HDAC6 serves as a biomarker for the prognosis of patients with renal cell carcinoma

Selective HDAC6 Inhibition Has the Potential for Anti-Cancer Effect in Renal Cell Carcinoma

Despite significant advancements in systemic therapy for renal cell carcinoma (RCC), the prognosis for patients with metastatic RCC remains poor, as they are often incurable. Consequently, there is an urgent need for innovative therapeutic strategies to further enhance the efficacy of RCC treatment and improve patient outcomes. One such promising avenue lies in targeting histone deacetylase (HDAC) 6, a protein known to regulate numerous crucial biological processes implicated in cancer progression by modulating the acetylation status of various cytoplasmic proteins. To explore the therapeutic potential of HDAC6 inhibition in RCC, our study focused on investigating the effects of HDAC6 inhibitors on cultured RCC cells. Utilizing a panel of 12 small molecule selective HDAC6 inhibitors and employing genetic knockdown techniques, we examined the impact of HDAC6 inhibition on RCC cellular dynamics. Our findings revealed that HDAC6 inhibition exerted a profound effect on RCC cells, resulting in decreased cell viability and DNA replication. Importantly, this effect was attributed to the induction of apoptosis. Our study provides valuable insights into the mechanisms underlying the anticancer effects of selective HDAC6 inhibitors on RCC. A detailed understanding of the molecular mechanisms underlying the anticancer effects of HDAC6 inhibition is important to explore new therapeutic strategies for metastatic RCC.

Histone deacetylase 6: at the interface of cancer and neurodegeneration

With the recognition in the early 1960s that histones can be post-translationally modified, the list of different post-translational modifications of histones and their biological consequences has continued to expand. In addition, the idea of the 'histone code' hypothesis, later introduced by David Allis and colleagues, further broaden the horizon of chromatin biology. Currently, there is a wealth of knowledge about the transition between the active and the repressive state of chromatin, and modifications of histones remains at the center of chromatin biology. Histone deacetylases (HDACs) in particular are of great importance for the therapeutic success of cancer treatment. Focusing primarily on HDAC6, herein we have briefly highlighted its unique involvement in cancer and also apparently in neurodegeneration.

HDAC6 inhibition: a significant potential regulator and therapeutic option to translate into clinical practice in renal transplantation

Histone deacetylase 6 (HDAC6), an almost exclusively cytoplasmic enzyme, plays an essential role in many biological processes and exerts its deacetylation-dependent/independent effects on a variety of target molecules, which has contributed to the flourishing growth of relatively isoform-specific enzyme inhibitors. Renal transplantation (RT) is one of the alternatively preferred treatments and the most cost-effective treatment approaches for the great majority of patients with end-stage renal disease (ESRD). HDAC6 expression and activity have recently been shown to be increased in kidney disease in a number of studies. To date, a substantial amount of validated studies has identified HDAC6 as a pivotal modulator of innate and adaptive immunity, and HDAC6 inhibitors (HDAC6i) are being developed and investigated for use in arrays of immune-related diseases, making HDAC6i a promising therapeutic candidate for the management of a variety of renal diseases. Based on accumulating evidence, HDAC6i markedly open up new avenues for therapeutic intervention to protect against oxidative stress-induced damage, tip the balance in favor of the generation of tolerance-related immune cells, and attenuate fibrosis by inhibiting multiple activations of cell profibrotic signaling pathways. Taken together, we have a point of view that targeting HDAC6 may be a novel approach for the therapeutic strategy of RT-related complications, including consequences of ischemia-reperfusion injury, induction of immune tolerance in transplantation, equilibrium of rejection, and improvement of chronic renal graft interstitial fibrosis after transplantation in patients. Herein, we will elaborate on the unique function of HDAC6, which focuses on therapeutical mechanism of action related to immunological events with a general account of the tantalizing potential to the clinic.

Curriculum vitae of HDAC6 in solid tumors

Histone deacetylase 6 (HDAC6) is the only member of the HDAC family that resides primarily in the cytoplasm with two catalytic domains and a ubiquitin-binding domain. HDAC6 is highly expressed in various solid tumors and participates in a wide range of biological activities, including hormone receptors, the p53 signaling pathway, and the kinase cascade signaling pathway due to its unique structural foundation and abundant substrate types. Additionally, HDAC6 can function as an oncogenic factor in solid tumors, boosting tumor cell proliferation, invasion and metastasis, drug resistance, stemness, and lowering tumor cell immunogenicity, so assisting in carcinogenesis. Pan-HDAC inhibitors for cancer prevention are associated with potential cardiotoxicity in clinical investigations. It's interesting that HDAC6 silencing didn't cause any significant harm to normal cells. Currently, the use of HDAC6 specific inhibitors, individually or in combination, is among the most promising therapies in solid tumors. This review's objective is to give a general overview of the structure, biological functions, and mechanism of HDAC6 in solid tumor cells and in the immunological milieu and discuss the preclinical and clinical trials of selective HDAC6 inhibitors. These endeavors highlight that targeting HDAC6 could effectively kill tumor cells and enhance patients' immunity during solid tumor therapy.

Inhibition of histone deacetylase 6 destabilizes ERK phosphorylation and suppresses cancer proliferation via modulation of the tubulin acetylation-GRP78 interaction

BACKGROUND

The leading cause of cancer-related mortality worldwide is lung cancer, and its clinical outcome and prognosis are still unsatisfactory. The understanding of potential molecular targets is necessary for clinical implications in precision diagnostic and/or therapeutic purposes. Histone deacetylase 6 (HDAC6), a major deacetylase enzyme, is a promising target for cancer therapy; however, the molecular mechanism regulating cancer pathogenesis is largely unknown.

METHODS

The clinical relevance of HDAC6 expression levels and their correlation with the overall survival rate were analyzed based on the TCGA and GEO databases. HDAC6 expression in clinical samples obtained from lung cancer tissues and patient-derived primary lung cancer cells was evaluated using qRT-PCR and Western blot analysis. The potential regulatory mechanism of HDAC6 was identified by proteomic analysis and validated by immunoblotting, immunofluorescence, microtubule sedimentation, and immunoprecipitation-mass spectrometry (IP-MS) assays using a specific inhibitor of HDAC6, trichostatin A (TSA) and RNA interference to HDAC6 (siHDAC6). Lung cancer cell growth was assessed by an in vitro 2-dimensional (2D) cell proliferation assay and 3D tumor spheroid formation using patient-derived lung cancer cells.

RESULTS

HDAC6 was upregulated in lung cancer specimens and significantly correlated with poor prognosis. Inhibition of HDAC6 by TSA and siHDAC6 caused downregulation of phosphorylated extracellular signal-regulated kinase (p-ERK), which was dependent on the tubulin acetylation status. Tubulin acetylation induced by TSA and siHDAC6 mediated the dissociation of p-ERK on microtubules, causing p-ERK destabilization. The proteomic analysis demonstrated that the molecular chaperone glucose-regulated protein 78 (GRP78) was an important scaffolder required for p-ERK localization on microtubules, and this phenomenon was significantly inhibited by either TSA, siHDAC6, or siGRP78. In addition, suppression of HDAC6 strongly attenuated an in vitro 2D lung cancer cell growth and an in vitro 3D patient derived-lung cancer spheroid growth.

CONCLUSIONS

HDAC6 inhibition led to upregulate tubulin acetylation, causing GRP78-p-ERK dissociation from microtubules. As a result, p-ERK levels were decreased, and lung cancer cell growth was subsequently suppressed. This study reveals the intriguing role and molecular mechanism of HDAC6 as a tumor promoter, and its inhibition represents a promising approach for anticancer therapy.

Emerging role of microtubule-associated proteins on cancer metastasis

The major cause of death in cancer patients is strongly associated with metastasis. While much remains to be understood, microtubule-associated proteins (MAPs) have shed light on metastatic progression’s molecular mechanisms. In this review article, we focus on the role of MAPs in cancer aggressiveness, particularly cancer metastasis activity. Increasing evidence has shown that a growing number of MAP member proteins might be fundamental regulators involved in altering microtubule dynamics, contributing to cancer migration, invasion, and epithelial-to-mesenchymal transition. MAP types have been established according to their microtubule-binding site and function in microtubule-dependent activities. We highlight that altered MAP expression was commonly found in many cancer types and related to cancer progression based on available evidence. Furthermore, we discuss and integrate the relevance of MAPs and related molecular signaling pathways in cancer metastasis. Our review provides a comprehensive understanding of MAP function on microtubules. It elucidates how MAPs regulate cancer progression, preferentially in metastasis, providing substantial scientific information on MAPs as potential therapeutic targets and prognostic markers for cancer management.

Aggresome-Autophagy Associated Gene HDAC6 Is a Potential Biomarker in Pan-Cancer, Especially in Colon Adenocarcinoma

BACKGROUND

Histone deacetylase 6 (HDAC6) regulates cytoplasmic signaling networks through the deacetylation of various cytoplasmic substrates. Recent studies have identified the role of HDAC6 in tumor development and immune metabolism, but its specific function remains unclear.

METHODS

The current study determined the role of HDAC6 in tumor metabolism and tumor immunity through a multi-database pan-cancer analysis. The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), and Cancer Cell Line Encyclopedia (CCLE) datasets were used to determine the expression levels, prognosis, tumor progression, immune checkpoints, and immune metabolism of HDAC6 in 33 tumors. Pathways, immune checkpoints, immune neoantigens, immune microenvironment, tumor mutational burden (TMB), microsatellite instability (MSI), DNA mismatch repair (MMR), and the value of methyltransferases. The R package was used for quantitative analysis and panoramic description.

RESULTS

In the present study, we determined that HDAC6 is differentially expressed in pan carcinomas, and by survival, we found that HDAC6 was generally associated with the prognosis of pancreatic adenocarcinoma, Thymoma, and uveal melanoma, where low expression of HDAC6 had a significantly worse prognosis. Secondly, through this experiment, we confirmed that HDAC6 expression level was associated with tumor immune infiltration and tumor microenvironment, especially in PAAD. Finally, HDAC6 was associated with immune neoantigen and immune checkpoint gene expression profiles in all cancers in addition to TMB and MSI in pan-cancers.

CONCLUSION

HDAC6 is differentially expressed in pan-cancers and plays an essential role in tumor metabolism and immunity. HDAC6 holds promise as a tumor potential prognostic marker, especially in colon cancer.

Silencing of Histone Deacetylase 6 Decreases Cellular Malignancy and Contributes to Primary Cilium Restoration, Epithelial-to-Mesenchymal Transition Reversion, and Autophagy Inhibition in Glioblastoma Cell Lines

Simple Summary

Glioblastoma multiforme (GBM) is the most common as well as the most aggressive malignant brain tumor, with an overall survival of almost 15 months. Histone deacetylase 6 (HDAC6), an enzyme related to the deacetylation of α-tubulin, is overexpressed in GBM. The aim of our research was to study the effects of HDAC6 silencing in GBM cells. We first confirmed the overexpression of HDAC6 in GBM tissue (n = 40) against control brain (n = 10). Treatment with siHDAC6 diminished viability, clonogenic potential, and migration ability in GBM-derived cell lines. HDAC6 inhibition also reverted the mesenchymal phenotype, inhibited the Sonic Hedgehog pathway, restored primary cilium structure, and decreased autophagy. Thus, we confirm that HDAC6 is a good therapeutic target for GBM treatment.

Abstract

Glioblastoma multiforme, the most common type of malignant brain tumor as well as the most aggressive one, lacks an effective therapy. Glioblastoma presents overexpression of mesenchymal markers Snail, Slug, and N-Cadherin and of the autophagic marker p62. Glioblastoma cell lines also present increased autophagy, overexpression of mesenchymal markers, Shh pathway activation, and lack of primary cilia. In this study, we aimed to evaluate the role of HDAC6 in the pathogenesis of glioblastoma, as HDAC6 is the most overexpressed of all HDACs isoforms in this tumor. We treated glioblastoma cell lines with siHDAC6. HDAC6 silencing inhibited proliferation, migration, and clonogenicity of glioblastoma cell lines. They also reversed the mesenchymal phenotype, decreased autophagy, inhibited Shh pathway, and recovered the expression of primary cilia in glioblastoma cell lines. These results demonstrate that HDAC6 might be a good target for glioblastoma treatment.

Correlation analysis between expression of histone deacetylase 6 and clinical parameters in IgA nephropathy patients

Background

It has been demonstrated that histone deacetylase 6 (HDAC6) is involved in various kidney diseases in experimental study. However, correlation between HDAC6 and clinical parameters in IgA nephropathy (IgAN) patients is still unknown.

Methods

A total of 46 human kidney biopsy specimens with IgAN were selected as observation group, specimens of normal renal cortex tissue that was not affected by the tumor from patients with renal carcinoma (n = 7) served as control. We investigated the relationship between HDAC6 and clinical parameters in IgAN.

Results

HDAC6 was highly expressed in human kidney biopsy specimens with IgAN compared with control group, while the number of acetyl histone H3 positive cells were significantly decreased. There was a statistical difference in the indexes of albumin, estimated glomerular filtration rate (eGFR), serum urea, serum creatinine, serum uric acid, β2-microglobulin, cystatin C, cholesterol, high-density lipoprotein, low-density lipoprotein, and HDAC6 positive area among the different Oxford Classification (p < 0.05). The expression of HDAC6 was different in various eGFR levels, the expression of HDAC6 increased with the decreasing of eGFR level, the expression of acetyl histone H3 decreased with the decreasing of eGFR level. In addition, the expression of HDAC6 positively correlated with Masson trichrome positive area, serum urea, serum creatinine, β2 macroglobulin, and cystatin C, while negatively correlated with eGFR and acetyl histone H3. Multivariate linear regression analysis demonstrated that eGFR and cystatin C were independently associated with HDAC6, respectively (p < 0.05).

Conclusions

These results suggested that high level of HDAC6 expression in IgAN is correlated with renal dysfunction.

Pin1 coordinates HDAC6 upregulation with cell migration in lung cancer cells

Histone deacetylase 6 (HDAC6) controls many cellular processes via its catalyzing deacetylation of downstream substrates or interacting with its partner proteins. Dysregulation of HDAC6 signaling links to many diseases. Our previous study has been reported peptidyl-prolyl cis/trans isomerase, and NIMA-interacting 1 (Pin1) involving in HDAC6-mediated cell motility. To gain insight into precisely coordination of HDAC6 and Pin1 in cell migration, shRNA-mediated gene silencing and ectopic expression were applied to manipulate protein expression level to evaluate relationship between HDAC6 and Pin1 expression. Quantitative RT-PCR and the cycloheximide (CHX) chase assay resulted in HDAC6 expression is correlated with Pin1 level in H1299 cells. It hints that the Pin1 increases HDAC6 expression through increased transcripts and posttranslational stabilization. Furthermore, wound healing assay and transwell invasion assay evidenced the contribution of Pin1 on cell motility in H1299 cells. Our data suggest that Pin1 acts as an important regulator to manage HDAC6 expression for cell motility in lung cancer cells.

The Complex Interplay between Metabolic Reprogramming and Epigenetic Alterations in Renal Cell Carcinoma

Renal cell carcinoma (RCC) is the most common malignancy affecting the kidney. Current therapies are mostly curative for localized disease, but do not completely preclude recurrence and metastization. Thus, it is imperative to develop new therapeutic strategies based on RCC biological properties. Presently, metabolic reprograming and epigenetic alterations are recognized cancer hallmarks and their interactions are still in its infancy concerning RCC. In this review, we explore RCC biology, highlighting genetic and epigenetic alterations that contribute to metabolic deregulation of tumor cells, including high glycolytic phenotype (Warburg effect). Moreover, we critically discuss available data concerning epigenetic enzymes' regulation by aberrant metabolite accumulation and their consequences in RCC emergence and progression. Finally, we emphasize the clinical relevance of uncovering novel therapeutic targets based on epigenetic reprograming by metabolic features to improve treatment and survival of RCC patients.

High-selective HDAC6 inhibitor promotes HDAC6 degradation following autophagy modulation and enhanced antitumor immunity in glioblastoma

Glioblastoma is the most fatal type of primary brain cancer, and current treatments for glioblastoma are insufficient. HDAC6 is overexpressed in glioblastoma, and siRNA-mediated knockdown of HDAC6 inhibits glioma cell proliferation. Herein, we report a high-selective HDAC6 inhibitor, J22352, which has PROTAC (proteolysis-targeting chimeras)-like property resulted in both p62 accumulation and proteasomal degradation, leading to proteolysis of aberrantly overexpressed HDAC6 in glioblastoma. The consequences of decreased HDAC6 expression in response to J22352 decreased cell migration, increased autophagic cancer cell death and significant tumor growth inhibition. Notably, J22352 reduced the immunosuppressive activity of PD-L1, leading to the restoration of host anti-tumor activity. These results demonstrate that J22352 promotes HDAC6 degradation and induces anticancer effects by inhibiting autophagy and eliciting the antitumor immune response in glioblastoma. Therefore, this highly selective HDAC6 inhibitor can be considered a potential therapeutic for the treatment of glioblastoma and other cancers.

Upregulation of long noncoding RNA PVT1 predicts unfavorable prognosis in patients with clear cell renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is one of the most malignant genitourinary diseases worldwide. Long noncoding RNAs (lncRNAs) are a class of noncoding RNAs in the human genome that are involved in RCC initiation and progression.

OBJECTIVE

To investigate the expression of PVT1 in ccRCC and evaluate its correlation with clinicopathologic characteristics and patients' survival.

METHODS

Quantitative real-time PCR was performed to examine PVT1 expression in 129 ccRCC tissue samples and matched adjacent normal tissue samples. The relationship of PVT1 expression with clinicopathologic characteristics and clinical outcome was evaluated.

RESULTS

We identified the lncRNA PVT1, which was upregulated in clear cell renal cell carcinoma (ccRCC) tissues when compared with corresponding controls. Furthermore, PVT1 expression was positively associated with gender, tumor size, pT stage, TNM stage, and Fuhrman grade. Kaplan-Meier survival analysis showed that patients with high PVT1 expression had shorter disease-free survival (DFS) and overall-survival (OS) than those with low PVT1 expression, and multivariate analysis identified PVT1 as an independent prognostic factor in ccRCC.

CONCLUSIONS

PVT1 may be an oncogene as well as may promote metastasis in ccRCC and could serve as a potential biomarker to predict the prognosis of ccRCC patients.

HDAC6 regulates microRNA-27b that suppresses proliferation, promotes apoptosis and target MET in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma. Histone deacetylase 6 (HDAC6) is frequently altered in DLBCL and inhibition of HDAC6 has potent anti-tumor effects in vitro and in vivo. We profiled miRNAs that altered in the HDAC6 knockdown DLBCL cells with NanoString nCounter assay and identified microRNA-27b (miR-27b) as the most significantly increased miRNA. We validated decreased expression of miR-27b in DLBCL tissues, and we found that low expression of miR-27b was associated with poor overall survival of patients with DLBCL. In addition, forced expression of miR-27b suppressed DLBCL cell viability and proliferation in vitro, and inhibited tumor growth in vivo. Mechanistically, Rel A/p65 is found to negatively regulate miR-27b expression, and its acetylation and block of nuclear translocalization caused by HDAC6 inhibition significantly elevates miR-27b expression. Furthermore, miR-27b targets MET and thus represses the MET/PI3K/AKT pathway. These findings highlight an important role of miR-27b in the development of DLBCL and uncover a HDAC6-Rel A/p65-miR-27b-MET signaling pathway. Elevating miR-27b through HDAC6 inhibition would be a promising strategy for DLBCL treatment.