Inhibition of EZH2 enhances the therapeutic effect of 5-FU via PUMA upregulation in colorectal cancer

Nucleoside-based anticancer drugs: Mechanism of action and drug resistance

Nucleoside-based drugs, recognized as purine or pyrimidine analogs, have been potent therapeutic agents since their introduction in 1950, deployed widely in the treatment of diverse diseases such as cancers, myelodysplastic syndromes, multiple sclerosis, and viral infections. These antimetabolites establish complex interactions with cellular molecular constituents, primarily via activation of phosphorylation cascades leading to consequential interactions with nucleic acids. However, the therapeutic efficacy of these agents is frequently compromised by the development of drug resistance, a continually emerging challenge in their clinical application. This comprehensive review explores the mechanisms of resistance to nucleoside-based drugs, encompassing a wide spectrum of phenomena from alterations in membrane transporters and activating kinases to changes in drug elimination strategies and DNA damage repair mechanisms. The critical analysis in this review underlines complex interactions of drug and cell and also guides towards novel therapeutic strategies to counteract resistance. The development of targeted therapies, novel nucleoside analogs, and synergistic drug combinations are promising approaches to restore tumor sensitivity and improve patient outcomes.

Long noncoding RNA SNHG6 silencing sensitized esophageal cancer cells to 5-FU via EZH2/STAT pathway

Chemotherapy was the main treatment method for esophageal cancer (EC) patients. However, chemotherapy resistance due to multiple factors is a major barrier to EC treatment. For investigating how small nucleolar RNA host gene 6 (SNHG6) affected the 5-fluorouracil (5-FU) resistance in EC as well as its possible molecular mechanism. This work conducted cell viability assay, clone formation, scratch assays together with cell apoptosis for evaluating the roles of SNHG6 and enhancer of zeste homolog 2 (EZH2, the histone-lysine N-methyltransferase). Relevant molecular mechanism was identified by RT-qPCR analysis together with Western-blot (WB) assays. Our data showed that SNHG6 expression increased in EC cells. SNHG6 promotes colony formation and migration, whereas suppresses EC cell apoptosis. SNHG6 silencing markedly promoted 5-FU-mediated suppression on KYSE150 and KYSE450 cells. Additional mechanism studies showed that SNHG6 modulating STAT3 and H3K27me3 via promoting EZH2 level. Similar to the function of SNHG6, abnormal expression of EZH2 promotes the malignancy of EC and intensifies its resistance to 5-FU. In addition, overexpression of EZH2 abolished the role of SNHG6 silencing in 5-FU sensitivity in EC cells. SNHG6 overexpression promoted malignancy of EC and increased EC cell resistance to 5-FU. Besides, further molecular mechanism studies provided a novel regulatory pathways that SNHG6 knockdown promoted EC cell sensitivity to 5-FU by modulating STAT3 and H3K27me3 via promoting EZH2 expression.

Evaluation of Tazemetostat as a Therapeutically Relevant Substance in Biliary Tract Cancer

Biliary tract cancer (BTC) is a gastrointestinal malignancy associated with a poor survival rate. Current therapies encompass palliative and chemotherapeutic treatment as well as radiation therapy, which results in a median survival of only one year due to standard therapeutic ineffectiveness or resistance. Tazemetostat is an FDA-approved inhibitor of enhancer of Zeste homolog 2 (EZH2), a methyltransferase involved in BTC tumorigenesis via trimethylation of histone 3 at lysine 27 (H3K27me3), an epigenetic mark associated with silencing of tumor suppressor genes. Up to now, there are no data available regarding tazemetostat as a possible treatment option against BTC. Therefore, the aim of our study is a first-time investigation of tazemetostat as a potential anti-BTC substance in vitro. In this study, we demonstrate that tazemetostat affects cell viability and the clonogenic growth of BTC cells in a cell line-dependent manner. Furthermore, we found a strong epigenetic effect at low concentrations of tazemetostat, which was independent of the cytotoxic effect. We also observed in one BTC cell line that tazemetostat increases the mRNA levels and protein expression of the tumor suppressor gene Fructose-1,6-bisphosphatase 1 (FBP1). Interestingly, the observed cytotoxic and epigenetic effects were independent of the mutation status of EZH2. To conclude, our study shows that tazemetostat is a potential anti-tumorigenic substance in BTC with a strong epigenetic effect.

Novel insights into histone lysine methyltransferases in cancer therapy: From epigenetic regulation to selective drugs

The reversible and precise temporal and spatial regulation of histone lysine methyltransferases (KMTs) is essential for epigenome homeostasis. The dysregulation of KMTs is associated with tumor initiation, metastasis, chemoresistance, invasiveness, and the immune microenvironment. Therapeutically, their promising effects are being evaluated in diversified preclinical and clinical trials, demonstrating encouraging outcomes in multiple malignancies. In this review, we have updated recent understandings of KMTs' functions and the development of their targeted inhibitors. First, we provide an updated overview of the regulatory roles of several KMT activities in oncogenesis, tumor suppression, and immune regulation. In addition, we summarize the current targeting strategies in different cancer types and multiple ongoing clinical trials of combination therapies with KMT inhibitors. In summary, we endeavor to depict the regulation of KMT-mediated epigenetic landscape and provide potential epigenetic targets in the treatment of cancers.

SFMBT1 facilitates colon cancer cell metastasis and drug resistance combined with HMG20A

In colorectal cancer (CRC), the development of reagents that increase sensitivity to chemotherapeutic agents could prevent drug resistance and improve patient survival. Scm-like with four malignant brain tumor domains 1 (SFMBT1) is up-regulated in CRC tumor tissues and cells and may be associated with drug resistance. We detected the expression of SFMBT1 in CRC tissue microarrays by immunohistochemistry. The role of SFMBT1 in the migration, proliferation and invasion of CRC or resistance to 5-fluorouracil (5-FU) was determined using scratch assay, colony formation and Transwell assay. Fluorescence co-localization and immunoprecipitation were used to analyze the correlation between SFMBT1 and high mobility group domain-containing protein 20 A (HMG20A). Xenograft experiments were conducted to investigate the role of SFMBT1 and HMG20A in tumor growth and metastasis in vivo. We found that SFMBT1 is up-regulated in CRC and its expression is further amplified in 5-FU resistance. SFMBT1 drives 5-FU resistance and CRC proliferation, migration and invasion. Correlation analysis shows that SFMBT1 and HMG20A are positively correlated. Mechanistically, fluorescence co-localization and immunoprecipitation assay indicate an interaction between SFMBT1 and HMG20A. Depletion of SFMBT1 down-regulates HMG20A downstream. These results were verified by murine xenograft and lung metastasis models. Our results indicate that the SFMBT1/HMG20A axis could be targeted to increase the resistance of CRC cells to 5-FU.

The paradigm of drug resistance in cancer: an epigenetic perspective

Innate and acquired resistance towards the conventional therapeutic regimen imposes a significant challenge for the successful management of cancer for decades. In patients with advanced carcinomas, acquisition of drug resistance often leads to tumor recurrence and poor prognosis after the first therapeutic cycle. In this context, cancer stem cells (CSCs) are considered as the prime drivers of therapy resistance in cancer due to their 'non-targetable' nature. Drug resistance in cancer is immensely influenced by different properties of CSCs such as epithelial-to-mesenchymal transition (EMT), a profound expression of drug efflux pump genes, detoxification genes, quiescence, and evasion of apoptosis, has been highlighted in this review article. The crucial epigenetic alterations that are intricately associated with regulating different mechanisms of drug resistance, have been discussed thoroughly. Additionally, special attention is drawn towards the epigenetic mechanisms behind the interaction between the cancer cells and their microenvironment which assists in tumor progression and therapy resistance. Finally, we have provided a cumulative overview of the alternative treatment strategies and epigenome-modifying therapies that show the potential of sensitizing the resistant cells towards the conventional treatment strategies. Thus, this review summarizes the epigenetic and molecular background behind therapy resistance, the prime hindrance of present day anti-cancer therapies, and provides an account of the novel complementary epi-drug-based therapeutic strategies to combat drug resistance.

Preclinical and clinical aspects of using Tazemetostate in human cancers

Abstract:

Epigenetic drugs are novel drug categories with promising effects in different cancers. Tazemetostate is among the drugs that were recently used in clinical settings, especially in the treatment of specific tumors and lymphomas. There are a growing number of ongoing clinical trials evaluating the safety and efficacy of tazemetostate in different cancers. The present review addressed the available preclinical studies evaluating the combination of tazemetostate and other chemotherapy agents in treating different cancers and summarized the limited clinical evidence available regarding the efficacy of this novel Enhancer of Zeste Homolog 2 (EZH2) inhibitor in cancer. Based on the available clinical studies, tazemetostate could be considered a safe epigenetic agent with limited adverse events for treating specific types of lymphomas and solid tumors. However, the superiority of using tazemetostate over other chemotherapy agents in patients with cancer as well as using the drug for other clinical conditions including non-alcoholic steatohepatitis needs further investigation. Moreover, the effect of tazemetostate on human germline cells is clearly evaluated as some animal studies demonstrated that the drug can affect germline epigenome suggesting further studies on this issue.

Identification of autophagy related genes in predicting the prognosis and aiding 5- fluorouracil therapy of colorectal cancer

The emergence of 5-Fluorouracil (5-FU) resistance is the barrier to effective clinical outcomes for colorectal cancer (CRC) patients. Autophagy was found to be involved in protecting tumor cells from 5-FU. However, the specific role of autophagy-related genes in CRC 5-FU resistance remains unclear. In this study, HSPB8 among 34 differentially expressed ARGs in CRC was identified to be the hub ARGs in 5-FU resistant which was down-regulated in CRC samples when compared with normal samples but up-regulated in CRC samples with relatively higher lymphatic invasion, later stages and poor prognosis of CRC. Mechanistic analysis demonstrated that due to the recruitment of CAFs, HSPB8 expression was enhanced in CRC cells so that HSPB8 could act together with its co-chaperone BAG3 in autophagy drived 5-FU resistance. Furthermore, the augmented expression level of HSPB8 was found to be significantly correlated to the immune cell infiltration such as Treg cells, macrophages, monocyte and dendritic cells and so on. Our results suggested CAFs driving HSPB8 induced CRC 5-FU resistance by promoting tumor autophagy would provide a new strategy in seeking potential CRC therapeutic target.

MY11 exerts antitumor effects through activation of the NF-κB/PUMA signaling pathway in breast cancer

Breast cancer is the most common malignancy in women worldwide, and the discovery of new effective breast cancer therapies with lower toxicity is still needed. We screened a series of chalcone derivatives and found that MY11 ((E)-1-(2-hydroxy-4,6-dimethoxyphenyl)-3-(4-piperazinylphenyl) prop-2-en-1-one) had the strongest anti-breast cancer activity. MY11 inhibited the growth of MDA-MB-231 and MCF-7 breast cancer cells by arresting the cell cycle and promoting apoptosis, through regulation of the cell cycle and apoptosis-related proteins. PDTC (Pyrrolidinedithiocarbamate ammonium), a specific inhibitor of the NF-κB pathway, abolished the inhibitory effect of MY11 treatment. NF-κB has been shown to regulate PUMA-dependent apoptosis. Our in vitro studies demonstrated that MY11 promoted breast cancer cell apoptosis by activating the NF-κB/PUMA/mitochondrial apoptosis pathway (including Bcl-2, Bax, and Caspase-9). MY11 also inhibited tumor growth in an orthotopic breast cancer mouse model by inducing apoptosis through the NF-κB signaling pathway, importantly, with minimal toxicity. In addition, MY11 was found by docking analysis to bind to p65, which might enhance the stability of the p65 protein. Taken together, our findings indicate that MY11 exerts a significant anticancer effect in breast cancer and that it may be a potential candidate for the treatment of breast cancer.

RFWD3 Participates in the Occurrence and Development of Colorectal Cancer via E2F1 Transcriptional Regulation of BIRC5

Objectives: Colorectal cancer (CRC) is one of the most common human malignancies. It was reported that the alterations in the DNA damage response (DDR) pathways are emerging as novel targets for treatment across different cancer types including CRC. RFWD3 plays a critical role in replication protein A (RPA)-mediated DNA damage in cancer cells. More importantly, RFWD3 can response to DNA damage by positively regulating p53 stability when the G1 cell cycle checkpoint is activated. However, the functional significance of RFWD3 in CRC has not been reported in the existing documents.

Materials and Methods: Here, we revealed high expression of RFWD3 in CRC tissues by IHC analysis and The Cancer Genome Atlas (TCGA) database. Besides, overexpression of RFWD3 in CRC cell lines was also confirmed by qRT-PCR and western blot assay. The Celigo cell counting method and wound-healing/transwell migration assay were applied to evaluate CRC cell proliferation and migration. The tumor growth indicators were quantified in nude mice xenografted with shRFWD3 and shCtrl RKO cells.

Results: The results indicated that RFWD3 knockdown restricted CRC development in vitro and in vivo. In exploring the downstream mechanism of RFWD3’s action, we found that RFWD3 could transcriptionally activate BIRC5 by interacting with E2F transcription factor 1 (E2F1). Accordingly, we identified BIRC5 as a downstream gene of RFWD3 regulating CRC. Subsequent loss- and gain- of function experiments demonstrated that upon overexpressing BIRC5 in RKO cells with down-regulated RFWD3, the inhibitory effects of cell proliferation, migration and colony formation could be reversed, while the capacity of cell apoptosis was ameliorated, suggesting that the effects of RFWD3 depletion was mainly due to BIRC5 suppression.

Conclusion: Taken together, this study revealed that RFWD3 participates in the occurrence and development of colorectal cancer via E2F1 transcriptional regulation of BIRC5.

Tumor-suppressive function of EZH2 is through inhibiting glutaminase

Tumors can use metabolic reprogramming to survive nutrient stress. Epigenetic regulators play a critical role in metabolic adaptation. Here we screened a sgRNA library to identify epigenetic regulators responsible for the vulnerability of colorectal cancer (CRC) cells to glucose deprivation and found that more EZH2-knockout cells survived glucose deprivation. Then, we showed that EZH2 expression was significantly downregulated in response to glucose deprivation in a glucose-sensitive CRC cell line, and EZH2-knockdown cells were more resistant to glucose deprivation. Mechanistically, EZH2 deficiency upregulated the expression of glutaminase (GLS) and promoted the production of glutamate, which in turn led to increased synthesis of intracellular glutathione (GSH) and eventually attenuated the reactive oxygen species (ROS)-mediated cell death induced by glucose deprivation. Although EZH2 functioned as an oncogene in cancer progression and EZH2 knockout abolished colorectal cancer development in a mouse model, here we revealed a mechanistic link between EZH2 and metabolic reprogramming via the direct regulation of GLS expression and observed a negative correlation between EZH2 and GLS expression in colorectal cancer tissues. These findings further confirmed the importance of heterogeneity, provided an explanation for the clinical tolerance of cancer cells to EZH2 inhibitors from the perspective of metabolism, and proposed the possibility of combining EZH2 inhibitors and glutamine metabolism inhibitors for the treatment of cancer.

BRD9 inhibition promotes PUMA-dependent apoptosis and augments the effect of imatinib in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are primarily characterized by activating mutations of tyrosine kinase or platelet-derived growth factor receptor alpha. Although the revolutionary therapeutic outcomes of imatinib are well known, the long-term benefits of imatinib are still unclear. The effects of BRD9, a recently identified subunit of noncanonical BAF complex (ncBAF) chromatin remodeling complexes, in GISTs are not clear. In the current study, we evaluated the functional role of BRD9 in GIST progression. Our findings demonstrated that the expression of BRD9 was upregulated in GIST tissues. The downregulation or inhibition of BRD9 could significantly reduce cellular proliferation, and facilitates apoptosis in GISTs. BRD9 inhibition could promote PUMA-dependent apoptosis in GISTs and enhance imatinib activity in vitro and in vivo. BRD9 inhibition synergizes with imatinib in GISTs by inducing PUMA upregulation. Mechanism study revealed that BRD9 inhibition promotes PUMA induction via the TUFT1/AKT/GSK-3β/p65 axis. Furthermore, imatinib also upregulates PUMA by targeting AKT/GSK-3β/p65 axis. In conclusion, our results indicated that BRD9 plays a key role in the progression of GISTs. Inhibition of BRD9 is a novel therapeutic strategy in GISTs treated alone or in combination with imatinib.

TMT-Based Quantitative Proteomic Analysis Identified Proteins and Signaling Pathways Involved in the Response to Xanthatin Treatment in Human HT-29 Colon Cancer Cells

BACKGROUND

Xanthatin is a plant-derived bioactive sesquiterpene lactone from the Xanthium strumarium L., and it has been used as a traditional Chinese medicine. Recently, many studies have reported that xanthatin has anticancer activity. However, a comprehensive understanding of the mechanism underlying the antitumor effects of xanthatin is still lacking.

OBJECTIVE

To systematically and comprehensively identify the underlying mechanisms of xanthatin on cancer cells, quantitative proteomic techniques were performed.

METHODS

Xanthatin induced HT-29 colon cancer cells death was detected by lactate dehydrogenase (LDH) release cell death assay. Differentially abundant proteins in two groups (control groups and xanthatin treatment groups) of human HT-29 colon cancer cells were identified using tandem mass tag (TMT) quantitative proteomic techniques. All the significant differentially abundant proteins were generally characterized by performing hierarchical clustering, Gene Ontology (GO) enrichment analyses and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. We chose Western blot analysis to validate the candidate proteins in the proteomics results.

RESULTS

A total of 5637 proteins were identified, of which 397 significantly differentially abundant proteins in the groups were quantified. Based on the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses, we found that p53-related signaling played an important role in xanthatin-treated HT-29 colon cancer cells. p53-upregulated modulator of apoptosis (Puma), Sestrin-2 and p14ARF, which were selected from among p53-related signaling proteins, were further validated, and the results were consistent with the tandem mass tag quantitative proteomic results.

CONCLUSION

We first investigated the molecular mechanism underlying the effects of xanthatin treatment on HT-29 colon cancer cells using tandem mass tag quantitative proteomic methods and provided a global comprehensive understanding of the antitumor effects of xanthatin. However, it is necessary to further confirm the function of the differentially abundant proteins and the potentially associated signaling pathways.

Long noncoding RNA DLGAP1-AS1 promotes the progression of glioma by regulating the miR-1297/EZH2 axis

Dysregulated lncRNAs have been implicated in a plethora of tumors, including glioma. One such oncogenic lncRNAs that has been reported in several cancers is the lncRNA DLGAP1 antisense RNA 1 (DLGAP1-AS1). This study seeks to characterize the expression of DLGAP1-AS1 in glioma tissues, which we found to be raised in both glioma samples and cell lines. Functional experiments revealed that DLGAP1-AS1 promoted in vitro glioma cell invasion, migration and proliferation. DLGAP1-AS1 was found to function as a miR-1297 sponge, based on information from luciferase reporter assays, RNA pull-down assays and publicly available online databases. miR-1297 was in turn found to functionally target EZH2. DLGAP1-AS1 modulated EZH2 expressions through miR-1297 sponging. Glioma progression appears to be supported DLGAP1-AS1 -promoted activation of the miR-1297/EZH2 axis. The components of this axis may function as therapeutic targets for glioma.

The Role of Epigenetics in the Progression of Clear Cell Renal Cell Carcinoma and the Basis for Future Epigenetic Treatments

Simple Summary

The accumulated evidence on the role of epigenetic markers of prognosis in clear cell renal cell carcinoma (ccRCC) is reviewed, as well as state of the art on epigenetic treatments for this malignancy. Several epigenetic markers are likely candidates for clinical use, but still have not passed the test of prospective validation. Development of epigenetic therapies, either alone or in combination with tyrosine-kinase inhibitors of immune-checkpoint inhibitors, are still in their infancy.

Abstract

Clear cell renal cell carcinoma (ccRCC) is curable when diagnosed at an early stage, but when disease is non-confined it is the urologic cancer with worst prognosis. Antiangiogenic treatment and immune checkpoint inhibition therapy constitute a very promising combined therapy for advanced and metastatic disease. Many exploratory studies have identified epigenetic markers based on DNA methylation, histone modification, and ncRNA expression that epigenetically regulate gene expression in ccRCC. Additionally, epigenetic modifiers genes have been proposed as promising biomarkers for ccRCC. We review and discuss the current understanding of how epigenetic changes determine the main molecular pathways of ccRCC initiation and progression, and also its clinical implications. Despite the extensive research performed, candidate epigenetic biomarkers are not used in clinical practice for several reasons. However, the accumulated body of evidence of developing epigenetically-based biomarkers will likely allow the identification of ccRCC at a higher risk of progression. That will facilitate the establishment of firmer therapeutic decisions in a changing landscape and also monitor active surveillance in the aging population. What is more, a better knowledge of the activities of chromatin modifiers may serve to develop new therapeutic opportunities. Interesting clinical trials on epigenetic treatments for ccRCC associated with well established antiangiogenic treatments and immune checkpoint inhibitors are revisited.