1/PR cross-talk to facilitate P-dependent gene transcription in endometrial epithelial cells.

Cell Line, Tumor↗

PubMed2005

Null mutation of Kruppel-like factor9/basic transcription element binding protein-1 alters peri-implantation uterine development in mice.

Female mice null for the basic transcription element binding protein-1 (Bteb1) gene have reduced numbers of implanting embryos. We hypothesized that the implantation defect, resulting in subfertility, is a consequence of developmental asynchrony between the embryo and uterine endometrium at peri-implantation. To address this, endometrium from wild-type (WT) and Bteb1(-/-) females at 0.5 to 5.5 days postcoitum (dpc) were evaluated for proliferation (BrdU labeling), apoptosis (TUNEL), and steroid hormone receptor expression (immunohistochemistry). Loss of BTEB1 did not affect serum estrogen (E) and progesterone (P) levels. In stroma (ST), the numbers of progesterone receptor (PGR) and HomeoboxA10 (HOXA10)-expressing cells were lower (3.5 and 4.5 dpc), while those of estrogen receptor-alpha (ESR1) were higher (3.5 dpc), with Bteb1 ablation. The peak of proliferation in luminal epithelium (LE), glandular epithelium (GE), and ST was delayed, while the apoptotic index in all cell types was increased (2.5 dpc) in Bteb1(-/-) relative to WT mice. The numbers of PGR-positive ST cells was negatively correlated with LE proliferation in WT mice; this correlation was lost in Bteb1(-/-) mice and was not observed before 2.5 dpc for both genotypes. Proliferation and apoptosis in all endometrial compartments, as well as the numbers of PGR-, HOXA10-, and ESR1-expressing ST cells, were lower in Bteb1(-/-) relative to WT mice after ovariectomy and E + P treatment. Results suggest that BTEB1, by regulating ST PGR expression and transactivation, participates in the paracrine control of LE proliferation by PGR and thus is important for establishment of a receptive uterus critical for successful implantation.

Animals↗

PubMed2005

The soy isoflavone genistein promotes apoptosis in mammary epithelial cells by inducing the tumor suppressor PTEN.

The isoflavone genistein (GEN), a biologically active component of soy foods, is associated with reduced breast cancer risk in women who consume soy-rich diets. GEN has been reported to influence many biological processes, of which suppression of cell proliferation and stimulation of apoptosis are considered to be the major pathways underlying its inhibition of tumorigenesis. This study evaluated the mechanism by which diets containing GEN promote mammary epithelial cell death. We report that mammary glands of young adult female rats exposed from gestation day 4 to postnatal day 50, to AIN-93G diets containing as sole protein source, casein (CAS) supplemented with GEN, or soy protein isolate (SPI+) had increased apoptosis, relative to rats fed CAS diet devoid of GEN. Mammary gland proliferation was unaffected by diet. The increased apoptotic index in mammary glands of GEN and SPI+ rats was accompanied by increased levels of the tumor suppressor protein PTEN (phosphatase and tensin homolog deleted in chromosome ten), albeit enhanced mammary expression of the pro-apoptotic p21, Bax and Bok genes was observed only in GEN-fed rats. GEN-induced apoptosis in MCF-7 cells was concomitant with increased PTEN expression, and this was abrogated by PTEN siRNA. MCF-7 cells treated with serum from GEN- or SPI(+)-fed rats had increased apoptosis as well as increased levels of the PTEN transcript. PTEN siRNA attenuated the increased apoptotic response of MCF-7 cells to serum from rats fed SPI+ or GEN, although the inhibition to basal (CAS serum) apoptotic levels was achieved only for cells treated with GEN serum. Decreased p21 and Bok gene expression accompanied the inhibition of apoptosis by PTEN siRNA. Data implicate PTEN in the induction of apoptosis by GEN and suggest that the promotion of apoptosis leading to inhibition of tumorigenesis in vivo by diets containing GEN may also involve the distinct activities of yet unknown GEN metabolite(s) and/or other systemic factors induced by GEN.

Animals↗

PubMed2005

Uterine phenotype of young adult rats exposed to dietary soy or genistein during development.

Dietary soy intake is associated with protection from breast cancer, but questions persist on the potential risks of the major soy isoflavone genistein (GEN) on female reproductive health. Here, we evaluated intermediate markers of cancer risk in uteri of cycling, young adult Sprague-Dawley rats lifetime exposed to one of three AIN-93G semipurified diets: casein (CAS), soy protein isolate (SPI+ with 276 mg GEN aglycone equivalents/kg) and CAS+GEN (GEN at 250 mg/kg). Postnatal day 50 (PND50) rats lifetime exposed to GEN or SPI+ had similar uterine luminal epithelium height, myometrial thickness, endometrial gland numbers, endometrial immunoreactive proliferating cell nuclear antigen (PCNA), and serum estrogen and progesterone, as CAS-fed rats. GEN-fed rats showed modestly increased apoptosis in uterine glandular epithelium, compared to those of CAS- or SPI+-fed groups. Diet had no effect on the uterine expression of genes for the tumor suppressors PTEN, p53 and p21, and the apoptotic-associated proteins Bcl2, Bax and progesterone receptor. Uterine tissue and serum concentrations of total GEN were higher in rats fed GEN than in those fed SPI+. Human Ishikawa endocarcinoma cells treated with GEN-fed rat serum tended to exhibit increased apoptotic status than those treated with CAS-fed rat serum. Exogenously added GEN (0.2 and 2 microM) increased, while estradiol-17beta (0.1 microM) decreased Ishikawa cell apoptosis, relative to untreated cells. Results suggest that lifetime dietary exposure to soy foods does not alter uterine cell phenotype in young adult rats, while GEN, by enhancing uterine endometrial glandular apoptosis in vivo and in vitro, may confer protection against uterine carcinoma. Given its limited influence on uterine phenotype of young adult females, GEN, when taken as part of soy foods or as supplement, should be favorably considered for other potential health benefits.

Animals↗

PubMed2004

Inhibition of NMU-induced mammary tumorigenesis by dietary soy.

We previously demonstrated that female Sprague-Dawley rats fed AIN-93G diets containing soy protein isolate (SPI+) had lower DMBA-induced mammary tumor incidence than those fed diets containing casein (CAS), due partly to altered Phase I metabolism with soy. Here, we evaluated the tumor protective effects of these same diets to the direct-acting carcinogen N-methyl-nitrosourea (NMU). Tumor incidence was reduced and tumor latency was enhanced, in NMU-administered female rats lifetime exposed to SPI+, relative to the CAS group. Tumor multiplicity did not differ with diet, while tumor grade tended to be more advanced with SPI+. Normal mammary glands of CAS and SPI+ tumor-bearing rats had comparable proliferative and apoptotic status. However, mammary expression of HER-2/neu and progesterone receptor (PR) genes was higher for SPI+ rats. Moreover, tumored SPI+ rats had lower serum progesterone levels than those fed CAS, while serum estrogen did not differ. Serum from tumored SPI+ rats had higher apoptotic activity towards mammary epithelial MCF-7 cells, than CAS serum. Thus, dietary soy protects against mammary tumorigenesis induced by a direct-acting carcinogen and alters signaling pathways involving PR and HER-2/neu.

Alkylating Agents↗

PubMed2004

Dietary exposure to whey proteins alters rat mammary gland proliferation, apoptosis, and gene expression during postnatal development.

We have found that AIN-93G diets made with whey protein hydrolysate (WPH) reduce 7,12-dimethyl-benz[a]anthracene (DMBA)-induced tumor incidence in Sprague-Dawley (Harlan) rats relative to those fed a diet with casein (CAS). Herein, we replicated these findings in another Sprague-Dawley substrain (Charles River) and examined whether WPH protective effects were associated with altered mammary gland differentiation status and expression of the tumor suppressor phosphatase and tensin homolog deleted in chromosome ten (PTEN). Mammary tumor incidence was lower in DMBA-treated rats fed WPH than in those fed CAS. Mammary glands of WPH- and CAS-fed rats were isolated at weaning [postnatal day (PND) 21-28] and at an early adult stage (PND 50-53) and analyzed for proliferative (proliferating cell nuclear antigen immunoreactivity), apoptotic (terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick-end labeling), and differentiation (beta-casein) indices, as well as for PTEN mRNA and protein levels. PND 50-53 rats fed WPH showed decreased proliferation and increased apoptosis in mammary structures, coincident with increased mammary beta-casein gene expression, decreased terminal end-bud numbers, and increased ductal lengths, relative to same-age CAS-fed rats. When challenged with DMBA for 24 h, mammary glands of PND 53 CAS-fed rats had decreased cell survival in both terminal end buds and ductal epithelium, while the mammary glands of WPH-fed rats were not altered from pre-DMBA levels. At 7 d post-DMBA, mammary glands of CAS- and WPH-fed rats exhibited comparable apoptotic indices. Mammary PTEN expression was higher in WPH- than in CAS-fed rats at PND 21-28, but was not different in young adults fed either diet. Results demonstrate that dietary WPH advances mammary gland differentiation during neonatal development and suggest that the transiently increased expression of the pro-apoptotic signal PTEN during a sensitive developmental window may partly underlie the cancer protective effects of WPH.

9,10-Dimethyl-1,2-benzanthracene↗