Uridine-cytidine Kinase 2 Research Articles

UCK2 promotes intrahepatic cholangiocarcinoma progression and desensitizes cisplatin treatment by PI3K/AKT/mTOR/autophagic axis

Intrahepatic cholangiocarcinoma (iCCA) is a highly aggressive tumor with extremely poor prognosis due to the low resection rate, high recurrence rate and drug resistance. Uridine-cytidine kinase 2 (UCK2) is proved to promote progression and drug resistance of various carcinomas by regulating pyrimidine metabolism. However, the role of UCK2 in progression and drug resistance of iCCA was largely unclear. Gene expression matrices were obtained from public database and were verified by qRT-PCR using tumor sample from Sun Yat-sen University Cancer Center. Knockdown and overexpression of UCK2 were used to evaluate the effects of UCK2 on carcinogenesis and cisplatin response in iCCA. CCK8-kit assays and plate clone formation assays were performed to detect the effect of UCK2 on proliferative activity of tumor cells. Western blotting was performed to investigate protein level of UCK2 and the relevant biomarkers of PI3K/AKT/mTOR/autophagic axis. Cell migration and invasion were assessed by using wound-healing and transwell assays. UCK2 expression was detected elevated in iCCA tissues compared with adjacent normal tissues. Biologically, overexpression of UCK2 can promote proliferation of iCCA cells, and desensitizes iCCA to cisplatin in both in vivo and in vitro models. Mechanistically, UCK2 promote iCCA progression and cisplatin resistance through inhibition of autophagy by activating the PI3K/AKT/mTOR signaling pathway. Clinically, higher UCK2 expression in iCCA tumor was associated with aggressive tumor features, poorer survival and lower sensitivity of chemotherapy. UCK2 promotes iCCA progression and desensitizes cisplatin treatment by regulating PI3K/AKT/mTOR/autophagic axis. UCK2 exhibited potential as a biomarker in predicting prognosis and drug sensitivity of iCCA patients.

CircUCK2 promotes hepatocellular carcinoma development by upregulating UCK2 in a mir-149-5p-dependent manner

BackgroundCircular RNAs (circRNAs) participate in the regulation of Hepatocellular Carcinoma (HCC) progression. The objective of this study was to explore the function and mechanism of circUCK2 in HCC development.MethodsThe RNA levels of circUCK2, miR-149-5p and uridine–cytidine kinase 2 (UCK2) were examined by quantitative real-time polymerase chain reaction (qRT-PCR). EdU incorporation assay and colony formation assay were respectively performed to analyze cell proliferation and colony formation. Wound healing assay and transwell assay were conducted for cell migration and invasion. Flow cytometry was used for cell apoptosis analysis. Western blot assay was conducted to determine the protein levels of E-cadherin, N-cadherin, matrix metallopeptidase 9 (MMP-9) and UCK2. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay were conducted to confirm the interaction between miR-149-5p and circUCK2 or UCK2. The xenograft model was established to explore the role of circUCK2 in tumor growth in vivo.ResultsCircUCK2 level was elevated in HCC, and circUCK2 depletion suppressed HCC cell proliferation, colony formation, migration and invasion and accelerated cell apoptosis. Mechanistically, circUCK2 could positively modulate UCK2 expression by interacting with miR-149-5p. Furthermore, the repressive effects of circUCK2 knockdown on the malignant behaviors of HCC cells were alleviated by UCK2 overexpression or miR-149-5p inhibition. The promoting effects of circUCK2 overexpression on HCC cell malignancy were alleviated by UCK2 silencing or miR-149-5p introduction. Additionally, circUCK2 knockdown hampered tumor growth in vivo.ConclusionCircUCK2 contributed to HCC malignant progression in vitro and in vivo via targeting miR-149-5p/UCK2 axis, demonstrating that circUCK2 might be a novel therapeutic target for HCC.

Reprogramming of pyrimidine nucleotide metabolism supports vigorous cell proliferation of normal and malignant T cells

AbstractAdult T-cell leukemia/lymphoma (ATL) is triggered by infection with human T-cell lymphotropic virus-1 (HTLV-1). Here, we describe the reprogramming of pyrimidine biosynthesis in both normal T cells and ATL cells through regulation of uridine-cytidine kinase 2 (UCK2), which supports vigorous proliferation. UCK2 catalyzes the monophosphorylation of cytidine/uridine and their analogues during pyrimidine biosynthesis and drug metabolism. We found that UCK2 was overexpressed aberrantly in HTLV-1–infected T cells but not in normal T cells. T-cell activation via T-cell receptor (TCR) signaling induced expression of UCK2 in normal T cells. Somatic alterations and epigenetic modifications in ATL cells activate TCR signaling. Therefore, we believe that expression of UCK2 in HTLV-1–infected cells is induced by dysregulated TCR signaling. Recently, we established azacitidine-resistant (AZA-R) cells showing absent expression of UCK2. AZA-R cells proliferated normally in vitro, whereas UCK2 knockdown inhibited ATL cell growth. Although uridine and cytidine accumulated in AZA-R cells, possibly because of dysfunction of pyrimidine salvage biosynthesis induced by loss of UCK2 expression, the amount of UTP and CTP was almost the same as in parental cells. Furthermore, AZA-R cells were more susceptible to an inhibitor of dihydroorotic acid dehydrogenase, which performs the rate-limiting enzyme of de novo pyrimidine nucleotide biosynthesis, and more resistant to dipyridamole, an inhibitor of pyrimidine salvage biosynthesis, suggesting that AZA-R cells adapt to UCK2 loss by increasing de novo pyrimidine nucleotide biosynthesis. Taken together, the data suggest that fine-tuning pyrimidine biosynthesis supports vigorous cell proliferation of both normal T cells and ATL cells.

The Underling Mechanisms Exploration of Rubia cordifolia L. Extract Against Rheumatoid Arthritis by Integrating Network Pharmacology and Metabolomics.

Rubia cordifolia L. (RC) is a classic herbal medicine for the treatment of rheumatoid arthritis (RA) and has been used since ancient times. The ethanol extract of Rubia cordifolia L. (RCE) showed obvious anti-RA effects in our previous study. However, further potential mechanisms require more exploration. We aimed to investigate the mechanism of RCE for the treatment of RA by integrating metabolomics and network pharmacology in this study. An adjuvant-induced arthritis (AIA) rat model was established, and we evaluated the therapeutic effects of RCE. Metabolomics of serum and urine was used to identify the differential metabolites. Network pharmacology was applied to determine the key metabolites and potential targets. Finally, the potential targets and compounds of RCE were verified by molecular docking. The results indicated that RCE suppressed foot swelling and alleviated joint damage and also had anti-inflammatory properties by inhibiting the expressions of tumor necrosis factor (TNF)-α, Interleukin (IL)-1β, prostaglandin E2 (PGE2), and P65. Ten and seven differential metabolites were found in the serum and urine, respectively, of rats. Six key targets, ie, phospholipase A2 group IIA (PLA2G2A), phospholipase A2 group X (PLA2G10), cytidine deaminase (CDA), uridine-cytidine kinase 2 (UCK2), charcot-leyden crystal galectin (CLC), and 5',3'-nucleotidase, mitochondrial (NT5M), were discovered by network pharmacology and metabolite analysis and were found to be related to glycerophospholipid metabolism and pyrimidine metabolism. Molecular docking confirmed that the favorable compounds showed affinities with the key targets, including alizarin, 6-hydroxyrubiadin, ruberythric acid, and munjistin. This study revealed the underlying mechanisms of RCE and provided evidence that will allow researchers to further investigate the functions and components of RCE against RA.

UCK2 promotes the proliferation, migration, and invasion of trophoblast cells in preeclampsia by activating the STAT3 pathway

Background: Preeclampsia (PE), characterized by hypertension and proteinuria, leads to serious maternal and infant complications. Uridine-cytidine kinase 2 (UCK2) belongs to the UCK family, a class of enzymes that catalyzes the conversion of uridine and cytidine to monophosphate form. However, the role of UCK2 in PE has not been reported. Methods: The expression of UCK2 was detected in the placenta of PE patients and N(ω)-nitro-L-arginine methyl esterinduced PE mouse model. Through forced up-regulation or down-regulation of UCK2 in vitro, we examined the effects of UCK2 on the proliferation, apoptosis, migration, and invasion of trophoblast cells. Stattic, the inhibitor of STAT3 pathway, was used to investigate whether the STAT3 pathway mediates the biological function of UCK2 in trophoblast cells. Results: The present study found that UCK2 showed low expression in the placenta of PE patients and PE mouse model. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and flow cytometry assays verified that up-regulation of UCK2 promoted the proliferation of trophoblast cells, while the silence of UCK2 suppressed cell proliferation. Besides, flow cytometry and TdT-mediated dUTP Nick-End Labeling assays demonstrated that knockdown of UCK2 resulted in apoptosis of trophoblast cells. The wound healing and transwell assays showed that the migration and invasion activities of the trophoblast cells were facilitated by the overexpression of UCK2 and were blocked by the silence of UCK2. Furthermore, the expression of phosphorylated STAT3 was increased with the upregulation of UCK2 and decreased with the inhibition of UCK2. When the STAT3 pathway was blocked by its inhibitor stattic, the promotion effects of UCK2 on trophoblast cells were suppressed. Conclusion: UCK2 promotes the proliferation, migration, and invasion of trophoblast cells, and these effects may be partly mediated by the activation of the STAT3 pathway.

Targeting uridine–cytidine kinase 2 induced cell cycle arrest through dual mechanism and could improve the immune response of hepatocellular carcinoma

BackgroundPyrimidine metabolism is critical for tumour progression. Uridine–cytidine kinase 2 (UCK2), a key regulator of pyrimidine metabolism, is elevated during hepatocellular carcinoma (HCC) development and exhibits carcinogenic effects. However, the key mechanism of UCK2 promoting HCC and the therapeutic value of UCK2 are still undefined. The aim of this study is to investigate the potential of UCK2 as a therapeutic target for HCC.MethodsGene expression matrices were obtained from public databases. RNA-seq, co-immunoprecipitation and RNA-binding protein immunoprecipitation were used to determine the mechanism of UCK2 promoting HCC. Immune cell infiltration level and immune-related functional scores were evaluated to assess the link between tumour microenvironment and UCK2.ResultsIn HCC, the expression of UCK2 was upregulated in part by TGFβ1 stimulation. UCK2 promoted cell cycle progression of HCC by preventing the degradation of mTOR protein and maintaining the stability of PDPK1 mRNA. We also identified UCK2 as a novel RNA-binding protein. Downregulation of UCK2 induced cell cycle arrest and activated the TNFα/NFκB signalling pathway-related senescence-associated secretory phenotype to modify the tumour microenvironment. Additionally, UCK2 was a biomarker of the immunosuppressive microenvironment. Downregulated UCK2 induced a secretory phenotype, which could improve the microenvironment, and decreased UCK2 remodelling metabolism could lower the resistance of tumour cells to T-cell-mediated killing.ConclusionsTargeting UCK2 inhibits HCC progression and could improve the response to immunotherapy in patients with HCC. Our study suggests that UCK2 could be an ideal target for HCC.

Identifying Mechanisms of Resistance to DHODH Inhibition in Cancer

All transcriptionally active and rapidly dividing cells require high amounts of pyrimidines for DNA replication and repair and RNA synthesis. The only two known mechanisms by which cells can acquire pyrimidines are the de novo pyrimidine biosynthesis pathway and the pyrimidine salvage pathway. The rate-limiting enzyme in de novo synthesis is dihydroorotate dehydrogenase (DHODH), a critical metabolic enzyme that converts dihydroorotate (DHO) to orotate, which is then converted to the pyrimidine precursor uridine monophosphate (UMP). The rate-limiting enzyme in the salvage pathway is uridine-cytidine kinase 2 (UCK2), a ribonucleoside kinase that converts uridine to UMP and cytidine to cytidine monophosphate (CMP). Under physiologic conditions, salvage pathway substrates are limiting, and many cancer types, most notably acute myeloid leukemia (AML), are highly dependent on DHODH activity for proliferation and survival. Based on these observations, several DHODH inhibitors have been developed as anti-cancer therapeutics and have been tested clinically. Unfortunately, to date, these drugs have failed to show significant anti-cancer activity in early-phase clinical trials. In order to understand how leukemia cells that are highly sensitive to DHODH inhibitors can bypass their dependence on DHODH activity, we conducted positive-selection whole-genome CRISPR-activation drug resistance screens in TF-1 human AML cells using BAY 2402234, a highly potent and highly specific DHODH inhibitor. In preliminary studies, we found that 1 nM BAY 2402234 fully inhibits TF-1 cells whereas TF-1 cells that overexpress high levels of DHODH require 50 nM BAY 2402234 to achieve the same effect. Importantly, the effects of 1 nM and 50 nM BAY 2402234 are fully rescued by addition of uridine to the culture media, demonstrating that the anti-leukemic activity of BAY 2402234 is on-target at both drug doses. To perform the drug resistance screens, we stably expressed nuclease-deactivated Cas9 fused to a transcriptional activator (dCas9-VP64) in TF-1 cells and then infected the cells with the human whole-genome Calabrese sgRNA lentiviral library. We then passaged the cells in media containing vehicle control (DMSO), 1 nM or 50 nM BAY 2402234 for 18 days, collecting cells on day 0 and day 18 of drug treatment. Genomic DNA was then extracted and was subjected to next generation sequencing to assess the relative abundance of each sgRNA in each sample. We reasoned that activation of genes that enhance de novo pathway activity at the level of, or downstream of, DHODH would promote resistance to 1 nM BAY 2402234 but not 50 nM BAY 2402234, whereas activation of genes that act through de novo pathway-independent mechanisms would promote resistance to both 1 nM and 50 nM BAY 2402234. As predicted, sgRNAs targeting DHODH conferred resistance to 1 nM but not 50 nM BAY 2402234 whereas sgRNAs targeting UCK2 conferred resistance to both 1 and 50 nM BAY 2402234 (Figure 1). A number of other known salvage pathway genes scored in both screens, including uracil phosphoribosyltransferase (UPRT) and the nucleoside transporters SLC4A1 and SLC29A1. Unexpectedly, the screens also identified carbamoyl-phosphate synthetase 2/aspartate transcarbamoylase/dihydroorotase (CAD) as a potential mechanism of resistance to DHODH inhibition. CAD is a trifunctional multi-domain enzyme that acts upstream of DHODH, catalyzing the first three steps in de novopyrimidine biosynthesis. How upregulation of CAD activity can bypass the requirement for DHODH activity is not clear, although CAD is a very large enzyme complex about which very little is known besides its de novo pyrimidine synthesis activity. The screens also identified several genes that are not known to play a role in pyrimidine metabolism as potential resistance mechanisms. These include the serine-threonine kinase MARK3, the serine-threonine phosphatase CTDSPL2, and the RNA-binding protein NANOS2. Finally, the screens identified several genes whose upregulation sensitized cells to BAY 2402234, including the urokinase receptor PLAUR, the adaptor protein BCAR3, the scaffold protein SHOC2, and the deoxynucleoside phosphohydrolase SAMHD1. Studies are currently underway to validate the results of the CRISPRa screens and elucidate the mechanisms by which the candidate resistance genes help cells to bypass their requirement for DHODH activity. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

P1301: BIOLOGICAL SIGNIFICANCE OF UCK2 IN HTLV-1-INFECTED CELLS IN ATL LEUKEMOGENESIS AND ACQUIRED RESISTANCE TO AZACITIDINE

Background: Adult T-cell leukemia-lymphoma (ATL) is an aggressive hematological malignancy of CD4+ T-cells transformed by human T-cell lymphotropic virus-1 (HTLV-1). We have reported that regional DNA hypermethylation in HTLV-1-infected T-cells reflects the disease status of ATL and the anti-ATL effects of DNA demethylating agents, azacitidine (AZA) and decitabine (Blood 2020, 136: 871-884). We recently generated AZA-resistant (AZA-R) cells from ATL cell lines via long-term drug exposure and found down-regulation of uridine cytidine kinase2 (UCK2) correlated with lower susceptibility to AZA (Int J Cancer 2022, 150: 1184-1197). UCK1 and UCK2 are involved in mono-phosphorylation of uridine and cytidine in pyrimidine nucleotide biosynthesis. Both proteins also catalyze mono-phosphorylation of AZA. Overexpression of UCK2 has been observed in several types of solid tumor tissues. Aims: Here, we aimed to understand the role of UCK2 in HTLV-1-infected cells during multi-step carcinogenesis of ATL and the biological significance of inactivation of UCK2 in AZA-R cells. Methods: All studies using human samples were performed in accordance with the guidelines set out in the Declaration of Helsinki and were approved by the institutional review board at Saga University (2018-03-02). Peripheral blood mononuclear cells (PBMCs) were isolated from peripheral blood samples from healthy volunteers, HTLV-1 carriers and patients with ATL. ATL cell lines were cultured in RPMI-1640 medium containing 10% FBS. Results: We found that UCK2 gene expression was higher in HTLV-1-infected T-cells than in normal T-cells using the gene expression datasets GSE55851 and GSE33615. UCK2 protein expression was increased in HTLV-1-infected T-cells (CADM1+ cells) isolated from patients with ATL compared with uninfected T-cells (Fig. A). We also found UCK2 gene expression was upregulated via activation of T-cell receptor (TCR) signaling pathway in normal CD4+ T-cells (Fig. B). Somatic alterations and epigenetic modifications activating TCR signaling have been identified in ATL cells. Therefore, we think UCK2 protein is overexpressed through dysregulated TCR signaling in HTLV-1-infected cells during ATL leukemogenesis. We have successfully established AZA-R cell lines, whose UCK2 expression was lost or decreased. Although they proliferated normally in vitro, the knockdown of UCK2 dramatically suppressed cell growth of ATL cell lines (Fig. C). Since UCK2 is involved in pyrimidine nucleotide biosynthesis, we then performed metabolome analysis in AZA-R cells. Although uridine and cytidine were accumulated in AZA-R cells, possibly due to loss of UCK2, the amount of UTP and CTP was almost same with parental cells. On the other hands, dihydroorotic acid (DHO) was decreased and orotate was increased in AZA-R cells (Fig. D). DHODH catalyzes the oxidation of DHO to orotic acid and is a rate-limiting enzyme in de novo pyrimidine nucleotide synthesis. AZA-R cells were more susceptible to BAY2402234, a DHODH inhibitor (Fig. E), indicating the activation of pyrimidine de novo synthesis in AZA-R cells. Image:Summary/Conclusion: Taken together, we think UCK2 supports the vigorous cell proliferation not only in normal TCR-stimulated T-cells but also in HTLV-1-infected cells. Inactivation of UCK2 makes cells resistant to AZA but suppresses the cell growth possibly due to the pyrimidine nucleotide starvation. AZA-R cells with reduced UCK2 expression proliferate normally in vitro by the activation of pyrimidine de novo synthesis.

The Metabolic and Non-Metabolic Roles of UCK2 in Tumor Progression.

Enhanced nucleoside metabolism is one of the hallmarks of cancer. Uridine-cytidine kinase 2 (UCK2) is a rate-limiting enzyme of the pyrimidine salvage synthesis pathway to phosphorylate uridine and cytidine to uridine monophosphate (UMP) and cytidine monophosphate (CMP), respectively. Recent studies have shown that UCK2 is overexpressed in many types of solid and hematopoietic cancers, closely associates with poor prognosis, and promotes cell proliferation and migration in lung cancer and HCCs. Although UCK2 is thought to catalyze sufficient nucleotide building blocks to support the rapid proliferation of tumor cells, we and other groups have recently demonstrated that UCK2 may play a tumor-promoting role in a catalytic independent manner by activating oncogenic signaling pathways, such as STAT3 and EGFR-AKT. By harnessing the catalytic activity of UCK2, several cytotoxic ribonucleoside analogs, such as TAS-106 and RX-3117, have been developed for UCK2-mediated cancer chemotherapy. Moreover, we have demonstrated that the concurrent targeting of the catalytic dependent and independent features of UCK2 could synergistically inhibit tumor growth. These findings suggest that UCK2 may serve as a potential therapeutic target for cancer treatment. In this mini-review, we introduced the genomic localization and protein structure of UCK2, described the role of UCK2 in tumor development, discussed the application of UCK2 in anti-tumor treatment, and proposed concurrent targeting of the catalytic and non-catalytic roles of UCK2 as a potential therapeutic strategy for cancer treatment.

Adult T-cell leukemia-lymphoma acquires resistance to DNA demethylating agents through dysregulation of enzymes involved in pyrimidine metabolism.

Adult T‐cell leukemia‐lymphoma (ATL) is an aggressive neoplasm derived from T‐cells transformed by human T‐cell lymphotropic virus‐1 (HTLV‐1). Recently, we reported that regional DNA hypermethylation in HTLV‐1‐infected T‐cells reflects the disease status of ATL and the anti‐ATL effects of DNA demethylating agents, including azacitidine (AZA), decitabine (DAC) and a new DAC prodrug, OR‐2100 (OR21), which we developed. Here, to better understand the mechanisms underlying drug resistance, we generated AZA‐, DAC‐ and OR21‐resistant (AZA‐R, DAC‐R and OR21‐R, respectively) cells from the ATL cell line TL‐Om1 and the HTLV‐1‐infected cell line MT‐2 via long‐term drug exposure. The efficacy of OR21 was almost the same as that of DAC, indicating that the pharmacodynamics of OR21 were due to release of DAC from OR21. Resistant cells did not show cellular responses observed in parental cells induced by treatment with drugs, including growth suppression, depletion of DNA methyltransferase DNMT1 and DNA hypomethylation. We also found that reduced expression of deoxycytidine kinase (DCK) correlated with lower susceptibility to DAC/OR21 and that reduced expression of uridine cytidine kinase2 (UCK2) correlated with reduced susceptibility to AZA. DCK and UCK2 catalyze phosphorylation of DAC and AZA, respectively; reconstitution of expression reversed the resistant phenotypes. A large homozygous deletion in DCK and a homozygous splice donor site mutation in UCK2 were identified in DAC‐R TL‐Om1 and AZA‐R TL‐Om1, respectively. Both genomic mutations might lead to loss of protein expression. Thus, inactivation of UCK2 and DCK might be a putative cause of phenotypes that are resistant to AZA and DAC/OR21, respectively.

A Preliminary Study on the Impact of UCK2 Knockdown in DLD-1 Colorectal Cells Treated with DHODH Inhibitor

Brequinar sodium (BQR) is a well-studied inhibitor of the dihydroorotate dehydrogenase (DHODH) enzyme. Both the DHODH and uridine-cytidine kinase 2 (UCK2) enzymes have been reported to be over-expressed in cancer cells to maintain the cells high demand for DNA and RNA for their proliferation. In this study, we aim to further sensitize cells to the effects of BQR by knocking down the UCK2 activity. In DLD-1 UCK2 knockdown cells, no change in the sensitivity of cells to BQR was observed. Uridine is known to reverse the anti-proliferative effect of DHODH inhibitors via the salvage pathway. We observed abrogation of approximately 30% of the uridine reversal effect in UCK2 knockdown cells compared to the wild type cells. Our finding indicates that the loss of UCK2 activity in the salvage pathway did not enhance the BQR-mediated cell proliferation inhibition but it abrogates the uridine reversal in the cells.

METTL3-induced UCK2 m6A hypermethylation promotes melanoma cancer cell metastasis via the WNT/β-catenin pathway.

BackgroundMelanoma is a highly aggressive, malignant skin tumor with a statistically high mortality rate. N6-methyladenosine (m6A) modification is involved in a variety of biological processes, including tumorigenesis. m6A modifications regulate the fate and functions of RNA, such as mRNA stability, nuclear processing, transport, localization, translation, primary microRNA (miRNA) processing, and RNA-protein interactions. Several members (including METTL3, METTL14, FTO, ALKBH5, and YTHDF2) are actively involved in a variety of human cancers. However, the basic mechanism of the involvement of uridine cytidine kinase 2 (UCK2) in melanoma metastasis has not been studied. UCK2 is upregulated in a variety of malignancies. However, the complex molecular mechanisms and therapeutic effects of UCK2 in melanoma remain unclear.MethodsThe expression of UCK2 was evaluated by qRT-PCR. The effects of UCK2 on the biological characteristics of PC cells were investigated on the basis of loss-of-function analyses. Immunoprecipitation-qPCR (MeRIP-qPCR) was performed to identify the m6A targeted effect of UCK2 in melanoma cancer.ResultsBased on the bioinformatics analysis in this study, up-regulation of UCK2 could be essential in melanoma cancer, and associated with poor survival. Furthermore, the m6A modification regulated by METTL3 led to UCK2 increased messenger RNA (mRNA) stability in melanoma cancer. Functional and mechanistic experiments indicated that UCK2 enhanced the metastasis of melanoma cancer cells through the WNT/β-catenin pathway.ConclusionIn this study, we found that m6A-METTL3 axis induced abnormal UCK2 expression plays a role in melanoma metastasis by enhancing the Wnt/β-catenin pathway, which may provide new clues for melanoma metastasis. It also provides a potential target for the prevention and treatment of melanoma.

RX-3117, a Novel Nucleoside Analog Targeting UCK2 Is Active Alone and Synergistic with Ibrutinib and Bendamustine in ABC and DH/DP- Diffuse Large B-Cell Lymphoma

IntroductionRX-3117 is a prodrug activated by uridine-cytidine kinase 2 (UCK-2) which is found predominantly in human cancer cells including non-Hodgkin lymphoma (NHL). Once activated by UCK2, RX-3117 inhibits DNA and RNA synthesis leading to apoptosis. Despite current approved therapies for DLBCL, a significant number of patients fail frontline and subsequent therapies. This is more so for activated B-cell (ABC), double-hit/double protein DLBCL (DH/DP-DLBCL) and Transform Follicular lymphoma. We hypothesized that combining RX-3117 with bendamustine or ibrutinib would be synergistic and a rational means to inhibit proliferation and enhance apoptosis in aggressive types of DLBCL.MethodsU2932, VAL, OCI-Ly10 and TMD8 DLBCL cells were assessed for UCK-2 expression by Western blotting. Cellular cytotoxicity assays were performed with RX-3117, ibrutinib, bendamustine and their combinations using a CellTiter 96 Cell Proliferation Assay (Promega, Madison, WI) and combination-index (CI) calculated by the principle of Chou and Talalay. Apoptosis was detected by Western blotting for PARP cleavage and flow cytometry. Cellular signaling pathways were investigated by Western blotting analyses. Finally, to establish safety and efficacy, we are evaluating above drug combinations in a U2932 DP-DLBCL SCID mouse xenograft model.ResultsThe anti-proliferative activity of RX-3117 correlates with increased UCK-2 expression and activity. In DLBCL cell lines UCK-2 is over-expressed relative to normal B cells indicating a significant therapeutic index. MTS assays demonstrate single agent differential activity for RX-3117, bendamustine and ibrutinib in the 4 DLBCL cell lines respectively. RX-3117 plus bendamustine or ibrutinib were highly synergistic in DLBCL cells. Western blotting showed inhibition of NF-kB expression with RX-3117 plus bendamustine or ibrutinib. This combination also induces apoptosis by increased PARP cleavage. The U2932 mouse xenograft model is ongoing with RX-3117 alone and in combination with bendamustine + rituximab or ibrutinib. Results will be available shortly and presented at the meeting.ConclusionsRX-3117, a novel nucleoside pro-drug activated by high UCK-2 levels in aggressive DLBCL has single agent activity and synergizes with bendamustine and ibrutinib. Novel combination therapies of RX-3117 are warranted in relapsed and refractory DLBCL. DisclosuresLee:Rexahn Pharmaceuticals: Employment, Other: Stock Options. Kim:Rexahn Pharmaceuticals: Employment, Other: Stock Options. Benaim:Rexahn Pharmaceuticals: Employment, Other: Stock Options.

Analysis of m6A RNA Methylation-Related Genes in Liver Hepatocellular Carcinoma and Their Correlation with Survival.

N6-methyladenosine (m6A) modification on RNA plays an important role in tumorigenesis and metastasis, which could change gene expression and even function at multiple levels such as RNA splicing, stability, translocation, and translation. In this study, we aim to conduct a comprehensive analysis on m6A RNA methylation-related genes, including m6A RNA methylation regulators and m6A RNA methylation-modified genes, in liver hepatocellular carcinoma, and their relationship with survival and clinical features. Data, which consist of the expression of widely reported m6A RNA methylation-related genes in liver hepatocellular carcinoma from The Cancer Genome Atlas (TCGA), were analyzed by one-way ANOVA, Univariate Cox regression, a protein–protein interaction network, gene enrichment analysis, feature screening, a risk prognostic model, correlation analysis, and consensus clustering analysis. In total, 405 of the m6A RNA methylation-related genes were found based on one-way ANOVA. Among them, DNA topoisomerase 2-alpha (TOP2A), exodeoxyribonuclease 1 (EXO1), ser-ine/threonine-protein kinase Nek2 (NEK2), baculoviral IAP repeat-containing protein 5 (BIRC5), hyaluronan mediated motility receptor (HMMR), structural maintenance of chromosomes protein 4 (SMC4), bloom syndrome protein (BLM), ca-sein kinase I isoform epsilon (CSNK1E), cytoskeleton-associated protein 5 (CKAP5), and inner centromere protein (INCENP), which were m6A RNA methylation-modified genes, were recognized as the hub genes based on the protein–protein interaction analysis. The risk prognostic model showed that gender, AJCC stage, grade, T, and N were significantly different between the subgroup with the high and low risk groups. The AUC, the evaluation parameter of the prediction model which was built by RandomForest, was 0.7. Furthermore, two subgroups were divided by consensus clustering analysis, in which stage, grade, and T differed. We identified the important genes expressed significantly among two clusters, including uridine-cytidine kinase 2 (UCK2), filensin (BFSP1), tubulin-specific chaperone D (TBCD), histone-lysine N-methyltransferase PRDM16 (PRDM16), phosphorylase b ki-nase regulatory subunit alpha (PHKA2), serine/threonine-protein kinase BRSK2 (BRSK2), Arf-GAP with coiled-coil (ACAP3), general transcription factor 3C polypep-tide 2 (GTF3C2), and guanine nucleotide exchange factor MSS4 (RABIF). In our study, the m6A RNA methylation-related genes in liver hepatocellular carcinoma were analyzed systematically, including the expression, interaction, function, and prognostic values, which provided an important theoretical basis for m6A RNA methylation in liver cancer. The nine important m6A-related genes could be prognostic markers in the survival time of patients.

Non-metabolic role of UCK2 links EGFR-AKT pathway activation to metastasis enhancement in hepatocellular carcinoma

Up-regulation of Uridine-cytidine kinase 2 (UCK2), a rate-limiting enzyme of the pyrimidine salvage pathway, has been suggested in HCC, but the detailed molecular mechanisms and therapic role of UCK2 remain elusive. Bioinformatic analyses revealed that UCK2 might be a key up-regulated metabolic gene in HCCs. The expressional pattern and prognostic value of UCK2 were further examined in a large number of clinical samples. Functional assays based on site-directed mutagenesis showed that UCK2 promoted cell proliferation in a metabolic manner, but non-catalytically facilitates HCC metastasis. Mechanistically, in response to EGF, UCK2 interacted with EGFR to block EGF-induced EGFR ubiquitination and degradation, which resulted in elevated EGFR-AKT pathway activation and metastasis enhancement in HCCs. Concurrent pharmacological targeting on UCK2 and EGFR showed synergistic effects on HCC treatment. This study disclosed the non-metabolic role of UCK2 and suggested the therapeutic potential of concurrent blocking the metabolic and non-metabolic roles of UCK2 in HCC treatment.

Uridine-cytidine kinase 2 (UCK2): A potential diagnostic and prognostic biomarker for lung cancer.

Lung cancer has the highest morbidity and mortality among all cancers. Discovery of early diagnostic and prognostic biomarkers of lung cancer can greatly facilitate the survival rate and reduce its mortality. In our study, by analyzing Gene Expression Omnibus and Oncomine databases, we found a novel potential oncogene uridine‐cytidine kinase 2 (UCK2), which was overexpressed in lung tumor tissues compared to adjacent nontumor tissues or normal lung. Then we confirmed this finding in clinical samples. Specifically, UCK2 was identified as highly expressed in stage IA lung cancer with a high diagnostic accuracy (area under the receiver operating characteristic curve > 0.9). We also found that high UCK2 expression was related to poorer clinicopathological features, such as higher T stage and N stage and higher probability of early recurrence. Furthermore, we found that patients with high UCK2 expression had poorer first progression survival and overall survival than patients with low UCK2 expression. Univariate and multivariate Cox regression analyses showed that UCK2 was an independent risk factor related with worse DFS and OS. By gene set enrichment analysis, tumor‐associated biological processes and signaling pathways were enriched in the UCK2 overexpression group, which indicated that UCK2 might play a vital role in lung cancer. Furthermore, in cytology experiments, we found that knockdown of UCK2 could suppress the proliferation and migration of lung cancer cells. In conclusion, our study indicated that UCK2 might be a potential early diagnostic and prognostic biomarker for lung cancer.

Discovery of small molecule inhibitors of human uridine-cytidine kinase 2 by high-throughput screening.

Clinically relevant inhibitors of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme in mammalian de novo pyrimidine synthesis, have strong antiviral and anticancer activity in vitro. However, they are ineffective in vivo due to efficient uridine salvage by infected or rapidly dividing cells. The pyrimidine salvage enzyme uridine-cytidine kinase 2 (UCK2), a ∼29 kDa protein that forms a tetramer in its active state, is necessary for uridine salvage. Notwithstanding the pharmacological potential of this target, no medicinally tractable inhibitors of the human enzyme have been reported to date. We therefore established and miniaturized an in vitro assay for UCK2 activity and undertook a high-throughput screen against a ∼40,000-compound library to generate drug-like leads. The structures, activities, and modes of inhibition of the most promising hits are described. Notably, our screen yielded non-competitive UCK2 inhibitors which were able to suppress nucleoside salvage in cells both in the presence and absence of DHODH inhibitors.

Abstract 428: Phenotyping pancreatic cancer CTCs as biomarkers for RX-3117 clinical trials

Abstract Background: RX-3117 is an oral, small molecule nucleoside analogue pro-drug being used in combination with nab-paclitaxel in a Ph2 clinical trial for pancreatic cancer. RX-3117 can be transported intracellularly by SLC29A1 (hENT1) and is converted to an active agent by the cancer-enriched enzyme, uridine-cytidine kinase 2 (UCK2) for incorporation into RNA and DNA. This leads to cancer cell apoptosis. We developed an approach to enumerate and phenotype CTCs from pancreatic cancer subjects by quantitative immunofluorescence (QIF) to assess whether CTC numbers, phenotypic features and/or early apoptotic responses to therapy predict or presage clinical response. Methods: QIF staining parameters were developed with cancer cell lines sensitive and resistant to RX-3117 utilizing monoclonal antibodies to hENT1 and UCK2. The staining methods were then applied to CTCs isolated from 10 ml anticoagulated blood by dielectrophoretic (DEP) properties that differentiate cancer cells and normal PBMCs using the ApoStream device (ApoCell, TX). In addition to the drug-related markers, CTCs were stained for a panel of either Epithelial or Mesenchymal markers, CD45 and nuclei (DAPI). Phenotyped CTCs were binned into 6 categories defined by whether they were EPI+/-, EMT+/- or CD45+/-. The percentage of cells in each category also positive for hENT1 or UCK2 was determined as was the mean fluorescence intensity of the marker+ sub-population. In addition, assessment of hENT1 and UCK2 expression was performed by qRT-PCR utilizing mRNA isolated from isolated CTCs, the buffy coat from spun blood and in plasma. Results: In a pilot study, blood was obtained from five subjects with Stage IV pancreatic cancer on various regimens. CTCs were isolated, enumerated and phenotyped. CTC numbers ranged from 100 – 20,000 per ml. The percentages of UCK2+ cells were higher in EPI+/EMT+ subsets than EPI-/EMT- subsets. The percentages of hENT1+ cells were generally low in all the subsets. hENT1 and UCK2 transcripts were observed at acceptable levels in the cell populations, and borderline, but consistent levels in plasma samples. CEACAM5 transcripts were observed only in one CTC and PBMC fraction from one subject. After normalization vs. housekeeping transcripts, a greater than 2-fold increase of UCK2 was observed in three CTC samples compared to PBMC samples. A greater than 2-fold increase of hENT1 was observed in two CTC samples. Conclusion: CTCs from patients with pancreatic cancer can be obtained in numbers suitable for multiparameter phenotyping to identify features that might serve as selective, predictive or prognostic biomarkers in clinical trials. Multiparameter phenotyping of several relevant markers is being performed by quantitative immunofluorescence on CTCs isolated from pancreatic cancer patients in an on-going Ph2 clinical trial of RX-3117 in combination with nab-paclitaxel. Citation Format: Andrew Eisen, DJ Kim, Jie Yang, Weiguo Wu, Darren W. Davis. Phenotyping pancreatic cancer CTCs as biomarkers for RX-3117 clinical trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 428.

Uridine Cytidine Kinase 2 as a Potential Biomarker for Treatment with RX-3117 in Pancreatic Cancer.

The novel cytidine analog RX-3117, which is activated by uridine-cytidine kinase 2 (UCK2), shows encouraging activity in pancreatic and bladder cancer Phase IIa studies. In this study we highlight the potential role of UCK2 as a biomarker for selecting patients for RX-3117 treatment. The online genomics analysis and visualization platform, R2, developed by the Oncogenomics department at the AMC (Amsterdam, The Netherlands) was used for in silico UCK2-mRNA correlation with overall survival of pancreatic cancer patients, while UCK2 protein expression was evaluated by immunohistochemistry on pancreatic tumor formalin-fixed-paraffin-embedded sections from independent pancreatic cancer patients. mRNA expression was also determined for SUIT-2, PANC-1 and PDAC-3. Lastly, the drug sensitivity to RX-3117 was investigated using the Sulforhodamine-B cytotoxicity assay. The in silico data showed that a high UCK2-mRNA expression was correlated with a shorter overall survival in pancreatic cancer patients. Moreover, UCK2 protein expression was high in 21/25 patients, showing a significantly shorter mean. Overall Survival (8.4 versus 34.3 months, p=0.045). Sensitivity to RX-3117 varied between 0.6 and 11 μM. Pancreatic cancer cells are sensitive to pharmacologically achievable RX-3117 concentrations and UCK2 might be exploited as a biomarker for patient treatment selection.

Abstract 1267: Unusual mechanism of resistance to the novel cytidine analog fluorocyclopentenylcytosine (RX-3117)

Abstract RX-3117 is a novel cytidine analog showing encouraging results in ongoing Phase 2a studies with gemcitabine-resistant pancreatic ductal adenocarcinoma and advanced urothelial bladder cancer. Cellular uptake of RX-3117 is mediated by the equilibrative nucleoside transporter 1 (hENT1). RX-3117 is activated by uridine-cytidine kinase-2 (UCK2) and is not a substrate for cytidine deaminase (CDA), and shows a good oral bioavailability. In an earlier study accumulation of RX-3117 nucleotides was associated with sensitivity to the drug. RX-3117 is incorporated into RNA and DNA and inhibits DNA methyltransferase 1 (DNMT1). RX-3117 is active against gemcitabine-resistant non-small cell lung cancer (NSCLC) cell lines. In this study we aimed to elucidate potential resistance mechanisms against RX-3117. For that purpose the NSCLC cell lines H460, A549 and SW1573 (including its gemcitabine resistant variant SW-G) were exposed to increasing concentrations of RX-3117. For A549 and SW1573 two variants were obtained: A549/RX1, A549/RX2, SW1573/RX1 and SW1573/RX2. Resistance varied from 10 (H460; SW-G) to >100-fold for the other cell lines. Resistance was stable except for H460 cells. Cross-resistance in the same range was observed for the cytidine analogs ethynyl-cytidine (ETC), cyclopentenylcytosine (CPEC) and aza-cytidine (aza-CR), which are all activated by UCK2; no cross-resistance was observed for gemcitabine and aza-deoxycytidine which are activated by deoxycytidine kinase. No change was observed in the expression of DNMT1, while expression of ribonucleotide reductase 1 was decreased. However, analysis of UCK2 at the enzyme activity level, protein and gene expression did not reveal a decrease in UCK2 while for ETC, aza-CR and CPEC resistance was reported to be mediated by a UCK2 deficiency. No change was found in the other activating enzymes UMP-kinase, CMP-kinase and NME1/NDKA. Despite this lack of change, accumulation of RX-3117 and RX-3117 nucleotides (mono-, di- and triphosphate) was 2-5-fold lower in the resistant cells after incubation with 10 or 100 μM RX-3117 for 4-24 hr. No evidence for accumulation of RX-3117 deoxynucleotides was found in both the parent and the resistant cell lines. Since no change in hENT1 was found, cell lines were further investigated by using RNA-seq, and western blotting focusing on nucleoside/nucleotide degradation enzymes. CDA was decreased in resistant cells, but the cytosolic pyrimidine nucleotidase NT5C3 was increased in the resistant cell lines as well as DCTPP1, which can degrade deoxynucleoside triphosphates. Moreover several DNA repair enzymes SAMHD1, MTH1 and TDP1 were increased. However, inhibition of MTH1 and DCTPP1 did not increase sensitivity to RX-3117. In conclusion, induction of resistance to the novel cytidine analog RX-3117 led to a decreased accumulation of RX-3117 ribonucleotides, which might be associated with an increased degradation. Citation Format: Godefridus J. Peters, Dzjemma Sarkisjan, Btissame El Hassouni, Richard J. Honeywell, Joris R. Julsing, Beatrice Balboni, Daniel J. De Klerk, Safet Zekanovic, Kees Smid, Elisa Giovannetti, Young B. Lee, Deog J. Kim. Unusual mechanism of resistance to the novel cytidine analog fluorocyclopentenylcytosine (RX-3117) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1267.