Effects of estradiol and medroxyprogesterone acetate on morphology, proliferation and apoptosis of human breast tissue in organ cultures

Background

Human breast tissue undergoes phases of proliferation, differentiation and regression regulated by changes of the levels of circulating sex hormones during the menstrual cycle or aging. Ovarian hormones also likely play a key role in the etiology and biology of breast cancer. Reports concerning the proliferative effects of steroid hormones on the normal epithelium of human breast have been conflicting. Some studies have shown that steroid hormones may predispose breast epithelial cells to malignant changes by stimulating their proliferation, which is known to be regulated tightly by stromal cells.

The aim of this study was to investigate the effects of 17β-estradiol and medroxyprogesterone acetate on proliferation, apoptosis, expression of differentiation markers and steroid hormone receptors in breast epithelium using an in vitro model of freshly isolated human breast tissue, in which a proper interaction of breast epithelium and stroma has been maintained.

Methods

Human breast tissues were obtained from women undergoing surgery for breast tumours. Peritumoral tissues were excised and explants were cultured for 3 weeks in medium supplemented with E₂ or MPA or with E₂+MPA. Endpoints included histopathological, histomorphometric and immunohistochemical assessment of the breast explants.

Results

Culture of breast explants for 14 or 21 days with steroid hormones increased proliferative activity and the thickness of acinar and ductal epithelium. E₂-treatment led to hyperplastic epithelial morphology, MPA to hypersecretory single-layered epithelium and E₂+MPA to multilayered but organised epithelium.

The proliferative response to E₂ in comparison to control (p < 0.001) was more pronounced than to MPA (p < 0.05) or E₂+MPA (p < 0.05) at 7 and 14 days for Ki-67 and PCNA. E₂ treatment also decreased the proportion of apoptotic cells after 7 (p < 0.01) and 14 (p < 0.01) days. In addition, the relative number of ERα, ERβ and PR positive epithelial cells was decreased by all hormonal treatments.

Conclusion

Organ culture system provides a model for studying the direct effects of steroid hormones and their analogues on postmenopausal human breast tissue.

Addition of E₂ or MPA or E₂+MPA to breast explants caused characteristic changes in morphology, stimulated epithelial proliferation, lowered apoptosis ratio and decreased the relative number of epithelial cells expressing ERα, ERβ and PR.

Beneficial effects of soy protein in the initiation and progression against dimethylbenz [a] anthracene-induced breast tumors in female rats

This study was to demonstrate by histological grading whether soy protein protects against dimethylbenz[a]anthracene (DMBA) -induced breast tumors in female rats. At 25 days of age, rats were fed diets containing either casein or soy protein. After 25 days on diets, a single dose of DMBA in sesame oil (80 mg/kg) was administered by gavage. All tumors were detected by palpation. The number of tumors per rat was less in soy group than that in casein group at any time point up to 122 days after DMBA administration. Incidence of tumors was less in soy protein group than that in casein group. Casein group had 20% grade I, 60% grade II, and 20% grade III adenocarcinoma. However, the soy group had 100% grade I adenocarcinoma and no aggressive grade II or grade III tumor. There was a delay in the development of tumor in the soy protein group in comparison to the casein group. Again, unlike casein, the soy group had cessation of angiogenesis at several sites of tumor, and reduced levels of angiogenic markers, VEGF and bFGF. Immunohistochemical analysis of the breast tissues did not show any CD-31 positive stain in soy protein group, whereas some CD-31 positive stain was revealed in casein group, which further suggests that soy protein controls angiogenesis. Furthermore, proliferative index as assessed by Ki-67 staining was less in soy protein group than that in casein group. These findings suggest that the soy protein may protect against the development of a more aggressive breast carcinoma.

Nuclear morphometry in columnar cell lesions of the breast: is it useful?

AIMS

To evaluate the nuclear morphometric features of breast columnar cell lesions (CCLs) observed on mammotome core biopsies, to determine if there are significant measurable differences between those with atypia and those without. Correlation with follow-up open excision specimens was made.

METHODS

Mammotome core biopsies performed on patients that contained CCLs were derived from the departmental case files. Histological material was reviewed and foci of CCLs demarcated for nuclear morphometric assessment, which was accomplished using an imaging system. Nuclear parameters studied were nuclear area and perimeter, circularity factor and feret's diameter. Statistical analysis used the GraphPad Prism software, with p<0.05 indicating significance.

RESULTS

On examination of core biopsies of 40 patients with CCLs, 8 lesions were benign, 4 showed atypical lobular hyperplasia, 8 showed CCLs with nuclear atypia, 19 disclosed atypical ductal hyperplasia (ADH) and 1 showed ductal carcinoma in situ (DCIS). The nuclear area, perimeter and feret's diameter of CCLs with atypia were significantly greater than those without (p = 0.04, 0.03 and 0.019, respectively), whereas no difference was observed in the circularity factor. Follow-up open excision biopsy specimens in 24 patients showed upgrading to DCIS in 40% of cases diagnosed initially with ADH on core biopsy compared with 20% of CCLs with atypia.

CONCLUSIONS

Nuclear morphometry in CCLs confirms nuclear size as the key parameter in the assessment of nuclear atypia. Whether it can be potentially used as an adjunctive tool depends on the establishment of appropriate cut-offs.

Electron microscopic findings for diagnosis of breast lesions

The normal mammary gland can be roughly divided into the large duct close to the nipple and the terminal duct located within the lobulus. Both the large duct and the terminal duct are composed of epithelial cells and myoepithelial cells. The epithelial cells can be divided into light and dark cells using electron density. Heterochromatin is the predominant type of chromatin found in normal mammary glands. The cytoplasm of myoepithelial cells contains a number of fine filaments that possess dense patches. The myoepithelial cells of the large duct have a large process with a crablike appearance that protrudes from the cytoplasm. The myoepithelial cells of the terminal duct, by contrast, assume a relatively flat form and are approximately parallel to the epithelial-stromal junction. If the nuclei of the epithelial cells of normal mammary glands and benign breast lesions are compared with those of malignant breast lesions, the latter are primarily oval or circular in shape whereas the former often show marked notches. The predominant chromatin is heterochromatin in noncancer cells and euchromatin in cancer cells. The intracytoplasmic lumen (ICL) can be roughly divided into two types. The ICL is frequently seen in breast cancers, especially scirrhous carcinoma and lobular carcinoma. Invasive ductal carcinoma can be divided into three types: papillotubular carcinoma, solid-tubular carcinoma, and scirrhous carcinoma. Scirrhous carcinoma can be divided into two subtypes: scirrhous carcinoma in the broader sense of the term (characterized by scirrhous invasion of the stroma by papillotubular carcinoma or solid-tubular carcinoma), and scirrhous carcinoma in the narrower sense of the term (characterized by linear or cluster-like invasion of the stroma without forming ducts). Ultrastructural characteristics of scirrhous carcinoma in the narrow sense are bright cytoplasm (seen in most cells) and euchromatin (seen in all cells of this type of carcinoma). In cases of papillotubular carcinoma, solid-tubular carcinoma, and scirrhous carcinoma in the broad sense, euchromatin is predominant but sporadic cells with heterochromatin are also seen. Adenoid cystic carcinoma and carcinoid tumor of the breast are histological types of breast carcinoma that show characteristic features under an electron microscope. Ultrastructurally, the former shows a pseudocyst and true lumen whereas the latter presents numerous neuroendocrine granules within the cytoplasm. Breast carcinoma shows several ultrastructural characteristics that are useful in differential diagnosis. Therefore, it is advisable to take electron microscopic findings into account when evaluating or diagnosing breast lesions.

BRCA1 promoter methylation in sporadic breast cancer is associated with reduced BRCA1 copy number and chromosome 17 aneusomy

To explore the molecular mechanisms for the similarities between inherited and noninherited forms of breast cancer, we tested the hypothesis that inactivation of BRCA1 by promoter hypermethylation is associated with reduced gene copy number and chromosome 17 aneusomy as observed in tumors from BRCA1 mutation carriers. Using a combination of methylation-specific PCR analysis and fluorescence in situ hybridization, we observed varying degrees of promoter methylation in 39 of 131 (29.8%) primary tumors. Despite significant tumor heterogeneity, mean copy numbers of BRCA1 and CEP17 per cell were lower in methylated cases compared with unmethylated cases [1.78 versus 2.30 (P = 0.001) and 1.85 versus 2.29 (P = 0.005), respectively]. Methylation was more frequently observed in younger women (P = 0.05) with high-grade (P = 0.001), estrogen receptor-negative (P = 0.04), and progesterone receptor-negative (P = 0.01) tumors. Moreover, methylation was associated with reduced or absent BRCA1 transcripts, which was reversible in the heavily BRCA1-methylated cell line UACC3199 following treatment with 5-aza-2'-deoxycytidine and trichostatin A. We identified five CpGs at positions -533, -355, -173, -21, and +44 as critical in the reexpression of BRCA1. We conclude that BRCA1 methylation contributes to a subset of sporadic breast cancers with the resulting molecular and clinicopathologic phenotype similar to that of hereditary BRCA1-associated breast cancers. Our data support a model of carcinogenesis in which BRCA1 promoter methylation may serve as a "first hit," much like an inherited germ line mutation, and promote tumor progression down a restricted set of molecular pathways.

Differential subcellular distribution of glucose transporters GLUT1–6 and GLUT9 in human cancer: Ultrastructural localization of GLUT1 and GLUT5 in breast tumor tissues

It has been proposed that the enhanced metabolic activity of tumor cells is accompanied by an increased expression of facilitative hexose transporters (GLUTs). However, a previous immunohistochemical analysis of GLUT1 expression in 154 malignant human neoplasms failed to detect the GLUT1 isoform in 87 tumors. We used 146 normal human tissues and 215 tumor samples to reassess GLUT1 expression. A similar number of samples were used to compare the expression of GLUT2-6 and 9. The classical expression of GLUT1-5 in different normal human tissues was confirmed, however, we were unable to detect GLUT2 in human pancreatic islet cells. GLUT6 was principally detected in testis germinal cells and GLUT9 was localized in kidney, liver, heart, and adrenal. In tumor samples, GLUT1, 2, and 5 were the main transporters detected. GLUT1 was the most widely expressed transporter, however, 42% of the samples had very low-to-negative expression levels. GLUT2 was detected in 31% of the samples, being mainly expressed in breast, colon, and liver carcinoma. GLUT5 was detected in 27% of breast and colon adenocarcinoma, liver carcinoma, lymphomas, and testis seminoma samples. In situ RT-PCR and ultrastructural immunohistochemistry confirmed GLUT5 expression in breast cancer. GLUT6 and 9 are not clearly over-expressed in human cancer. The extensive expression of GLUT2 and 5 (glucose/fructose and fructose transporters, respectively) in malignant human tissues indicates that fructose may be a good energy substrate in tumor cells. Our functional data obtained in vitro in different tumor cells support this hypothesis. Additionally, these results suggest that fructose uptake could be used for positron emission tomography imaging and, may possibly represent a novel target for the development of therapeutic agents in different human cancers.

Normal and pathological breast, the histological basis

Breast tissue is heterogeneous, associating connective and glandular structures, which grow and change cyclically under hormonal regulation. Hormones are also thought to be the main determinant of the major benign and malignant pathologies encountered in the breast. Benign lesions are more frequent and fibrocystic changes are by far the most common among them. They usually associate different entities, (adenosis, fibrosis, cysts and hyperplasia) but vary in intensity and extension. Thus, their clinical and radiographic presentation is extremely different from one patient to another. Adenofibroma is the most frequent tumour. It also undergoes modifications according to hormonal conditions. About 90% of malignant tumours are primary carcinoma. The incidence of intra-ductal carcinoma has risen dramatically since the development of screening because of its ability to induce calcification. Two mechanisms could be involved in the formation of calcification: one active (tumour cell secretion of vesicles), the other passive (necrotic cell fragments are released). Invasive carcinoma comprises numerous histological types. Stromal reactions essentially determines their shape: a fibrous reaction commonly found in ductal carcinoma creates a stellate lesion while other stroma, inflammatory (medullary carcinoma), vascular (papillary carcinoma) or mucinous determine nodular lesions whose borders push the surrounding tissue. The histological features which give rise to the radiographic pattern will be emphasised.

Scanning electrochemical microscopy of living cells. 5. Imaging of fields of normal and metastatic human breast cells

Scanning electrochemical microscopy (SECM) was used to image fields of different types of human breast cells in monolayer culture. The goal of these experiments was to demonstrate the possibility of distinguishing between nontransformed human breast epithelial cells (MCF-10A) and metastatic breast cells (MDA-MB-231) by their redox activities. Imaging of densely packed cells by SECM requires approaches that differ from previously reported experiments with well-separated single cells. The combination of SECM with optical and fluorescence microscopies was used to locate individual cells in a homogeneous or heterogeneous field of cells. To establish that metastatic breast cells can be detected against a field of normal cells, the former were preloaded with fluorescent nanospheres and plated together with unlabeled MCF-10A cells. By matching SECM and fluorescence images of a selected group of metastatic cells, the level of discrimination and fidelity of the SECM signal could be shown. Several factors (distance between the electrode and the cells, cell density, choice of mediator, and its concentration) were identified that can be used to maximize the contrast between images of metastatic and nontransformed cells. These studies provide a framework for future analysis of malignant cells in human breast tissue samples.

Microfabricated silicon microneedles for nonviral cutaneous gene delivery

BACKGROUND

The skin represents an accessible somatic tissue for therapeutic gene transfer. The superficial lipophilic layer of the skin, the stratum corneum, however, constitutes a major obstacle to the cutaneous delivery of charged macromolecules such as DNA.

OBJECTIVES

To determine whether silicon-based microneedles, microfabricated via a novel isotropic etching/BOSCH reaction process, could generate microchannels in the skin of sufficient dimensions to facilitate access of lipid : polycation : pDNA (LPD) nonviral gene therapy vectors.

METHODS

Scanning electron microscopy was used to visualize the microconduits created in heat-separated human epidermal sheets after application of the microneedles. Following confirmation of particle size and particle surface charge by photon correlation spectrocopy and microelectrophoresis, respectively, the diffusion of fluorescent polystyrene nanospheres and LPD complexes through heat-separated human epidermal sheets was determined in vitro using a Franz-type diffusion cell. In-vitro cell culture with quantification by flow cytometry was used to determine gene expression in human keratinocytes (HaCaT cells).

RESULTS

The diffusion of 100 nm diameter fluorescent polystyrene nanospheres, used as a readily quantifiable predictive model for LPD complexes, through epidermal sheets was significantly enhanced following membrane treatment with microneedles. The delivery of LPD complexes either into or through the membrane microchannels was also demonstrated. In both cases considerable interaction between the particles and the epidermal sheet was observed. In-vitro cell culture was used to confirm that LPD complexes mediated efficient reporter gene expression in human keratinocytes in culture when formulated at the appropriate surface charge.

CONCLUSIONS

These studies demonstrate the utility of silicon microneedles in cutaneous gene delivery. Further studies are required to elucidate fully the influence of the physicochemical characteristics of gene therapy vectors, e.g. particle diameter and surface charge, on their diffusion through microchannels and to quantify gene expression in vivo.

PEA3 transcription factors are expressed in tissues undergoing branching morphogenesis and promote formation of duct-like structures by mammary epithelial cells in vitro

The genetic program that controls reciprocal tissue interactions during epithelial organogenesis is still poorly understood. Erm, Er81 and Pea3 are three highly related transcription factors belonging to the Ets family, within which they form the PEA3 group. Little information is yet available regarding the function of these transcription factors. We have previously used in situ hybridization to compare their expression pattern during critical stages of murine embryogenesis [Oncogene 15 (1997), 937; Mech. Dev. 108 (2001), 191]. In this study, we have examined the expression of PEA3 group members during organogenesis of the lung, salivary gland, kidney, and mammary gland. In all of these developmental settings, we observed a tight correlation between branching morphogenesis and the expression of specific members of the PEA3 group. To assess the functional relevance of these findings, Erm and Pea3 were overexpressed in the TAC-2.1 mammary epithelial cell line, which has the ability to form branching duct-like structures when grown in collagen gels. We found that overexpression of Erm and Pea3 markedly enhances branching tubulogenesis of TAC-2.1 cells and also promotes their invasion into a collagen matrix. Collectively, these findings suggest that the differential expression of PEA3 group transcription factors has an important role in the regulation of branching morphogenesis and raise the question of their implication in branching signaling.

Detection of interferon-gamma-inducible chemokines in human milk

AIM

To assess the immunological role of human milk by analysing the concentrations of interferon-gamma-inducible protein of 10 kda (IP-10) and monokine induced by interferon-gamma (MIG) in human milk from mothers of preterm and term infants.

METHODS

IP-10 and MIG levels of colostrum, early milk, mature milk and sera were measured by enzyme-linked immunosorbent assay (ELISA). IP-10 and MIG mRNA expression levels in cellular components of human milk were determined by RT-PCR. IP-10 and MIG protein expression in mammary gland tissues was analysed by immunohistochemistry.

RESULTS

Significant amounts of IP-10 and MIG were detected in human milk. The concentrations of IP-10 and MIG in colostrum and early milk were significantly higher than those of sera from healthy controls or lactating mothers. These chemokine concentrations in colostrum and early milk were significantly higher than those of mature milk. Premature delivery or pregnancy complications of mothers had no significant correlation with these chemokine concentrations in breast milk. There were significant correlations between MIG and interferon-gamma (IFN-gamma) or IP-10 levels (p < 0.001) in human milk. Expression of IP-10 and MIG genes and proteins in the milk cells as well as in mammary gland epithelial tissues was detected by RT-PCR and immunohistochemistry.

CONCLUSION

IP-10 and MIG in human milk, probably derived from milk cells and mammary gland epithelial cells, may contribute to the migration and activation of intestinal T lymphocytes to enhance mucosal immunity during the early neonatal period.

Zinc transporters 1, 2 and 4 are differentially expressed and localized in rats during pregnancy and lactation

Zinc metabolism is controlled within relatively restricted limits throughout the life cycle. Expression and localization of zinc transporters 1, 2 and 4 during pregnancy and lactation in small intestine, mammary gland and liver of the rat were investigated using Northern analysis, Western blotting and immunohistochemistry. In maternal tissues, zinc transporter 4 was the most widely expressed among these zinc transporters in the tissues examined. In small intestine and liver, zinc transporter 4 increased from levels found during late gestation, but zinc transporter 1 did not. Zinc transporter 2 expression in small intestine was transient, being highest around parturition, and was not detected in liver. Immunohistochemistry revealed unique patterns of zinc transporter localization at different stages of development. In the placenta, zinc transporters 1 and 4 were found concentrated along the villous visceral splanchnopleure. In the mammary gland, zinc transporter 4 was most abundant in cells surrounding the alveolar ducts and oriented to the basement lamina. All three transporters were highly expressed in neonatal small intestine, principally near the apical surface, but zinc transporters 1 and 4 increased in abundance at the basolateral surface during development. Zinc transporter 2 was oriented apically, directly adjacent to the microvilli of enterocytes. Within the intestine, expression of each transporter was limited to enterocytes. These results support a role for these transporters in maintaining an adequate zinc supply derived from the maternal diet for zinc acquisition and use by the fetus and neonate.

A novel method of imaging lysosomes in living human mammary epithelial cells

Cancer cells invade by secreting degradative enzymes which, under normal conditions, are sequestered in lysosomal vesicles. The ability to noninvasively label lysosomes and track lysosomal trafficking would be extremely useful to understand the mechanisms by which degradative enzymes are secreted in the presence of pathophysiological environments, such as hypoxia and acidic extracellular pH, which are frequently encountered in solid tumors. In this study, a novel method of introducing a fluorescent label into lysosomes of human mammary epithelial cells (HMECs) was evaluated. Highly glycosylated lysosomal membrane proteins were labeled with a newly synthesized compound, 5-dimethylamino-naphthalene-1-sulfonic acid 5-amino-3,4,6-trihydroxy-tetrahydro-pyran-2-ylmethyl ester (6-O-dansyl-GlcNH2). The ability to optically image lysosomes using this new probe was validated by determining the colocalization of the fluorescence from the dansyl group with immunofluorescent staining of two well-established lysosomal marker proteins, LAMP-1 and LAMP-2. The location of the dansyl group in lysosomes was also verified by using an anti-dansyl antibody in Western blots of lysosomes isolated using isopycnic density gradient centrifugation. This novel method of labeling lysosomes biosynthetically was used to image lysosomes in living HMECs perfused in a microscopy-compatible cell perfusion system.

Effect of 4-hydroxytamoxifen isomers on growth and ultrastructural aspects of normal human breast epithelial (HBE) cells in culture

In the search for a breast cancer prevention strategy which would avoid undesirable effects of orally administered tamoxifen, the percutaneous administration of the highly active metabolite 4OHTamoxifen (4OHTam) has been proposed. Percutaneous 4OHTam penetrates the skin to reach breast tissues. It, thus, avoids the hepatic first pass effect, and offers an optimal local/systemic effect. However, trans-4OHTamoxifen can spontaneously isomerize into the cis-isomer, which may have estrogen agonist action. The aim of this study was to examine the effect of cis-4OHTam on normal human breast epithelial (HBE) cells in culture. Spontaneous isomerization of trans- into cis-4OHTam occurred within 24-48h, but stabilized rapidly at a trans/cis ratio of 70/30, whether in stock solution, culture medium or cultured cells. The cis-4OHTam did not stimulate HBE cell growth according to histometric cell counts and scanning electron microscopy analysis, but inhibited E(2)-induced cell growth, albeit two to three times less than trans-4OHTam. In conclusion, spontaneous isomerization of trans- to cis-4-OHTam is limited and 4OHTam retains a marked antiestrogenic effect. It may prove to be a useful alternative to tamoxifen in breast cancer prevention, especially if administered percutaneously.

Carrageenan-induced inclusions in mammary myoepithelial cells

The purpose of this investigation was to characterize the ultrastructural changes that occur in mammary myoepithelial cells (MMEC) following exposure in tissue culture to low concentrations of lambda-carrageenan, a sulfated polysaccharide commonly used as a food additive. MMEC were obtained from reduction mammoplasty, grown in tissue culture, exposed for varying durations to low concentrations (0.0014%-0.0001%) of lambda-carrageenan, and examined by transmission electron microscopy, following staining for acid phosphatase and for aryl sulfatase. Carrageenan appeared to enter the cells by membrane-associated endocytic vesicles and accumulate in endosomes and lysosomes. Unusual lamellar inclusions were identified within lysosomes of the MMEC, and lysosomal vacuolation arose in association with the inclusions. The observed changes appeared to lead to destruction of the MMEC by release of proteolytic enzymes from the distorted lysosomes, similar to the process observed in lysosomal storage diseases.

Proteoglycan–collagen associations in the non-lactating human breast connective tissue during the menstrual cycle

The human mammary gland undergoes a sequence of histological changes in both epithelial and stromal compartments during the menstrual cycle. Swelling and unswelling of the breast stromal tissue is a characteristic feature of the two phases of the cycle and is mediated by changes in the water content of sulfated proteoglycans in the matrix between the fibrils. In an ultrastructural study we investigated the distribution of sulfated proteoglycans identified as cupromeronic blue-positive needle-like structures and measured the distance between the dermatan sulfate-proteoglycan attachment sites at the d-bands of the collagen fibrils in the loose intralobular connective tissue and in the dense interlobular connective tissue. We characterized the dermatan sulfate proteoglycan by enzyme digestion and by immunogold-labeled antibody. In the follicular phase a relatively constant distance of 46 nm between neighboring proteoglycan attachment sites was found, while in the luteal phase the measured distances are strikingly variable and exceed the follicular value by up to 9 nm. This difference of the two cycle phases is more evident in the loose than in the dense connective tissue. Possibly the changes of the fibril-attached proteoglycans in the luteal phase reflect an influence of the higher water content of the matrix leading to a probably torsional swelling of the collagen fibril.

Cell proliferation in bovine mammary epithelium: identification of the primary proliferative cell population

Histologic analyses indicate that a lightly staining cell population present in mammary parenchyma may function as mammary stem cells. We performed an analysis of mammary epithelial cell proliferation in prepubertal bromodeoxyuridine (BrdU)-injected Holstein heifers to investigate this hypothesis. We observed light, dark, and intermediate staining cells in histologic sections stained with basic fuschin and azure II. Light cells comprised 10% of the total parenchymal cell population but accounted for 50% of the cell proliferation. Intermediate cells comprised 60% of the cell population and 43% of proliferating cells. Dark cells comprised 30% of the parenchymal cell population but only 7% of proliferating cells. The distribution of BrdU+ cells across basal, embedded, and lumenal parenchymal cell layers was correlated with the fraction of total parenchymal cells present in each layer (r=0.99). However, the proportion of mitotic cells observed in the basal cell layer was only half of what would be predicted by the BrdU-labeling data. This observation suggests that some basal cells either arrest in G(2) or migrate into the suprabasal epithelial layers before undergoing mitosis. These results strongly support the concept that lightly staining mammary parenchymal cells are the primary proliferative cell population.

Endocytic prolactin routes to the secretory pathway in lactating mammary epithelial cells

Plasma-borne prolactin is carried from blood to milk by transcytosis across the mammary epithelial cell through the endocytic and secretory pathways. To determine the precise route of prolactin endocytosis, intracellular transport of biotinylated prolactin was monitored, in parallel with endocytosis of fluorescein isothiocyanate-conjugated dextran and IgG, by using pulse-chase experiments in lactating mammary fragments and in enzymatically dissociated acini. Biotinylated prolactin was sorted to vesiculo-tubular organelles whereas dextran was very rapidly carried to the lumen and IgG remained accumulated in the basal region of cells. To determine whether prolactin uses routes into and across the Golgi and trans-Golgi network, localisation of biotinylated prolactin was combined with the immunofluorescence detection of caseins and, respectively, p58 and TGN38. Biotinylated prolactin strongly colocalised with caseins during a chase but not all or only very little with p58 and TGN38. To characterise the organelles involved in transcytosis, gold-labelled prolactin, experimentally accumulated in late endosomes and which recovered a normal transport, was localised by electron microscopy. In mammary fragments incubated at low temperature, and in mammary fragments from rats fed with a lipid-deprived diet, transport of gold-labelled prolactin was restored by increasing the temperature and by adding arachidonic acid, respectively. These data demonstrate that a sorting occurs very rapidly between prolactin, dextran and IgG. They suggest that prolactin may reach the biosynthetic pathway after direct fusion between multivesicular bodies and secretory vesicles.

Ultrastructural localization of laminin and type IV collagen in normal human breast

The ability of carcinomas to invade and metastasize depends in part on their passage through basement membranes. Two of the major components of basement membranes are type IV collagen and laminin and these have been extensively studied by light microscopical immunocytochemical techniques to investigate alterations in their distribution in human breast carcinomas [1-3]. Breaks in the epithelial basement membrane associated with malignant epithelial tumors have been reported [3, 4]. However, these breaks are based on immunocytochemical observations and have not been correlated with basement membrane morphology. By light microscopical techniques there is no evidence of type IV collagen or laminin between myoepithelial cells or between myoepithelial and epithelial cells and they appear to be restricted to the basement membrane surrounding the entire ductule of the breast. By electron microscopy the basement membrane region contains a linear, homogeneous, electron-dense region (lamina densa) beneath a clear zone (lamina lucida) directly beneath the epithelial and myoepithelial cells of the breast ductule. These two regions constitute the basal lamina. Hemidesmosomes are present on the basal aspect of myoepithelial cells where fine filaments connect these regions to the adjacent basal lamina. The extracellular matrix components laminin and type IV collagen have both been localized in the basement membrane of the normal human breast ductule. Breaks in the continuity of these components occur in breast carcinomas and have been implicated in tumor metastasis. Using a postembedding ultrastructural immunogold technique, laminin and type IV collagen were distributed within the basal lamina surrounding the normal human breast ductule. Both components were present diffusely along the basal lamina and were not localized to particular regions, and neither were present between epithelial and myoepithelial cells. Laminin binding of these cells thus probably occurs only at the basal aspect where they are in contact with the basal lamina and is not involved in the cell-cell adhesion between epithelial and myoepithelial cells. This study provides a basis for further ultrastructural investigations of extracellular matrix components in normal and neoplastic breast tissue.

Nuclear magnetic resonance-visible lipids induced by cationic lipophilic chemotherapeutic agents are accompanied by increased lipid droplet formation and damaged mitochondria

Proton nuclear magnetic resonance (NMR) spectroscopy, histological lipid staining, and electron microscopy were used to assess the biochemical and structural changes induced by treating the cultured human breast cell line HBL-100 with the cationic lipophilic phosphonium salts p-(triphenylphosphoniummethyl) benzaldehyde chloride (drug A) and [4-(hydrazinocarboxy)-1-butyl] tris-(4-dimethylaminophenyl) phosphonium chloride (drug B). The major biochemical change detected by (1)H NMR in drug-treated cells was a significant time- and concentration-dependent increase in lipid acyl chain resonances arising from mobile lipids. The amount of NMR-visible lipid strongly correlated with morphometric measurements of oil red O-staining lipid detected in the cytoplasm by light microscopy. Ultrastructural investigations revealed substantial damage to mitochondria and the progressive development of lipid droplets accompanied by end-stage autophagic vacuoles, in the form of densely staining myelinoid bodies, after treatment of HBL-100 cells with drug B at the IC(50). No apparent increase in acid phosphatase activity was observed using electron microscopy, indicating that the accumulation of phospholipids in myelinoid bodies may result from substrate inundation of the lysosome, rather than increased lysosomal activity. These results indicate a potential role for lysosomal lipid catabolism in the formation of NMR-visible lipids in models of cytotoxic insult.

Rho regulates p21(CIP1), cyclin D1, and checkpoint control in mammary epithelial cells

The small GTPase Rho is important for cell cycle progression and Ras transformation in fibroblasts. However, it is unclear whether Rho is needed for proliferation in other cell types, and its targets in promoting normal cell cycle progression are unknown. Here, we demonstrate that Rho is required for G1 to S progression in MCF10A mammary epithelial cells, both in response to EGF and in response to oncogenic Ras. We describe two effects of Rho, the repression of p21(CIP1) and the induction of cyclin D1, that may underlie its role in promoting S phase entry. The Rho inhibitor, C3 exotransferase, induced p21(CIP1) both in EGF-stimulated and V12Ras-expressing cells. In addition, C3 blocked EGF-stimulated cyclin D1 promoter activity whereas V14RhoA induced the cyclin D1 promoter and cooperated with V12Ras in cyclin D1 induction. Finally, a high proportion of cells co-expressing V14RhoA and V12Ras displayed lobulated, polyploid nuclei that were actively synthesizing DNA. Our results demonstrate that Rho plays a fundamental role in promoting Ras-dependent S phase entry in mammary epithelial cells, whether in response to normal or oncogenic signaling, and indicate that in cells expressing oncogenic Ras, the activation of Rho diminishes p21(CIP1) expression, increases cyclin D1 promoter activity, and uncouples DNA synthesis from mitosis.

Increased risk of local recurrence is associated with allelic loss in normal lobules of breast cancer patients

Allelic losses characteristic of tumor cells, when displayed by morphologically normal terminal ductal lobular units (TDLUs) adjacent to carcinoma [G. Deng et al., Science (Wash. DC), 274: 2057-2059, 1996], may indicate an extended field of increased cancer susceptibility within the affected breast tissue. We investigated this possibility by asking whether the presence of loss of heterozygosity (LOH) at chromosome 3p11-26 in histologically normal TDLUs (3pLOHn) could lead to an increased risk of local tumor recurrence. We assessed LOHs in normal TDLUs adjacent to 48 informative cases of early-stage invasive breast cancer samples and found 3pLOHn in approximately 25% (13 of 48) of patients whose tumors had 3pLOH in this region. Our analyses suggest that the most frequent region of LOH is localized at 3p24.3. We also demonstrate, using a Cox proportional hazards regression model, that the presence of 3pLOHn was the only variable significantly related to local tumor recurrence, leading to a 3.9-5.2-fold increase in the hazard ratio (P < 0.05). The time to recurrence was longer in such cases than in those without 3pLOHn, suggesting de novo tumor development. These data provide a strong rationale to assess histologically normal breast tissue at the margins of surgically excised cancers for molecular predictors of local recurrence after breast-conserving treatment.

Effects of anabolic implants of oestradiol alone or in combination with trenbolone acetate on the ultrastructure of mammary glands in female lambs regarding their interference in prolactin secretion

The side-effects of anabolic steroid implants on mammary gland ultrastructure were evaluated in female lambs treated with oestradiol (n = 10) and with oestradiol plus trenbolone acetate (n = 10). Ten non-implanted lambs were used as controls. Apart from the ultrastructural study of the mammary gland, an assessment of the prolactin pituitary cell population was carried out by immunological methods. Our results showed that oestrogenic implants exert stimulating effects on mammary gland development, both by activating the synthesis process at mammary gland cell levels and by increasing prolactin pituitary production. Nevertheless, there was no evidence of secretory products in the lumen of the gland. Implants containing trenbolone acetate counteracted the mammary stimulus of oestrogens showing ultrastructural images of cell autolysis and necrosis.

[Ultrastructural stereologic parameters of epithelial cells of alveolar ducts in the pre-and postovulatory female breast]

Stereological characteristics of ductular parenchyma epithelial cells are analysed ultrastructurally on 8 cases of normal breast tissue. Different physiological states have been compared and tahat pre- and postovulatory. Volume density (VV), surface density (SV) and specific surface density (SV/VV) of nuclei and epithelial cells cytoplasm have been stereologically examined and compared. Postovulatory, the volume density (VV) and surface density (SV) of nuclei as well as specific surface density (SV/VV) of epithelial cells cytoplasm are much less, while a volume density (VV) of epithelial cells cytoplasm is greater.

Changes in adhesive properties of epithelial cells during early morphogenesis of the mammary gland

Previous studies have demonstrated that cell adhesion systems are downregulated in epithelial buds at the earliest stages of submandibular gland and hair follicle development, but are restored at subsequent stages. Here it is shown that epithelial cell adhesion systems are also remodeled during early mammary gland development. Immunofluorescence and electron microscopy of the mouse mammary bud demonstrated that cell-cell adhesion systems were hardly detectable, with significant downregulation of expression of desmosomal molecules, but not of E-cadherin and beta-catenin. Hemidesmosomal structures were also rarely found, although their component molecules were expressed. Differences in cell adhesivity between cells of the mammary bud and those of the overlying epidermis were shown by the finding that the mammary cells formed smaller aggregates than the epidermal cells and were not randomly mixed with the epidermal cells. At subsequent stages, the mammary epithelium restored cell-cell adhesion systems along with de novo expression of tight junction molecules. These data, together with previous findings, indicate that remodeling of epithelial cell adhesion systems is a general feature underlying the early development of several ectoderm-derived organs and support the idea that segregation and rearrangements of cells are involved in early epithelial morphogenesis.