Epithelial HBL-100 cell line derived from milk of an apparently healthy woman harbours SV40 genetic information

Long Noncoding RNA DCST1-AS1 Promotes Cell Proliferation and Metastasis in Triple-negative Breast Cancer by Forming a Positive Regulatory Loop with miR-873-5p and MYC

Background: DC-STAMP domain containing 1-antisense 1 (DCST1-AS1) is a long noncoding RNA (lncRNA) that is up-regulated in triple-negative breast cancer (TNBC) tissues. Here, we attempt to investigate the oncogenic property of DCST1-AS1.

Methods: LncRNA microarrays were used to detect differentially expressed lncRNA in cancerous tissues. Fluorescence in situ hybridization assay was used to detect the distribution of DCST1-AS1 in BT-549 and MDA-MB-231 cells. Lentiviral systems, inhibitors, siRNA and overexpression plasmids were used for gain- and loss-of-function experiments. Colony formation assay, wound healing assay, CCK8 assay, transwell assay, and flow cytometry assay were used to study the function of DCST1-AS1. Luciferase assay was used to verify the binding of MYC to the promoter region and the binding of miR-873-5p to DCST1-AS1. RNA immunoprecipitation assay was used to verify that argonaute 2 binds to both miR-873-5p and DCST1-AS1. Western blotting was used to measure changes in protein expression.

Results: Consistent with the microarray results, we found that DCST1-AS1 was up-regulated in both TNBC tissue samples and cell lines. DCST1-AS1 was positively correlated with distant metastasis and histopathological grades. DCST1-AS1 is distributed in both nucleus and cytoplasm. Knockdown of DCST1-AS1 inhibits TNBC cell proliferation and metastasis, while overexpression of DCST1-AS1 promotes TNBC cell proliferation and metastasis. We confirmed that DCST1-AS1 expression in TNBC cells is regulated by MYC. Furthermore, we found that DCST1-AS1 is negatively correlated with miR-873-5p in TNBC tissues and is a direct target gene of miR-873-5p. Argonaute 2 is involved in the binding of DCST1-AS1 and miR-873-5p and promotes the degradation of DCST1-AS1. The interaction of DCST1-AS1 with miR-873-5p ultimately up-regulated the expression of insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1), MYC, CD44 and lymphoid enhancer binding factor 1 (LEF1).

Conclusions:DCST1-AS1 is activated by MYC and is degraded by binding to miR-873-5p, thereby upregulating the expression of miR-873-5p downstream proteins IGF2BP1, MYC, LEF1 and CD44. MYC, DCST1-AS1 and miR-873-5p form a positive regulatory loop to promote TNBC cell proliferation and metastasis.

The non-receptor tyrosine kinase TNK2/ACK1 is a novel therapeutic target in triple negative breast cancer

Breast cancer is the most prevalent cancer in women worldwide. About 15-20% of all breast cancers do not express estrogen receptor, progesterone receptor or HER2 receptor and hence are collectively classified as triple negative breast cancer (TNBC). These tumors are often relatively aggressive when compared to other types of breast cancer, and this issue is compounded by the lack of effective targeted therapy. In our previous phosphoproteomic profiling effort, we identified the non-receptor tyrosine kinase TNK2 as activated in a majority of aggressive TNBC cell lines. In the current study, we show that high expression of TNK2 in breast cancer cell lines correlates with high proliferation, invasion and colony forming ability. We demonstrate that knockdown of TNK2 expression can substantially suppress the invasiveness and proliferation advantage of TNBC cells in vitro and tumor formation in xenograft mouse models. Moreover, inhibition of TNK2 with small molecule inhibitor (R)-9bMS significantly compromised TNBC proliferation.

Finally, we find that high levels of TNK2 expression in high-grade basal-like breast cancers correlates significantly with poorer patient outcome. Taken together, our study suggests that TNK2 is a novel potential therapeutic target for the treatment of TNBC.

Effect of neighboring cells on cell stiffness measured by optical tweezers indentation

We report on the modification of mechanical properties of breast cancer cells when they get in contact with other neighboring cells of the same type. Optical tweezers vertical indentation was employed to investigate cell mechanics in isolated and contact conditions, by setting up stiffness as a marker. Two human breast cancer cell lines with different aggressiveness [MCF-7 (luminal breast cancer) and MDA-MB-231 (basal-like breast cancer)] and one normal immortalized breast cell line HBL-100 (normal and myoepithelial) were selected. We found that neighboring cells significantly alter cell stiffness: MDA-MB-231 becomes stiffer when in contact, while HBL-100 and MCF-7 exhibit softer character. Cell stiffness was probed at three cellular subregions: central (above nucleus), intermediate (cytoplasm), and near the leading edge. In an isolated condition, all cells showed a significant regional variation in stiffness: higher at the center and fading toward the leading edge. However, the regional variation becomes statistically insignificant when the cells were in contact with other neighboring cells. The proposed approach will contribute to understand the intriguing temporal sequential alterations in cancer cells during interaction with their surrounding microenvironment.

High Expression of the Newly Found Long Noncoding RNA Z38 Promotes Cell Proliferation and Oncogenic Activity in Breast Cancer

The aberrant expression of long noncoding RNAs (lncRNAs) has great impacts on cancer origination and progression. In the current study, a newly found lncRNA Z38, which was identified through combining experiments of suppression subtractive hybridization (SSH) and reverse dot-blotting, was found to have high expression in breast cancer. More importantly, inhibiting Z38 expression by gene silencing greatly suppressed breast cancer cell proliferation and tumorigenesis, and treatment with Z38 siRNAs significantly induced cell apoptosis and inhibited tumor growth. In conclusion, the newly found lncRNA Z38, which plays important roles in breast cancer, may act as a candidate biomarker and therapeutic target in carcinomas.

Probing Regenerative Potential of Moringa oleifera Aqueous Extracts Using In vitro Cellular Assays

Background:

Molecules stimulating regeneration and proliferation of cells are of significance in combating ailments caused due to tissue injury, inflammation, and degenerative disorders. Moringa oleifera is one of the most valued food plants having the profile of important nutrients and impressive range of medicinal uses.

Objective:

To evaluate the potential of M. oleifera aqueous leaf and flower extracts to promote the proliferation of cells and explore their effect on cancer cell lines for assessment of safety.

Materials and Methods:

Aqueous leaf and flower extracts of M. oleifera were investigated for effect on rat-derived primary fibroblast, mesenchymal stem cells (MSCs), and cancer cell lines using cell proliferation assay. They were also tested and compared for wound healing, angiogenesis, and hepatoprotective effect using in vitro assays.

Results:

Statistically significant increase in the proliferation of primary rat fibroblast, MSCs, and angiogenesis was observed after treatment with aqueous flower extract. The aqueous leaf extract determined a comparatively moderate increment in the proliferation of MSCs and angiogenesis. It however showed prominent cytotoxicity to cancer cell lines and a significant hepatoprotective effect.

Conclusion:

A very clear difference in response of the two extracts to different types of cells was detected in this study. The aqueous flower extract exhibited a higher potential to stimulate cell proliferation while not exerting the same effect on cancer cell lines. The leaf extract on the other hand, had a prominent antitumor and hepatoptotective effects.

SUMMARY

Moringa oleifera flower extract showed significant ability to promote proliferation of rat fibroblast and mesenchymal stem cells. The extract also had prominent angiogenic and hepatoprotective effects.

The extract did not influence proliferation of cancer cell lines indicating its safety for human consumption and use in pharmaceuticals.

The Moringa oleifera leaf extract showed relatively less potential to stimulate cells but had prominent cytotoxic effect on cancer cell lines.

Abbreviations Used: ALT: Alanine transaminase, AST: Asparatate amino transferase, ATCC: American type culture collection, BMMSC: Bone marrow mesenchymal stem cells (used in this paper), CAM: Chick chorioallantoic membrane, CCl4: Carbon tetra chloride, DMEM: Dulbecco's modified Eagle medium, DMSO: Dimethyl sulfoxide, EDTA: Ethylene diamine tetraacetic acid, HBL 100: Human breast epithelial cell line, Mcf-7: Human breast adenocarcinoma cell line, aMEM: Minimum Essential Medium Eagle alpha modification, MOF: Moringa oleifera aqueous flower extract (used in this paper), MOL: Moringa oleifera aqueos leaf extract (Used in this paper), OD: Optical density, PBS: Phosphate buffered saline

Global phosphotyrosine survey in triple-negative breast cancer reveals activation of multiple tyrosine kinase signaling pathways

Breast cancer is the most prevalent cancer in women worldwide. About 15-20% of all breast cancers are triple negative breast cancer (TNBC) and are often highly aggressive when compared to other subtypes of breast cancers. To better characterize the biology that underlies the TNBC phenotype, we profiled the phosphotyrosine proteome of a panel of twenty-six TNBC cell lines using quantitative high resolution Fourier transform mass spectrometry. A heterogeneous pattern of tyrosine kinase activation was observed based on 1,789 tyrosine-phosphorylated peptides identified from 969 proteins. One of the tyrosine kinases, AXL, was found to be activated in a majority of aggressive TNBC cell lines and was accompanied by a higher level of AXL expression. High levels of AXL expression are correlated with a significant decrease in patient survival. Treatment of cells bearing activated AXL with a humanized AXL antibody inhibited cell proliferation and migration in vitro, and tumor growth in mice. Overall, our global phosphoproteomic analysis provided new insights into the heterogeneity in the activation status of tyrosine kinase pathways in TNBCs. Our approach presents an effective means of identifying important novel biomarkers and targets for therapy such as AXL in TNBC.

Effect of testosterone on E1S-sulfatase activity in non-malignant and cancerous breast cells in vitro

INTRODUCTION

Testosterone (T) is a therapeutic option for women with hypoactive sexual desire disorder. T may have an impact on the mammary gland by altering local estrogen synthesis. The aim of the present study was to measure the effect of T on estrone-sulfate (E1S)-sulfatase (STS) expression, and activity using hormone-dependent BC cells with high and low aggressive potential (BT-474, MCF-7), and HBL-100 as a breast cell line of non-malignant origin.

METHODS

Cells were incubated in RPMI 1640 medium containing 5% steroid-depleted fetal calf serum for 3d, and subsequently incubated in absence or presence of T alone, and combined with anastrozole (A) at 10(-8)M, and 10(-6)M at 37 degrees C for either 24h or directly in cell extracts ("direct"). STS protein expression was measured by dot-blot (immunoblotting), and STS, HSD17B1 and HSD17B2 mRNA levels by quantitative RT-PCR. STS activity was evaluated by incubating homogenized breast cells with [(3)H]-E1S and separating the products E1, and E2 by thin layer chromatography.

RESULTS

Basal STS mRNA expression did not reveal group differences. However, STS mRNA was decreased by T+A in MCF-7 cells. 17HSDB1 expression was decreased by T+A in BT-474 cells, and 17HSDB2 expression was decreased by A and T+A treatment in MCF-7 cells. Basal and T treated STS protein expression was significantly higher in malignant compared to non-malignant breast cells. However, T did not induce significant intra-cell line differences. Similarly, basal and T treated STS activity was significantly higher in highly malignant compared to non-malignant breast cells. Regardless of cell lines, T slightly decreased STS activity after "direct" incubation, but led to an increase of local estrogen formation after 24h which was attenuated, and partly reversed by A, respectively.

CONCLUSIONS

The more aggressive the breast cell line, the higher the local estrogen formation. The transition from normal to malignant seems to be accompanied by an altered autoregulation. The given local endocrine milieu seems to be essential for response to T.

Evidence for a role of the Simian Virus 40 in human breast carcinomas

AIMS OF THE STUDY

The aim of this study was to investigate whether the Simian Virus 40 (SV40) is implicated in human breast carcinomas (BC).

EXPERIMENTAL DESIGN

SV40 presence was investigated by PCR assays targeting the Tag, the regulatory, and the VP1 regions in 109 invasive breast ductal carcinomas from Tunisian women. We also examined the relationship between the presence of SV40 and promoter methylation status of 15 tumor-related genes. Immunohistochemistry was used to investigate the expression of Tag, estrogen and progesterone receptors, HER2, and P53.

RESULTS

SV40 DNA sequences were detected in 22% of tumors and in only 1.8% of the matched non-tumoral tissues. Using immunohistochemistry, SV40 was detected in the tumor cells. Hypermethylation frequencies were 78% for RASSF1A, 66% for SHP1, 61% for HIN1 and BRCA1, 47% for P16 and ER, 42% for CDH1 and APC, 40% for BLU, 35% for DAPK, 34% for RARbeta2, 27% for GSTP1, 17% for TIMP3, 14% for CCND2, and 8% for hMLH1. Interestingly, the frequencies of RASSF1A, SHP1, BRCA1, and TIMP3 methylation, and the mean of the methylation index (MI) were significantly higher in SV40-positive than in SV40-negative cases (P-values ranging from 0.043 to 0.003). Moreover, SV40 presence correlates with P53 protein accumulation (32.7% vs. 13.3%; P=0.015) and HER2 low expression (3.7% vs. 28%; P=0.008). We also found SV40 more frequently in patients over 50 years than in younger patients (34.8% vs. 12.3%; P=0.006).

CONCLUSIONS

This study is the first to demonstrate the presence of SV40 in human BC and provides data supporting a role for this virus in the pathogenesis of these tumors.

Overexpression of fatty acid synthase gene activates HER1/HER2 tyrosine kinase receptors in human breast epithelial cells

OBJECTIVES

More than 50 years ago, we learned that breast cancer cells (and those of many other types of tumour) endogenously synthesize 95% of fatty acids (FAs) de novo, despite having adequate nutritional lipid supply. Today, we know that breast cancer cells benefit from this phenomenon in terms of enhanced cell proliferation, survival, chemoresistance and metastasis. However, the exact role of the major lipogenic enzyme fatty acid synthase (FASN) as cause, correlate or facilitator of breast cancer remains unidentified.

MATERIALS AND METHODS

To evaluate a causal effect of FASN-catalysed endogenous FA biosynthesis in the natural history of breast cancer disease, HBL100 cells (an SV40-transformed in vitro model for near-normal gene expression in the breast epithelium), and MCF10A cells (a non-transformed, near diploid, spontaneously immortalized human mammary epithelial cell line) were acutely forced to overexpress the human FASN gene.

RESULTS

Following transient transfection with plasmid pCMV6-XL4 carrying full-length human FASN cDNA (gi: NM 004104), HBL100 cells enhanced their endogenous lipid synthesis while acquiring canonical oncogenic properties such as increased size and number of colonies in semisolid (i.e. soft-agar) anchorage-independent cultures. Anchorage-dependent cell proliferation assays in low serum (0.1% foetal bovine serum), MTT-based assessment of cell metabolic status and cell death ELISA-based detection of apoptosis-induced DNA-histone fragmentation, together revealed that sole activation of endogenous FA biosynthesis was sufficient to significantly enhance breast epithelial cell proliferation and survival. When analysing molecular mechanisms by which acute activation of de novo FA biosynthesis triggered a transformed phenotype, HBL100 cells, transiently transfected with pCMV6-XL4/FASN, were found to exhibit a dramatic increase in the number of phosphor-tyrosine (Tyr)-containing proteins, as detected by 4G10 antiphosphor-Tyr monoclonal antibody. Phosphor-Tyr-specific antibodies recognizing the phosphorylation status of either the 1173 Tyr residue of epidermal growth factor receptor (HER1) or the 1248 Tyr residue of HER2, further revealed that FASN-induced Tyr-phosphorylation at approximately 180 kDa region mainly represented that of these key members of the HER (erbB) network, which remained switched-off in mock-transfected HBL100 cells. ELISA and immunoblotting procedures demonstrated that FASN overactivation significantly increased (> 200%) expression levels of epidermal growth factor receptor and HER2 proteins in HBL100 cells. Proteome Profilertrade mark antibody arrays capable of simultaneously detecting relative levels of phosphorylation of 42 phospho-receptor Tyr-kinases (RTKs) confirmed that acute activation of endogenous FA biosynthesis specifically promoted hyper-Tyr-phosphorylation of HER1 and HER2 in MCF10A cells. This FASN-triggered HER1/HER2-breast cancer-like phenotype was specifically inhibitable either by FASN inhibitor C75 or by Tyr-kinase inhibitors (TKIs) gefitinib (Iressa) and lapatinib (Tykerb) but not by chemotherapeutic agents such as cisplatin. Transient overexpression of FASN dramatically increased HBL100 breast epithelial cells' sensitivity to cytotoxic effects of C75, gefitinib and lapatinib (approximately 8, 10 and > 15 times, respectively), while significantly decreasing (approximately 3 times) cisplatin efficacy.

CONCLUSIONS

Although we cannot definitely establish FASN as a novel oncogene in breast cancer, this study reveals for the first time that exacerbated endogenous FA biosynthesis in non-cancerous epithelial cells is sufficient to induce a cancer-like phenotype functionally dependent on the HER1/HER2 duo. These findings may perhaps radically amend our current perspective of endogenously synthesized fat, as on its own, it appears to actively increase signal-to-noise ratio in the HER1/HER2-driven progression of human breast epithelial cells towards malignancy.

Differential effect of hormone therapy on E1S-sulfatase activity in non-malignant and cancerous breast cells in vitro

Breast tissue possesses the enzymes for local estrogen biosynthesis. We measured the effect of Estradiol (E2), Tibolone (OrgOD14) and its metabolite Org4094 on estrone sulfate (E1S)-sulfatase (STS) using breast cancer (MCF-7) and non-malignant breast cells (HBL-100). Cells were cultured in 5% steroid depleted fetal calf serum for 3 days and subsequently incubated with each steroid for either 24 h or directly in cell extracts. STS mRNA and protein expression, and its subcellular localization were determined by semi-quantitative RT-PCR, immunoblotting, and confocal immunofluorescence microscopy. STS activity was evaluated by incubating homogenized breast cells with [(3)H]-E1S. The products E1 and E2 were separated by thin layer chromatography. STS was co-localized with the Golgi marker protein GM130 and the endoplasmic reticulum marker protein calnexin. Treatment did not significantly alter STS mRNA expression. STS protein expression was increased by each steroid in HBL-100 cells but by E2 only in MCF-7 cells. 24 h incubation with OrgOD14 and Org4094 did not alter STS activity in both cell lines. However, STS activity was significantly diminished in HBL-100 but slightly increased in MCF-7 cells by 24 h treatment with E2. "Direct" incubation of cell extracts, eliminating cellular regulation of metabolism, reduced estrogen biosynthesis regardless of cell line and treatment. In conclusion, the immediate reduction of estrogen biosynthesis by OrgOD14 is counteracted by an increased STS protein expression. On the contrary, E2 exerts a differential effect on STS in HBL-100 and MCF-7 cells. The transition from normal to malignant breast cells may be accompanied by an abolished autoregulation of local estrogen formation.

Selective radiosensitization by nitric oxide in tumor cell lines

The radiosensitizing effect of nitric oxide (NO) on mouse and human tumor cells with different degrees of malignancy was evaluated. Cells pre-treated with the NO donor diethylenetriamine-NO (DETA-NO), were irradiated with gamma rays. Survival curves were obtained by clonogenicity and fitted to the linear-quadratic model. Results demonstrated an association between radiosensitization and degree of malignancy. The more malignant the cell line, the higher the degree of radiosensitization by DETA-NO. In conclusion, the differential radiosensitizing effect of DETA-NO shown here is of great interest for the potential use of NO in radiotherapy, due to an enhanced radiation effect on tumor vs. normal tissue.

Indole-3-carbinol-induced death in cancer cells involves EGFR downregulation and is exacerbated in a 3D environment

Indole-3-carbinol (I3C) is a promising anticancer dietary compound, which inhibits breast cancer in animal models. The objective of the current study was to characterize I3C-induced cell death in a panel of human breast tumorigenic cells (MCF7, MDA-MB-468, MDA-MB-231 and HBL100) in comparison with normal fibroblasts. Since epithelial cells are protected from cell death by a three-dimensional environment, 3D cell culture (collagen I gel and spheroids) was employed to investigate susceptibility to I3C. Cell viability in the presence of 256 microM I3C, a concentration close to the physiologically achievable range, was in the order fibroblasts = HBL100>MDA-MB-231>MCF7>MDA-MB-468 in monolayer culture. However, 3D culture conditions increased the susceptibility of MCF7 and MDA-MB-468 cancer cells towards I3C. I3C induced cell death in breast cancer MCF7, MDA-MB-468 and MDA-MB-231 cells via the mitochondrial apoptotic pathway. I3C significantly reduced levels of epidermal growth factor receptor (EGFR) in MDA-MB-468 after 6 h and in MDA-MB-231 and HBL100 cells after 30 h. Downregulation of EGFR in MDA-MB468 and MDA-MB-231 cells using an EGFR inhibitor resulted in apoptosis. EGFR modulation using EGF or an EGFR inhibitor markedly influenced viability and response to I3C in MDA-MB-468 cells in 3D conditions. EGFR expression was modulated by 3D conditions. Therefore, I3C-induced EGFR reduction in these cells is likely to be responsible for I3C-induced apoptosis.

Molecular characterization of the t(3;9) associated with immortalization in the MCF10A cell line

The t(3;9)(p14;p21) in the MCF10A human mammary gland epithelial cell line was the single cytogenetic event that accompanied the transition from primary culture to immortalized cell line, suggesting that it is related to the development of the immortalization phenotype. To study the molecular consequences of the breakpoints in this rearrangement, we used a combination of fluorescence in situ hybridization (FISH) and array comparative genomic hybridization (CGH). The 3p14 translocation breakpoint occurs within BAC RP11-795e22, which accommodates only the TAFA1 gene, a novel cysteine-rich secreted protein thought to be involved in cytokine signaling. TAFA1 is expressed in normal breast tissue, not in MCF10A, and shows differential expression in a range of breast cancer cell lines. The 9p translocation breakpoint results in a deletion of approximately 4 megabases on the derivative chromosome 9, which includes the CDKN2A (p16) gene. Array CGH and FISH analysis demonstrated that BAC 149i22, which contains the CDKN2A/B genes, is also deleted specifically on the apparently normal copy of chromosome 9, making MCF10A null for the p16/p15 genes. The exact extent of gains and losses of chromosome regions resulting from rearrangements involving chromosomes 1q, 5q, and 8q have also been characterized using the BAC arrays.

The centrosomal kinase Nek2 displays elevated levels of protein expression in human breast cancer

Aneuploidy and chromosome instability are common abnormalities in human cancer. Loss of control over mitotic progression, multipolar spindle formation, and cytokinesis defects are all likely to contribute to these phenotypes. Nek2 is a cell cycle-regulated protein kinase with maximal activity at the onset of mitosis that localizes to the centrosome. Functional studies have implicated Nek2 in regulation of centrosome separation and spindle formation. Here, we present the first study of the protein expression levels of the Nek2 kinase in human cancer cell lines and primary tumors. Nek2 protein is elevated 2- to 5-fold in cell lines derived from a range of human tumors including those of cervical, ovarian, breast, prostate, and leukemic origin. Most importantly, by immunohistochemistry, we find that Nek2 protein is significantly up-regulated in preinvasive in situ ductal carcinomas of the breast as well as in invasive breast carcinomas. Finally, by ectopic expression of Nek2A in immortalized HBL100 breast epithelial cells, we show that increased Nek2 protein leads to accumulation of multinucleated cells with supernumerary centrosomes. These data highlight the Nek2 kinase as novel potential target for chemotherapeutic intervention in breast cancer.

Relevance of breast cancer cell lines as models for breast tumours: an update

The number of available breast cancer cell (BCC) lines is small, and only a very few of them have been extensively studied. Whether they are representative of the tumours from which they originated remains a matter of debate. Whether their diversity mirrors the well-known inter-tumoural heterogeneity is another essential question. While numerous similarities have long been found between cell lines and tumours, recent technical advances, including the use of micro-arrays and comparative genetic analysis, have brought new data to the discussion. This paper presents most of the BCC lines that have been described in some detail to date. It evaluates the accuracy of the few of them widely used (MCF-7, T-47D, BT-474, SK-BR-3, MDA-MB-231, Hs578T) as tumour models. It is concluded that BCC lines are likely to reflect, to a large extent, the features of cancer cells in vivo. The importance of oestrogen receptor-alpha (gene ESR1 ) and Her-2/ neu ( ERBB2 ) as classifiers for cell lines and tumours is underlined. The recourse to a larger set of cell lines is suggested since the exact origin of some of the widely used lines remains ambiguous. Investigations on additional specific lines are expected to improve our knowledge of BCC and of the dialogue that these maintain with their surrounding normal cells in vivo.

Comparison of p53 mutational status with mRNA and protein expression in a panel of 24 human breast carcinoma cell lines

We analyzed the p53 mutational status, mRNA and protein expression in 24 human breast carcinoma cell lines. Following measurement of their DNA content with flow cytometry, we ascertained the copy numbers of the centromere of chromosome 17 (cen17) and p53 with fluorescence in situ hybridization (FISH). A functional yeast assay (FASAY) was used to screen for inactivating mutations. Positive results were subsequently verified by DNA sequencing. Finally, we assessed the mRNA expression with a competitive reverse transcription-polymerase chain reaction (RT-PCR) assay and the protein expression with immunocytochemical staining, western blot, and quantitative flow cytometry. The DNA content of the cell lines ranged from 0.85 to 2.58. Nine cell lines had concordant copy numbers (between two and four) of p53 and cen17, whereas 12 had more, and three less cen17 than p53 copies. The FASAY was successful in all but one cell line and revealed the presence of mutated alleles in 16 of them, 13 cell lines expressed only the mutated, and three both the mutated and the wild-type alleles. The mutations were comprised of 11 missense, two nonsense, and three frameshift mutations. Immunocytochemical staining, western blot and quantitative flow cytometry yielded comparable p53 protein expression results. However, both the mRNA and the protein expression levels varied considerably in the different cell lines and no consistent pattern with regard to the respective p53 mutational status became evident. The results obtained in these breast carcinoma cell lines indicate that no clear-cut linear relationship exists between the p53 mutational status and the extent of its respective mRNA and protein expression. Therefore, direct DNA analyses and functional assays remain the only methods for the reliable detection of p53 mutations.

MCF‐10AT: A Model for Human Breast Cancer Development

A number of lesions, collectively termed Proliferative Breast Disease (PBD), have been associated with high risk of developing breast cancer. Understanding of the natural history of PBD and its relationship to breast cancer progression has been hampered by the lack of an experimental model. MCF-10AT cells are of human, breast epithelial cell origin. They grow as xenografts in immune-incompetent mice where they produce normal-appearing ducts, atypical hyperplasia, carcinoma-in-situ, and invasive carcinoma. Estrogen supplementation of the mice accelerates development of cancer. The MCF-10AT model of PBD offers a new approach to the study of early breast cancer progression and its prevention.

Association of SV40 with human tumours

SV40 was discovered as a contaminant of poliovirus vaccines that were inadvertently administered to millions of people in Europe and the United States between 1955 and 1963. Shortly afterwards, SV40 was proven to be oncogenic in rodents and capable of transforming human and animal cells in vitro. The possibility that SV40 might cause tumours in humans thus became a subject of scientific and public interest and scrutiny. However, largely due to a lack of significant epidemiological evidence, interest in assessing SV40's potential carcinogenic role in humans diminished. Recently, many laboratories have reported the presence of SV40-like DNA in a high proportion of human mesotheliomas, ependymomas and osteosarcoma (the three main types of tumours caused by virus in hamsters), renewing the question whether SV40 might be a human tumour virus. Molecular data from these studies are reviewed to re-evaluate the potential role of SV40 as a human carcinogen.

Simian virus 40 is present in human lymphomas and normal blood

Many independent studies have demonstrated Simian virus 40 (SV40) in normal and neoplastic human tissues. Clonal integration of virus in the DNA of several thyroid and bone tumors suggests a direct role for SV40 in some cancers. However, in most cases the role of SV40 remains unclear. This study determined the presence of SV40, by amplification followed by hybridization, in 266 normal and neoplastic blood and lymphoid samples. Amplification detected SV40 in 14% of non-autoimmune deficiency syndrome (AIDS) lymphomas, 28% of AIDS related lymphoma and 16% of peripheral blood lymphocytes from non-cancerous patients. No SV40 was detected in leukemia samples. Direct Southern blotting of SV40+ samples detected no virus, consistent with less than one viral genome in ten cells. Sequence analysis of SV40 in blood and lymphoid samples found sequences distinct from laboratory strains of SV40. The presence of limited quantities of SV40 in a small proportion of both normal and neoplastic tissues is suggestive of an adventitious presence with no apparent direct role in blood and lymphoid cancers.

An in vitro model of human breast carcinogenesis: epigenetic aspects

A review is given of 12 years of research on a human breast epithelial cell line, HMT-3522, which has undergone malignant transformation in vitro without being exposed to known carcinogenic agents. Epigenetic aspects of the malignant transformation have been considered and the results have been viewed in a clinical context. It has been concluded that the history and characteristics of the cell line resembles the comedocarcinoma of the human breast. It is hypothesized that progression from benign lesion to comedo in situ carcinoma and invasive carcinoma occurs if low levels of epidermal growth factor are prevailing in the microenvironment. Our data also suggest that breast cancer developed under high epidermal growth factor receptor activity is estrogen receptor negative, while suppression of epidermal growth factor receptor activity promotes estrogen responsive breast cancer.

C-erbB-2/ HER-2 upregulates fascin, an actin-bundling protein associated with cell motility, in human breast cancer cell lines

The over-expression of c-erbB-2/ HER-2, a receptor tyrosine kinase, correlates with poor prognosis in patients with breast and ovarian cancer. In the human breast cancer cell line, MDA-MB-435, c-erbB-2 over-expression results in increased chemoinvasion and higher metastatic properties in nude mice. However, the mechanisms by which c-erbB-2 increases the malignant potential of cells remains unclear. We have determined that over-expression of c-erbB-2 in MDA-MB-435 cells, and in some additional breast cancer cell lines, is associated with graphic increases in mRNA and protein levels of the actin bundling protein fascin. Heightened fascin expression has been observed in other systems to result in greatly increased cell motility, and indeed, our work employing semi-automated time-lapse microscopy demonstrates that MDA-MB-435 cells over-expressing c-erbB-2 exhibit significantly heightened cellular dynamics and locomotion, while visualization of bundled microfilaments within fixed cells revealed enhanced formation of dendritic-like processes, microspikes and other dynamic actin based structures. To address the means by which c-erbB-2 over-expression might result in elevated fascin levels, we identified multiple perfect match TCF and NF-kappaB consensus sites in fascin's promoter and first intron, which appeared consistent with the greater endogenous transcriptional activities of TCF and NF-kappaB in c-erbB-2 over-expressing MDA-MB-435 cells. While such transcriptional modulation may occur in the context of the intact gene/chromatin, subsequent tests using reporter constructs did not support involvement of these signaling pathways. In conclusion, highly increased fascin levels were observed in MDA-MB-435 over-expressing c-erbB-2, likely contributing to these cells' altered actin dynamics, and increased cell motility and malignancy. Studies in progress aim to discern the means by which c-erbB-2 over-expression leads to transcriptional activation of the fascin gene.

Nuclear localization and cell cycle-specific expression of CtIP, a protein that associates with the BRCA1 tumor suppressor

The BRCA1 tumor suppressor has been implicated in a diverse spectrum of cellular processes, including transcriptional regulation, DNA repair, and cell cycle checkpoint control. CtIP was recently identified as a protein that associates with BRCA1 and two other nuclear factors, CtBP1 and Rb1. To understand the functions of CtIP, we have evaluated its biological properties with respect to those of BRCA1. Our results show that CtIP, like its associated factors, is predominantly a nuclear protein. A subset of the endogenous pool of CtIP polypeptides exists in a protein complex that includes both BRCA1 and the BRCA1-associated RING domain protein (BARD1). At the protein level, CtIP expression varies with cell cycle progression in a pattern identical to that of BRCA1. Thus, the steady-state levels of CtIP polypeptides, which remain low in resting cells and G(1) cycling cells, increase dramatically as dividing cells traverse the G(1)/S boundary. In contrast to BRCA1, however, the G(1)/S induction of CtIP expression is mediated primarily by post-transcriptional mechanisms. Finally, the interaction between CtIP and BRCA1 is shown to be stable in the face of genotoxic stress elicited by treatment with UV light, adriamycin, or hydrogen peroxide. Together, these results indicate that CtIP can potentially modulate the functions ascribed to BRCA1 in transcriptional regulation, DNA repair, and/or cell cycle checkpoint control.

Expression of cancer-related genes in human cells exposed to 60 Hz magnetic fields

Exposure to 60 Hz magnetic fields (MFs) may be a risk factor for human cancer. One mechanism through which MFs could influence neoplastic development is through alterations in the expression of cancer-related genes. Previous molecular studies of the action of MFs have measured effects on a limited number of genes. In the present studies, arrays containing cDNAs for 588 cancer-related genes were used to approach the hypothesis that the biological activity of MFs is mediated by alterations in gene expression. Cultures of normal (HME) and transformed (HBL-100) human mammary epithelial cells and human promyelocytic leukemia (HL60) cells were exposed to MFs at field strengths of 0, 0.01 or 1.0 mT for 24 h. Several genes were identified in MF-exposed cells whose expression was increased by at least twofold or decreased by 50% or more. However, no gene was found to be differentially expressed in each of three independent exposures for any cell type, and no relationship between exposure intensity and differential gene expression was found. These studies failed to identify a plausible genetic target for the action of MFs in human cells, and they provide no support for the hypothesis that MF exposure alters the expression of genes that are involved in cancer development.

Targets of extinction: identification of genes whose expression is repressed as a consequence of somatic fusion between cells representing basal and luminal mammary epithelial phenotypes

The use of somatic cell hybrids has led to an increased understanding of the ‘negative’ regulation of cellular phenotype. Using somatic cell hybrids constructed between human breast cells that represent differing stages of malignancy but also display differing phenotypes from the same tissue, we present experimental results suggesting that luminal epithelial characteristics are controlled by repressive mechanisms. Fusion of HBL 100 cells, non-tumorigenic and characteristic of the basal cell lineage, with MCF-7 or MDA-MB-468 malignant breast cancer cells, characteristic of the luminal lineage, resulted in hybrid cells that displayed the phenotype of the HBL 100 cells. Using representational difference analysis, a panel of genes whose expression was repressed in the hybrid between HBL 100 and MDA-MB-468 was identified. This analysis revealed markers of luminal epithelial cells to be repressed, including Ep-CAM, cytokeratin 19 and E-cadherin. These markers were found to be coordinately re-expressed in variant hybrid cells indicating that the observed repression is reversible. Integrin (alpha)(v)(beta)(3) expression was found to be in mutual exclusivity to the luminal epithelial markers, thereby revealing a bidirectional ‘switch’ in the pattern of gene expression in this system. Finally, the expression of Ep-CAM was found to be lost in heterokaryons produced by fusion of HBL 100 and MCF-7 or MDA-MB-468 cells suggesting that the extinction of this gene in hybrid cells is the consequence of a trans-acting factor(s) synthesized by the HBL 100 cells. These data suggest that a number of markers of luminal cell differentiation in the mammary gland can be controlled through negative mechanisms and that such control of phenotype is highly coordinated.

Resistance of HBL100 human breast epithelial cells to vitamin D action

Vitamin D analogs are effective inhibitors of breast cancer cell growth, but many breast cancer cell lines show various degrees of resistance to the growth inhibitory effect of vitamin D. In this study, we investigated the mechanism of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] resistance of the human breast epithelial cell line HBL100, which had been immortalized by Simian virus 40 (SV40) large T antigen. We determined the expression, DNA binding and transactivation activity of vitamin D3 receptor (VDR) in HBL100 and a vitamin D-sensitive ZR75-1 breast cancer cell line. Western blot analysis revealed a comparable expression of VDR gene in both cell lines. However, gel retardation assays demonstrated nuclear proteins from ZR75-1 cells but not from HBL100; cells expressed a 9-fold increase in the binding activity with a vitamin D response element (VDRE). Using a transient transfection assay, we showed that the VDRE was activated by 8-fold in ZR75-1. However, in HBL100 cells there was no activation observed in response to 1,25(OH)2D3. On the other hand, co-transfection of a VDR expression vector could restore 1,25(OH)2D3-induced VDRE transcription in HBL100 cells. Moreover, stable expression of VDR in HBL100 cells resulted in enhanced sensitivity of the cells to the growth inhibitory effect of 1,25(OH)2D3. Since CV-1 cells express very little endogenous VDR, the interactions of VDR and large T antigen were carried out in these cells. By transient co-transfection, we observed that expression of the large T antigen strongly inhibited 1,25(OH)2D3-induced VDRE transcriptional activity in a dose-dependent fashion in CV-1 cells. At 120 ng VDR concentration, the inhibition was completely reversed. Thus the loss of the growth inhibitory effect of vitamin D3 in HBL100 cells may be caused by the expression of the large T antigen in the cells, and provide further evidence that VDR is required for efficient growth inhibition by vitamin D3.

The C-terminal (BRCT) domains of BRCA1 interact in vivo with CtIP, a protein implicated in the CtBP pathway of transcriptional repression

The BRCA1 tumor suppressor encodes a polypeptide with two recognizable protein motifs: a RING domain near the N terminus and two tandem BRCT domains at the C terminus. Studies of tumor-associated mutations indicate that the RING and BRCT sequences are required for BRCA1-mediated tumor suppression. In addition, recent work has shown that BRCA1 is a potent regulator of RNA transcription and that the BRCT domains are also essential for this activity. Therefore, we used the Sos recruitment system to screen for proteins that bind this critical region of BRCA1. Our results show that the BRCT domains interact in vivo with CtIP, a protein originally identified on the basis of its association with the CtBP transcriptional co-repressor. This finding suggests that BRCA1 regulates gene expression, at least in part, by modulating CtBP-mediated transcriptional repression. Moreover, the in vivo interaction between BRCA1 and CtIP is completely ablated by each of three independent tumor-associated mutations affecting the BRCT motifs of BRCA1. These results indicate that the BRCA1-CtIP interaction may be required for tumor suppression by BRCA1.

BG-1 ovarian cell line: an alternative model for examining estrogen-dependent growth in vitro

Examination of estrogen-responsive processes in cell culture is used to investigate hormonal influence on cancer cell growth and gene expression. Most experimental studies have used breast cancer cell lines, in particular MCF7 cells, to investigate estrogen responsiveness. In this study we examined an ovarian cancer cell line, BG-1, which is highly estrogen-responsive in vitro. This observation, plus the fact that the cells are of ovarian rather than mammary gland origin, makes it an attractive alternative model. 17Beta-estradiol, epidermal growth factor, and insulin-like growth factorinduced proliferation of BG-1 and MCF7 cells. Viability was dependent on these growth factors in BG-1 cells, but not in MCF7 cells. Therefore, we examined the differences between these two cell lines with respect to estrogen and growth factor receptors. BG-1 cells have twice as many estrogen receptors as MCF7 cells, and BG-1 cells have higher insulin-like growth factor-1 and epidermal growth factor receptor levels than MCF7 cells. This may also explain why BG-1 cells proliferate 56% more robustly in serum and show more serum dependence in culture. In both BG-1 and MCF7 cells, epidermal growth factor receptor number is low (<20000/cell), while insulin-like growth factor-1 receptor level was highest in estrogen receptor positive cell lines. For example, insulin-like growth factor-1 receptor was higher in BG-1 and MCF7 cells than in estrogen receptor negative cells (HeLa > MDA-MB-435 > HBL100). In conclusion, BG-1 cells are an excellent model for understanding hormone responsiveness in ovarian tissue and an alternative for examining estrogen receptor-mediated and insulin-like growth factor-1/epidermal growth factor/estrogen cross-talk processes because of their sensitivity to these factors.

Production and oestrogen regulation of FGF1 in normal and cancer breast cells

To investigate the relationship between the FGF1 oestrogen regulation and the normal/cancer status of breast cells, we have studied FGF1 17beta-oestradiol regulation in normal, transformed and cancerous cells. Normal (NMEC), transformed (HBL-100) and cancerous (MCF-7, MDA-MB-231) human mammary epithelial cells express different levels of FGF1 mRNAs. Western blot analysis allowed us to characterize FGF1 as an 18 kDa form of this polypeptide. Using a neutralizing anti-FGF1 antibody we demonstrated that FGF1 is secreted by all mammary cells studied and stimulates their proliferation in an autocrine manner. We have examined the regulation of FGF1 mRNAs in response to 17beta-oestradiol. FGF1 mRNAs were upregulated in hormone-dependent NMEC but was not upregulated either in hormone-sensitive HBL-100 cells or in the hormone-dependent cancerous cell line MCF-7. However, enzyme linked immunosorbent assay indicated an increase of FGF1 protein in NMEC, HBL-100 and MCF-7 cells. We have also examined the 17beta-oestradiol regulation of the four alternatively spliced FGF1 mRNAs: 1.A, 1.B, 1. C and 1.D. Only 1.B transcripts were downregulated by 17beta-oestradiol in normal cells. These results show that 17beta-oestradiol regulates FGF1 mRNAs in a cell-specific manner, and that this regulation may be transcriptional or translational depending on cell phenotype. The specificity of oestradiol effects was checked using its receptor antagonist tamoxifen.

Structural cues from the tissue microenvironment are essential determinants of the human mammary epithelial cell phenotype

Historically, the study of normal human breast function and breast disorders has been significantly impaired by limitations inherent to available model systems. Recent improvements in human breast epithelial cell lines and three-dimensional (3-D)3 culture systems have contributed to the development of in vitro model systems that recapitulate differentiated epithelial cell phenotypes with remarkable fidelity. Molecular characterization of these human breast cell models has demonstrated that normal breast epithelial cell behavior is determined in part by the precise interplay that exists between a cell and its surrounding microenvironment. Recent functional studies of integrins in a human model system provide evidence to support the idea that the structural stability afforded by integrin-mediated cell-extracellular matrix interactions is an important determinant of normal cellular behavior, and that alterations in tissue structure can give rise to tumorigenic progression.

Serum p53 antibodies in patients with oral lesions: correlation with p53/HSP70 complexes

The functional significance of alterations in expression of tumour-suppressor gene p53 and 70-kDa heat-shock protein (HSP70) in eliciting p53-specific humoral response in oral-cancer patients is not yet known. In this study, p53 auto-antibodies were analyzed in sera from oral-cancer patients by immunoblotting and results were correlated with clinicopathological features of the patients as well as with the levels of HSP70, p53 and p53-HSP70 complexes in matched patients' tumour tissue, for determining their diagnostic/prognostic significance and relationship to survival. Circulating anti-p53 antibodies were observed in 7 of 30 cancer patients and 3 of 25 patients with pre-malignant lesions. Over-expression of p53 protein in matched oral lesions was observed in 22 of these 30 cancer patients and 14 of 25 patients with dysplastic lesions. No detectable levels of p53 protein or anti-p53 antibodies were observed in normal subjects (15 cases). Elevated levels of HSP70 were observed in 23 of these 30 oral tumours and 17 of 25 dysplastic lesions. All the anti-p53-antibody-seropositive cases showed elevated levels of p53 and HSP70 proteins, as well as formation of p53-HSP70 complexes, in matched dysplastic or malignant lesions, suggesting that these molecular alterations may be early events in oral tumorigenesis and are implicated in eliciting p53-specific humoral immune response in these patients. Anti-p53-antibody-seropositive cases showed poor prognosis and significantly decreased overall disease-free survival in comparison with the seronegative cases. Detection of circulating anti-p53 antibodies may serve as a useful non-invasive marker for identifying oral tumours having poor prognosis.

Cell cycle-dependent colocalization of BARD1 and BRCA1 proteins in discrete nuclear domains

Germ-line mutations of the BRCA1 gene predispose women to early-onset breast and ovarian cancer by compromising the gene's presumptive function as a tumor suppressor. Although the biochemical properties of BRCA1 polypeptides are not understood, their expression pattern and subcellular localization suggest a role in cell-cycle regulation. When resting cells are induced to proliferate, the steady-state levels of BRCA1 increase in late G1 and reach a maximum during S phase. Moreover, in S phase cells, BRCA1 polypeptides are hyperphosphorylated and accumulate into discrete subnuclear foci termed "BRCA1 nuclear dots." BRCA1 associates in vivo with a structurally related protein termed BARD1. Here we show that the steady-state levels of BARD1, unlike those of BRCA1, remain relatively constant during cell cycle progression. However, immunostaining revealed that BARD1 resides within BRCA1 nuclear dots during S phase of the cell cycle, but not during the G1 phase. Nevertheless, BARD1 polypeptides are found exclusively in the nuclear fractions of both G1- and S-phase cells. Therefore, progression to S phase is accompanied by the aggregation of nuclear BARD1 polypeptides into BRCA1 nuclear dots. This cell cycle-dependent colocalization of BARD1 and BRCA1 indicates a role for BARD1 in BRCA1-mediated tumor suppression.

The gene for the human interleukin-11 receptor alpha chain locus is highly homologous to the murine gene and contains alternatively spliced first exons

The gene for the murine interleukin-11 receptor alpha chain (mIL-11R alpha) contains two loci (1 and 2), of which locus 2 is restricted to only some mouse strains. Two alternatively spliced exons (1a and 1b) encode the 5' untranslated region (5'UTR) of the murine locus 1. We have characterized the gene for the human interleukin-11 receptor alpha chain locus (hIL-11R alpha), examined its expression by Northern analysis and determined its chromosomal location by fluorescence in situ hybridization. The presence of exon(s) encoding the 5'UTR and mapping of transcription initiation sites was determined by reverse-transcriptase polymerase chain reaction and 5' rapid amplification of cDNA ends (5'RACE) techniques. The human locus spanned 10 kilobasepairs (kb) and consisted of 14 exons. Two alternatively spliced first exons (1a and 1b) encoding the 5'UTR were identified and shared 76 and 73% nucleotide identity with murine exons 1a and 1b. Multiple transcription start sites were demonstrated for human exon 1a. The promoter regions of both human exons 1a and 1b did not display a canonical TATA box. A predominant 1.8 kb transcript for the hIL-11R alpha was present in heart, brain, skeletal muscle, lymph nodes, thymus, appendix, pancreas and foetal liver. The hIL-11R alpha gene was localized to chromosome 9p13. In summary, the hIL-11R alpha gene was highly related to locus 1 of the murine gene and there was no evidence of a second hIL-11R alpha locus.

Tumoral progression of human breast epithelial cells secreting FGF2 and FGF4

The human breast epithelial cell line HBL100 synthesizes and secretes FGF2, is able to grow in soft agar but is not tumorigenic in nude mice. Transfection of this cell line with the FGF4 gene led to its tumorigenic conversion in a dose-dependent manner as assessed by growth under serum-free conditions, growth in soft agar and growth as xenografts in nude mice. Clones of FGF4-transfected cells producing different amounts of FGF4 secreted similar quantities of FGF2. Exogenously added recombinant FGF4 stimulated growth of clones that do not express this growth factor, but did not affect growth of FGF4-producers. Neutralizing IgGs directed against FGF2 strongly inhibited growth of clones that do not produce FGF4, but did not affect growth of FGF4-producers, indicating that the latter are FGF2-independent. Cross-linking experiments done with 125I-FGF2 showed a down-regulation of FGF receptors from the cell surface of FGF4-expressing clones. Taken together, these results indicate that the FGF signalling pathway may be involved during tumoral progression of human breast epithelial cells and that there is a dose-dependent relationship between the quantity of FGF4 produced and tumor development.

Characterization of the estrogen receptor transfected MCF10A breast cell line 139B6

There has been increasing evidence which suggests that abnormal expression of the estrogen receptor (ER) protein in nonmalignant breast tissue may be important in the carcinogenic process. To examine the effects of ER expression in immortalized nonmalignant mammary epithelial cells, an expression vector containing human ER cDNA was transfected into the ER negative human breast cells, MCF10A. Characterization of a clone stably expressing ER, 139B6, provided evidence for the regulated synthesis of a functional ER capable of binding estradiol-17 beta (E2) and undergoing processing. Expression of the ER gene did not enable E2 to stimulate endogenous genes [progesterone receptor (PgR), pS2, cathepsin D and TGF alpha] which normally respond to estrogens in breast cancer cells. The ER in 139B6 cells was, however, capable of inducing expression of an ERE-regulated reporter gene, indicating its ability to interact with transcriptional machinery. Furthermore, cultures in log growth displayed a slight increase in doubling time in the presence of E2. These results indicate that ER expression alone is not sufficient to induce a transformed phenotype. Thus, the 139B6 cell line should provide a new model for determining what additional changes lead to increased growth potential in response to E2 and for exploring how E2 itself may help bring about changes leading to progression of preneoplastic breast epithelial cells.

Quantification of uPA receptor expression in human breast cancer cell lines by cRT-PCR

The conversion of plasminogen to active plasmin is thought to be a crucial step in the process of extracellular matrix degradation associated with metastatic spread. Activation of plasminogen is initiated by urokinase plasminogen activator (uPA). The binding of uPA to the uPA cell surface receptor (uPA-R) accelerates plasmin generation from plasminogen and localizes uPA activity to the cell surface. We investigated the mRNA-expression of uPA-R in 19 different human breast cancer cell lines. In a competitive reverse transcription polymerase chain reaction (cRT-PCR) we simultaneously co-amplified two different RNA templates bearing the same primer recognition sequences, the cell line RNA and a known amount of an in vitro synthesized uPA-R-RNA internal standard. We analyzed the two PCR products differing 50 bp in size by agarose gel electrophoresis and calculated the initial uPA-R-RNA template concentration from the relative intensities of the bands quantified by video densitometry. We grouped the investigated cell lines according to their in vitro invasiveness according to literature. Cell lines with a high potential of invasiveness showed a higher expression of uPA-R compared to those with a low potential of invasiveness (Student's t-test, p 0.04). In addition to that we compared the uPA-R mRNA levels with uPA-R, uPA, and PAI-1 protein levels in culture supernatants and cell lysates. The obtained results in breast cancer cell lines with different invasiveness and in benign epithelial cell lines revealed the complex cooperation of the urokinase type proteolytic pathway. uPA, uPA-R, and PAI-1 are to be considered as a diagnostic tool rather than assaying a particular molecule alone. Our findings support the hypothesis that the urokinase proteolytic pathway plays a central role in the acquisition of an invasive phenotype and favors its potential use as a prognostic marker in patients with breast cancer.

Critical centrifugal forces induce adhesion rupture or structural reorganization in cultured cells

Cultured epithelial cells were exposed to accelerations ranging from 9,000 to 70,000g for time periods of 5, 15, or 60 min, by centrifugation in a direction tangential to their plastic substrate. Three regimes describe the cellular response: (1) Cell morphology and density remain unaltered at forces below a threshold of about 10(-7) N; (2) Between this critical force and a second threshold of about 1.5 10(-7)N, the number of adherent cells decreases exponentially with time and acceleration, with no alteration of cell morphology. This behavior can be modeled by a constant probability of detaching and by an exponential distribution of cell-to-substrate adhesive forces; (3) Past the second threshold, cells that are still adherent exhibit elongated morphologies, the degree of elongation increasing linearly with the force. The fact that cells lose their vinculin-rich focal contacts past the first threshold and that cells cultured on gelatin-coated plastic show an increased resistance to detachment suggests a rupture of cell-to-substrate adhesions upon centrifugation. Immunofluorescent labeling of cells for actin and tubulin shows a reorganization of the cytoskeleton upon centrifugation, and treatment of cells with the drugs cytochalasin D and nocodazole demonstrates that cytoskeletal elements are actively involved in the structural deformation of cells past the second acceleration threshold, microtubules and microfilaments paying antagonistic roles.

Expression of the cyclin-dependent kinase inhibitors p16INK4, p15INK4B and p21WAF1/CIP1 in human breast cancer

Aberrant cyclin expression has been implicated in oncogenesis in a number of human cancers. Since altered function of regulators of cyclin-dependent kinase (CDK) activity other than cyclins, in particular CDK inhibitors, might play a similar role in oncogenesis, we examined the expression and regulation of the CDK inhibitors p16INK4, p15INK4B and p21WAF1/CIP1 in human breast cancer cell lines. Both the INK4 and INK4B genes were homozygously deleted in 3 cell lines, while INK4 alone was deleted in 2 cell lines. A further 2 cell lines displayed loss of an allele at this locus, and in 1 of these the remaining allele contained a mis-sense mutation within the coding region of the p16INK4 protein. The majority of cell lines examined, including 2 normal mammary epithelial cell strains, expressed low levels of INK4 mRNA and low or undetectable levels of INK4B mRNA. However, INK4 mRNA was expressed at high levels in 5 cell lines, and this was associated with deletion or inactivation of the retinoblastoma susceptibility gene product pRB but not with mutation of TP53. No deletions of the WAF1/CIP1 gene were observed, but WAF1/CIP1 mRNA levels were reduced in cell lines with TP53 mutation. Transfection of a p16INK4 expression vector into MDA-MB-231 cells lacking the INK4 gene failed to produce any p16INK4-expressing cell lines, suggesting that such cells were selected against in continuous culture. Despite the frequent deletion of INK4 in breast cancer cell lines, no evidence was obtained for INK4 deletions in DNA from 45 primary breast carcinomas. Thus, homozygous deletion of the INK4 gene appears to be a rare event in primary breast cancer.

Comparison between novel steroid-like and conventional nonsteroidal antioestrogens in inhibiting oestradiol- and IGF-I-induced proliferation of human breast cancer-derived cells

1. This study has two specific aims: (a) to compare the antioestrogenic activity of two steroidal analogues of 17 beta-oestradiol, the 7 alpha-alkylamide, ICI 164,384 and the 7 alpha-alkylsulphinylamide, ICI 182,780, with that of the triphenylethylene-derived compound 4OH-tamoxifen on a pool of human breast cancer cell lines (HBCCL) with a range of hormonal responsiveness and acquired anti-oestrogen resistance and (b) to investigate the ability of such antioestrogens to modulate the potent breast carcinoma growth-stimulatory activity of the 'IGF-I system'. 2. For the chemosensitivity investigations we used a long-term colorimetric and the short-term thymidine incorporation assay; we analysed IGF-I in conditioned media by a radioimmunoassay, IGF-I mRNA in the cells by RT-PCR and molecular species of IGF-I-binding proteins, secreted in conditioned media, by Western ligand blot. IGF-I receptors were assayed on cell monolayers by binding studies and by Scatchard analysis, we calculated KD, Bmax and sites/cell. 3. Our results indicate that ICI 182,780 and ICI 164,384 are 1.5-5.5 fold more potent than 4OH-tamoxifen in inhibiting the basal proliferation of oestrogen-receptor positive (ER+) breast cancer cell lines. Moreover we demonstrate the capacity of ICI 182,780 and ICI 164,384 to reduce, in a time-dependent fashion, oestrogen- and/or IGF-I-stimulated growth of ER+cell lines, possibly by negatively interfering with an IGF-I-like material secretion and IGF-I-receptor number. 4. Our data provide the first evidence that, on ER+human breast carcinoma cell lines, steroidal antioestrogens inhibit cell growth and modulate the IGF-I mitogenic system. The mechanism of this latter effect has yet to be identified.

In vitro karyotype evolution and cytogenetic instability in the non-tumorigenic human breast epithelial cell line HMT-3522

The "spontaneously" immortalized cell line HMT-3522, derived from a fibrocystic breast lesion, is used as a model for premalignant breast epithelium. During 205 passages the cytogenetic evolution was followed. The results were compared with our earlier results on oncogene expression and growth factor requirements. During in vitro growth, gain and loss of markers, loss of normal chromosomes, and duplication of the chromosome complement could be demonstrated. The variability increased during in vitro growth. This variability, probably created randomly, leads to cells with different growth capacities, from which sidelines may be selected and become stemlines. The karyotypic evolution (including polyploidization) demonstrated here may be a result of genetic instability and heterogeneity. Although tumorigenicity was not achieved, either due to lack of cancer-specific gene alterations or to lack of proper selection pressure, the results suggest an ongoing process towards malignancy.

EGF modulation of the ras-related rhoB gene expression in human breast-cancer cell lines

The mRNA levels of the ras-related human rhoA, rhoB and rhoC genes were studied in human breast-cancer cell lines (HBCal), and in normal and immortalized mammary epithelial cells (HMEC) by Northern blot analysis and in situ hybridization. In contrast to the ubiquitous rhoA and rhoC gene expression, dramatic variations in the mRNA level of the rhoB gene were evidenced. The rhoB mRNA level appeared to be inversely correlated to the amounts of the epidermal-growth-factor(EGF) receptors in these cells. The rhoB transcripts were detected at high levels in ZR75-1, MCF7, HSL 53, HSL 59, HSL 90, T47D and SKBR3 HBCal, at hardly detectable levels in BT 20, MDA-MB 231 and H466B HBCal and at intermediate levels in normal and immortalized breast epithelial cells. Rapid and transient induction of the rhoB transcription was observed after EGF treatment in serum-deprived MDA-MB231, T47D and immortalized epithelial cells. In contrast, no modulation of rhoB expression by EGF could be objectified in the MCF7 and ZR75-1 cell lines. Yet a normal function of EGF receptors was evidenced, since the immediate early gene c-fos was rapidly induced, suggesting a constitutive expression of rhoB in these cell lines bypassing the regulation by EGF. In human mammary epithelial cells, rhoB mRNA is rapidly and transiently induced with EGF concentrations known to stimulate cell proliferation. This suggests that the rhoB product might be involved in a cascade that initiates or promotes cell proliferation, and plays an important role in EGF-stimulated growth of breast normal and cancer cells.

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.

Interaction with basement membrane serves to rapidly distinguish growth and differentiation pattern of normal and malignant human breast epithelial cells

Normal human breast epithelial cells show a high degree of phenotypic plasticity in monolayer culture and express many traits that otherwise characterize tumor cells in vivo. Paradoxically, primary human breast carcinoma cells are difficult to establish in culture: most outgrowths arise from the normal tissue surrounding the tumor. These characteristics have posed major obstacles to the establishment of simple reliable criteria for mammary epithelial transformation in culture. In the present study, we show that a reconstituted basement membrane (BM) can be used to culture all normal human breast epithelial cells and a subset of human breast carcinoma cells. The two cell types can be readily distinguished by virtue of the ability of normal cells to reexpress a structurally and functionally differentiated phenotype within BM. Twelve specimens of normal breast tissue and 2 normal breast epithelial cell lines (total 14 samples) embedded in BM as single cells were able to form multicellular spherical colonies with a final size close to that of true acini in situ. Sections of mature spheres revealed a central lumen surrounded by polarized luminal epithelial cells expressing keratins 18 and 19 and sialomucin at the apical membrane. Significantly, two-thirds of normal spheres deposited a visible endogenous type IV collagen-containing BM even though they were in contact with exogenously provided BM. Growth was arrested completely within the same time period. In contrast, none of 6 carcinoma cell lines or 2 cultures of carcinoma from fresh samples (total 8 samples) responded to BM by growth regulation, lumen formation, correct polarity, or deposition of endogenous BM. These findings may provide the basis of a rapid assay for discriminating normal human breast epithelial cells from their malignant counterparts. Furthermore, we propose that the ability to sense BM appropriately and to form three-dimensional organotypic structures may be the function of a class of "suppressor" genes that are lost as cells become malignant.