Selective immortalization of a phenotypically distinct epithelial cell type by microinjection of SV40 DNA into cultured human milk cells

Neoplastic transformation of human breast epithelial cells by estrogens and chemical carcinogens

Sporadic breast cancer, the most common cancer diagnosed in American and Northern European women, is gradually increasing in incidence in most Western countries. Prevention would be the most efficient way of eradicating this disease. This goal, however, cannot be accomplished until the specific agent(s) or mechanisms that initiate the neoplastic process are identified. Experimental studies have demonstrated that mammary cancer is a hormone-dependent multistep process that can be induced by a variety of compounds and mechanisms, that is, hormones, chemicals, radiation, and viruses, in addition to or in combination with genetic factors. Although estrogens have been shown to play a central role in breast cancer development, their carcinogenicity on human breast epithelial cells (HBECs) has not yet been clearly demonstrated. Breast cancer initiates in the undifferentiated lobules type 1, which are composed of three cell types: highly proliferating cells that are estrogen-receptor negative (ER-), nonproliferating cells that are ER positive (ER+), and very few (<1%) ER+ cells that proliferate. Interestingly, endogenous 17beta-estradiol (E(2)) is metabolized by the cytochrome P450 enzyme isoforms CYP1A1 and CYP1B1, which also activate benzo[a]pyrene (B[a]P), a carcinogen contained in cigarette smoke. We postulate that if estrogens are carcinogenic in HBECs, they should induce the same transformation phenotypes induced by chemical carcinogens and ultimately genomic changes observed in spontaneously developing primary breast cancers. To test this hypothesis we compared the transforming potential of E(2) on the HBEC MCF-10F with that of B[a]P. Both E(2) and B[a]P induced anchorage-independent growth, colony formation in agar methocel, and loss of ductulogenic capacity in collagen gel, all parameters indicative of cell transformation. In addition, the DNA of E(2)-transformed cells expressed LOH in chromosome 11 at 11q23.3, 11q24.2-q25, and LOH at 13q12-q13. B[a]P-induced cell transformation was also associated with LOH at 13q12-q13 and at 17p13.2. The relevance of these findings is highlighted by the observation that E(2)- and B[a]P-induced genomic alterations in the same loci found in ductal hyperplasia, ductal carcinoma in situ, and invasive ductal carcinoma of the breast.

Cell cycle arrest and induction of apoptosis by beta galactoside binding protein (beta GBP) in human mammary cancer cells. A potential new approach to cancer control

Conflict between mitogenic pressure, as is the case in tumour cells and an imposed inability to proceed through the cell cycle may result in cell death. In the present study we examined the effect of beta galactoside binding protein (beta GBP), a negative growth factor which controls cell cycle transition from S phase into G2, on three human mammary cell lines which differ for oncogenic potential, oestrogen receptor expression and expression of the EGF receptor family. We found that in all cases beta GBP induced a cell cycle block prior to the cells' entry into G2 and that this was followed by progressive apoptotic death. This evidence on epithelial cancer cells parallels previous data on tumour cells of mesenchymal origin and suggests that beta GBP has potential therapeutic implications in the treatment of cancers.

The development of epithelial phenotypes in the human fetal and infant breast

In order to explain the molecular events that contribute to benign and malignant breast disease, it is essential to understand the cellular context in which these are occurring. This study describes a detailed analysis of the epithelial phenotypes in the human fetal and infant breast and provides a starting point for such consideration. Using methacarn-fixed, paraffin sections from ten fetal and 45 infant breast, immunostained with a panel of antibodies to cytoskeletal proteins and kappa-casein, it has been possible to define in detail the chronological evolution of the major cell types in the human breast from 16 weeks of intrauterine life to 2 years of age, in both sexes. Cells at the tips of the lobular buds and terminal end buds have a characteristic cytoskeletal protein profile, suggesting that they may have the capacity to generate both basal cells and luminal cells. Based on the expression of cytoskeletal proteins in the developing fetal and infant breast, a model system has been proposed for mammary epithelial differentiation.

Growth requirements and neoplastic transformation of two types of normal human breast epithelial cells derived from reduction mammoplasty

A chemically defined culture medium was developed to support the growth of two distinctly different types of normal human breast epithelial cells (HBEC) derived from reduction mammoplasty. Type I cells expressed luminal epithelial cell markers and were deficient in gap junctional intercellular communication (GJIC), whereas Type II cells expressed basal epithelial cell markers and were efficient in GJIC. In this study, we examined and compared the growth factor and hormone requirements of these two types of cells and a series of cell lines that were obtained by sequential transfection with SV40 DNA (extended lifespan, nontumorigenic), treatment with 5-bromodeoxyuridine (BrdU)/black light (immortal and weakly tumorigenic), and infection of a virus carrying the neu oncogene (highly tumorigenic). Growth of Type I cells was inhibited by withdrawing epidermal growth factor (EGF), hydrocortisone (HC), or insulin (INS) from the culture media, but was enhanced by fetal bovine serum (FBS) supplementation. Growth of Type II cells was inhibited by withdrawal of EGF, HC, or INS from the media, and was inhibited by FBS supplementation. Withdrawal of human transferrin (HT) or 17 beta-estradiol (E2) from the media did not alter the growth of Type I or Type II cells. SV40 transfected Type I cell lines still required EGF, HC, or INS for optimal growth. However, the highly tumorigenic cell line did not show a growth dependence on EGF, HC, or INS but did appear to require HT and 3,3',5-triiodo-D.L. thyronine (T3) for optimal growth. In addition, FBS stimulated the growth of these cell lines. Thus, this study shows that Type I HBEC are distinctly different from Type II HBEC in growth response to FBS and that neoplastically transformed Type I cells could become growth factor and hormone independent.

Establishment and characterisation of two cell lines derived from a primary adenocarcinoma of the duodenum

Aims-To establish two cell lines from a primary duodenal adenocarcinoma; to describe the morphological, growth, ploidy, and immunophenotypic characteristics of these cell lines.Methods-The cell lines, designated DAC/S and DAC/E, were characterised using both in vitro and in vivo cell culture techniques, light and electron microscopy, immunocytochemistry, and FACS analyses.Results-Both cell lines have an epithelial origin, are aneuploid and display characteristics of transformed cells. The cell lines differ from each other in morphology, doubling time and serum requirements. These cell lines are anchorage dependent and do not grow in nude mice.Conclusions-DAC/S and DAC/E cell lines are derived from neoplastic epithelium and could provide in vitro model systems for future investigations of the cell and molecular biology of duodenal neoplasia.

Cyclin D1 protein expression and function in human breast cancer

Cyclin D1 is a cell-cycle regulator essential for G1 phase progression and a candidate proto-oncogene implicated in pathogenesis of several human tumour types, including breast carcinomas. In spite of the accumulating genetic evidence, however, there are no data regarding abundance and properties of the cyclin D1 protein in breast cancer. We now report aberrant nuclear overexpression/accumulation of the cyclin D1 protein in about half of the 170 primary breast carcinoma specimens analyzed by monoclonal antibody immunohistochemistry, indicating that the frequency of cyclin D1 abnormalities may be considerably higher than previously deduced from DNA amplification studies. A comparison of the expression patterns in matched lesions at different stages of tumour progression revealed that the cyclin D1 protein aberration appears to reflect a relatively early event and that, when acquired by a tumour, it is maintained throughout breast cancer progression including metastatic spread. In both tumour tissues and breast cancer cell lines, the abundance of this protein shows characteristic variations consistent with a cell-cycle oscillation and the peak levels expressed in G1. In all 7 cell lines whose retinoblastoma (Rb) protein is mutant or complexed to SV40 T antigen, exceptionally low levels of cyclin D1 protein and mRNA were found. Antibody-mediated and anti-sense oligonucleotide knockout experiments demonstrate the requirement for the cell-cycle regulatory function of cyclin D1 in breast cancer lines with single or multiple copies of the gene and reveal the absence of such a requirement in the cell lines with Rb defects. Our data are consistent with the notion that the emerging "Rb-cyclin D1 pathway" represents a frequent target of oncogenic abnormalities in breast cancer.

Cell cycle-related variation and tissue-restricted expression of human cyclin D1 protein

Recent evidence from genetic studies suggests that abnormalities of some of the members of the cyclin superfamily may be intimately associated with tumourigenesis, most likely through deregulation of the cell cycle control. In an attempt to elucidate the potential role of cyclin D1 (a gene located within the 11q13 amplicon and a candidate BCL-1, PRAD-1 oncogene) in the pathogenesis of human neoplasias, we have developed and characterized a novel monoclonal antibody specifically recognizing cyclin D1 protein in various assays including immunohistochemistry on frozen and paraffin sections. Using the DCS-6 antibody as a tool, we now show a characteristic cell cycle-dependent variation of the cyclin D1 protein in human cultured cells and report on the first immunohistochemical study of this G1 cyclin in a range of normal human tissues and breast carcinomas. Analysis of normal tissues revealed generally low levels of cyclin D1 protein, mainly restricted to the proliferative zones of some epithelial tissues, and the lack of its expression in several human tissues including lymph nodes, spleen, and tonsils. In contrast, pronounced overexpression/nuclear accumulation of cyclin D1 was found in 37 per cent of cases in a series of 35 primary ductal carcinomas of the breast. We conclude that the DCS-6 antibody provides a potentially useful tool for the establishment of simple methods suitable for verifying any diagnostic and/or prognostic value of this novel marker on large series of histological specimens and opens the way for biochemical, immunocytochemical, and immunohistochemical studies of the role played by cyclin D1 aberrations in human oncogenesis.

Molecular biology of breast cancer

BACKGROUND

A gene responsible for an inherited predisposition to breast and ovarian cancer has been localized to the long arm of chromosome 17 and termed BRCA1. As well as being closely linked to breast/ovarian cancer cases, this gene may be involved in up to 45% of site-specific breast cancers. The identification and cloning of the BRCA1 gene is imminent, and will facilitate the screening and counselling of families at risk of breast cancer, and in the longer term may open up new therapeutic possibilities. The tumour suppressor gene TP53 is mutated in 25%-40% of cases of sporadic breast cancer, and is associated with an aggressive tumour phenotype and poor prognosis in both node-positive and node-negative cases. The pattern of mutations in this tumour suppressor gene shows a higher than expected frequency of G to T transversions, mostly restricted to the highly conserved domain in exons 5 to 8. In many, but not all cases, point mutation of one allele is accompanied by deletion of the remaining normal allele at chromosome 17p13. Abnormalities of TP53 appear to be relatively early events in tumorigenesis, being present in ductal carcinoma in situ lesions. The retinoblastoma gene RB1 shows a variety of abnormalities in about 20% of breast cancers, and there may be an association with TP53 mutations. Other abnormalities which occur with a particularly high incidence in breast cancer include allele loss at chromosome 1p/1q, 3p, 6q, 11p, 16q and 18q. The ERBB2 oncogene encodes a transmembrane receptor tyrosine kinase whose ligand has recently been claimed to be the heregulin family in man.(ABSTRACT TRUNCATED AT 250 WORDS)

Malignant progression of SV40-immortalised human milk epithelial cells

A human breast epithelial cell line (Hu-MI), established by microinjecting SV40 DNA into human milk epithelial cells, exhibits the phenotype of luminal epithelial cells and is neither clonogenic nor tumorigenic. From this cell line we have selected two sublines, HuMI-T and HuMI-TTul, reflecting different stages of spontaneous transformation. HuMI-T cells grow anchorage-independently, but do not induce tumours in nude mice. HuMI-TTul cells are clonogenic as well as tumorigenic. Cells from both lines exhibit polymorphic structural and numerical chromosome aberrations. Immortalisation of normal luminal epithelial cells from human mammary gland with SV40 DNA alone may thus cause random genetic changes eventually resulting in tumorigenic cell lines. Since Hu-MI, HuMI-T and HuMI-TTul represent some of the consecutive stages taking place during cellular transformation, they are particularly suited as a novel in vitro model system to study progression of human breast cancer.

Immunohistochemical analysis of the p53 oncoprotein on paraffin sections using a series of novel monoclonal antibodies

Alterations of the p53 tumour suppressor gene are considered critical events in multistage carcinogenesis of a wide range of human cancers. In an attempt to elucidate the role of various p53 mutations in tumorigenesis and to investigate their relationship to the p53 protein accumulation and subcellular localization, we have raised a new series of 21 mouse monoclonal antibodies (MAbs) to human recombinant p53. The new MAbs (designated the Bp53 series) appear to recognize mainly denaturation-resistant epitopes in immunoblotting and the majority of them are suitable for immunostaining of p53 in cultured cells and frozen sections. Furthermore, at least three MAbs (Bp53-11, Bp53-12, and Bp53-28) proved to be reliable reagents for immunohistochemistry on paraffin-embedded specimens. The immunohistochemical analysis of paraffin sections from 118 human tumours of various histogeneses with Bp53-11 and Bp53-12 showed nuclear accumulation of the p53 protein in variable proportion of tumour cells in 76 cases (64 per cent). The influence of three parameters of tissue processing (type of fixative, period of fixation, and duration of autolysis) on p53 protein detection was also investigated. The results of this study provide the necessary basis for wider application of these novel MAbs as tools in both routine histopathology and functional analyses of the p53 oncoprotein.

Toward a molecular understanding of human breast cancer: a hypothesis

A rate limiting step in most metastatic breast cancers is the development of unlimited proliferative potential by mammary epithelial cells. We describe mechanisms by which these cells can attain this state. The two independent mortality mechanisms controlling fibroblast senescence and immortalization (M1 and M2) are also found in human mammary epithelial cells. However, although both p53 and Rb are involved in the M1 mechanism of fibroblast cellular senescence, in human mammary epithelial cells only p53 is involved. The M1/M2 mechanisms may be induced by the gradual loss of telomere ends that occur as normal cells divide. Loss of telomere ends may result in genomic instability and in altered gene expression due to heterochromatin changes in subtelomeric regions. Events which can abrogate p53 functions are described, as is the current state of knowledge about the function of p53. All these factors are included in a molecular model for the onset of breast cancer.

Preferential chromosome loss in human papilloma virus DNA-immortalized mammary epithelial cells

Human papilloma virus (HPV) DNA-immortalized human mammary epithelial cells may provide a model system for studying the molecular basis of immortalization and its role in breast neoplasia. Cytogenetic analyses were performed on clones derived from HPV 16- and HPV 18-immortalized human mammary epithelial cells. The majority of the clones contained near-diploid karyotypes. The single most frequent whole-chromosome loss was that of chromosome 19. Regions that showed preference for deletion and/or translocation included 2pter, 11qter, and 15pter. Evidence of chromosome 19 loss was confirmed by polymerase chain reaction (PCR)-generated, chromosome 19-specific, dinucleotide microsatellite repeat polymorphism analysis.

Single-steep transformation of human breast epithelial cells by SV40 large T oncogene

Normal human mammary epithelial cell (HMEC) cultures originating from 2 mammoplasty reduction surgical samples were transfected with replication-defective SV 40 DNA. Two independent cell lines designated as S2T2 and S1T3, selected for their increased proliferation potential and lifespan, were propagated for greater than 22 months in culture. They maintained a near-diploid karyotype with few chromosomal markers such as trisomy 1q (S1T3) and trisomy 8q (S2T2), which are most common in breast cancer in vivo. Immortalized S1T3 cells were not tumorigenic, whereas S2T2 cells produced slowly growing tumors in nude mice. One tumor was propagated in vitro and the transformed NS2T2 cell line subsequently raised 100% large tumors in the nude mouse. Rearrangement of the SV40 genome was observed in NS2T2 cells, which was not associated with increased expression of large T antigen. S1T3, S2T2 and transformed NS2T2 cell lines expressed cytokeratins CK18, CK19, the mammary-specific antigen DF3, and functional EGF receptors. Single-step immortalization and malignant transformation of human breast epithelial cells can thus occur upon transfection with SV40 large T oncogene. The chromosomal abnormalities observed in these cell lines suggest that they could offer a model for the study of breast-tumor progression in vitro.

Characterization of epithelial phenotypes in mortal and immortal human breast cells

We have previously described the mortal human breast epithelial culture MCF-10M, that was derived from fibrocystic breast tissue, was cultivated in medium with low calcium content for over 2 years, and spontaneously gave rise to the immortal MCF-10 cell line. The emergence of immortalized cells, characterized by growth in conventional calcium levels, from mortal cells has proven to be a reproducible event. Here we report the establishment of a second immortal line from MCF-10M, designated MCF-10-2, and establishment of the MCF-12 immortal line after long-term cultivation of MCF-12M mortal cells from reduction mammoplasty tissue. DNA fingerprinting demonstrated the independent, human origin and lineage of the MCF-10-2 and MCF-12 cell lines. Both lines require cortisol and EGF for maximal growth. The expression in these cultures of in vivo breast epithelial phenotypes was analyzed using 2-dimensional gel Western blots and immunoperoxidase staining with antibodies to cytokeratins and polymorphic epithelial mucin. MCF-10M and MCF-12M retain the cytokeratin profile of the luminal cell (7, 8, 18, 19), and also express cytokeratin 14, found predominantly in basal cells. The immortal lines express a similar profile, except that cytokeratin 19, a component of the fully differentiated luminal cell, is not expressed in the more uniform population seen in MCF-10 and MCF-12, but is retained in the morphologically mixed, less-selected population of MCF-10-2. Epitopes on the polymorphic epithelial mucin, recognized by antibodies HMFG 1, HMFG 2 and SM-3, were detected in the mortal cultures and in the immortal lines, indicating the occurrence of both normal and abnormal mucin processing. MCF-10, MCF-10-2 and MCF-12 cells do not form tumors in nude mice, but appear to organize as duct-like structures before regressing in the 5th week post injection.

Human thymic epithelial cells are frequently transformed by retroviral vectors encoding simian virus 40

The thymic microenvironment contains a mixture of phenotypically distinct epithelial cells of varied functions, some of which are unknown. In an attempt to understand their relevance to T cell differentiation in the thymus, human thymic epithelial cell clones from both fetal (SM3-SM5) and postnatal (SM6) thymus were produced by using a defective recombinant retroviral vector encoding the simian virus 40 large T antigen and the neomycin resistance gene. The presence of keratins 8 and 18, desmosomes, and tonofilaments confirmed the epithelial origin of the cell strains. The cells expressed Thy-1 and HLA-Class I at high levels, showed weak-expression antigens defined by TE3B and A2B5, and low to negligible levels of the MR19-defined molecule. When compared with the phenotype of thymic epithelial cells in situ, the cell strains appear to be derived from neuroendocrine components in the outer cortical region of the human thymus. The use of retroviral vectors to transform human thymic epithelium was considerably more efficient than transfection with a plasmid carrying the origin of replication-defective SV40 large T gene. In the latter case, only two cell strains with subcapsular epithelial phenotypes were derived from fetal thymus. With the retroviral vectors, epithelial cell strains could, for the first time, be generated from human postnatal thymus as well as from fetal thymus.

p53 protein alterations in human testicular cancer including pre-invasive intratubular germ-cell neoplasia

Expression of the p53 oncoprotein was examined in a wide range of primary human testicular germ-cell tumours using a new mouse monoclonal antibody (MAb) BP53-11 raised and characterized in this study, in parallel with a polyclonal rabbit antiserum CM-1. Immunohistochemistry on paraffin sections showed positive nuclear reaction in at least a fraction of malignant cells in 90 (84%) out of 107 cases studied. Aberrant accumulation of the p53 protein was found among testicular tumours of all major histological types, although generally a higher percentage of positive cases and a higher proportion of p53 over-expressing nuclei within individual lesions was observed in embryonal carcinomas when compared with seminomas. The typical heterogeneous staining pattern characteristic of histological specimens was also found in a cultured cell line derived from a human embryonal carcinoma. In contrast to immunohistochemically undetectable levels in normal testes and morphologically normal tissue areas in the tumour-bearing testes, the accumulation of the p53 protein was clearly identified in a high proportion (59% of cases) of the pre-invasive lesions with positive atypical intratubular germ cells often found in the tissue adjacent to invasive tumours. Altered expression of the p53 protein is therefore a unifying feature of the majority of invasive male germ-cell tumours and the change resulting in high levels of p53 appears to be a relatively early step in the human testicular cancer pathogenesis.

A series of 14 new monoclonal antibodies to keratins: characterization and value in diagnostic histopathology

A series of 14 new mouse monoclonal antibodies (MAbs) to keratins is described and the data suggesting their potential value in the differential diagnosis of human tumours are reported. The specificities of individual MAbs of the 'C-series' presented here range from monospecificity for keratin No. 7 (MAbs C-18, C-35, C-62, and C-68), keratin No. 8 (MAbs C-15, C-43, and C-15), and keratin No. 18 (MAbs C-04 and C-08) up to the broadly reacting 'pan-keratin' MAb C-11, with the target epitopes of the remaining four MAbs being shared by different pairs of keratin polypeptides. The results of the biochemical characterization of the MAbs, together with their immunohistochemical staining patterns on frozen as well as on paraffin sections of normal human tissues, suggest that they represent a significant contribution to the growing list of anti-keratin MAbs applicable in both research and routine diagnostic pathology. The immunohistochemical examination of a wide range of human neoplasms with the new MAbs not only confirmed their value in making distinctions between carcinomas, on the one hand, and lymphomas, and gliomas, on the other, but also verified the possibility of more subtle subdivisions within the group of adenocarcinomas and their metastases. Furthermore, the identification of small subsets of breast carcinomas with decreased levels or apparent loss of the keratin No. 7 polypeptide and some cases of stomach carcinoma with apparently induced expression of this keratin suggests that such 'exceptions' must be considered when using keratin spectra as one of the criteria in differential diagnosis.