Clinical significance of promoter hypermethylation of RASSF1A, RARbeta2, BRCA1 and HOXA5 in breast cancers of Indian patients

Promoter hypermethylation of genes is implicated in the pathogenesis of many cancers, including breast cancer. Herein, we analyzed the promoter methylation status of a panel of critical growth regulatory genes, RASSF1A, RARbeta2, BRCA1 and HOXA5, in 54 breast cancers and 5 distant normal breast tissues of Indian patients. The methylation data were correlated with clinicopathological characteristics and hormone receptor status to determine the impact of methylation in breast carcinogenesis. Promoter hypermethylation of RASSF1A was observed in 39/54 (72%), HOXA5 in 36/54 (67%), BRCA1 in 15/54 (28%) and RARbeta2 in 8/54 (15%) breast cancers. Our most significant findings were the association of RASSF1A methylation with nodal metastasis (p=0.05); and RARbeta2 methylation with age (all tumors in patients in the older age group were methylated, p=0.04). Further, the interactions between DNA methylation and hormone receptor biology in breast cancer cells are beginning to be clearly understood. In this context the association of HOXA5 methylation with loss of ERalpha (p=0.009) is noteworthy.     

LncRNA HOXA11‐AS promotes hepatocellular carcinoma progression by repressing miR‐214‐3p

Accumulating studies supported that lncRNAs played important roles in tumorigenesis. LncRNA HOXA11‐AS was a novel lncRNA that has been proved to involved in several tumours. However, the role of HOXA11‐AS in the development of hepatocellular carcinoma (HCC) remains to be explained. In our study, we showed that HOXA11‐AS expression was up‐regulated in the HCC tissues, and the higher expression of HOXA11‐AS was associated with the advanced stage in the HCC samples. In addition, we indicated that the expression of HOXA11‐AS was up‐regulated in HCC cell lines (Hep3B, SMMC‐7721, MHCC97‐H and BEL‐7402) compared with normal liver cell lines (HL‐7702). Overexpression of HOXA11‐AS promoted HCC proliferation and invasion and induced the epithelial‐mesenchymal transition (EMT) and knockdown of HOXA11‐AS suppressed the HCC cell proliferation and invasion. However, we showed that miR‐214‐3p expression was down‐regulated in the HCC tissues and cell lines. Ectopic expression of miR‐214‐3p suppressed HCC cell proliferation and invasion. Furthermore, we indicated that overexpression of HOXA11‐AS decreased the miR‐214‐3p expression and the expression of miR‐214‐3p was negatively related with the HOXA11‐AS expression in HCC samples. Ectopic expression of HOXA11‐AS increased HCC proliferation and invasion and induced EMT through inhibiting miR‐214‐3p expression. These data suggested that HOXA11‐AS/miR‐214‐3p axis was responsible for development of HCC.     

Steroid receptors and proliferation in the human breast

Despite recent gains in our knowledge of the hormonal control of proliferation and differentiation in the rodent mammary gland, the factors regulating these processes in the human are poorly understood. We have developed a model in which intact normal human breast tissue is grafted subcutaneously into adult female athymic nude mice and treated with oestrogen (E) and/or progesterone (P) at human physiological serum levels. We have shown that (i) E and not P is the major epithelial cell mitogen in the adult non-pregnant, non-lactating breast, (ii) E induces progesterone receptor (PR) expression and (iii) PR expression is maximally induced at low E concentrations while a higher amount of E is required to stimulate proliferation. These data raised the question of whether one cell type demonstrated two different responses to the two different E concentrations or whether PR expression and proliferation occurred in separate cell populations. Using dual label immunofluorescence, we showed that steroid receptor expression and proliferation (Ki67 antigen) are detected in separate cell populations in normal human breast epithelium, and that cells expressing the oestrogen receptor-alpha (ERalpha) invariably contained the PR. We also reported that this separation between steroid receptor expression and proliferation observed in the normal human epithelium is disrupted at an early stage in breast tumourigenesis. One interpretation supported by our recent findings is that some ERalpha/PR-positive epithelial cells are quiescent breast stem cells that act as "steroid hormone sensors". Such hormone sensor cells might secrete positive or negative paracrine/juxtacrine factors dependent on the prevailing E or P concentration to influence the proliferative activity of adjacent ERalpha/PR-negative epithelial cells.     

Isolation and characterization of human mammary stem cells

Since stem cells are present throughout the lifetime of an organism, it is thought that they may accumulate mutations, eventually leading to cancer. In the breast, tumours are predominantly oestrogen and progesterone receptor-positive (ERalpha/PR+). We therefore studied the biology of ERalpha/PR-positive cells and their relationship to stem cells in normal human mammary epithelium. We demonstrated that ERalpha/PR-positive cells co-express the putative stem cell markers p21(CIP1/WAF1), cytokeratin (CK) 19 and Musashi-1 when examined using dual label immunofluorescence on tissue sections. Next, we isolated a Hoechst dye-effluxing 'side population' (SP) from the epithelium using flow cytometry and demonstrated them to be undifferentiated cells by lack of expression of myoepithelial and luminal cell-specific antigens such as CALLA and MUC1. Epithelial SP cells were shown to be enriched for the putative stem cell markers p21(CIP1/WAF1), Musashi-1 and ERalpha/PR-positive cells. Lastly, SP cells, compared to non-SP, were highly enriched for the capacity to produce colonies containing multiple lineages in 3D basement membrane (Matrigel) culture. We conclude that breast stem cells include two populations: a primitive ERalpha/PR-negative stem cell necessary for development and a shorter term ERalpha/PR-positive stem cell necessary for adult tissue homeostasis during menstrual cycling. We speculate these two basic stem cell types may therefore be the cells of origin for ERalpha-positive and -negative breast tumours.     

The role and proposed mechanism by which oestradiol 17β-hydroxysteroid dehydrogenase regulates breast tumour oestrogen concentrations

Synthesis of the biologically active oestrogen, oestradiol, within breast tumours makes an important contribution to the high concentrations of oestrogens which are present in malignant breast tissues. In breast tumours, oestrone is preferentially converted to oestradiol by the Type I oestradiol 17β-hydroxysteroid dehydrogenase (E2DH). Several growth factors, such as insulin-like growth factor Type I, and cytokines, such as Tumour Necrosis Factor (TNF), have been shown to stimulate E2DH activity in MCF-7 breast cancer cells. As little is known about the regulation of Type I E2DH expression and activity in other breast cancer cell lines, the expression and activity of this enzyme was examined in other oestrogen receptor positive and also oestrogen receptor negative breast cancer cell lines. As it is possible that E2DH activity may be limited by co-factor availability, the effects of exogenous co-factors on enzyme activity in these cell lines was also investigated. For T47D and BT20 breast cancer cells, the addition of exogenous co-factors was found to enhance enzyme activity. TNF, in addition to stimulating E2DH activity in MCF-7 cells, also increased activity in T47D and MDA-MB-231 cells, although to a lesser extent than in MCF-7 cells. An investigation of signalling pathways involved in the regulation of E2DH activity revealed that stimulation of both the protein kinase C (PKC) and PKA pathways may be involved in regulation of E2DH activity. As several growth factors and cytokines have now been found to be involved in regulating E2DH activity, the role that macrophages and lymphocytes have in supplying these factors and the mechanism by which these factors may stimulate tumour growth, is also reviewed.     

Epigenetic reprogramming of breast cancer cells by valproic acid occurs regardless of estrogen receptor status

Estrogen receptors (ERs) are a recognized prognostic factor and therapeutic target in breast cancer. The loss of ER expression relates to poor prognosis, poor clinical outcome and impairs the use of anti-estrogenic treatment. Histone deacetylase inhibitors are candidate drugs for cancer therapy. Among them, valproic acid (VPA) is a long used and safe anti-epileptic drug. We studied the biological consequences of the chromatin remodeling action of VPA in a normal human mammary epithelial cell line and in ERalpha-positive and ERalpha-negative breast cancer cell lines. In these cells and regardless of their ER status, VPA-induced cell differentiation, as shown by increased milk lipids production, decreased expression of the CD44 antigen and growth arrest in the G(0)-G(1) phase of the cell cycle. These effects were accompanied by decreased Rb phosphorylation, hyperacetylation of the p21(WAF1/CIP1) gene promoter and increased p21 protein expression. Only in breast cancer cells, cyclin B1 expression was decreased and the cells accumulated also in G(2). ERalpha expression decreased in ERalpha-positive, increased in ERalpha-negative and was unchanged in normal mammary epithelial cells, as did the expression of progesterone receptor, a physiological ERalpha target. VPA decreased the expression of the invasiveness marker pS2 in ERalpha-positive breast cancer cells, but did not cause its re-expression in ERalpha-negative cells. Overall, these data suggest that in both ERalpha-positive and -negative malignant mammary epithelial cells VPA reprograms the cells to a more differentiated and "physiologic" phenotype that may improve the sensitivity to endocrine therapy and/or chemotherapy in breast cancer patients.     

p53 protein expression and oestrogen and progesterone receptor status in invasive ductal breast carcinomas

p53 protein expression and oestrogen and progesterone receptor status in invasive ductal breast carcinomas The p53 protein expression and oestrogen and progesterone receptors status was investigated in correlation to the grade of malignancy of primary breast carcinomas. Our material constituted imprints from surgical biopsies of 75 invasive ductal breast cancer cases. The p53 protein expression was investigated immunocytologically using the monoclonal antibody p53 DO-7 (DAKO). A biochemical DCC method was applied for the detection of oestrogen and progesterone receptors for all tumours. Fifty-one percent of breast cancer cases were p53 protein positive. A statistically significant association of p53 protein expression and high tumour grade was found (chi2=23.72, d.f.=2, P < 0.001). A statistically significant association was also found between oestrogen and progesterone receptor positive cases and the grade of malignancy (P < 0.001). A negative association between p53 protein expression and oestrogen (ER) and progesterone receptors (PgR) positivity was found. From our results it appears that it is possible to distinguish from grade II tumours two subgroups of cases, one with low malignancy potential and p53 (-), ER (+), PgR (+), and another subgroup with high malignancy potential and phenotype p53 (+), ER (-), PgR (-). The last subset of patients could actually benefit from adjuvant therapy.     

Reduction in serum IL-6 after vacination of breast cancer patients with tumour-associated antigens is related to estrogen receptor status

Elevated serum IL-6 concentrations have been associated with poor prognosis in a variety of cancers, and decreases in serum IL-6 concentrations have been reported after chemotherapy. We have demonstrated that serum IL-6 concentrations are elevated in breast cancer patients [normal women 0.7 +/- 2.5 pg/ml (n=36), breast cancer patients 38.3 +/- 138.7 pg/ml (n = 111)]. After vaccination of breast cancer patients with a combination of tumour-associated antigens and biological adjuvants (IL-2 and GM-CSF), the concentration of IL-6 decreased significantly (P<0.05) to 8.1 +/- 14.6 pg/ml (n=85). Other studies have shown that oestrogen suppresses IL-6 production in oestrogen receptor positive breast cancer cells. We have demonstrated that the decrease in IL-6 associated with vaccination is related to the oestrogen receptor status of the tumours from breast cancer patients, as a decrease in IL-6 from 124.0 +/- 267.5 pg/ml (n=26) to 6.2 +/- 11.0 pg/ml (n=34) only occurs in patients with oestrogen receptor negative tumours. The IL-6 concentration in breast cancer patients with oestrogen receptor positive tumours remained unchanged (9.5 pg/ml before vaccination, and 9.3 pg/ml after vaccination). These results suggest that postmenopausal women with oestrogen receptor negative breast cancers, who do not respond well to either hormonal therapy with tamoxifen or adjuvant chemotherapy, may have a significant response to vaccination with autologous tumour-associated antigens.     

Epigenetic mechanisms regulate the prostaglandin E receptor 2 in breast cancer

The increase in local oestrogen production seen in oestrogen receptor positive (ER+) breast cancers is driven by increased activity of the aromatase enzyme. CYP19A1, the encoding gene for aromatase, is often overexpressed in the oestrogen-producing cells of the breast adipose fibroblasts (BAFs) surrounding an ER+ tumour, and the molecular processes underlying this upregulation is important in the development of breast-specific aromatase inhibitors for breast cancer therapy. Prostaglandin E2 (PGE2), a factor secreted by tumours, is known to stimulate CYP19A1 expression in human BAFs. The hormonal regulation of this process has been examined; however, what is less well understood is the emerging role of epigenetic mechanisms and how they modulate PGE2 signalling. This present study characterises the epigenetic processes underlying expression of the prostanoid receptor EP2 in the context of ER+ breast cancer. Sodium bisulphite sequencing of CpG methylation within the promoter region of EP2 revealed that an inverse correlation existed between methylation levels and relative EP2 expression in breast cancer cell lines MDA-MB-231, MCF7 and MCF10A but not in HS578t and T47D. Inhibition of DNA methylation with 5-aza-2'-deoxycytidine (5aza) and histone deacetylation with Trichostatin A (TSA) resulted in upregulation of EP2 mRNA in all cell lines with varying influences of each epigenetic process observed. Expression of EP2 was detected in human BAFs despite a natively methylated promoter, and this expression was further increased upon 5aza treatment. An examination of 3 triple negative, 3 ductal carcinoma in situ and 3 invasive ductal carcinoma samples revealed that there was no change in EP2 promoter methylation status between normal and cancer associated stroma, despite observed differences in relative mRNA levels. Although EP2 methylation status is inversely correlated to expression levels in established breast cancer cell lines, we could not identify that such a correlation existed in tumour-associated stroma cells.     

Oestrogen receptor gene structure and function in breast cancer

The mechanisms underlying loss of oestrogen responsiveness in breast cancer are not well-defined. Potential mechanisms include loss of receptor expression, alterations in the oestrogen receptor (ER) gene producing proteins with abnormal function, or changes to receptor-dependent or -independent pathways controlling cell proliferation. Examination by Southern analysis of the ER gene in a series of ER-negative and -positive breast tumour biopsies failed to provide evidence of gross rearrangements and in only only one of thirty seven tumour DNA samples was significant gene amplification observed. No restriction fragment length polymorphisms were detected for the restriction enzymes EcoRI, Pst I or Hind III. Methylation of the ER gene as assessed by Hpa II and Msp I restriction enzyme digests varied between tumours but the degree of methylation was not correlated with levels of expression of the receptor protein. Similar findings applied in a series of ER-negative and -positive breast cancer cell lines and clonal lines of MCF-7 cells, which were developed as an in vitro model for the acquisition of oestrogen and antioestrogen resistance. In this model there was no evidence that changes to ER receptor function and/or structure at the level of the ER gene, mRNA, ligand binding, and ability to induce progesterone receptor might account for the development of hormone resistance. However, the ability of ER to interact with a DNA sequence containing the vitellogenin promoter oestrogen response element, as assessed by gel retardation assay, was impaired in the clone showing the greatest degree of oestrogen and antioestrogen resistance.     

Correlation of interleukin 6 with interleukin 1alpha in human mammary tumours, but not with oestrogen receptor expression

The authors hypothesized that IL-6 production by breast tumour tissues would correlate with OR-positivity, as only those tumours that contain oestrogen receptors (OR) and use oestrogen as a mitogen would benefit from locally increased oestrogen. IL-6 increases the activity of the 17beta-oxidoreductase, which converts oestrone to oestradiol, a process that may contribute to the increased concentration of oestrogen around breast tumours. IL-1alpha upregulates IL-6 production; therefore, the correlation between IL-1alpha and IL-6 immunoreactivity and OR-positivity in paraffin-embedded human breast tumours was further investigated.The results indicate IL-6 immunoreactivity in 40 of 66 paraffin embedded breast tumour specimens, a finding which did not correlate with the clinical evaluation of oestrogen receptor positivity (P=0.32 by Fisher's exact test). However, there was a correlation between IL-6 and IL-1alpha immunoreactivity (P<0.05). To study an in vitro model for this phenomenon, the IL-6 immunoreactivity in available cell lines was tested. Surprisingly, no production of IL-6 protein or mRNA could be detected in any of the cell lines, and this did not change with IL-1alpha stimulation. Therefore, none of the cell lines apparently reflected the immunological potential observed in the majority of surgical specimens.