Malignant MCF10CA1 cell lines derived from premalignant human breast epithelial MCF10AT cells.

The MCF10 series of cell lines was derived from benign breast tissue from a woman with fibrocystic disease. The MCF10 human breast epithelial model system consists of mortal MCF10M and MCF10MS (mortal cells grown in serum-free and serum-containing media, respectively), immortalized but otherwise normal MCF10F and MCF10A lines (free-floating versus growth as attached cells), transformed MCF10AneoT cells transfected with T24 Ha-ras, and premalignant MCF10AT cells with potential for neoplastic progression. The MCF10AT, derived from xenograft-passaged MCF10-AneoT cells, generates carcinomas in approximately 25% of xenografts. We now report the derivation of fully malignant MCF10CA1 lines that complete the spectrum of progression from relatively normal breast epithelial cells to breast cancer cells capable of metastasis. MCF10CA1 lines display histologic variations ranging from undifferentiated carcinomas, sometimes with focal squamous differentiation, to well-differentiated adenocarcinomas. At least two metastasize to the lung following injection of cells into the tail vein; one line grows very rapidly in the lung, with animals moribund within 4 weeks, whereas the other requires 15 weeks to reach the same endpoint. In addition to variations in efficiency of tumor production, the MCF10CA1 lines show differences in morphology in culture, anchorage-independent growth, karyotype, and immunocytochemistry profiles. The MCF10 model provides a unique tool for the investigation of molecular changes during progression of human breast neoplasia and the generation of tumor heterogeneity on a common genetic background.

Expression of transforming growth factor-beta receptor type II and tumorigenicity in human breast adenocarcinoma MCF-7 cells.

To analyze transforming growth factor-beta (TGF-beta) response during MCF-7 cell progression, early passage (MCF-7E, < 200 passage) and late passage (MCF-7L, > 500 passage) cells were compared. MCF-7E cells showed an IC50 of approximately 10 ng/ml of TGF-beta1, whereas MCF-7L cells were insensitive. MCF-7E cells contained approximately threefold higher levels of TGF-beta receptor type II (TbetaRII) mRNA than MCF-7L, but their TbetaRI levels were similar. MCF-7E parental cells showed higher TbetaRII promoter activity than MCF-7L cells, which could be attributed to changes in Sp1 nuclear protein levels. Receptor cross-linking studies indicated that the cell surface receptor levels parallel mRNA levels in both cell lines. Limiting dilution clones of MCF-7E cells were established to determine the heterogeneity of TbetaRII expression in this cell line, and they showed varying degrees of TbetaRII expression. Fibronectin was induced at higher levels in cells expressing higher TbetaRII levels. All three TGF-beta isoforms were detected in limiting dilution clones and parental cells, but TGF-beta1 was more abundant relative to TGF-beta2 or 3, and no correlation between TGF-beta isoform profile with TGF-beta sensitivity was found. MCF-7L cells were tumorigenic and formed xenografts rapidly and progressively, whereas MCF-7E parental and limiting dilution clonal cells showed transient tumor formation followed by regression. These results indicate that decreased TbetaRII transcription in breast cancer cells leads to a loss of TbetaRII expression, resulting in cellular resistance to TGF-beta which contributes to escape from negative growth regulation and tumor progression.

Transforming and oncogenic potential of activated c-Ha-ras in three immortalized human breast epithelial cell lines.

The ability of activated c-Ha-ras (codon 12 valine) to transform human breast epithelial cells varied for three different immortalized normal human breast epithelial cell lines established from two different women. Although activated c-Ha-ras may transform and induce a preneoplastic phenotype in MCF10A cells, activated c-Ha-ras was not sufficient to transform MCF10-2A cells. Only two of three MCF10-2A clones which expressed mutant p21 protein acquired the ability to form colonies in soft agar. When xenografted into nude beige mice, two MCF10-2A clones formed squamous carcinomas and one formed no lesions at all. The ability to form tumors did not correlate with growth in soft agar. All three activated c-Ha-ras-transfected clones of MCF-12A formed colonies in soft agar but only two produced squamous carcinomas in nude beige mice. Unlike activated c-Ha-ras-transfected MCF10A cells, none of the activated c-Ha-ras-transfected MCF10-2A or MCF-12A clones formed ducts in xenografts. Rather, initial xenograft lesions consisted of nests of cells with squamous differentiation. These observations illustrate that additional events are involved in the transformation and progression of human breast epithelial cells with activated c-Ha-ras.

Chromosomal markers of immortalization in human breast epithelium.

We describe a series of five immortal breast cell lines that have emerged independently from diploid cultures from two individuals. We have karyotyped representative cultures of each of these lines prior to and at intervals after immortalization. Although considerable diversity of chromosomal aberration was found among the five lines, analysis of sublines has defined the chromosomal changes common for each immortalization. These changes differed both within and between the individual patient sources. Some common alterations were noted in lines from both patients, however, including loss of the short arm of chromosome 20 and gain of 1q. We suggest that genes within these chromosomal regions contribute to spontaneous immortalization of human breast epithelium.

Xenograft model of progressive human proliferative breast disease.

BACKGROUND: Progression of proliferative breast disease has been associated with increased risk for development of invasive carcinoma. Cell lines have been developed to facilitate the study of this process. Human cell line MCF10A originated from spontaneous immortalization of breast epithelial cells obtained from a patient with fibrocystic disease, and cell lines MCF10AneoN and MCF10AneoT were created by stable transfection of these cells with the neomycin-resistance gene and either the HRAS gene or the mutated T-24 HRAS gene, respectively. PURPOSE: Our goal was to develop an experimental model of progressive human proliferative breast disease. METHODS: MCF10A, MCF10AneoN, and MCF10AneoT cells were injected subcutaneously into the dorsal flank of male nude/beige (C57/BALB/c nu/nu bg/bg) mice (12 mice for each cell type). These mice were examined periodically for formation and persistence or growth of palpable nodules. One mouse per group was killed 1 week after cell injection; thereafter, mice were observed as long as possible. Cells were recovered from palpable lesions by enzymatic dissociation of the excised lesions. Cells re-established in tissue culture from a week-14 tumor (MCF10AneoT.TG1) were injected into 12 male nude/beige mice. Southern blot hybridization analysis of the HRAS gene locus and cytogenetic analyses were performed. RESULTS: Transplanted MCF10A and MCF10AneoN cells formed transient, small palpable nodules that regressed and disappeared during the 4th and 5th weeks. In 10 of the 12 mice, T-24 HRAS gene-transfected MCF10A cells (MCF10AneoT) formed small, flat nodules that persisted for at least 1 year. Three of these xenografts became carcinomas. One (removed 7 weeks after transplantation) was an undifferentiated carcinoma composed of polygonal cells with large, vesicular nuclei and numerous mitoses. The second (removed after 14 weeks) was an invasive squamous cell carcinoma. The third (removed after 56 weeks) was a moderately differentiated adenocarcinoma. Initially, xenografts of MCF10AneoT.TG1 cells showed intraductal proliferative changes; after 23 weeks, the lesions showed histologic features resembling those seen in atypical hyperplasia of the human breast, and later lesions showed characteristics of carcinoma in situ. The MCF10 lineage of cells of three MCF10AneoT.TG1 xenografts was confirmed by DNA fingerprinting and karyotype analysis. CONCLUSIONS: MCF10AneoT and MCF10AneoT.TG1 comprise a transplantable xenograft model that produces a broad spectrum of human proliferative breast disease. IMPLICATIONS: The reproducible establishment of representative stages in early breast cancer progression from the MCF10 model offers a new opportunity to analyze critical events of carcinogenesis and progression in breast cancer.

Nuclear matrix proteins in normal and breast cancer cells.

The progression from normal breast epithelium to a malignant phenotype may depend on changes in genetic events as well as failure of host mechanisms. Intermediate biomarkers are needed to more effectively identify malignant progression as well as to develop the potential for more specific treatments and prevention strategies. The nuclear matrix is the RNA-protein network which forms the skeleton of the nucleus and participates in DNA organization as well as multiple cellular functions. Nuclear matrix proteins have been demonstrated to be tissue and cell type specific as well as to reflect the state of cell differentiation and/or transformation. We prepared nuclear matrices from normal and cancer breast tissue from 10 patients with infiltrating ductal carcinoma of the breast as well as the MCF-10 mortal, immortal, and transfected breast cell lines. Nuclear matrices derived from normal human breast tissue and tumor tissue share common nuclear matrix proteins as well as demonstrate specific changes which appear to occur with the acquisition of the cancer phenotype. The MCF-10 cell lines demonstrate a phenotype that is intermediate between the normal and cancer tissue. These data suggest that the nuclear matrix may be an important biomarker in the pathogenesis of breast cancer.

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.

Ultrastructural and immunocytochemical characterization of an immortalized human breast epithelial cell line, MCF-10.

The human breast epithelial cell line MCF-10 was derived from s.c. mastectomy tissue from a 36-year-old, parous, premenopausal woman with fibrocystic disease. It was initiated as a mortal cell line (MCF-10M), which senesces when transferred serially in 1.05 mM calcium. These cells spontaneously gave origin to two immortal sublines, MCF-10A, or attached cells, and MCF-10F, or floating cells, which have proliferated for more than 4 years in Dulbecco's modified essential medium and Ham's F-12 either with the customary calcium concentration of 1.05 mM (DMEM-H) or in medium containing 0.04 mM calcium or low calcium. Studies reported here indicate that MCF-10 is a mammary epithelial cell line. Electron microscopy showed that both MCF-10A and MCF-10F have characteristics of luminal ductal cells, but not of myoepithelial cells. When grown for more than 1200 days in Dulbecco's modified essential medium-Ham's F-12 and low calcium media, respectively, they maintained their epithelial characteristics, although the concentration of calcium exerted a powerful influence on cell morphology. Cells grown in Dulbecco's modified Eagle's medium-Ham's F12 medium are low cuboidal with numerous desmosomes and short microvilli, whereas those grown in low calcium medium have significantly reduced number of desmosomes, are more spherical, and have greater numbers of microvilli which are longer than those of cells grown in DMEM-H. The breast epithelial orgin of these cells was confirmed by immunocytochemical detection of epithelial sialomucins and keratins. The monoclonal antibodies MFA-breast and MC5 and the polyclonal antibody epithelial membrane antigen were used to detect the epithelial sialomucins. Keratins were characterized by using KA-4, K-14, AE1/AE3, and K-19 specific antibodies. It was concluded that MCF-10A and MCF-10F cells are breast epithelial cells and that they represent an important tool for studies of the basic processes of growth and carcinogenesis.

Isolation and characterization of a spontaneously immortalized human breast epithelial cell line, MCF-10.

Two sublines of a breast epithelial cell culture, MCF-10, derived from human fibrocystic mammary tissue exhibit immortality after extended cultivation in low calcium concentrations (0.03-0.06 mM) and floating transfers in low calcium (MCF-10F), or by trypsin-Versene passages in the customary (normal) calcium levels, 1.05 mM (MCF-10A). Both sublines have been maintained as separate entities after 2.3 years (849 days) in vitro and at present have been in culture for longer than 4 years. MCF-10 has the characteristics of normal breast epithelium by the following criteria: (a) lack of tumorigenicity in nude mice; (b) three-dimensional growth in collagen; (c) growth in culture that is controlled by hormones and growth factors; (d) lack of anchorage-independent growth; and (e) dome formation in confluent cultures. Cytogenetic analysis prior to immortalization showed normal diploid cells; although later passages showed minimal rearrangement and near-diploidy, the immortal cells were not karyotypically normal. The emergence of an immortal culture in normal calcium media was not an inherent characteristic of the original tissue from which MCF-10 was derived since reactivated cryo-preserved cells from cultures grown for 0.3 and 1.2 years in low calcium were incapable of sustained growth in normal calcium.

A simplified method for passage and long-term growth of human mammary epithelial cells.

A method is described for culturing human mammary epithelial cells in primary culture and allowing more than 50 generations and a 1000-fold increase from starting inocula without need of enzymatic transfers. Organoids dissociated from breast tissue are plated in medium containing 1.05 mM Ca++ to effect attachment and growth to monolayer density. Medium is then switched to one containing 0.06 mM Ca++ to overcome "renewal inhibition" and to stimulate growth. In low Ca++ media, primary cultures become a long-term, continuous source of free-floating viable cells free of fibroblasts. A fundamental requirement for extended growth in primary culture is maintaining calcium levels at approximately 0.06 mM. Above 0.06 mM Ca++, cells divide only 3 to 4 times in primary cultures before terminal differentiation occurs. At 0.06 mM Ca++, cells continue to divide for periods of time determined partly by feeding schedule, but up to 6 mo. and 50 generations of (linear) growth. Cells released from monolayer were greater than 90% viable and yielded 10(5) cells/cm2 of attached cells every 72 h. Free-floating single cells readily replated and cloned, when transferred, without need of trypsin for dissociation. Long-term free-floating cells were typical mammary epithelium: they formed domes and exhibited renewal inhibition, they produced ductlike formations in collagen gels, they contained epithelium-specific keratin filaments, and they were diploid.

Calcium regulation of normal human mammary epithelial cell growth in culture.

The concentration of Ca++ in culture media profoundly affected the growth and differentiation properties of normal human mammary epithelial cells in short-term culture. In media where Ca++ was above 0.06 mM, longevity was limited to an average of three to four cell divisions. The extended growth fraction (those cells able to divide more than once) was only approximately 50% and diminished to zero quickly with time. Stationary cells inhibited from dividing appeared differentiated in the formation of lipid vacuoles and accumulation of alpha-lactalbumin. Growth of stationary cultures could be reinstituted in about half the cells, either by disruption and transfer or by a reduction in Ca++ to less than 0.08 mM. The reduction of Ca++ to levels below 0.08 mM extended the longevity of normal cells to eight to nine divisions. The extended growth fraction was 100%. Under these conditions, cells did not differentiate. The effects of Ca++ on growth and differentiation were specific (Mg++ and Mn++ variations were without effect) and reversible and in many respects resembled Ca++ effects on epidermal cells. One major difference is that the dual pathways of growth and differentiation in mammary cells were controlled by glucocorticoid and insulin. Based on the kinetics of the reversible Ca++-induced coupling and uncoupling of proliferation and the program of differentiation, we proposed that Ca++ may be an essential trigger for cell divisions that commit a mammary cell to differentiate progressively in a permissive hormonal milieu.

Renewal inhibition of human mammary cell growth in vitro: cortisol and the recruitment of cells to terminal differentiation.

Cortisol and insulin stimulated exponential growth of normal human mammary epithelium in short-term monolayer culture. The response of cells depended on their organization into "growth units" on the surface of the culture dish; single cells did not respond. Growth of cells in the units ceased after only 3-4 doublings, ending in terminal differentiation. The 3-4 divisions that occurred in response to insulin and cortisol and that resulted in terminal differentiation, were not inhibited by short-range signals normally transmitted at population confluence. When growing above confluence density in response to hormones, cells reduced volume to accommodate the "terminal differentiation" divisions while still largely preserving a monolayer. The longevity of populations of normal cells (9-14 divisions), which occurred in 3 or 4 passages, exceeded the average longevity of individual cells in one passage (3-4 divisions). This disparity between real and apparent longevity was due to the inhibition of growth of divisional cells within growth units, which occurred in concert with terminal differentiation of other cells in these units. Inhibited cells could be recruited to undergo terminal differentiation divisions in response to cortisol and insulin, but only when the growth units were disrupted and terminally differentiated cells were eliminated, which occurred at subculture. We refer to the inhibition of growth that occurs in growth units as "renewal inhibition" to distinguish it from population-wide "confluence inhibition" and to emphasize three other aspects: (1) it occurred in terminally differentiating growth units; (2) it occurred in the continued presence of an inductive hormonal stimulus for differentiative growth; and (3) it conserved less differentiated cells for recruitment to terminal differentiation. There are parallels between renewal inhibition in vitro and the signals that restrain growth of mammary cells in 'growth buds" in vivo to preserve their capacity for multiple cycles of secretory differentiation. Differences in the behavior of normal and malignant breast cells in vitro suggest that renewal inhibition, rather than confluence inhibition, may be an important locus of growth control alteration in malignant transformation.

Phenotypic variance among cells isolated from spontaneous mouse mammary tumors in primary suspension culture.

A method is given for selecting epithelial cells directly from primary mammary tumors in Methocel suspension culture. The frequency of colony-forming units in primary tumors was approximately 10(-4). Colonies grew by cell division; formation and growth of colonies was cell density dependent. Five Methocel isolates were established in monolayer culture and characterized. Two were epithelial, evidenced by functional occluding junctions. The other three were not typed in vitro, although they formed carcinomas in vivo. All were subtetraploid by passage 10. There were variations in ability of the five Methocel isolates to reclone in suspension that appeared to be due to the evolution of anchorage-dependent variants during their growth in monolayer culture. These variants could be purified by limiting dilution plating on solid substrates. The five Methocel isolates and their derivative variants were used to determine correlations between transformation markers and tumorigenicity. Only three Methocel-derived sublines of nine tested, including two recloned in Methocel, were tumorigenic at all when inoculated in two sites of three syngeneic hosts, one athymic. The other six were nontumorigenic. The tumorigenic sublines were less tumorigenic than uncultured cells of parent tumors or parent tumor cells grown in primary monolayer culture. Thus, anchorage-independent growth is not a reliable marker for the tumorigenic mammary phenotype. No correlation was found between two other "contact-related" transformation markers, rapid growth rate and monolayer overgrowth, and tumorigenicity. The three transformation markers were expressed independently. Both tumorigenic and nontumorigenic sublines expressed mammary tumor virus antigens M.W. 28,000 protein and M.W. 52,000 glycoprotein, although only a minor fraction of cells contained the M.W. 52,000 glycoprotein. These data emphasize the heterogeneity of phenotypes in mammary tumors as well as differences between fibroblasts and mammary epithelium in models of neoplastic transformation.

Estrogen responsive proliferation of clonal human breast carcinoma cells in athymic mice.

A clone of MCF-7 (MCF-7ED), a cell in continuous in vitro cultivation derived from an estrogen-responsive human breast carcinoma, requires estrogen supplementation for progressive exponential (double time: 50--85 h) tumor growth in the mammary fat of athymic mice. The plasma concentration of estradiol which stimulated exponential growth of MCF-7ED corresponded to physiologic premenopausal levels in women. The tumors were carcinomas with murine and MCF-7ED cells intermixed. MCF-7ED cells could be repurified in subcultures of mixed tumors. Comparative studies of breast and non-breast cell lines showed concordance between the presence of estradiol receptor, sensitivity to the anti-estrogen tamoxifen for growth in vitro, and estradiol dependence for tumorigenic growth in athymic mice. Progesterone alone did not stimulate MCF-7ED growth, but acted synergistically with estrogen. Progesterone's action was to decrease tumor latent period, not to increase final tumor incidence or growth rate. Under estrogen-deficient conditions, condsitions approximating postmenopausal status in women, (10(-10) M in plasma), a dormant state was established between MCF-7ED cells and murine mammary stroma which could be maintained several months. The dormant state could be broken by introduction of estradiol, but not progesterone. This system should be useful for defining host and cancer cell determinants in estrogen-responsive breast cancer growth.

Reexpression of the original tumor pattern by a human breast carcinoma cell line (MCF-7) in sponge culture.

A stable cell line (MCF-7), derived from a pleural effusion of a patient with metastatic breast carcinoma, was maintained in these laboratories for more than 3 years in conventional monolayer culture. To further characterize the tumor origin of the MCF-7 line, cells were grown on collagen-coated cellulos sponges. On the three-dimensional sponge matrix, the cells formed clusters, ductlike structures, and lumina similar to the patterns observed in the antecedent primary tumor and in the pleural metastasis. The similarity between the original tumor and the cells grown in sponge suggested that the MCF-7 cells did in fact retain the potential to express the histologic patterns of tumor, even in the absence of stroma support. This study confirmed the utility of sponge culture for the investigation of the retention of tumor characteristics by cultured cells of neoplastic origin.

Fine structure of a murine mammary carcinoma cell line.

A fine structural study was made of cells from the epithelioid MCF-8/5-2A cell line derived from a MuMTV-free D2 transplantable hyperplastic outgrowth. Electron microscopy shows the cells to be truly epithelial with many cell-to-cell junctions and microvilli. The cells are similar in many respects to normal mouse mammary gland and some of the conventional mammary tumor derived cell lines. This study supports previous observations of the absence of MuMTV in MCF-8 within the limits of morphological detection, and demonstrates the presence of numerous virus particles within, or budding into, cisternae of the endoplasmic reticulum and nuclear envelope. These intracisternal A particles have not been previously described in such abundance in mammary tumor tissue culture cells.