Histone deacetylase inhibitors and epigenetic modifications as a novel strategy in renal cell carcinoma

Biomarkers of disease recurrence in stage I testicular germ cell tumours

Stage I testicular cancer is a disease restricted to the testicle. After orchiectomy, patients are considered to be without disease; however, the tumour is prone to relapse in ~4-50% of patients. Current predictive markers of relapse, which are tumour size and invasion to rete testis (in seminoma) or lymphovascular invasion (in non-seminoma), have limited clinical utility and are unable to correctly predict relapse in a substantial proportion of patients. Adjuvant therapeutic strategies based on available biomarkers can lead to overtreatment of 50-85% of patients. Discovery and implementation of novel biomarkers into treatment decision making will help to reduce the burden of adjuvant treatments and improve patient selection for adjuvant therapy.

PDCD5 inhibits progression of renal cell carcinoma by promoting T cell immunity: with the involvement of the HDAC3/microRNA-195-5p/SGK1

BACKGROUND

Epigenetics exerts a vital role in the onset and development of renal cell carcinoma (RCC). Mounting evidence has shed light on the significance of human immune system in response to tumor infiltrating T cells. Hereby, we sought to unmask the immunomodulatory role of histone deacetylase 3 (HDAC3) and its potential upstream molecule, programmed cell death 5 (PDCD5) in RCC.

METHODS

RCC and adjacent non-cancerous tissues were clinically resected from 58 patients, in which the expression profile of microRNA-195-5p (miR-195-5p), PDCD5, HDAC3, and serum glucocorticoid-inducible kinase 1 (SGK1) was determined by RT-qPCR and Western blot analysis. Their relations were investigated by a series of luciferase assays in combination with ChIP and co-IP. RCC cells (A498) were intervened using gain- and loss-of-function approaches, followed by cell proliferation evaluation. After co-culture with CD3⁺ T cells, flow cytometry and interferon-γ (IFN-γ) determination were performed. A xenograft tumor mouse model was developed for in vivo validation.

RESULTS

PDCD5 was downregulated in RCC tissues and A498 cells. Upregulation of HDAC3, as well as of SGK1, resulted in suppression of A498 cell proliferation and promotion of T cell activation as evidenced by higher IFN-γ expression. Re-expression of PDCD5 downregulated HDAC3, causing a subsequent upregulation of miR-195-5p, while miR-195-5p could inversely modulate its target gene, SGK1. The regulatory mechanism appeared to be functional in vivo.

CONCLUSION

Our results highlight the possible manipulation by PDCD5 on RCC cell proliferation and T cell activation, which provides new clues to better understand the immune balance in RCC progression.

HDAC Inhibitory and Anti-Cancer Activities of Curcumin and Curcumin Derivative CU17 against Human Lung Cancer A549 Cells

Previous research reported that the curcumin derivative (CU17) inhibited several cancer cell growths in vitro. However, its anticancer potential against human lung cancer cells (A549 cell lines) has not yet been evaluated. The purpose of this research was to examine the HDAC inhibitory and anti-cancer activities of CU17 compared to curcumin (CU) in A549 cells. An in vitro study showed that CU17 had greater HDAC inhibitory activity than CU. CU17 inhibited HDAC activity in a dose dependent manner with the half-maximal inhibitory concentration (IC₅₀) value of 0.30 ± 0.086 µg/mL against HDAC enzymes from HeLa nuclear extract. In addition, CU17 could bind at the active pockets of both human class I HDACs (HDAC1, 2, 3, and 8) and class II HDACs (HDAC4, 6, and 7) demonstrated by molecular docking studies, and caused hyperacetylation of histone H3 (Ac-H3) in A549 cells shown by Western blot analysis. MTT assay indicated that both CU and CU17 suppressed A549 cell growth in a dose- and time-dependent manner. Besides, CU and CU17 induced G2/M phase cell cycle arrest and p53-independent apoptosis in A549 cells. Both CU and CU17 down-regulated the expression of p53, p21, Bcl-2, and pERK1/2, but up-regulated Bax expression in this cell line. Although CU17 inhibited the growth of lung cancer cells less effectively than CU, it showed less toxicity than CU for non-cancer cells. Accordingly, CU17 is a promising agent for lung cancer treatment. Additionally, CU17 synergized the antiproliferative activity of Gem in A549 cells, indicating the possibility of employing CU17 as an adjuvant treatment to enhance the chemotherapeutic effect of Gem in lung cancer.

The clinical significance of epigenetic and RNAPII variabilities occurring in clear cell renal cell carcinoma as a potential prognostic marker

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30 ccRCC patients were used, to follow the epigenetic changes (γH2A.X, H3K4me3 and H3K9me3) and the alterations in the level of RNA polymerase II (RNAPII).

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The variabilities between the tumorous and non-tumorous parts of the tissue were measured by image analysis in which we monitored 30 cells from different positions of either the tumorous or the non-tumorous part of the tissue sections.

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These markers were classified to predict patient outcomes based on their individual cellular background. These results also support that detection of any alteration in the level of H3K4me3, H3K9me3, and γH2AX can account valuable information for presuming the progression of ccRCC and the clinical benefits to select the most efficient personalized therapy.

Patients diagnosed with clear cell renal cell carcinoma (ccRCC) have poor prognosis for recurrence and approximately 30–40% of them will later develop metastases. For this reason, the appropriate diagnosis and the more detailed molecular characterisation of the primary tumour, including its susceptibility to metastasis, are crucial to select the proper adjuvant therapy by which the most prosperous outcome can be achieved. Nowadays, clinicopathological variables are used for classification of the tumours. Apart from these, molecular biomarkers are also necessary to improve risk classification, which would be the most beneficial amongst modern adjuvant therapies. As a potential molecular biomarker, to follow the transcriptional kinetics in ccRCC patients (n=30), we analysed epigenetic changes (γH2A.X, H3K4me³, and H3K9me³) and the alterations in the level of RNA polymerase II (RNAPII) by immunohistochemical staining on dissected tissue sections. The variabilities between the tumorous and non-tumorous parts of the tissue were detected using quantitative image analysis by monitoring 30 cells from different positions of either the tumorous or the non-tumorous part of the tissue sections. Data obtained from the analyses were used to identify potential prognostic features and to associate them with the progression. These markers might have a value to predict patient outcomes based on their individual cellular background. These results also support that detection of any alteration in the level of H3K4me³, H3K9me³, and γH2A.X can account for valuable information for presuming the progression of ccRCC and the clinical benefits to select the most efficient personalised therapy.

Comprehensive analysis of a new prognosis signature based on histone deacetylases in clear cell renal cell carcinoma

Histone deacetylases (HDAC) family is vital for tumorigenesis and tumor progression. However, the exact role of the HDAC family in clear cell renal cell carcinoma (ccRCC) remains unclear. Based on The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), and The Human Protein Atlas (HPA) database, we investigated and validated the expression profile, clinical significance and prognostic value of HDAC family members in ccRCC. Moreover, we further explored the correlation between HDACs and tumor microenvironment, tumor stemness, drug activity and immune subtype. The HDAC8, HDAC10, and HDAC11 manifested potential clinical value for prognosis, and the correlation analyses reveals underlying molecular mechanisms, which deserve further investigation for ccRCC. This Integrated bioinformatics analysis, based on transcriptomics and proteomics, implied that HDAC8, HDAC10, and HDAC11 may serve as potential molecular biomarkers and therapeutic targets for ccRCC, but some underlying molecular mechanisms still need to be elucidated.

Optimized Combination of HDACI and TKI Efficiently Inhibits Metabolic Activity in Renal Cell Carcinoma and Overcomes Sunitinib Resistance

Simple Summary

To ameliorate the situation for kidney cancer patients and to broaden the application of available drugs, we initiated this research to enhance the anti-cancer activity through combination treatment. There is an unmet need for innovative treatment strategies and optimized drug combinations haven proven to be an adequate solution. We identified a four-drug combination of two histone deacetylate and two tyrosine kinase inhibitors that is effective in sunitinib-naïve and -resistant human renal cell carcinoma cells. Through our research, we demonstrated the superior anti-cancer activity of an optimized drug combination in comparison to single drugs, while maintaining a good safety/selectivity profile. We anticipate that the development and use of well-established drug combinations will be enforced offering personalized and more diverse treatment options in clinical conditions.

Abstract

Clear cell renal cell carcinoma (ccRCC) is characterized by high histone deacetylase (HDAC) activity triggering both cell motility and the development of metastasis. Therefore, there is an unmet need to establish innovative strategies to advance the use of HDAC inhibitors (HDACIs). We selected a set of tyrosine kinase inhibitors (TKIs) and HDACIs to test them in combination, using the validated therapeutically guided multidrug optimization (TGMO) technique based on experimental testing and in silico data modeling. We determined a synergistic low-dose three-drug combination decreasing the cell metabolic activity in metastatic ccRCC cells, Caki-1, by over 80%. This drug combination induced apoptosis and showed anti-angiogenic activity, both in original Caki-1 and in sunitinib-resistant Caki-1 cells. Through phosphoproteomic analysis, we revealed additional targets to improve the translation of this combination in 3-D (co-)culture systems. Cell–cell and cell–environment interactions increased, reverting the invasive and metastatic phenotype of Caki-1 cells. Our data suggest that our optimized low-dose drug combination is highly effective in complex in vitro settings and promotes the activity of HDACIs.

Epigenetic Modifiers as Potential Therapeutic Targets in Diabetic Kidney Disease

Diabetic kidney disease is one of the fastest growing causes of death worldwide. Epigenetic regulators control gene expression and are potential therapeutic targets. There is functional interventional evidence for a role of DNA methylation and the histone post-translational modifications-histone methylation, acetylation and crotonylation-in the pathogenesis of kidney disease, including diabetic kidney disease. Readers of epigenetic marks, such as bromodomain and extra terminal (BET) proteins, are also therapeutic targets. Thus, the BD2 selective BET inhibitor apabetalone was the first epigenetic regulator to undergo phase-3 clinical trials in diabetic kidney disease with an endpoint of kidney function. The direct therapeutic modulation of epigenetic features is possible through pharmacological modulators of the specific enzymes involved and through the therapeutic use of the required substrates. Of further interest is the characterization of potential indirect effects of nephroprotective drugs on epigenetic regulation. Thus, SGLT2 inhibitors increase the circulating and tissue levels of β-hydroxybutyrate, a molecule that generates a specific histone modification, β-hydroxybutyrylation, which has been associated with the beneficial health effects of fasting. To what extent this impact on epigenetic regulation may underlie or contribute to the so-far unclear molecular mechanisms of cardio- and nephroprotection offered by SGLT2 inhibitors merits further in-depth studies.

The Contribution of Histone Crotonylation to Tissue Health and Disease: Focus on Kidney Health

Acute kidney injury (AKI) and chronic kidney disease (CKD) are the most severe consequences of kidney injury. They are interconnected syndromes as CKD predisposes to AKI and AKI may accelerate CKD progression. Despite their growing impact on the global burden of disease, there is no satisfactory treatment for AKI and current therapeutic approaches to CKD remain suboptimal. Recent research has focused on the therapeutic target potential of epigenetic regulation of gene expression, including non-coding RNAs and the covalent modifications of histones and DNA. Indeed, several drugs targeting histone modifications are in clinical use or undergoing clinical trials. Acyl-lysine histone modifications (e.g. methylation, acetylation, and crotonylation) have modulated experimental kidney injury. Most recently, increased histone lysine crotonylation (Kcr) was observed during experimental AKI and could be reproduced in cultured tubular cells exposed to inflammatory stress triggered by the cytokine TWEAK. The degree of kidney histone crotonylation was modulated by crotonate availability and crotonate supplementation protected from nephrotoxic AKI. We now review the functional relevance of histone crotonylation in kidney disease and other pathophysiological contexts, as well as the implications for the development of novel therapeutic approaches. These studies provide insights into the overall role of histone crotonylation in health and disease.

Anti-leukemic effects of histone deacetylase (HDAC) inhibition in acute lymphoblastic leukemia (ALL) cells: Shedding light on mitigating effects of NF-κB and autophagy on panobinostat cytotoxicity

Identification of the roles of epigenetic alterations in cancers has suggested that different molecules involved in this process are potentially therapeutic targets. Given the role of histone deacetylases (HDACs) enzymes in leukemogenesis, we designed a study to investigate the anti-leukemic property of panobinostat, a HDAC inhibitor, in acute lymphoblastic leukemia (ALL) cells. Our results showed that panobinostat decreased cell viability of pre-B ALL-derived cells. The favorable anti-leukemic effects of the inhibitor was further confirmed by cell cycle analysis, where we found that panobinostat prolonged the transition of the cells from G1 phase probably through c-Myc-mediated up-regulation of cyclin-dependent kinase inhibitors. Unlike the apoptotic effect of panobinostat on Nalm-6 cells, the expression of anti-apoptotic nuclear factor-kappa B (NF-κB) target genes remained unchanged. Accordingly, we found that the inhibition of NF-κB pathway using bortezomib boosted the effect of panobinostat, indicating that panobinostat-induced apoptosis could be attenuated through the activation of the NF-κB pathway. The results of the present study reflected another aspect of autophagy in leukemic cells, as we showed that although Nalm-6 cells could exploit autophagy to override the anti-survival effect of HDAC inhibition, the presence of an autophagy inhibitor could alter the compensatory circumstance to induce cell death. Beyond panobinostat cytotoxicity as a single agent, synergistic experiments outlined that pharmaceutical targeting of HDACs could amplify the cytotoxicity of vincristine in ALL cells, delineating that panobinostat, either as a single agent or in a combined modality, possesses novel promising potentials for the treatment of ALL.

Targeting epigenetic DNA and histone modifications to treat kidney disease

Epigenetics refers to heritable changes in gene expression patterns not caused by an altered nucleotide sequence, and includes non-coding RNAs and covalent modifications of DNA and histones. This review focuses on functional evidence for the involvement of DNA and histone epigenetic modifications in the pathogenesis of kidney disease and the potential therapeutic implications. There is evidence of activation of epigenetic regulatory mechanisms in acute kidney injury (AKI), chronic kidney disease (CKD) and the AKI-to-CKD transition of diverse aetiologies, including ischaemia-reperfusion injury, nephrotoxicity, ureteral obstruction, diabetes, glomerulonephritis and polycystic kidney disease. A beneficial in vivo effect over preclinical kidney injury has been reported for drugs that decrease DNA methylation by either inhibiting DNA methylation (e.g. 5-azacytidine and decitabine) or activating DNA demethylation (e.g. hydralazine), decrease histone methylation by inhibiting histone methyltransferases, increase histone acetylation by inhibiting histone deacetylases (HDACs, e.g. valproic acid, vorinostat, entinostat), increase histone crotonylation (crotonate) or interfere with histone modification readers [e.g. inhibits of bromodomain and extra-terminal proteins (BET)]. Most preclinical studies addressed CKD or the AKI-to-CKD transition. Crotonate administration protected from nephrotoxic AKI, but evidence is conflicting on DNA methylation inhibitors for preclinical AKI. Several drugs targeting epigenetic regulators are in clinical development or use, most of them for malignancy. The BET inhibitor apabetalone is in Phase 3 trials for atherosclerosis, kidney function being a secondary endpoint, but nephrotoxicity was reported for DNA and HDAC inhibitors. While research into epigenetic modulators may provide novel therapies for kidney disease, caution should be exercised based on the clinical nephrotoxicity of some drugs.

Epigenetic Modification Mechanisms Involved in Inflammation and Fibrosis in Renal Pathology

The growing incidence of obesity, hypertension, and diabetes, coupled with the aging of the population, is increasing the prevalence of renal diseases in our society. Chronic kidney disease (CKD) is characterized by persistent inflammation, fibrosis, and loss of renal function leading to end-stage renal disease. Nowadays, CKD treatment has limited effectiveness underscoring the importance of the development of innovative therapeutic options. Recent studies have identified how epigenetic modifications participate in the susceptibility to CKD and have explained how the environment interacts with the renal cell epigenome to contribute to renal damage. Epigenetic mechanisms regulate critical processes involved in gene regulation and downstream cellular responses. The most relevant epigenetic modifications that play a critical role in renal damage include DNA methylation, histone modifications, and changes in miRNA levels. Importantly, these epigenetic modifications are reversible and, therefore, a source of potential therapeutic targets. Here, we will explain how epigenetic mechanisms may regulate essential processes involved in renal pathology and highlight some possible epigenetic therapeutic strategies for CKD treatment.

Oxidative stress-induced epigenetic changes associated with malignant transformation of human kidney epithelial cells

Renal Cell Carcinoma (RCC) in humans is positively influenced by oxidative stress status in kidneys. We recently reported that adaptive response to low level of chronic oxidative stress induces malignant transformation of immortalized human renal tubular epithelial cells. Epigenetic alterations in human RCC are well documented, but its role in oxidative stress-induced malignant transformation of kidney cells is not known. Therefore, the objective of this study was to evaluate the potential role of epigenetic changes in chronic oxidative stress-induced malignant transformation of HK-2, human renal tubular epithelial cells. The results revealed aberrant expression of epigenetic regulatory genes involved in DNA methylation (DNMT1, DNMT3a and MBD4) and histone modifications (HDAC1, HMT1 and HAT1) in HK-2 cells malignantly transformed by chronic oxidative stress. Additionally, both in vitro soft agar assay and in vivo nude mice study showing decreased tumorigenic potential of malignantly transformed HK-2 cells following treatment with DNA de-methylating agent 5-aza 2’ dC further confirmed the crucial role of DNA hypermethyaltion in oxidative stress-induced malignant transformation. Changes observed in global histone H3 acetylation (H3K9, H3K18, H3K27 and H3K14) and decrease in phospho-H2AX (Ser139) also suggest potential role of histone modifications in increased survival and malignant transformation of HK-2 cells by oxidative stress. In summary, the results of this study suggest that epigenetic reprogramming induced by low levels of oxidative stress act as driver for malignant transformation of kidney epithelial cells. Findings of this study are highly relevant in potential clinical application of epigenetic-based therapeutics for treatments of kidney cancers.

Current Concepts of Epigenetics in Testicular Cancer

Testicular germ cell tumors (GCTs) are characterized into seminomas (SGCTs) and non-seminomatous testicular germ cell tumors (NSGCTs). Serum tumor markers (STMs) play an important role in testicular cancer as they provide useful information for diagnosis, staging, and detection of recurrence. Nonetheless, additional tumor markers for early diagnosis and therapeutic options are required to enhance specificity of serological diagnosis of testes cancers. Epigenetics is defined as inherited changes in gene expression that are not encoded in the DNA structure. Epigenetic changes include DNA methylation, histone modifications, and microRNA (miRNA) regulation. It is through the study of epigenetics that diagnostic methods for early detection and novel therapeutic strategies may be established for testicular cancer. We performed a comprehensive review of the English medical literature in PubMed by combining search terms including DNA methylation, histone modifications, microRNA (miRNA) regulation, epigenetics, and testicular cancer. DNA methylation is the most extensively studied epigenetic modification. It consists of the addition of a methyl group to nucleotide bases. It has been reported that SGCT contain reduced levels of DNA methylation compared to NSGCT. MiRNAs are small non-coding RNAs that regulate posttranscriptional gene expression. It has been suggested that miRNAs may play a role in the pathogenesis of GCT. Specific expression patterns have been displayed by various miRNAs in patients with GCT. Histones are proteins intertwined with coiled, double-stranded genomic DNA that form a structure known as a nucleosome. The most widely studied histone modifications include acetylation, methylation, and phosphorylation. Methylation of histone proteins has been found in all types of NSGCT. Epigenetics may offer an additional and effective tool in establishing a diagnosis of GCT of the testes, including prognostic information and perhaps enabling targeted treatment in patients with testicular GCT.

Protocadherin17 Promoter Methylation is a Potential Predictive Biomarker in Clear Cell Renal Cell Carcinoma

Background

Protocadherin17 (PCDH17) is a tumor suppressor gene, and is frequently silenced by promoter methylation in human cancers, including clear cell renal cell carcinoma (ccRCC). However, the clinical significance of PCDH17 methylation in ccRCC remains largely unclear. The aim of the present study was to investigate the methylation status of PCDH17 in ccRCC and its potential relevance to clinicopathological parameters and prognosis.

Material/Methods

Methylation-specific PCR was used to examine the methylation status of PCDH17 in 191 ccRCC tumors and matched paired adjacent noncancerous tissues. Subsequently, the associations between PCDH17 methylation and clinicopathological parameters and prognosis of patients with ccRCC were analyzed.

Results

PCDH17 methylation occurred in 66.5% of ccRCC tumors, but in only 12.1% of adjacent noncancerous tissues. PCDH17 methylation is significantly correlated with advanced stage, higher grade, and lymph node metastasis in ccRCC. Moreover, it is an independent prognostic factor for progression-free survival and overall survival of patients with ccRCC.

Conclusions

PCDH17 methylation occurred more frequently and was associated with malignant clinicopathological characteristics and poor prognosis in ccRCC patients. Thus, PCDH17 methylation may be used as a novel biomarker to predict the prognosis of patients with ccRCC.

Development and validation of a sensitive HPLC-MS/MS method for determination of chidamide (epidaza), a new benzamide class of selective histone deacetylase inhibitor, in human plasma and its clinical application

Chidamide (epidaza), a new oral isotype-selective histone deacetylase inhibitor (HDACi), which is just approved in China for the treatment of recurrent or refractory peripheral T-cell lymphoma (PTCL) in December 2014, is the first listed benzamide class of HDACi in the world, and is currently undergoing global clinical trials for solid tumor treatments. Here, we report a sensitive, rapid and robust HPLC-MS/MS method for determination of chidamide in human plasma. Plasma sample was subjected to a simple acetonitrile protein precipitation containing MS-275 used as an internal standard (IS). Chromatography was performed on a Hypersil GOLD C18 analytical column, using a gradient methanol/water mobile phase containing 0.1% formic acid. A tandem mass spectrometer equipped with electrospray ionization source was used as detector and operated in the positive-ion mode. Selected reaction monitoring (SRM) using the precursor/ product transitions (m/z) of 391.1/265.1 for chidamide and 377.1/359.2 for IS were used for quantification, respectively. Good linearity was obtained in the range of 1-1000ng/mL. The method gave R.S.D.% values for precision always lower than 13.8% and R.E.% values for accuracy between -3.7 and 9.1%. In addition, the specificity, recovery, stability and matrix effect were satisfactory too. The method is now being successfully applied to plasma samples as part of an ongoing chidamide phase Ib clinical trial in patients with solid tumors, and had demonstrated consistent AUClast and t1/2 results with the published phase I pharmacokinetic data, which was also analyzed by this method, thus further confirming the reproducibility and accuracy during its clinical application. Considering the excellent performance of this method, it will continue being utilized for future clinical developments of chidamide and for routine monitoring of plasma exposure of chidamide during its clinical therapy.

Treatment of chronic kidney diseases with histone deacetylase inhibitors

Histone deacetylases (HDACs) induce deacetylation of both histone and non-histone proteins and play a critical role in the modulation of physiological and pathological gene expression. Pharmacological inhibition of HDAC has been reported to attenuate progression of renal fibrogenesis in obstructed kidney and reduce cyst formation in polycystic kidney disease. HDAC inhibitors (HDACis) are also able to ameliorate renal lesions in diabetes nephropathy, lupus nephritis, aristolochic acid nephropathy, and transplant nephropathy. The beneficial effects of HDACis are associated with their anti-fibrosis, anti-inflammation, and immunosuppressant effects. In this review, we summarize recent advances on the treatment of various chronic kidney diseases with HDACis in pre-clinical models.

The role of epigenetics in kidney malignancies

Introduction

Renal cell carcinomas (RCC) are collectively the third most common type of genitourinary neoplasms, surpassed only by prostate and bladder cancer. Cure rates for renal cell carcinoma are related to tumor grade and stage; therefore, diagnostic methods for early detection and new therapeutic modalities are of paramount importance. Epigenetics can be defined as inherited modifications in gene expression that are not encoded in the DNA sequence itself. Epigenetics may play an important role in the pursuit of early diagnosis, accurate prognostication and identification of new therapeutic targets.

Material and methods

We used PubMed to conduct a comprehensive search of the English medical literature using search terms including epigenetics, DNA methylation, histone modification, microRNA regulation (miRNA) and RCC. In this review, we discuss the potential application of epigenetics in the diagnosis, prognosis and treatment of kidney cancer.

Results

During the last decade, many different types of epigenetic alterations of DNA have been found to be associated with malignant renal tumors. This has led to the research of the diagnostic and prognostic implications of these changes in renal malignancies as well as to the development of novel drugs to target these changes, with the aim of achieving a survival benefit.

Conclusions

Epigenetics has become a promising field in cancer research. The potential to achieve early detection and accurate prognostication in kidney cancer might be feasible through the application of epigenetics. The possibility to reverse these epigenetic changes with new therapeutic agents motivates researchers to continue pursuing better treatment options for kidney cancer and other malignancies.

The novel histone deacetylase inhibitor, N-hydroxy-7-(2-naphthylthio) hepatonomide, exhibits potent antitumor activity due to cytochrome-c-release-mediated apoptosis in renal cell carcinoma cells

Background

Epigenetic modifications play a critical role in the regulation of all DNA-based processes, such as transcription, repair, and replication. Inappropriate histone modifications can result in dysregulation of cell growth, leading to neoplastic transformation and cell death. Renal tumors have been shown to have a higher global methylation percentage and reduced histone acetylation. Preclinical models have revealed that histone gene modifiers and epigenetic alterations play important roles in renal cell carcinoma (RCC) tumorigenesis. Recently, a novel HDAC inhibitor, N-hydroxy-7-(2-naphthylthio) heptanomide (HNHA), has been introduced as an example of a new class of anti-cancer agents. The anti-cancer activity of HNHA and the underlying mechanisms of action remain to be clarified.

Methods

The MTS assay using a panel of RCC cells was used to evaluate the anti-proliferative effects of HNHA. The established HDAC inhibitors, SAHA and TSA, were used for comparison. Western blotting analysis was performed to investigate the acetylation of histone H3 and the expression of apoptotic markers in vitro and in vivo. Subcellular fractionation was performed to evaluate expression of Bax and cytochrome c in the cytosol and mitochondria, and also translocation of cytochrome c from the cytoplasm to the nucleus. A confocal microscopic evaluation was performed to confirm inhibition of cell proliferation, induction of apoptosis, and the nuclear translocation of cytochrome c in RCC cells.

Results

In this study, we investigated the apoptosis-inducing activity of HNHA in cultured kidney cancer cells. Apoptosis in the HNHA-treated group was induced significantly, with marked caspase activation and Bcl-2 suppression in RCC cells in vitro and in vivo. HNHA treatment caused cytochrome c release from mitochondria, which was mediated by increased Bax expression and caspase activation. HNHA also induced nuclear translocation of cytochrome c, suggesting that HNHA can induce caspase-independent nuclear apoptosis in RCC cells. An in vivo study showed that HNHA had greater anti-tumor and pro-apoptotic effects on RCC xenografts than the established HDAC inhibitors.

Conclusions

HNHA has more potent anti-tumor activity than established HDAC inhibitors. Its activities are mediated by caspase-dependent and cytochrome-c-mediated apoptosis in RCC cells. These results suggest that HNHA may offer a new therapeutic approach to RCC.

Aberrant methylation of PCDH8 is a potential prognostic biomarker for patients with clear cell renal cell carcinoma

BACKGROUND

PCDH8 is a tumor suppressor that regulates cell adhesin, proliferation, and migration. It is often inactivated by aberrant promoter methylation in several human cancers, including clear cell renal cell carcinoma (CCRCC). The clinical significance of PCDH8 methylation in CCRCC remains unclear. The aim of this study was to investigate the relationship between PCDH8 methylation and clinicopathological characteristics as well as outcome of patients with CCRCC.

MATERIAL/METHODS

The methylation status of PCDH8 in 153 CCRCC tissues and 97 paired adjacent normal renal tissues were examined using methylation-specific PCR (MSP). Then the relationships between PCDH8 methylation and clinicopathological features as well as progression-free survival of CCRCC patients were evaluated.

RESULTS

PCDH8 methylation was significantly more frequent in CCRCC tissues compared with normal renal tissues. Moreover, PCDH8 methylation was significantly correlated with advanced clinical stage (P=0.0141), higher grade (P=0.0190), and lymph node metastasis (P=0.0098). In addition, multivariate analysis showed that PCDH8 methylation was independently associated with poor progression-free survival (P=0.0316).

CONCLUSIONS

PCDH8 methylation is a frequent event in CCRCC and is correlated with unfavorable clinicopathological features. Moreover, PCDH8 methylation may be a useful biomarker to predict the progression of CCRCC.