Id-1 is not expressed in the luminal epithelial cells of mammary glands

BACKGROUND: The family of inhibitor of differentiation/DNA binding (Id) proteins is known to regulate development in several tissues. One member of this gene family, Id-1, has been implicated in mammary development and carcinogenesis. Mammary glands contain various cell types, among which the luminal epithelial cells are primarily targeted for proliferation, differentiation and carcinogenesis. Therefore, to assess the precise significance of Id-1 in mammary biology and carcinogenesis, we examined its cellular localization in vivo using immunohistochemistry. METHODS: Extracts of whole mammary glands from wild type and Id-1 null mutant mice, and tissue sections from paraffin-embedded mouse mammary glands from various developmental stages and normal human breast were subjected to immunoblot and immunohistochemical analyses, respectively. In both these procedures, an anti-Id-1 rabbit polyclonal antibody was used for detection of Id-1. RESULTS: In immunoblot analyses, using whole mammary gland extracts, Id-1 was detected. In immunohistochemical analyses, however, Id-1 was not detected in the luminal epithelial cells of mammary glands during any stage of development, but it was detected in vascular endothelial cells. CONCLUSION: Id-1 is not expressed in the luminal epithelial cells of mammary glands

Estrogen and progesterone receptors have distinct roles in the establishment of the hyperplastic phenotype in PR-A transgenic mice

Introduction: Expression of the A and B forms of progesterone receptor (PR) in an appropriate ratio is critical for mammary development. Mammary glands of PR-A transgenic mice, carrying an additional A form of PR as a transgene, exhibit morphological features associated with the development of mammary tumors. Our objective was to determine the roles of estrogen (E) and progesterone (P) in the genesis of mammary hyperplasias/preneoplasias in PR-A transgenics.Methods: We subjected PR-A mice to hormonal treatments and analyzed mammary glands for the presence of hyperplasias and used BrdU incorporation to measure proliferation. Quantitative image analysis was carried out to compare levels of latency-associated peptide and transforming growth factor beta 1 (TGFβ1) between PR-A and PR-B transgenics. Basement membrane disruption was examined by immunofluorescence and proteolytic activity by zymography.Results: The hyperplastic phenotype of PR-A transgenics is inhibited by ovariectomy, and is reversed by treatment with E + P. Studies using the antiestrogen ICI 182,780 or antiprogestins RU486 or ZK 98,299 show that the increase in proliferation requires signaling through E/estrogen receptor alpha but is not sufficient to give rise to hyperplasias, whereas signaling through P/PR has little impact on proliferation but is essential for the manifestation of hyperplasias. Increased proliferation is correlated with decreased TGFβ1 activation in the PR-A transgenics. Analysis of basement membrane integrity showed loss of laminin-5, collagen III and collagen IV in mammary glands of PR-A mice, which is restored by ovariectomy. Examination of matrix metalloproteases (MMPs) showed that total levels of MMP-2 correlate with the steady-state levels of PR, and that areas of laminin-5 loss coincide with those of activation of MMP-2 in PR-A transgenics. Activation of MMP-2 is dependent on treatment with E and P in ovariectomized wild-type mice, but is achieved only by treatment with P in PR-A mice.Conclusions: These data establish a link between hormonal response, proliferation, modulation of MMP activity and maintenance of basement membrane integrity that depend on a balance in the expression levels of PR-A and PR-B isoforms. Notably, concomitant increased proliferation, due to inhibition of TGFβ1 activation, and loss of basement membrane integrity, via increased MMP-2 activity, appear to be prerequisites for the PR-A hyperplastic phenotype.Fil: Simian, Marina. Lawrence Berkeley National Laboratory; Estados Unidos. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Bissell, Mina J.. Lawrence Berkeley National Laboratory; Estados UnidosFil: Barcellos Hoff, Mary H.. Lawrence Berkeley National Laboratory; Estados Unidos. NYU Langone Medical Center; Estados UnidosFil: Shyamala, Gopalan. Lawrence Berkeley National Laboratory; Estados Unido

Stabilization of alpha-Li2SO4 at lower temperatures

We report here on the effect of borax, a known modifier, on the conductivity of lithium sulphate. Even with 2 m/o borax, XRD suggests the formation of LiNaSO4. A conductivity enhancement in excess of two orders of magnitude is observed with 10-12 m/o borax. With 15 m/o borax, alpha- Li2SO4 could be stabilized at 764 K

Progesterone receptor expression in medroxyprogesterone acetate-induced murine mammary carcinomas and response to endocrine treatment

Using medroxyprogesterone acetate (MPA) as a carcinogen, we were able to induce in BALB/c female mice, several progestin-dependent mammary ductal carcinomas that regress completely with estrogen or antiprogestins and are maintained by serial transplantations in syngeneic mice. Progestin-independent variants were subsequently generated or appeared spontaneously. Based on their response to estrogen or antiprogestins, we subdivided them into responsive progestin-independent (R-PI) variants which regress completely and unresponsive progestin-independent (UR-PI) carcinomas which are resistant to both families of compounds. In this study we have investigated progesterone receptor (PR) expression in six responsive progestin-dependent, six R-PI, and three UR-PI tumors. Progestin-dependent and R-PI tumors disclosed a higher expression of the PR(A) isoform as compared with PR(B), as well as an additional band of 78 kDa that was not detected in uterine tissue; all were down-regulated by progestins. UR-PI tumors expressed lower levels of all bands in western blots, but were highly reactive by immunohistochemistry. PR RNA expression was detected in both, UR-PI and R-PI tumors. PR binding was comparable in progestin-dependent and R-PI tumors. In the three UR-PI tumors, only 29/61 (48%) of the samples evaluated showed low binding levels, the rest were negative. This report is the first to describe in an experimental model of breast cancer the expression of PR isoforms and their distribution. Our results suggest the expression of functionally altered isoforms in a subgroup of mammary carcinomas, which may explain their lack of hormone response.Fil: Helguero, Luisa A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Viegas, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Asaithamby, Aroumougame. University of California at Berkeley; Estados UnidosFil: Shyamala, Gopalan. University of California at Berkeley; Estados UnidosFil: Lanari, Claudia Lee Malvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Molinolo, Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentin

Id-1 is not expressed in the luminal epithelial cells of mammary glands.

BackgroundThe family of inhibitor of differentiation/DNA binding (Id) proteins is known to regulate development in several tissues. One member of this gene family, Id-1, has been implicated in mammary development and carcinogenesis. Mammary glands contain various cell types, among which the luminal epithelial cells are primarily targeted for proliferation, differentiation and carcinogenesis. Therefore, to assess the precise significance of Id-1 in mammary biology and carcinogenesis, we examined its cellular localization in vivo using immunohistochemistry.MethodsExtracts of whole mammary glands from wild type and Id-1 null mutant mice, and tissue sections from paraffin-embedded mouse mammary glands from various developmental stages and normal human breast were subjected to immunoblot and immunohistochemical analyses, respectively. In both these procedures, an anti-Id-1 rabbit polyclonal antibody was used for detection of Id-1.ResultsIn immunoblot analyses, using whole mammary gland extracts, Id-1 was detected. In immunohistochemical analyses, however, Id-1 was not detected in the luminal epithelial cells of mammary glands during any stage of development, but it was detected in vascular endothelial cells.ConclusionId-1 is not expressed in the luminal epithelial cells of mammary glands

Latent Transforming Growth Factor-β Activation in Mammary Gland : Regulation by Ovarian Hormones Affects Ductal and Alveolar Proliferation

Transforming growth factor-β1 (TGF-β1) is a pluripotent cytokine that can inhibit epithelial proliferation and induce apoptosis, but is also widely implicated in breast cancer progression. Understanding its biological action in mammary development is critical for understanding its role in cancer. TGF-β1 is produced as a latent complex that requires extracellular activation before receptor binding. To better understand the spatial and temporal regulation of its action during mammary gland development, we examined the pattern of activation in situ using antibodies selected to distinguish between latent and active TGF-β. Activation was highly restricted. TGF-β1 activation was localized primarily to the epithelium, and within the epithelium it was restricted to luminal epithelial cells but absent from either cap or myoepithelial cells. Within the luminal epithelium, we noted a further restriction. During periods of proliferation (ie, puberty, estrus and pregnancy), which are stimulated by ovarian hormones, TGF-β1 activation decreased in some cells, consistent with preparation for proliferation. Paradoxically, other cells simultaneously increase TGF-β1 immunoreactivity, which suggests that TGF-β1 differentially restrains epithelial subpopulations from responding to hormonal signals to proliferate. These data suggest that endogenous TGF-β1 activation and thus activity are regulated by ovarian hormones. To determine the specific consequences of TGF-β1 activity, we manipulated TGF-β1 levels in vivo using Tgfβ1 knockout mice and undertook tissue recombination experiments with heterozygous tissue. In Tgfβ1 heterozygous mice, which have <10% wild-type levels of TGF-β1, ductal development during puberty and alveolar development during pregnancy were accelerated, consistent with its role as a growth inhibitor. The proliferative index of Tgfβ1+/− epithelium was increased approximately twofold in quiescent tissue and fourfold in proliferating tissue but both ducts and alveoli were grossly and histologically normal. To test whether epithelial TGF-β1 was critical to the proliferative phenotype, Tgfβ1+/+ and +/− epithelium were transplanted into +/+ mammary stroma. The outgrowth of Tgfβ1+/− epithelium was accelerated in wild-type hosts, indicating that the phenotype was intrinsic to the epithelium. Moreover, proliferation was 15-fold greater in Tgfβ1+/− than wild-type mice after ovariectomy and treatment with estrogen and progesterone, suggesting that TGF-β1 acts in an autocrine or juxtacrine manner to regulate epithelial proliferation. Together these data indicate that ovarian hormones regulate TGF-β1 activation, which in turn restricts proliferative response to hormone signaling