Gene expression profiling of breast cancers with emphasis of beta-catenin regulation

Meta-analysis identifies key genes and pathways implicated in Benzo[a]pyrene exposure response

INTRODUCTION

Benzo[a]pyrene (B[a]P) is a carcinogenic polycyclic aromatic hydrocarbon that poses significant risks to human health. B[a]P influences cellular processes via intricate interactions; however, a comprehensive understanding of B[a]P's effects on the transcriptome remains elusive. This study aimed to conduct a comprehensive analysis focused on identifying relevant genes and signaling pathways affected by B[a]P exposure and their impact on human gene expression.

METHODS

We searched the Gene Expression Omnibus database and identified four studies involving B[a]P exposure in human cells (T lymphocytes, hepatocellular carcinoma cells, and C3A cells). We utilized two approaches for differential expression analysis: the LIMMA package and linear regression. A meta-analysis was utilized to combine log fold changes (FC) and p-values from the identified studies using a random effects model. We identified significant genes at a Bonferroni-adjusted significance level of 0.05 and determined overlapping genes across datasets. Pathway enrichment analysis elucidated key cellular processes modulated by B[a]P exposure.

RESULTS

The meta-analysis revealed significant upregulation of CYP1B1 (log FC = 1.15, 95% CI: 0.51-1.79, P < 0.05, I2 = 82%) and ASB2 (log FC = 0.44, 95% CI: 0.20-0.67, P < 0.05, I2 = 40%) in response to B[a]P exposure. Pathway analyses identified 26 significantly regulated pathways, with the top including Aryl Hydrocarbon Receptor Signaling (P = 0.00214) and Xenobiotic Metabolism Signaling (P = 0.00550). Key genes CYP1A1, CYP1B1, and CDKN1A were implicated in multiple pathways, highlighting their roles in xenobiotic metabolism, oxidative stress response, and cell cycle regulation.

CONCLUSION

The results provided insights into the mechanisms of B[a]P toxicity, highlighting CYP1B1's key role in B[a]P bioactivation. The findings underscored the complexity of B[a]P's mechanisms of action and their potential implications for human health. The identified genes and pathways provided a foundation for further exploration and enhanced our understanding of the multifaceted biological activities associated with B[a]P exposure.

The role of Siah2 in tumorigenesis and cancer therapy

Seven in absentia homolog 2 (Siah2), an RING E3 ubiquitin ligases, has been characterized to play the vital role in tumorigenesis and cancer progression. Numerous studies have determined that Siah2 promotes tumorigenesis in a variety of human malignancies such as prostate, lung, gastric, and liver cancers. However, several studies revealed that Siah2 exhibited tumor suppressor function by promoting the proteasome-mediated degradation of several oncoproteins, suggesting that Siah2 could exert its biological function according to different stages of tumor development. Moreover, Siah2 is subject to complex regulation, especially the phosphorylation of Siah2 by a variety of protein kinases to regulate its stability and activity. In this review, we describe the structure and regulation of Siah2 in human cancer. Moreover, we highlight the critical role of Siah2 in tumorigenesis. Furthermore, we note that the potential clinical applications of targeting Siah2 in cancer therapy.

Resveratrol inhibits the growth of gastric cancer via the Wnt/β-catenin pathway

The inhibitory effect of resveratrol on the growth of gastric cancer cells through downregulation of the Wnt/β-catenin signaling pathway were studied. First we determined the effective concentration of resveratrol on the growth and proliferation of MGC-803 gastric cancer cells. Methylthiazolyl tetrazolium assay showed that resveratrol significantly inhibited the proliferation of MGC-803 cells in a dose-dependent manner. Resveratrol induced apoptotic morphological changes in MGC-803 cells. Reverse transcription-polymerase chain reaction and western blot analysis showed that resveratrol downregulated the expression of three important components of the Wnt signaling pathway, β-catenin, c-myc, and cyclin D1, at the mRNA and protein levels. Overall, resveratrol inhibits the growth of MGC-803 cells by inhibiting the Wnt signaling pathway. This study provides a new idea and direction for the antitumor mechanism of resveratrol.

Inhibitory effects of aesculetin on the proliferation of colon cancer cells by the Wnt/β-catenin signaling pathway

The inhibitory effect of aesculetin on the growth of colon cancer cell line SW480 through the Wnt/β-catenin signaling pathway was studied. The appropriate concentration of aesculetin was selected by cell counting kit-8 (CCK-8) assay, and the effect of aesculetin on the proliferation of SW480 cells was investigated by bromodeoxyuridine (BrdU) assay. The expression level of the messenger ribonucleic acid (mRNA) in β-catenin and Wnt signaling pathway target genes, c-Myc and cyclin D1, was detected by reverse transcription-polymerase chain reaction (RT-PCR). The expression levels of β-catenin, c-Myc and cyclin D1 proteins were detected by western blotting. CCK-8 detection results showed that compared with the control group, aesculetin effectively inhibited the proliferation of SW480 cells. BrdU detection results indicated that the number of BrdU positive cells in all the groups treated with drugs was significantly decreased. The of RT-PCR results suggested that aesculetin reduced the expression level of β-catenin mRNA and inhibited the expression of mRNA in the Wnt signaling pathway target genes, c-Myc and cyclin D1. Western blotting detection results revealed that aesculetin downregulated the expression level of β-catenin, c-Myc and cyclin D1 proteins. Aesculetin can inhibit tumor growth by suppressing the Wnt signaling pathway. This study provides a new idea and direction for the antitumor mechanism of aesculetin.

Mammary Development and Breast Cancer: A Wnt Perspective

The Wnt pathway has emerged as a key signaling cascade participating in mammary organogenesis and breast oncogenesis. In this review, we will summarize the current knowledge of how the pathway regulates stem cells and normal development of the mammary gland, and discuss how its various components contribute to breast carcinoma pathology.

Expression of Β-catenin and c-myc during human common bile duct development: a possible role in the morphogenesis of the common bile duct

β-catenin and c-myc play important roles in the development of tissues and organs. However, little is known about their expression patterns during the development of the human common bile duct. Immunohistochemistry was used to detect β-catenin and c-myc expression in common bile duct samples from postmortem tissues of 14 premature infants and 6 spontaneously aborted fetuses. The expression of β-catenin and c-myc was also analyzed by Western blot. The samples were divided into four groups based on the stage of human fetal development: 12, 13-27, 28-37, and >37 weeks. The Image-Pro Plus v. 6.0 image analysis software was used to calculate the mean qualifying score (MQS). At fetal stages 12, 13-27, 28-37, and >37 weeks, MQS of β-catenin were 612.52 ± 262.13, 818.38 ± 311.73, 706.33 ± 157.19, and 350.69 ± 110.19, respectively. There was a significant difference in MQS among the four groups (ANOVA, P=0.0155) and between the scores at >37 and 13-27 weeks (Student-Newman-Keuls, P<0.05). At fetal stages 12, 13-27, 28-37, and >37 weeks, the MQS of c-myc were 1376.64 ± 330.04, 1224.18 ± 171.66, 1270.24 ± 320.75, and 741.04 ± 219.19, respectively. There was a significant difference in MQS among the four groups (ANOVA, P=0.0087) and between the scores at >37 and 12 weeks, >37 and 13-27 weeks, and >37 and 28-37 weeks (all P<0.05, Student-Newman-Keuls). Western blots showed that β-catenin and c-myc expression were significantly higher in fetal than in postnatal control duct tissue (P<0.05). c-myc and β-catenin are involved in the normal development of the human common bile duct.

Expression and significance of Wnt signaling components and their target genes in breast carcinoma

The aim of this study was to investigate the expression of β-catenin, axin, cyclin D1 and c-myc, and their correlation with various clinicopathological factors of breast carcinoma. Using immunohistochemistry, the expression of axin, β-catenin, cyclin D1 and c-myc proteins was detected in 168 breast carcinomas and 40 normal breast tissue samples, as well as in 72 breast intraductal proliferative lesions. Correlations among the expression of these proteins with the clinicopathological factors of breast carcinomas were subsequently analyzed. Gene mutations of β-catenin (exon 3) in 44 cases of breast carcinoma were analyzed using polymerase chain reaction (PCR) followed by direct sequencing. In normal tissue, the epithelial cells demonstrated a marked membranous expression of β-catenin protein at cell-cell boundaries and positive axin expression; cyclin D1 and c-myc expression, however, were negative. The abnormal rate of β-catenin expression and the overexpression of cyclin D1 and c-myc were higher in breast carcinomas compared with breast cystic hyperplasia tissues. Positive axin expression levels were lower in breast carcinomas compared with breast intraductal proliferative lesions and normal breast tissues. Axin expression correlated inversely with tumor size, histological grade, clinical tumor, node, metastasis (TNM) stage and lymph node metastasis. The abnormal expression of β-catenin and the overexpression of cyclin D1 were correlated, and the overexpression of c-myc was correlated with tumor size, histological grade, clinical TNM stage and lymph node metastasis. The abnormal expression of β-catenin was correlated with the overexpression of cyclin D1, but not with the overexpression of c-myc. Lower levels of axin expression were correlated with higher levels of nuclear β-catenin expression. Mutations in the β-catenin gene were not detected in 44 cases of breast carcinoma. The abnormal expression of β-catenin may be key in the carcinogenesis and progression of human breast carcinoma by upregulating the expression of cyclin D1. The abnormal expression of β-catenin, the reduced expression of axin, and the overexpression of cyclin D1 and c-myc may be useful markers for determining metastasis, providing a prognosis for human breast carcinoma and for guiding treatment.

Expression of seven-in-absentia homologue 1 and hypoxia-inducible factor 1 alpha: novel prognostic factors of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an EBV-associated cancer. We analysed Siah1 expression as well as LMP1 and HIF1α expression by immuno-histochemical staining in 74 NPC biopsy specimens and found that the expression of Siah1 was significantly correlated with advanced tumour status and stage. Moreover, Siah1-positive and HIF1α-positive cases had significantly worse prognoses. The expression score for LMP1 was remarkably correlated with that of Siah1, whereas there was little correlation between LMP1 expression and the other markers evaluated. This is the first study to evaluate the pattern and clinical significance of Siah1 and HIF1α expression in NPC, and such an evaluation is valuable for identifying those patients at a high risk for a poor prognosis.

Biphasic dose-dependent effect of lithium chloride on survival of human hormone-dependent breast cancer cells (MCF-7)

Lithium, the first element of Group I in the periodic system, is used to treat bipolar psychiatric disorders. Lithium chloride (LiCl) is a selective inhibitor of glycogen synthase kinase-3β (GSK-3β), a serine/threonine kinase that regulates many cellular processes, in addition to its role in the regulation of glycogen synthase. GSK-3β is emerged as a promising drug target for various neurological diseases, type-2 diabetes, cancer, and inflammation. Several works have demonstrated that lithium can either inhibit or stimulate growth of normal and cancer cells. Hence, the present study is focused to analyze the underlying mechanisms that dictate the biphasic oncogenic properties of LiCl. In the current study, we have investigated the dose-dependent effects of LiCl on human breast cancer cells (MCF-7) by assessing the consequences on cytotoxicity and protein expressions of signaling molecules crucial for the maintenance of cell survival. The results showed breast cancer cells respond in a diverse manner to LiCl, i.e., at lower concentrations (1, 5, and 10 mM), LiCl induces cell survival by inhibiting apoptosis through regulation of GSK-3β, caspase-2, Bax, and cleaved caspase-7 and by activating anti-apoptotic proteins (Akt, β-catenin, Bcl-2, and cyclin D1). In contrast, at high concentrations (50 and 100 mM), it induces apoptosis by reversing these effects. Moreover, LiCl also alters the sodium and potassium levels thereby altering the membrane potential of MCF-7 cells. Thus it is inferred that LiCl exerts a dose-dependent biphasic effect on breast cancer cells (MCF-7) by altering the apoptotic/anti-apoptotic balance.

A genome-wide association study identifies a genetic variant in the SIAH2 locus associated with hormonal receptor-positive breast cancer in Japanese

In Japan, breast cancer is the most common cancer among women and the second leading cause of cancer death among women worldwide. To identify genetic variants associated with the disease susceptibility, we performed a genome-wide association study (GWAS) using a total of 1086 Japanese female patients with hormonal receptor-positive (HRP) breast cancer and 1816 female controls. We selected 33 single-nucleotide polymorphisms (SNPs) with suggestive associations in GWAS (P-value of <1 × 10(-4)) as well as 4 SNPs that were previously implicated their association with breast cancer for further replication by an independent set of 1653 cases and 2797 controls. We identified significant association of the disease with a SNP rs6788895 (P(combined) of 9.43 × 10(-8) with odds ratio (OR) of 1.22) in the SIAH2 (intron of seven in absentia homolog 2) gene on chromosome 3q25.1 where the involvement in estrogen-dependent diseases was suggested. In addition, rs3750817 in intron 2 of the fibroblast growth factor receptor 2 gene, which was reported to be associated with breast cancer susceptibility, was significantly replicated with P(combined) of 8.47 × 10(-8) with OR=1.22. Our results suggest a novel susceptibility locus on chromosome 3q25.1 for a HRP breast cancer.

Symmetric division versus asymmetric division: a tale of two coactivators

The decision for a stem cell to undergo a symmetric versus an asymmetric differentiation is probably the most critical cellular decision process in adults, as it probably underlies a large array of diseases, is associated with a decrease in tissue maintenance/homeostasis and the ability to repair properly, may mediate pathological processes such as cancer, fibrosis and neurodegeneration, and may be the underlying problem associated in general with aging. Interestingly and importantly, the decision to divide asymmetrically or symmetrically may be the major fundamental intrinsic difference between normal somatic stem and cancer stem cells. Based upon work done primarily in our laboratory over the past 10 years (both published and unpublished data), the article provides perspective on the critical importance of symmetric versus asymmetric divisions and the role of differential usage of the highly homologous coactivators Creb-binding protein (CBP) or p300 in the Wnt/catenin signaling cascade in stem cells and how they can be pharmacologically manipulated.

Increased SIAH expression predicts ductal carcinoma in situ (DCIS) progression to invasive carcinoma

Hyperactivated HER2/Neu/EGFR/RAS signaling is a major growth-promoting pathway known to drive cellular transformation and oncogenesis in breast cancers. HER2 amplification is detected in ~20% of all human breast cancer and is quite prevalent (up to 49%) in ductal carcinoma in situ (DCIS). The E3 ubiquitin ligase SIAH is considered a key downstream "gatekeeper" required for proper HER2/EGFR/RAS signal transduction. Formalin-fixed, paraffin-embedded resection specimens from 65 patients with DCIS treated with wide excision only were stained with an anti-SIAH antibody, and the percentage of tumor and normal adjacent tissue cells positive for SIAH nuclear staining were recorded. Statistical analysis was performed comparing SIAH staining in tumor cells to disease recurrence, histologic type, necrosis, hormone receptor status, and Her2/neu status, as well as nuclear grade. Correlation of SIAH expression in tumor cells with SIAH expression in normal adjacent tissue and age was also examined. Expression levels of SIAH in tumor cells was significantly higher in specimens from patients with recurrence (median = 19%) as compared to patients without recurrence (7%) (P < 0.001). There was also significantly increased SIAH expression in tumors with more aggressive features including comedo morphology (13.5% in comedo vs. 7% in other histologic types, P = 0.014). No significant association was observed between SIAH expression and estrogen receptor, progesterone receptor, and Her2/neu status. There was a significant correlation between SIAH expression in tumors and normal adjacent tissue (Spearman correlation = 0.58, P < 0.001) as well as between SIAH expression in normal adjacent tissue and patient age (Spearman correlation = -0.59, P < 0.001). No significant correlation was identified between patient age and SIAH expression in tumors (Spearman correlation = -0.23, P = 0.067). In conclusion, SIAH may represent a useful prognostic biomarker that predicts DCIS progression to invasive breast cancer.

Key signaling nodes in mammary gland development and cancer: β-catenin

β-Catenin plays important roles in mammary development and tumorigenesis through its functions in cell adhesion, signal transduction and regulation of cell-context-specific gene expression. Studies in mice have highlighted the critical role of β-catenin signaling for stem cell biology at multiple stages of mammary development. Deregulated β-catenin signaling disturbs stem and progenitor cell dynamics and induces mammary tumors in mice. Recent data showing deregulated β-catenin signaling in metaplastic and basal-type tumors suggest a similar link to reactivated developmental pathways and human breast cancer. The present review will discuss β-catenin as a central transducer of numerous signaling pathways and its role in mammary development and breast cancer.

Targeting Wnt signaling: can we safely eradicate cancer stem cells?

The Wnt signaling pathways have been conserved throughout evolution and regulate cell proliferation, morphology, motility, and fate during embryonic development. These pathways also play important roles throughout adult life to maintain homeostasis of tissues including skin, blood, intestine, and brain by regulating somatic stem cells and their niches. Aberrant regulation of the Wnt pathway leads to neoplastic proliferation in these same tissues. It has been suggested that Wnt signaling is also involved in the regulation of cancer stem cells (CSC), because there are many similarities in the signaling pathways that regulate normal adult stem cells and CSC. In this Perspective, we have focused on the Wnt/beta-catenin signaling pathway, which is the most intensively studied and best characterized Wnt signaling pathway. We provide an overview on the function of the Wnt/beta-catenin signaling pathway in CSC, and the possibility of the development of novel therapeutics to target this pathway.

Regulator of G-protein signaling (RGS) proteins in cancer biology

The regulator of G-protein signaling (RGS) family is a diverse group of multifunctional proteins that regulate cellular signaling events downstream of G-protein coupled receptors (GPCRs). In recent years, GPCRs have been linked to the initiation and progression of multiple cancers; thus, regulators of GPCR signaling are also likely to be important to the pathophysiology of cancer. This review highlights recent studies detailing changes in RGS transcript expression during oncogenesis, single nucleotide polymorphisms in RGS proteins linked to lung and bladder cancers, and specific roles for RGS proteins in multiple cancer types.

Breast cancer-derived Dickkopf1 inhibits osteoblast differentiation and osteoprotegerin expression: implication for breast cancer osteolytic bone metastases

Most breast cancer metastases in bone form osteolytic lesions, but the mechanisms of tumor-induced bone resorption and destruction are not fully understood. Although it is well recognized that Wnt/beta-catenin signaling is important for breast cancer tumorigenesis, the role of this pathway in breast cancer bone metastasis is unclear. Dickkopf1 (Dkk1) is a secreted Wnt/beta-catenin antagonist. In the present study, we demonstrated that activation of Wnt/beta-catenin signaling enhanced Dkk1 expression in breast cancer cells and that Dkk1 overexpression is a frequent event in breast cancer. We also found that human breast cancer cell lines that preferentially form osteolytic bone metastases exhibited increased levels of Wnt/beta-catenin signaling and Dkk1 expression. Moreover, we showed that breast cancer cell-produced Dkk1 blocked Wnt3A-induced osteoblastic differentiation and osteoprotegerin (OPG) expression of osteoblast precursor C2C12 cells and that these effects could be neutralized by a specific anti-Dkk1 antibody. In addition, we found that breast cancer cell conditioned media were able to block Wnt3A-induced NF-kappaB ligand reduction in C2C12 cells. Finally, we demonstrated that conditioned media from breast cancer cells in which Dkk1 expression had been silenced via RNAi were unable to block Wnt3A-induced C2C12 osteoblastic differentiation and OPG expression. Taken together, these results suggest that breast cancer-produced Dkk1 may be an important mechanistic link between primary breast tumors and secondary osteolytic bone metastases.

Downregulation of SIAH2, an ubiquitin E3 ligase, is associated with resistance to endocrine therapy in breast cancer

PURPOSE

In our microarray analysis we observed that Seven-in-Absentia Homolog 2 (SIAH2) levels were low in estrogen receptor (ER) positive breast tumors of patients resistant to first-line tamoxifen therapy. The aim of this study was to evaluate SIAH2 for its (a) predictive/prognostic value, and (b) functional role in endocrine therapy resistance.

PATIENTS AND METHODS

SIAH2 expression was measured with quantitative Real-Time-PCR (qRT-PCR) in 1205 primary breast tumor specimens and related to disease outcome. The functional role of SIAH2 was determined in human breast cancer cell lines ZR-75-1, ZR/HERc, and MCF7. Cell lines were treated with estrogen (E2), anti-estrogen ICI164.384 or epidermal growth factor (EGF). Moreover, MCF7 was treated with ICI164.384 after silencing SIAH2 expression.

RESULTS

SIAH2 was not prognostic in 603 lymph node negative patients who had not received adjuvant systemic therapy. In multivariate analysis of ER-positive tumors of 235 patients with recurrent disease, SIAH2 as continuous variable, significantly predicted first-line tamoxifen treatment failure (OR = 1.48; P = 0.05) and progression-free survival (PFS) (HR = 0.79; P = 0.007). Furthermore, in primary breast cancer patients treated with adjuvant tamoxifen, SIAH2 predicted metastasis-free survival (MFS) (HR = 0.73; P = 0.005). In vitro experiments showed that SIAH2 silencing in MCF7 cells resulted in resistance to ICI164.384-treatment when compared with mock silenced cells (P = 0.008). Interestingly, in ZR cells transfected with EGFR (ZR/HERc), SIAH2 expression was induced by E2 but downregulated by EGF.

CONCLUSION

In primary breast tumor specimens as well as in vitro low SIAH2 levels associated with resistance to endocrine therapy. Moreover, SIAH2 expression showed an opposite regulation by E2 and EGF.

Cadherins and catenins in breast cancer

Recent studies show that cadherins and catenins are hormonally regulated and carry out physiological roles during mammary development but have pathological effects when deregulated. E-cadherin expression is irreversibly lost in invasive lobular breast cancer (ILC). Animal models of ILC provide mechanistic insight, confirming that E-cadherin serves as both a tumor suppressor and an invasion suppressor in ILC. Ductal breast cancer involves complex, reversible, epigenetic modulation of multiple cadherins. Transcriptional regulators of E-cadherin have been identified that induce epithelial-to-mesenchymal transitions. Catenins are lost or mislocalized in tumors lacking cadherins. However, beta-catenin signaling is upregulated by numerous pathways in >50% of breast tumors and animal models suggest its oncogenic function in breast relates to its role in mammary progenitor cell expansion.

Kinase-inactive glycogen synthase kinase 3beta promotes Wnt signaling and mammary tumorigenesis

Recent studies have implicated ectopic activation of the Wnt pathway in many human cancers, including breast cancer. beta-catenin is a critical coactivator in this signaling pathway and is regulated in a complex fashion by phosphorylation, degradation, and nuclear translocation. Glycogen synthase kinase 3beta (GSK3beta) phosphorylation of the NH2-terminal domain of beta-catenin targets it for ubiquitination and proteosomal degradation. We hypothesized that expression of kinase-inactive GSK3beta (KI-GSK3beta) in mammary glands would function in a dominant-negative fashion by antagonizing the endogenous activity of GSK3beta and promoting breast cancer development. Consistent with this, we find that KI-GSK3beta stabilizes beta-catenin expression, catalyzes its localization to the nucleus, and up-regulates the downstream target gene, cyclin D1, in vitro. In vivo, transgenic mice overexpressing the KI-GSK3beta under the control of the mouse mammary tumor virus-long terminal repeat develop mammary tumors with overexpression of beta-catenin and cyclin D1. Thus, antagonism of GSK3beta activity is oncogenic in the mammary epithelium; mutation or pharmacologic down-regulation of GSK3beta could promote mammary tumors.

Gene expression analysis of cultured amniotic fluid cell with Down syndrome by DNA microarray

Complete or partial triplication of human chromosome 21 results in Down syndrome (DS). To analyze differential gene expressions in amniotic fluid (AF) cells of DS, we used a DNA microarray system to analyze 102 genes, which included 24 genes on chromosome 21, 28 genes related to the function of brain and muscle, 36 genes related to apoptosis, 4 genes related to extracellular matrix, 8 genes related to other molecular function and 2 house-keeping genes. AF cells were collected from 12 pregnancies at 16-18 weeks of gestation in DS (n=6) and normal (n=6) subjects. Our DNA microarray experiments showed that the expressions of 11 genes were altered by at least 2-folds in DS, as follows. Ten genes, COL6A1, CASP5, AKT2, JUN, PYGM, BNIP1, OSF-2, PRSS7, COL3A1, and MBLL were down-regulated and GSTT1 was only up-regulated. The differential expressions of GSTT1 and COL3A1 were further confirmed by semi-quantitative RT-PCR for each sample. The gene dosage hypothesis on chromosome 21 may explain the neurological and other symptoms of DS. However, our results showed that only two genes (COL6A1 and PRSS7), among 24 genes on chromosome 21, were down-regulated in the AF cells of DS. Our data may provide the basis for a more systematic identification of biological markers of fetal DS, thus leading to an improved understanding of pathogenesis for fetal DS.