Prognostic significance of Cbx4 expression and its beneficial effect for transarterial chemoembolization in hepatocellular carcinoma

Unravelling the impact of the chromobox proteins in human cancers

Chromobox (CBX) proteins play a crucial role in regulating epigenetic processes. They are extensively involved in various biological processes, including embryonic development, stem cell maintenance, cell proliferation and apoptosis control. The disruption and malfunction of CBXs in cancer typically results in the interference or abnormal activation of developmental pathways, which facilitate the onset, growth, and advancement of cancer. This review initially introduces the physiological properties and functions of the CBXs. Subsequently, it examines the involvement of CBXs in different cancer types. Cancer hallmarks driven by CBXs are mediated through multiple mechanisms, including changes in gene expression patterns, epigenetic dysregulation of chromatin control, disruption of intracellular signaling and alterations in cell metabolism. The study also highlights novel potential anticancer therapeutics targeting CBXs in cancer. In this review we provide novel perspectives and a solid foundation for future investigations on CBXs as promising therapeutic targets for cancer treatment.

CBX4 plays a bidirectional role in transcriptional regulation and lung adenocarcinoma progression

Lung adenocarcinoma (LUAD) remains a leading cause of cancer-related mortality worldwide. Understanding the dysregulated epigenetics governing LUAD progression is pivotal for identifying therapeutic targets. CBX4, a chromobox protein, is reported to be upregulated in LUAD. This study highlights the dual impact of CBX4 on LUAD proliferation and metastasis through a series of rigorous in vitro and in vivo experiments. Further investigation into the underlying mechanism through high-throughput ChIP-seq and RNA-seq reveals that CBX4 functions in promoting LUAD proliferation via upregulating PHGDH expression and subsequent serine biosynthesis, while concurrently suppressing LUAD metastasis by inhibiting ZEB2 transcription. CBX4 facilitates PHGDH transcription through the interaction with GCN5, inducing heightened histone acetylation on the PHGDH promoter. Simultaneously, the inhibition of ZEB2 transcription involves CBX4-mediated recruitment of canonical PRC1 (cPRC1), establishing H2K119ub on the ZEB2 promoter. These findings underscore CBX4's pivotal role as a regulator of LUAD progression, emphasizing its diverse transcriptional regulatory functions contingent upon interactions with specific epigenetic partners. Understanding the nuanced interplay between CBX4 and epigenetic factors sheds light on potential therapeutic avenues in LUAD.

Two pairs of 2-pyrone enantiomers and a benzophenone analogue from the endophytic fungus Penicillium egyptiacum

Four new 2-pyrone derivatives, two pairs of enantiomers, (±)-egypyrone A [(±)-1] and (±)-egypyrone B [(±)-2], together with a new benzophenone analogue, orbiophenone B (3), were isolated from the endophytic fungus Penicillium egyptiacum. The enantiomeric mixtures (±)-1 and (±)-2 were separated through chiral HPLC, respectively. Their structures were elucidated by extensive analysis of spectroscopic data and the absolute configuration was determined by comparing the optical rotation of structurally similar molecule. Subsequently, the cytotoxic activities of (±)-1, (±)-2, and 3 against the U87 cell line were tested and no activity was observed at a concentration of 10 µM.

Aflatoxin B1-DNA adducts modify the effects of post-operative adjuvant transarterial chemoembolization improving hepatocellular carcinoma prognosis

AIM

DNA damage involves in the carcinogenesis of some cancer and may act as a target for therapeutic intervention of cancers. However, it is unclear whether aflatoxin B1 (AFB1)-DNA adducts (ADAs), an important kind of DNA damage caused by AFB1, affect the efficiency of post-operative adjuvant transarterial chemoembolization (po-TACE) treatment improving hepatocellular carcinoma (HCC) survival.

METHODS

A hospital-based retrospective study, including 318 patients with Barcelona Clinic Liver Cancer (BCLC)-C stage HCC from high AFB1 exposure areas, to investigate the potential effects of ADAs in the tissues with HCC on po-TACE treatment. The amount of ADAs in the cancerous tissues was tested by competitive enzyme-linked immunosorbent assay (c-ELISA).

RESULTS

Among these patients with HCC, the average amount of ADAs was 3.00 µmol/mol ± 1.51 µmol/mol DNA in their tissues with cancer. For these patients, increasing amount of ADAs was significantly associated with poorer overall survival (OS) and tumor reoccurrence-free survival (RFS), with corresponding death risk (DR) of 3.69 (2.78-4.91) and tumor recurrence risk (TRR) of 2.95 (2.24-3.88). The po-TACE therapy can efficiently improve their prognosis [DR = 0.59 (0.46-0.76), TRR = 0.63 (0.49-0.82)]. Interestingly, this improving role was more noticeable among these patients with high ADAs [DR = 0.36 (0.24-0.53), TRR = 0.40 (0.28-0.59)], but not among those with low ADAs (P > 0.05).

CONCLUSIONS

These results suggest that increasing ADAs in the cancerous tissues may be beneficial for po-TACE in ameliorating the survival of patients with HCC.

Vessels that encapsulate tumor clusters (VETC) pattern predicts the efficacy of adjuvant TACE in hepatocellular carcinoma

PURPOSE

Postoperative adjuvant trans-catheter arterial chemoembolization (TACE) is regarded as a common strategy for hepatocellular carcinoma (HCC) patients at a high risk of recurrence. However, there are currently no clinically available biomarkers to predict adjuvant TACE response. Vessels that encapsulate tumor clusters (VETC) can be used as an independent predictor of HCC prognosis. In this study, we aimed to explore whether the VETC pattern could predict adjuvant TACE benefit.

METHODS

Vascular pattern and HIF-1α expression were detected in immunohistochemistry. The survival benefit of adjuvant TACE therapy for patients with or without VETC pattern (VETC+ /VETC-) was evaluated.

RESULTS

The adjuvant TACE therapy obviously improved the TTR and OS in VETC+ patients, while adjuvant TACE therapy could not benefit from VETC- patients. Univariate and multivariate analysis revealed that adjuvant TACE therapy significantly improved the TTR and OS in VETC+ patients, but not in VETC- patients. In addition, the VETC+ , but not VETC- , patients could benefit from adjuvant TACE therapy in patients with high-risk factors of vascular invasion, larger tumor or multiple tumor. The mechanistic investigations revealed that the favorable efficacy of adjuvant TACE on VETC+ patients, but not VETC- ones, may be not due to the activation of HIF-1α pathway.

CONCLUSION

The VETC pattern may represent a novel and reliable factor for selecting HCC patients who may benefit from adjuvant TACE therapy, and the combination of VETC pattern and tumor characteristics may help stratify patients' outcomes and responses to adjuvant TACE therapy.

Comprehensive bioinformatics analysis of the expression, prognostic value, and immune infiltration of chromobox family members in cervical cancer

Objectives

Cervical cancer (CC) is the fourth most prevalent type of cancer in women worldwide and it is considered the leading cause of tumor-related death and malignancy. As part of complexes involved in epigenetic control, the proteins of the chromobox (CBX) family have been found to have a role in the growth of malignancies by preventing differentiation and increasing proliferation. Here, by a thorough investigation, we investigated the expression, prognostic significance, and immune infiltration of CBX in patients with CC.

Materials and Methods

Differential expression, clinicopathological parameters, immune cell infiltration, enrichment analysis, genetic alteration, and prognostic value of CBXs in patients with CC were examined using TIMER, Metascape, STRING, GeneMANIA, cBioPortal, UALCAN, The Human Protein Atlas, Gene Expression Profiling Interactive Analysis (GEPIA), and Oncomine.

Results

In CC tissues, CBX 2/3/4/5 and CBX 8 expression levels were considerably higher, whereas CBX 6/7 expression levels were lower. In CC, the CBX 5/6/8 promoters have elevated levels of methylation. The expression of CBX 2/6/8 and the pathological stage were connected. A 37% mutation rate of the differentially expressed CBX genes was observed. Also, there was a strong correlation of the CBXs expression with immune cell infiltration, such as T CD4⁺ cells, macrophages, neutrophils, B cells, T CD8⁺ cells, and dendritic cells.

Conclusion

The investigation discovered that members of the CBXs family may be therapeutic targets for CC patients and may play significant roles in the development of CC tumors.

Useful genes for predicting the efficacy of transarterial chemoembolization in hepatocellular carcinoma

Transarterial chemoembolization (TACE) is generally used to treat patients with hepatocellular carcinoma (HCC), a common and deadly cancer; however, its efficacy varies according to factors such as tumor volume, stage, serum alpha-fetoprotein level, and chosen feeding artery. In addition, gene-related factors have been recently suggested to be involved in the regulation and prediction of TACE outcomes. Accordingly, genes could serve as effective biomarkers to select patients who can benefit from TACE. These gene-related factors can activate signaling pathways affecting cancer cell survival while regulating the epithelial-mesenchymal transition, angiogenesis, and the tumor microenvironment, all directly associated with tumor progression, thereby affecting TACE efficacy. Moreover, this disordered gene expression is associated with poor prognosis in patients with HCC, including TACE resistance, postoperative recurrence, and metastasis. To identify the exact relationship between various genes and TACE efficacy, this review summarizes the involvement of protein-coding and non-coding genes and single nucleotide polymorphisms in TACE efficacy for predicting the efficacy of TACE; the present findings may help improve the efficacy of TACE in clinical settings.

Critical Roles of Polycomb Repressive Complexes in Transcription and Cancer

Polycomp group (PcG) proteins are members of highly conserved multiprotein complexes, recognized as gene transcriptional repressors during development and shown to play a role in various physiological and pathological processes. PcG proteins consist of two Polycomb repressive complexes (PRCs) with different enzymatic activities: Polycomb repressive complexes 1 (PRC1), a ubiquitin ligase, and Polycomb repressive complexes 2 (PRC2), a histone methyltransferase. Traditionally, PRCs have been described to be associated with transcriptional repression of homeotic genes, as well as gene transcription activating effects. Particularly in cancer, PRCs have been found to misregulate gene expression, not only depending on the function of the whole PRCs, but also through their separate subunits. In this review, we focused especially on the recent findings in the transcriptional regulation of PRCs, the oncogenic and tumor-suppressive roles of PcG proteins, and the research progress of inhibitors targeting PRCs.

Chromobox 4 (CBX4) promotes tumor progression and stemness via activating CDC20 in gastric cancer

BACKGROUND

The Chromobox homolog 4 (CBX4) has been found to be overexpressed in multiple malignancies. However, the associations between CBX4 and gastric cancer (GC) have remained unclear. This study aimed to determine the biological roles of CBX4 in GC and identify effective therapeutic targets.

METHODS

The 3-(4,5-dimethylthiazol-2-yl) (MTT) assays were used to screen CBX family members. Differential analysis was utilized to evaluate the CBX4 levels. Kaplan-Meier analysis was used to perform prognostic analysis. Western blotting assay, quantitative polymerase chain reaction (qPCR) assay and immunohistochemistry (IHC) were used to assess CBX4 expressions. Colony formation assay, Cell Counting Kit-8 (CCK-8) assay, and Transwell assay were used to assess progression features of cells. The tail vein injection model was utilized to determine the metastatic efficacy of GC cells. Tumor sphere formation assay was used to assess tumor stemness maintenance ability. Chromatin immunoprecipitation (ChIP)-qPCR assay was used to evaluate the associations between CBX4 and CDC20. A subcutaneous tumor model was used to assess the in vivo growth ability of GC.

RESULTS

The MTT assay revealed that only CBX4 inhibition could lead to notable restriction of GC growth, as compared to others. Differential analysis suggested that CBX4 was upregulated in tumor samples relative to normal tissues. Less favorable overall survival (OS) outcomes were noticed in GC patients with high CBX4 in comparison to those with low CBX4. High CBX4 could notably enhance cell proliferation capacity, migration ability, and in vivo metastatic efficacy. Gene set enrichment analysis (GSEA) indicated the relationships between CBX4 and GC stemness, and CBX4 overexpression could remarkably elevate self-renewal ability of GC cells. In addition, CBX4 could mainly promote CDC20 messenger RNA (mRNA) levels, and targeting CBX4 suppressed the relative CDC20 levels. The ChIP-qPCR assay further demonstrated that CBX4 coordinated with H3K4me3 to bind at the CDC20 promoter region. Additionally, CBX4 depended on CDC20 to drive GC growth. Lastly, downregulated CBX4 could notably inhibit the growth of GC in vivo.

CONCLUSIONS

This study highlights the oncogenic roles of CBX4 in GC. CBX4 activates CDC20 to maintain stemness features of GC, thereby creating therapeutic vulnerabilities in the treatment of GC.

Members of the Chromobox Family Have Prognostic Value in Hepatocellular Carcinoma

Liver cancer is the fifth most prevalent malignant tumor, while hepatocellular carcinoma represents the most prevalent subtype worldwide. Previous studies have associated the chromobox family, critical components of epigenetic regulatory complexes, with development of many malignancies owing to their role in inhibiting differentiation and promoting proliferation of cancer cells. However, little is known regarding their function in development and progression of hepatocellular carcinoma. In the present study, we analyzed differential expression, prognostic value, immune cell infiltration, and gene pathway enrichment of chromobox family in hepatocellular carcinoma patients. Next, we performed Pearson’s correlation analysis to determine the relationships between chromobox family proteins with tumor-immune infiltration. Results revealed that high expression of CBX1, CBX2, CBX3, CBX6, and CBX8 was associated with poor survival rates of hepatocellular carcinoma patients. These five factors were used to build prognostic gene models using LASSO Cox regression analysis. Results indicated that high expression of CBX2 and CBX3 proteins was significantly associated with poor prognosis for hepatocellular carcinoma patients. The resulting nomogram revealed that CBX3 and T stages were significantly correlated with prognosis of hepatocellular carcinoma patients. Notably, predictive CBX3 was strongly correlated with immune cell infiltration. Furthermore, results from functional enrichment analysis revealed that CBX3 was mainly involved in regulation of methylation of Histone H3-K27. Collectively, these findings suggest that CBX3 could be a biomarker for predicting prognosis of hepatocellular carcinoma patients.

Mechanisms of Polycomb group protein function in cancer

Cancer arises from a multitude of disorders resulting in loss of differentiation and a stem cell-like phenotype characterized by uncontrolled growth. Polycomb Group (PcG) proteins are members of multiprotein complexes that are highly conserved throughout evolution. Historically, they have been described as essential for maintaining epigenetic cellular memory by locking homeotic genes in a transcriptionally repressed state. What was initially thought to be a function restricted to a few target genes, subsequently turned out to be of much broader relevance, since the main role of PcG complexes is to ensure a dynamically choregraphed spatio-temporal regulation of their numerous target genes during development. Their ability to modify chromatin landscapes and refine the expression of master genes controlling major switches in cellular decisions under physiological conditions is often misregulated in tumors. Surprisingly, their functional implication in the initiation and progression of cancer may be either dependent on Polycomb complexes, or specific for a subunit that acts independently of other PcG members. In this review, we describe how misregulated Polycomb proteins play a pleiotropic role in cancer by altering a broad spectrum of biological processes such as the proliferation-differentiation balance, metabolism and the immune response, all of which are crucial in tumor progression. We also illustrate how interfering with PcG functions can provide a powerful strategy to counter tumor progression.

The predictive potential of genetic single nucleotide polymorphisms in CBX4 for hepatocellular carcinoma survival

Background: Our previous studies have reported that polycomb chromobox 4 (CBX4) has a potential promoting hepatocellular carcinoma (HCC) angiogenesis and tumor progression. However, it is unclear whether genetic single-nucleotide polymorphisms (SNPs) in this gene are associated with HCC prognosis. Methods: We conducted a hospital-based two-phase study, including 598 patients with pathologically diagnosed HCC for the SNPs screening phase and 328 HCC patients for clinic significance validating phase, to elucidate the association between SNPs of CBX4 and the survival of HCC. The genotypes of CBX4 were tested using the SNaPshot method and the effects of CBX4 SNPs on HCC prognosis were analyzed using Kaplan-Meier survival model and Cox regression model. Results: A total of 33 SNPs were selected and genotyped in this study. We found the rs77447679 SNP was significantly related to survival in individuals with HCC. Specifically, survival was noticeably decreased in HCC patients who have mutant homozygote AA of this SNP (rs77447679-AA) compared with these with wild type (rs77447679-CC). An additive effect of rs77447679 polymorphism and aflatoxin B1 exposure level was also observed in the survival analyses of HCC cases. Furthermore, this SNP was positively correlated not only with tumor size, grade, stage, and microvessel density (correlation coefficient r = 0.17, 0.23, 0.23, and 0.42, respectively), but also with increasing CBX4 expression (r = 0.57). Interestingly, the mutant genotypes of rs77447679 can significantly improve the therapeutic response of HCC cases on post-operative adjuvant transarterial chemoembolization (pa-TACE), but wild type not. Conclusions: These data suggest that genetic polymorphisms in the CBX4 may be a prognostic biomarker for HCC, and the rs77447679 SNP is such a potential candidate.

The SUMO E3 ligase CBX4 is identified as a poor prognostic marker of gastric cancer through multipronged OMIC analyses

Gastric cancer (GC) is one of the most common malignancies, with an ever-increasing incidence and high mortality rate. Chromobox4 (CBX4), also named hPC2, is a small ubiquitin-related modifier (SUMO) E3 ligase. Previous studies have found that high CBX4 expression is associated with tumor size, pathologic differentiation and decreased patient survival in hepatocellular carcinoma (HCC). However, the expression and prognostic value of CBX4 in GC have not been clarified. In our study, ONCOMINE, UALCAN, Kaplan-Meier Plotter, cBioPortal, DAVID 6.8 and TIMER were utilized. RT-PCR, immunohistochemistry (IHC), Western blot, CCK-8 assay, cell apoptosis assay, cell cycle assay were used to further verify in GC tissue samples or cell line. The transcriptional and protein level of CBX4 in GC tissues was found significantly elevated and a significant association between the expression of CBX4 and clinicopathological parameters was found in GC patients. Low expression of CBX4 in GC patients were correlated with a significantly improved prognosis. The functions of CBX4 are primarily related to the stem cell pluripotency signaling pathway, Hippo signaling pathway, HTLV-I infection, Notch signaling pathway, and N-glycan biosynthesis. Our results may provide novel insights for the selection of therapeutic targets and prognostic biomarkers for GC.

Therapeutic Potential of Targeting the SUMO Pathway in Cancer

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer. The delicate balance between SUMOylation and deSUMOylation is regulated by SENP enzymes possessing SUMO-deconjugation activity. Dysregulation of SUMO machinery components can disrupt the balance of SUMOylation, contributing to the tumorigenesis and drug resistance of various cancers in a context-dependent manner. Many molecular mechanisms relevant to the pathogenesis of specific cancers involve SUMO, highlighting the potential relevance of SUMO machinery components as therapeutic targets. Recent advances in the development of inhibitors targeting SUMOylation and deSUMOylation permit evaluation of the therapeutic potential of targeting the SUMO pathway in cancer. Finally, the first drug inhibiting SUMO pathway, TAK-981, is currently also being evaluated in clinical trials in cancer patients. Intriguingly, the inhibition of SUMOylation may also have the potential to activate the anti-tumor immune response. Here, we comprehensively and systematically review the recent developments in understanding the role of SUMOylation in cancer and specifically focus on elaborating the scientific rationale of targeting the SUMO pathway in different cancers.

Comprehensive Analysis of the Expression and Prognosis Value of Chromobox Family Members in Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) accounts for 80% of all renal cancers and has a poor prognosis. Chromobox (CBX) family protein expression has been reported in a variety of human malignancies, but the roles of CBXs in ccRCC remain unclear. In this study, by using ONCOMINE, UALCAN, GEPIA, Kaplan-Meier Plotter, cBioPortal, and TIMER, we found the transcriptional levels of CBX3 and CBX4 in ccRCC tissues were significantly higher than those in normal kidney tissues, whereas the transcriptional levels of CBX1, CBX5, CBX6, and CBX7 were significantly reduced in ccRCC tissues. The promoters of CBX2, CBX3, CBX4, CBX5, CBX6, CBX7, and CBX8 were hypermethylated, whereas the CBX1 promoter was hypomethylated in ccRCC. The expression of CBX1, CBX3, CBX4, CBX5, CBX6, and CBX7 was significantly associated with clinicopathological parameters in ccRCC patients. ccRCC patients with high expression levels of CBX3, CBX4, and CBX8 and low expression levels of CBX1, CBX5, CBX6, and CBX7 showed a strong association with poor overall survival. Genetic alterations in CBXs were correlated with poor overall survival and disease-free survival in patients with ccRCC. Moreover, we found significant associations between the expression of CBXs and infiltration of immune cells (B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells). Our results provide novel insights into the development of CBX-based biomarkers and therapeutic targets for ccRCC.

Human Polycomb Protein 2 (hPC2) as a Novel Independent Prognostic Marker in Nasopharyngeal Carcinoma

Purpose

Human polycomb protein 2(hPC2) is a vital component of polycomb repressive complex 1(PRC1). It plays a critical role in tumorigenesis and progression. However, whether HPC2 expression affects the prognosis of patients with nasopharyngeal carcinoma (NPC) is currently unclear. In the present study, we investigated the expression of hPC2and elucidated its clinical prognostic significance in NPC.

Patients and Methods

The expression of hPC2 in 180 NPCs samples was examined by immunohistochemistry (IHC) and evaluated by H-score staining intensity. Receiver operator characteristic (ROC) curve analysis was performed to determine cut-off values of hPC2 expression. The chi-square test, Kaplan–Meier (Log rank test), and the Cox proportional hazards model were utilized to analyze the data.

Results

We found hPC2 is highly expressed in 48.3% of NPC specimens, which significantly correlated with T stage (p=0.032), N stage (p=0.006), and clinical stage (p=0.003). Kaplan–Meier analysis indicated that NPCs with high hPC2 expression tended to have a lower cumulative rates of overall survival (OS, p<0.001), recurrence-free survival (RFS, p=0.001), and distant metastasis-free survival (DMFS, p=0.003). In the NPCs subgroup, T3–T4, N2–N3, and stages III–IV, high hPC2 expression also had a prognostic impact on worse outcome in terms of OS, RFS, and DMFS. More importantly, multivariate analyses demonstrated that hPC2 expression was an independent prognostic factor for OS (hazard ratio [HR], 95% (confidence interval [CI]), p=0.001), RFS (HR, 95% CI, p=0.018), and DMFS (HR, 95% CI, p=0.022).

Conclusion

We present evidence that high expression of hPC2 correlated with poorer prognosis in NPC. hPC2 could serve as a novel prognostic biomarker and might be a promising therapeutic target for NPC.

Inhibiting CBX4 efficiently protects hepatocellular carcinoma cells against sorafenib resistance

BACKGROUND

This study aimed to investigate the possible role of inhibiting chromobox protein homologue 4 (CBX4) to deregulate of cancer stem cells (CSCs) and to evaluate the contribution of these molecules to sorafenib resistance in advanced hepatocellular carcinoma (HCC).

METHODS

HCC cell lines and a xenograft mouse model with resistance to sorafenib were employed to analyse the effects of miR424 on CSC characteristics. RNA expression was analysed by RT-PCR and next-generation sequencing in a cohort of HCC cancer patients and sorafenib-resistant (SR) cell lines, respectively, to validate the key microRNAs and targets in the network.

RESULTS

MicroRNA and mRNA profiles of SR cell lines identified miR424 and its direct target CBX4 as significantly associated with stem-cell-like properties, poor survival, and clinical characteristics. Functional experiments demonstrated that miR424 suppressed CBX4 and CBX4 induced nuclear translocation of YAP1 protein but was not associated with protein production. When YAP1 and CBX4 were modulated with CA3 and UNC3866, tumorigenicity and stem-like properties were extremely inhibited, thus indicating that these compounds exerted a strong anti-tumour effect in vivo against SR HCC cells.

CONCLUSIONS

Our results revealed that blocking CBX4 expression is critical in response to sorafenib resistance with advanced HCC.

Comprehensive analysis of the prognosis for chromobox family in gastric cancer

Background

Chromobox (CBX) family proteins are a class of transcriptional repressors involved in epigenetic regulation and developmental processes of various tumors, including gastric cancer. However, the function and prognosis of different CBXs in gastric cancer remain unknown.

Methods

This study addresses this issue by synthesizing several mainstream databases (Oncomine, GEPIA2, cBioportal, and Kaplan-Meier plotter, among others) that currently contain many tumor samples and provide very reliable analysis results, investigating the role of CBXs in the prognosis of gastric cancer.

Results

The mRNA of CBX1/2/3/4/5/8 was highly expressed in gastric cancer, the mRNA of CBX7 was lowly expressed in gastric cancer, and the mRNA expression of CBX6 was not significantly different in CRC. Besides, high and low CBXs mRNA expression correlated with cancer stage, node metastasis status, H. pylori infection status, and tumor grade in CRC patients. We found that high mRNA expression of CBX4/5/6/7/8 was significantly associated with worse overall survival (OS), progression-free survival (FP), and post-progression survival (PPS) in a large number of CRC patients. High mRNA expression of CBX3 was significantly associated with better OS and FP. We also found that none of the eight CBXs family genes had a mutation rate of less than 5% in gastric cancer, and the highest mutation rate was in CBX3 (14%).

Conclusions

These results suggest that CBX3/4/5/6/7/8 could be a prognostic biomarker in gastric cancer patients.

CircTLK1 promotes the proliferation and metastasis of renal cell carcinoma by sponging miR-136-5p

BACKGROUND

Circular RNAs (circRNAs), a novel type of noncoding RNA (ncRNA), are covalently linked circular configurations that form via a loop structure. Accumulating evidence indicates that circRNAs are potential biomarkers and key regulators of tumor development and progression. However, the precise roles of circRNAs in renal cell carcinoma (RCC) remain unknown.

METHODS

Through circRNA high-throughput sequencing of RCC cell lines, we identified the circRNA TLK1 (circTLK1) as a novel candidate circRNA derived from the TLK1 gene. qRT-PCR detected the mRNA, circRNA and miRNA expression levels in RCC tissues and cells. Loss-of function experiments were executed to detect the biological roles of circTLK1 in the RCC cell phenotypes in vitro and in vivo. RNA-FISH, RNA pull-down, dual-luciferase reporter, western blot and immunohistochemistry assays were used to investigate the molecular mechanisms underlying the functions of circTLK1.

RESULTS

circTLK1 is overexpressed in RCC, and expression is positively correlated with distant metastasis and unfavorable prognosis. Silencing circTLK1 significantly inhibited RCC cell proliferation, migration and invasion in vitro and in vivo. circTLK1 was mainly distributed in the cytoplasm and positively regulated CBX4 expression by sponging miR-136-5p. Forced CBX4 expression reversed the circTLK1 suppression-induced phenotypic inhibition of RCC cells. Moreover, CBX4 expression was positively correlated with VEGFA expression in RCC tissues. CBX4 knockdown significantly inhibited VEGFA expression in RCC cells.

CONCLUSION

Collectively, our findings demonstrate that circTLK1 plays a critical role in RCC progression by sponging miR-136-5p to increase CBX4 expression. circTLK1 may act as a diagnostic biomarker and therapeutic target for RCC.

[Establishment and gene expression analysis of drug-resistant cell lines in hepatocellular carcinoma induced by sorafenib]

OBJECTIVE

To establish the drug-resistant cell lines of hepatocellular carcinoma (HCC) induced by sorafenib, and to screen out the high expression genes in drug-resistant cell lines of HCC induced by sorafenib, then to explore the genes related to sorafenib resistance in hepatocellular carcinoma.

METHODS

The human PLC and Huh7 cell lines were obtained, then the PLC and Huh7 drug-resistant cell lines were induced with sorafenib by using intermittent induction in vitro. CCK8 assay was used to detect the IC50 value of sorafenib for evaluation of drug sensitivity of hepatocellular carcinoma cell lines in PLC and Huh7. All the up regulated genes in PLC and Huh7 drug-resistant cell lines induced by sorafenib were screened out using high-throughput cDNA sequencing (RNA-Seq), Ualcan database was used to analyze the correlations between the up regulated genes in PLC and Huh7 drug-resistant cell lines induced and four clinical biological characteristics of hepatocellular carcinoma, including the gene expressions between normal samples and tumor samples, tumor stage, tumor grade, and patient overall survival, to find the genes that might be involved in the mechanism of sorafenib resistance of hepatocellular carcinoma.

RESULTS

All the up regulated genes detected by the using high-throughput cDNA sequencing (RNA-Seq) in PLC and Huh7 drug-resistant cell lines were further screened out by following conditions:(1) genes co-expressed in PLC and Huh7 drug-resistant cells induced by sorafenib, (2) the fold change was more than 4 times and the difference was statistically significant (P <0.05), the top 12 up regulated genes in PLC and Huh7 drug-resistant cell lines were found, which were TPSG1, CBX4, CLC, CLEC18C, LGI4, F2RL1, S100A6, HABP2, C15ORF48, ZG16, FOLH1, and EPCAM. Compared with the correlations between the twelve genes and the clinical biological characteristics by Ualcan database, the potentially significant gene CBX4 was screened out.

CONCLUSION

The human PLC and Huh7 drug-resistant cell lines of hepatocellular carcinoma induced by sorafenib were successfully established. CBX4, the gene related to sorafenib resistance in hepatocellular carcinoma, was screened out by the high-throughput cDNA sequencing (RNA-Seq) and further analysis using Ualcan database, which is providing a powerful basis for further research on the mechanism of sorafenib resistance of hepatocellular carcinoma.

Hyperactivation of IL-6/STAT3 pathway leaded to the poor prognosis of post-TACE HCCs by HIF-1α/SNAI1 axis-induced epithelial to mesenchymal transition

Transarterial chemoembolization (TACE) has been considered the standard treatment for intermediate-stage hepatocellular carcinoma according to BCLC algorithm. However, it has been unclear about the TACE-related predictive bio-markers and underlying molecular mechanisms. This investigation revealed that HCCs with higher HIF-1α suffered from unfavorable OS after TACE. mRNA expression microarray revealed that HIF-1α was potential target of p-STAT3 which was verified by ChIP and immunoblotting assay. Activation of IL-6/STAT3/HIF-1α signaling was found to promote EMT and chemoresistance to Doxorubicin in vitro and in vivo by regulating SNAI1. Hypoxia did not enhance HIF-1α expression and influence cell growth and chemoresistence to Doxorubicin in HCC cells when STAT3 expression was abolished. Taken together, HIF-1α overexpression in HCC tissues predicted the unfavorable outcome of HCCs after TACE and IL-6/STAT3 pathway resulted in EMT induced-metastases and chemoresistance of HCC after TACE through HIF-1α/SNAI1 axis.

MicroRNA-497-5p Induces Cell Cycle Arrest Of Cervical Cancer Cells In S Phase By Targeting CBX4

Purpose

miR-497-5p can inhibit cervical cancer cell proliferation. However, the underlying mechanism remains to be elucidated.

Methods

Bioinformatics was used to analyze the target genes of miR-497-5p. qRT-PCR and Western blot were used to analyze mRNA and protein expression, respectively. Dual-luciferase reporter assay was used to analyze the direct binding between miR-497-5p and 3'-untranslated region of CBX4. Cell viability was measured with MTT assay. Flow cytometry was performed to detect cell cycle distribution.

Results

Here, using bioinformatics methods we firstly found that miR-497-5p regulated cervical carcinoma proliferation by targeting polycomb chromobox4 (CBX4). Expression of miR-497-5p in cervical carcinoma tissues was negatively correlated with CBX4. A binding region of miR-497-5p in 3'-untranslated region of CBX4 was predicted. Further experiments confirmed that miR-497-5p directly targeted CBX4. Besides, RNA interference of CBX4 inhibited cervical cancer cell proliferation, arrested cells at S phase and reduced the expression of CDK2 and Cyclin A2 proteins. The use of miR-497-5p inhibitor compromised CBX4 interference RNAs induced cycle arrest of cervical cancer cells. Cells co-transfected with miR-497-5p inhibitors and CBX4 interference RNAs had a higher proliferation rate than CBX4 inference RNA-transfected cells.

Conclusion

All together, the present study demonstrates that miR-497-5p inhibits cervical cancer cells proliferation by directly targeting CBX4.

Three new α-pyrone derivatives from the plant endophytic fungus Penicillium ochrochloronthe and their antibacterial, antifungal, and cytotoxic activities

Three new 3,4,6-trisubstituted α-pyrone derivatives, namely 6-(2'R-hydroxy-3'E,5'E-diene-1'-heptyl)-4-hydroxy-3-methyl-2H-pyran-2-one (1), 6-(2'S-hydroxy-5'E-ene-1'-heptyl)-4-hydroxy-3-methyl-2H-pyran-2-one (2), and 6-(2'S-hydroxy-1'-heptyl)-4 -hydroxy-3-methyl-2H-pyran-2-one (3), together with one known compound trichodermic acid (4), were isolated from the solid-substrate fermentation culture of Penicillium ochrochloronthe associated the roots of Taxus media. Compounds 1-4 displayed the antimicrobial activity selectively against tested fungal and bacterial strains with minimum inhibitory concentration (MIC) values ranging from 12.5 to 100 μg/ml. Furthermore, we found that only compound 4 exhibited moderate cytotoxicity against five human cancer cells (A549, LN229, MGC, LOVO, and MDA231) with IC₅₀ values of 51.45, 23.43, 39.16, 46.97, and 42.85 μg/ml, respectively.

Transcriptional expressions of Chromobox 1/2/3/6/8 as independent indicators for survivals in hepatocellular carcinoma patients

Chromobox (CBX) proteins are important components of epigenetic regulation complexes known to play key roles in hepatocellular carcinoma (HCC). Little is known about the function of distinct CBXs in HCC. To address this issue, the study investigated the roles of CBXs in the prognosis of HCC using ONCOMINE, UALCAN, Human Protein Atlas, Kaplan-Meier Plotter, c-BioPortal databases. Over expressions of 8 CBXs members were found to be significantly associated with clinical cancer stages and pathological tumor grades in HCC patients. Besides, higher mRNA expressions of CBX1/2/3/6/8 were found to be significantly associated with shorter overall survival (OS) in HCC patients, while higher mRNA expression of CBX7 was associated with favorable OS. Multivariate analysis also showed that high mRNA expressions of CBX1/2/3/6/8 were independent prognostic factors for shorter OS of HCC patients. Moreover, high mutation rate of CBXs (51%) was also observed in HCC patients, and genetic alteration in CBXs was associated with shorter OS and disease-free survival (DFS) in HCC patients. Taken together, these results indicated that CBX1/2/3/6/8 could be prognostic biomarkers for survivals of HCC patients.

Micro RNA-4651 Serves as a Potential Biomarker for Prognosis When Selecting Hepatocellular Carcinoma Patients for Postoperative Adjuvant Transarterial Chemoembolization Therapy

Our previous reports have shown that microRNA-4651 is a potential early diagnostic and prognostic marker for hepatocellular carcinoma. We aimed to investigate whether microRNA-4651 modified postoperative adjuvant transarterial chemoembolization (pa-TACE) to improve the prognosis of hepatocellular carcinoma. A hospital-based retrospective study, including 302 patients with advanced-stage hepatocellular carcinoma who received tumor resection or tumor resection plus pa-TACE as an initial therapy, was conducted to assess the effects of microRNA-4651 on pa-TACE treatment. MicroRNA-4651 expression in tumor tissues was tested using the TaqMan-PCR technique. The sensitivity of tumor cells to doxorubicin (an anticancer drug used in pa-TACE procedure) was analyzed by the half-maximal inhibitory concentration (IC50). Upregulated microRNA-4651 expression in tumor tissues can improve the therapeutic response of patients with hepatocellular carcinoma on pa-TACE (hazard ratios [95% confidence intervals] = 0.32 [0.22-0.46] for death risk and 0.39 [0.28-0.56] for tumor-recurrence risk, respectively), but downregulated expression cannot. Functional analyses-displayed microRNA-4651 mimics decreased while its inhibitor increased the IC50 of tumor cells to doxorubicin (0.65 [0.61-0.69] versus 2.17 [1.98-2.37] µM). Cytochrome P450 2W1 was shown as a possible target of microRNA-4651. Additionally, dysregulation of microRNA-4651 also affected the clinical pathological features of hepatocellular carcinoma and was an independent prognostic factor for this cancer. Conclusion: These results indicate that increasing microRNA-4651 expression may be beneficial for pa-TACE in improving hepatocellular carcinoma prognosis.

SUMOylation and phosphorylation cross-talk in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a primary malignancy of the liver and occurs predominantly in patients with underlying chronic liver disease and cirrhosis. The large spectrum of protein post-translational modification (PTM) includes numerous critical signaling events that occur during neoplastic transformation. PTMs occur to nearly all proteins and increase the functional diversity of proteins. We have reviewed the role of two major PTMs, SUMOylation and phosphorylation, in the altered signaling of key players in HCC. SUMOylation is a PTM that involves addition of a small ubiquitin-like modifiers (SUMO) group to proteins. It is known to regulate protein stability, protein-protein interactions, trafficking and transcriptional activity. The major pathways that are regulated by SUMOylation and may influence HCC are regulation of transcription, cell growth pathways associated with B-cell lymphoma 2 (Bcl-2) and methionine adenosyltransferases (MAT), oxidative stress pathways [nuclear erythroid 2-related factor 2 (Nrf2)], tumor suppressor pathways (p53), hypoxia-inducible signaling [hypoxia-inducible factor-1 (HIF-1)], glucose and lipid metabolism, nuclear factor kappa B (NF-κB) and β-Catenin signaling. Phosphorylation is an extensively studied PTM in HCC. The mitogen-activated protein kinase (MAPK), phosphatidyl inositol/AK-strain transforming (PI3K/AKT), and C-SRC pathways have been extensively studied for deregulation of kinases and alteration in signaling of targets through phosphorylation of their substrates. Cross-talk between phosphorylation and SUMOylation is known to influence transcriptional activity of proteins and protein-protein interactions. In HCC, several SUMOylation-dependent phosphorylation events have been studied such as MAPK activation and c-SRC activity that have been reviewed in this work. The drastic effects of site-specific phosphorylation or SUMOylation on enzyme activity of signaling players and its effect on growth and tumorigenesis suggests that these PTMs are novel targets for therapeutic intervention in HCC.

CBX4 exhibits oncogenic activities in breast cancer via Notch1 signaling

Polycomb chromobox (CBX) proteins are involved in gene silencing to function as oncogenes or tumor suppressors through the polycomb repressive complex (PRC1). CBX4 has been implicated in the progression of human cancers, but its role and clinical significance in breast cancer remain unclear. Here, we show that CBX4 is up-regulated in breast cancer and exerts oncogenic activities via miR-137-mediated activation of Notch1 signaling pathway. CBX4 expression was increased in breast cancer, compared with the nontumorous tissues. High CBX4 expression was closely correlated with tumor metastasis, advanced clinical stage and poor overall survival in a cohort of 179 patients with breast cancer. In vitro studies demonstrated that CBX4 overexpression enhanced, whereas CBX4 knockdown inhibited cell growth and migration. Mechanistically, in a PRC1-dependent manner, CBX4 inhibited the promoter activity of miR-137 and suppressed its expression. miR-137 decreased the expression of Notch1, Jag1 and Hey2 via targeting their 3'-UTRs. The suppression of Notch1 by siRNA or overexpression of miR-137 markedly attenuated CBX4-promoted phenotypes. Collectively, these findings indicate that CBX4 promotes breast cancer via miR-137-mediated Notch1 signaling. Our data, therefore, suggest that CBX4 serve as a prognostic biomarker and that targeting CBX4/miR-137 axis may provide therapeutic potent in the treatment of breast cancer.

Prognostic significance of XRCC4 expression in hepatocellular carcinoma

BACKGROUND

Our previous investigations have shown that the variants of X-ray repair complementing 4 (XRCC4) may be involved in hepatocellular carcinoma (hepatocarcinoma) tumorigenesis. This study aimed to investigate the possible prognostic significance of XRCC4 expression for hepatocarcinoma patients and possible value for the selection of transarterial chemoembolization (TACE) treatment.

MATERIALS AND METHODS

We conducted a hospital-based retrospective analysis (including 421 hepatocarcinoma cases) to analyze the effects of XRCC4 on hepatocarcinoma prognosis and TACE. The levels of XRCC4 expression were tested using immunohistochemistry. The sensitivity of cancer cells to anti-cancer drug doxorubicin was evaluated using the half-maximal inhibitory concentration (IC50).

RESULTS

XRCC4 expression was significantly correlated with pathological features including tumor stage, liver cirrhosis, and micro-vessel density. XRCC4 expression was an independent prognostic factor of hepatocarcinoma, and TACE treatments had no effects on prognosis of hepatocarcinoma patients with high XRCC4 expression. More intriguingly, TACE improved the prognosis of hepatocarcinoma patients with low XRCC4 expression. Functionally, XRCC4 overexpression increased while XRCC4 knockdown reduced the IC50 of cancer cells to doxorubicin.

CONCLUSIONS

These results suggest that XRCC4 may be an independent prognostic factor for hepatocarcinoma patients, and that decreasing XRCC4 expression may be beneficial for post-operative adjuvant TACE treatment in hepatocarcinoma.

Association between Sumoylation-Related Gene rs77447679 Polymorphism and Risk of Gastric Cancer (GC) in a Chinese Population

Purpose: Sumoylation plays a critical role in gene regulation and tumorigenesis, and is hypothesized to correlate with the development of various cancers. So far, there has been no reported association between sumoylation-related genes and the risk of gastric cancer (GC).

Methods: A total of 17 tagging single-nucleotide polymorphisms (tag-SNPs) in 5 sumoylation-related genes were selected and genotyped by SNaPshot in a case-control study, including 1021 GC patients and 1304 controls. Odds ratio (OR) and 95% confidential interval (CI) were computed to evaluate the genetic association of the onset of GC.

Results: We demonstrated that CBX4 rs77447679 polymorphism was significantly associated with GC risk (P= 0.017; adjusted OR: 1.71; 95% CI: 1.10-2.66). The patients with CC genotype had a lower risk of GC (CC vs. CA+AA, P= 0.017; adjusted OR: 1.24; 95% CI: 1.04-1.49).

Conclusion: This study revealed that CBX4 rs77447679 polymorphism was positively associated with GC, and individuals with CC genotype had less risk of GC. The risky effects and functional effect of this polymorphism in GC require further investigation.

HDAC7 Ubiquitination by the E3 Ligase CBX4 Is Involved in Contextual Fear Conditioning Memory Formation

Histone acetylation, an epigenetic modification, plays an important role in long-term memory formation. Recently, histone deacetylase (HDAC) inhibitors were demonstrated to promote memory formation, which raises the intriguing possibility that they may be used to rescue memory deficits. However, additional research is necessary to clarify the roles of individual HDACs in memory. In this study, we demonstrated that HDAC7, within the dorsal hippocampus of C57BL6J mice, had a late and persistent decrease after contextual fear conditioning (CFC) training (4-24 h), which was involved in long-term CFC memory formation. We also showed that HDAC7 decreased via ubiquitin-dependent degradation. CBX4 was one of the HDAC7 E3 ligases involved in this process. Nur77, as one of the target genes of HDAC7, increased 6-24 h after CFC training and, accordingly, modulated the formation of CFC memory. Finally, HDAC7 was involved in the formation of other hippocampal-dependent memories, including the Morris water maze and object location test. The current findings facilitate an understanding of the molecular and cellular mechanisms of HDAC7 in the regulation of hippocampal-dependent memory.SIGNIFICANCE STATEMENT The current findings demonstrated the effects of histone deacetylase 7 (HDAC7) on hippocampal-dependent memories. Moreover, we determined the mechanism of decreased HDAC7 in contextual fear conditioning (CFC) through ubiquitin-dependent protein degradation. We also verified that CBX4 was one of the HDAC7 E3 ligases. Finally, we demonstrated that Nur77, as one of the important targets for HDAC7, was involved in CFC memory formation. All of these proteins, including HDAC7, CBX4, and Nur77, could be potential therapeutic targets for preventing memory deficits in aging and neurological diseases.

Serum cell death biomarker mirrors liver cancer regression after transarterial chemoembolisation

BACKGROUND

Hepatocellular carcinoma (HCC) represents an increasing health problem with limited therapeutic options. In patients with intermediate disease stage, transarterial chemoembolisation (TACE) is widely applied. Treatment response is routinely assessed by imaging techniques according to the international response evaluation criteria in solid tumours (RECIST), which consider tumour regression or additionally tumour necrosis (modified RECIST). Evaluation of treatment response, however, by these methods is time- and cost-intensive and usually performed at earliest several months following TACE.

AIM

To investigate the suitability of novel non-invasive cell death biomarkers for an earlier prediction of TACE response.

METHODS

We analysed activation of pro-apoptotic caspases and the proteolytic cleavage of the caspase substrate CK-18 in liver tissues and sera from HCC patients by immunohistochemistry, a luminometric substrate assay and ELISA.

RESULTS

Both caspase activity and caspase-cleaved CK-18 fragments were elevated in HCC patients compared to healthy controls. CK-18 serum levels significantly increased during the first 3 days and peaked at day two following TACE. Interestingly, we found significant differences in CK-18 levels between patients with and without tumour regression. Detection of CK-18 fragments revealed a promising performance for the early prediction of TACE response with an area under the curve value of 0.76.

CONCLUSIONS

Caspase-cleaved CK-18 levels mirror liver cancer regression and allow an earlier prediction of TACE response. The concordance with mRECIST suggests that the detection of CK-18 levels immediately after TACE might be used as a short-term decision guide to continue or change HCC therapy.

The long noncoding RNAs PVT1 and uc002mbe.2 in sera provide a new supplementary method for hepatocellular carcinoma diagnosis

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver in adults worldwide. Several studies have demonstrated that long noncoding RNAs (lncRNAs) are involved in the development of various types of cancer, including HCC. These findings prompted us to examine the detectability of lncRNAs in blood samples from patients with HCC. In this study, we explored the expression levels of 31 cancer-related lncRNAs in sera from 71 HCC patients and 64 healthy individuals by reverse transcription and quantitative polymerase chain reaction (RT-qPCR). We found that 25 lncRNAs could be detected in the serum and that 7 had significantly different expression levels. A 2-lncRNA signature (PVT1 and uc002mbe.2) identified by stepwise regression showed potential as a diagnostic marker for HCC. The area under the receiver operating characteristic (ROC) curve was 0.764 (95% CI: 0.684-0.833). The sensitivity and specificity values of this serum 2-lncRNA signature for distinguishing HCC patients from the healthy group were 60.56% and 90.62%, respectively. The diagnostic ability of the combination of the serum 2-lncRNA signature with alpha-fetoprotein (AFP) was much greater than that of AFP alone. The expression levels of the 2 lncRNAs were associated with clinical parameters including tumor size, Barcelona Clinic Liver Cancer (BCLC) stage, and serum bilirubin.

Epigenetic regulators: Polycomb-miRNA circuits in cancer

Polycomb group (PcG) proteins belong to a family of epigenetic modifiers and play a key role in dynamic control of their target genes. Several reports have found that aberrations in PcG-microRNA (miRNA) interplay in various cancer types often associated with poor clinical prognosis. This review discusses important PcG-miRNA molecular networks which act as critical interfaces between chromatin remodeling, and transcriptional and post-transcriptional regulation of their target genes in cancer. Moreover, here are discussed several compounds influencing the activity of PcG proteins entered in clinical arena for the treatment of solid tumors, multiple myeloma and B lymphomas, thus highlighting the therapeutic potential of targeting this protein family.

Chromobox Homolog 4 is Positively Correlated to Tumor Growth, Survival and Activation of HIF-1α Signaling in Human Osteosarcoma under Normoxic Condition

Objectives: The clinical significance and tumorigenesis of Chromobox homolog 4 (CBX4) have been reported in hepatocellular carcinoma. The purpose of this study is to confirm the expression, elucidate the biological function and investigate the potential mechanism of CBX4 in osteosarcoma (OS). Methods: The expression of CBX4 in OS samples and cell lines was measured by RT-PCR and western blot test. Cell cycle, CCK8 and colony-forming assays were used to detect changes of cells growth. Cell apoptosis assay was used to measure cell survival capacity. Trans-well assay was used to test the activities of migration and invasion. The expression of genes regulated by CBX4 was detected by qRT-PCT test. Results: The expression of CBX4 was up-regulated in multiple OS cell lines and clinical samples. Overexpression of CBX4 was correlated with advanced clinical stage, high degree of malignancy and low tumor necrosis rate. Moreover, knockdown of CBX4 resulted in significant inhibition of cell growth and cell survival in OS cells under normoxic condition. In addition, we found that knockdown of CBX4 lead to down-regulating of HIF-1α-targeted genes without changing HIF-1α expression itself. Conclusion: Taken together, CBX4 is up-regulated and has a pro-tumor effect in OS with an activation of HIF-1α signaling pathway under normoxic condition. Therefore, targeting CBX4 may provide a new therapeutic method for OS.

Chemical Inhibitors of Epigenetic Methyllysine Reader Proteins

Protein methylation is a common post-translational modification with diverse biological functions. Methyllysine reader proteins are increasingly a focus of epigenetics research and play important roles in regulating many cellular processes. These reader proteins are vital players in development, cell cycle regulation, stress responses, oncogenesis, and other disease pathways. The recent emergence of a small number of chemical inhibitors for methyllysine reader proteins supports the viability of these proteins as targets for drug development. This article introduces the biochemistry and biology of methyllysine reader proteins, provides an overview of functions for those families of readers that have been targeted to date (MBT, PHD, tudor, and chromodomains), and reviews the development of synthetic agents that directly block their methyllysine reading functions.