Blocking histone methyltransferase SETDB1 inhibits tumorigenesis and enhances cetuximab sensitivity in colorectal cancer

CRISPR/Cas9-directed epigenetic editing in colorectal cancer

Colorectal cancer (CRC) remains a leading cause of cancer-related illness and death worldwide, arising from a complex interplay of genetic predisposition, environmental influences, and epigenetic dysregulation. Among these factors, epigenetic modifications-reversible and heritable changes in gene expression-serve as crucial regulators of CRC progression. Understanding these modifications is essential for identifying potential biomarkers for early diagnosis and developing targeted therapeutic strategies. Epigenetic drugs (epidrugs) such as DNA methyltransferase inhibitors (e.g., decitabine) and bromodomain inhibitors (e.g., JQ1) have shown promise in modulating aberrant epigenetic changes in CRC. However, challenges such as drug specificity, delivery, and safety concerns limit their clinical application. Advances in CRISPR-Cas9-based epigenetic editing offer a more precise approach to modifying specific epigenetic markers, presenting a potential breakthrough in CRC treatment. Despite its promise, CRISPR-based epigenome editing may result in unintended genetic modifications, necessitating stringent regulations and safety assessments. Beyond pharmacological interventions, lifestyle factors-including diet and gut microbiome composition-play a significant role in shaping the epigenetic landscape of CRC. Nutritional and microbiome-based interventions have shown potential in preventing CRC development by maintaining intestinal homeostasis and reducing tumor-promoting epigenetic changes. This review provides a comprehensive overview of epigenetic alterations in CRC, exploring their implications for diagnosis, prevention, and treatment. By integrating multi-omics approaches, single-cell technologies, and model organism studies, future research can enhance the specificity and efficacy of epigenetic-based therapies. Shortly, a combination of advanced gene-editing technologies, targeted epidrugs, and lifestyle interventions may pave the way for more effective and personalized CRC treatment strategies.

The HIF2α-dependent upregulation of SETDB1 facilitates hypoxia-induced functional and phenotypical changes of pulmonary microvascular endothelial cells

Emerging studies have reported the vital role of histone modification in the dysfunction of pulmonary vascular endothelial cells, which acts as the key reason to drive the hypoxia-induced pulmonary vascular remodeling and pulmonary hypertension (PH). This study aims to investigate the role of a histone 3 lysine 9 (H3K9) methyltransferase, SET domain bifurcated 1 (SETDB1), in hypoxia-induced functional and phenotypical changes of pulmonary vascular endothelial cells. Primarily cultured rat pulmonary microvascular endothelial cells (PMVECs) were used as cell model. Specific knockdown and overexpression strategies were used to systematically determine the molecular regulation and function of SETDB1 in PMVECs. SETDB1 is highly expressed and significantly upregulated in the pulmonary vascular endothelium of lung tissue isolated from SU5416/hypoxia-induced PH (SuHx-PH) rats and also in pulmonary arterial endothelial cells (PAECs) from patients with idiopathic pulmonary arterial hypertension (IPAH), comparing with their respective controls. In primarily cultured rat PMVECs, treatment of hypoxia or CoCl2 induces significant upregulation of HIF2α, SETDB1, and H3K9me3. Specific knockdown and overexpression strategies indicate that the hypoxia- or CoCl2-induced upregulation of SETDB1 is mediated through a HIF2α-dependent mechanism. Knockdown of SETDB1 significantly inhibits the hypoxia- or CoCl2-induced apoptosis, senescence, and endothelial to mesenchymal transition (EndoMT) in rat PMVECs. Moreover, treatment of the specific inhibitor of histone methyltransferase, Chaetocin, effectively attenuates the disease pathogenesis of SuHx-PH in rat. Our results suggest that the HIF2α-dependent upregulation of SETDB1 facilitates hypoxia-induced functional and phenotypical changes of PMVECs, potentially contributing to the hypoxia-induced pulmonary vascular remodeling and PH.NEW & NOTEWORTHY Abnormal histone modification plays vital role in pulmonary hypertension (PH). This study reports the regulation and role of a histone 3 lysine 9 (H3K9) methyltransferase, SETDB1, in primarily cultured rat pulmonary microvascular endothelial cells (PMVECs). Hypoxia induces significant upregulation of SETDB1 at both mRNA and protein levels, in a HIF2α-dependent manner. The hypoxic upregulation of SETDB1 leads to significant apoptosis, senescence, and endothelial-to-mesenchymal transition in PMVECs. Treatment of a specific inhibitor of histone methyltransferase, Chaetocin, effectively attenuates the disease pathogenesis of PH rat model induced by SU5416/hypoxia.

Therapeutic targeting potential of the protein lysine and arginine methyltransferases to reverse cancer chemoresistance

Cancer treatments have continued to improve tremendously over the past decade, but therapy resistance is still a common, major factor encountered by patients diagnosed with cancer. Chemoresistance arises due to various circumstances and among these causes, increasing evidence has shown that enzymes referred to as protein methyltransferases (PMTs) play a significant role in the development of chemoresistance in various cancers. These enzymes are responsible for the methylation of different amino acids, particularly lysine and arginine, via protein lysine methyltransferases (PKMTs) and protein arginine methyltransferases (PRMTs), respectively. Various PMTs have been identified to be dysregulated in the development of cancer and chemoresistance. Nonetheless, the functional role of these PMTs in the development of chemoresistance is poorly characterised. This advocates the need for innovative approaches and technologies suitable for better characterisation of these PMTs and their potential clinical inhibitors. In the case of a handful of PMTs, inhibitory small molecules which can function as anticancer drugs have been developed and have also entered clinical trials. Considering all this, PMTs have become a promising and valuable target in cancer chemoresistance related research. This review will give a small introduction on the different PKMTs and PRMTs families which are dysregulated in different cancers and the known proteins targeted by the respective enzymes. The focus will then shift towards PMTs known to be involved in chemoresistance development and the inhibitors developed against these, together with their mode of action. Lastly, the current obstacles and future perspectives of PMT inhibitors in cancer chemoresistance will be discussed.

The function of histone methyltransferase SETDB1 and its roles in liver cancer

Epigenetic alterations in gene expression have been implicated in cancer development and tumor immune escape, with posttranslational histone or non-histone modifications representing attractive targets for disease surveillance and therapy. SET domain bifurcated 1 (SETDB1) is a histone lysine methyltransferase that reversibly catalyzes the di- and tri-methylation of histone 3 lysine 9 (H3K9) on euchromatin, inhibiting gene transcription within these regions and facilitating the switch from euchromatic to heterochromatic states. Emerging evidence suggests that SETDB1 amplification and aberrant activation are significantly associated with poor prognosis in hepatocellular carcinoma (HCC), and contribute to HCC development, immune escape, and immune checkpoint blockade (ICB) resistance. Here, we provide an updated overview of the cellular and molecular effects of SETDB1 activity in hepatocarcinogenesis and progression and focus on studies linking its function to immunotherapy for HCC, and present current challenges and future perspectives for targeting SETDB1 in HCC treatment.

SETDB1 as a cancer target: challenges and perspectives in drug design

Genome stability is governed by chromatin structural dynamics, which modify DNA accessibility under the influence of intra- and inter-nucleosomal contacts, histone post-translational modifications (PTMs) and variations, besides the activity of ATP-dependent chromatin remodelers. These are the main ways by which chromatin dynamics are regulated and connected to nuclear processes, which when dysregulated can frequently be associated with most malignancies. Recently, functional crosstalk between histone modifications and chromatin remodeling has emerged as a critical regulatory method of transcriptional regulation during cell destiny choice. Therefore, improving therapeutic outcomes for patients by focusing on epigenetic targets dysregulated in malignancies should help prevent cancer cells from developing resistance to anticancer treatments. For this reason, SET domain bifurcated histone lysine methyltransferase 1 (SETDB1) has gained a lot of attention recently as a cancer target. SETDB1 is a histone lysine methyltransferase that plays an important role in marking euchromatic and heterochromatic regions. Hence, it promotes the silencing of tumor suppressor genes and contributes to carcinogenesis. Some studies revealed that SETDB1 was overexpressed in various human cancer types, which enhanced tumor growth and metastasis. Thus, SETDB1 appears to be an attractive epigenetic target for new cancer treatments. In this review, we have discussed the effects of its overexpression on the progression of tumors and the development of inhibitor drugs that specifically target this enzyme.

SETDB1, an H3K9-specific methyltransferase: An attractive epigenetic target to combat cancer

SET domain bifurcated histone lysine methyltransferase 1 (SETDB1) is an important epigenetic regulator catalyzing histone H3 lysine 9 (H3K9) methylation, specifically di-/tri-methylation. This regulation promotes gene silencing through heterochromatin formation. Aberrant SETDB1 expression, and its oncogenic role is evident in many cancers. Thus, SETDB1 is a valid target with novel therapeutic benefits. In this review, we explore the structural and biochemical features of SETDB1, its regulatory mechanisms, and its role in various cancers. We also discuss recent discoveries in small molecules targeting SETDB1 and provide suggestions for future research.

SETDB1: Progress and prospects in cancer treatment potential and inhibitor research

SET domain bifurcated methyltransferase 1 (SETDB1) serves as a histone lysine methyltransferase, catalyzing the di- and tri-methylation of histone H3K9. Mounting evidence indicates that the abnormal expression or activity of SETDB1, either through amplification or mutation, plays a crucial role in tumorigenesis and progression. This is particularly evident in the context of tumor immune evasion and resistance to immune checkpoint blockade therapy. Furthermore, there is a robust association between SETDB1 dysregulation and an unfavorable prognosis across various types of tumors. The oncogenic role of SETDB1 primarily arises from its methyltransferase function, which contributes to the establishment of a condensed and transcriptionally inactive heterochromatin state. This results in the inactivation of genes that typically hinder cancer development and silencing of retrotransposons that could potentially trigger an immune response. These findings underscore the substantial potential for SETDB1 as an anti-tumor therapeutic target. Nevertheless, despite significant strides in recent years in tumor biology research, challenges persist in SETDB1-targeted therapy. To better facilitate the development of anti-tumor therapy targeting SETDB1, we have conducted a comprehensive review of SETDB1 in this account. We present the structure and function of SETDB1, its role in various tumors and immune regulation, as well as the advancements made in SETDB1 antagonists. Furthermore, we discuss the challenges encountered and provide perspectives for the development of SETDB1-targeted anti-tumor therapy.

SETDB1 promotes progression through upregulation of SF3B4 expression and regulates the immunity in ovarian cancer

BACKGROUND

Ovarian cancer (OC) is the most lethal gynecologic malignant tumour. The mechanism promoting OC initiation and progression remains unclear. SET domain bifurcated histone lysine methyltransferase 1(SETDB1) acts as an oncogene in a variety of tumours. This study aims to explore the role of SETDB1 in OC.

METHODS

GEO, TCGA, CSIOVDB and CPTAC databases jointly analysed SETDB1 mRNA and protein expression. Effect of SETDB1 expression on the clinical prognosis of OC patients was analysed through online Kaplan‒Meier plotter and CSIOVDB database. Then, the effect of SETDB1 in OC cells progression and mobility was examined using MTT, EdU, colony formation and transwell assay. Additionally, Cistrome DB database was used to visualize the binding of SETDB1 protein and splicing factor 3b subunit 4 (SF3B4) promoter, and dual-luciferase reporter gene assay was performed to confirm the interaction. Finally, bioinformatics analysis was employed to reveal the relationship between SETDB1 and the microenvironment of OC.

RESULTS

In the present study, we found that SETDB1 was obviously upregulated in OC and its overexpression predicted poor prognosis of OC patients. Then, we verified that SETDB1 promoted the progression and motility of OC cells in vitro. Knockdown of SETDB1 had the opposite effect. Further research showed that SETDB1 acted as a transcription factor to activate SF3B4 expression. SF3B4 knockdown impaired the effect of SETDB1 to promote the proliferative capacity and motility of OC cells. Finally, the results of bioinformatics analysis confirmed that SETDB1 regulated the immune microenvironment of ovarian cancer.

CONCLUSION

SETDB1 promoted ovarian cancer progression by upregulating the expression of SF3B4 and inhibiting the tumour immunity. SETDB1 may be a promising prognostic and therapeutic marker for OC.

Exploring Potential Epigenetic Biomarkers for Colorectal Cancer Metastasis

Metastatic progression is a complex, multistep process and the leading cause of cancer mortality. There is growing evidence that emphasises the significance of epigenetic modification, specifically DNA methylation and histone modifications, in influencing colorectal (CRC) metastasis. Epigenetic modifications influence the expression of genes involved in various cellular processes, including the pathways associated with metastasis. These modifications could contribute to metastatic progression by enhancing oncogenes and silencing tumour suppressor genes. Moreover, specific epigenetic alterations enable cancer cells to acquire invasive and metastatic characteristics by altering cell adhesion, migration, and invasion-related pathways. Exploring the involvement of DNA methylation and histone modification is crucial for identifying biomarkers that impact cancer prediction for metastasis in CRC. This review provides a summary of the potential epigenetic biomarkers associated with metastasis in CRC, particularly DNA methylation and histone modifications, and examines the pathways associated with these biomarkers.

The functions of SET domain bifurcated histone lysine methyltransferase 1 (SETDB1) in biological process and disease

Histone methyltransferase SETDB1 (SET domain bifurcated histone lysine methyltransferase 1, also known as ESET or KMT1E) is known to be involved in the deposition of the di- and tri-methyl marks on H3K9 (H3K9me2 and H3K9me3), which are associated with transcription repression. SETDB1 exerts an essential role in the silencing of endogenous retroviruses (ERVs) in embryonic stem cells (mESCs) by tri-methylating H3K9 (H3K9me3) and interacting with DNA methyltransferases (DNMTs). Additionally, SETDB1 is engaged in regulating multiple biological processes and diseases, such as ageing, tumors, and inflammatory bowel disease (IBD), by methylating both histones and non-histone proteins. In this review, we provide an overview of the complex biology of SETDB1, review the upstream regulatory mechanisms of SETDB1 and its partners, discuss the functions and molecular mechanisms of SETDB1 in cell fate determination and stem cell, as well as in tumors and other diseases. Finally, we discuss the current challenges and prospects of targeting SETDB1 for the treatment of different diseases, and we also suggest some future research directions in the field of SETDB1 research.

Protein post-translational modifications: A key factor in colorectal cancer resistance mechanisms

Colorectal cancer (CRC) is one of the leading causes of cancer-related death. Despite advances in treatment, drug resistance remains a critical impediment. Post-translational modifications (PTMs) regulate protein stability, localization, and activity, impacting vital cellular processes. Recent research has highlighted the essential role of PTMs in the development of CRC resistance. This review summarizes recent advancements in understanding PTMs' roles in CRC resistance, focusing on the latest discoveries. We discuss the functional impact of PTMs on signaling pathways and molecules involved in CRC resistance, progress in drug development, and potential therapeutic targets. We also summarize the primary enrichment methods for PTMs. Finally, we discuss current challenges and future directions, including the need for more comprehensive PTM analysis methods and PTM-targeted therapies. This review identifies potential therapeutic interventions for addressing medication resistance in CRC, proposes prospective therapeutic options, and gives an overview of the function of PTMs in CRC resistance.

The role of dietary polyphenols in alternating DNA methylation in cancer

Natural products such as curcumin, quercetin, and resveratrol have been shown to have antitumor effectsand several studies have examined their role in treating cancer, either alone or in combination with other chemotherapeutic drugs. These compounds are capable of affecting different cancer-related mechanisms, such as proliferation, inflammation, invasion, and metastasis. Along with all of the benefits of these agents, affecting epigenetic processes is one of the most important aspects of their impact. Epigenetic modifications can be categorized into three main processes that include DNA methylation, histone modification, and regulation of small non-coding RNAs. Therefore, targeting DNA methylation can be used as a cancer treatment strategy by identifying or developing methylation modulators. Herein, we take a look into the studies investigating the role of natural products (e.g. curcumin, resveratrol, epigallocatechin gallate (EGCG), and quercetin) in alternating the DNA methylation status of various cancer cells. We discuss how these compounds reduce the expression of enzymes mediating the methylation of tumor suppressor genes and thereby, increasing the expression of tumor suppressors while reactivating antitumor signaling pathways.

Chromatin factors: Ready to roll as biomarkers in metastatic colorectal cancer?

Colorectal cancer (CRC) ranks as the third most prevalent cancer globally and stands as the fourth leading cause of cancer-related fatalities in 2020. Survival rates for metastatic disease have slightly improved in recent decades, with clinical trials showing median overall survival of approximately 24-30 months. This progress can be attributed to the integration of chemotherapeutic treatments alongside targeted therapies and immunotherapy. Despite these modest improvements, the primary obstacle to successful treatment for advanced CRC lies in the development of chemoresistance, whether inherent or acquired, which remains the major cause of treatment failure. Epigenetics has emerged as a hallmark of cancer, contributing to master transcription regulation and genome stability maintenance. As a result, epigenetic factors are starting to appear as potential clinical biomarkers for diagnosis, prognosis, and prediction of treatment response in CRC.In recent years, numerous studies have investigated the influence of DNA methylation, histone modifications, and chromatin remodelers on responses to chemotherapeutic treatments. While there is accumulating evidence indicating their significant involvement in various types of cancers, the exact relationship between chromatin landscapes and treatment modulation in CRC remains elusive. This review aims to provide a comprehensive summary of the most pertinent and extensively researched epigenetic-associated mechanisms described between 2015 and 2022 and their potential usefulness as predictive biomarkers in the metastatic disease.

Histone modifications in drug-resistant cancers: From a cancer stem cell and immune evasion perspective

The development and immune evasion of cancer stem cells (CSCs) limit the efficacy of currently available anticancer therapies. Recent studies have shown that epigenetic reprogramming regulates the expression of characteristic marker proteins and tumor plasticity associated with cancer cell survival and metastasis in CSCs. CSCs also possess unique mechanisms to evade external attacks by immune cells. Hence, the development of new strategies to restore dysregulated histone modifications to overcome cancer resistance to chemotherapy and immunotherapy has recently attracted attention. Restoring abnormal histone modifications can be an effective anticancer strategy to increase the therapeutic effect of conventional chemotherapeutic and immunotherapeutic drugs by weakening CSCs or by rendering them in a naïve state with increased sensitivity to immune responses. In this review, we summarize recent findings regarding the role of histone modifiers in the development of drug-resistant cancer cells from the perspectives of CSCs and immune evasion. In addition, we discuss attempts to combine currently available histone modification inhibitors with conventional chemotherapy or immunotherapy.

SETDB1 induces lenalidomide resistance in multiple myeloma cells via epithelial‑mesenchymal transition and PI3K/AKT pathway activation

SET domain bifurcated histone lysine methyltransferase 1 (SETDB1) is a histone H3K9 methyltransferase that stimulates cell proliferation by methylating AKT, which contributes to drug resistance in multiple myeloma (MM). Lenalidomide is an immunomodulatory agent widely used in the treatment of MM. However, lenalidomide resistance occurs in patients with MM. Currently, the role of SETDB1 in lenalidomide resistance in MM remains unclear. Thus, the present study aimed to explore the functional association between SETDB1 and lenalidomide resistance in MM. The analysis of GEO datasets revealed that SETDB1 was upregulated in lenalidomide-resistant MM cells and that its expression was associated with poor prognosis of patients with MM. Apoptosis analysis revealed that overexpression of SETDB1 in MM cells significantly decreased apoptosis, while knockdown of SETDB1 increased apoptosis. Furthermore, the IC₅₀ value of lenalidomide in MM cells increased following SETDB1 overexpression and decreased following SETDB1 silencing. Additionally, SETDB1 mediated epithelial-mesenchymal transition (EMT) and activated the PI3K/AKT pathway. Mechanistic analysis revealed that inhibition of PI3K/AKT signaling in MM cells increased apoptosis, sensitized the cells to lenalidomide and inhibited EMT, whereas SETDB1 overexpression inhibited the effects of PI3K/AKT cascade inhibition. In conclusion, the findings of the present study indicated that SETDB1 promoted lenalidomide resistance in MM cells by promoting EMT and the PI3K/AKT signaling pathway. Thus, SETDB1 may be a potential therapeutic target for MM.

SETDB1 confers colorectal cancer metastasis by regulation of WNT/β-catenin signaling

BACKGROUND

Metastasis is a critical step in tumor development; however, its specific molecular mechanism is still not fully understood. SETDB1 overexpression is associated with tumor progression and poor prognosis. Here, we explored a novel mechanism by which SETDB1 promotes tumor metastasis in colorectal cancer.

METHODS

We conducted database and clinical specimen analysis to determine the expression level of SETDB1 in colorectal cancer, as well as the prognosis of colorectal cancer with overexpressed SETDB1. We used wound healing assays, Transwell assays, and animal studies to study the effect of SETDB1 on colorectal cancer. We performed western blotting, qRT-PCR, immunofluorescence, and co-immunoprecipitation to explore the underlying associations between SETDB1 and β-catenin. We further used wound healing assays, Transwell assays, and animal studies to verify the relationship between SETDB1 and Wnt/β-catenin.

RESULTS

SETDB1 expression was upregulated in colorectal cancer and correlated with poor prognosis. Low expression of SETDB1 decreased invasion and metastasis in colorectal cancer. Low-expression of SETDB1 in colorectal tumor cells decreased β-catenin expression and its nuclear import. We also found that SETDB1 can bind and directly methylate β-catenin, Lastly, we discovered that this metastatic ability could be decreased by activating the Wnt/β-catenin pathway with SETDB1 knock-down.

CONCLUSION

SETDB1 is highly expressed in colorectal cancer and plays an important role in the invasion and metastasis through the Wnt/β-catenin pathway. It does so by direct methylation of β-catenin. This novel SETDB1/Wnt/β-catenin pathway provides a new strategy for the treatment of colorectal cancer.

The Role of Histone Modification in DNA Replication-Coupled Nucleosome Assembly and Cancer

Histone modification regulates replication-coupled nucleosome assembly, DNA damage repair, and gene transcription. Changes or mutations in factors involved in nucleosome assembly are closely related to the development and pathogenesis of cancer and other human diseases and are essential for maintaining genomic stability and epigenetic information transmission. In this review, we discuss the role of different types of histone posttranslational modifications in DNA replication-coupled nucleosome assembly and disease. In recent years, histone modification has been found to affect the deposition of newly synthesized histones and the repair of DNA damage, further affecting the assembly process of DNA replication-coupled nucleosomes. We summarize the role of histone modification in the nucleosome assembly process. At the same time, we review the mechanism of histone modification in cancer development and briefly describe the application of histone modification small molecule inhibitors in cancer therapy.

CircPTK2/PABPC1/SETDB1 axis promotes EMT-mediated tumor metastasis and gemcitabine resistance in bladder cancer

Bladder cancer (BCa), characterized by high invasion, metastasis, recurrence, and chemoresistance, is one of the most prevalent urologic malignant tumors. Recent studies have highlighted the potential impact of the circRNAs-protein complex in tumorigenesis. However, the mechanisms by which the circRNAs-protein complex regulates BCa metastasis and chemoresistance remain elusive. Herein, we identified an upregulated circRNA, circPTK2, which could regulate SETDB1 expression by analyzing the transcriptome by RNA-sequencing. Importantly, using circRNA pulldown assay and RNA-binding protein immunoprecipitation, we identified PABPC1 as a robust novel interacting protein of circPTK2. Mechanistically, circPTK2 could bind to PABPC1 and enhance its ability to stabilize SETDB1 mRNA, thereby specifically promoting SETDB1 expression and facilitating SETDB1-mediated epithelial-mesenchymal transition (EMT). Functionally, overexpression of the circPTK2-SETDB1 axis markedly promoted migration, invasion, and gemcitabine resistance in vitro and enhanced lymph node metastasis in vivo. Collectively, our findings clarified a hitherto unexplored mechanism of the circPTK2/PABPC1/SETDB1 axis in EMT-mediated tumor metastasis and gemcitabine resistance in BCa.

SETDB1 interactions with PELP1 contributes to breast cancer endocrine therapy resistance

Background

Methyltransferase SETDB1 is highly expressed in breast cancer (BC), however, the mechanisms by which SETDB1 promotes BC progression to endocrine therapy resistance remains elusive. In this study, we examined the mechanisms by which SETDB1 contribute to BC endocrine therapy resistance.

Methods

We utilized therapy sensitive (MCF7 and ZR75), therapy resistant (MCF7-TamR, MCF7-FR, MCF7-PELP1cyto, MCF7-SETDB1) estrogen receptor alpha positive (ER⁺)BC models and conducted in vitro cell viability, colony formation, 3-dimensional cell growth assays to investigate the role of SETDB1 in endocrine resistance. RNA-seq of parental and SETDB1 knock down ER⁺ BC cells was used to identify unique pathways. SETDB1 interaction with PELP1 was identified by yeast-two hybrid screen and confirmed by immunoprecipitation and GST-pull down assays. Mechanistic studies were conducted using Western blotting, reporter gene assays, RT-qPCR, and in vitro methylation assays. Xenograft assays were used to establish the role of PELP1 in SETDB1 mediated BC progression.

Results

RNA-seq analyses showed that SETDB1 regulates expression of a subset of estrogen receptor (ER) and Akt target genes that contribute to endocrine therapy resistance. Importantly, using yeast-two hybrid screen, we identified ER coregulator PELP1 as a novel interacting protein of SETDB1. Biochemical analyses confirmed SETDB1 and PELP1 interactions in multiple BC cells. Mechanistic studies confirmed that PELP1 is necessary for SETDB1 mediated Akt methylation and phosphorylation. Further, SETDB1 overexpression promotes tamoxifen resistance in BC cells, and PELP1 knockdown abolished these effects. Using xenograft model, we provided genetic evidence that PELP1 is essential for SETDB1 mediated BC progression in vivo. Analyses of TCGA datasets revealed SETDB1 expression is positively correlated with PELP1 expression in ER⁺ BC patients.

Conclusions

This study suggests that the PELP1/SETDB1 axis play an important role in aberrant Akt activation and serves as a novel target for treating endocrine therapy resistance in breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-022-01520-4.

The SETDB1-TRIM28 Complex Suppresses Antitumor Immunity

The tumor immune microenvironment is influenced by the epigenetic landscape of the tumor. Here, we have identified the SETDB1-TRIM28 complex as a critical suppressor of antitumor immunity. An epigenetic CRISPR-Cas9 screen of 1,218 chromatin regulators identified TRIM28 as a suppressor of PD-L1 expression. We then revealed that expression of the SETDB1-TRIM28 complex negatively correlated with infiltration of effector CD8⁺ T cells. Inhibition of SETDB1-TRIM28 simultaneously upregulated PD-L1 and activated the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) innate immune response pathway to increase infiltration of CD8⁺ T cells. Mechanistically, SETDB1-TRIM28 inhibition led to micronuclei formation in the cytoplasm, which is known to activate the cGAS-STING pathway. Thus, SETDB1-TRIM28 inhibition bridges innate and adaptive immunity. Indeed, SETDB1 knockout enhanced the antitumor effects of immune checkpoint blockade with anti-PD-L1 in a mouse model of ovarian cancer in a cGAS-dependent manner. Our findings establish the SETDB1-TRIM28 complex as a regulator of antitumor immunity and demonstrate that its loss activates cGAS-STING innate immunity to boost the antitumor effects of immune checkpoint blockade.

Regulation of signal transduction pathways in colorectal cancer: implications for therapeutic resistance

Resistance to anti-cancer treatments is a critical and widespread health issue that has brought serious impacts on lives, the economy and public policies. Mounting research has suggested that a selected spectrum of patients with advanced colorectal cancer (CRC) tend to respond poorly to both chemotherapeutic and targeted therapeutic regimens. Drug resistance in tumours can occur in an intrinsic or acquired manner, rendering cancer cells insensitive to the treatment of anti-cancer therapies. Multiple factors have been associated with drug resistance. The most well-established factors are the emergence of cancer stem cell-like properties and overexpression of ABC transporters that mediate drug efflux. Besides, there is emerging evidence that signalling pathways that modulate cell survival and drug metabolism play major roles in the maintenance of multidrug resistance in CRC. This article reviews drug resistance in CRC as a result of alterations in the MAPK, PI3K/PKB, Wnt/β-catenin and Notch pathways.

Lemur tyrosine kinase-3 (LMTK3) induces chemoresistance to cetuximab in colorectal cancer via the ERK/MAPK pathway

As an oncogenic kinase in multiple cancers, LMTK3 was deeply implicated in cancer pathogenesis. Nevertheless, its biological function in colorectal cancer (CRC) is still unclear. In this study, LMTK3 mRNA expression was assessed by RT-qPCR. LMTK3, phospho-ERK1/2 (p-ERK1/2), ERK1/2, and cleaved caspase-3 protein levels were detected by western blotting. Cetuximab (CTX)-resistant CRC cell models were constructed to investigate the mechanism of LMTK3-regulated CTX resistance in CRC. CTX half-maximal inhibitory concentration (IC₅₀), viability, apoptosis, cell cycle, migration, and invasion of CRC cells were analyzed via Cell Counting Kit-8 (CCK-8), flow cytometry, wound healing, and transwell assays. We found LMTK3 was distinctly upregulated in CRC tissues and cells, particularly in CTX-resistant CRC tissues and cells. LMTK3 inhibition lowered CTX half-maximal inhibitory concentration (IC₅₀) value, inhibited cell viability, induced cell apoptosis, triggered cell-cycle arrest, and impaired cell metastatic capability in CTX-resistant CRC cells. Moreover, we also demonstrated that LMTK3 induced CTX resistance in CRC via the activation of ERK/MAPK signaling in vitro. These results suggested a novel molecular mechanism by which LMTK3 participates in the development of CTX resistance in CRC.

HIST2H2BF Potentiates the Propagation of Cancer Stem Cells via Notch Signaling to Promote Malignancy and Liver Metastasis in Colorectal Carcinoma

Background

Growing evidence demonstrates that the initiation and progression of colorectal carcinoma (CRC) is related to the presence of cancer stem cells (CSCs). However, the mechanism through which the stem cell features of CRC cells are maintained is poorly understood. In this study, we identified the oncogenic histone cluster 2 H2B family member F (HIST2H2BF) and aimed to investigate the function of upregulated HIST2H2BF expression in maintaining the stem cell features of CRC cells, which accelerate the progression of CRC.

Methods

HIST2H2BF expression was quantified using real-time polymerase chain reaction, immunohistochemistry, and western blotting. The correlation between CpG island methylation status and HIST2H2BF re-expression was assessed through bisulfite sequencing polymerase chain reaction, methylation-specific polymerase chain reaction, and 5-Aza-dC treatment. Functional assays were performed on CRC cells and mice to investigate the HIST2H2BF-induced stem cell-like and cancer properties of CRC. Using the Notch pathway inhibitor FLI-06, the regulatory effect of HIST2H2BF on downstream Notch signaling was confirmed.

Results

HIST2H2BF was highly expressed in CRC tissues and cell lines. The reactivation of HIST2H2BF in CRC stems at least in part from the hypomethylated CpG islands. CRC patients with high HIST2H2BF expression have poor survival outcomes. Functional studies have shown that HIST2H2BF promotes CSC phenotype, malignancy, and liver metastasis through the activation of Notch signaling in CRC. Blockage of the Notch pathway reduced the stem cell-like and cancer properties.

Conclusion

Our study suggests that HIST2H2BF upregulation enhances the CSC phenotype, malignancy, and liver metastasis through the activation of Notch signaling in CRC. These results identified a new perspective on the mechanism by which the stem cell features of CRC cells are maintained and highlighted the potential novel therapeutic targets for CRC.

NSD2 promotes tumor angiogenesis through methylating and activating STAT3 protein

Tumor angiogenesis plays vital roles in tumorigenesis and development; regulatory mechanism of angiogenesis is still not been fully elucidated. NSD2, a histone methyltransferase catalyzing di-methylation of histone H3 at lysine 36, has been proved a critical molecule in proliferation, metastasis, and tumorigenesis. But its role in tumor angiogenesis remains unknown. Here we demonstrated that NSD2 promoted tumor angiogenesis in vitro and in vivo. Furthermore, we confirmed that the angiogenic function of NSD2 was mediated by STAT3. Momentously, we found that NSD2 promoted the methylation and activation of STAT3. In addition, mass spectrometry and site-directed mutagenesis assays revealed that NSD2 methylated STAT3 at lysine 163 (K163). Meanwhile, K to R mutant at K163 of STAT3 attenuated the activation and angiogenic function of STAT3. Taken together, we conclude that methylation of STAT3 catalyzed by NSD2 promotes the activation of STAT3 pathway and enhances the ability of tumor angiogenesis. Our findings investigate a NSD2-dependent methylation-phosphorylation regulation pattern of STAT3 and reveal that NSD2/STAT3/VEGFA axis might be a potential target for tumor therapy.

SETD8 potentiates constitutive ERK1/2 activation via epigenetically silencing DUSP10 expression in pancreatic cancer

Constitutive ERK1/2 activation has been frequently observed in pancreatic adenocarcinoma (PDAC). How ERK1/2 activation status been potentiated and maintained by epigenetic mechanisms has seldom been discussed in PDAC. In this study, we first examined the expression status of p-ERK1/2 in PDAC tissues by immunohistochemical staining and then screened possible epigenetic factors that displayed different expression status between p-ERK1/2 high and low groups by RNA profiling, and found that SETD8 displayed an increased expressional pattern in p-ERK1/2high patient group. Then the impact of SETD8 on the proliferation of PDAC cells were investigated on the basis of gain or loss-of-function assays. RNA sequencing assays were performed to screen potential SETD8 downstream targets that contribute to ERK1/2 activation. Mass spectrometry and transcriptional analysis, including dual-luciferase assay and chromatin immunoprecipitation assay (ChIP), were used to explore the molecular mechanisms that governing SETD8-mediated ERK1/2 activation. In vitro cell line studies and in vivo xenograft mouse model studies indicated that SETD8 promoted cell proliferation and increased tumor formation capacity of PDAC cell lines. Mechanism explorations uncovered that SETD8 suppressed the expression of DUSP10, which was responsible for dephosphorylation of ERK1/2. Mass spectrometry and transcriptional analysis results demonstrated that STAT3 interacted with SETD8 and recruited SETD8 to the promoter region of DUSP10, leading to epigenetic silencing of DUSP10 and the resultant activation of ERK1/2. In conclusion, SETD8 interacts with STAT3 on DUSP10 promoter region and epigenetically silences DUSP10 expression. Decreased DUSP10 expression in PDAC potentiates activation of ERK1/2 phosphorylation, resulting in unfavorable prognosis of PDAC.

Insight into the multi-faceted role of the SUV family of H3K9 methyltransferases in carcinogenesis and cancer progression

Growing evidence implicates histone H3 lysine 9 methylation in tumorigenesis. The SUV family of H3K9 methyltransferases, which include G9a, GLP, SETDB1, SETDB2, SUV39H1 and SUV39H2 deposit H3K9me1/2/3 marks at euchromatic and heterochromatic regions, catalyzed by their conserved SET domain. In cancer, this family of enzymes can be deregulated by genomic alterations and transcriptional mis-expression leading to alteration of transcriptional programs. In solid and hematological malignancies, studies have uncovered pro-oncogenic roles for several H3K9 methyltransferases and accordingly, small molecule inhibitors are being tested as potential therapies. However, emerging evidence demonstrate onco-suppressive roles for these enzymes in cancer development as well. Here, we review the role H3K9 methyltransferases play in tumorigenesis focusing on gene targets and biological pathways affected due to misregulation of these enzymes. We also discuss molecular mechanisms regulating H3K9 methyltransferases and their influence on cancer. Finally, we describe the impact of H3K9 methylation on therapy induced resistance in carcinoma. Converging evidence point to multi-faceted roles for H3K9 methyltransferases in development and cancer that encourages a deeper understanding of these enzymes to inform novel therapy.