Potential use of custirsen to treat prostate cancer

Therapeutic Potential of Clusterin Inhibition in Human Cancer

Clusterin (CLU) protein is involved in various pathophysiological processes including carcinogenesis and tumor progression. In recent years, the role of the secretory isoform has been demonstrated in tumor cells, where it inhibits apoptosis and favors the acquisition of resistance to conventional treatments used to treat cancer. To determine the possible therapeutic potential of inhibiting this protein, numerous studies have been carried out in this field. In this article, we present the existing knowledge to date on the inhibition of this protein in different types of cancer and analyze the importance it could have in the development of new therapies targeted against this disease.

Bioengineered chimeric tRNA/pre-miRNAs as prodrugs in cancer therapy

Today, biologic prodrugs have led to targeting specific tumor markers and have increased specificity and selectivity in cancer therapy. Various studies have shown the role of ncRNAs in cancer pathology and tumorigenesis and have suggested that ncRNAs, especially miRNAs, are valuable molecules in understanding cancer biology and therapeutic processes. Most miRNAs-based research and treatment are limited to chemically synthesized miRNAs. Synthetic alterations in these miRNA mimics may affect their folding, safety profile, and even biological activity. However, despite synthetic miRNA mimics produced by automated systems, various carriers could be used to achieve efficient production of bioengineered miRNAs through economical microbial fermentation. These bioengineered miRNAs as biological prodrugs could provide a new approach for safe therapeutic methods and drug production. In this regard, bioengineered chimeric miRNAs could be selectively processed to mature miRNAs in different types of cancer cells by targeting the desired gene and regulating cancer progression. In this article, we aim to review bioengineered miRNAs and their use in cancer therapy, as well as offering advances in this area, including the use of chimeric tRNA/pre-miRNAs.

The Functional Role of Prostate Cancer Metastasis-related Micro-RNAs

The mortality of patients with hormone-resistant prostate cancer can be ascribed to a large degree to metastasis to distant organs, predominantly to the bones. In this review, we discuss the contribution of micro-RNAs (miRs) to the metastatic process of prostate cancer. The criteria for selection of miRs for this review were the availability of preclinical in vivo metastasis-related data in conjunction with prognostic clinical data. Depending on their function in the metastatic process, the corresponding miRs are up- or down-regulated in prostate cancer tissues when compared to matching normal tissues. Up-regulated miRs preferentially target suppressors of cytokine signaling or tumor suppressor-related genes and metastasis-inhibitory transcription factors. Down-regulated miRs promote epithelial-mesenchymal transition or mesenchymal-epithelial transition and diverse pro-metastatic signaling pathways. Some of the discussed miRs exert their function by simultaneously targeting epigenetic pathways as well as cell-cycle-related, anti-apoptotic and signaling-promoting targets. Finally, we discuss potential therapeutic options for the treatment of prostate cancer-related metastases by substitution or inhibition of miRs.

Glyceryl trinitrate‑induced cytotoxicity of docetaxel‑resistant prostatic cancer cells is associated with differential regulation of clusterin

Metastatic castration resistant prostate cancer (mCRPC) relapse due to acquired resistance to chemotherapy, such as docetaxel, remains a major threat to patient survival. Resistance of mCRPC to docetaxel can be associated with elevated levels of soluble clusterin (sCLU) and growth differentiation factor‑15 (GDF‑15). Any strategies aiming to modulate sCLU and/or GDF‑15 in docetaxel‑resistant prostate cancer cells present a therapeutic interest. The present study reports the cytotoxic effect of a nitric oxide donor, glyceryl trinitrate (GTN), on docetaxel‑resistant mCRPC human cell lines and demonstrates that GTN displays greater inhibition of cell viability toward docetaxel‑resistant mCRPC cells than on mCRPC cells. It is also demonstrated that GTN modulates the level of expression of clusterin (CLU) which is dependent of GDF‑15, two markers associated with docetaxel resistance in prostate cancer. The results indicate that GTN represses the level of expression of the cytoprotective isoform of CLU (sCLU) and can increase the level of expression of the cytotoxic isoform (nuclear CLU) in docetaxel resistant cells. Furthermore, it was observed that GTN differentially regulates the level of the precursor form of GDF‑15 between resistant and parental cells, and that recombinant GDF‑15 can modulate the expression of CLU isoforms and counteract GTN‑induced cytotoxicity in resistant cells. A link was established between GDF‑15 and the expression of CLU isoforms. The present study thus revealed GTN as a potential therapeutic strategy to overcome docetaxel‑resistant mCRPC.

Meta-analysis of efficacy and safety of custirsen in patients with metastatic castration-resistant prostate cancer

Custirsen is the second-generation antisense oligonucleotide (ASO), which can reduce cellular levels of clusterin to increase the cytotoxic effect of chemotherapeutic drugs. Our study assessed the efficacy and safety of custirsen in patients with metastatic castration-resistant prostate cancer (mCRPC).We conducted a comprehensive search to identify all the randomized controlled trials (RCTs) of custirsen for the treatment of mCRPC. The reference lists of the retrieved studies were investigated.Three publications involving a total of 1709 patients were used in the analysis. We found that overall survival (OS) (P = .25) was not statistically significant in the comparison. Safety assessments indicated custirsen were often associated with complications resulting from neutropenia (P < .001), anaemia (P < .001), thrombocytopenia (P < .001), and diarrhea (P = .002).Our meta-analysis shows that custirsen has no obvious effect on improving the OS of patients with mCRPC. Adverse reactions were more common among those patients treated with custirsen as compared to those treated with placebo.

O-linked N-acetylglucosamine transferase enhances secretory clusterin expression via liver X receptors and sterol response element binding protein regulation in cervical cancer

O-linked N-acetylglucosamine transferase (OGT) expression is increased in various cancer types, indicating the potential importance of O-GlcNAcylation in tumorigenesis. Secretory clusterin (sCLU) is involved in cancer cell proliferation and drug resistance, and recently, liver X receptors (LXRs) and sterol response element binding protein-1 (SREBP-1) were reported to regulate sCLU transcription. Here, we found that sCLU is significantly increased in cervical cancer cell lines, which have higher expression levels of O-GlcNAc and OGT than keratinocytes. OGT knockdown decreased expression of LXRs, SREBP-1 and sCLU through hypo-O-GlcNAcylation of LXRs. Additionally, treatment with Thiamet G, O-GlcNAcase OGA inhibitor, increased expression of O-GlcNAcylation and sCLU, and high glucose increased levels of LXRs, SREBP-1 and sCLU in HeLa cells. Moreover, OGT knockdown induced G₀/G₁ phase cell cycle arrest and late apoptosis in cisplatin-treated HeLa cells, and decreased viability compared to OGT intact HeLa cells. Taken together, these findings suggest that OGT, O-GlcNAcylated LXRs, and SREBP-1 increase sCLU expression in cervical cancer cells, which contributes to drug resistance.

Clusterin and neuropilin-2 as potential biomarkers of tumor progression in benzo[a]pyrene-transformed 16HBE cells xenografted nude mouse model

Benzo[a]pyrene (BaP) is a ubiquitous environment contaminant and its exposure could increase incidence of human lung cancer. In order to confirm and compare potential biomarkers of BaP-induce carcinogenesis and tumor progression, time-dependent changes of clusterin (CLU) and neuropilin-2 (NRP2) levels were evaluated in sera of BaP-transformed 16HBE cell line T-16HBE-C1 cells xenografted nude mice. Performance of CLU and NRP2 on tissue classification and tumor progression forecast was also calculated. Levels of CLU and NRP2 were significant elevated in both culture supernatant of T-16HBE-C1 cells and sera of T-16HBE-C1 cells xenografted nude mice compared with control. CLU and NRP2 were both found positively stained in tumor tissue. CLU and NRP2 alone could well predicate tumor progression in nude mice and CLU appeared to be more sensitive than NRP2. When both of them combined, performance of predication would improve. In conclusion, CLU and NRP2 could serve as potential biomarkers of tumor progression in nude mice xenografted with T-16HBE-C1 cells.

Addressing taxane resistance in metastatic castration-resistant prostate cancer: a focus on chaperone proteins

Despite the significant survival benefit of taxane therapy in metastatic castration-resistant prostate cancer (mCRPC), all patients inevitably develop treatment resistance. An understanding of resistance mechanisms has led to new therapies for prostate cancer (cabazitaxel, abiraterone and enzalutamide), all of which have improved survival following first-line docetaxel. Another treatment, currently in development, targets the prosurvival molecule clusterin. Custirsen, an antisense molecule that inhibits clusterin production, has shown promise in combination with docetaxel in mCRPC patients at risk for poor outcomes. Although optimal sequence and combination of available therapies is unclear, the heterogeneity of mCRPC suggests a continuing need for personalized treatment regimens and improved abilities to predict which patients will respond to the available treatment options.

Oligonucleotide-Based Drug Development: Considerations for Clinical Pharmacology and Immunogenicity

The field of oligonucleotide (OGN)-based therapeutics has been growing dramatically in the past decade, providing innovative platforms to develop agents for the treatment of a wide variety of clinical conditions. OGN agents have unique physicochemical properties and pharmacokinetic/pharmacodynamic characteristics. This review considers findings from the literature and information on new molecular entities submitted to the US Food and Drug Administration as OGN-based therapeutics. In addition, the article discusses several challenging issues from the perspective of clinical pharmacology, emphasizing the potential of immunogenicity, the effect of renal impairment on OGN exposure, drug-drug interactions, and the utility of pharmacokinetic/pharmacodynamic modeling. The field of OGN-based therapeutics is in evolution and will benefit from further studies as well as clinical experience to formulate guidelines and promote the development of this class of agents.

Metastatic castration-resistant prostate cancer: time for innovation

Androgen deprivation is the mainstay of advanced prostate cancer treatment. Despite initial responses, almost all patients progress to castration-resistant prostate cancer (CRPC). The understanding of the biology of CRPC and the evidence that CRPC still remains driven by androgen receptor signaling led to the discovery of new therapeutic targets. In the last few years, large Phase III trials showed improvements in survival and outcomes and led to the approval of a CYP17 inhibitor (abiraterone), an androgen receptor antagonist (enzalutamide), the taxane cabazitaxel, an α-emitter (radium-223), the bone resorption-targeting drug denosumab and an immunotherapy (sipuleucel-T). This article describes the molecular mechanisms underlying castration resistance, discusses recent and ongoing trials and offers some insights into identifying the best sequence of new drugs.

Pten Regulates Epithelial Cytodifferentiation during Prostate Development

Gene expression and functional studies have indicated that the molecular programmes involved in prostate development are also active in prostate cancer. PTEN has been implicated in human prostate cancer and is frequently mutated in this disease. Here, using the Nkx3.1:Cre mouse strain and a genetic deletion approach, we investigate the role of Pten specifically in the developing mouse prostate epithelia. In contrast to its role in other developing organs, this gene is dispensable for the initial developmental processes such as budding and branching. However, as cytodifferentiation progresses, abnormal luminal cells fill the ductal lumens together with augmented epithelial proliferation. This phenotype resembles the hyperplasia seen in postnatal Pten deletion models that develop neoplasia at later stages. Consistent with this, gene expression analysis showed a number of genes affected that are shared with Pten mutant prostate cancer models, including a decrease in androgen receptor regulated genes. In depth analysis of the phenotype of these mice during development revealed that loss of Pten leads to the precocious differentiation of epithelial cells towards a luminal cell fate. This study provides novel insight into the role of Pten in prostate development as part of the process of coordinating the differentiation and proliferation of cell types in time and space to form a functional organ.

[New therapies in metastatic castration resistant prostate cancer]

Therapeutic arsenal in prostate cancer widens for several years. New hormonal therapies such as acetate abiraterone or enzalutamide were the first molecules to revolutionize the treatment of metastatic castration resistant prostate cancer. Several other treatments are on trial targeting different pathways: androgene pathway (TAK-007, ARN-509, ODM-201, TOK-001), immune system (sipuleucel, ipilimumab, PROSTVAC-V/F, tasquinimod), but also tumor cell (PARP inhibitor, cabozantinib). The treatment sequencing will therefore soon be problematic, raising the necessity to identify predictive markers of response to the new therapies.

Current and emerging therapies for bone metastatic castration-resistant prostate cancer

BACKGROUND

A paucity of therapeutic options is available to treat men with metastatic castration-resistant prostate cancer (mCRPC). However, recent developments in our understanding of the disease have resulted in several new therapies that show promise in improving overall survival rates in this patient population.

METHODS

Agents approved for use in the United States and those undergoing clinical trials for the treatment of mCRPC are reviewed. Recent contributions to the understanding of prostate biology and bone metastasis are discussed as well as how the underlying mechanisms may represent opportunities for therapeutic intervention. New challenges to delivering effective mCRPC treatment will also be examined.

RESULTS

New and emerging treatments that target androgen synthesis and utilization or the microenvironment may improve overall survival rates for men diagnosed with mCRPC. Determining how factors derived from the primary tumor can promote the development of premetastatic niches and how prostate cancer cells parasitize niches in the bone microenvironment, thus remaining dormant and protected from systemic therapy, could yield new therapies to treat mCRPC. Challenges such as intratumoral heterogeneity and patient selection can potentially be circumvented via computational biology approaches.

CONCLUSIONS

The emergence of novel treatments for mCRPC, combined with improved patient stratification and optimized therapy sequencing, suggests that significant gains may be made in terms of overall survival rates for men diagnosed with this form of cancer.

Cytotoxic chemotherapy in the contemporary management of metastatic castration-resistant prostate cancer (mCRPC)

For several years, docetaxel was the only treatment shown to improve survival of patients with metastatic castration-resistant prostate cancer (mCRPC). There are now several novel agents available, although chemotherapy with docetaxel and cabazitaxel continues to play an important role. However, the increasing number of available agents will inevitably affect the timing of chemotherapy and therefore it may be important to offer this approach before declining performance status renders patients ineligible for chemotherapy. Patient selection is also important to optimise treatment benefit. The role of predictive biomarkers has assumed greater importance due to the development of multiple agents and resistance to available agents. In addition, the optimal sequence of treatments remains undefined and requires further study in order to maximize long-term outcomes. We provide an overview of the clinical data supporting the role of chemotherapy in the treatment of mCRPC and the emerging role in metastatic castration-sensitive prostate cancer. We review the key issues in the management of patients including selection of patients for chemotherapy, when to start chemotherapy, and how best to sequence treatments to maximise outcomes. In addition, we briefly summarise the promising new chemotherapeutic agents in development in the context of emerging therapies.

Nanoways to overcome docetaxel resistance in prostate cancer

Prostate cancer is the most common non-cutaneous malignancy in American men. Docetaxel is a useful chemotherapeutic agent for prostate cancer that has been available for over a decade, but the length of the treatment and systemic side effects hamper compliance. Additionally, docetaxel resistance invariably emerges, leading to disease relapse. Docetaxel resistance is either intrinsic or acquired by adopting various mechanisms that are highly associated with genetic alterations, decreased influx and increased efflux of drugs. Several combination therapies and small P-glycoprotein inhibitors have been proposed to improve the therapeutic potential of docetaxel in prostate cancer. Novel therapeutic strategies that may allow reversal of docetaxel resistance include alterations of enzymes, improving drug uptake and enhancement of apoptosis. In this review, we provide the most current docetaxel reversal approaches utilizing nanotechnology. Nanotechnology mediated docetaxel delivery is superior to existing therapeutic strategies and a more effective method to induce P-glycoprotein inhibition, enhance cellular uptake, maintain sustained drug release, and improve bioavailability.

Clusterin: a key player in cancer chemoresistance and its inhibition

Clusterin is a heterodimeric disulfide-linked glycoprotein (449 amino acids) isolated in the rat prostate after castration. It is widely distributed in different tissues and highly conserved in species. There are two isoforms (1 and 2) with antagonistic actions regarding apoptosis. Clusterin is implicated in a number of biological processes, including lipid transport, membrane recycling, cell adhesion, programmed cell death, and complement cascade, representing a truly multifunctional protein. Isoform 2 is overexpressed under cellular stress conditions and protects cells from apoptosis by impeding Bax actions on the mitochondrial membrane and exerts other protumor activities, like phosphatidylinositol 3-kinase/protein kinase B pathway activation, modulation of extracellular signal-regulated kinase 1/2 signaling and matrix metallopeptidase-9 expression, increased angiogenesis, modulation of the nuclear factor kappa B pathway, among others. Its overexpression should be considered as a nonspecific cellular response to a wide variety of tissue insults like cytotoxic chemotherapy, radiation, excess of free oxygen radicals, androgen or estrogen deprivation, etc. A review of the recent literature strongly suggests potential roles for custirsen in particular, and proapoptosis treatments in general, as novel modalities in cancer management. Inhibition of clusterin is known to increase the cytotoxic effects of chemotherapeutic agents, and custirsen, a second-generation antisense oligonucleotide that blocks clusterin, is being tested in a Phase III clinical trial after successful results were achieved in Phase II studies. A major issue in cancer evolution that remains unanswered is whether clusterin represents a driving force of tumorigenesis or a late phenomenon after chemotherapy. This review presents preclinical data that encourages trials in various types of cancer other than advanced castration-resistance prostate cancer and discusses briefly the appropriate timing for clusterin inhibition in the clinical context.

Senescent remodeling of the innate and adaptive immune system in the elderly men with prostate cancer

Despite years of intensive investigation that has been made in understanding prostate cancer, it remains a major cause of death in men worldwide. Prostate cancer emerges from multiple alterations that induce changes in expression patterns of genes and proteins that function in networks controlling critical cellular events. Based on the exponential aging of the population and the increasing life expectancy in industrialized Western countries, prostate cancer in the elderly men is becoming a disease of increasing significance. Aging is a progressive degenerative process strictly integrated with inflammation. Several theories have been proposed that attempt to define the role of chronic inflammation in aging including redox stress, mitochondrial damage, immunosenescence, and epigenetic modifications. Here, we review the innate and adaptive immune systems and their senescent remodeling in elderly men with prostate cancer.

A hybrid lipid oligonucleotide: a versatile tool for supramolecular chemistry

Lipid oligonucleotides (LONs) self-assemble into supramolecular structures. This property has an impact on the biological effects of the oligonucleotide sequences.