Reactivation of epigenetically silenced HER4/ERBB4 results in apoptosis of breast tumor cells

Experimental and clinical data support a growth inhibitory role for HER4 in breast cancer. Clinically HER4 expression is extinguished during breast tumorigenesis supporting a tumor suppressor function for HER4, however, a molecular mechanism to explain the selective loss of HER4 expression has remained elusive. Epigenetic mechanisms, for example, aberrant gene promoter hypermethylation, have been shown to ablate tumor suppressor gene expression in breast carcinomas. We identified a CpG island within the HER4 promoter and show by pyrosequencing of bisulfite-treated DNA an inverse correlation between HER4 expression and the extent of promoter methylation. Treatment of the HER4-negative BT20 cell line with the DNA demethylating agent 5-aza-2′-deoxycytidine (DAC)-enhanced HER4 expression, confirming a role for DNA methylation in suppressed HER4 expression. DAC treatment to reactive HER4 expression in combination with the HER4 ligand heregulin-β1 (HRG) resulted in apoptosis of BT20 cells providing a novel therapeutic strategy for triple-negative tumors. The BT20 cells were rescued from apoptosis when preincubated with HER4 small interfering RNA, thereby confirming a role for HER4 in DAC/HRG-induced apoptosis. We verified HER4 promoter methylation in primary breast carcinomas and detected a significant increase in HER4 promoter methylation in HER4-negative breast tumors (P<0.001). Furthermore, increased levels of HER4 promoter methylation were significantly associated with worse patient prognosis (P=0.0234). Taken together, our data support a tumor suppressor function for HER4, which is epigenetically suppressed in breast tumors through promoter hypermethylation

SFRP1 reduction results in an increased sensitivity to TGF-β signaling

Background Transforming growth factor (TGF)-β plays a dual role during mammary gland development and tumorigenesis and has been shown to stimulate epithelial-mesenchymal transition (EMT) as well as cellular migration. The Wnt/β-catenin pathway is also implicated in EMT and inappropriate activation of the Wnt/β-catenin signaling pathway leads to the development of several human cancers, including breast cancer. Secreted frizzled-related protein 1 (SFRP1) antagonizes this pathway and loss of SFRP1 expression is frequently observed in breast tumors and breast cancer cell lines. We previously showed that when SFRP1 is knocked down in immortalized non-malignant mammary epithelial cells, the cells (TERT-siSFRP1) acquire characteristics associated with breast tumor initiating cells. The phenotypic and genotypic changes that occur in response to SFRP1 loss are consistent with EMT, including a substantial increase in the expression of ZEB2. Considering that ZEB2 has been shown to interact with mediators of TGF-β signaling, we sought to determine whether TGF-β signaling is altered in TERT-siSFRP1 cells. Methods Luciferase reporter assays and real-time PCR analysis were employed to measure TGF-β transcriptional targets. Western blot analysis was used to evaluate TGF-β-mediated ERK1/2 phosphorylation. Migration chamber assays were utilized to quantify cellular migration. TERT-siSFRP1 cells were transfected with Stealth RNAi™ siRNA in order to knock-down the expression of ZEB2. Results TERT-siSFRP1 cells exhibit a significant increase in both TGF-β-mediated luciferase activity as well as TGF-β transcriptional targets, including Integrin β3 and PAI-1. Phosphorylation of ERK1/2 is increased in TERT-siSFRP1 cells in response to enhanced TGF-β signaling. Furthermore, when the TGF-β pathway is blocked with a TGF-βR antagonist (LY364947), cellular migration is significantly hindered. Finally, we found that when ZEB2 is knocked-down, there is a significant reduction in the expression of exogeneous and endogenous TGF-β transcriptional targets and cellular migration is impeded. Conclusions We demonstrate that down-regulation of SFRP1 renders mammary epithelial cells more sensitive to TGF-β signaling which can be partially ameliorated by blocking the expression of ZEB2

Expression and prognostic significance of THBS1, Cyr61 and CTGF in esophageal squamous cell carcinoma

<p>Abstract</p> <p>Background</p> <p>Thrombospondin1 (THBS1), cystene-rich protein 61 (Cyr61) and connective tissue growth factor (CTGF) are all involved in the transforming growth factor-beta (TGF-β) signal pathway, which plays an important role in the tumorigenesis. The purpose of this study is to explore the expression and prognostic significance of these proteins in esophageal squamous cell carcinoma (ESCC).</p> <p>Methods</p> <p>We used immunohistochemistry and western blotting to examine the expression status of THBS1, Cyr61 and CTGF in ESCC. Correlations of THBS1, Cyr61 and CTGF over-expressions with various clinicopathologic factors were also determined by using the Chi-square test or Fisher's exact probability test. Survival analysis was assessed by the Kaplan-Meier analysis and the log-rank test. Relative risk was evaluated by the multivariate Cox proportional hazards model.</p> <p>Results</p> <p>THBS1, Cyr61 and CTGF were all over-expressed in ESCC. THBS1 over-expression was significantly associated with TNM stage (<it>P </it>= 0.029) and regional lymph node involvement (<it>P </it>= 0.026). Kaplan-Meier survival analysis showed that over-expression of THBS1, Cyr61 or CTGF was related to poor survival of ESCC patients (<it>P </it>= 0.042, <it>P </it>= 0.020, <it>P </it>= 0.018, respectively). Multivariate Cox analysis demonstrated that Cyr61 and CTGF were independent factors in prognosis of ESCC.</p> <p>Conclusion</p> <p>Cyr61, CTGF and THBS1 were all over-expressed in ESCC and might be new molecular markers to predict the prognosis of ESCC patients.</p

Heterogeneity of mammary lesions represent molecular differences

BACKGROUND: Human breast cancer is a heterogeneous disease, histopathologically, molecularly and phenotypically. The molecular basis of this heterogeneity is not well understood. We have used a mouse model of DCIS that consists of unique lines of mammary intraepithelial neoplasia (MIN) outgrowths, the premalignant lesion in the mouse that progress to invasive carcinoma, to understand the molecular changes that are characteristic to certain phenotypes. Each MIN-O line has distinguishable morphologies, metastatic potentials and estrogen dependencies. METHODS: We utilized oligonucleotide expression arrays and high resolution array comparative genomic hybridization (aCGH) to investigate whole genome expression patterns and whole genome aberrations in both the MIN-O and tumor from four different MIN-O lines that each have different phenotypes. From the whole genome analysis at 35 kb resolution, we found that chromosome 1, 2, 10, and 11 were frequently associated with whole chromosome gains in the MIN-Os. In particular, two MIN-O lines had the majority of the chromosome gains. Although we did not find any whole chromosome loss, we identified 3 recurring chromosome losses (2F1-2, 3E4, 17E2) and two chromosome copy number gains on chromosome 11. These interstitial deletions and duplications were verified with a custom made array designed to interrogate the specific regions at approximately 550 bp resolution. RESULTS: We demonstrated that expression and genomic changes are present in the early premalignant lesions and that these molecular profiles can be correlated to phenotype (metastasis and estrogen responsiveness). We also identified expression changes associated with genomic instability. Progression to invasive carcinoma was associated with few additional changes in gene expression and genomic organization. Therefore, in the MIN-O mice, early premalignant lesions have the major molecular and genetic changes required and these changes have important phenotypic significance. In contrast, the changes that occur in the transition to invasive carcinoma are subtle, with few consistent changes and no association with phenotype. CONCLUSION: We propose that the early lesions carry the important genetic changes that reflect the major phenotypic information, while additional genetic changes that accumulate in the invasive carcinoma are less associated with the overall phenotype

Metastatic canine mammary carcinomas can be identified by a gene expression profile that partly overlaps with human breast cancer profiles

<p>Abstract</p> <p>Background</p> <p>Similar to human breast cancer mammary tumors of the female dog are commonly associated with a fatal outcome due to the development of distant metastases. However, the molecular defects leading to metastasis are largely unknown and the value of canine mammary carcinoma as a model for human breast cancer is unclear. In this study, we analyzed the gene expression signatures associated with mammary tumor metastasis and asked for parallels with the human equivalent.</p> <p>Methods</p> <p>Messenger RNA expression profiles of twenty-seven lymph node metastasis positive or negative canine mammary carcinomas were established by microarray analysis. Differentially expressed genes were functionally characterized and associated with molecular pathways. The findings were also correlated with published data on human breast cancer.</p> <p>Results</p> <p>Metastatic canine mammary carcinomas had 1,011 significantly differentially expressed genes when compared to non-metastatic carcinomas. Metastatic carcinomas had a significant up-regulation of genes associated with cell cycle regulation, matrix modulation, protein folding and proteasomal degradation whereas cell differentiation genes, growth factor pathway genes and regulators of actin organization were significantly down-regulated. Interestingly, 265 of the 1,011 differentially expressed canine genes are also related to human breast cancer and, vice versa, parts of a human prognostic gene signature were identified in the expression profiles of the metastatic canine tumors.</p> <p>Conclusions</p> <p>Metastatic canine mammary carcinomas can be discriminated from non-metastatic carcinomas by their gene expression profiles. More than one third of the differentially expressed genes are also described of relevance for human breast cancer. Many of the differentially expressed genes are linked to functions and pathways which appear to be relevant for the induction and maintenance of metastatic progression and may represent new therapeutic targets. Furthermore, dogs are in some aspects suitable as a translational model for human breast tumors in order to identify prognostic molecular signatures and potential therapeutic targets.</p

p53 Target Gene SMAR1 Is Dysregulated in Breast Cancer: Its Role in Cancer Cell Migration and Invasion

Tumor suppressor SMAR1 interacts and stabilizes p53 through phosphorylation at its serine-15 residue. We show that SMAR1 transcription is regulated by p53 through its response element present in the SMAR1 promoter. Upon Doxorubicin induced DNA damage, acetylated p53 is recruited on SMAR1 promoter that allows activation of its transcription. Once SMAR1 is induced, cell cycle arrest is observed that is correlated to increased phospho-ser-15-p53 and decreased p53 acetylation. Further we demonstrate that SMAR1 expression is drastically reduced during advancement of human breast cancer. This was correlated with defective p53 expression in breast cancer where acetylated p53 is sequestered into the heterochromatin region and become inaccessible to activate SMAR1 promoter. In a recent report we have shown that SMAR1 represses Cyclin D1 transcription through recruitment of HDAC1 dependent repressor complex at the MAR site of Cyclin D1 promoter. Here we show that downmodulation of SMAR1 in high grade breast carcinoma is correlated with upregulated Cyclin D1 expression. We also established that SMAR1 inhibits tumor cell migration and metastases through inhibition of TGFβ signaling and its downstream target genes including cutl1 and various focal adhesion molecules. Thus, we report that SMAR1 plays a central role in coordinating p53 and TGFβ pathways in human breast cancer

Transforming Growth Factor β Signaling Pathway Associated Gene Polymorphisms May Explain Lower Breast Cancer Risk in Western Indian Women

Transforming growth factor β1 (TGFB1) T29C and TGF β receptor type 1 (TGFBR1) 6A/9A polymorphisms have been implicated in the modulation of risk for breast cancer in Caucasian women. We analyzed these polymorphisms and combinations of their genotypes, in pre menopausal breast cancer patients (N = 182) and healthy women (N = 236) from western India as well as in breast cancer patients and healthy women from the Parsi community (N = 48 & 171, respectively). Western Indian women were characterized by a higher frequency of TGFB1*C allele of the TGF β T29C polymorphism (0.48 vs 0.44) and a significantly lower frequency of TGFBR1*6A allele of the TGFBR1 6A/9A polymorphism (0.02 vs 0.068, p<0.01) as compared to healthy Parsi women. A strong protective effect of TGFB1*29C allele was seen in younger western Indian women (<40 yrs; OR = 0.45, 95% CI 0.25–0.81). Compared to healthy women, the strikingly higher frequencies of low or intermediate TGF β signalers in patients suggested a strong influence of the combination of these genotypes on the risk for breast cancer in Parsi women (for intermediate signalers, OR = 4.47 95%CI 1.01–19.69). The frequency of low signalers in Parsi healthy women, while comparable to that reported in Europeans and Americans, was three times higher than that in healthy women from western India (10.6% vs 3.3%, p<0.01). These observations, in conjunction with the low incidence rate of breast cancer in Indian women compared to White women, raise a possibility that the higher frequency of TGFB1*29C allele and lower frequency of TGFBR1*6A allele may represent important genetic determinants that together contribute to a lower risk of breast cancer in western Indian women

Molecular profiling of cervical cancer progression

Most cancer patients die of metastatic or recurrent disease, hence the importance to identify target genes upregulated in these lesions. Although a variety of gene signatures associated with metastasis or poor prognosis have been identified in various cancer types, it remains a critical problem to identify key genes as candidate therapeutic targets in metastatic or recurrent cancer. The aim of our study was to identify genes consistently upregulated in both lymph node micrometastases and recurrent tumours compared to matched primary tumours in human cervical cancer. Taqman Low-Density Arrays were used to analyse matched tumour samples, obtained after laser-capture microdissection of tumour cell islands for the expression of 96 genes known to be involved in tumour progression. Immunohistochemistry was performed for a panel of up- and downregulated genes. In lymph node micrometastases, most genes were downregulated or showed expressions equal to the levels found in primary tumours. In more than 50% of lymph node micrometastases studied, eight genes (AKT, BCL2, CSFR1, EGFR1, FGF1, MMP3, MMP9 and TGF-β) were upregulated at least two-fold. Some of these genes (AKT and MMP3) are key regulators of epithelial–mesenchymal transition in cancer. In recurrent tumours, almost all genes were upregulated when compared to the expression profiles of the matched primary tumours, possibly reflecting their aggressive biological behaviour. The two genes showing a consistent downregulated expression in almost all lymph node metastases and recurrent tumours were BAX and APC. As treatment strategies are very limited for metastatic and recurrent cervical cancer, the upregulated genes identified in this study are potential targets for new molecular treatment strategies in metastatic or recurrent cervical cancer

Mouse models of breast cancer metastasis

Metastatic spread of cancer cells is the main cause of death of breast cancer patients, and elucidation of the molecular mechanisms underlying this process is a major focus in cancer research. The identification of appropriate therapeutic targets and proof-of-concept experimentation involves an increasing number of experimental mouse models, including spontaneous and chemically induced carcinogenesis, tumor transplantation, and transgenic and/or knockout mice. Here we give a progress report on how mouse models have contributed to our understanding of the molecular processes underlying breast cancer metastasis and on how such experimentation can open new avenues to the development of innovative cancer therapy