Methylation-associated silencing of SFRP1 with an 8p11-12 amplification inhibits canonical and non-canonical WNT pathways in breast cancers

Detection of complex chromosome rearrangements using optical genome mapping

Chromosomal structural variations (SVs) are a main cause of human genetic disease. Currently, karyotype, chromosomal microarray analysis (CMA), and fluorescent in situ hybridization (FISH) form the backbone of current routine diagnostics (CRD). These methods have their own limitations. CRD cannot identify cryptic balanced SVs and complex SVs even if these techniques were performed either simultaneously or in a sequential manner. Optical genome mapping (OGM) is a novel technology that can identify several classes of SVs with higher resolution, but studies on the applicability of OGM and its comparison with CRD are inadequate for difficult and complicated chromosomal SVs are lacking. Herein, seven patients with definite complicated SVs involving at least two breakpoints (BPs) were recruited for this study. The results of BPs and SVs from OGM were compared with those from CRD. The results showed that all BPs of five samples and partial BPs of two samples were detected by OGM. The undetected BPs were all close to the repeat-rich gap region. Besides, OGM also detected additional SVs including a cryptic balanced translocation, two additional complex chromosomal rearrangement (CCR). OGM yielded the additional information, such as the orientation of acentric fragments, BP positions, and genes mapped in the BP region for all the cases. The accuracy of additional SVs and BPs detected by OGM was verified by FISH panel and next-generation sequencing and Sanger sequencing. Taken together, OGM exhibit a better performance in detecting chromosomal SVs compared to the CRD. We suggested that OGM method should be utilized in the clinical examination to improve the efficiency and accuracy of genetic disease diagnosis, supplemented by FISH or karyotyping to compensate for the SVs in the repeat-rich gap region if necessary.

SFRP1 Expression is Inversely Associated With Metastasis Formation in Canine Mammary Tumours

BACKGROUND

Canine mammary tumours (CMTs) are the most frequent tumours in intact female dogs and show strong similarities with human breast cancer. In contrast to the human disease there are no standardised diagnostic or prognostic biomarkers available to guide treatment. We recently identified a prognostic 18-gene RNA signature that could stratify human breast cancer patients into groups with significantly different risk of distant metastasis formation. Here, we assessed whether expression patterns of these RNAs were also associated with canine tumour progression.

METHOD

A sequential forward feature selection process was performed on a previously published microarray dataset of 27 CMTs with and without lymph node (LN) metastases to identify RNAs with significantly differential expression to identify prognostic genes within the 18-gene signature. Using an independent set of 33 newly identified archival CMTs, we compared expression of the identified prognostic subset on RNA and protein basis using RT-qPCR and immunohistochemistry on FFPE-tissue sections.

RESULTS

While the 18-gene signature as a whole did not have any prognostic power, a subset of three RNAs: Col13a1, Spock2, and Sfrp1, together completely separated CMTs with and without LN metastasis in the microarray set. However, in the new independent set assessed by RT-qPCR, only the Wnt-antagonist Sfrp1 showed significantly increased mRNA abundance in CMTs without LN metastases on its own (p = 0.013) in logistic regression analysis. This correlated with stronger SFRP1 protein staining intensity of the myoepithelium and/or stroma (p < 0.001). SFRP1 staining, as well as β-catenin membrane staining, was significantly associated with negative LN status (p = 0.010 and 0.014 respectively). However, SFRP1 did not correlate with β-catenin membrane staining (p = 0.14).

CONCLUSION

The study identified SFRP1 as a potential biomarker for metastasis formation in CMTs, but lack of SFRP1 was not associated with reduced membrane-localisation of β-catenin in CMTs.

Disruption of ZNF334 promotes triple-negative breast carcinoma malignancy through the SFRP1/ Wnt/β-catenin signaling axis

Zinc-finger proteins (ZNFs) constitute the largest transcription factor family in the human genome. The family functions in many important biological processes involved in tumorigenesis. In our research, we identified ZNF334 as a novel tumor suppressor of triple-negative breast cancer (TNBC). ZNF334 expression was usually reduced in breast cancerv (BrCa) tissues and TNBC cell lines MDA-MB-231 (MB231) and YCCB1. We observed that promoter hypermethylation of ZNF334 was common in BrCa cell lines and tissues, which was likely responsible for its reduced expression. Ectopic expression of ZNF334 in TNBC cell lines MB231 and YCCB1 could suppress their growth and metastatic capacity both in vitro and in vivo, and as well induce cell cycle arrest at S phase and cell apoptosis. Moreover, re-expression of ZNF334 in TNBC cell lines could rescue Epithelial-Mesenchymal Transition (EMT) process and restrain stemness, due to up-regulation of SFRP1, which is an antagonist of Wnt/β-catenin signaling. In conclusion, we verified that ZNF334 had a suppressive function of TNBC cell lines by targeting the SFRP1/Wnt/β-catenin signaling axis, which might have the potentials to become a new biomarker for diagnosis and treatment of TNBC patients.

A MicroRNA Derived From Schistosoma japonicum Promotes Schistosomiasis Hepatic Fibrosis by Targeting Host Secreted Frizzled-Related Protein 1

Schistosomiasis remains a serious parasitic disease, which is characterized by granulomatous inflammation and hepatic fibrosis. MicroRNAs derived from parasites can regulate host genes and cell phenotype. Here, we showed that a miRNA derived from S. japonicum (Sja-miR-1) exists in the hepatic stellate cells (HSCs) of mice infected with the parasite and up-regulates the expression of collagens and α-SMA by targeting secreted frizzled-related protein 1 (SFRP1). A vector-mediated delivery of Sja-miR-1 into naive mice led to hepatic fibrogenesis in the mice. Accordingly, inhibition of Sja-miR-1 in the infected mice led to reduction of the parasite-induced hepatic fibrosis. The mechanism behind the Sja-miR-1-mediated activation of HSC could be through targeting SFRP1 to regulate the Wnt/β-catenin pathway. These findings reveal that parasite-derived small non-coding RNAs are implicated in cross-species regulation of host pathological process and persistent inhibition of Sja-miR-1 may provide a therapeutic potential for the parasite diseases.

Exosomal miR-196a-1 promotes gastric cancer cell invasion and metastasis by targeting SFRP1

Aim: To investigate the role of exosomal miRNAs on gastric cancer (GC) metastasis. Materials & methods: miRNA expression profiles of exosomes with distinct invasion potentials were analyzed using miRNA microarray and validated by quantitative real-time PCR. In vitro and in vivo experiments assessed the role of exosomal miR-196a-1 in GC's metastasis. Results: High expression level of exosomal miR-196a-1 expression was significantly associated with poor survival in GC. Exosomes that contained miR-196a-1 were secreted from high-invasive GC cells. Ectopic miR-196a-1 expression promoted invasion of low-invasive GC cells by targeting SFRP1. Conclusion: miR-196a-1 was delivered from high-invasive GC into low-invasive GC cells via exosomes and promoted metastasis to the liver in vitro and in vivo.

Silencing microRNA-27a inhibits proliferation and invasion of human osteosarcoma cells through the SFRP1-dependent Wnt/β-catenin signaling pathway

Osteosarcoma is the most common malignant tumor of bone with a high potential for metastasis. Importantly, microRNA-27a (miR-27a) is involved in the progression of osteosarcoma. The present study aims to discuss the effects of miR-27a and its target gene secreted frizzled related protein 1 (SFRP1) on proliferation and invasion of human osteosarcoma cells via Wnt/β-catenin signaling pathway. The expression of miR-27a and SFRP1 in osteosarcoma tissues and cells was detected, followed by identification of their relations. Subsequently, miR-27a mimic, miR-27a inhibitor, or siRNA against SFRP1 were introduced into cells (HOS and U2OS) to investigate their role in cell proliferation and invasion. The expression of Wnt/β-catenin signaling pathway-related gene was analyzed to further uncover the regulatory mechanism of miR-27a. The osteosarcoma tissues and cells exhibited elevated miR-27 expression and reduced SFRP1 expression. SFRP1 was verified to be a target gene of miR-27a. Meanwhile, silenced miR-27a inhibited proliferation and invasion of human osteosarcoma cells. Finally, silencing miR-27a inhibited the activation of Wnt/β-catenin signaling pathway, evidenced by reduced β-catenin expression. Our study draws a conclusion that silencing miR-27a dampens osteosarcoma progression, which might be achieved through the inactivation of the Wnt/β-catenin signaling pathway by up-regulating SFRP1.

Correlation between SFRP1 expression and clinicopathological parameters in patients with triple-negative breast cancer

Aim: Breast cancer is a heterogeneous disease with distinct molecular and clinical behavior demanding reliable biomarkers, especially in triple-negative breast cancer (TNBC). This study seeks to improve the understanding of SFRP1 as a potential biomarker in breast cancer focusing on TNBC. Materials & methods: SFRP1 expression was investigated via immunohistochemistry with two anti-SFRP1-antibodies on tissue-microarrays of 376 invasive breast cancers. Results: Statistical analysis revealed a highly significant association between TNBC (n = 36) and SFRP1 expression (p < 0.001). SFRP1 expression was significantly associated with younger age, higher tumor stage, size and grade. Conclusion: SFRP1 expression is strongly correlated with TNBC on protein level. Associations with age and tumor grade support the role of SFRP1 as a biomarker for chemotherapy response in TNBC.

miR-542-3p prevents ovariectomy-induced osteoporosis in rats via targeting SFRP1

Secreted frizzled-related protein-1 (SFRP1) is a negative regulatory molecule of the WNT signaling pathway and serves as a therapeutic target for bone formation in osteoporosis. In this study, we first established an ovariectomized (OVX) rat model to simulate postmenopausal osteoporosis and found significant changes in miR-542-3p and sFRP1 expression by RNA sequencing and qRT-PCR. In addition, there was a significant negative correlation between miR-542-3p and sFRP1 mRNA levels in postmenopausal women with osteoporosis. We found that miR-542-3p inhibited the expression of sFRP1 mRNA by luciferase reporter assay. When the miR-542-3p binding site in sFRP1 3'UTR was deleted, it did not affect its expression. Western blot results showed that miR-542-3p inhibited the expression of SFRP1 protein. The expression of SFRP1 was significantly increased in osteoblast-induced mesenchymal stem cells (MSC), whereas the expression of miR-542-3p was significantly decreased. And miR-542-3p transfected MSCs showed a significant increase in osteoblast-specific marker expression, indicating that miR-542-3p is necessary for MSC differentiation. Inhibition of miR-542-3p reduced bone formation, confirmed miR-542-3p play a role in bone formation in vivo. In general, these data suggest that miR-542-3p play an important role in bone formation via inhibiting SFRP1 expression and inducing osteoblast differentiation.

HN1 contributes to migration, invasion, and tumorigenesis of breast cancer by enhancing MYC activity

BACKGROUND

Hematological and neurological expressed 1 (HN1) is upregulated in many tumors, but the role of HN1 in breast cancer progression and its regulatory mechanism have not been well understood.

METHODS

To study the role of HN1 in the initiation and progression of breast cancer, we examined HN1 levels in breast cancer cells and tissues and analyzed the relationship between HN1 levels and patient survival. We used mammosphere formation assay, side population analysis, wound healing assay, transwell assay, soft agar formation assay, and xenografted tumor model to determine the effect of HN1 on the expansion of breast cancer stem cells, and the migration, invasion and tumorigenesis of breast cancer. To determine whether HN1 regulates MYC, we used quantitative real-time PCR and Western blot analysis to assess the expression of MYC and their targeted genes to determine the phenotype caused by knockdown of MYC in breast cancer cell with HN1 overexpression.

RESULTS

In this study, we found that HN1 was upregulated in breast cancer tissues. Patients with high levels of HN1 expression had significantly shorter survival than those with low HN1 expression. In breast cancer cell line, ectopic overexpression of HN1 not only promoted the expansion of breast cancer stem cells, but also promoted cell migration, invasion, and tumorigenesis, while knockdown of HN1 reduced these effects. Furthermore, there was a positive correlation between MYC (also known as c-MYC) level and HN1 level, mechanism analysis suggested HN1 promoted the expression of MYC and its targeted genes like CDK4, CCND1, p21, CAV1, and SFRP1. Downregulation of MYC abrogated the effect of HN1 overexpression in breast cancer cell lines.

CONCLUSION

Taken together, these data reveal that HN1 promotes the progression of breast cancer by upregulating MYC expression, and might be a therapeutic target for breast cancer.

Breast cancer stem cells: current advances and clinical implications

There is substantial evidence that many cancers, including breast cancer, are driven by a population of cells that display stem cell properties. These cells, termed cancer stem cells (CSCs) or tumor initiating cells, not only drive tumor initiation and growth but also mediate tumor metastasis and therapeutic resistance. In this chapter, we summarize current advances in CSC research with a major focus on breast CSCs (BCSCs). We review the prevailing methods to isolate and characterize BCSCs and recent evidence documenting their cellular origins and phenotypic plasticity that enables them to transition between mesenchymal and epithelial-like states. We describe in vitro and clinical evidence that these cells mediate metastasis and treatment resistance in breast cancer, the development of novel strategies to isolate circulating tumor cells (CTCs) that contain CSCs and the use of patient-derived xenograft (PDX) models in preclinical breast cancer research. Lastly, we highlight several signaling pathways that regulate BCSC self-renewal and describe clinical implications of targeting these cells for breast cancer treatment. The development of strategies to effectively target BCSCs has the potential to significantly improve the outcomes for patients with breast cancer.

Deregulation of secreted frizzled-related proteins is associated with aberrant β-catenin activation in the carcinogenesis of oral submucous fibrosis

Secreted frizzled-related proteins (SFRPs), the first identified Wnt antagonists, have been well recognized as tumor suppressors in multiple human cancers through suppressing the Wnt/β-catenin pathway. To better elucidate the mechanisms of SFRPs involved in the carcinogenesis of oral submucous fibrosis (OSF), one of the precancerous lesions of oral squamous cell carcinoma (OSCC), we investigated expression and localization of SFRP1, SFRP5, and β-catenin in normal oral epithelium, OSF, and OSCC tissues. We found that SFRP1 and SFRP5 were readily expressed in normal oral mucous tissues but gradually decreased in OSF early, moderately advanced, and advanced tissues and rarely expressed in OSCC tissues. We found the changes of SFRP1 localization and SFRP5 localization from nucleus to cytoplasm in the carcinogenesis of OSF. There is a significant association among reduced SFRP1, SFRP5, and cytoplasmic/nuclear β-catenin expression, which is correlated with higher tumor grade and stage of OSCC. We further found that SFRP1 and SFRP5 were frequently methylated in OSCC cases with betel quid chewing habit but not in normal oral mucous and different stages of OSF tissues, suggesting that methylation of SFRP1 and SFRP5 is tumor specific in the carcinogenesis of OSF. Taken together, our data demonstrated that reduced SFRP1 and SFRP5 by promoter methylation could lead to cytoplasmic/nuclear accumulation of β-catenin and tumor progression. The changes of SFRPs and β-catenin localization, as well as SFRPs' methylation, could be useful predictors or biomarkers of OSF malignant progression and prognosis.

Low SFRP1 Expression Correlates with Poor Prognosis and Promotes Cell Invasion by Activating the Wnt/β-Catenin Signaling Pathway in NPC

Distant metastasis remains the predominant mode of treatment failure in nasopharyngeal carcinoma (NPC). Unfortunately, the molecular events underlying NPC metastasis remain poorly understood. Secreted frizzled-related protein 1 (SFRP1) plays an important role in tumorigenesis and progression. However, little is known about the function and mechanism of SFRP1 in NPC. Immunohistochemistry was used to determine SFRP1 expression levels in patients with NPC. SFRP1 function was evaluated using MTT, colony formation, wound-healing, Transwell assays, and in vivo models. The methylation level of SFRP1 in NPC cells was examined using bisulfate pyrosequencing; the Wnt/β-catenin signaling pathway genes were studied using Western blotting. Compared with patients with high SFRP1 expression, patients with low SFRP1 expression had worse overall survival [HR, 2.32; 95% confidence interval (CI), 1.36-3.94; P = 0.002], disease-free survival (HR, 1.98; 95% CI, 1.23-3.18; P = 0.005), and distant metastasis-free survival (HR, 2.07; 95% CI, 1.19-3.59; P = 0.009). Multivariate Cox regression analysis indicated that SFRP1 was an independent prognostic factor. Furthermore, SFRP1 was significantly downregulated in NPC cell lines. SFRP1 overexpression suppressed NPC cell proliferation, migration, and invasion in vitro and lung colonization in vivo. SFRP1 expression was restored after treatment with a demethylation agent, and the SFRP1 promoter region was hypermethylated in NPC cells. β-Catenin, c-Myc, and cyclin D1 were downregulated after SFRP1 restoration, which suggested that SFRP1 suppressed growth and metastasis by inhibiting the Wnt/β-catenin signaling pathway in NPC. SFRP1 provides further insight into NPC progression and may provide novel therapeutic targets for NPC treatment.

KAT6A, a chromatin modifier from the 8p11-p12 amplicon is a candidate oncogene in luminal breast cancer

The chromosome 8p11-p12 amplicon is present in 12% to 15% of breast cancers, resulting in an increase in copy number and expression of several chromatin modifiers in these tumors, including KAT6A. Previous analyses in SUM-52 breast cancer cells showed amplification and overexpression of KAT6A, and subsequent RNAi screening identified KAT6A as a potential driving oncogene. KAT6A is a histone acetyltransferase previously identified as a fusion partner with CREB binding protein in acute myeloid leukemia. Knockdown of KAT6A in SUM-52 cells, a luminal breast cancer cell line harboring the amplicon, resulted in reduced growth rate compared to non-silencing controls and profound loss of clonogenic capacity both in mono-layer and in soft agar. The normal cell line MCF10A, however, did not exhibit slower growth with knockdown of KAT6A. SUM-52 cells with KAT6A knockdown formed fewer mammospheres in culture compared to controls, suggesting a possible role for KAT6A in self-renewal. Previous data from our laboratory identified FGFR2 as a driving oncogene in SUM-52 cells. The colony forming efficiency of SUM-52 KAT6A knockdown cells in the presence of FGFR inhibition was significantly reduced compared to cells with KAT6A knockdown only. These data suggest that KAT6A may be a novel oncogene in breast cancers bearing the 8p11-p12 amplicon. While there are other putative oncogenes in the amplicon, the identification of KAT6A as a driving oncogene suggests that chromatin-modifying enzymes are a key class of oncogenes in these cancers, and play an important role in the selection of this amplicon in luminal B breast cancers.

The Discovery of Novel Biomarkers Improves Breast Cancer Intrinsic Subtype Prediction and Reconciles the Labels in the METABRIC Data Set

BACKGROUND

The prediction of breast cancer intrinsic subtypes has been introduced as a valuable strategy to determine patient diagnosis and prognosis, and therapy response. The PAM50 method, based on the expression levels of 50 genes, uses a single sample predictor model to assign subtype labels to samples. Intrinsic errors reported within this assay demonstrate the challenge of identifying and understanding the breast cancer groups. In this study, we aim to: a) identify novel biomarkers for subtype individuation by exploring the competence of a newly proposed method named CM1 score, and b) apply an ensemble learning, as opposed to the use of a single classifier, for sample subtype assignment. The overarching objective is to improve class prediction.

METHODS AND FINDINGS

The microarray transcriptome data sets used in this study are: the METABRIC breast cancer data recorded for over 2000 patients, and the public integrated source from ROCK database with 1570 samples. We first computed the CM1 score to identify the probes with highly discriminative patterns of expression across samples of each intrinsic subtype. We further assessed the ability of 42 selected probes on assigning correct subtype labels using 24 different classifiers from the Weka software suite. For comparison, the same method was applied on the list of 50 genes from the PAM50 method.

CONCLUSIONS

The CM1 score portrayed 30 novel biomarkers for predicting breast cancer subtypes, with the confirmation of the role of 12 well-established genes. Intrinsic subtypes assigned using the CM1 list and the ensemble of classifiers are more consistent and homogeneous than the original PAM50 labels. The new subtypes show accurate distributions of current clinical markers ER, PR and HER2, and survival curves in the METABRIC and ROCK data sets. Remarkably, the paradoxical attribution of the original labels reinforces the limitations of employing a single sample classifiers to predict breast cancer intrinsic subtypes.

Overexpression of neogenin inhibits cell proliferation and induces apoptosis in human MDA-MB-231 breast carcinoma cells

Neogenin has been documented as playing an important role in cancer development. Although an elevated expression of neogenin has been detected in human breast cancer, the role of neogenin in breast cancer cells is not clearly understood. In the present study, we investigated neogenin in breast cancer cell proliferation, migration and apoptosis. We found that neogenin overexpression markedly reduced the proliferation and migration of breast cancer cells (P<0.05). Neogenin overexpression resulted in a reduction in the apoptosis rate. Inhibition of neogenin expression by neogenin siRNA dramatically promoted the proliferation and migration of breast cancer cells, whereas it inhibited cell apoptosis. Furthermore, we found that BMP-2-induced phosphorylation of Smad1/5/8 which was inhibited by neogenin overexpression. The present study demonstrates that neogenin may be a tumor suppressor in breast cancer. Neogenin may serve as a potential diagnostic marker and therapeutic target for breast cancer.

Expression, purification, and therapeutic implications of recombinant sFRP1

Secreted frizzled-related proteins (sFRPs) constitute a family of proteins, which impede the Wnt signaling pathway. Upregulation of the Wnt cascade is one of the multiple facets of carcinogenesis. Herein, we report the expression, solubilization, purification, characterization, and anti-cell proliferative activity of a novel recombinant GST-tagged sFRP1 of human origin. sFRP1 was cloned into pGEX-4T2 bacterial expression vector, and the recombinant protein was overexpressed in Escherichia coli BL21 (DE3). It was solubilized from inclusion bodies with N-lauroylsarcosine and Triton X-100, before being purified to homogeneity using glutathione agarose affinity chromatography column. The purified protein was characterized using Western blotting, MALDI TOF-TOF, and circular dichroism spectroscopy analysis. Homology modeling and docking studies revealed that tagging GST with sFRP1 does not change the binding conformation of the cysteine-rich domain and hence, possibly does not alter its function. The novel anti-proliferative activity of GST-sFRP1 was demonstrated in a dose-dependent manner on two cancer cell lines, viz., HeLa (cervical cancer) and MCF-7 (breast cancer). Also, combination therapy of the protein with chemotherapeutic drugs resulted in enhanced anti-cancer activity. This opens up a new avenue in the application of recombinant sFRP1 for cancer therapeutics.

Influence of secreted frizzled receptor protein 1 (SFRP1) on neoadjuvant chemotherapy in triple negative breast cancer does not rely on WNT signaling

BACKGROUND

Triple negative breast cancer (TNBC) is characterized by lack of expression of both estrogen and progesterone receptor as well as lack of overexpression or amplification of HER2. Despite an increased probability of response to chemotherapy, many patients resistant to current chemotherapy regimens suffer from a worse prognosis compared to other breast cancer subtypes. However, molecular determinants of response to chemotherapy specific to TNBC remain largely unknown. Thus, there is a high demand for biomarkers potentially stratifying triple negative breast cancer patients for neoadjuvant chemotherapies or alternative therapies.

METHODS

In order to identify genes correlating with both the triple negative breast cancer subtype as well as response to neoadjuvant chemotherapy we employed publicly available gene expression profiles of patients, which had received neoadjuvant chemotherapy. Analysis of tissue microarrays as well as breast cancer cell lines revealed correlation to the triple negative breast cancer subtype. Subsequently, effects of siRNA-mediated knockdown on response to standard chemotherapeutic agents as well as radiation therapy were analyzed. Additionally, we evaluated the molecular mechanisms by which SFRP1 alters the carcinogenic properties of breast cancer cells.

RESULTS

SFRP1 was identified as being significantly overexpressed in TNBC compared to other breast cancer subtypes. Additionally, SFRP1 expression is significantly correlated with an increased probability of positive response to neoadjuvant chemotherapy. Knockdown of SFRP1 in triple negative breast cancer cells renders the cells more resistant to standard chemotherapy. Moreover, tumorigenic properties of the cells are modified by knockdown, as shown by both migration or invasion capacity as well reduced apoptotic events. Surprisingly, we found that these effects do not rely on Wnt signaling. Furthermore, we show that pro-apoptotic as well as migratory pathways are differentially regulated after SFRP1 knockdown.

CONCLUSION

We could firstly show that SFRP1 strongly correlates with the triple negative breast cancer subtype and secondly, that SFRP1 might be used as a marker stratifying patients to positively respond to neoadjuvant chemotherapy. The mechanisms by which tumor suppressor SFRP1 influences carcinogenic properties of cancer cells do not rely on Wnt signaling, thereby demonstrating the complexity of tumor associated signaling pathways.

Minireview: the molecular and genomic basis for prostate cancer health disparities

Despite more aggressive screening across all demographics and gradual declines in mortality related to prostate cancer (PCa) in the United States, race disparities persist. For African American men (AAM), PCa is more often an aggressive disease showing increased metastases and greater PCa-related mortality compared with European American men. The earliest research points to how distinctions are likely the result of a combination of factors, including ancestry genetics and lifestyle variables. More recent research considers that cancer, although influenced by external forces, is ultimately a disease primarily driven by aberrations observed in the molecular genetics of the tumor. Research studying PCa predominantly from European American men shows that indolent and advanced or metastatic prostate tumors have distinguishing molecular genomic make-ups. Early yet increasing evidence suggests that clinically distinct PCa from AAM also display molecular distinctions. It is reasonable to predict that further study will reveal molecular subtypes and various frequencies for PCa subtypes among diverse patient groups, thereby providing insight as to the genomic lesions and gene signatures that are functionally implicated in carcinogenesis or aggressive PCa in AAM. That knowledge will prove useful in developing strategies to predict who will develop advanced PCa among AAM and will provide the rationale to develop effective individualized treatment strategies to overcome disparities.

Unexpected close surgical margin in resected buccal cancer: very close margin and DAPK promoter hypermethylation predict poor clinical outcomes

OBJECTIVES

In resected buccal cancer patients, an unexpected close surgical margin has been observed to correlate with poor clinical outcomes. However, close surgical margin alone does not independently guide post-operative therapies, revealing a clinical debate. Hence, the present study intended to explore epigenetic-based bio-predictors for further stratifying this debating patient population.

MATERIALS AND METHODS

Between 2000 and 2008, we retrospectively recruited 44 resected buccal cancer patients with a close surgical margin of ≤5 mm. All patients had post-operative radiotherapy. Genomic DNA was extracted from tumor-enrich areas that contained cancer cells of >70%. Methylation-specific PCR was performed to detect promoter methylation of four tumor suppressor genes, including RASSF1A, DAPK, IRF8, and SFRP1. Post-irradiation locoregional control was defined as the primary end point.

RESULTS

There were 40 males and 4 females, with a median age of 53.5 years (range, 32-82 years). Multivariate analysis identified two independent predictors for locoregional recurrence: very close margin of ≤1 mm (HR: 4.96; 95% CI, 1.63-15.09; P=0.018) and promoter hypermethylation of DAPK (HR: 2.83; 95% CI, 1.05-7.63; P=0.042). The highest risk of locoregional recurrence was observed in patients with both of the two factors (HR, 8.05; 95% CI, 2.56-25.82; P=0.002) when compared with patients with none. Shorter disease-free survival, but not overall survival, was also observed.

CONCLUSION

More aggressive managements should be considered in resected buccal cancer patients with both very close margin and DAPK promoter hypermethylation rather than post-operative observation or radiotherapy alone.

Wnt activation by wild type and mutant myocilin in cultured human trabecular meshwork cells

BACKGROUND

Myocilin is a gene linked to the most prevalent form of glaucoma, a major blinding disease. The trabecular meshwork (TM), a specialized eye tissue, is believed to be involved, at least in part, in the development of glaucoma. The Pro³⁷⁰ to Leu (P370L) mutation of myocilin is associated with severe glaucoma phenotypes and Gln³⁶⁸ stop (Q368X) is the most common myocilin mutation reported. Myocilin, upon overexpression, has been shown to induce phenotypes that include a loss of actin stress fibers, an increase in the cAMP level and protein kinase A (PKA) activity, as well as a reduction in the RhoA activity. We examined herein whether Wnt signaling pathway is involved in the myocilin phenotypes and whether P370L and Q368X mutants also display biological effects similar to those of the wild type myocilin.

METHODOLOGY/PRINCIPAL FINDINGS

Wild type myocilin, when transfected into cultured human TM cells, induced a loss of actin stress fibers as judged by phalloidin staining. Such a loss was averted by treatment of secreted Frizzled-related protein 1 (sFRP1), an inhibitor of Wnt signaling. Consistent with the notion that Wnt pathway mediates the myocilin phenotype, Wnt activation was demonstrated by TOP/FOP-Flash reporter assays. Treatment of human TM cells of a Wnt activator, SB216763, as well as transfection of myocilin P370L and Q368X mutants all resulted in actin stress fiber loss, PKA activation and RhoA inactivation. The PKA elevation was obviated by the sFRP1 treatment, indicating that Wnt signaling was upstream that of PKA.

CONCLUSIONS/SIGNIFICANCE

The present study demonstrated that following forced expression of wild type myocilin, Wnt was activated, triggering in turn other myocilin-related alterations. P370L and Q368X mutations induced similar phenotypes, suggesting one possible mechanism how the mutants may lead to TM cell damage and pathology.

DNA methyltransferase inhibitor, zebularine, delays tumor growth and induces apoptosis in a genetically engineered mouse model of breast cancer

Zebularine is a novel potent inhibitor of both cytidine deaminase and DNA methylation. We examined the effect of zebularine on mammary tumor growth in genetically engineered MMTV-PyMT transgenic mice that develop mammary tumors at 60 days of age with 100% penetrance. The MMTV-PyMT transgenic mice were randomized at 46 days of age into control (n = 25) and zebularine (n = 25) treatment groups and monitored for parameters of tumor growth. Zebularine was administered at 5 mg/mL in drinking water. We observed a significant delay in the growth of mammary tumors in zebularine-treated mice with a statistically significant reduction (P = 0.0135) in total tumor burden at 94 days of age when the mice were sacrificed. After 48 days of zebularine treatment, the tumors were predominantly necrotic compared with untreated animals. In addition, a high apoptotic index by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was observed as early as 13 days following treatment. Immunoblot analysis showed depletion of DNMT1 and partial depletion of DNMT3b after zebularine treatment. Microarray analyses of global gene expression identified upregulation of twelve methylation-regulated genes as well as a set of candidate cancer genes that participate in cell growth and apoptosis. In summary, zebularine inhibits the growth of spontaneous mammary tumors and causes early onset of tumor cell necrosis and apoptosis in a genetically engineered mouse model of breast cancer. Defining the parameters of zebularine-mediated tumor inhibition may advance the future development of DNA methyltransferase inhibitors as an effective cancer treatment.

Aberrant promoter CpG methylation and its translational applications in breast cancer

Breast cancer is a complex disease driven by multiple factors including both genetic and epigenetic alterations. Recent studies revealed that abnormal gene expression induced by epigenetic changes, including aberrant promoter methylation and histone modification, plays a critical role in human breast Carcinogenesis. Silencing of tumor suppressor genes (TSGs) by promoter CpG methylation facilitates cells growth and survival advantages and further results in tumor initiation and progression, thus directly contributing to breast tumorigenesis. Usually, aberrant promoter methylation of TSGs, which can be reversed by pharmacological reagents, occurs at the early stage of tumorigenesis and therefore may serve as a potential tumor marker for early diagnosis and therapeutic targeting of breast cancer. In this review, we summarize the epigenetic changes of multiple TSGs involved in breast pathogenesis and their potential clinical applications as tumor markers for early detection and treatment of breast cancer.

Secreted-frizzled related protein 1 is a transcriptional repression target of the t(8;21) fusion protein in acute myeloid leukemia

Secreted-frizzled related proteins (SFRPs) are modulators of the Wnt signaling pathway that is closely involved in normal and malignant hematopoiesis. Epigenetic deregulation of Wnt modulators leading to aberrant signaling has been reported in adult patients with acute myeloid leukemia (AML), but its occurrence in childhood patients with AML and the role of individual modulators are unclear. In this study, we examined SFRP1, SFRP2, SFRP4, and SFRP5 promoter methylation in 83 patients with AML (59 children and 24 adults) and found preferential SFRP1 methylation and mRNA down-regulation in the prognostically favorable subgroup of AML with t(8;21) translocation. Among the 4 genes, SFRP1 methylation independently predicted prolonged event-free and relapse-free survivals in childhood patients with nonacute promyelocytic leukemia with nonadverse cytogenetics. Mechanistically, we further demonstrated that RUNX1-ETO, the t(8;21) fusion product, specifically bound the SFRP1 promoter and repressed its transcription via a consensus RUNX binding site. In t(8;21)-leukemia cells, SFRP1 selectively inhibited canonical Wnt signaling and cellular proliferation that were associated with concomitant down-regulation of Wnt/β-catenin target genes, including CCND1 and MYC. Taken together, we identified SFRP1 as a transcriptional repression target of the t(8;21) fusion protein and demonstrated a novel mechanism of Wnt activation in a specific subtype of AML.

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.

Drug discovery approaches to target Wnt signaling in cancer stem cells

Cancer stem cells (CSCs) represent a unique subset of cells within a tumor that possess self-renewal capacity and pluripotency, and can drive tumor initiation and maintenance. First identified in hematological malignancies, CSCs are now thought to play an important role in a wide variety of solid tumors such as NSCLC, breast and colorectal cancer. The role of CSCs in driving tumor formation illustrates the dysregulation of differentiation in tumorigenesis. The Wnt, Notch and Hedgehog (HH) pathways are developmental pathways that are commonly activated in many types of cancer. While substantial progress has been made in developing therapeutics targeting Notch and HH, the Wnt pathway has remained an elusive therapeutic target. This review will focus on the clinical relevance of the Wnt pathway in CSCs and tumor cell biology, as well as points of therapeutic intervention and recent advances in targeting Wnt/β-catenin signaling.

Transforming properties of 8p11-12 amplified genes in human breast cancer

Amplification of the 8p11-12 region has been found in about 15% of human breast cancers and is associated with poor prognosis. Earlier, we used genomic analysis of copy number and gene expression to perform a detailed analysis of the 8p11-12 amplicon to identify candidate oncogenes in breast cancer. We identified 21 candidate genes and provided evidence that three genes, namely, LSM-1, TC-1, and BAG4, have transforming properties when overexpressed. In the present study, we systematically investigated the transforming properties of 13 newly identified 8p11-12 candidate oncogenes in vitro. WHSC1L1, DDHD2, and ERLIN2 were most potently transforming oncogenes based on the number of altered phenotypes expressed by the cells. WHSC1L1 contains a PWWP-domain that is a methyl-lysine recognition motif involved in histone code modification and epigenetic regulation of gene expression. Knockdown of WHSC1L1 in 8p11-12-amplified breast cancer cells resulted in profound loss of growth and survival of these cells. Further, we identified several WHSC1L1 target genes, one of which is iroquois homeobox 3 gene (IRX3), a member of the Iroquois homeobox transcription factor family.

Reconstitution of secreted frizzled-related protein 1 suppresses tumor growth and lung metastasis in an orthotopic model of hepatocellular carcinoma

BACKGROUND

Secreted Frizzled-related protein 1 (sFRP1) is frequently silenced in many types of cancer, including hepatocellular carcinoma (HCC), leading to aberrant activation of Wnt signaling and thereby facilitating tumor development. In this study, we aimed to investigate whether restoration of sFRP1 affected HCC growth and metastasis.

METHODS

We generated stable cell lines overexpressing sFRP1 in MHCC97-H cells, which naturally do not express detectable sFRP1 messenger RNA (mRNA) and have high metastatic properties. The effects of sFRP1 reexpression on tumor growth and metastasis were assessed in vitro and in vivo. It was also tested whether β-catenin signaling mediated the function of sFRP1 in tumor progression.

RESULTS

Overexpression of sFRP1 substantially diminished the proliferation and invasion potentials of MHCC97-H cells. Furthermore, sFRP1 expression significantly inhibited MHCC97-H xenograft growth and metastasis in vivo, which was accompanied by decreased angiogenesis and increased tumor cell apoptosis. Moreover, sFRP1 overexpression caused less expression of β-catenin and its downstream effector genes cyclin D1 and matrix metalloproteinase (MMP)-2.

CONCLUSION

Together these findings demonstrate that sFRP1 reconstitution suppresses tumor growth, angiogenesis, and metastasis in MHCC97-H xenografts, which may be associated with inactivation of β-catenin signaling, thus providing a possible therapeutic strategy against HCC.

Triple-negative breast cancer: molecular features, pathogenesis, treatment and current lines of research

Breast cancer is a heterogeneous disease with different morphologies, molecular profiles, clinical behaviour and response to therapy. The triple negative is a particular type of breast cancer defined by absence of oestrogen and progesterone receptor expression as well as absence of ERBB2 amplification. It is characterized by its biological aggressiveness, worse prognosis and lack of a therapeutic target in contrast with hormonal receptor positive and ERBB2+ breast cancers. Given these characteristics, triple-negative breast cancer is a challenge in today's clinical practice. A new breast cancer classification emerged recently in the scientific scene based in gene expression profiles. The new subgroups (luminal, ERBB2, normal breast and basal-like) have distinct gene expression patterns and phenotypical characteristics. Triple-negative breast cancer shares phenotypical features with basal-like breast cancer, which is in turn the most aggressive and with worse outcome. Since microarray gene-expression assays are only used in the research setting, clinicians use the triple-negative definition as a surrogate of basal-like breast cancer. The aim of this review, that focuses on triple-negative breast cancer, is to summarize the most relevant knowledge on this particular type of cancer in terms of molecular features, pathogenesis, clinical characteristics, current treatments and the new therapeutic options that include the use of platinum compounds, EGFR antagonists, antiangiogenics and PARP inhibitors. Advances in research are promising and new types of active drugs will become a reality in the near future, making possible a better outcome for this subgroup of breast cancer patients.