Papillary apocrine change of the breast: associations with atypical hyperplasia and risk of breast cancer

Micropapillary patterns of apocrine change in human female breasts are common histological findings. They have been identified as cancer associated and implicated as an indicator of cancer risk in a predictive manner. This study has stratified papillary apocrine change (PAC) into categories of increasing complexity using a combination of cytological and histological pattern rules. Cases (2,876) were identified in a review of 10,357 benign breast biopsies. Of 5966 women, 1613 and PAC and were followed for a median of 20 years after biopsy for the development of invasive carcinoma of the breast. There was a slight association with cancer risk elevation, but most of this disappeared when women with concurrent, specifically identified patterns of atypical hyperplasia (AH) were excluded from the groups with PAC. The resultant relative risk was only 1.2 after women with AH were excluded. Only 1% of the reviewed biopsies demonstrated highly complex patterns of PAC, and 20% of these had coexistent lesions of AH. Women with highly complex patterns of PAC without AH did experience a relative risk of 2.4 (95% confidence interval = 0.77-7.04) but without statistical significance. More than one-half of all PAC patterns occurred without concurrent foci of lesions of proliferative disease that are associated with a slight elevation of breast cancer risk (at least 1.5 times); when present without proliferative disease, there was no suggestion of later breast cancer risk for PAC.

New insights in the molecular mechanism of progestin-induced proliferation of mammary epithelium: induction of the local biosynthesis of growth hormone (GH) in the mammary glands of dogs, cats and humans

In contrast to the protective, anti-proliferative, action of progestins on the development of endometrium cancer, progestins may have local stimulatory and inhibitory effects on the proliferation of mammary epithelium. Until now there was no final molecular explanation of this discrepancy. Prolonged treatment of dogs with depot medroxyprogesterone acetate (DPMA) or with proligestone (PROL) results in enhanced plasma concentrations of growth hormone (GH), insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins, together with the development of benign mammary tumours. The stimulated plasma GH levels do not have the typical pulsatile secretion pattern, and are not sensitive to stimulation with GHRH or to inhibition with somatostatin. The autonomous secretion can be inhibited by the anti-progestin RUU-486. The source of progestin-induced plasma GH levels has been demonstrated to be the canine mammary gland where progestins induce the expression of the gene encoding GH. The expression of the GH gene is restricted to focal areas of hyperplastic epithelium as shown by immunohistochemistry, and is predominantly located in single positive epithelial cells with an intermediate position between luminal- and myo-epithelium. Progestin-induced fibroadenomatous changes in the mammary gland of cats are also associated with locally enhanced GH expression. In both normal, benign and malignant mammary tumours of humans GH mRNA expression has been demonstrated by RT-PCR. The presence of GH mRNA is associated with the presence of immunoreactive GH as shown by immunohistochemistry. Sequence analysis revealed 100% homology to the pituitary expressed GH gene. In malignant mammary tumours of humans and dogs GH expression is also found in specimens negative for progesterone receptors as measured by ligand binding. It is concluded that the gene encoding GH is expressed in the mammary gland of a variety of species, including man. This appears to represent a contribution to the molecular explanation of the action of progestins on proliferation of mammary epithelium. It needs, however, to be proven whether this local biosynthesis of GH in the mammary gland is the cause of the local stimulatory effect of progestins on the proliferation of mammary epithelium.

Mammary Paget's disease confined to the areola and associated with multifocal Toker cell hyperplasia

A hitherto unreported variant of mammary Paget's disease (MPD) limited to the areola, leaving the nipple unaffected, has been analyzed by serial sectioning of the whole areola and nipple. This otherwise characteristic MPD proved to be confined to the epidermis. There was no underlying carcinoma. This MPD was associated with a multifocal presence of monomorphic but otherwise similar cells in small collections surrounding the ostia of areolar mammary glands in the clinically unaffected area. This condition was interpreted as hyperplasia of mammary gland-related cells also found in normal nipples (so-called Toker cells). The observations hint at a possible derivation of some cases of mammary and extramammary Paget's disease from such Toker cells.

Effects of cell cycle, wild-type p53 and DNA damage on p21CIP1/Waf1 expression in human breast epithelial cells

In this study we examine the relationship between p21CIP1/Waf1 (CIP1), a 21 kDa protein that binds to and modulates the activity of several cyclin dependent kinases and expression of wild-type (WT) p53 in human breast epithelial cells. Basal CIP1 protein, but not CIP1 mRNA levels correlated well with expression of WT p53 in human breast epithelial cells. To obtain more direct evidence that WT p53 regulated the level of CIP1 protein, the Human Papilloma Virus (HPV) E6 protein was introduced into immortalized 184B5 breast cells. Residual WT p53 levels correlated well with CIP1 protein but not CIP1 mRNA levels in isolated clones of transfected cells. CIP1 protein was increased at early times after growth factor arrested cells were stimulated to proliferate. The rise in CIP1 protein was due to a concomitant increase in CIP1 mRNA levels in MCF10, but not in normal mammary epithelial cells. DNA damage induced by ionizing radiation resulted in a transient increase in WT p53 levels but a prolonged induction of CIP1 protein. The sustained increase in CIP1 protein 24 h after radiation could not be attributed to a concomitant increase in CIP1 mRNA levels. Although the half-life of the CIP1 protein was not altered following irradiation, a fourfold increase in the amount of radioactivity incorporated into CIP1 protein was detected. When considered together these data suggest that wild-type p53 affects CIP1 protein accumulation at a posttranscriptional level in human breast epithelial cells under different physiologic and stress conditions.

Ultrastructural and immunohistochemical observations on intralobular fibroblasts of human breast, with observations on the CD34 antigen

Understanding the diverse pathological processes which are initiated in the ultimate organizational units of the mammary parenchyma--the lobules and ductules--will to a large extent be based on understanding the normal breast. During the routine diagnostic evaluation of 11 surgical specimens for a variety of benign and malignant breast lesions, grossly normal mammary parenchyma, subsequently confirmed as histologically normal by light microscopy, was sampled for this purpose. Tissue was studied by histology, light microscope immunohistochemistry, transmission electron microscopy, scanning electron microscopy, and ultrastructural immunohistochemistry. A number of features hitherto disregarded in the literature are described in detail, or are elaborated with respect to earlier descriptions. These include: the presence of solitary cilia and lipid-rich residual bodies in intralobular fibroblasts, and the frequent association of inflammatory cells (lymphocytes, plasma cells, macrophages, mast cells) with the cell bodies and processes of fibroblasts. For the first time also, CD34, best known as an endothelial cell marker, has been demonstrated by ultrastructural immunohistochemistry on the cell surface of fibroblasts. Finally, scanning electron microscopy has demonstrated new features of the intercellular matrix in which the fibroblasts and inflammatory cells are located. The significance of these findings is discussed in terms of a postulated immune surveillance role of the mononuclear cells in collaboration with the fibroblasts.

Expression and ligand binding of alpha 2 beta 1 integrin on breast carcinoma cells

We examined the expression and ligand specificity of the alpha 2 beta 1 integrin on human mammary epithelial cells (HMEC) and a panel of breast carcinoma cell lines in vitro. We found that the alpha 2 beta 1 integrin was universally, but quite variably expressed on these cells by FACS analysis. No significant correlation was observed between its expression and other known cellular phenotypes. Substrate attachment assays using blocking antibodies demonstrated that alpha 2 beta 1 integrin served as a receptor for collagen on HMEC and almost all breast carcinoma cells. However, its contribution to laminin binding of these cells appeared to be related to cellular differentiation as evaluated by sex steroid receptor status and by markers of epithelial-mesenchymal transition, i.e. loss of E-cadherin and expression of vimentin. Two different populations of non-malignant immortalized HMEC (184A1N4 and MCF-10A) contained cells capable of using alpha 2 beta 1 integrin as a laminin receptor. Breast cancer cell lines positive for estrogen receptor (ER) and E-cadherin (MCF-7, T47D, ZR75-1) could also use alpha 2 beta 1 integrin as a laminin receptor. Conversely, alpha 2 beta 1 integrin appeared to be incapable of binding to laminin or to be a very minor receptor for laminin on metastatic ER-negative breast carcinoma cells that expressed vimentin (MDA-MB 231, MDA-MB 435, and MDA-MB 436). These findings suggest that the ligand specificity of alpha 2 beta 1 integrin, i.e. its function as a laminin receptor, may be regulated during the malignant progression of breast carcinoma cells. A reduced contribution of alpha 2 beta 1 integrin to the cellular laminin binding appears to be associated with an increased malignant phenotype and with an epithelial-mesenchymal transition of breast carcinoma cells.

Analysis of MTS1/CDK4 in female breast carcinomas

Multiple factors, both environmental and genetic, are thought to play roles in breast carcinogenesis. The recently cloned multiple tumor suppressor gene (MTS1), the product of which interacts with CDK4 to regulate cell growth, has been found to be mutated with high frequency in a variety of cell lines as well as primary tumors of different histologic types. Using PCR-SSCP, we analyzed exons one (126 bp) and two (307 bp) of the MTS1 gene to determine the incidence of mutation in a population of 50 primary breast adenocarcinomas and corresponding normal tissue. Analysis of five breast tumor cell lines was also performed. We found no mutations in the MTS1 gene in the primary breast tumor samples. One cell line was found to have a homozygous deletion of the gene. Our results suggest that the MTS1 gene is not mutated with increased frequency in primary breast tumors, and thus may not play a major role in breast carcinogenesis.

bFGF and aFGF induce membrane ruffling in breast cancer cells but not in normal breast epithelial cells: FGFR-4 involvement

Acidic and basic fibroblast growth factors (aFGF and bFGF) are growth factors which may have a physiological role in the normal breast and in breast cancer. A study of the effects of aFGF and bFGF on a variety of breast cell lines and epithelial cells purified from normal breast organoids showed that whereas normal breast cells did not exhibit membrane ruffling in response to either of these growth factors, some breast cancer cell lines did. This difference was not due to lack of receptor since all the cell lines tested were mitogenically stimulated by bFGF. Dominant negative mutations of FGF receptor 3 (FGFR-3) and the small GTP-binding protein p21rac inhibited membrane ruffling, showing that receptor dimerization and phosphorylation and p21rac activation are prerequisites for membrane ruffling in response to aFGF and bFGF. Transient transfection of individual FGFRs into cos-7 cells showed that FGFR-1, FGFR-2 and FGFR-3 could not mediate a membrane ruffling response whereas FGFR-4 could. These studies elucidate one signalling mechanism of FGF and point to differences in the response of normal and cancer breast epithelial cells which may be important in cell motility.

Electron-microscopic cytochemical localization of adenylate cyclase activity in the myoepithelial cells of the lactating mouse mammary gland

Adenylate cyclase activity was localized in the lactating mouse mammary gland using an ultrastructural histochemical technique. Reaction product was deposited on the plasma membrane of the myoepithelial cells adjacent to the secretory epithelium. No reaction product was encountered on the secretory epithelium. These findings suggest that the presence of cAMP, previously biochemically documented in lactating mammary gland, is mainly connected with myoepithelial cellular activity. The asymmetrical distribution of adenylate cyclase activity suggests that cAMP is involved in the intercellular communication between the secretory and myoepithelial cells and that the secretory epithelium takes part in the regulation of the contraction of myoepithelial cells.

Malignancy-associated changes in the breast. Changes in chromatin distribution in epithelial cells in normal-appearing tissue adjacent to carcinoma

Malignancy-associated changes (MACs) have been described as subtle morphologic changes in normal-appearing tissues adjacent to or distant from malignant tumors. MACs might be applicable as a marker of occult malignancy, increased risk of subsequent carcinoma or recurrence of tumor after therapy. The aim of this study was to verify the existence of MACs in normal-appearing breast tissue adjacent to breast carcinoma. Image cytometry measurements were performed on 4-microns sections cut from formaldehyde-fixed tissue blocks and stained with thionin-SO2 following the Feulgen procedure. Morphologically normal appearing breast lobules were analyzed in patients with benign (20 cases) and malignant breast disease (23 invasive and 11 in situ tumors). The chromatin distribution features of the epithelial nuclei in normal-appearing breast lobules differed between patients with benign and malignant breast disease. Changes in nuclear features, detected in epithelial nuclei from normal-appearing lobules in breasts resected for carcinoma, were defined as MACs. The frequency of MAC nuclei was low in benign tissues, increased in tissues with ductal carcinoma in situ and highest in tissues with invasive carcinoma. Based on the measurements of nuclei in normal-appearing lobules, it was possible to discriminate between patients with benign breast disease and patients with invasive carcinoma in 86% of cases.

Chromosome abnormalities in benign hyperproliferative disorders of epithelial and stromal breast tissue

Cytogenetic analysis of short-term cultures from 15 cases of benign proliferative breast disease (PBD), 10 diffuse PBD and 5 papillomas, and 15 fibroadenomas of the breast revealed clonal chromosome abnormalities in 7 diffuse PBD lesions, 4 papillomas and 5 fibroadenomas. The remaining 14 cases had a normal female chromosome complement. Cytogenetically unrelated abnormal clones were seen in 4 fibroadenomas and 2 PBDs. A single abnormal clone was found in 9 PBDs and 1 fibroadenoma. Three clonal abnormalities were seen as recurrent changes in 6 cases, namely interstitial deletions of 3p with 3p 12-14 as the minimally common deleted segment (in 1 papilloma, 1 diffuse PBD with atypia and 1 mixed-pattern lesion with both papilloma and atypical diffuse PBD features), r(9)(p24q34) (in 1 diffuse PBD and 1 fibroadenoma), and del(1)(q12)(again in 1 diffuse PBD and 1 fibroadenoma). Intriguingly, 6 of the 16 abnormal cases had chromosome changes that have been seen repeatedly as primary abnormalities in breast carcinomas: der(16)t(1;16)(q10;p10), del(3)(p12p14), and del(1)(q12). We conclude that some of the chromosome anomalies frequently found in breast carcinomas are also present in PBD and fibroadenomas. These aberrations may be accepted as early, neoplasia-relevant mutations. However, they do not seem to be sufficient by themselves to unleash a malignant process.

Ultrastructure and immunohistochemistry of the embryonic type of fat identified in the human infant breast

In this paper we describe the light and electron microscopic appearance of the embryonic type of fat in human infant breast, together with immunocytochemical findings. This fat tissue was composed of numerous capillaries surrounded by a mixed population of undifferentiated mesenchymal cells and preadipocytes at various stages of differentiation. The preadipocytes were characterised by a number of cytoplasmic processes, varying numbers of lipid droplets, and an envelope of electrondense material outside the cell membrane. Immunocytochemistry showed a characteristic distribution of collagen type IV adjacent to and vimentin and S100 protein within the preadipocytes. This is the first report of the ultrastructure of the human mammary embryonic type of fat. The possible role of the embryonic type of fat in the development and growth of the human breast is discussed.

Individual differences between nuclear parameters of normal and malignant breast epithelium

This study attempts to estimate the status of estrogen and progesterone receptors (ER and PR) in tissue of invasive breast carcinoma. Identical stereologic parameters of nuclear ultrastructure, of normal and malignant epithelium in the same breast were compared. Samples of normal and malignant epithelium of 30 surgically amputated breasts were analysed morphometrically. The concentration of ER and PR in the malignant epithelium was estimated by means of the dextran-coated charcoal (DCC) method. We measured the mean nuclear area (A), nuclear specific density (Sv/Vv) and nuclear numerical density (Nv) of epithelium. The comparison of such models of normal and malignant epithelium nuclear ultrastructure of the same breast demonstrated: a) the difference between Sv/Vv of nuclei very sensitively and specifically marks the ER status in malignant tissue (overall efficiency = 80%, p < 0.01), and b) the difference between A, Sv/Vv and Nv marks the concordant ER and PR status with identical overall efficiency. Minimal individual differences in size, surface structure and shape, observed between nuclei of malignant epithelium of positive concordant ER and PR status and nuclei of normal epithelium demonstrated that the highest morphological similarity is associated with biochemical similarity of cells exposed to the identical media of steroid hormones.

Differentiation of breast cancer cells in vitro is promoted by the concurrent influence of myoepithelial cells and relaxin

Our previous studies showed that relaxin promotes differentiation of MCF-7 breast adenocarcinoma cells. In the current investigation, we aimed to elucidate whether the effect of the hormone is potentiated when MCF-7 cells are grown together with myoepithelial cells, thus creating a microenvironment reminiscent of the organised tissue architecture of the mammary parenchyma in vivo. The findings obtained reveal that most MCF-7 cells cultured alone have an undifferentiated, blast-like phenotype, only a minority showing a more differentiated phenotype with more organelles and rudimentary intercellular junctions. When co-cultured with myoepithelial cells more MCF-7 cells acquire ultrastructural features consistent with a more differentiated phenotype, such as a rich organellular complement, apical microvilli and intercellular junctions. When relaxin was added to the co-cultures, the ultrastructural signs of differentiation could be observed in even more MCF-7 cells and became more pronounced than in the absence of the hormone, judged by the appearance of a clear-cut polarisation of cytoplasmic organelles, an almost continuous coat of apical microvilli and numerous intracellular pseudolumina.

Quantitative study of the lysosomes of epithelial cells from human mammary glands and fibroadenoma during proliferative and secretory phase of the menstrual cycle

The cyclic lysosome number variation in fibroadenoma and normal breast epithelial cells in 13 women, using light microscopy and Gomory acid phosphatase method, was studied. The menstrual cycle phase was determined by the last menstrual period, plasmatic progesterone level and endometrium biopsy. Seven lumps were extirpated in the proliferative phase and other 7 in the secretory period. The lysosomes were counted in the fibroadenoma and the normal breast epithelia. The statistical analysis of the findings showed that both fibroadenoma and normal breast epithelia present a number of lysosomes statistically higher in proliferative than in the secretory phase. It was also noted that the number of lysosomes in fibroadenomas is always greater than in the normal breast, independently of the phase of the menstrual cycle.

Differential expression of estrogen, progesterone, and epidermal growth factor receptors in normal, benign, and malignant human breast tissues using dual staining immunohistochemistry

Distribution of estrogen (ER), progesterone (PR) receptors, and epidermal growth factor (EGF) receptors was assayed by dual staining immunohistochemistry on 28 selected cytosolic ER-positive breast carcinomas and 22 nonmalignant breast tissues. ER-positive tumor cells were detected in 26 (93%) and EGF receptor positive tumor cells were detected in 7 (25%) carcinomas. In five tumors both ER and EGF receptors were detected but localized in distinct tumor cells. Only in one case of ductal carcinoma in situ co-expression was observed in a subset of tumor cells. In contrast, simultaneous expression of ER/PR and EGF receptors was observed in non-neoplastic ductal remnants in the majority of the carcinomas and the fibroadenomas. In addition, double-positive cells were occasionally detected in luminal epithelial cells of normal breast tissue and mastopathies. This study shows that ER/PR and EGF receptors in breast tumor cells are inversely related at the single cell level. However, demonstration of ER/PR and EGF receptors in individual normal luminal cells shows that expression is not mutually exclusive.

Desogestrel versus gestodene in oral contraceptives: influence on the clinical and histomorphological features of benign breast disease

Forty-four female volunteers asking for oral contraception, affected by symptomatic benign breast disease (BBD) were evaluated to compare the effects on mastalgia and breast nodularity of two different low dose oral contraceptives (OCs), containing 20 micrograms [corrected] ethinylestradiol + 150 micrograms desogestrel (EE+D) and 30 micrograms ethinylestradiol + 75 micrograms gestodene (EE+G), respectively. Physical examination, bilateral thermography, X-ray and/or ultrasonography of breast, and needle and screw-needle biopsies of mammary tissue were performed in all patients before OCs administration and after six cycles of treatment. OCs administration caused an overall improvement of mastalgia in 53%. Breast nodularity improved only in 8% of patients in both groups. Epithelial tissue modifications in mammary biopsies were observed, with involutive and/or secretory histomorphological and ultrastructural changes, frequently coexisting in different areas of the same breast.

Morphological and ultrastructural aspects of the cyclical changes of human mammary gland during the menstrual cycle

Analyzing the morphological and ultrastructural features of the mammary gland during the menstrual cycle, the authors observed that in the proliferative phase, the mammary gland consisted of few developed lobules and presented a relative absence of mitotic figures. In this phase, the great majority of the epithelial cells contained small, dark, irregular, rich heterochromatinic nuclei. The mammary stroma showed similar findings, presenting dense connective tissue with few enhanced fibroblasts. During the secretory phase, the lobules were well developed and mitotic figures were usually observed. In this phase, the great majority of the epithelial cells presented clear voluminous, rich euchromatinic nuclei; the stroma consisted of fibroblasts with voluminous nuclei full of euchromatin. There are evident modifications of the mammary tissue according to the phase of the menstrual cycle. The morphological and ultrastructural modifications indicate higher metabolical and mitotic activities during the secretory phase.

Histological assessment of fifty breast capsules from smooth and textured augmentation and reconstruction mammoplasty prostheses with emphasis on the role of synovial metaplasia

Fifty breast capsules surrounding smooth and textured breast prostheses were reviewed histologically, immunohistochemically, and ultrastructurally, and findings correlated with patient data. The histology of the capsules varied; although most consisted of a simple fibrocollagenous membrane, some were lined by organized, round to polyhedral cells similar to synovium. Histologically, the lining of the synovial type consisted of epithelioid cells overlying parallel bands of collagen, with basally located nuclei and cytoplasmic processes directed toward the surface and arranged within a well developed reticulin network. Immunohistochemically, the cells were vimentin positive, weakly positive focally for alpha-1-antitrypsin, alpha-antichymotrypsin, and lysozyme, and negative for EMA and AE1/AE3. Scanning electron photomicrographs showed a bosselated luminal lining overlying parallel bands of collagen. By transmission electron microscopy, both secretory and phagocytic cells could be distinguished. Some of the former were multinucleated. No basement membrane material could be identified, and cell junctions were rare. Histologically, immunohistochemically, and ultrastructurally the lining appeared identical to synovium and to the synovial metaplasia that has been described in sutured skin, after repeated subcutaneous injections of air, the bone-cement interface of loose hip prostheses and adjacent to gliding silastic tendon reconstruction rods. The physical and chemical composition of the prostheses, the mechanical forces, and the developmental response of the host mesenchymal tissue are thought to influence the formation and maintenance of the synovial metaplasia of the breast capsule.

Immunohistochemical staining patterns of type VI collagen in the normal, hyperplastic, and neoplastic adult male breast

Ten cases of primary invasive male breast ductal carcinomas (N.O.S.), one case of male breast fibroadenoma, seven cases of pure florid gynecomastia and four cases of normal mammary glands were examined immunohistochemically for type VI collagen expression and distribution. In normal male breast type VI collagen was absent in the whole fibrous stroma. On the contrary this collagen was markedly expressed in the stroma of invasive carcinoma as well as fibroadenoma and gynecomastia. In all these proliferative diseases, type VI collagen gave a distinct basement membrane-like deposition at the epithelial-stromal junctions while organized a fibrillar network in the interstitium. Our immunohistochemical findings showed that type VI collagens is involved in the stromal response of benign and malignant male breast proliferative diseases.

Nucleolus organizer regions (AgNORs) in ductal mammary carcinoma. Comparison with classifications and prognosis

The relevance of silver-stained NORs for classifications and prognosis was investigated in breast tissue. Paraffin sections from 137 cases of invasive ductal breast carcinomas and 12 cases with non-tumorous ductus epithelium as controls were stained according to a modified technique and analysed. From the cancer cases follow-up data up to 10 years (45 to 165 months) and in addition clinical, histological and several DNA distribution parameters were available. The nuclei and the silver grains were measured by means of a semiautomatic image analysis system. Significant differences in AgNOR features were found between controls and diploid tumors (p < or = 0.001), diploid and aneuploid tumors (p < or = 0.001), Bloom-Richardson-gradings I, II, and III (p < or = 0.001), and between the tumor cells from patients developing metastases within 5 years and those without (p < or = 0.002). The prognostic significance of AgNORs was estimated using Cox regression analysis. Four AgNOR features were correlated significantly with survival time. In a multivariate approach offering all parameters available an AgNOR parameter (CV of relative area AgNORs) ranked at the third position beyond the SD of DNA distribution and pTNM-staging. Considering the metastases-free interval of patients the same AgNOR feature showed an independent prognostic validity.

bcl-2 in normal human breast and carcinoma, association with oestrogen receptor-positive, epidermal growth factor receptor-negative tumours and in situ cancer

The role of bcl-2 expression in solid tumours is as yet undefined. It was, therefore, the purpose of this study to investigate expression of bcl-2 protein in 111 human breast carcinomas using immunohistochemistry and the monoclonal antibody bcl-2 124. Expression was then compared with the established indicators of prognosis and biological behaviour in malignant breast disease. No relationship could be observed between bcl-2 and node status, tumour size, differentiation, type or age at excision. However, a strong positive relationship was seen between bcl-2 and oestrogen receptor (ER), with 70 of 88 (80%) bcl-2-positive tumours being ER positive also, compared with seven of 23 (30%) bcl-2-negative tumours being ER positive (P < 0.0001). The converse was found when bcl-2 was compared with epidermal growth factor receptor (EGFR). A strong negative relationship was observed, with 26 of 88 (30%) bcl-2-positive tumours being EGFR positive, compared with 16 of 23 (70%) bcl-2-negative tumours being EGFR positive (P = 0.001), raising the possibility that bcl-2 is an ER-regulated gene. An inverse relationship was also found between bcl-2 and the oncogenes c-erbB-2 and p53. Thus, loss of bcl-2 expression in breast cancer is associated with a range of molecular markers of poor prognosis and may define part of an ER-negative, EGFR-positive phenotype.

Endocytosis of desmosomal plaques depends on intact actin filaments and leads to a nondegradative compartment

Epithelial cells in situ can internalize their desmosomes. This can be induced in cell cultures after removal of calcium ions from the cell medium. To study this endocytic process, a nontumorigenic human breast epithelial cell line, HMT-3522, was used. HMT-3522 cells were grown in serum-free, chemically defined medium, containing epidermal growth factor (EGF). Removal of EGF from the medium led to growth arrest and a kind of epithelial differentiation process in which adjacent cells interdigitated and formed more desmosomes than in the proliferating state. Growth-inhibited HMT-3522 cells dissociated following EGTA treatment, the desmosomes divided in a symmetrical fashion, and the desmosomal plaques (half-desmosomes) on the cell surface became internalized. The internalization was independent of clathrin, since immunogold labeling of ultracryosections never showed clathrin on desmosomal plaque-associated membrane domains. Moreover, cytosol acidification, which selectively inhibits endocytosis from clathrin-coated pits, practically blocked the uptake of transferrin, whereas internalization of desmosomal plaques continued. In contrast, actin filaments appeared to be involved in the desmosomal internalization. Thus, depolymerization of actin filaments by cytochalasin D significantly reduced endocytosis of half-desmosomes. Immunogold labeling showed that the vesicles with desmosomal plaques were not enriched in MPR (cation-independent mannose-6-phosphate receptor), cathepsin D or the lysosome-associated membrane protein lamp-1. In addition, the morphology was different. Thus, the endocytic vesicles with desmosomal plaques represent a special compartment, distinct from typical endosomes and lysosomes.

Effect of modification of carbohydrate side chains on the reactivity of antibodies with core-protein epitopes of the MUC1 gene product

The product of the MUC1 gene, the polymorphic epithelial mucin (PEM), contains a large domain consisting of tandem repeats of 20 amino acids. Each repeat contains five potential sites for O-glycosylation, suggesting that this region forms a scaffold for the attachment of the O-linked carbohydrate which makes up more than 50% of the molecule. A number of monoclonal antibodies have been shown to recognize core-protein epitopes within the tandem repeat domain. One such antibody, SM3, reacts with the mucin expressed by breast carcinomas but shows little or no reaction with normal resting or lactating breast. Using primary mammary epithelial cells (HuME), an immortalized cell line derived from HuME (MTSV1-7) and a breast carcinoma cell line (BT20) the influence of the carbohydrate side chains on the binding of antibodies to core-protein epitopes has been investigated. We unequivocally show that the masking of the SM3 epitopes in normal breast epithelial cells is due to the carbohydrate side chains. In addition we demonstrate that the binding of two other antibodies (HMFG1, HMFG2) to core-protein epitopes is influenced by the carbohydrate side chains. The binding of HMFG-1 is particularly affected by sialic acid whereas the binding of HMFG2 is influenced by the length of the oligosaccharide side chains. Furthermore, inhibited elongation of O-linked carbohydrate side chains does not seem to interfere with the cell trafficking of the mucin to the cell surface.