SIRT4 and SIRT6 Serve as Novel Prognostic Biomarkers With Competitive Functions in Serous Ovarian Cancer

β-1,3-glucan from Euglena gracilis: a promising epidrug targeting epigenetic regulators PRMTs and SIRTs for therapeutic applications in ovarian cancer

Natural products serve as a valuable resource in drug discovery and the identification of bioactive molecules in the field of epimedicine, which targets epigenetic regulator enzymes through epidrugs. In this study, β-1,3-glucan (BG), a natural storage polysaccharide in Euglena gracilis, a well-known immunostimulatory agent, is propounded as a promising epidrug. To elucidate the therapeutic efficacy of BG against ovarian cancer, the molecular interactions between BG and epigenetic regulators, Protein Arginine Methyltransferases (PRMTs) and Sirtuins (SIRTs) were investigated using computational methods followed by in vitro gene expression studies in SKOV-3 ovarian cancer cell line. The binding energies of PRMT5 and SIRT5 against BG were observed as -65.5 and -68.2 kcal/mol, respectively. The in vitro cytotoxic effects of BG against human ovarian cancer cell line, SKOV-3 showed an IC50 of 150 µg/mL at 48 h. Significant epigenetic modifications were observed to be influenced by BG which increased the gene expression of PRMT5, SIRT5 and Nrf2 to 0.3, 0.5, and 0.7 fold-change respectively, while the Nrf1/2 plasmid showed reduced reporter activity by 29%. Collectively, both in silico and in vitro studies provided valuable insights into the epigenetic regulation of PRMT5 and SIRT5 by BG via Nrf1/2. Nonetheless, further preclinical and clinical investigations are essential to validate the therapeutic properties of BG as an epidrug against ovarian cancer.

Cisplatin-induced PANDAR-Chemo-EVs contribute to a more aggressive and chemoresistant ovarian cancer phenotype through the SRSF9-SIRT4/SIRT6 axis

OBJECTIVE

We previously elucidated that long non-coding RNA Promoter of CDKN1A Antisense DNA damage Activated RNA (PANDAR) as a p53-dependent oncogene to promote cisplatin resistance in ovarian cancer (OC). Intriguingly, high level of p53-independent PANDAR was found in cisplatin-resistant patients with p53 mutation. Here, our study probed the new roles and the underlying mechanisms of PANDAR in p53-mutant OC cisplatin-resistance.

METHODS

A2780 and A2780-DDP cells were served as OC cisplatin-sensitive and cisplatin-resistant cells. HO-8910PM cells were subjected to construct chemotherapy-induced extracellular vesicles (Chemo-EVs). Transmission electron microscopy (TEM) and nanoparticle tracking analysis were employed to evaluate Chemo-EVs. Cell viability was assessed using cell counting kit-8 and colony formation assays. Cell apoptosis was assessed using Annexin V and propidium iodide staining. The relationships between PANDAR, serine and arginine-rich pre-mRNA splicing factor 9 (SRSF9) were verified by RNA immunoprecipitation and fluorescence in situ hybridization. Tumor xenograft experiment was employed to evaluate the effects of PANDAR-Chemo-EVs on OC cisplatin-resistance in vivo. Immunofluorescent staining and immunohistochemistry were performed in tumor tissue.

RESULTS

PANDAR level increased in OC patients with p53-mutation. PANDAR efflux enacted via exosomes under cisplatin conditions. Additionally, exosomes from OC cell lines carried PANDAR, which significantly increased cell survival and chemoresistance in vitro and tumor progression and metastasis in vivo. During cisplatin-induced stress, SRSF9 was recruited to nuclear bodies by increased PANDAR and muted apoptosis in response to cisplatin. Besides, SRSF9 significantly increased the ratio of SIRT4/SIRT6 mRNA in OC.

CONCLUSION

Cisplatin-induced exosomes transfer PANDAR and lead to a rapid adaptation of OC cell survival through accumulating SRSF9 following cisplatin stress exposure.

The Role of NAD+, SIRTs Interactions in Stimulating and Counteracting Carcinogenesis

The World Health Organization has identified oncological diseases as one of the most serious health concerns of the current century. Current research on oncogenesis is focused on the molecular mechanisms of energy-biochemical reprogramming in cancer cell metabolism, including processes contributing to the Warburg effect and the pro-oncogenic and anti-oncogenic roles of sirtuins (SIRTs) and poly-(ADP-ribose) polymerases (PARPs). However, a clear understanding of the interaction between NAD⁺, SIRTs in cancer development, as well as their effects on carcinogenesis, has not been established, and literature data vary greatly. This work aims to provide a summary and structure of the available information on NAD⁺, SIRTs interactions in both stimulating and countering carcinogenesis, and to discuss potential approaches for pharmacological modulation of these interactions to achieve an anticancer effect.

MiR-363 suppresses the tumor growth of natural killer/T-cell lymphoma via the SIRT6/PI3K/AKT axis

Background

Natural killer/T cell lymphoma (NKTCL) is a rare and aggressive tumor of non-Hodgkin's lymphoma. The role of micro ribonucleic acid (RNA) (miR)-363 in NKTCL has not yet been elucidated. The present study aimed to investigate the potential role of miR-363 in NKTCL.

Methods

The expression of the top five differentially expressed microRNAs (miRNAs) as well as sirtuin 6 (SIRT6) in NK normal cells and its tumor cell lines were explored. The clinical tissues of NKTCL patients were collected and analyzed for expression of miR-363 and SIRT6. In addition, human NK/T-cell lymphoma cells (SNK-6) were transfected into different groups to detect cell proliferation and apoptosis abilities through cell counting kit 8 (CCK-8) experiment and flow cytometry analysis. Western blot assay was employed to examine protein expression. NKTCL nude mice models were constructed by subcutaneous injection of stably transfected SNK-6 cells to validate the mechanism of miR-363 in NKTCL via SIRT6 in vivo.

Results

MiR-363 was down-regulated in NKTCL tissues and cell lines. Overexpression of miR-363 inhibited cell proliferation and promoted cell apoptosis. In contrast, SIRT6 was up-regulated in NKTCL and proved to be a downstream target of miR-363. SIRT6 could activate the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. Also, miR-363 mimic could suppress the proliferation and induce the apoptosis of NKTCL via the SIRT6/PI3K/AKT axis both in vitro and in vivo.

Conclusions

MiR-363 suppresses the SIRT6/PI3K/AKT pathway to restrain cell proliferation and accelerate cell apoptosis during NKTCL progression.

Potential of histone deacetylase inhibitors for the therapy of ovarian cancer

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemotherapy increase patient mortality. Accumulating evidence demonstrates that histone modifications play a key role in cancerization and progression. Histone deacetylases is associated with chromatin condensed structure and transcriptional repression and play a role in chromatin remodeling and epigenetics. Histone deacetylases are promising targets for therapeutic interventions intended to reverse aberrant epigenetic associated with cancer. Therefore, histone deacetylases inhibitors could be used as anti-cancer drugs. Preclinical studies have shown promising outcomes of histone deacetylases inhibitors in ovarian cancer while clinical trials have had mixed results and limited success as monotherapy. Therefore, combination therapy with different anticancer drugs for synergistic effects and newly selective histone deacetylases inhibitors development for lower toxicity are hot issues now. In this review, we summarize the latest studies on the classification and mechanisms of action of histone deacetylase and the clinical application of their inhibitors as monotherapy or combination therapy in ovarian cancer.

The role of epigenetic modifications in Colorectal Cancer Metastasis

Distant metastasis is the major contributor to the high mortality rate of colorectal cancer (CRC). To overcome the poor prognosis caused by distant metastasis, the mechanisms of CRC metastasis should be further explored. Epigenetic events are the main mediators of gene regulation and further affect tumor progression. Recent studies have found that some epigenetic enzymes are often dysregulated or mutated in multiple tumor types, which prompted us to study the roles of these enzymes in CRC metastasis. In this review, we summarized the alteration of enzymes related to various modifications, including histone modification, nonhistone modification, DNA methylation, and RNA methylation, and their epigenetic mechanisms during the progression of CRC metastasis. Existing data suggest that targeting epigenetic enzymes is a promising strategy for the treatment of CRC metastasis.

ADP-Ribosylation as Post-Translational Modification of Proteins: Use of Inhibitors in Cancer Control

Among the post-translational modifications of proteins, ADP-ribosylation has been studied for over fifty years, and a large set of functions, including DNA repair, transcription, and cell signaling, have been assigned to this post-translational modification (PTM). This review presents an update on the function of a large set of enzyme writers, the readers that are recruited by the modified targets, and the erasers that reverse the modification to the original amino acid residue, removing the covalent bonds formed. In particular, the review provides details on the involvement of the enzymes performing monoADP-ribosylation/polyADP-ribosylation (MAR/PAR) cycling in cancers. Of note, there is potential for the application of the inhibitors developed for cancer also in the therapy of non-oncological diseases such as the protection against oxidative stress, the suppression of inflammatory responses, and the treatment of neurodegenerative diseases. This field of studies is not concluded, since novel enzymes are being discovered at a rapid pace.