Re-Sensitizing Tumor Cells to Cancer Drugs with Epigenetic Regulators

A New Class of Gold(I) NHC Complexes with Proapoptotic and Resensitizing Properties towards Multidrug Resistant Leukemia Cells Overexpressing BCL-2

From previous studies, it is evident that metal-organic gold(I) complexes have antiproliferative activities. The aim of this study is not only to find new anticancer agents but also to overcome existing cytostatic resistance in cancer cells. The synthesis and medicinal evaluation of two cationic 1,3-disubstituted gold(I) bis-tetrazolylidene complexes 1 and 2 are reported. To determine apoptosis-inducing properties of the complexes, DNA fragmentation was measured using propidium iodide staining followed by flow cytometry. Gold(I) complex 1 targets explicitly malignant cells, effectively inhibiting their growth and selectively inducing apoptosis without signs of necrosis. Even in cells resistant to common treatments such as doxorubicin, it overcomes multidrug resistance and sensitizes existing drug-resistant cells to common cytostatic drugs. It is assumed that gold(I) complex 1 involves the mitochondrial pathway in apoptosis and targets members of the BCL-2 family, enhancing its potential as a therapeutic agent in cancer treatment.

Targeting the chromatin structural changes of antitumor immunity

Epigenomic imbalance drives abnormal transcriptional processes, promoting the onset and progression of cancer. Although defective gene regulation generally affects carcinogenesis and tumor suppression networks, tumor immunogenicity and immune cells involved in antitumor responses may also be affected by epigenomic changes, which may have significant implications for the development and application of epigenetic therapy, cancer immunotherapy, and their combinations. Herein, we focus on the impact of epigenetic regulation on tumor immune cell function and the role of key abnormal epigenetic processes, DNA methylation, histone post-translational modification, and chromatin structure in tumor immunogenicity, and introduce these epigenetic research methods. We emphasize the value of small-molecule inhibitors of epigenetic modulators in enhancing antitumor immune responses and discuss the challenges of developing treatment plans that combine epigenetic therapy and immunotherapy through the complex interaction between cancer epigenetics and cancer immunology.

Inhibition of the CoREST Repressor Complex Promotes Wound Re-Epithelialization through the Regulation of Keratinocyte Migration

Wound healing is a complex process involving phases of hemostasis, inflammation, proliferation, and remodeling. The regenerative process in the skin requires coordination between many regulators, including signaling molecules, transcription factors, and the epigenetic machinery. In this study, we show that chromatin regulators HDAC1 and LSD1, key components of the CoREST repressor complex, are upregulated in the regenerating epidermis during wound repair. We also show that corin, a synthetic dual inhibitor of the CoREST complex and HDAC1/LSD1 activities, significantly accelerates wound closure through enhanced re-epithelialization in a mouse tail wound model. Acetylated H3K9 (methylation of histone H3 at lysine 9) expression, a histone modification targeted by HDAC1, is increased in keratinocytes after topical treatment with 100 nM and 1 μM of corin. In vitro experiments demonstrate that corin promotes migration and inhibits the proliferation of human keratinocytes. Furthermore, expression levels of genes promoting keratinocyte migration, such as AREG, CD24, EPHB2, ITGAX, PTGS, SCT1, SERPINB2, SERPINE1, SLPI, SNAI2, and TWIST, increased in keratinocytes treated with corin. These data demonstrate that dual inhibition of class I histone deacetylases and LSD1 by corin may serve as a new approach for promoting wound re-epithelialization and provide a platform for further applications of corin for the treatment of chronic wounds.

Drug Repositioning for Ovarian Cancer Treatment: An Update

Ovarian cancer (OC) is one of the most prevalent malignancies in female reproductive organs, and its 5-year survival is below 45%. Despite the advances in surgical and chemotherapeutic options, OC treatment is still a challenge, and new anticancer agents are urgently needed. Drug repositioning has gained significant attention in drug discovery, representing a smart way to identify new clinical applications for drugs whose human safety and pharmacokinetics have already been established, with great time and cost savings in pharmaceutical development endeavors. This review offers an update on the most promising drugs repurposable for OC treatment and/or prevention.

3-deazaneplanocin A, a histone methyltransferase inhibitor, improved the chemoresistance induced under hypoxia in melanoma cells

One of common characteristics of solid tumors is low O2 level, so-called hypoxia, which plays a critical role in chemoresistance. Epigenetic mechanism such as DNA methylation and histone modification is involved in cancer development and progression. There is ample evidence that epigenetic drugs reversed acquired chemoresistance in cancer cells under normal O2 level, normoxia. However, it remains unknown whether epigenetic drugs improve acquired chemoresistance under hypoxia. The aim of our study was to investigate whether epigenetic drugs can improve the chemoresistance induced under hypoxia in cancer cells. In murine melanoma B16-BL6 (B16) cells, the culture under hypoxia, 1%O2 caused the elevated expression of hypoxia-inducible factor-1α (HIF-1α) and its target genes. The chemoresistance to 7-ethyl-10-hydroxycamptothecin (SN-38, the active metabolite of irinotecan) was also acquired under hypoxia in B16 cells. In addition, as epigenetic mechanisms, the protein expression of the enhancer of zeste homolog 2 (EZH2), histone methyltransferase and its target histone H3 trimethylation at lysine 27 (H3K27Me3) level increased under hypoxia. The induction of H3K27Me3 under hypoxia was suppressed by EZH2 siRNA and 3-deazaneplanocin A (DZNep), an EZH2 inhibitor. Furthermore, both EZH2 siRNA and DZNep significantly reduced the cell viability after SN-38 treatment and improved the chemoresistance to SN-38 under hypoxia. These results indicated that the chemoresistance to SN-38 under hypoxia would arise from epigenetic mechanism, H3K27Me3 elevation due to EZH2 induction. In conclusion, a histone methyltransferase EZH2 inhibitor, DZNep was capable of tackling acquired chemoresistance via the suppression of histone methylation induced under hypoxic tumor microenvironment.

The Advances in Epigenetics for Cancer Radiotherapy

Cancer is an important factor threatening human life and health; in recent years, its morbidity and mortality remain high and demosntrate an upward trend. It is of great significance to study its pathogenesis and targeted therapy. As the complex mechanisms of epigenetic modification has been increasingly discovered, they are more closely related to the occurrence and development of cancer. As a reversible response, epigenetic modification is of great significance for the improvement of classical therapeutic measures and the discovery of new therapeutic targets. It has become a research focusto explore the multi-level mechanisms of RNA, DNA, chromatin and proteins. As an important means of cancer treatment, radiotherapy has made great progress in technology, methods, means and targeted sensitization after years of rapid development, and even research on radiotherapy based on epigenetic modification is rampant. A series of epigenetic effects of radiation on DNA methylation, histone modification, chromosome remodeling, RNA modification and non-coding RNA during radiotherapy affects the therapeutic effects and prognosis. Starting from the epigenetic mechanism of tumorigenesis, this paper reviews the latest progress in the mechanism of interaction between epigenetic modification and cancer radiotherapy and briefly introduces the main types, mechanisms and applications of epigenetic modifiers used for radiotherapy sensitization in order to explore a more individual and dynamic approach of cancer treatment based on epigenetic mechanism. This study strives to make a modest contribution to the progress of human disease research.

Multi-CpG linear regression models to accurately predict paclitaxel and docetaxel activity in cancer cell lines

The microtubule-targeting paclitaxel (PTX) and docetaxel (DTX) are widely used chemotherapeutic agents. However, the dysregulation of apoptotic processes, microtubule-binding proteins, and multi-drug resistance efflux and influx proteins can alter the efficacy of taxane drugs. In this review, we have created multi-CpG linear regression models to predict the activities of PTX and DTX drugs through the integration of publicly available pharmacological and genome-wide molecular profiling datasets generated using hundreds of cancer cell lines of diverse tissue of origin. Our findings indicate that linear regression models based on CpG methylation levels can predict PTX and DTX activities (log-fold change in viability relative to DMSO) with high precision. For example, a 287-CpG model predicts PTX activity at R² of 0.985 among 399 cell lines. Just as precise (R²=0.996) is a 342-CpG model for predicting DTX activity in 390 cell lines. However, our predictive models, which employ a combination of mRNA expression and mutation as input variables, are less accurate compared to the CpG-based models. While a 290 mRNA/mutation model was able to predict PTX activity with R² of 0.830 (for 546 cell lines), a 236 mRNA/mutation model could calculate DTX activity at R² of 0.751 (for 531 cell lines). The CpG-based models restricted to lung cancer cell lines were also highly predictive (R²≥0.980) for PTX (74 CpGs, 88 cell lines) and DTX (58 CpGs, 83 cell lines). The underlying molecular biology behind taxane activity/resistance is evident in these models. Indeed, many of the genes represented in PTX or DTX CpG-based models have functionalities related to apoptosis (e.g., ACIN1, TP73, TNFRSF10B, DNASE1, DFFB, CREB1, BNIP3), and mitosis/microtubules (e.g., MAD1L1, ANAPC2, EML4, PARP3, CCT6A, JAKMIP1). Also represented are genes involved in epigenetic regulation (HDAC4, DNMT3B, and histone demethylases KDM4B, KDM4C, KDM2B, and KDM7A), and those that have never been previously linked to taxane activity (DIP2C, PTPRN2, TTC23, SHANK2). In summary, it is possible to accurately predict taxane activity in cell lines based entirely on methylation at multiple CpG sites.

m6A Methyltransferase METTL14-Mediated Upregulation of Cytidine Deaminase Promoting Gemcitabine Resistance in Pancreatic Cancer

Objective

Pancreatic cancer is one of the most lethal human malignancies. Gemcitabine is widely used to treat pancreatic cancer, and the resistance to chemotherapy is the major difficulty in treating the disease. N⁶-methyladenosine (m⁶A) modification, which regulates RNA splicing, stability, translocation, and translation, plays critical roles in cancer physiological and pathological processes. METTL14, an m6A Lmethyltransferase, was found deregulated in multiple cancer types. However, its role in gemcitabine resistance in pancreatic cancer remains elusive.

Methods

The mRNA and protein level of m⁶A modification associated genes were assessed by QRT-PCR and western blotting. Then, gemcitabine‐resistant pancreatic cancer cells were established. The growth of pancreatic cancer cells were analyzed using CCK8 assay and colony formation assay. METTL14 was depleted by using shRNA. The binding of p65 on METTL14 promoter was assessed by chromatin immunoprecipitation (ChIP) assay. Protein level of deoxycytidine kinase (DCK) and cytidine deaminase (CDA) was evaluated by western blotting. In vivo experiments were conducted to further confirm the critical role of METTL14 in gemcitabine resistance.

Results

We found that gemcitabine treatment significantly increased the expression of m⁶A methyltransferase METTL14, and METTL14 was up-regulated in gemcitabine-resistance human pancreatic cancer cells. Suppression of METTL14 obviously increased the sensitivity of gemcitabine in resistant cells. Moreover, we identified that transcriptional factor p65 targeted the promoter region of METTL14 and up-regulated its expression, which then increased the expression of cytidine deaminase (CDA), an enzyme inactivates gemcitabine. Furthermore, in vivo experiment showed that depletion of METTL14 rescue the response of resistance cell to gemcitabine in a xenograft model.

Conclusion

Our study suggested that METTL14 is a potential target for chemotherapy resistance in pancreatic cancer.