Deoxycytidine Kinase Expression Research Articles

Abstract 3866: Azvudine: An emerging immunomodulator in the treatment of cancer and viral infections

Abstract Azvudine (FNC) is a nucleoside analog that has secured approval from the CDE in China for the treatment of both AIDS and COVID-19. In these contexts, it has showed remarkable efficacy and safety when taken orally. Typically, nucleoside analog drugs function by integrating into DNA and impeding DNA synthesis, evident in drugs like 5-FU, Capecitabine, Ara-C, and Gemcitabine. Furthermore, FNC has been reported to exhibit robust anti-tumor properties, curbing cell proliferation, initiating G1 and S phase arrests, and advancing apoptosis across various human cancer cell lines. Grounded in this mode of action, we have ascertained that the anti-tumor effects of FNC intricately align with the expression of deoxycytidine kinase (dCK) both in vitro and in vivo. Remarkably, our studies delved into the effects and underlying mechanisms of FNC in enhancing the tumor microenvironment within solid tumors. Our findings, stemming from cell-based assays and in vivo animal experiments, elucidate the following: 1. FNC can trigger immunogenic cell death (ICD) in tumor cells. This is evidenced by the surface presentation and liberation of damage-associated molecular patterns (DAMPs) such as Calreticulin, HSP70, HSP90, Annexin A1, and HMGB1, which in turn stimulate both innate and adaptive immune responses. 2. FNC substantially reduces the population of monocytic-myeloid derived suppressor cells (M-MDSC) and Polymorphonuclear-myeloid derived suppressor cells (PMN-MDSC) in the tumor microenvironment. Concurrently, it boosts the infiltration and proliferation of CD8+T, CD4+T and NK cells. This instigates the transformation of the tumor microenvironment from a 'cold' state to a 'hot' one, enhancing the synergistic effects of PD-1 when used in tandem with FNC. This mechanism was substantiated through a high proportion of MDSCs observed in H22 and CT-26 syngeneic models, and contrastingly, a low proportion in MC38 and LL/2 in vivo syngeneic models. Notably, every animal subjected to combined FNC and PD-1 treatment in the H22 and CT-26 in vivo models witnessed complete tumor regression. Given these revelations, there's a compelling argument that FNC monotherapy possesses immense potential as an anti-tumor agent. The potent anticancer effects of FNC in vitro and in vivo warrants further investigation of its anticancer potential as immunomodulator. Citation Format: Pan Li, Limin Jia, Zhaoyang Wang, Jinfa Du. Azvudine: An emerging immunomodulator in the treatment of cancer and viral infections [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3866.

Deoxycytidine kinase inactivation enhances gemcitabine resistance and sensitizes mitochondrial metabolism interference in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is considered one of the most lethal forms of cancer. Although in the last decade, an increase in 5-year patient survival has been observed, the mortality rate remains high. As a first-line treatment for PDAC, gemcitabine alone or in combination (gemcitabine plus paclitaxel) has been used; however, drug resistance to this regimen is a growing issue. In our previous study, we reported MYC/glutamine dependency as a therapeutic target in gemcitabine-resistant PDAC secondary to deoxycytidine kinase (DCK) inactivation. Moreover, enrichment of oxidative phosphorylation (OXPHOS)-associated genes was a common property shared by PDAC cell lines, and patient clinical samples coupled with low DCK expression was also demonstrated, which implicates DCK in cancer metabolism. In this article, we reveal that the expression of most genes encoding mitochondrial complexes is remarkably upregulated in PDAC patients with low DCK expression. The DCK-knockout (DCK KO) CFPAC-1 PDAC cell line model reiterated this observation. Particularly, OXPHOS was functionally enhanced in DCK KO cells as shown by a higher oxygen consumption rate and mitochondrial ATP production. Electron microscopic observations revealed abnormal mitochondrial morphology in DCK KO cells. Furthermore, DCK inactivation exhibited reactive oxygen species (ROS) reduction accompanied with ROS-scavenging gene activation, such as SOD1 and SOD2. SOD2 inhibition in DCK KO cells clearly induced cell growth suppression. In combination with increased anti-apoptotic gene BCL2 expression in DCK KO cells, we finally reveal that venetoclax and a mitochondrial complex I inhibitor are therapeutically efficacious for DCK-inactivated CFPAC-1 cells in in vitro and xenograft models. Hence, our work provides insight into inhibition of mitochondrial metabolism as a novel therapeutic approach to overcome DCK inactivation-mediated gemcitabine resistance in PDAC patient treatment.

DCK expression by RNAseq as a potential biomarker of gemcitabine response in sarcoma.

11578 Background: Deoxycytidine kinase (DCK) is responsible for activation of gemcitabine by phosphorylation of gemcitabine to its monophosphate form. Studies have suggested that DCK expression may be correlated to response to gemcitabine in various solid tumors, and that downregulation of DCK may be at least partly responsible for gemcitabine-resistance in vitro. However, the significance of DCK expression in sarcomas as a biomarker of response to gemcitabine remains poorly characterized. Methods: Participants enrolled in the prospective Electronic Health Record (EHR)-Based Comprehensive Bone and Soft Tumor Registry ( NCT02677961 ) at The Ohio State James Cancer Center who had received gemcitabine-based chemotherapy for the treatment of bone and soft tissue sarcoma were eligible for this study. A total of 179 patients were identified who had received at least one cycle of gemcitabine-based chemotherapy, between January 1st, 2014, to December 31st, 2022. Whole exome RNASeq expression data was available for 36 of these patients who had received gemcitabine-based chemotherapy in the setting of active disease. Results: Of the 36 patients included in this study, 22 were female and 14 were male. Nine different main disease types were identified in the patient subset. These include angiosarcoma (8), chondrosarcoma (1), leiomyosarcoma (16), liposarcoma (3), malignant peripheral nerve sheath tumor (1), myxofibrosarcoma (2), osteosarcoma (2), undifferentiated pleomorphic sarcoma (3), and undifferentiated spindle cell sarcoma (1). The median time to treatment discontinuation (TTD) among all patients was 178 days. Among DCK low-expressors (n = 16), the median TTD was 86 days; among high-expressors (n = 16), the median TTD was not reached. Differences between groups did not reach statistical significance (HR = 0.55, p = 0.14). Conclusions: DCK expression by clinical RNASeq is a potential biomarker of gemcitabine-response in sarcoma, but larger studies are necessary to evaluate the potential clinical significance and possible role of DCK expression in identifying patients most likely to benefit from gemcitabine-based chemotherapy.

MYC/Glutamine Dependency Is a Therapeutic Vulnerability in Pancreatic Cancer with Deoxycytidine Kinase Inactivation-Induced Gemcitabine Resistance.

Our study revealed the key pathways involved in gemcitabine resistance in PDAC, thus providing potential therapeutic strategies.

Decitabine-induced DNA methylation-mediated transcriptomic reprogramming in human breast cancer cell lines; the impact of DCK overexpression.

Decitabine (DAC), a DNA methyltransferase (DNMT) inhibitor, is tested in combination with conventional anticancer drugs as a treatment option for various solid tumors. Although epigenome modulation provides a promising avenue in treating resistant cancer types, more studies are required to evaluate its safety and ability to normalize the aberrant transcriptional profiles. As deoxycytidine kinase (DCK)-mediated phosphorylation is a rate-limiting step in DAC metabolic activation, we hypothesized that its intracellular overexpression could potentiate DAC’s effect on cell methylome and thus increase its therapeutic efficacy. Therefore, two breast cancer cell lines, JIMT-1 and T-47D, differing in their molecular characteristics, were transfected with a DCK expression vector and exposed to low-dose DAC (approximately IC20). Although transfection resulted in a significant DCK expression increase, further enhanced by DAC exposure, no transfection-induced changes were found at the global DNA methylation level or in cell viability. In parallel, an integrative approach was applied to decipher DAC-induced, methylation-mediated, transcriptomic reprogramming. Besides large-scale hypomethylation, accompanied by up-regulation of gene expression across the entire genome, DAC also induced hypermethylation and down-regulation of numerous genes in both cell lines. Interestingly, TET1 and TET2 expression halved in JIMT-1 cells after DAC exposure, while DNMTs’ changes were not significant. The protein digestion and absorption pathway, containing numerous collagen and solute carrier genes, ranking second among membrane transport proteins, was the top enriched pathway in both cell lines when hypomethylated and up-regulated genes were considered. Moreover, the calcium signaling pathway, playing a significant role in drug resistance, was among the top enriched in JIMT-1 cells. Although low-dose DAC demonstrated its ability to normalize the expression of tumor suppressors, several oncogenes were also up-regulated, a finding, that supports previously raised concerns regarding its broad reprogramming potential. Importantly, our research provides evidence about the involvement of active demethylation in DAC-mediated transcriptional reprogramming.

E2F2 enhances the chemoresistance of pancreatic cancer to gemcitabine by regulating the cell cycle and upregulating the expression of RRM2.

Both pro-oncogenic and anti-oncogenic effects of E2F2 have been revealed in different malignancies. However, the precise role of E2F2 in pancreatic cancer, in particular in relation to therapeutic intervention with gemcitabine, remains unclear. In this study, the effect of E2F2 on the proliferation and cell cycle modulation of pancreatic cancer cells, and whether E2F2 plays a role in the treatment of pancreatic cancer cells by gemcitabine, were investigated. The expression of E2F2 in pancreatic cancer was assessed by various methods including bioinformatics prediction, Western blotting, and real-time PCR. The effect of E2F2 on the proliferation and cell cycling of pancreatic cancer cells was analyzed by tissue culture and flow cytometry. In addition, the effect of E2F2 on the intervention of pancreatic cancer by gemcitabine was investigated using both in vitro and in vivo approaches. The expression of E2F2 was found to be significantly increased in pancreatic cancer tissues and cell lines. The pathogenic capacity of E2F2 lied in the fact that this transcription factor promoted the transformation of pancreatic cancer cell cycle from G1-phase to S-phase, thus enhancing the proliferation of pancreatic cancer cells. Furthermore, the expression of E2F2 was increased in pancreatic cancer cells in the presence of gemcitabine, and the augmented expression of E2F2 upregulated the gemcitabine resistance-related gene RRM2 and its downstream signaling molecule deoxycytidine kinase (DCK). The resistance of pancreatic cancer cells to gemcitabine was confirmed using both in vitro and in vivo models. In this study, E2F2 has been demonstrated for the first time to play a pro-oncogenic role in pancreatic cancer by promoting the transition of the cell cycle from G1-phase to S-phase and, therefore, enhancing the proliferation of pancreatic cancer cells. E2F2 has also been demonstrated to enhance the chemotherapy resistance of pancreatic cancer cells to gemcitabine by upregulating the expression of RRM2 and DCK that is downstream of RRM2.

Abstract 3034: Purine nucleoside phosphorylase regulates metabolic and immune checkpoints

Abstract Purine nucleoside phosphorylase (PNP) functions as a central regulator of nucleotide metabolism by catalyzing the degradation of purine nucleosides guanosine and deoxyguanosine. PNP inactivation has been paradoxically associated with both immunodeficiency and autoimmunity in humans but the genetic and molecular determinants of these divergent outcomes are poorly defined and whether they reflect cell type specific mechanisms is currently unknown. Moreover, the mechanisms underlying the clinical efficacy of PNP inhibitors in a subset of patients with hematological malignancies are yet to be determined, thereby severely limiting the potential of this promising new class of metabolic targeted therapies. To address these gaps in knowledge we performed a systematic evaluation of the metabolic, immunological and cell-context phenotypic effects of targeting PNP using a clinical-stage inhibitor with picomolar affinity and excellent oral bioavailability. Here we show that across cancer types PNP inhibition is synthetically lethal with sterile alpha motif and HD domain-containing protein 1 (SAMHD1) deficiency by triggering massive dGTP pool expansion, and impairing DNA replication. These cytotoxic effects require the expression of deoxycytidine kinase (dCK) which mediates the intracellular trapping of deoxyguanosine and expansion of dGTP pools, and are opposed by environmental deoxycytidine produced by bone marrow stromal cells in a SAMHD1 and nucleoside transporter dependent manner. This resistance mechanism to PNP inhibition can be counteracted by the deoxycytidine catabolizing enzyme cytidine deaminase (CDA). We further show that in addition to, and independent of its dCK and CDA-dependent cytotoxic effects in SAMHD1 deficient cells, PNP inhibition elevates serum inflammatory cytokines and cytokine transcript levels in secondary lymphoid organs. Using scRNAseq we identify CD19+ B-cells and CSF1R+ macrophages, which express the pattern recognition receptor TLR7, as the drivers of these alterations. TLR7 activation in these cell types is promoted by guanosine accumulation which functions as a ligand for TLR7 alongside uridine-containing ssRNA. Importantly, TLR7 stimulation achieved by PNP inhibition initiates transcriptional alterations that are quantitatively and qualitatively unique from synthetic TLR7 agonists, such as the production of type I interferons. We additionally demonstrate that PNP inactivation stimulates germinal center responses in secondary lymphoid organs via the expansion of activated B-cells and T follicular helper cells. In summary, we demonstrate that by modulating multiple metabolic and immune checkpoints in a multigenic, cell type and environment dependent manner, pharmacological PNP inhibition elicits specific outcomes which can be leveraged for the development of novel therapeutic applications. Citation Format: Evan R. Abt, Khalid Rashid, Thuc M. Le, Hailey R. Lee, Amanda L. Creech, Ting-Ting Wu, Thomas Mehrling, Shanta Bantia, Caius G. Radu. Purine nucleoside phosphorylase regulates metabolic and immune checkpoints [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3034.

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.

Drug resistance to nelarabine in leukemia cell lines might be caused by reduced expression of deoxycytidine kinase through epigenetic mechanisms.

Drug resistance is a serious problem in leukemia therapy. A novel purine nucleoside analogue, nelarabine, is available for the treatment of children with T cell acute lymphoblastic leukemia. We investigated the mechanisms of drug resistance to nelarabine. Nelarabine-resistant cells were selected by stepwise and continuous exposure to nelarabine using the limiting dilution method in human B and T cell lymphoblastic leukemia cell lines. Expression analysis was performed using real-time polymerase chain reaction, and epigenetic analysis was performed using methylation-specific polymerase chain reaction and chromatin immunoprecipitation. The RNA expression level for deoxycytidine kinase (dCK) was decreased in nelarabine-resistant leukemia cells. There were no differences between the parental and nelarabine-resistant leukemia cells in the methylation status of the promoter region of the dCK gene. In the chromatin immune precipitation assay, decreased acetylation of histones H3 and H4 bound to the dCK promoter was seen in the nelarabine-resistant cells when compared to the parental cells. Furthermore, treatment with a novel histone deacetylase inhibitor, vorinostat, promoted the cytotoxic effect of nelarabine along with increased expression of the dCK gene, and it increased acetylation of both histones H3 and H4 bound to the dCK promoter in nelarabine-resistant leukemia cells. The combination index showed that the effect of nelarabine and vorinostat was synergistic. This study reports that nelarabine with vorinostat can promote cytotoxicity in nelarabine-resistant leukemia cells through epigenetic mechanisms.

RRM1 Expression as a Prognostic Biomarker for Unresectable or Recurrent Biliary Tract Cancer Treated with Gemcitabine plus Cisplatin.

The combination of gemcitabine plus cisplatin (GP) is regarded as a first-line treatment for patients with unresectable or recurrent biliary tract cancer (BTC). Several proteins including human equilibrative nucleoside transporter-1 (hENT1), deoxycytidine kinase (DCK), cytidine deaminase (CDA), and ribonucleotide reductase subunit 1 (RRM1) are known to be involved in gemcitabine uptake and metabolism. This study was aimed to identify the predictive and prognostic values of these biomarkers in patients who treated with GP for advanced BTC. Tumor samples were obtained from 34 patients with unresectable or recurrent BTC who were treated with GP between August 2015 and February 2018. Intratumoral expression of hENT1, DCK, CDA and RRM1 was determined by immunohistochemistry and analyzed for association with chemotherapy response, progression-free survival (PFS) and overall survival (OS). Median OS was significantly longer in the RRM1-negative group than in the RRM1-positive (9.9 months vs. 5.9 months, p = 0.037). Multivariate adjustment analyses also demonstrated RRM1 expression as an independent prognostic factor for OS in patients treated with GP chemotherapy. Increased intratumoral expression of RRM1 on immunohistochemical staining may be a biomarker predicting poor survival in patients with GP chemotherapy for advanced BTC. Large-scale well-predefined prospective research is needed to validate the utility of biomarkers in clinical practice.

Venetoclax and alvocidib are both cytotoxic to acute myeloid leukemia cells resistant to cytarabine and clofarabine

BackgroundCytarabine (ara-C) is the major drug for the treatment of acute myeloid leukemia (AML), but cellular resistance to ara-C is a major obstacle to therapeutic success. The present study examined enhanced anti-apoptosis identified in 3 newly established nucleoside analogue-resistant leukemic cell line variants and approaches to overcoming this resistance.MethodsHL-60 human AML cells were used to develop the ara-C– or clofarabine (CAFdA)-resistant variants. The Bcl-2 inhibitor venetoclax and the Mcl-1 inhibitor alvocidib were tested to determine whether they could reverse these cells’ resistance.ResultsA 10-fold ara-C-resistant HL-60 variant, a 4-fold CAFdA-resistant HL-60 variant, and a 30-fold CAFdA-resistant HL-60 variant were newly established. The variants demonstrated reduced deoxycytidine kinase and deoxyguanosine kinase expression, but intact expression of surface transporters (hENT1, hENT2, hCNT3). The variants exhibited lower expression of intracellular nucleoside analogue triphosphates compared with non-variant HL-60 cells. The variants also overexpressed Bcl-2 and Mcl-1. Venetoclax as a single agent was not cytotoxic to the resistant variants. Nevertheless, venetoclax with nucleoside analogs demonstrated synergistic cytotoxicity against the variants. Alvocidib as a single agent was cytotoxic to the cells. However, alvocidib induced G1 arrest and suppressed the cytotoxicity of the co-administered nucleoside analogs.ConclusionsThree new nucleoside analogue-resistant HL-60 cell variants exhibited reduced production of intracellular analogue triphosphates and enhanced Bcl-2 and Mcl-1 expressions. Venetoclax combined with nucleoside analogs showed synergistic anti-leukemic effects and overcame the drug resistance.

Human equilibrative nucleoside transporter-1 and deoxycytidine kinase can predict gemcitabine effectiveness in Egyptian patients with Hepatocellular carcinoma.

BackgroundSeveral biomarkers of gemcitabine effectiveness have been studied in cancers, but less so in hepatocellular carcinoma (HCC), which is identified as the fifth most common cancer worldwide. Investigation of human equilibrative nucleoside transporter‐1 (HENT‐1) and deoxycytidine kinase (DCK), genes involved in gemcitabine uptake and metabolism, can be beneficial in the selection of potential cancer patients who could be responding to the treatment.AimTo study HENT‐1 and DCK gene expression in HCC patients with different protocols of treatment.MethodsUsing real‐time PCR, we analyzed expression levels of HENT‐1 and DCK genes from peripheral blood samples of 109 patients (20 controls & 89 HCC patients) between March 2015 and March 2017. All the 89 HCC patients received the antioxidants selenium (Se) and vitamin E (Vit.E) either alone (45 patients) or in combination with gemcitabine (24 patients) or radiofrequency ablation (RFA) (20 patients).ResultsThere was a significant increase in HENT‐1 expression levels in HCC patients treated with Se and Vit.E alone as compared to controls (P ˂ .0001), while there was no significant difference between HCC patients treated with gemcitabine or RFA as compared to controls. In contrast, expression of DCK was significantly increased in all groups of HCC patients as compared to controls (P ˂ .0001).ConclusionsHENT‐1 and DCK mRNA expressions are important markers of HCC and for GEM effect and GEM sensitivity in patients with HCC. This could be beneficial in the selection of HCC patients sensitive to gemcitabine to avoid subjecting resistant patients to unnecessary chemotherapy.

Cladribine modifies functional properties of microglia.

SummaryCladribine (CdA), an oral prodrug approved for the treatment of relapsing multiple sclerosis, selectively depletes lymphocytes. CdA passes the blood–brain barrier, suggesting a potential effect on central nervous system (CNS) resident cells. We examined if CdA modifies the phenotype and function of naive and activated primary mouse microglia, when applied in the concentrations 0·1–1 μM that putatively overlap human cerebrospinal fluid (CSF) concentrations. Primary microglia cultures without stimulation or in the presence of proinflammatory lipopolysaccharide (LPS) or anti‐inflammatory interleukin (IL)‐4 were treated with different concentrations of CdA for 24 h. Viability was assessed by MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide] assay. Phagocytotic ability and morphology were examined by flow cytometry and random migration using IncuCyte Zoom and TrackMate. Change in gene expression was examined by quantitative polymerase chain reaction (qPCR) and protein secretion by Meso Scale Discovery. We found that LPS and IL‐4 up‐regulated deoxycytidine kinase (DCK) expression. Only activated microglia were affected by CdA, and this was unrelated to viability. CdA 0·1–1 μM significantly reduced granularity, phagocytotic ability and random migration of activated microglia. CdA 10 μM increased the IL‐4‐induced gene expression of arginase 1 (Arg1) and LPS‐induced expression of IL‐1β, tumor necrosis factor (TNF), inducible nitric oxide synthase (iNOS) and Arg1, but protein secretion remained unaffected. CdA 10 μM potentiated the increased expression of anti‐inflammatory TNF receptor 2 (TNF‐R2) but not TNF‐R1 induced by LPS. This suggests that microglia acquire a less activated phenotype when treated with 0·1–1 μM CdA that putatively overlaps human CSF concentrations. This may be related to the up‐regulated gene expression of DCK upon activation, and suggests a potential alternative mechanism of CdA with direct effect on CNS resident cells.

DCK is an Unfavorable Prognostic Biomarker and Correlated With Immune Infiltrates in Liver Cancer.

Background:The biological function of deoxycytidine kinase in tumor is not yet clear, and there are a few studies relating to the correlation of deoxycytidine kinase gene with the occurrence and development of liver cancer.Methods:The messenger RNA expression of deoxycytidine kinase was analyzed with the use of the UALCAN and GEPIA database. Moreover, we assessed the function of deoxycytidine kinase on clinical prognosis with Kaplan-Meier plotter database. The relationship between deoxycytidine kinase and cancer immune infiltrates was investigated via Tumor Immune Estimation Resource site. Furthermore, Tumor Immune Estimation Resource was also used to evaluate the correlations between the expression of deoxycytidine kinase and gene marker sets of immune infiltrates.Results:The deoxycytidine kinase messenger RNA level significantly upregulated in patients with liver cancer compared to normal liver samples. Moreover, the increased expression of deoxycytidine kinase messenger RNA was closely associated with reduced overall survival and disease-free survival in all liver cancers. In addition, deoxycytidine kinase expression displayed a strong correlation with infiltrating levels of macrophages, neutrophils, and dendritic cells in liver cancer, and deoxycytidine kinase expression was positively correlated with diverse immune marker sets in liver cancer.Conclusions:All the above findings suggested that increased expression of deoxycytidine kinase was significantly related to unfavorable prognosis in patients with liver cancer. And deoxycytidine kinase is correlated with immune infiltrating levels, including those of B cells, macrophages, neutrophils, and dendritic cells in patients with liver cancer. These findings suggest that deoxycytidine kinase can be used as a prognostic biomarker for determining prognosis and immune infiltration in liver cancer. And deoxycytidine kinase is a potential target for liver cancer therapy, and these preliminary findings require further study to determine whether deoxycytidine kinase-targeting reagents might be developed for clinical application in liver cancer.

Role of Damage DNA-Binding Protein 1 in Pancreatic Cancer Progression and Chemoresistance.

Damaged DNA-binding protein 1 (DDB1) recruits nucleotide excision pathway proteins to form the UV-damaged DNA-binding protein complex and is required for DNA repair. DDB1 was reported to participate in apoptosis and chemoresistance regulation in several cancers. However, little is known about the function of DDB1 in pancreatic adenocarcinoma (PDAC). In this study, we reported that DDB1 functions as a tumor-promoting factor in PDAC by regulating cancer cell proliferation, epithelial-mesenchymal transition (EMT) and chemoresistance. Compared to normal pancreatic tissues, PDAC tissues had high expression levels of DDB1, and this high expression was positively correlated with poor prognosis. Furthermore, reductions in cell proliferation and EMT were observed in DDB1-deficient PDAC cell lines. Intriguingly, we also found that abrogation of DDB1 expression increased PDAC cell sensitivity to gemcitabine (GEM). Mechanistically, DDB1 knockdown was associated with an increase in deoxycytidine kinase expression in vivo and in vitro. In summary, our work demonstrated that DDB1 promotes PDAC progression and chemoresistance and may serve as a potential predictive marker and therapeutic target for PDAC treatment.

The modulation study of multiple drug resistance in bladder cancer by curcumin and resveratrol.

Gemcitabine (GCB), which functions via the inhibition of DNA synthesis, is commonly used in the treatment of bladder cancer; however, its response rate is not satisfactory due to the development of drug resistance. The potential for phytochemicals to reverse drug resistance in bladder cancer tumor cells was evaluated. A human bladder cancer cell line, T24, was cultured, and GCB-resistant cells (T24-GCB) were also established. The acquired resistance of T24-GCB to GCB was measured using an MTT assay. The gene expression of ATP-binding cassette (ABC) transporter protein family members was analyzed using reverse transcription-quantitative PCR analysis, and western blotting was performed to verify ABC family protein, cytoplasmic thymidine kinase (TK) and poly (ADP-ribose) polymerase (PARP) expression on whole cell lysates. Subsequently, resveratrol and curcumin were used to evaluate their modulation potential in decreasing the drug resistance of T24-GCB cells to GCB using MTT and migration assays. T24-GCB cells have increased drug resistance ability, with an 18.75-fold higher ID50 value compared with native T24 cells (105 vs. 5.6 nM). T24-GCB cells also exhibit increased cross resistance to mitomycin C and paclitaxel. The mRNA expression of ABCC2 in T24-GCB cells increased compared with that in native T24 cells. Via western blot analysis, it was determined that the expression of ABCC2 protein was also increased in T24-GCB cells. Conversely, the expression of ABCB1, ABCG2, deoxycytidine kinase (DCK), TK1 and TK2 decreased. Following curcumin and resveratrol treatment alone or combined with GCB, additive cytotoxic enhancement was observed, and the migratory abilities of T24-GCB cells were significantly decreased. Western blot analysis revealed that ABCC2 protein expression increased, and DCK, TK1 and TK2 expression decreased following co-treatment of T24-GCB cells with GCB + curcumin or resveratrol compared with GCB alone. Of note, there was a marked increase in cleaved-PARP expression in T24-GCB cells treated with a combination of GCB + curcumin or resveratrol. Both curcumin and resveratrol could reverse the drug resistance of T24-GCB cells in an additive pattern though PARP enhancement without changes in ABCC2 and DCK, TK1 and TK2 expression.

Danggui Buxue Decoction Sensitizes the Response of Non-Small-Cell Lung Cancer to Gemcitabine via Regulating Deoxycytidine Kinase and P-glycoprotein.

This study aimed to investigate whether the anti-tumor effect of gemcitabine (GEM) in non-small-cell lung cancer (NSCLC) treatment was affected by Danggui Buxue decoction (DBD), and explore the potential mechanisms. The combined use of GEM and DBD showed an enhanced tumor growth inhibition effect in a murine Lewis lung carcinoma (LLC) model. LC-MS/MS results showed that the pharmacokinetic behaviors of a GEM active metabolite, gemcitabine triphosphate (dFdCTP), were found to be altered remarkably in the peripheral blood mononuclear cells (PBMC) of DBD co-administration rats. In addition, after co-administration of DBD with GEM, Western Blot and qPCR results confirmed that the expression of deoxycytidine kinase (dCK) in tumor tissues of LLC-bearing mice were markedly increased. DBD co-administration also reversed the upregulation of P-glycoprotein (P-gp) in tumor tissues induced by GEM. Moreover, DBD could notably up-regulate the IL-12p70 and GM-CSF expression in mice serum, suggesting potential immunomodulatory activities in tumor-bearing mice. Meanwhile, DBD inhibited the P-gp efflux activity in A549 cells. Therefore, the regulation of dCK and P-gp played important roles in the alternation of GEM pharmacokinetics and the enhancement of the anti-tumor effect of GEM. DBD being a potential dCK promoter could work as an adjuvant agent to boost the anticancer effect of GEM.

Genome-scale CRISPR/Cas9 screen determines factors modulating sensitivity to ProTide NUC-1031

Gemcitabine is a fluoropyrimidine analogue that is used as a mainstay of chemotherapy treatment for pancreatic and ovarian cancers, amongst others. Despite its widespread use, gemcitabine achieves responses in less than 10% of patients with metastatic pancreatic cancer and has a very limited impact on overall survival due to intrinsic and acquired resistance. NUC-1031 (Acelarin), a phosphoramidate transformation of gemcitabine, was the first anti-cancer ProTide to enter the clinic. We find it displays important in vitro cytotoxicity differences to gemcitabine, and a genome-wide CRISPR/Cas9 genetic screening approach identified only the pyrimidine metabolism pathway as modifying cancer cell sensitivity to NUC-1031. Low deoxycytidine kinase expression in tumour biopsies from patients treated with gemcitabine, assessed by immunostaining and image analysis, correlates with a poor prognosis, but there is no such correlation in tumour biopsies from a Phase I cohort treated with NUC-1031.

Surmounting Cytarabine-resistance in acute myeloblastic leukemia cells and specimens with a synergistic combination of hydroxyurea and azidothymidine

Acute myeloid leukemia (AML) patients display dismal prognosis due to high prevalence of refractory and relapsed disease resulting from chemoresistance. Treatment protocols, primarily based on the anchor drug Cytarabine, remained chiefly unchanged in the past 50 years with no standardized salvage regimens. Herein we aimed at exploring potential pre-clinical treatment strategies to surmount Cytarabine resistance in human AML cells. We established Cytarabine-resistant sublines derived from human leukemia K562 and Kasumi cells, and characterized the expression of Cytarabine-related genes using real-time PCR and Western blot analyses to uncover the mechanisms underlying their Cytarabine resistance. This was followed by growth inhibition assays and isobologram analyses testing the sublines’ sensitivity to the clinically approved drugs hydroxyurea (HU) and azidothymidine (AZT), compared to their parental cells. All Cytarabine-resistant sublines lost deoxycytidine kinase (dCK) expression, rendering them refractory to Cytarabine. Loss of dCK function involved dCK gene deletions and/or a novel frameshift mutation leading to dCK transcript degradation via nonsense-mediated decay. Cytarabine-resistant sublines displayed hypersensitivity to HU and AZT compared to parental cells; HU and AZT combinations exhibited a marked synergistic growth inhibition effect on leukemic cells, which was intensified upon acquisition of Cytarabine-resistance. In contrast, HU and AZT combination showed an antagonistic effect in non-malignant cells. Finally, HU and AZT synergism was demonstrated on peripheral blood specimens from AML patients. These findings identify a promising HU and AZT combination for the possible future treatment of relapsed and refractory AML, while sparing normal tissues from untoward toxicity.

CYR61/CCN1 Regulates dCK and CTGF and Causes Gemcitabine-resistant Phenotype in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) develops extrinsic- and intrinsic-resistant phenotypes to prevent chemotherapies from entering into the cells by promoting desmoplastic reactions (DR) and metabolic malfunctions of the drugs. It is well established that these responses are also associated with pancreatic cancer cells' gemcitabine resistance. However, the mechanism by which these resistant pathways function in the pancreatic cancer cells remains poorly understood. In these studies, we show that CYR61/CCN1 signaling plays a vital role in making pancreatic cancer cells resistant to gemcitabine in vitro and also in a tumor xenograft model. We proved that the catastrophic effect of gemcitabine could significantly be increased in gemcitabine-resistant PDAC cells when CYR61/CCN1 is depleted, while this effect can be suppressed in gemcitabine-sensitive neoplastic cells by treating them with CYR61/CCN1 recombinant protein. Ironically, nontransformed pancreatic cells, which are sensitive to gemcitabine, cannot be resistant to gemcitabine by CYR61/CCN1 protein treatment, showing a unique feature of CYR61/CCN signaling that only influences PDAC cells to become resistant. Furthermore, we demonstrated that CYR61/CCN1 suppresses the expression of the gemcitabine-activating enzyme deoxycytidine kinase (dCK) while it induces the expression of a DR-promoting factor CTGF (connective tissue growth factor) in pancreatic cancer cells in vitro and in vivo Thus, the previously described mechanisms (dCK and CTGF pathways) for gemcitabine resistance may be two novel targets for CYR61/CCN1 to protect pancreatic cancer cells from gemcitabine. Collectively, these studies reveal a novel paradigm in which CYR61/CCN1regulates both extrinsic and intrinsic gemcitabine resistance in PDAC cells by employing unique signaling pathways.