Estradiol and EGF requirements for cell-cycle progression of normal human mammary epithelial cells in culture

In vitro culture and characterization of a mammary epithelial cell line from Chinese Holstein dairy cow

Background

The objective of this study was to establish a culture system and elucidate the unique characteristics of a bovine mammary epithelial cell line in vitro.

Methodology

Mammary tissue from a three year old lactating dairy cow (ca. 100 d relative to parturition) was used as a source of the epithelial cell line, which was cultured in collagen-coated tissue culture dishes. Fibroblasts and epithelial cells successively grew and extended from the culturing mammary tissue at the third day. Pure epithelial cells were obtained by passages culture.

Principal Findings

The strong positive immunostaining to cytokeratin 18 suggested that the resulting cell line exhibited the specific character of epithelial cells. Epithelial cells cultured in the presence of 10% FBS, supraphysiologic concentrations of insulin, and hydrocortisone maintained a normal diploid chromosome modal number of 2n = 60. Furthermore, they were capable of synthesizing β-casein (CSN2), acetyl-CoA carboxylase-α (ACACA) and butyrophilin (BTN1A1). An important finding was that frozen preservation in a mixture of 90% FBS and 10% DMSO did not influence the growth characteristics, chromosome number, or protein secretion of the isolated epithelial cell line.

Conclusions

The obtained mammary epithelial cell line had normal morphology, growth characteristics, cytogenetic and secretory characteristics, thus, it might represent an useful tool for studying the function of Chinese Holstein dairy cows mammary epithelial cell (CMECs).

Silibinin impairs constitutively active TGFalpha-EGFR autocrine loop in advanced human prostate carcinoma cells

PURPOSE

Epidermal growth factor (EGF) and transformation growth factor-alpha (TGFalpha) are potent mitogens that regulate proliferation of prostate cancer cells via autocrine and paracrine loops, and promote tumor metastasis. They exert their action through binding to the cell surface receptor, epidermal growth factor receptor (EGFR), and cause activation of Erk1/2 mediated mitogenic signaling in human prostate cancer (PCA) at both advanced and androgen-independent stages. Thus, we rationalized that inhibiting this mitogenic pathway could be useful in controlling advanced PCA growth.

METHODS

LNCaP and DU145 human PCA cells were treated with silibinin (100-200 microM) for different time points, and the levels of TGFalpha, activated signaling molecules (EGFR, Erk1/2 and Jnk1/2) and Erk1/2 kinase activity were analyzed employing ELISA, immunoprecipitation and/or immunoblotting techniques. The mRNA levels of TGFalpha were analyzed by RT-PCR.

RESULTS

Treatment of cells (LNCaP and DU145) with silibinin resulted in a decrease in TGFalpha protein at both secreted and cellular levels together with a decrease in its mRNA level. Silibinin also caused an inhibition of EGFR activation followed by that of Erk1/2 without any change in their protein levels. The kinase activity of Erk1/2 to Elk1 was also inhibited by silibinin at least in DU145 cells. In other study, silibinin caused strong inhibition of Jnk1/2 activation in LNCaP cells while in DU145 cells, a strong induction in Jnk1/2 activation was observed. These results suggest that silibinin impairs TGFalpha-EGFR-Erk1/2 signaling in both androgen-dependent (LNCaP) and -independent (DU145) advanced human prostate carcinoma cells.

CONCLUSIONS

This study, for the first time, identifies the inhibitory effect of silibinin on constitutively active TGFalpha-EGFR autocrine loop in advanced human PCA cells, which plausible contributes to the strong efficacy of silibinin in PCA prevention and intervention, as reported in recent studies.

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.

Divergent effect of TGFbeta1 on growth and proteolytic modulation of human prostatic-cancer cell lines

Plasminogen activators (PAs) play a key role in malignant transformation. PA secretion by tumoral cells is strongly correlated with their aggressive phenotype. Regulation of invasive potential by growth factors has been also demonstrated. This study was designed to investigate the effects of 5alpha-dihydrotestosterone (DHT), epidermal growth factor (EGF), transforming growth factor beta1 (TGFbeta1), retinoic acid and basic fibroblastic growth factor (bFGF) on cell growth and PA expression and secretion in DU145 and PC3 cells, 2 human prostatic-cancer cell lines. The proliferation of 2 cell lines was significantly increased only by EGF (about 30%), but decreased by TGFbeta1 (40% inhibition). However, EGF-treated cells showed significant enhancement (about 400%) of u-PA secretion. A similar effect was observed when cells were cultured with DHT (200%) and with TGFbeta1 (300%). Nevertheless, u-PA mRNA level in EGF-, TGFbeta1 - or DHT-treated cells was amplified only between 110 and 180% of control, suggesting that growth factors differently controlled the steps of PA expression. Furthermore, our results clearly showed the divergent effect of TGFbeta1, i.e., an inhibition of prostatic-cell-line growth accompanied by an increase in proteolytic activity.

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

The growth and differentiation of normal human mammary epithelial cells (HMEC) were studied after propagation of serial cultures from breast tissue biopsies from 42 mammoplasty patients. Cells were grown for up to 7 mo. in low calcium medium. HMEC cultures displayed heterogeneous growth patterns, according to the average doubling time of 44 +/- 6 h for 32 generations. Proliferation peaked at Day 30. HMEC maintained a normal karyotype and were organized in ductlike structures when cultured in collagen gel matrix. The cultures retained several phenotype traits of the epithelial lineage, including the expression of cytokeratins 18 and 19, specific mammary gland antigens, as shown by indirect HMEC immunostaining by the monoclonal antibodies DF3, EMA, 7B10, and 1BE12. Estrogen receptors were undetectable, whereas progesterone receptors were present at very low density. High-affinity cell surface receptors for epidermal growth factor (EGF) (Kd = 1.1 x 10(-10) M) were observed at a density of 50,000 to 100,000 sites per cell. Accordingly, [3H]thymidine incorporation in HMEC was optimally stimulated by EGF at concentrations of 10(-11) to 10(-10) M. HMEC were also seen to possess functional VIP receptors linked to the adenylate cyclase system, as we previously observed in seven human breast cancer cell lines. These results show that long-term cultures of HMEC provide useful models for studying the growth and differentiation of the normal human mammary gland, and the role of growth factors and hormones in these functions.