Androgen deprivation-induced elevated nuclear SIRT1 promotes prostate tumor cell survival by reactivation of AR signaling

A forward genetic screen identifies Sirtuin1 as a driver of neuroendocrine prostate cancer

Although localized prostate cancer is relatively indolent, advanced prostate cancer manifests with aggressive and often lethal variants, including neuroendocrine prostate cancer (NEPC). To identify drivers of aggressive prostate cancer, we leveraged Sleeping Beauty (SB) transposon mutagenesis in a mouse model based on prostate-specific loss-of-function of Pten and Tp53 . Compared with control mice, SB mice developed more aggressive prostate tumors, with increased incidence of metastasis. Notably, a significant percentage of the SB prostate tumors display NEPC phenotypes, and the transcriptomic features of these SB mouse tumors recapitulated those of human NEPC. We identified common SB transposon insertion sites (CIS) and prioritized associated CIS-genes differentially expressed in NEPC versus non-NEPC SB tumors. Integrated analysis of CIS-genes encoding for proteins representing upstream, post-translational modulators of master regulators controlling the transcriptional state of SB -mouse and human NEPC tumors identified sirtuin 1 ( Sirt1 ) as a candidate mechanistic determinant of NEPC. Gain-of-function studies in human prostate cancer cell lines confirmed that SIRT1 promotes NEPC, while its loss-of-function or pharmacological inhibition abrogates NEPC. This integrative analysis is generalizable and can be used to identify novel cancer drivers for other malignancies.

Summary

Using an unbiased forward mutagenesis screen in an autochthonous mouse model, we have investigated mechanistic determinants of aggressive prostate cancer. SIRT1 emerged as a key regulator of neuroendocrine prostate cancer differentiation and a potential target for therapeutic intervention.

Targeting S6K/NFκB/SQSTM1/Polθ signaling to suppress radiation resistance in prostate cancer

In this study we have identified POLθ-S6K-p62 as a novel druggable regulator of radiation response in prostate cancer. Despite significant advances in delivery, radiotherapy continues to negatively affect treatment outcomes and quality of life due to resistance and late toxic effects to the surrounding normal tissues such as bladder and rectum. It is essential to develop new and effective strategies to achieve better control of tumor. We found that ribosomal protein S6K (RPS6KB1) is elevated in human prostate tumors, and contributes to resistance to radiation. As a downstream effector of mTOR signaling, S6K is known to be involved in growth regulation. However, the impact of S6K signaling on radiation response has not been fully explored. Here we show that loss of S6K led to formation of smaller tumors with less metastatic ability in mice. Mechanistically we found that S6K depletion reduced NFκB and SQSTM1 (p62) reporter activity and DNA polymerase θ (POLθ) that is involved in alternate end-joining repair. We further show that the natural compound berberine interacts with S6K in a in a hitherto unreported novel mode and that pharmacological inhibition of S6K with berberine reduces Polθ and downregulates p62 transcriptional activity via NFκB. Loss of S6K or pre-treatment with berberine improved response to radiation in prostate cancer cells and prevented radiation-mediated resurgence of PSA in animals implanted with prostate cancer cells. Notably, silencing POLQ in S6K overexpressing cells enhanced response to radiation suggesting S6K sensitizes prostate cancer cells to radiation via POLQ. Additionally, inhibition of autophagy with CQ potentiated growth inhibition induced by berberine plus radiation. These observations suggest that pharmacological inhibition of S6K with berberine not only downregulates NFκB/p62 signaling to disrupt autophagic flux but also decreases Polθ. Therefore, combination treatment with radiation and berberine inhibits autophagy and alternate end-joining DNA repair, two processes associated with radioresistance leading to increased radiation sensitivity.

NAD+ mediated photoelectrochemical biosensor for histone deacetylase Sirt1 detection based on CuO-BiVO4-AgNCs heterojunction and hybridization chain reaction amplification

BACKGROUND

Histone deacetylate Sirt1 has been involved in many important biological processes and is closely related to the occurrence and development of many diseases. Therefore, the accurate detection of Sirt1 is of great significance for the diagnosis and treatment of diseases caused by Sirt1 and the development of related drugs.

RESULTS

In this work, a photoelectrochemical biosensor was developed for Sirt1 detection based on the NAD + mediated Sirt1 recognition and E. Coli DNA ligase activity. CuO-BiVO4p-n heterojunction was employed as the photoactive material, rolling circle amplification (RCA), hybridization chain reaction (HCR) and AgNCs were used as triple signal amplifications. As a bifunctional cofactor, NAD+ played a crucial role for Sirt1 detection, where the peptide deacetylation catalyzed by Sirt1 consumed NAD+, and the decreased amount of NAD + inhibited the activity of E. Coli DNA ligase, leading to the failure on RCA reaction, and improving the HCR reaction. Finally, AgNCs were generated using C-rich DNA as carrier. The surface plasmon effect of AgNCs and its heterojunction with CuO and BiVO4 accelerated the transfer rate of photogenerated carriers and improved the photocurrent signal. When the detection range was 0.001-200 nM, the detection limit of the biosensor was 0.76 pM (S/N = 3).

SIGNIFICANCE

The applicability of the method was evaluated by studying the effects of known inhibitors nicotinamide and environmental pollutant halogenated carbazole on Sirt1 enzyme activity. The results showed that this method can be used as a new platform for screening Sirt1 enzyme inhibitors, and also provided a new biomarker for evaluating the ecotoxicological effects of environmental pollutants.

Discovery of selective and potent USP22 inhibitors via structure-based virtual screening and bioassays exerting anti-tumor activity

Ubiquitin-specific protease 22 (USP22) plays a prominent role in tumor development, invasion, metastasis and immune reprogramming, which has been proposed as a potential therapeutic target for cancer. Herein, we employed a structure-based discovery and biological evaluation and discovered that Rottlerin (IC50 = 2.53 μM) and Morusin (IC50 = 8.29 μM) and as selective and potent USP22 inhibitors. Treatment of HCT116 cells and A375 cells with each of the two compounds resulted in increased monoubiquitination of histones H2A and H2B, as well as reduced protein expression levels of Sirt1 and PD-L1, all of which are known as USP22 substrates. Additionally, our study demonstrated that the administration of Rottlerin or Morusin resulted in an increase H2Bub levels, while simultaneously reducing the expression of Sirt1 and PD-L1 in a manner dependent on USP22. Furthermore, Rottlerin and Morusin were found to enhance the degradation of PD-L1 and Sirt1, as well as increase the polyubiquitination of endogenous PD-L1 and Sirt1 in HCT116 cells. Moreover, in an in vivo syngeneic tumor model, Rottlerin and Morusin exhibited potent antitumor activity, which was accompanied by an enhanced infiltration of T cells into the tumor tissues. Using in-depth molecular dynamics (MD) and binding free energy calculation, conserved residue Leu475 and non-conserved residue Arg419 were proven to be crucial for the binding affinity and inhibitory function of USP22 inhibitors. In summary, our study established a highly efficient approach for USP22-specific inhibitor discovery, which lead to identification of two selective and potent USP22 inhibitors as potential drugs in anticancer therapy.

Emerging therapeutic strategy for mitigating cancer progression through inhibition of sirtuin-1 and epithelial-mesenchymal transition

With 8.8 million deaths worldwide, cancer is the major reason for the high rate of fatalities. Malignancy's commencement, progression, development, metastasis, and therapy resistance have all been correlated with the epithelial-to-mesenchymal transition (EMT) pathway. EMT promotes the cancer cells' metastatic spread and starts the development of treatment resistance. Sirtuin-1 (SIRT1) is a histone deacetylase that is important for signaling, cell persistence, and apoptosis. It does this by deacetylating important cell signaling molecules and proteins that are associated with apoptosis. The function of SIRT1 in EMT and cancer progression, as well as the emerging therapeutic strategy of treating cancer through the inhibition of SIRT1 and EMT will be discussed in detail.

Drastic Synergy of Lovastatin and Antrodia camphorata Extract Combination against PC3 Androgen-Refractory Prostate Cancer Cells, Accompanied by AXL and Stemness Molecules Inhibition

Prostate cancer (PC) is the second most frequently diagnosed cancer and the fifth leading cause of cancer-related death in males worldwide. Early-stage PC patients can benefit from surgical, radiation, and hormonal therapies; however, once the tumor transitions to an androgen-refractory state, the efficacy of treatments diminishes considerably. Recently, the exploration of natural products, particularly dietary phytochemicals, has intensified in response to addressing this prevailing medical challenge. In this study, we uncovered a synergistic effect from combinatorial treatment with lovastatin (an active component in red yeast rice) and Antrodia camphorata (AC, a folk mushroom) extract against PC3 human androgen-refractory PC cells. This combinatorial modality resulted in cell cycle arrest at the G0/G1 phase and induced apoptosis, accompanied by a marked reduction in molecules responsible for cellular proliferation (p-Rb/Rb, Cyclin A, Cyclin D1, and CDK1), aggressiveness (AXL, p-AKT, and survivin), and stemness (SIRT1, Notch1, and c-Myc). In contrast, treatment with either AC or lovastatin alone only exerted limited impacts on the cell cycle, apoptosis, and the aforementioned signaling molecules. Notably, significant reductions in canonical PC stemness markers (CD44 and CD133) were observed in lovastatin/AC-treated PC3 cells. Furthermore, lovastatin and AC have been individually examined for their anti-PC properties. Our findings elucidate a pioneering discovery in the synergistic combinatorial efficacy of AC and clinically viable concentrations of lovastatin on PC3 PC cells, offering novel insights into improving the therapeutic effects of dietary natural products for future strategic design of therapeutics against androgen-refractory prostate cancer.

Melatonin Modulates the SIRT1-Related Pathways via Transdermal Cryopass-Laser Administration in Prostate Tumor Xenograft

Melatonin displays antitumor activity in several types of malignancies; however, the best delivery route and the underlying mechanisms are still unclear. Alternative non-invasive delivery route based on transdermal administration of melatonin by cryopass-laser treatment demonstrated efficiency in reducing the progression of LNCaP prostate tumor cells xenografted into nude mice by impairing the biochemical pathways affecting redox balance. Here, we investigated the impact of transdermal melatonin on the tumor dimension, microenvironment structure, and SIRT1-modulated pathways. Two groups (vehicle cryopass-laser and melatonin cryopass-laser) were treated for 6 weeks (3 treatments per week), and the tumors collected were analyzed for hematoxylin eosin staining, sirius red, and SIRT1 modulated proteins such as PGC-1α, PPARγ, and NFkB. Melatonin in addition to simple laser treatment was able to boost the antitumor cancer activity impairing the tumor microenvironment, increasing the collagen structure around the tumor, and modulating the altered SIRT1 pathways. Transdermal application is effective, safe, and feasible in humans as well, and the significance of these findings necessitates further studies on the antitumor mechanisms exerted by melatonin.

Dimethylarginine Dimethylaminohydrolase - 1 expression is increased under tBHP-induced oxidative stress regulates nitric oxide production in PCa cells attenuates mitochondrial ROS-mediated apoptosis

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) expression is frequently elevated in different cancers including prostate cancer (PCa) and enhances nitric oxide (NO) production in tumor cells by metabolising endogenous nitric oxide synthase (NOS) inhibitors. DDAH1 protects the PCa cells from cell death and promotes survival. In this study, we have investigated the cytoprotective role of DDAH1 and determined the mechanism of DDAH1 in protecting the cells in tumor microenvironment. Proteomic analysis of PCa cells with stable overexpression of DDAH1 has identified that oxidative stress-related activity is altered. Oxidative stress promotes cancer cell proliferation, survival and causes chemoresistance. A known inducer of oxidative stress, tert-Butyl Hydroperoxide (tBHP) treatment to PCa cells led to elevated DDAH1 level that is actively involved in protecting the PCa cells from oxidative stress induced cell damage. In PC3-DDAH1- cells, tBHP treatment led to higher mROS levels indicating that the loss of DDAH1 increases the oxidative stress and eventually leads to cell death. Under oxidative stress, nuclear Nrf2 controlled by SIRT1 positively regulates DDAH1 expression in PC3 cells. In PC3-DDAH1+ cells, tBHP induced DNA damage is well tolerated compared to wild-type cells while PC3-DDAH1- became sensitive to tBHP. In PC3 cells, tBHPexposure has increased the production of NO and GSH which may be acting as an antioxidant defence to overcome oxidative stress. Furthermore, in tBHP treated PCa cells, DDAH1 is controlling the expression of Bcl2, active PARP and caspase 3. Taken together, these results confirm that DDAH1 is involved in the antioxidant defence system and promotes cell survival.

Epigenetic (De)regulation in Prostate Cancer

Prostate cancer (PCa) is a heterogeneous disease exhibiting both genetic and epigenetic deregulations. Epigenetic alterations are defined as changes not based on DNA sequence, which include those of DNA methylation, histone modification, and chromatin remodeling. Androgen receptor (AR) is the main driver for PCa and androgen deprivation therapy (ADT) remains a backbone treatment for patients with PCa; however, ADT resistance almost inevitably occurs and advanced diseases develop termed castration-resistant PCa (CRPC), due to both genetic and epigenetic changes. Due to the reversible nature of epigenetic modifications, inhibitors targeting epigenetic factors have become promising anti-cancer agents. In this chapter, we focus on recent studies about the dysregulation of epigenetic regulators crucially involved in the initiation, development, and progression of PCa and discuss the potential use of inhibitors targeting epigenetic modifiers for treatment of advanced PCa.

Druggable Metabolic Vulnerabilities Are Exposed and Masked during Progression to Castration Resistant Prostate Cancer

There is an urgent need for exploring new actionable targets other than androgen receptor to improve outcome from lethal castration-resistant prostate cancer. Tumor metabolism has reemerged as a hallmark of cancer that drives and supports oncogenesis. In this regard, it is important to understand the relationship between distinctive metabolic features, androgen receptor signaling, genetic drivers in prostate cancer, and the tumor microenvironment (symbiotic and competitive metabolic interactions) to identify metabolic vulnerabilities. We explore the links between metabolism and gene regulation, and thus the unique metabolic signatures that define the malignant phenotypes at given stages of prostate tumor progression. We also provide an overview of current metabolism-based pharmacological strategies to be developed or repurposed for metabolism-based therapeutics for castration-resistant prostate cancer.

The Mechanistic Roles of Sirtuins in Breast and Prostate Cancer

Simple Summary

There are diverse reports of the dual role of sirtuin genes and proteins in breast and prostate cancers. This review discusses the current information on the tumor promotion or suppression roles of SIRT1–7 in breast and prostate cancers. Precisely, we highlight that sirtuins regulate various proteins implicated in proliferation, apoptosis, autophagy, chemoresistance, invasion, migration, and metastasis of both breast and prostate cancer. We also provide evidence of the direct regulation of sirtuins by miRNAs, highlighting the consequences of this regulation in breast and prostate cancer. Overall, this review reveals the potential value of sirtuins as biomarkers and/or targets for improved treatment of breast and prostate cancers.

Abstract

Mammalian sirtuins (SIRT1–7) are involved in a myriad of cellular processes, including apoptosis, proliferation, differentiation, epithelial-mesenchymal transition, aging, DNA repair, senescence, viability, survival, and stress response. In this review, we discuss the current information on the mechanistic roles of SIRT1–7 and their downstream effects (tumor promotion or suppression) in cancers of the breast and prostate. Specifically, we highlight the involvement of sirtuins in the regulation of various proteins implicated in proliferation, apoptosis, autophagy, chemoresistance, invasion, migration, and metastasis of breast and prostate cancer. Additionally, we highlight the available information regarding SIRT1–7 regulation by miRNAs, laying much emphasis on the consequences in the progression of breast and prostate cancer.

PGC1 alpha coactivates ERG fusion to drive antioxidant target genes under metabolic stress

The presence of ERG gene fusion; from developing prostatic intraepithelial neoplasia (PIN) lesions to hormone resistant high grade prostate cancer (PCa) dictates disease progression, altered androgen metabolism, proliferation and metastasis^1–3. ERG driven transcriptional landscape may provide pro-tumorigenic cues in overcoming various strains like hypoxia, nutrient deprivation, inflammation and oxidative stress. However, insights on the androgen independent regulation and function of ERG during stress are limited. Here, we identify PGC1α as a coactivator of ERG fusion under various metabolic stress. Deacetylase SIRT1 is necessary for PGC1α-ERG interaction and function. We reveal that ERG drives the expression of antioxidant genes; SOD1 and TXN, benefitting PCa growth. We observe increased expression of these antioxidant genes in patients with high ERG expression correlates with poor survival. Inhibition of PGC1α-ERG axis driven transcriptional program results in apoptosis and reduction in PCa xenografts. Here we report a function of ERG under metabolic stress which warrants further studies as a therapeutic target for ERG fusion positive PCa.

PGC1α acts as a co-activator of the ERG transcription factor during metabolic stress resulting in antioxidant functionsand inhibition of the PGC1α-ERG driven transcriptional program reduces prostate cancer growth by inducing ROS mediated apoptosis.

SIRT1 inhibition-induced senescence as a strategy to prevent prostate cancer progression

Emerging evidence suggests an important role for SIRT1, a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase in cancer development, progression and therapeutic resistance; making it a viable therapeutic target. Here, we examined the impact of resveratrol-mediated pharmacological activation of SIRT1 on the progression of HGPIN lesions (using the Pten^-/- mouse model) and on prostate tumor development (using an orthotopic model of prostate cancer cells stably silenced for SIRT1). We show that precise SIRT1 modulation could benefit both cancer prevention and treatment. Positive effect of SIRT1 activation can prevent Pten deletion-driven development of HGPIN lesions in mice if resveratrol is administered early (pre-cancer stage) with little to no benefit after the establishment of HGPIN lesions or tumor cell implantation. Mechanistically, our results show that under androgen deprivation conditions, SIRT1 inhibition induces senescence as evidenced by decreased gene signature associated with negative regulators of senescence and increased senescence-associated β-galactosidase activity. Furthermore, pharmacological inhibition of SIRT1 potentiated growth inhibitory effects of clinical androgen receptor blockade agents and radiation. Taken together, our findings provide an explanation for the discrepancy regarding the role of SIRT1 in prostate tumorigenesis. Our results reveal that the bifurcated roles for SIRT1 may occur in stage and context-dependent fashion by functioning in an antitumor role in prevention of early-stage prostate lesion development while promoting tumor development and disease progression post-lesion development. Clinically, these data highlight the importance of precise SIRT1 modulation to provide benefits for cancer prevention and treatment including sensitization to conventional therapeutic approaches.

SYT8 promotes pancreatic cancer progression via the TNNI2/ERRα/SIRT1 signaling pathway

Pancreatic cancer is a highly lethal malignancy due to failures of early detection and high metastasis in patients. While certain genetic mutations in tumors are associated with severity, the molecular mechanisms responsible for cancer progression are still poorly understood. Synaptotagmin-8 (SYT8) is a membrane protein that regulates hormone secretion and neurotransmission, and its expression is positively regulated by the promoter of the insulin gene in pancreatic islet cells. In this study, we identified a previously unknown role of SYT8 in altering tumor characteristics in pancreatic cancer. SYT8 levels were upregulated in patient tumors and contributed towards increased cell proliferation, migration, and invasion in vitro and in vivo. Increased SYT8 expression also promoted tumor metastasis in an in vivo tumor metastasis model. Furthermore, we showed that SYT8-mediated increase in tumorigenicity was regulated by SIRT1, a protein deacetylase previously known to alter cell metabolism in pancreatic lesions. SIRT1 expression was altered by orphan nuclear receptor ERRα and troponin-1 (TNNI2), resulting in cell proliferation and migration in an SYT8-dependent manner. Together, we identified SYT8 to be a central regulator of tumor progression involving signaling via the SIRT1, ERRα, and TNNI2 axis. This knowledge may provide the basis for the development of therapeutic strategies to restrict tumor metastasis in pancreatic cancer.