UHRF1 regulates global DNA hypomethylation and is associated with poor prognosis in esophageal squamous cell carcinoma

Globular adiponectin induces esophageal adenocarcinoma cell pyroptosis via the miR-378a-3p/UHRF1 axis

BACKGROUND

Antiapoptosis is a major factor in the resistance of tumor cells to chemotherapy and radiotherapy. Thus, activation of cell pyroptosis may be an effective option to deal with antiapoptotic cancers such as esophageal adenocarcinoma (EAC).

METHODS

Differential expression of ubiquitin-like versus PHD and ring finger structural domain 1 (UHRF1) in EAC and near normal tissues was analyzed, as well as the prognostic impact on survival in EAC. Also, the same study was done for globular adiponectin (gAD). Simultaneously, the mRNA expression of UHRF1 was observed in different EAC cell lines. Real time cellular analysis (RTCA) was used to detect cell proliferation, and flow cytometry and inverted fluorescence microscopy were used to detect pyroptosis. Biocredit analysis was conducted to observe the correlation between UHRF1 and key pyroptosis proteins. OD values and CCK8 assay were used to determine the effect of miR-378a-3p on EAC cells. Quantitative real-time polymerase chain reaction and Western blot were used to detect the correlation between UHRF1, gAD, and miR-378a-3p in EAC cells. Moreover, in vivo and in vitro experiments were performed to detect the relevant effects on tumor migration and invasion after inhibiting UHRF1 expression.

RESULTS

UHRF1 was negatively correlated with the survival of patients with EAC, while miR-378a-3p showed the opposite effect. Additionally, gAD promoted EAC cell pyroptosis, upregulated miR-378a-3p, and significantly inhibited the proliferation of EAC cells. gAD directly reduced UHRF1 expression in EAC cells by upregulating miR-378a-3p. In cell migration and invasion assays, inhibition of UHRF1 expression significantly suppressed EAC cell metastasis. In animal experiments, we again demonstrated that gAD induced pyroptosis in EAC cells by inhibiting the expression of UHRF1.

CONCLUSION

gAD-induced upregulation of miR-378a-3p significantly inhibited the proliferation of EAC by targeting UHRF1. Therefore, gAD may serve as an alternative therapy for chemotherapy- and radiation-refractory EAC or other cancers with the same mechanism of pyroptosis action.

Mechanistic insights into UHRF1‑mediated DNA methylation by structure‑based functional clarification of UHRF1 domains (Review)

Epigenetic modification is crucial for transmitting genetic information, while abnormalities in DNA methylation modification are primarily associated with cancer and neurological diseases. As a multifunctional epigenetic modifier, ubiquitin like with PHD and ring finger domains 1 (UHRF1) mainly affects cell energy metabolism and cell cycle control. It also inhibits the transcription of tumor suppressor genes through DNA and/or histone methylation modifications, promoting the occurrence and development of cancer. Therefore, comprehensively understanding the molecular mechanism of the epigenetic modification of UHRF1 in tumors will help identify targets for inhibiting the expression and function of UHRF1. Notably, each domain of UHRF1 functions as a whole and differently. Thus, the abnormality of any domain can lead to a change in phenotype or disease. However, the specific regulatory mechanism and proteins of each domain have not been fully elucidated. The present review aimed to contribute to the study of the regulatory mechanism of UHRF1 to a greater extent in different cancers and provide ideas for drug research by clarifying the function of UHRF1 domains.

Natural and Synthetic Anticancer Epidrugs Targeting the Epigenetic Integrator UHRF1

Cancer is one of the leading causes of death worldwide, and its incidence and mortality are increasing each year. Improved therapeutic strategies against cancer have progressed, but remain insufficient to invert this trend. Along with several other risk factors, abnormal genetic and epigenetic regulations play a critical role in the initiation of cellular transformation, as well as tumorigenesis. The epigenetic regulator UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1) is a multidomain protein with oncogenic abilities overexpressed in most cancers. Through the coordination of its multiple domains and other epigenetic key players, UHRF1 regulates DNA methylation and histone modifications. This well-coordinated dialogue leads to the silencing of tumor-suppressor genes (TSGs) and facilitates tumor cells' resistance toward anticancer drugs, ultimately promoting apoptosis escape and uncontrolled proliferation. Several studies have shown that the downregulation of UHRF1 with natural compounds in tumor cells induces the reactivation of various TSGs, inhibits cell growth, and promotes apoptosis. In this review, we discuss the underlying mechanisms and the potential of various natural and synthetic compounds that can inhibit/minimize UHRF1's oncogenic activities and/or its expression.

Comprehensive Pan-Cancer Analysis Reveals the Role of UHRF1-Mediated DNA Methylation and Immune Infiltration in Renal Cell Carcinoma

Ubiquitin-like PHD and ring finger domain protein 1 (UHRF1) are members of the multifunctional UHRF family, which can participate in DNA methylation change and histone posttranslational change through particular domains and participate in the event and development of tumors. The purpose of this study was to decide the molecular traits and potential medicine-based importance of UHRF1 that helped settle methylated immune infiltration in generalized cancer by carefully studying the relationship between UHRF1 expression and a variety of tumors and to further check for truth the functional role of UHRF1 in kidney-related cancer. A comprehensive analysis of UHRF1 in 33 cancers was performed based on TCGA database. This research involves analysis of mRNA expression profiles, prognostic value, immune infiltration, immune neoantigens, TMB, microsatellite instability, DNA methylation, and gene set enrichment analysis (GSEA). Both immune infiltration and DNA methylation were used to evaluate the importance and method of UHRF1 in renal cancer. The results showed that tumor tissue had higher expression level of UHRF1 than usual tissue. The high expression level of UHRF1 is related to the survival rate of renal cancer. UHRF1 expression was associated with tumor mutation load and microsatellite instability in different cancer types, and enrichment analysis identified terminology and pathways associated with UHRF1. This study showed that UHRF1 plays an important role in the group of objects and development of 33 tumors. UHRF1 may serve as a biomarker of immune infiltration and poor outlook of cancer.

The long non-coding RNA UPAT promotes gastric cancer cell progression via UHRF1

BACKGROUND

LncRNA ubiquitin-like with PHD and RING finger domains 1 (UHRF1) protein associated transcript (UPAT) regulates the progression of many cancers. However, its role in gastric cancer (GC) is less frequently reported.

OBJECTIVE

In the context of the promoting effect of lncRNA on modulating GC progression, detailed insights into the role and underlying mechanism of UPAT in GC are the foothold in this study.

METHODS

Overall survival was calculated. The mRNA expressions of UPAT and UHRF1 were measured by qRT-PCR, and the protein expressions of UHRF1, Cyclin D1 and cleaved caspase-3 were determined by western blot. Cell viability, growth, migration and invasion were assessed by CCK-8, colony formation, wound healing and Transwell assays, respectively. Apoptosis rate and cell cycle were assayed by flow cytometry.

RESULTS

UPAT was overexpressed in GC tissue and cell lines. Decreased UPAT level was associated with higher overall survival. Down-regulation of UPAT diminished cell proliferation, Cyclin D1 expression, and migration and invasion rates, increased apoptosis rate and cleaved caspase-3 expression, and blocked cell cycle in AGS and NCI-N87 cells. UPAT expression in GC was positively correlated with UHRF1 expression. UHRF1 overexpression offset the inhibitory effects of UPAT down-regulation on cell proliferation, migration, invasion and cell cycle, and partially reversed the positive effect of UPAT down-regulation on apoptosis.

CONCLUSION

UPAT might positively regulate the progression of GC via interacting with UHRF1. The UHRF1/UPAT axis revealed in the present study may provide a promising approach to intervene in the progression of GC.

Silencing UHRF1 Enhances Radiosensitivity of Esophageal Squamous Cell Carcinoma by Inhibiting the PI3K/Akt/mTOR Signaling Pathway

Purpose

Resistance to radiotherapy results in a high treatment failure rate for locally advanced esophageal squamous cell carcinoma (ESCC). Ubiquitin-like with plant homeodomain and ring-finger domains 1 (UHRF1), is associated with poor prognosis in ESCC. The present study aims to characterize the effect of UHRF1 silencing on the radiosensitivity of ESCC and its potential mechanism.

Methods

Both in vitro and in vivo experiments were conducted to observe the effects of UHRF1 silencing on the radiosensitivity of ESCC. The effects of UHRF1 silencing on the apoptosis of ESCC cells were assessed by flow cytometry. The expression of apoptosis-related factors (caspase-3 and Bcl-2), PI3K/Akt/mTOR signaling pathway-related factors (PTEN, p-Akt and Akt, p-mTOR and mTOR), and DNMT1 were measured via Western blot, and the status of PTEN methylation was detected by methylation-specific PCR. Immunohistochemistry was used to detect the expressions of PTEN, p-AKT, and p-mTOR in xenograft tumor tissues.

Results

In vitro and in vivo experiments showed that UHRF1 knock-down inhibited ESCC cell growth and enhanced their radiosensitivity. shUHRF1 combined with radiation significantly increased ESCC cell apoptosis. Meanwhile, it activated the expression of caspase-3 and inhibited the expression of Bcl-2. shUHRF1 inhibited the expression of DNMT1 and reduced the methylation of PTEN, and then upregulated the expression of PTEN to inhibit the PI3K/Akt/mTOR signaling pathway. On the contrary, the PI3K/Akt/mTOR signaling pathway can be activated by upregulation of UHRF1.

Conclusion

Our findings provide a theoretical basis for UHRF1 as a target to improve the radiosensitivity of ESCC.

Noncoding RNAs involved in DNA methylation and histone methylation, and acetylation in diabetic vascular complications

Diabetes is a metabolic disorder and its incidence is still increasing. Diabetic vascular complications cause major diabetic mobility and include accelerated atherosclerosis, nephropathy, retinopathy, and neuropathy. Hyperglycemia contributes to the pathogenesis of diabetic vascular complications via numerous mechanisms including the induction of oxidative stress, inflammation, metabolic alterations, and abnormal proliferation of EC and angiogenesis. In the past decade, epigenetic modifications have attracted more attention as they participate in the progression of diabetic vascular complications despite controlled glucose levels and regulate gene expression without altering the genomic sequence. DNA methylation and histone methylation, and acetylation are vital epigenetic modifications and their underlying mechanisms in diabetic vascular complication are still urgently needed to be investigated. Non-coding RNAs (nc RNAs) such as micro RNAs (miRNAs), long non-coding RNA (lncRNAs), and circular RNAs (circ RNAs) were found to exert transcriptional regulation in diabetic vascular complication. Although nc RNAs are not considered as epigenetic components, they are involved in epigenetic modifications. In this review, we summarized the investigations of non-coding RNAs involved in DNA methylation and histone methylation and acetylation. Their cross-talks might offer novel insights into the pathology of diabetic vascular complications.

UHRF1 Is a Novel Druggable Epigenetic Target in Malignant Pleural Mesothelioma

INTRODUCTION

Ubiquitin-like with plant homeodomain and ring finger domains 1 (UHRF1) encodes a master regulator of DNA methylation that has emerged as an epigenetic driver in human cancers. To date, no studies have evaluated UHRF1 expression in malignant pleural mesothelioma (MPM). This study was undertaken to explore the therapeutic potential of targeting UHRF1 in MPM.

METHODS

Microarray, real-time quantitative reverse transcription-polymerase chain reaction, immunoblot, and immunohistochemistry techniques were used to evaluate UHRF1 expression in normal mesothelial cells (NMCs) cultured with or without asbestos, MPM lines, normal pleura, and primary MPM specimens. The impact of UHRF1 expression on MPM patient survival was evaluated using two independent databases. RNA-sequencing, proliferation, invasion, and colony formation assays, and murine xenograft experiments were performed to evaluate gene expression and growth of MPM cells after biochemical or pharmacologic inhibition of UHRF1 expression.

RESULTS

UHRF1 expression was significantly higher in MPM lines and specimens relative to NMC and normal pleura. Asbestos induced UHRF1 expression in NMC. The overexpression of UHRF1 was associated with decreased overall survival in patients with MPM. UHRF1 knockdown reversed genomewide DNA hypomethylation, and inhibited proliferation, invasion, and clonogenicity of MPM cells, and growth of MPM xenografts. These effects were phenocopied by the repurposed chemotherapeutic agent, mithramycin. Biochemical or pharmacologic up-regulation of p53 significantly reduced UHRF1 expression in MPM cells. RNA-sequencing experiments exhibited the pleiotropic effects of UHRF1 down-regulation and identified novel, clinically relevant biomarkers of UHRF1 expression in MPM.

CONCLUSIONS

UHRF1 is an epigenetic driver in MPM. These findings support the efforts to target UHRF1 expression or activity for mesothelioma therapy.

Developmental and hormonal regulation of ubiquitin-like with plant homeodomain and really interesting new gene finger domains 1 gene expression in ovarian granulosa and theca cells of cattle

Ubiquitin-like with plant homeodomain and really interesting new gene finger domains 1 (UHRF1) is a multi-domain nuclear protein that plays an important role in epigenetics and tumorigenesis, but its role in normal ovarian follicle development remains unknown. Thus, the present study evaluated if UHRF1 mRNA abundance in bovine follicular cells is developmentally and hormonally regulated, and if changes in UHRF1 are associated with changes in DNA methylation in follicular cells. Abundance of UHRF1 mRNA was greater in granulosa cells (GC) and theca cells (TC) from small (<6 mm) than large (≥8 mm) follicles and was greater in small-follicle GC than TC. In GC and TC, fibroblast growth factor 9 (FGF9) treatment increased (P < 0.05) UHRF1 expression by 2-fold. Also, luteinizing hormone (LH) and insulin-like growth factor 1 (IGF1) increased (P < 0.05) UHRF1 expression in TC by 2-fold, and forskolin (an adenylate cyclase inducer) alone or combined with IGF1 increased (P < 0.05) UHRF1 expression by 3-fold. An E2F transcription factor inhibitor (E2Fi) decreased (P < 0.05) UHRF1 expression by 44% in TC and by 99% in GC. Estradiol, progesterone, and dibutyryl-cAMP decreased (P < 0.05) UHRF1 mRNA abundance in GC. Treatment of GC with follicle-stimulating hormone (FSH) alone had no effect but when combined with IGF1 enhanced the UHRF1 mRNA abundance by 2.7-fold. Beauvericin (a mycotoxin) completely inhibited the FSH plus IGF1-induced UHRF1 expression in small-follicle GC. Treatments that increased UHRF1 mRNA (i.e., FGF9) in GC tended to decrease (by 63%; P < 0.10) global DNA methylation, and those that decreased UHRF1 mRNA (i.e., E2Fi) in GC tended to increase (by 2.4-fold; P < 0.10) global DNA methylation. Collectively, these results suggest that UHRF1 expression in both GC and TC is developmentally and hormonally regulated, and that UHRF1 may play a role in follicular growth and development as well as be involved in ovarian epigenetic processes.

Multiple gene promoter methylation and clinical stage in adjacent normal tissues: Effect on prognosis of colorectal cancer in Taiwan

This study provide an insight that the panel genes methylation status in different clinical stage tended to reflect a different prognosis even in matched normal tissues, to clinical recommendation. We enrolled 153 colorectal cancer patients from a medical center in Taiwan and used the candidate gene approach to select five genes involved in carcinogenesis pathways. We analyzed the relationship between DNA methylation with different cancer stages and the prognostic outcome. There were significant trends of increasing risk of 5-year time to progression and event-free survival of subjects with raising number of hypermethylation genes both in normal tissue and tumor tissue. The group with two or more genes with aberrant methylation in the advanced cancer stages (Me/advanced) had lower 5-year event-free survival among patients with colorectal cancer in either normal or tumor tissue. The adjusted hazard ratios in the group with two or more genes with aberrant methylation with advanced cancer stages (Me/advanced) were 8.04 (95% CI, 2.80–23.1; P for trend <0.01) and 8.01 (95% CI, 1.92–33.4; P for trend <0.01) in normal and tumor tissue, respectively. DNA methylation status was significantly associated with poor prognosis outcome. This finding in the matched normal tissues of colorectal cancer patients could be an alternative source of prognostic markers to assist clinical decision making.

Lysyl oxidase impacts disease outcomes and correlates with global DNA hypomethylation in esophageal cancer

Abnormal function of human body enzymes and epigenetic alterations such as DNA methylation have been shown to lead to human carcinogenesis. Lysyl oxidase (LOX) enzyme has attracted attention due to its involvement in tumor progression in various cancers. The purpose of this study was to clarify the clinical importance of LOX expression and its epigenetic regulation in the pathogenesis of esophageal squamous cell carcinoma (ESCC). Using a database of 284 ESCCs, we examined LOX expression and its prognostic characteristics. The functional role of LOX was assessed by in vitro growth, migration, and invasion assays. The relationship between LOX expression, global DNA hypomethylation (ie, LINE‐1 methylation), and LOX promoter methylation was evaluated by using mRNA expression arrays and pyrosequencing technology. High LOX expression cases had a significantly shorter overall survival and cancer‐specific survival (log‐rank, P < .001). The prognostic effect of LOX expression was not significantly modified by other clinical variables. Silencing and enzymatic inhibition of LOX suppressed growth and reduced the invasion and migration ability of ESCC cell lines along with the downregulation of AKT and MMP2. An integrated gene analysis in tissues and cell lines revealed that LOX was the most highly upregulated gene in LINE‐1 hypomethylated tumors. In vitro, LOX expression was upregulated following DNA demethylation. LOX promoter methylation was not associated with LOX expression. Conclusively LOX expression was associated with poor prognosis in ESCC and was regulated epigenetically by genome‐wide hypomethylation. It could serve as a prognostic biomarker in ESCC patients, and therapeutically targeting LOX could reverse the progression of esophageal cancer.

THUMP domain containing 2 protein possibly induces resistance to cisplatin and 5-fluorouracil in in vitro human esophageal squamous cell carcinoma cells as revealed by transposon activation mutagenesis

BACKGROUND

Although chemotherapy is a core treatment for esophageal cancer, some patients develop drug resistance. Gene screening with transposons (i.e. mobile genetic elements) is a novel procedure for identifying chemotherapy-resistant genes. Transposon insertion can randomly affect nearby gene expression. By identifying the affected genes, candidate genes can be found. The present study aimed to identify cisplatin (CDDP)/5-fluorouracil (5-FU)-resistant genes in in vitro human esophageal squamous cell carcinoma with transposons.

METHODS

After establishing transposon-tagged cells, we obtained CDDP/5-FU-resistant colonies. A polymerase chain reaction and sequencing were used to identify the transposon inserted site and candidate CDDP/5-FU resistant genes. Focusing on one candidate gene, we confirmed CDDP/5-FU resistance by comparing the IC₅₀ between drug-resistant and wild-type cells. Furthermore, we investigated gene expression by a real-time polymerase chain reaction. Finally, we mediated the candidate gene level with small interfering RNA to confirm the resistance.

RESULTS

Thirty-nine candidate genes for CDDP/5-FU resistance were identified. Nineteen were for CDDP resistance and 27 were for 5-FU resistance. Seven genes, THUMP domain-containing protein 2 (THUMPD2), nuclear factor interleukin-3-regulated protein (NFIL3), tyrosine-protein kinase transmembrane receptor 2 (ROR2), C-X-C chemokine receptor type 4 (CXCR4), thrombospondin type-1 domain-containing protein 2 (THSD7B) alpha-parvin (PARVA) and TEA domain transcription factor 1 (TEAD1), were detected as candidate genes in both colonies. Regarding THUMPD2, its expression was downregulated and knocking down THUMPD2 suggested drug resistance in both drugs.

CONCLUSIONS

Thirty-nine candidate genes were identified with transposons. The downregulation of THUMPD2 was suggested to play a role in multidrug resistance in in vitro esophageal squamous cell carcinoma.

UHRF1 depletion and HDAC inhibition reactivate epigenetically silenced genes in colorectal cancer cells

BACKGROUND

Ubiquitin-like protein containing PHD and RING finger domains 1 (UHRF1) is a major regulator of epigenetic mechanisms and is overexpressed in various human malignancies. In this study, we examined the involvement of UHRF1 in aberrant DNA methylation and gene silencing in colorectal cancer (CRC).

RESULTS

CRC cell lines were transiently transfected with siRNAs targeting UHRF1, after which DNA methylation was analyzed using dot blots, bisulfite pyrosequencing, and Infinium HumanMethylation450 BeadChip assays. Gene expression was analyzed using RT-PCR and gene expression microarrays. Depletion of UHRF1 rapidly induced genome-wide DNA demethylation in CRC cells. Infinium BeadChip assays and bisulfite pyrosequencing revealed significant demethylation across entire genomic regions, including CpG islands, gene bodies, intergenic regions, and repetitive elements. Despite the substantial demethylation, however, UHRF1 depletion only minimally reversed CpG island hypermethylation-associated gene silencing. By contrast, the combination of UHRF1 depletion and histone deacetylase (HDAC) inhibition reactivated the silenced genes and strongly suppressed CRC cell proliferation. The combination of UHRF1 depletion and HDAC inhibition also induced marked changes in the gene expression profiles such that cell cycle-related genes were strikingly downregulated.

CONCLUSIONS

Our results suggest that (i) maintenance of DNA methylation in CRC cells is highly dependent on UHRF1; (ii) UHRF1 depletion rapidly induces DNA demethylation, though it is insufficient to fully reactivate the silenced genes; and (iii) dual targeting of UHRF1 and HDAC may be an effective new therapeutic strategy.

UHRF1 promotes renal cell carcinoma progression through epigenetic regulation of TXNIP

UHRF1 is an important epigenetic regulator that belongs to the UHRF family. Overexpression of UHRF1 has been found in many kinds of tumors and its overexpression is associated with poor prognosis and short survival in certain cancer types. However, its function in renal cell carcinoma (RCC) is not clear. Here we report that RCC tumor tissues had obviously higher UHRF1 expression than normal renal tissues. Downregulation of UHRF1 by siRNA or shRNA in RCC cell lines resulted in decreased cell viability, inhibited cell migration and invasion, and increased apoptosis. UHRF1 knockdown RCC xenografts also resulted in obviously inhibited tumor growth in vivo. After downregulation of UHRF1 in RCC cells, the expression of TXNIP was upregulated. In addition, after UHRF1 and TXNIP were simultaneously downregulated, cell viability and cell invasion increased, whereas cell apoptosis decreased compared with UHRF1 single downregulated cells. We also showed that UHRF1 could recruit HDAC1 to the TXNIP promoter and mediate the deacetylation of histone H3K9, resulting in the inhibition of TXNIP expression. Our results confirm that UHRF1 has oncogenic function in RCC and UHRF1 may promote tumor progression through epigenetic regulation of TXNIP. UHRF1 might be used as a therapeutic target for RCC treatment.

Epigenetic mechanism and target therapy of UHRF1 protein complex in malignancies

Ubiquitin-like with plant homeodomain and really interesting new gene finger domains 1 (UHRF1) functions as an epigenetic regulator recruiting PCNA, DNMT1, histone deacetylase 1, G9a, SuV39H, herpes virus-associated ubiquitin-specific protease, and Tat-interactive protein by multiple corresponding domains of DNA and H3 to maintain DNA methylation and histone modifications. Overexpression of UHRF1 has been found as a potential biomarker in various cancers resulting in either DNA hypermethylation or global DNA hypo-methylation, which participates in the occurrence, progression, and invasion of cancer. The role of UHRF1 in the reciprocal interaction between DNA methylation and histone modifications, the dynamic structural transformation of UHRF1 protein within epigenetic code replication machinery in epigenetic regulations, as well as modifications during cell cycle and chemotherapy targeting UHRF1 are evaluated in this study.

Thymoquinone challenges UHRF1 to commit auto-ubiquitination: a key event for apoptosis induction in cancer cells

Down-regulation of UHRF1 (Ubiquitin-like containing PHD and Ring Finger 1) in Jurkat cells, induced by natural anticancer compounds such as thymoquinone, allows re-expression of tumor suppressor genes such as p73 and p16^INK4A . In order to decipher the mechanisms of UHRF1 down-regulation, we investigated the kinetic of expression of HAUSP (herpes virus-associated ubiquitin-specific protease), UHRF1, cleaved caspase-3 and p73 in Jurkat cells treated with thymoquinone. We found that thymoquinone induced degradation of UHRF1, correlated with a sharp decrease in HAUSP and an increase in cleaved caspase-3 and p73. UHRF1 concomitantly underwent a rapid ubiquitination in response to thymoquinone and this effect was not observed in the cells expressing mutant UHRF1 RING domain, suggesting that UHRF1 commits an auto-ubiquitination through its RING domain in response to thymoquinone treatment. Exposure of cells to Z-DEVD, an inhibitor of caspase-3 markedly reduced the thymoquinone-induced down-regulation of UHRF1, while proteosomal inhibitor MG132 had no such effect. The present findings indicate that thymoquinone induces in cancer cells a fast UHRF1 auto-ubiquitination through its RING domain associated with HAUSP down-regulation. They further suggest that thymoquinone-induced UHRF1 auto-ubiquitination followed by its degradation is a key event in inducing apoptosis through a proteasome-independent mechanism.

Targeting the SET and RING-associated (SRA) domain of ubiquitin-like, PHD and ring finger-containing 1 (UHRF1) for anti-cancer drug development

Ubiquitin-like containing PHD Ring Finger 1 (UHRF1) is a multi-domain protein with a methyl-DNA binding SRA (SET and RING-associated) domain, required for maintenance DNA methylation mediated by DNMT1. Primarily expressed in proliferating cells, UHRF1 is a cell-cycle regulated protein that is required for S phase entry. Furthermore, UHRF1 participates in transcriptional gene regulation by connecting DNA methylation to histone modifications. Upregulation of UHRF1 may serve as a biomarker for a variety of cancers; including breast, gastric, prostate, lung and colorectal carcinoma. To this end, overexpression of UHRF1 promotes cancer metastasis by triggering aberrant patterns of DNA methylation, and subsequently, silencing tumor suppressor genes. Various small molecule effectors of UHRF1 have been reported in the literature, although the mechanism of action may not be fully characterized. Small molecules that potentially bind to the SRA domain may affect the ability of UHRF1 to bind hemimethylated DNA; thereby reducing aberrant DNA methylation. Therefore, in a subset of cancers, small molecule UHRF1 inhibitors may restore normal gene expression and serve as useful anti-cancer therapeutics.

Functional dissection of the role of UHRF1 in the regulation of retinoblastoma methylome

UHRF1 (ubiquitin-like with PHD and RING finger domains 1) is a critical regulator for DNA methylation, and its frequent overexpression in human cancers has been associated with tumor-promoting effects. However, whether the overexpressed UHRF1 contributes to the establishment and maintenance of tumor methylomes and whether this process can affect the tumorigenesis remain unclear. In this study, we show that UHRF1 is highly expressed in retinoblastoma, and genomes of human primary retinoblastoma and cell lines have differential DNA methylation patterns compared with those of normal retina, characterized by lower global methylation and higher promoter methylation of tumor suppressors. However, our genome-wide DNA methylation study uncovers that UHRF1 down-modulation in retinoblastoma cells exerts minor effects on the existing methylation patterns at both bulk genome and individual gene loci, suggesting that retinoblastoma methylome is primarily maintained by other mechanisms. Furthermore, using two murine retinoblastoma models, we found that high UHRF1 expression does not alter global methylation levels in both premalignant neonatal retina and retinoblastoma tumors, implying that DNA hypomethylation may not be an early mechanism driving retinoblastoma tumorigenesis unlike what has been proposed for other types of cancer. These results suggest that tumor-promoting functions of UHRF1 in retinoblastoma are largely independent of its role in DNA methylation.

LINE-1 hypomethylation is inversely correlated with UHRF1 overexpression in gastric cancer

DNA methylation is an important epigenetic modification that alters gene expression; DNA hypomethylation contributes to tumorigenesis through multiple processes. In the present study, the methylation of long interspersed element-1 (LINE-1) in 95 gastric cancer (GC) tissues and matched adjacent normal tissues was investigated by pyrosequencing. LINE-1 methylation was compared with the expression of ubiquitin-like with PHD and ring-finger protein 1 (UHRF1), an essential regulator of DNA methylation, using reverse transcription-quantitative polymerase chain reaction. Significant hypomethylation of LINE-1 and overexpression of UHRF1 were observed in GC tissues compared with the matched controls (P<0.001 and P=0.001, respectively). LINE-1 hypomethylation was inversely correlated with UHRF1 overexpression in GC tissues (r=-0.026, P=0.028). In addition, LINE-1 hypomethylation in GC was significantly associated with Lauren's histological classification, tumor differentiation and background intestinal metaplasia (P=0.014, P=0.042 and P=0.034, respectively). These results suggest that LINE-1 hypomethylation may be a potential biomarker for GC and it is indirectly regulated by UHRF1 overexpression.

UHRF1 is an Independent Prognostic Factor and a Potential Therapeutic Target of Esophageal Squamous Cell Carcinoma

Purpose: Ubiquitin-like with plant homeodomain and ring-finger domains 1 (UHRF1) plays an essential role in DNA methylation, and the overexpression of UHRF1 is associated with poor prognosis in various cancers. Esophageal squamous cell carcinoma (ESCC) accounts for approximately 90% of esophageal cancer cases in China, but the five-year survival rate for patients is less than 10% due to limited clinical approaches for early diagnosis and treatment. The present research aimed to investigate the expression of UHRF1 in ESCC and its biological role in ESCC development. Methods: UHRF1 expression in ESCC and normal esophageal tissues was examined using immunohistochemical staining, followed by analysis of the correlation between UHRF1 expression and clinical features. In addition, the effects of lentivirus-mediated RNA interference of UHRF1 on global DNA methylation, cell proliferation, cell cycle progression and apoptosis and were investigated in ESCC cells. Results: UHRF1 was overexpressed in ESCC tissues and was an independent prognostic factor for ESCC patients. In ESCC cells, knockdown of UHRF1 caused global DNA hypomethylation, inhibited cell proliferation and induced apoptosis. Furthermore, UHRF1 depletion induced cell cycle arrest at the G2/M phase, accompanied by activation of Wee1 and DNA damage response pathway. Conclusions: Our findings identify UHRF1 as a promising prognostic marker for ESCC and suggest that UHRF1 may be a potential therapy target for ESCC patients with elevated UHRF1 expression.

The epigenetic integrator UHRF1: on the road to become a universal biomarker for cancer

Cancer is one of the deadliest diseases in the world causing record number of mortalities in both developed and undeveloped countries. Despite a lot of advances and breakthroughs in the field of oncology still, it is very hard to diagnose and treat the cancers at early stages. Here in this review we analyze the potential of Ubiquitin-like containing PHD and Ring Finger domain 1 (UHRF1) as a universal biomarker for cancers. UHRF1 is an important epigenetic regulator maintaining DNA methylation and histone code in the cell. It is highly expressed in a variety of cancers and is a well-known oncogene that can disrupt the epigenetic code and override the senescence machinery. Many studies have validated UHRF1 as a powerful diagnostic and prognostic tool to differentially diagnose cancer, predict the therapeutic response and assess the risk of tumor progression and recurrence. Highly sensitive, non-invasive and cost effective approaches are therefore needed to assess the level of UHRF1 in patients, which can be deployed in diagnostic laboratories to detect cancer and monitor disease progression.

Globular adiponectin inhibits leptin-stimulated esophageal adenocarcinoma cell proliferation via adiponectin receptor 2-mediated suppression of UHRF1

Esophageal adenocarcinoma (EAC) is one of the most common malignancies in the world which is associated the increased prevalence of obesity. In the context of obesity, leptin can directly contribute to progression of EAC. Adiponectin inhibits leptin-induced oncogenic signaling in EAC cells. However, the exact molecular mechanisms linking obesity, adipokines, and EAC remain far from completely understood. In the present study, we tested the role of ubiquitin-like with PHD and ring finger domains 1 (UHRF1) in adiponectin-induced protective effects against leptin-induced EAC cell proliferation. We found that globular adiponectin (gAD) significantly inhibited leptin-induced increase of cell proliferation and decrease of apoptosis in OE 19 cells. Moreover, leptin-induced increase of UHRF1 expression was suppressed by gAD. Compared with normal controls, UHRF1 expression was markedly increased in EAC tissues and cell lines. Silence of UHRF1 increased the expression of cleaved caspase 3 and 9 and Bax, reduced the expression of Bcl-2, promoted apoptosis, and inhibited cell proliferation in OE 19 cells. Overexpression of UHRF1 significantly blocked gAD-induced decrease of cell proliferation and increase of apoptosis in leptin-treated cells. Silence of adiponectin receptor 1/2 (AdipoR1/2) could inhibit gAD-induced decrease of cell proliferation and increase of apoptosis in leptin-treated cells. Silence of AdipoR2, but not AdipoR1, suppressed gAD-induced decrease of UHRF1 expression in leptin-treated cells. The results indicated that gAD inhibited the prooncogenic effects of leptin via AdipoR2-mediated suppression of UHRF1. Our study provides novel insights into the role of UHRF1 in the development of EAC and the mechanism of antitumor effect of gAD.