Wnt antagonist family genes as biomarkers for diagnosis, staging, and prognosis of renal cell carcinoma using tumor and serum DNA

HIF2α Promotes Cancer Metastasis through TCF7L2-Dependent Fatty Acid Synthesis in ccRCC

Recent studies have highlighted the notable involvement of the crosstalk between hypoxia-inducible factor 2 alpha (HIF2α) and Wnt signaling components in tumorigenesis. However, the cellular function and precise regulatory mechanisms of HIF2α and Wnt signaling interactions in clear cell renal cell carcinoma (ccRCC) remain elusive. To analyze the correlation between HIF2α and Wnt signaling, we utilized the Cancer Genome Atlas - Kidney Renal Clear Cell Carcinoma (TCGA-KIRC) public database, HIF2α RNA sequencing data, and conducted luciferase reporter assays. A Wnt-related gene set was employed to identify key regulators of Wnt signaling controlled by HIF2α in ccRCC. Furthermore, we assessed the biological effects of TCF7L2 on ccRCC metastasis and lipid metabolism in both in vivo and in vitro settings. Our outcomes confirm TCF7L2 as a key gene involved in HIF2α-mediated regulation of the canonical Wnt pathway. Functional studies demonstrate that TCF7L2 promotes metastasis in ccRCC. Mechanistic investigations reveal that HIF2α stabilizes TCF7L2 mRNA in a method based on m6A by transcriptionally regulating METTL3. Up-regulation of TCF7L2 enhances cellular fatty acid oxidation, which promotes histone acetylation. This facilitates the transcription of genes connected to epithelial-mesenchymal transition and ultimately enhances metastasis of ccRCC. These outcomes offer a novel understanding into the involvement of lipid metabolism in the signaling pathway regulation, offering valuable implications for targeted treatment in ccRCC.

Liquid Biopsy: A New Avenue for the Diagnosis of Kidney Disease: Diabetic Kidney Disease, Renal Cancer, and IgA Nephropathy

Kidney diseases are some of the most common healthcare problems. As the population of elderly individuals with concurrent health conditions continues to rise, there will be a heightened occurrence of these diseases. Due to the renal condition being one of the longevity predictors, early diagnosis of kidney dysfunction plays a crucial role. Currently, prevalent diagnostic tools include laboratory tests and kidney tissue biopsies. New technologies, particularly liquid biopsy and new detection biomarkers, hold promise for diagnosing kidney disorders. The aim of this review is to present modern diagnostic methods for kidney diseases. The paper focuses on the advances in diagnosing three common renal disorders: diabetic kidney disease, renal cancer, and immunoglobulin A nephropathy. We highlight the significance of liquid biopsy and epigenetic changes, such as DNA methylation, microRNA, piRNAs, and lncRNAs expression, or single-cell transcriptome sequencing in the assessment of kidney diseases. This review underscores the importance of early diagnosis for the effective management of kidney diseases and investigates liquid biopsy as a promising approach.

Secreted frizzled-related proteins: A promising therapeutic target for cancer therapy through Wnt signaling inhibition

The Wnt signaling system is a critical pathway that regulates embryonic development and adult homeostasis. Secreted frizzled-related proteins (SFRPs) are extracellular inhibitors of Wnt signaling that act by binding directly to Wnt ligands or Frizzled receptors. SFRPs can act as anti-Wnt agents and suppress cancer growth by blocking the action of Wnt ligands. However, SFRPs are often silenced by promoter methylation in cancer cells, resulting in hyperactivation of the Wnt pathway. Epigenetic modifiers can reverse this silencing and restore SFRPs expression. Despite the potential of SFRPs as a therapeutic target, the effects of SFRPs on tumor development remain unclear. Therefore, a review of the expression of various members of the SFRPs family in different cancers and their potential as therapeutic targets is warranted. This review aims to summarize the current knowledge of SFRPs in cancer, focusing on their expression patterns and their potential as novel therapeutic targets.

New insights into fibrotic signaling in renal cell carcinoma

Fibrotic signaling plays a pivotal role in the development and progression of solid cancers including renal cell carcinoma (RCC). Intratumoral fibrosis (ITF) and pseudo-capsule (PC) fibrosis are significantly correlated to the disease progression of renal cell carcinoma. Targeting classic fibrotic signaling processes such as TGF-β signaling and epithelial-to-mesenchymal transition (EMT) shows promising antitumor effects both preclinically and clinically. Therefore, a better understanding of the pathogenic mechanisms of fibrotic signaling in renal cell carcinoma at molecular resolution can facilitate the development of precision therapies against solid cancers. In this review, we systematically summarized the latest updates on fibrotic signaling, from clinical correlation and molecular mechanisms to its therapeutic strategies for renal cell carcinoma. Importantly, we examined the reported fibrotic signaling on the human renal cell carcinoma dataset at the transcriptome level with single-cell resolution to assess its translational potential in the clinic.

Kidney tumors associated with germline mutations of FH and SDHB show a CpG island methylator phenotype (CIMP)

Germline mutations within the Krebs cycle enzyme genes fumarate hydratase (FH) or succinate dehydrogenase (SDHB, SDHC, SDHD) are associated with an increased risk of aggressive and early metastasizing variants of renal cell carcinoma (RCC). These RCCs express significantly increased levels of intracellular fumarate or succinate that inhibit 2-oxoglutarate-dependent dioxygenases, such as the TET enzymes that regulate DNA methylation. This study evaluated the genome-wide methylation profiles of 34 RCCs from patients with RCC susceptibility syndromes and 11 associated normal samples using the Illumina HumanMethylation450 BeadChip. All the HLRCC (FH mutated) and SDHB-RCC (SDHB mutated) tumors demonstrated a distinct CpG island methylator phenotype (CIMP). HLRCC tumors demonstrated an extensive and relatively uniform level of hypermethylation that showed some correlation with tumor size. SDHB-RCC demonstrated a lesser and more varied pattern of hypermethylation that overlapped in part with the HLRCC hypermethylation. Combined methylation and mRNA expression analysis of the HLRCC tumors demonstrated hypermethylation and transcription downregulation of genes associated with the HIF pathway, HIF3A and CITED4, the WNT pathway, SFRP1, and epithelial-to-mesenchymal transition and MYC expression, OVOL1. These observations were confirmed in the TCGA CIMP-RCC tumors. A selected panel of probes could identify the CIMP tumors and differentiate between HLRCC and SDHB-RCC tumors. This panel accurately detected all CIMP-RCC tumors within the TCGA RCC cohort, identifying them as HLRCC -like, and could potentially be used to create a liquid biopsy-based screening tool. The CIMP signature in these aggressive tumors could provide both a useful biomarker for diagnosis and a target for novel therapies.

LiKidMiRs: A ddPCR-Based Panel of 4 Circulating miRNAs for Detection of Renal Cell Carcinoma

Simple Summary

Early detection of renal cell carcinoma (RCC) significantly increases the likelihood of curative treatment, avoiding the need of adjuvant therapies, associated side effects and comorbidities. Thus, we aimed to discover circulating microRNAs that might aid in early, minimally invasive, RCC detection/diagnosis.

Abstract

Background: Decreased renal cell cancer-related mortality is an important societal goal, embodied by efforts to develop effective biomarkers enabling early detection and increasing the likelihood of curative treatment. Herein, we sought to develop a new biomarker for early and minimally invasive detection of renal cell carcinoma (RCC) based on a microRNA panel assessed by ddPCR. Methods: Plasma samples from patients with RCC (n = 124) or oncocytomas (n = 15), and 64 healthy donors, were selected. Hsa-miR-21-5p, hsa-miR-126-3p, hsa-miR-155-5p and hsa-miR-200b-3p levels were evaluated using a ddPCR protocol. Results: RCC patients disclosed significantly higher circulating levels of hsa-miR-155-5p compared to healthy donors, whereas the opposite was observed for hsa-miR-21-5p levels. Furthermore, hsa-miR-21-5p and hsa-miR-155-5p panels detected RCC with high sensitivity (82.66%) and accuracy (71.89%). The hsa-miR-126-3p/hsa-miR-200b-3p panel identified the most common RCC subtype (clear cell, ccRCC) with 74.78% sensitivity. Conclusion: Variable combinations of plasma miR levels assessed by ddPCR enable accurate detection of RCC in general, and of ccRCC. These findings, if confirmed in larger studies, provide evidence for a novel ancillary tool which might aid in early detection of RCC.

The Next Paradigm Shift in the Management of Clear Cell Renal Cancer: Radiogenomics—Definition, Current Advances, and Future Directions

With improved molecular characterization of clear cell renal cancer and advances in texture analysis as well as machine learning, diagnostic radiology is primed to enter personalized medicine with radiogenomics: the identification of relationships between tumor image features and underlying genomic expression. By developing surrogate image biomarkers, clinicians can augment their ability to non-invasively characterize a tumor and predict clinically relevant outcomes (i.e., overall survival; metastasis-free survival; or complete/partial response to treatment). It is thus important for clinicians to have a basic understanding of this nascent field, which can be difficult due to the technical complexity of many of the studies. We conducted a review of the existing literature for radiogenomics in clear cell kidney cancer, including original full-text articles until September 2021. We provide a basic description of radiogenomics in diagnostic radiology; summarize existing literature on relationships between image features and gene expression patterns, either computationally or by radiologists; and propose future directions to facilitate integration of this field into the clinical setting.

CENPA promotes clear cell renal cell carcinoma progression and metastasis via Wnt/β-catenin signaling pathway

Clear cell renal cell carcinoma (ccRCC) is the most common malignant tumor of the kidney. New and reliable biomarkers are in urgent need for ccRCC diagnosis and prognosis. The CENP family is overexpressed in many types of cancers, but its functions in ccRCC have not been fully clarified. In this paper, we found that several CENP family members were highly expressed in ccRCC tissues. Also, CENPA expression level was related to clinicopathological grade and prognosis by weighted gene co-expression network analysis (WGCNA). CENPA served as a representative CENP family member as a ccRCC biomarker. Further in vitro experiments verified that overexpression of CENPA promoted ccRCC proliferation and metastasis by accelerating the cell cycle and activating the Wnt/β-catenin signaling pathway. The elevated β-catenin led by CENPA overexpression translocated to nucleus for downstream effect. Functional recovery experiment confirmed that Wnt/β-catenin pathway was essential for ccRCC progression and metastasis. Developing selective drugs targeting CENPA may be a promising direction for cancer treatment.

Epigenetic Biomarkers of Renal Cell Carcinoma for Liquid Biopsy Tests

Renal cell carcinomas (RCC) account for 2–3% of the global cancer burden and are characterized by the highest mortality rate among all genitourinary cancers. However, excluding conventional imagining approaches, there are no reliable diagnostic and prognostic tools available for clinical use at present. Liquid biopsies, such as urine, serum, and plasma, contain a significant amount of tumor-derived nucleic acids, which may serve as non-invasive biomarkers that are particularly useful for early cancer detection, follow-up, and personalization of treatment. Changes in epigenetic phenomena, such as DNA methylation level, expression of microRNAs (miRNAs), and long noncoding RNAs (lncRNAs), are observed early during cancer development and are easily detectable in biofluids when morphological changes are still undetermined by conventional diagnostic tools. Here, we reviewed recent advances made in the development of liquid biopsy-derived DNA methylation-, miRNAs- and lncRNAs-based biomarkers for RCC, with an emphasis on the performance characteristics. In the last two decades, a mass of circulating epigenetic biomarkers of RCC were suggested, however, most of the studies done thus far analyzed biomarkers selected from the literature, used relatively miniature, local, and heterogeneous cohorts, and suffered from a lack of sufficient validations. In summary, for improved translation into the clinical setting, there is considerable demand for the validation of the existing pool of RCC biomarkers and the discovery of novel ones with better performance and clinical utility.

Cancer Epigenetic Biomarkers in Liquid Biopsy for High Incidence Malignancies

Early alterations in cancer include the deregulation of epigenetic events such as changes in DNA methylation and abnormal levels of non-coding (nc)RNAs. Although these changes can be identified in tumors, alternative sources of samples may offer advantages over tissue biopsies. Because tumors shed DNA, RNA, and proteins, biological fluids containing these molecules can accurately reflect alterations found in cancer cells, not only coming from the primary tumor, but also from metastasis and from the tumor microenvironment (TME). Depending on the type of cancer, biological fluids encompass blood, urine, cerebrospinal fluid, and saliva, among others. Such samples are named with the general term "liquid biopsy" (LB). With the advent of ultrasensitive technologies during the last decade, the identification of actionable genetic alterations (i.e., mutations) in LB is a common practice to decide whether or not targeted therapy should be applied. Likewise, the analysis of global or specific epigenetic alterations may also be important as biomarkers for diagnosis, prognosis, and even for cancer drug response. Several commercial kits that assess the DNA promoter methylation of single genes or gene sets are available, with some of them being tested as biomarkers for diagnosis in clinical trials. From the tumors with highest incidence, we can stress the relevance of DNA methylation changes in the following genes found in LB: SHOX2 (for lung cancer); RASSF1A, RARB2, and GSTP1 (for lung, breast, genitourinary and colon cancers); and SEPT9 (for colon cancer). Moreover, multi-cancer high-throughput methylation-based tests are now commercially available. Increased levels of the microRNA miR21 and several miRNA- and long ncRNA-signatures can also be indicative biomarkers in LB. Therefore, epigenetic biomarkers are attractive and may have a clinical value in cancer. Nonetheless, validation, standardization, and demonstration of an added value over the common clinical practice are issues needed to be addressed in the transfer of this knowledge from "bench to bedside".

SOX17 Antagonizes the WNT Signaling Pathway and is Epigenetically Inactivated in Clear-Cell Renal Cell Carcinoma

Background

SRY-box containing gene 17 (SOX17) was reported to be a candidate tumor suppressor gene in multiple tumors. Little is known about its role in clear-cell renal cell carcinoma (ccRCC). This study aims to identify the epigenetic regulation and tumor-suppressive function of SOX17 in ccRCC.

Patients and Methods

Fifty-five human ccRCC tissue samples, ten adjacent non-malignant kidney tissue samples, 20 paired paraffin section tissues and seven RCC cell lines were obtained. Immunohistochemistry (IHC) and real-time PCR were used to examine the expression of the target genes at the mRNA and protein levels. The methylation of SOX17 was analyzed using methylation-specific PCR (MSP) and bisulfite genomic sequencing (BGS) assay. The functions of SOX17 were examined by using CCK8, colony formation, wound healing assay and Matrigel invasion assays. Luciferase assay was used to analyze the function of SOX17 in the WNT signaling pathway.

Results

We investigated the SOX17 expression in ccRCC tissues and adjacent non-malignant kidney tissues using PCR and IHC. The expression of SOX17 was lower in ccRCC tissues. Next, we analyzed the DNA promoter methylation of SOX17 in 55 human ccRCC tissues, 10 adjacent non-malignant kidney tissues and RCC cell lines using MSP. DNA methylation of the SOX17 promoter region occurred in 60% of ccRCC tissues and 10% of adjacent non-malignant kidney tissues. In vitro experiments showed that SOX17 suppressed the proliferation of RCC cells. Furthermore, SOX17 inhibited the migration of RCC cells as shown in the wound healing and migration assays. In addition, we found that SOX17 overexpression affected the WNT signaling pathway by downregulating c-myc and cyclinD1.

Conclusion

In summary, our study showed that SOX17 is downregulated in ccRCC and the loss of SOX17 expression is regulated via epigenetic mechanisms in ccRCC. In addition, SOX17 negatively regulates the WNT signaling pathway and function as a tumor suppressor in ccRCC.

The Role of Epigenetics in the Progression of Clear Cell Renal Cell Carcinoma and the Basis for Future Epigenetic Treatments

Simple Summary

The accumulated evidence on the role of epigenetic markers of prognosis in clear cell renal cell carcinoma (ccRCC) is reviewed, as well as state of the art on epigenetic treatments for this malignancy. Several epigenetic markers are likely candidates for clinical use, but still have not passed the test of prospective validation. Development of epigenetic therapies, either alone or in combination with tyrosine-kinase inhibitors of immune-checkpoint inhibitors, are still in their infancy.

Abstract

Clear cell renal cell carcinoma (ccRCC) is curable when diagnosed at an early stage, but when disease is non-confined it is the urologic cancer with worst prognosis. Antiangiogenic treatment and immune checkpoint inhibition therapy constitute a very promising combined therapy for advanced and metastatic disease. Many exploratory studies have identified epigenetic markers based on DNA methylation, histone modification, and ncRNA expression that epigenetically regulate gene expression in ccRCC. Additionally, epigenetic modifiers genes have been proposed as promising biomarkers for ccRCC. We review and discuss the current understanding of how epigenetic changes determine the main molecular pathways of ccRCC initiation and progression, and also its clinical implications. Despite the extensive research performed, candidate epigenetic biomarkers are not used in clinical practice for several reasons. However, the accumulated body of evidence of developing epigenetically-based biomarkers will likely allow the identification of ccRCC at a higher risk of progression. That will facilitate the establishment of firmer therapeutic decisions in a changing landscape and also monitor active surveillance in the aging population. What is more, a better knowledge of the activities of chromatin modifiers may serve to develop new therapeutic opportunities. Interesting clinical trials on epigenetic treatments for ccRCC associated with well established antiangiogenic treatments and immune checkpoint inhibitors are revisited.

DNA methylation and protein expression of Wnt pathway markers in progressive glioblastoma

BACKGROUND

Wnt signaling plays important roles in tumorigenesis, invasiveness and therapeutic resistance of glioblastoma (GBM).

METHODS

We simultaneously investigated six Wnt pathway markers (Wnt5a, Fzd-2, beta-catenin, Wnt3a, Wnt7b, Fzd-10) at epigenetic and protein levels in 21 sequential formalin-fixed paraffin-embedded GBM pairs and controls.

RESULTS

Expression levels of Wnt5a, beta-catenin and Wnt3a proteins either moderately or significantly increased, while those of Fzd-2, Wnt7b and Fzd-10 decreased in the primary (GBM-P) and recurrent (GBM-R) tumors compared to the controls. Methylation levels within promoters and genes showed corresponding decreases for Wnt5a, beta-catenin and Wnt3a in tumors vs. controls, while that of Fzd-10 was uniformly high. Comparing the GBM-P and GBM-R pairs, proteins of Fzd-2, beta-catenin and Wnt3a were either moderately or significantly up-, while that of Wnt7b was downregulated in GBM-R, but these patterns were not accompanied by inverse methylation patterns in the corresponding promoters and genes over time. No methylation differences were noted within promoters and genes of the same markers in 112 pairs of primary and recurrent GBMs in a database, suggesting that the observed changes in protein expression levels may not be explained by CpG methylation status alone. The promoter and gene methylation rate was the highest for Fzd-10 in the database cohort too, supporting the noted low Fzd-10 protein expression.

DISCUSSION

These analyses underscore the relevance of Wnt pathway molecules in the context of their methylation profiles in the development and evolution of GBM, and suggest that Wnt pathway regulation as a potential treatment target merits further studies.

Renal Cell Carcinoma: Predicting DNA Methylation Subtyping and Its Consequences on Overall Survival With Computed Tomography Imaging Characteristics

PURPOSE

The aim of the study was to investigate associations between computed tomography (CT) imaging characteristics, DNA methylation subtyping, and overall survival in renal cell carcinomas.

METHODS

Survival curves were calculated using the Kaplan-Meier analysis. The CT data from 212 patients generated with The Cancer Imaging Archive (TCIA) were reviewed. Identified were 70 (33.0%) M1 subtype, 17 (8.0%) M2 subtype, and 125 (59.0%) M3 subtype. Univariate and multivariate analyses were performed using the logistic regression model.

RESULTS

Patients with M1 subtype had the shortest median overall survival (P < 0.001). On univariate analysis, long axis of 70 mm, intratumoral calcifications, enhancement, long axis > median, short axis > median, and intratumoral vascularity were associated with a significantly higher incidence of M1 subtype (P < 0.05). Short axis ≤ median, absence of necrosis, absence of intratumoral vascularity, and nodular enhancement were associated with M2 subtype (P < 0.05). Short axis ≤ median, long axis ≤ median, long axis of less than 70 mm, and necrosis were associated with a significantly higher incidence of M3 subtype (P < 0.05). On multivariate logistic regression analysis, long axis of greater than 70 mm (odds ratio [OR] = 2.452, P = 0.004; 95% confidence interval [CI] = 1.332-4.514) and necrosis (OR = 4.758, P = 0.041, 95% CI = 1.065-21.250) were associated with M1 subtype (area under the curve [AUC] = 0. 664). Necrosis (OR = 0.047, P < 0.001, 95% CI = 0.012-0.178) and enhancement (OR = 0.083, P = 0.024, 95% CI = 0.010-0.716) were associated with M2 subtype (AUC = 0.909). Long axis > median (OR = 0.303, P < 0.001, 95% CI = 0.164-0.561) and necrosis (OR = 3.256, P = 0.003, 95% CI = 1.617-10.303) were associated with M3 subtype (AUC = 0. 664).

CONCLUSIONS

The shortest survival was observed in patients with M1 subtype. This preliminary radiogenomics analysis of renal cell carcinoma demonstrated associations between CT imaging characteristic and DNA methylation subtyping.

Identification of DNA methylation patterns and biomarkers for clear-cell renal cell carcinoma by multi-omics data analysis

Background

Tumorigenesis is highly heterogeneous, and using clinicopathological signatures only is not enough to effectively distinguish clear cell renal cell carcinoma (ccRCC) and improve risk stratification of patients. DNA methylation (DNAm) with the stability and reversibility often occurs in the early stage of tumorigenesis. Disorders of transcription and metabolism are also an important molecular mechanisms of tumorigenesis. Therefore, it is necessary to identify effective biomarkers involved in tumorigenesis through multi-omics analysis, and these biomarkers also provide new potential therapeutic targets.

Method

The discovery stage involved 160 pairs of ccRCC and matched normal tissues for investigation of DNAm and biomarkers as well as 318 cases of ccRCC including clinical signatures. Correlation analysis of epigenetic, transcriptomic and metabolomic data revealed the connection and discordance among multi-omics and the deregulated functional modules. Diagnostic or prognostic biomarkers were obtained by the correlation analysis, the Least Absolute Shrinkage and Selection Operator (LASSO) and the LASSO-Cox methods. Two classifiers were established based on random forest (RF) and LASSO-Cox algorithms in training datasets. Seven independent datasets were used to evaluate robustness and universality. The molecular biological function of biomarkers were investigated using DAVID and GeneMANIA.

Results

Based on multi-omics analysis, the epigenetic measurements uniquely identified DNAm dysregulation of cellular mechanisms resulting in transcriptomic alterations, including cell proliferation, immune response and inflammation. Combination of the gene co-expression network and metabolic network identified 134 CpG sites (CpGs) as potential biomarkers. Based on the LASSO and RF algorithms, five CpGs were obtained to build a diagnostic classifierwith better classification performance (AUC > 99%). A eight-CpG-based prognostic classifier was obtained to improve risk stratification (hazard ratio (HR) > 4; log-rank test, p-value < 0.01). Based on independent datasets and seven additional cancers, the diagnostic and prognostic classifiers also had better robustness and stability. The molecular biological function of genes with abnormal methylation were significantly associated with glycolysis/gluconeogenesis and signal transduction.

Conclusion

The present study provides a comprehensive analysis of ccRCC using multi-omics data. These findings indicated that multi-omics analysis could identify some novel epigenetic factors, which were the most important causes of advanced cancer and poor clinical prognosis. Diagnostic and prognostic biomarkers were identified, which provided a promising avenue to develop effective therapies for ccRCC.

Age-, tumor-, and metastatic tissue-associated DNA hypermethylation of a T-box brain 1 locus in human kidney tissue

BACKGROUND

While a considerable number of tumor-specific hypermethylated loci have been identified in renal cell cancer (RCC), DNA methylation of loci showing successive increases in normal, tumoral, and metastatic tissues could point to genes with high relevance both for the process of tumor development and progression. Here, we report that DNA methylation of a locus in a genomic region corresponding to the 3'UTR of the transcription factor T-box brain 1 (TBR1) mRNA accumulates in normal renal tissues with age and possibly increased body mass index. Moreover, a further tissue-specific increase of methylation was observed for tumor and metastatic tissue samples.

RESULTS

Biometric analyses of the TCGA KIRC methylation data revealed candidate loci for age-dependent and tumor-specific DNA methylation within the last exon and in a genomic region corresponding to the 3'UTR TBR1 mRNA. To evaluate whether methylation of TBR1 shows association with RCC carcinogenesis, we measured 15 tumor cell lines and 907 renal tissue samples including 355 normal tissues, 175 tissue pairs of normal tumor adjacent and corresponding tumor tissue as well 202 metastatic tissues samples of lung, bone, and brain metastases by the use of pyrosequencing. Statistical evaluation demonstrated age-dependent methylation in normal tissue (R = 0.72, p < 2 × 10^-16), association with adiposity (P = 0.019) and tumor-specific hypermethylation (P = 6.1 × 10^-19) for RCC tissues. Comparison of tumor and metastatic tissues revealed higher methylation in renal cancer metastases (P = 2.65 × 10^-6).

CONCLUSIONS

Our analyses provide statistical evidence of association between methylation of TBR1 and RCC development and disease progression.

Association between SFRP promoter hypermethylation and different types of cancer: A systematic review and meta-analysis

Abnormal methylation of secreted frizzled-related proteins (SFRPs) has been observed in various human cancer types. The loss of SFRP gene expression induces the activation of the Wnt pathway and is a vital mechanism for tumorigenesis and development. The aim of the present systematic review was to assess the association between SFRP methylation and cancer risk. A meta-analysis was systematically conducted to assess the clinicopathological significance of SFRP methylation in cancer risk. The Cochrane Library, PubMed and Web of Science databases were comprehensively searched, and 83 publications with a total of 21,612 samples were selected for the meta-analysis. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated to evaluate the degree of associations between SFRP promoter methylation and cancer risk. Subgroup analysis, meta regression and sensitivity analysis were used to identify the potential sources of heterogeneity. SFRP1, SFRP2, SFRP4 and SFRP5 hypermethylation was significantly associated with cancer risk, with ORs of 8.48 (95% CI, 6.26-11.49), 8.21 (95% CI, 6.20-10.88), 11.41 (95% CI, 6.42-20.30) and 6.34 (95% CI, 3.86-10.42), respectively. SFRP2 methylation was significantly associated with differentiation in colorectal cancer (OR, 2.16; 95% CI, 1.02-4.56). The results of the present study demonstrated that SFRP methylation may contribute to carcinogenesis, especially in certain cancer types, including hepatocellular carcinoma and colorectal cancer.

Structure, function and disease relevance of Wnt inhibitory factor 1, a secreted protein controlling the Wnt and hedgehog pathways

Wnts and Hedgehogs (Hh) are large, lipid-modified extracellular morphogens that play key roles in embryonic development and stem cell proliferation of Metazoa. Both morphogens signal through heptahelical Frizzled-type receptors of the G-Protein Coupled Receptor family and there are several other similarities that suggest a common evolutionary origin of the Hh and Wnt pathways. There is evidence that the secreted protein, Wnt inhibitory factor 1 (WIF1) modulates the activity of both Wnts and Hhs and may thus contribute to the intertwining of these pathways. In this article, we review the structure, evolution, molecular interactions and functions of WIF1 with major emphasis on its role in carcinogenesis.

Contribution of the Wnt Pathway to Defining Biology of Glioblastoma

Glioblastoma (GBM), a highly lethal brain tumor, has been comprehensively characterized at the molecular level with the identification of several potential treatment targets. Data concerning the Wnt pathway are relatively sparse, but apparently very important in defining several aspects of tumor biology. The Wnt ligands are involved in numerous basic biological processes including regulation of embryogenic development, cell fate determination, and organogenesis, but growing amount of data also support the roles of Wnt pathways in the formation of many tumors, including gliomas. Two main Wnt pathways are distinguished: the canonical (β-catenin) and non-canonical (planar cell polarity, Wnt/Ca²⁺) routes. Wnt signaling regulates glioma stem cells (GSCs), thereby defining invasive potential, recurrence, and treatment resistance of GBM. Some observations suggest that the Wnt pathways are differentially active in molecular subtypes of this tumor, thereby may also guide prognostication and novel therapeutic decisions. In this review, we highlight main elements and biological relevance of the Wnt pathways, primarily focusing on the pathogenesis and subtypes of GBM. Finally, we briefly summarize newer therapeutic strategies targeting networks of the Wnt signaling cascades and their molecular associates that appear to be marked contributors to GBM aggressiveness.

SFRP1 Promoter Methylation and Renal Carcinoma Risk: A Systematic Review and Meta-Analysis

BACKGROUND/AIM

Epigenetic inactivation of tumor suppressor genes is an important molecular mechanism in the formation and development of human tumors. The purpose of our study was to evaluate the correlation between the methylation level of the secreted frizzled-related protein 1 (SFRP1) gene and the risk of renal cell carcinoma (RCC).

METHODS

The relevant literature was searched in detail in several electronic databases. The methodological heterogeneity was analyzed by meta-regression and subgroup analyses. The odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were calculated to summarize the dichotomous outcomes of our meta-analysis.

RESULTS

The ten included articles contained 535 RCC samples and 475 normal controls. The results demonstrated that the methylation level of the SFRP1 promoter region was significantly correlated with an increased incidence of RCC (OR=13.72; 95% CI: 6.01-31.28; P=0.000). Furthermore, the eligible studies that had sufficient clinical data about the RCC cases were included in the analysis, and the results indicated that the frequency of SFRP1 promoter methylation was associated with a higher histological grade (P=0.000), tumor stage (P=0.033), tumor size (≥5 cm; P=0.029), and distant metastasis (P=0.047).

CONCLUSION

Our results indicate that the methylation level of the SFRP1 promoter region is increased in patients with RCC compared to normal controls and might be involved in the occurrence and development of RCC. Additional well-designed studies are needed to further verify our conclusions.

Targeting DNA Methyltranferases in Urological Tumors

Urological cancers are a heterogeneous group of malignancies accounting for a considerable proportion of cancer-related morbidity and mortality worldwide. Aberrant epigenetic traits, especially altered DNA methylation patterns constitute a hallmark of these tumors. Nonetheless, these alterations are reversible, and several efforts have been carried out to design and test several epigenetic compounds that might reprogram tumor cell phenotype back to a normal state. Indeed, several DNMT inhibitors are currently under evaluation for therapeutic efficacy in clinical trials. This review highlights the critical role of DNA methylation in urological cancers and summarizes the available data on pre-clinical assays and clinical trials with DNMT inhibitors in bladder, kidney, prostate, and testicular germ cell cancers.

The Cancer Genome Atlas Comprehensive Molecular Characterization of Renal Cell Carcinoma

Renal cell carcinoma (RCC) is not a single disease, but several histologically defined cancers with different genetic drivers, clinical courses, and therapeutic responses. The current study evaluated 843 RCC from the three major histologic subtypes, including 488 clear cell RCC, 274 papillary RCC, and 81 chromophobe RCC. Comprehensive genomic and phenotypic analysis of the RCC subtypes reveals distinctive features of each subtype that provide the foundation for the development of subtype-specific therapeutic and management strategies for patients affected with these cancers. Somatic alteration of BAP1, PBRM1, and PTEN and altered metabolic pathways correlated with subtype-specific decreased survival, while CDKN2A alteration, increased DNA hypermethylation, and increases in the immune-related Th2 gene expression signature correlated with decreased survival within all major histologic subtypes. CIMP-RCC demonstrated an increased immune signature, and a uniform and distinct metabolic expression pattern identified a subset of metabolically divergent (MD) ChRCC that associated with extremely poor survival.

Diagnostic role of Wnt pathway gene promoter methylation in non small cell lung cancer

Wnt signal pathway genes are known to be involved with cancer development. Here we tested the hypothesis whether DNA methylation of genes part of the Wnt signaling pathway could help the diagnosis of non-small cell lung cancer (NSCLC). The methylation levels of SFRP1, SFRP2, WIF1 and PRKCB in 111 NSCLC patients were evaluated by quantitative methylation-specific PCR (qMSP). Promoter methylation levels of four candidate genes were significantly higher in tumor tissues compared with the adjacent tissues. SFRP1, SFRP2 and PRKCB genes were all shown to be good predictors of NSCLC risk (SFRP1: AUC = 0.711; SFRP2: AUC = 0.631; PRKCB: AUC = 0.650). The combined analysis showed that the methylation status of the four genes had a sensitivity of 70.3% and a specificity of 73.9% in the prediction of NSCLC risk for study cohort. A higher diagnostic value with an AUC of 0.945 (95% CI: 0.923–0.967, sensitivity: 90.6%, specificity: 93.0%) was found in TCGA cohort. In addition, SFRP1 and SFRP2 hypermethylation events were specific to male patients. Further TCGA data mining analysis suggested that SFRP1_cg15839448, SFRP2_cg05774801, and WIF1_cg21383810 were inversely associated with the host gene expression. Moreover, GEO database analysis showed that 5′-Aza-deoxycytidine was able to upregulate gene expression in several lung cancer cell lines. Subsequent dual-luciferase reporter assay showed a crucial regulatory function of PRKCB promoter. In summary, our study showed that a panel of Wnt signal pathway genes (SFRP1, SFRP2, WIF1 and PRKCB) had the potential as methylation biomarkers in the diagnosis of NSCLC.

Cell-free DNA: the role in pathophysiology and as a biomarker in kidney diseases

Cell-free DNA (cfDNA) is present in various body fluids and originates mostly from blood cells. In specific conditions, circulating cfDNA might be derived from tumours, donor organs after transplantation or from the foetus during pregnancy. The analysis of cfDNA is mainly used for genetic analyses of the source tissue -tumour, foetus or for the early detection of graft rejection. It might serve also as a nonspecific biomarker of tissue damage in critical care medicine. In kidney diseases, cfDNA increases during haemodialysis and indicates cell damage. In patients with renal cell carcinoma, cfDNA in plasma and its integrity is studied for monitoring of tumour growth, the effects of chemotherapy and for prognosis. Urinary cfDNA is highly fragmented, but the technical hurdles can now be overcome and urinary cfDNA is being evaluated as a potential biomarker of renal injury and urinary tract tumours. Beyond its diagnostic application, cfDNA might also be involved in the pathogenesis of diseases affecting the kidneys as shown for systemic lupus, sepsis and some pregnancy-related pathologies. Recent data suggest that increased cfDNA is associated with acute kidney injury. In this review, we discuss the biological characteristics, sources of cfDNA, its potential use as a biomarker as well as its role in the pathogenesis of renal and urinary diseases.

DNA Methylation and Urological Cancer, a Step Towards Personalized Medicine: Current and Future Prospects

Urologic malignancies are some of the commonest tumors often curable when diagnosed at early stage. However, accurate diagnostic markers and faithful predictors of prognosis are needed to avoid over-diagnosis leading to overtreatment. Many promising exploratory studies have identified epigenetic markers in urinary malignancies based on DNA methylation, histone modification and non-coding ribonucleic acid (ncRNA) expression that epigenetically regulate gene expression. We review and discuss the current state of development and the future potential of epigenetic biomarkers for more accurate and less invasive detection of urological cancer, tumor recurrence and progression of disease serving to establish diagnosis and monitor treatment efficacies. The specific clinical implications of such methylation tests on therapeutic decisions and patient outcome and current limitations are also discussed.

Prognostic DNA methylation markers for renal cell carcinoma: a systematic review

AIM

Despite numerous published prognostic methylation markers for renal cell carcinoma (RCC), none of these have yet changed patient management. Our aim is to systematically review and evaluate the literature on prognostic DNA methylation markers for RCC.

MATERIALS & METHODS

We conducted an exhaustive search of PubMed, EMBASE and MEDLINE up to April 2017 and identified 49 publications. Studies were reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, assessed for their reporting quality using the Reporting Recommendations for Tumor Marker Prognostic Studies (REMARK) criteria, and were graded to determine the level of evidence (LOE) for each biomarker.

RESULTS

We identified promoter methylation of BNC1, SCUBE3, GATA5, SFRP1, GREM1, RASSF1A, PCDH8, LAD1 and NEFH as promising prognostic markers. Extensive methodological heterogeneity across the included studies was observed, which hampers comparability and reproducibility of results, providing a possible explanation why these biomarkers do not reach the clinic.

CONCLUSION

Potential prognostic methylation markers for RCC have been identified, but they require further validation in prospective studies to determine their true clinical value.

Aberrant Wnt signaling: a special focus in CNS diseases

Wnt signals regulate cell proliferation, migration and differentiation during development, as well as synaptic transmission and plasticity in the adult brain. Abnormal Wnt signaling is central to a number of brain pathologies. We review here, the significance of this pathway focused in the contribution of the most frequent alterations in receptors, secretable modulators and downstream targets in Alzheimer's disease (AD) and Glioblastoma (GBM). β-catenin and GSK3 levels are pivotal in the neurodegeneration associated to AD contributing to memory deficits, tau phosphorylation, increased β-amyloid production and modulation of Apolipoprotein E in the brain. In consequence, β-catenin and GSK3 are targets for potential treatments in AD. Also, Wnt pathway components and secreted molecules interfering with this signaling contribute to the progression of tumoral cells. Wnt pathway activation is a bad prognosis in brain cancer; however, mutations in WNT or Frizzled (FZD) genes do not account for the cases of GBM. Instead, recent studies indicate that epigenetic modifications contribute to the development of GBMs opening novel strategies to study GBM progression.

The epigenetic landscape of renal cancer

The majority of kidney cancers are associated with mutations in the von Hippel-Lindau gene and a small proportion are associated with infrequent mutations in other well characterized tumour-suppressor genes. In the past 15 years, efforts to uncover other key genes involved in renal cancer have identified many genes that are dysregulated or silenced via epigenetic mechanisms, mainly through methylation of promoter CpG islands or dysregulation of specific microRNAs. In addition, the advent of next-generation sequencing has led to the identification of several novel genes that are mutated in renal cancer, such as PBRM1, BAP1 and SETD2, which are all involved in histone modification and nucleosome and chromatin remodelling. In this Review, we discuss how altered DNA methylation, microRNA dysregulation and mutations in histone-modifying enzymes disrupt cellular pathways in renal cancers.

Wnt inhibition is dysregulated in gliomas and its re-establishment inhibits proliferation and tumor sphere formation

Evidence indicates that the growth of glioblastoma (GBM), the most common and malignant primary brain cancer, is driven by glioma stem cells (GSCs) resistant to current treatment. As Wnt-signaling is pivotal in stem cell maintenance, we wanted to explore its role in GSCs with the objective of finding distinct signaling mechanisms that could serve as potential therapeutic targets. We compared gene expression in GSCs (n=9) and neural stem cells from the adult human brain (ahNSC; n=3) to identify dysregulated genes in the Wnt signaling pathway. This identified a six-gene Wnt signature present in all nine primary GSC cultures, and the combined expression of three of these genes (SFRP1, SFRP4 and FZD7) reduced median survival of glioma patients from 38 to 17 months. Treatment with recombinant SFRP1 protein in primary cell cultures downregulated nuclear β-catenin and decreased in vitro proliferation and sphere formation in a dose-dependent manner. Furthermore, expressional and functional analysis of SFRP1-treated GSCs revealed that SFRP1 halts cell cycling and induces apoptosis. These observations demonstrate that Wnt signaling is dysregulated in GSC, and that inhibition of the Wnt pathway could serve as a therapeutic strategy in the treatment of GBM.

The Role of Wnt Signaling in Squamous Cell Carcinoma

Aberrant Wnt signaling pathway is a common feature of tumors and also plays important roles in tumor progression and metastasis of many cancer types. Various lines of evidence suggest that genetic defects affect Wnt pathway components, as well as epigenetic mechanisms that modulate the suppressors of Wnt pathway in oral squamous cell carcinoma. Recently, the newly discovered microRNAs are important molecular regulators in gene expression through transcription and translation repression. They play fundamental roles in a wide spectrum of biological functions, including cancer. In this review, we aim to accumulate recent research findings on the roles of Wnt/β-catenin signaling and discuss how microRNAs affect Wnt/β-catenin signaling in oral squamous cell carcinoma tumorigenesis. Apparently, investigations into the role of microRNAs with regard to the Wnt pathway in oral squamous cell carcinoma may help in the development of better strategies for tumor treatment.

Diagnostic and prognostic epigenetic biomarkers in cancer

Growing cancer incidence and mortality worldwide demands development of accurate biomarkers to perfect detection, diagnosis, prognostication and monitoring. Urologic (prostate, bladder, kidney), lung, breast and colorectal cancers are the most common and despite major advances in their characterization, this has seldom translated into biomarkers amenable for clinical practice. Epigenetic alterations are innovative cancer biomarkers owing to stability, frequency, reversibility and accessibility in body fluids, entailing great potential of assay development to assist in patient management. Several studies identified putative epigenetic cancer biomarkers, some of which have been commercialized. However, large multicenter validation studies are required to foster translation to the clinics. Herein we review the most promising epigenetic detection, diagnostic, prognostic and predictive biomarkers for the most common cancers.

The epigenetic landscape of clear-cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most common subtype of all kidney tumors. During the last few years, epigenetics has emerged as an important mechanism in ccRCC pathogenesis. Recent reports, involving large-scale methylation and sequencing analyses, have identified genes frequently inactivated by promoter methylation and recurrent mutations in genes encoding chromatin regulatory proteins. Interestingly, three of detected genes (PBRM1, SETD2 and BAP1) are located on chromosome 3p, near the VHL gene, inactivated in over 80% ccRCC cases. This suggests that 3p alterations are an essential part of ccRCC pathogenesis. Moreover, most of the proteins encoded by these genes cooperate in histone H3 modifications. The aim of this review is to summarize the latest discoveries shedding light on deregulation of chromatin machinery in ccRCC. Newly described ccRCC-specific epigenetic alterations could potentially serve as novel diagnostic and prognostic biomarkers and become an object of novel therapeutic strategies.

Extracellular activation of Wnt signaling through epigenetic dysregulation of Wnt inhibitory factor-1 (Wif-1) is associated with pathogenesis of adrenocortical tumor

Wnt/β-catenin signaling is considered to be an essential regulator of adrenocortical oncogenesis. Wnt inhibitory factor-1 (Wif-1), an extracellular regulator of Wnt signaling, is frequently down-regulated by hypermethylation of the promoter CpG. We investigated epigenetic regulation of Wif-1 and its association with adrenocortical (AC) tumor pathogenesis in light of Wnt activation. The AC tumors showed a high prevalence of Wif-1 promoter methylation and low prevalence of Wif-1 mRNA transcription as compared to the normal adrenal (NA) samples. Furthermore, a significant correlation was found between Wif-1 promoter methylation and mRNA transcription in the tumors. Either intracellular β-catenin accumulation or β-catenin mRNA transcription was significantly elevated in the AC tumors, which also showed an inverse correlation with Wif-1 mRNA transcription. Cyclin D1, a target gene of Wnt signaling, was also up-regulated in the AC tumors as compared with the NA samples. In addition, down-regulation of Wif-1 was correlated with increased cyclin D1 at both mRNA and protein levels. However, despite the proposed activation of Wnt signaling in AC tumors, only 2 of 20 with intracellular β-catenin accumulation showed β-catenin mutations. Thus, genetic alterations of β-catenin and epigenetics-related Wif-1 promoter hypermethylation may be important mechanisms underlying AC tumor formation though aberrant canonical Wnt/β-catenin signaling activation.

Circulating SFRP1 promoter methylation status in gastric adenocarcinoma and esophageal square cell carcinoma

The secreted frizzled-related protein 1 (SFRP1) gene plays an important role in carcinogenesis of digestive system cancer. Previous studies proved that circulating DNA promoter methylation may be a suitable biomarker for cancer patients. The aim of the present study was to investigate whether the promoter methylation status of serum SFRP1 is a potential biomarker for gastric adenocarcinoma (GAC) and esophageal square cell carcinoma (ESCC). The blood samples obtained from 42 GAC and 36 ESCC patients were detected for the promoter methylation status of SFRP1 by methylation-specific polymerase chain reaction. The control group included 42 benign gastrointestinal disease volunteers (24 benign gastric disease and 18 benign esophageal disease) and 20 healthy volunteers. Serum SFRP1 methylation was evident in 30.95% (13/42) GAC patients and 38.89% (14/36) ESCC patients, which is clearly higher compared to 8.33% (2/24) in benign gastric disease, 11.11% (2/18) in benign esophageal disease and 5% (1/20) in healthy volunteers (P<0.05). The association between the serum SFRP1 promoter methylation status and the clinical pathological features were further analyzed and methylation of the SFRP1 gene was significantly associated with age >60 years in GAC patients (P=0.027). However, no correlations between the SFRP1 methylation status and other clinicopathological parameters were found. In conclusion, the SFRP1 promoter was detected frequently in the serum of GAC and ESCC patients. The detection of circulating methylated SFRP1 in the serum may be a useful biomarker for upper gastrointestinal cancer patients.

Nucleic acid-based biomarkers in body fluids of patients with urologic malignancies

This review focuses on the promising potential of nucleic acids in body fluids such as blood and urine as diagnostic, prognostic, predictive and monitoring biomarkers in urologic malignancies. The tremendous progress in the basic knowledge of molecular processes in cancer, as shown in the companion review on nucleic acid-based biomarkers in tissue of urologic tumors, provides a strong rationale for using these molecular changes as non-invasive markers in body fluids. The changes observed in body fluids are an integrative result, reflecting both tissue changes and processes occurring in the body fluids. The availability of sensitive methods has only recently made possible detailed studies of DNA- and RNA-based markers in body fluids. In addition to these biological aspects, methodological aspects of the determination of nucleic acids in body fluids, i.e. pre-analytical, analytical and post-analytical issues, are particularly emphasized. The characteristic changes of RNA (differential mRNA and miRNA expression) and DNA (concentrations, integrity index, mutations, microsatellite and methylation alterations) in serum/plasma and urine samples of patients suffering from the essential urologic cancers of the prostate, bladder, kidney and testis are summarized and critically discussed below. To translate the promising results into clinical practice, laboratory scientists and clinicians have to collaborate to resolve the challenges of harmonized and feasible pre-analytical and analytical conditions for the selected markers and to validate these markers in well-designed and sufficiently powered multi-center studies.

Dysregulated expression of dickkopfs for potential detection of hepatocellular carcinoma

The prognosis for hepatocellular carcinoma (HCC) remains dismal due to the lack of diagnostic markers for early detection. This review will discuss the clinical potential of the dickkopf (DKK) family members as diagnostic and/or prognostic markers for HCC. In comparison to serum α-fetoprotein (AFP) level, which remains the gold standard for HCC diagnosis, high serum DKK1 levels have higher diagnostic value for HCC, especially for AFP-negative HCC, and can distinguish HCC from non-malignant chronic liver diseases. Additionally, the combination of serum DKK1 and AFP levels enhances diagnostic accuracy for HCC compared to serum DKK1 or AFP levels alone. Although DKK1 offers potential for its use in HCC diagnosis this review will discuss the challenges facing DKK1 and also shed some light on recent developments on the remaining DKK family members: DKK2, DKK3 and DKK4.

Decreased expression of Dkk1 and Dkk3 in human clear cell renal cell carcinoma

The expression patterns of the Dickkopf (Dkk) family of proteins varies in different cancers. In the present study, the expression levels of Dkk1 and Dkk3 were investigated in clear cell renal cell carcinoma (ccRCC) tissues. Dkk1 and Dkk3 serum levels were also examined in patients with ccRCC, and the association between clinicopathological features and Dkk levels was investigated. Serum Dkk1 and Dkk3 were quantified using ELISA in 64 patients with ccRCC and in 30 healthy individuals (controls). The expression levels of Dkk1 and Dkk3 were analyzed in tumor and adjacent normal tissues obtained from patients with ccRCC (n=20) using quantitative polymerase chain reaction (qPCR), western blot analysis and immunohistochemistry. The mean serum levels of Dkk1 and Dkk3 in the patients with ccRCC were significantly lower than those in the healthy controls. Furthermore, the serum Dkk1 levels were significantly lower at higher tumor‑node‑metastasis stages and tumor grades. qPCR, western blot analysis and immunohistochemistry revealed a significant decrease in the Dkk1 and Dkk3 mRNA and protein levels in the tumor tissues compared with the adjacent normal tissues. Consequently, Dkk1 and Dkk3 may present a novel molecular target for the diagnosis and therapeutic treatment of ccRCC.

Tumor-specific hypermethylation of epigenetic biomarkers, including SFRP1, predicts for poorer survival in patients from the TCGA Kidney Renal Clear Cell Carcinoma (KIRC) project

The recent publication of the TCGA Kidney Renal Clear Cell Carcinoma (KIRC) project has provided an immense wealth and breadth of data providing an invaluable tool for confirmation and expansion upon previous observations in a large data set containing multiple data types including DNA methylation, somatic mutation, and clinical information. In clear cell renal cell carcinoma (CCRCC) many genes have been demonstrated to be epigenetically inactivated by promoter hypermethylated and in a small number of cases to be associated with clinical outcome. This study created two cohorts based on the Illumina BeadChip array used to confirm the frequency of tumor-specific hypermethylation of these published hypermethylated genes, assess the impact of somatic mutation or chromosomal loss and provide the most comprehensive assessment to date of the association of this hypermethylation with patient survival. Hypermethylation of the Fibrillin 2 (FBN2) gene was the most consistent epigenetic biomarker for CCRCC across both cohorts in 40.2% or 52.5% of tumors respectively. Hypermethylation of the secreted frizzled-related protein 1 (SFRP1) gene and the basonuclin 1 (BNC1) gene were both statistically associated with poorer survival in both cohorts (SFRP1 - p = <0.0001 or 0.0010 and BNC1 - p = <0.0001 or 0.0380) and represented better independent markers of survival than tumor stage, grade or dimension in one cohort and tumor stage or dimension in the other cohort. Loss of the SFRP1 protein can potentially activate the WNT pathway and this analysis highlighted hypermethylation of several other WNT pathway regulating genes and demonstrated a poorer survival outcome for patients with somatic mutation of these genes. The success of demethylating drugs in hematological malignances and the current trials in solid tumors suggest that the identification of clinically relevant hypermethylated genes combined with therapeutic advances may improve the effectiveness and usefulness of such drugs in clear cell renal cell carcinoma.

Secreted frizzled related proteins: Implications in cancers

The Wnt (wingless-type) signaling pathway plays an important role in embryonic development, tissue homeostasis, and tumor progression becaluse of its effect on cell proliferation, migration, and differentiation. Secreted frizzled-related proteins (SFRPs) are extracellular inhibitors of Wnt signaling that act by binding directly to Wnt ligands or to Frizzled receptors. In recent years, aberrant expression of SFRPs has been reported to be associated with numerous cancers. As gene expression of SFRP members is often lost through promoter hypermethylation, inhibition of methylation through the use of epigenetic modifying agents could renew the expression of SFRP members and further antagonize deleterious Wnt signaling. Several reports have described epigenetic silencing of these Wnt signaling antagonists in various human cancers, suggesting their possible role as tumor suppressors. SFRP family members thus come across as potential tools in combating Wnt-driven tumorigenesis. However, little is known about SFRP family members and their role in different cancers. This review comprehensively covers all the available information on the role of SFRP molecules in various human cancers.

DNA methyltransferase inhibitor-mediated apoptosis in the Wnt/β-catenin signal pathway in a renal cell carcinoma cell line

The Wnt signaling pathway is activated in most cancer types when Wnt antagonist genes are inactivated. Glycogen synthase kinase 3 ( GSK3β) is an important regulator of the Wnt/β-catenin signaling pathway. The mechanisms underlying GSK3β regulation of neoplastic transformation and tumor development are unclear. Studies have raised the possibility that the Wnt signaling pathway may be implicated in renal cell carcinoma (RCC). Therefore, in the present study, we hypothesize that the expression and methylation status of the secreted frizzled-related protein 2 ( sFRP2) gene, one of the secreted antagonists that bind Wnt protein, and re-expression of this gene with the demethylation agent (5-aza-2′-deoxycytidine; DAC) may induce apoptosis in RCC cells. To test this hypothesis, we investigated the relationship among epigenetic inactivation of sFRP2 and p-GSK3β (Ser9) and other Wnt antagonists ( sFRP1, DKK3, WIF-1) and apoptotic factors ( Bax and Caspase3) as well as the anti-apoptotic factor BCL2. Our results indicate that DAC-mediated inhibition of DNA methylation led to a re-activation of sFRP2 expression and increased expression levels of the Wnt antagonists and apoptotic factors. In contrast, the level of β-catenin (CTNNB1) expression decreased. The p-GSK3β (Ser9) protein level in Caki-2 cells was significantly down-regulated, while the DNA fragmentation rate increased after treatment with 5 μM DAC at 96 h. Our data show that sFRP2 functions as a tumor suppressor gene in RCC and that its restoration may offer a new therapeutic approach for the treatment of RCC. Moreover, our study draws attention to the regulatory features of epigenetic molecules and analyses their underlying molecular mechanisms of action and their potential use in clinical practice.