Characterization of normal breast epithelial cells in primary cultures: differentiation and growth factor receptors studies

Distinctive Expression of MetastamiRs in Breast Cancer Mesenchymal Stem Cells Isolated from Solid Tumor

BACKGROUND

MSCs are a part of the tumor microenvironment, which secrete cytokines and chemokines. They can affect metastasis and the growth of tumors. metastamiRs are newly recognized regulatory elements of the metastasis pathway which are involved in epithelial-to-mesenchymal transition (EMT).

OBJECTIVE

In the present study, we aimed to assess the expression profile of metastamiRs in the context of MSCs in correlation with their invasion and migration power.

METHODS

Tumor-isolated BC-MSCs and normal human mammary epithelial cells (HMECs) along with MCF-7, MDA-MB231, and MCF-10A cells were prepared and confirmed for their identity. The cells were assessed for CD44+CD24¯ percentage, Oct-4, and Survivin expression. GEO, KEGG, and TCGA databases were investigated to detect differential miR-expressions. Real- time PCR for 13 miRs was performed using LNA primers. Ultimately, Transwell-Matrigel assays as used to assess the level of migration and invasion.

RESULTS

Our results indicated that some oncomiRs like miR-10b were upregulated in BC-MSCs, while the levels of miR-373 and miR-520c were similar to the MCF-10A. Generally, miR-200 family members were on lower levels compared to the other miR-suppressor (miR-146a, 146b, and 335). miR-31 and 193b were up-regulated in MCF-10A. The most invasiveness was observed in the MDA-MB231 cell line.

CONCLUSION

We have demonstrated that the miR-expression levels of BC-MSCs are somewhat in between MCF-7 and MDA-MB231 miR-expression levels. This could be the logic behind the moderate level of invasion in BC-MSCs. Therefore, miR-therapy approaches such as miR-mimic or antagomiRs could be used for BC-MSCs in clinical cancer therapy.

Differential prognostic impact of interleukin-34 mRNA expression and infiltrating immune cell composition in intrinsic breast cancer subtypes

Interleukin-34 (IL-34) is a ligand for the CSF-1R and has also two additional receptors, PTPRZ1 and syndecan-1. IL-34 plays a role in innate immunity, inflammation, and cancer. However, the role of IL-34 in breast cancer is still ill-defined. We analyzed IL-34 mRNA expression in breast cancer cell lines and breast cancer patients and applied established computational approaches (CIBERSORT, ESTIMATE, TIMER, TCIA), to analyze gene expression data from The Cancer Genome Atlas (TCGA). Expression of IL-34 was associated with a favorable prognosis in luminal and HER2 but not basal breast cancer patients. Gene expression of CSF-1 and CSF-1R was strongly associated with myeloid cell infiltration, while we found no or only weak correlations between IL-34, PTPRZ1, syndecan-1 and myeloid cells. In vitro experiments showed that tyrosine phosphorylation of CSF-1R, ERK, and FAK and cell migration are differentially regulated by IL-34 and CSF-1 in breast cancer cell lines. Collectively, our data suggest that correlation of IL-34 gene expression with survival is dependent on the molecular breast cancer subtype. Furthermore, IL-34 is not associated with myeloid cell infiltration and directly regulates breast cancer cell migration and signaling.

Characterization of immortalized human mammary epithelial cell line HMEC 2.6

Primary human mammary epithelial cells have a limited life span which makes it difficult to study them in vitro for most purposes. To overcome this problem, we have developed a cell line that was immortalized using defined genetic elements, and we have characterized this immortalized non-tumorigenic human mammary epithelial cell line to establish it as a potential model system. human mammary epithelial cells were obtained from a healthy individual undergoing reduction mammoplasty at SIU School of Medicine. The cells were transduced with CDK4R24C followed by transduction with human telomerase reverse transcriptase. Post all manipulation, the cells displayed a normal cell cycle phase distribution and were near diploid in nature, which was confirmed by flow cytometry and karyotyping. In vitro studies showed that the cells were anchorage dependent and were non-invasive in nature. The cell line expressed basal epithelial markers such as cytokeratin 7, CD10, and p63 and was negative for the expression of estrogen receptor and progesterone receptor. Upon G-band karyotyping, the cell line displayed the presence of a few cytogenic abnormalities, including trisomy 20 and trisomy 7, which are also commonly present in other immortalized mammary cell lines. Furthermore, the benign nature of these cells was confirmed by multiple in vitro and in vivo experiments. Therefore, we think that this cell line could serve as a good model to understand the molecular mechanisms involved in the development and progression of breast cancer and to also assess the effect of novel therapeutics on human mammary epithelial cells.

Relationship between Targeting Efficacy of Liposomes and the Dosage of Targeting Antibody Using Surface Plasmon Resonance

Surface plasmon resonance (SPR) was used in this research to investigate the targeting efficacy (i.e., the binding affinity) of antibody-modified liposomes. The results indicated that liposomes modified by targeting antibodies exhibited an increase in apparent binding affinity, a result attributed to the avidity effect. More specifically, the targeting effect improved as the surface density of the targeting antibody increased, an increase primarily attributed to the decrease of the dissociation rate. However, this trend stopped when the surface density reached a threshold of approximately 1.5 × 10(8) antibody/mm(2). This surface density was found to be quite consistent regardless of the liposome size and the type of targeting antibody. In addition, a traditional cell binding experiment was conducted to confirm the saturation point obtained from SPR.

Cyclosporine A inhibits breast cancer cell growth by downregulating the expression of pyruvate kinase subtype M2

The high proliferative rate of tumor cells leads to metabolic needs distinct from those of their normal counterparts. An embryonic- and tumor-specific isoform of the enzyme pyruvate kinase M2 (PKM2) is overexpressed in cancer cells to increase the use of glycolytic intermediates for macromolecular biosynthesis and tumor growth. We report that Cyclosporin A (CsA) can regulate the expression and activity of PKM2 in breast cancer cell lines MCF-7, MDA-MB-435 and MDA-MB-231. PKM2 was found to be highly expressed in the three breast cancer cell lines compared to normal primary breast cells. Treatment with CsA inhibited the viability of breast cancer cells in a time- and dose-dependent manner. CsA significantly downregulated the expression of PKM2 in breast cancer cells and decreased adenosine triphosphate (ATP) synthesis, which induced cancer cells to undergo necrosis. Furthermore, the growth suppression effect of CsA was impaired in MCF-7 cells when they were transfected with the PKM2 overexpression plasmid, suggesting that CsA was an effective inhibitor of PKM2-dependent proliferation of breast cancer cells. These results may provide new insights into the mechanism of CsA in cancer therapy.

The nanostructure effect on the adhesion and growth rates of epithelial cells with well-defined nanoporous alumina substrates

We systematically analyzed the adhesion and the proliferation of cells on various nanoporous alumina surfaces to understand the effects of nanostructured surfaces on cell behavior. Various nanoporous surfaces were fabricated using the anodizing method and characterized by atomic force microscopy and scanning electron microscopy. The adhesion rate and proliferation rate of cells as functions of pore size and depth were statistically investigated using a colorimetric method. The adhesion rate of cells was not affected by the depth of the nanoporous surface whereas the proliferation of cells dramatically increased when the aspect ratio of the nanopore was near unity. This phenomenon was further verified by comparing the change in roughness of the cytoplasmic layer of cells adhered on a nanoporous surface with that of a bare nanoporous surface. The proliferation of cells was also influenced by the pore size of the nanoporous surface because the nanostructure could control the interaction between extracellular matrix (ECM) molecules and the surface. In conclusion, the nanostructured surfaces affected cell adhesion and proliferation by increasing the surface area to which the cells could adhere, and the interactions between small ECM molecules were influenced by the sufficiently small structures of the nanosurface.

Raloxifene plus 17beta-estradiol inhibits proliferation of primary cultured vascular smooth muscle cells and human mammary endothelial cells via the janus kinase/signal transducer and activator of transcription3 cascade

Long-term use of estrogen replacement therapy increases the risk of breast cancer. Presently, we investigated the effects and mechanisms of Raloxifene, a second generation selective estrogen receptor modulator, plus 17beta-estradiol on the proliferation of primary cultured vascular smooth muscle cells (VSMC) and human mammary endothelial cells (HMEC). Raloxifene plus 17beta-estradiol inhibited angiotensin II-induced VSMC proliferation and rapid phosphorylation of STAT(3); these effects were blocked by AG490, the janus kinase/signal transducer and activator of transcription3 (JAK/STAT(3)) inhibitor. STAT(3) production was not affected. In primary cultured HMEC, immunofluorescence identified the ERbeta subtype, but not the ERalpha subtype, in the nucleus. Raloxifene plus 17beta-estradiol inhibited 17beta-estradiol-induced proliferation of HMEC. Western blot analysis established that Raloxifene attenuated the 17beta-estradiol-induced phosphorylation of STAT(3), and that this effect was blocked by AG490. We conclude that Raloxifene plus 17beta-estradiol inhibits the proliferation of VSMC and HMEC through the JAK/STAT(3) cascade, which in primary cultured HMEC may be implemented through ERbeta.

Myoepithelial cells: pathology, cell separation and markers of myoepithelial differentiation

Until recently the myoepithelial cell has been studied relatively little in terms of its role in breast cancer. A number of malignancies showing myoepithelial differentiation have been reported in the literature, although they are still thought to be relatively rare and only limited studies are published. As a result of recent expression profiling experiments, one type of tumor with myoepithelial features, the so-called 'basal' breast cancer, has received a renewed interest, although it has been known to pathologists for more than two decades. These tumors, which express markers of both luminal and myoepithelial cells, are now being studied using antibodies against some new molecules that have emerged from studies of sorted normal luminal and myoepithelial cells. These immunohistochemical data, combined with genomic studies, may lead to better identification and management of patients with 'basal' tumors.

Fidelity of the methylation pattern and its variation in the genome

The methylated or unmethylated status of a CpG site is copied faithfully from parental DNA to daughter DNA, and functions as a cellular memory. However, no information is available for the fidelity of methylation pattern in unmethylated CpG islands (CGIs) or its variation in the genome. Here, we determined the methylation status of each CpG site on each DNA molecule obtained from clonal populations of normal human mammary epithelial cells. Methylation pattern error rates (MPERs) were calculated based upon the deviation from the methylation patterns that should be obtained if the cells had 100% fidelity in replicating the methylation pattern. Unmethylated CGIs in the promoter regions of five genes showed MPERs of 0.018-0.032 errors/site/21.6 generations, and the fidelity of methylation pattern was calculated as 99.85%-99.92%/site/generation. In contrast, unmethylated CGIs outside the promoter regions showed MPERs more than twice as high (P < 0.01). Methylated regions, including a CGI in the MAGE-A3 promoter and DMR of the H19 gene, showed much lower MPERs than unmethylated CGIs. These showed that errors in methylation pattern were mainly due to de novo methylations in unmethylated regions. The differential MPERs even among unmethylated CGIs indicated that a promoter-specific protection mechanism(s) from de novo methylation was present.

Transforming growth factor beta 1 and sodium butyrate differentially modulate urokinase plasminogen activator and plasminogen activator inhibitor-1 in human breast normal and cancer cells

The effects of transforming growth factor beta 1 (TGF-beta1) and sodium butyrate on cell proliferation and the urokinase plasminogen activator (uPA) system were examined in normal human breast epithelial cells (HBECs) and in a breast cancer cell line, MDA-MB-231. In HBECs, TGF-beta1 inhibited cell proliferation and uPA activity, while it augmented plasminogen activator inhibitor-1 (PAI-1) antigen level. Sodium butyrate inhibited both cell proliferation and uPA activity but did not affect the level of PAI-1. In MDA-MB-231, TGF-beta1 had no effect on cell proliferation but increased uPA activity and PAI-1 antigen level; sodium butyrate inhibited both cell proliferation and uPA activity but had no effect on PAI-1 level. Moreover, in the presence of plasminogen, cell detachment could be modulated by the level of cell-associated uPA. Our results indicate (1) that the effects of TGF-beta1 on cell growth can be dissociated from its effects on the uPA/PAI system; (2) that, while TGF-beta1 is a potent inhibitor of cell proliferation and uPA activity in normal cells, it may promote invasion and metastasis of tumour cells by increasing uPA activity and PAI-1 levels; and (3) that sodium butyrate offers a potential approach to preventing tumour development by inhibiting both cell proliferation and invasion.

Statistical methods for estimating doubling time in in vitro cell growth

Doubling time has been widely used to represent the growth pattern of cells. A traditional method for finding the doubling time is to apply gray-scaled cells, where the logarithmic transformed scale is used. As an alternative statistical method, the log-linear model was recently proposed, for which actual cell numbers are used instead of the transformed gray-scaled cells. In this paper, I extend the log-linear model and propose the extended log-linear model. This model is designed for extra-Poisson variation, where the log-linear model produces the less appropriate estimate of the doubling time. Moreover, I compare statistical properties of the gray-scaled method, the log-linear model, and the extended log-linear model. For this purpose, I perform a Monte Carlo simulation study with three data-generating models: the additive error model, the multiplicative error model, and the overdispersed Poisson model. From the simulation study, I found that the gray-scaled method highly depends on the normality assumption of the gray-scaled cells; hence, this method is appropriate when the error model is multiplicative with the log-normally distributed errors. However, it is less efficient for other types of error distributions, especially when the error model is additive or the errors follow the Poisson distribution. The estimated standard error for the doubling time is not accurate in this case. The log-linear model was found to be efficient when the errors follow the Poisson distribution or nearly Poisson distribution. The efficiency of the log-linear model was decreased accordingly as the overdispersion increased, compared to the extended log-linear model. When the error model is additive or multiplicative with Gamma-distributed errors, the log-linear model is more efficient than the gray-scaled method. The extended log-linear model performs well overall for all three data-generating models. The loss of efficiency of the extended log-linear model is observed only when the error model is multiplicative with log-normally distributed errors, where the gray-scaled method is appropriate. However, the extended log-linear model is more efficient than log-linear model in this case.

Effect of stromal and epithelial cells derived from normal and tumorous breast tissue on the proliferation of human breast cancer cell lines in co-culture

Stromal and epithelial components surrounding neoplastic cells are believed to be important in tumor regulation. We have studied the effects of stromal and epithelial cells on the proliferation of a variety of breast-cancer epithelial cell lines. Co-culture experiments were performed in which the 2 cell types were separated by a microporous membrane. Under these conditions, fibroblasts from normal breast tissues inhibited the proliferation of MCF-7 cells, but not that of immortalized normal S2T2 cells. In contrast, fibroblasts from cancerous breast tissues did not influence the proliferation of the 2 cell lines tested. Conditioned media (CM) of breast fibroblasts derived from normal tissues were not able to affect MCF-7 cell growth, suggesting complex paracrine interactions between both cell types. Normal breast epithelial cells (NBEC) have also been tested for their ability to regulate the proliferation of breast-cancer epithelial cell lines. Co-culture experiments demonstrated that NBEC inhibited a variety of breast-cancer cell lines. CM from NBEC induced similar results and the inhibitory effect appeared to be specific for epithelial cells from tumorous breast. Moreover, CM from NBEC and normal fibroblasts were shown to contain more TGF beta 1 and amphiregulin than those of MCF-7 cells. We conclude that both the tissue origin and the target tumor cell's phenotype will determine the extent of proliferative response. More important, the tumor-cell growth inhibition induced by fibroblasts and epithelial cells of normal breast tissue may constitute a tumor-growth-regulatory mechanism.

A comparative study of cytokine gene transcripts in normal and malignant breast tissue and primary cell cultures derived from the same tissue samples

Using a differential centrifugation method followed by culture in selective medium, we have successfully isolated and maintained individual epithelial and stromal cells from normal (n = 10) and malignant (n = 6) human breast tissue and characterised their phenotype by immunocytochemistry. Further, we have studied expression of the cytokine genes IL-1beta, IL-6, IL-8 and TNF-beta in each cell fraction by RT-PCR and have compared these results with cytokine gene expression in tissue extracts from which primary cultures were derived. In breast tumours, there was near complete absence of IL-1beta in both whole tissue and cell fractions, and in normals it was present in only 3/10 tissue preparations, with increased expression in stromal (6/10) and epithelial (5/10) cell samples. IL-6 was constitutively expressed in all tumour-derived breast tissue samples but down-regulated in tumour cell cultures, with the opposite result in normal breast. Near identical levels of IL-8 expression were found throughout each preparation, irrespective of tissue origin. TNF-beta was expressed in all normal tissue samples, in 9/10 epithelial preparations but in only 6/10 stromal preparations. In tumours, TNF-beta was associated predominantly with whole tissue or stromal samples, with reduced expression in epithelial preparations. Our data confirm that primary cultures of normal and malignant human breast tissue can be successfully separated into epithelial and mesenchymal cell populations and their phenotype can be maintained in culture for up to 30 days. However, this cellular separation does alter the cytokine profiles; therefore, experimental findings with isolated cells should be treated with a caveat.

Biodistribution of iodine-125 tyramine transforming growth factor alpha antisense oligonucleotide in athymic mice with a human mammary tumour xenograft following intratumoral injection

The Watson-Crick base pairing rule provides the underlying principle for the antisense (AS) approach to inhibiting gene expression. Transforming growth factor alpha (TGFalpha) was the first growth factor to be associated with tumorigenesis, thus making the TGFalpha (mRNA) a potential target for AS therapy and offering the potential for monitoring of the progression of malignancy by non-invasive imaging with radiolabelled AS phosphodiester. Probe labelling and biodistribution were studied in the present report. A 23-mer oligonucleotide sequence was synthesized and grafted in 5' with a tyramine group which was further radioiodinated. The radiolabelled AS was injected intratumorally in mammary tumour-bearing BALB/c mice (3 weeks after inoculation of 7.10(6)NS2T2A mammary cells). Biodistribution was monitored by sequential scintigraphy and organ radioactivity after autopsy. The 5' tyramine group allowed specific and stable radiolabelling of the AS with 125I. The 125I AS oligonucleotide was rapidly cleared from the tumour by intestine and kidneys. Four hours after intratumoral injection, 6.5%+/-1.5% of the dose was retained in the tumour as non-degraded 125I AS. It is concluded that 5' tyraminylated AS provides information on the biodistribution of AS oligonucleotide following intratumoral injection. These data will contribute to the pharmacology of AS oligonucleotides which can be used for therapy.

Differential expression of VIP/PACAP receptor genes in breast, intestinal, and pancreatic cell lines

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are structurally-related neuropeptides that function as trophic factors in addition to their more classical roles as neurotransmitters. Binding and molecular cloning studies have shown that their actions are mediated by receptors encoded by at least three different genes. VIP binding has been demonstrated on many tumor types, and radiolabeled VIP has recently been used as a novel method to localize intestinal tumors in humans and their sites of metastasis. To determine the receptor subtype and level of gene expression, we screened breast, intestinal, and pancreatic, cell lines by Northern blot analysis. Breast lines expressed VIP/PACAP1 receptor mRNA levels comparable to intestinal lines, in agreement with the studies showing particularly high VIP binding in these tumors and their derived cell lines. Pancreatic cell lines expressed mRNA for several receptor types. This extends the potential utility of VIP and PACAP in the localization of tumors, and because VIP and PACAP may regulate the growth rate of some tumors by autocrine or other mechanisms, the identification of receptor subtypes on these lines sets the stage for studies in which the activity of these individual receptors in growth and other processes can be investigated.

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.

EGF receptor expression, regulation, and function in breast cancer

Epidermal growth factor receptor (EGFR) overexpression correlates with both loss of estrogen receptor (ER) and poor prognosis in breast cancer. Interestingly, in normal breast EGFR appears to be expressed more frequently than in malignant tissue, and there may be a different relationship between ER and EGFR. A variety of cellular regulators, such as EGF, TGF alpha, phorbol esters, and steroid hormones, are capable of altering the level of EGFR expression in breast cells. However, much work remains to be done on the mechanistic details of EGFR regulation in this disease. The significance of EGFR as an oncogene in breast cancer is compounded by its potential interactions with other oncogenes such as c-erbB-2 and c-myc. Additionally, several recent studies have placed EGFR prominently in the signal transduction pathway, demonstrating that the EGFR-ligand system may play important roles throughout the course of malignant progression in breast cancer.