Orotate phosphoribosyltransferase expression level in tumors is a potential determinant of the efficacy of 5-fluorouracil

Uricase sensitizes hepatocellular carcinoma cells to 5-fluorouracil through uricase-uric acid-UMP synthase axis

Conventional chemotherapy plays a key role in hepatocellular carcinoma (HCC) treatment, however, with intrinsic or acquired chemoresistance being a major constraint. Here, we aimed to identify potential target to reverse such chemoresistance. In the present study, we found significant difference in uridine monophosphate synthetase (UMPS) expression between 5-FU resistant and sensitive HCC cell lines and the overexpression or downregulation of UMPS impacted 5-FU response in HCC cells. We further found that inhibition of UMPS activity with uric acid at concentration present in human plasma decreased the 5-FU sensitivity of HCC cells, while reduction of uric acid levels with uricase improved the 5-FU sensitivity of HCC cells as well as colorectal cancer cells. In vivo studies also suggested that modulation of uric acid levels did affect 5-FU sensitivity of tumors. These data indicated that UMPS was correlated with the 5-FU resistance in HCC cells and uricase sensitized cancer cells to 5-FU through uricase-uric acid-UMP synthase axis, which provided a potential strategy to improve the efficacy of 5-FU-based chemotherapy for human cancers.

Pre-treatment evaluation of 5-fluorouracil degradation rate: association of poor and ultra-rapid metabolism with severe toxicity in a colorectal cancer patients cohort

Despite the wide use of 5-fluorouracil-based chemotherapy, development of severe toxicity that follow the treatment is not a rare event. The efforts to establish pretreatment tools for toxicity prediction, led to the development of various pharmacogenetic and biochemical assays, mainly targeted to assess the activity level of dihydropyrimidine dehydrogenase (DPD), the main metabolizing enzyme for 5-fluorouracil. Using peripheral blood mononuclear cells, we developed a biochemical assay, that is not limited to the evaluation of DPD activity, but determines the net result of all the enzymatic transformation of 5FU, in terms of the amount of drug consumed by the cells in a time unit. This parameter, named 5-fluorauracil degradation rate, presents a normal distribution inside the population and highlight the presence of an ultra-rapid metabolizers class of subjects, besides the expected poor metabolizers class. Here we will show that, in a colorectal cancer patient cohort, both poor and ultra-rapid metabolizers have significantly increased the risk of developing severe toxicity (grade3–4). Patient stratification depending on the individual 5-fluorouracil degradation rate allows to identify a 10% of the overall population at high risk of developing severe toxicity, compared to the 1.3% (as assessed in the Italian population) identified by the most commonly employed pharmacogenetic test, including the DPD polymorphism IVS14+1G>A.

Pre-treatment assay of 5-fluorouracil degradation rate (5-FUDR) to improve prediction of 5-fluorouracil toxicity in gastro-esophageal cancer

Background

5-fluorouracil (5-FU) based chemotherapy is the most common first line regimen used in gastric and gastroesophageal junction cancer, but development of severe toxicity is a main concern in the treatment. The present study is aimed to evaluate a novel pre-treatment assay, known as the 5-FU degradation rate (5-FUDR), as a predictive factor for 5-FU toxicity.

Methods

Pre-treatment 5-FUDR and gene polymorphisms related to 5-FU metabolism (DPYDIVS14+1G>A, MTHFRA1298T or C677T, TMYS TSER) were characterized in gastro-esophageal cancer patients. Association with toxicities was retrospectively evaluated, using multivariate logistic regression analysis.

Results

107 gastro-esophageal cancer patients were retrospectively analyzed. No relation between gene polymorphisms and toxicity were detected, while low (< 5^th centile) and high (> 95^th centile) 5-FUDRs were associated with development of grade 3-4 toxicity (OR 11.14, 95% CI 1.09-113.77 and OR 9.63, 95% CI 1.70-54.55, p = 0.002).

Conclusions

Compared to currently used genetic tests, the pre-treatment 5-FUDR seems useful in identifying patients at risk of developing toxicity.

Degradation Rate of 5-Fluorouracil in Metastatic Colorectal Cancer: A New Predictive Outcome Biomarker?

Background

5-FU based chemotherapy is the most common first line regimen used for metastatic colorectal cancer (mCRC). Identification of predictive markers of response to chemotherapy is a challenging approach for drug selection. The present study analyzes the predictive role of 5-FU degradation rate (5-FUDR) and genetic polymorphisms (MTHFR, TSER, DPYD) on survival.

Materials and Methods

Genetic polymorphisms of MTHFR, TSER and DPYD, and the 5-FUDR of homogenous patients with mCRC were retrospectively studied. Genetic markers and the 5-FUDR were correlated with clinical outcome.

Results

133 patients affected by mCRC, treated with fluoropyrimidine-based chemotherapy from 2009 to 2014, were evaluated. Patients were classified into three metabolic classes, according to normal distribution of 5-FUDR in more than 1000 patients, as previously published: poor-metabolizer (PM) with 5-FU-DR ≤ 0,85 ng/ml/10⁶ cells/min (8 pts); normal metabolizer with 0,85 < 5-FU-DR < 2,2 ng/ml/10⁶ cells/min (119 pts); ultra-rapid metabolizer (UM) with 5-FU-DR ≥ 2,2 ng/ml/10⁶ cells/min (6 pts). PM and UM groups showed a longer PFS respect to normal metabolizer group (14.5 and 11 months respectively vs 8 months; p = 0.029). A higher G3-4 toxicity rate was observed in PM and UM, respect to normal metabolizer (50% in both PM and UM vs 18%; p = 0.019). No significant associations between genes polymorphisms and outcomes or toxicities were observed.

Conclusion

5-FUDR seems to be significantly involved in predicting survival of patients who underwent 5-FU based CHT for mCRC. Although our findings require confirmation in large prospective studies, they reinforce the concept that individual genetic variation may allow personalized selection of chemotherapy to optimize clinical outcomes.

High/positive expression of 5-fluorouracil metabolic enzymes predicts better response to S-1 in patients with gastric cancer: a meta-analysis

PURPOSE

To provide an assessment by meta-analysis of the relationship between the expression variations of 5-fluorouracil metabolic enzymes and clinical outcomes in patients with gastric cancer treated with S-1.

METHOD

Databases were searched electronically from inception to April 19th, 2015. Studies in gastric cancer patients treated with S-1 investigating the expression variations of 5-fluorouracil metabolic enzymes were included after having been identified systematically. Pooled odds ratios (OR) for the objective response rate (ORR) and median survival ratio were calculated using the Review Manager 5.3 and Stata 12.0 software separately.

RESULTS

A total of 555 patients in 10 studies met our inclusion criteria. There was a significant difference in ORR between patients with high/+ and low/- expression of orotate phosphoribosyl transferase (OPRT) (OR = 8.06; 95% CI, 4.06-16.02; p&lt;0.001) and dihydropyrimidine dehydrogenase (DPD) (OR = 1.95; 95% CI, 1.21-3.13; p = 0.006). There was no significant difference in ORR between different expression levels of thymidylate synthase (TS) and thymidine phosphorylase (TP). Although patients with low/- TS expression, low/- TP expression and high/+ DPD expression showed a trend towards longer survival, no statistical significance was found. The median OS was significantly longer in patients with high/+ expression of OPRT (p = 0.076).

CONCLUSIONS

OPRT and DPD expression can be treated as a potential predictive biomarker for S-1 response in gastric cancer patients. Further investigation is warranted.

Orotate phosphoribosyltransferase is overexpressed in malignant pleural mesothelioma: Dramatically responds one case in high OPRT expression

Objective: Malignant pleural mesothelioma (MPM) is a rare and aggressive, treatment-resistant cancer. Pemetrexed, an inhibitor of thymidylate synthase (TS), is used worldwide for MPM as a first-line chemotherapy regimen. However, there is little consensus for a second-line chemotherapy. S-1, a highly effective dihydropyrimidine dehydrogenase (DPD)-inhibitory fluoropyrimidine, mainly acts via a TS inhibitory mechanism similar to pemetrexed. Orotate phosphoribosyltransferase (OPRT) is a key enzyme related to the first step activation of 5-fluorouracil (5-FU) for inhibiting RNA synthesis. We investigated 5-FU related-metabolism proteins, especially focusing on OPRT expression, in MPM Methods and Patients: Fifteen MPM patients who were diagnosed between July 2004 and December 2013 were enrolled. We examined the protein levels of 5-FU metabolism-related enzymes (TS, DPD, OPRT, and thymidine phosphorylase [TP]) in 14 cases Results: High TS, DPD, OPRT, and TP expressions were seen in 28.6%, 71.4%, 85.7%, and 35.7% of patients, respectively. We found that OPRT expression was extremely high in MPM tissue. We experienced one remarkable case of highly effective S-1 combined therapy for pemetrexed refractory MPM. This case also showed high OPRT protein expression Conclusion: The present study suggests that OPRT expression is high in MPM tumors. Although pemetrexed is mainly used for MPM chemotherapy as a TS inhibitor, S-1 has potential as an anticancer drug not only as a TS inhibitor but also inhibiting RNA synthesis through the OPRT pathway. This is the first report investigating OPRT protein expressions in MPM.

Enhancement of 5-fluorouracil-induced cytotoxicity by leucovorin in 5-fluorouracil-resistant gastric cancer cells with upregulated expression of thymidylate synthase

BACKGROUND

Elucidation of the mechanisms by which gastric cancer cells acquire resistance to 5-fluorouracil (5FU) may provide important clues to the development of effective chemotherapy for 5FU-resistant gastric cancer

METHODS

Four 5FU-resistant cell lines (MKN45/5FU, MKN74/5FU, NCI-N87/5FU, and KATOIII/5FU) were established by continuous exposure of the cells to progressively increasing concentrations of 5FU for about 1 year. Then, mRNA expression levels of four genes associated with 5FU metabolism, i.e., thymidylate synthase (TS), dihydropyrimidine dehydrogenase, thymidine phosphorylase, and orotate phosphoribosyltransferase, were quantitatively evaluated by real-time reverse transcriptase-polymerase chain reaction. In addition, TS protein expression was measured by Western blot analysis.

RESULTS

As compared with the parent cell lines, the 5FU-resistant cell lines showed 3.8- to 11.6-fold higher resistance to 5FU, as well as 1.9- to 3.5-fold higher TS mRNA expression and 1.6- to 7.1-fold higher TS protein expression. In contrast, the expressions of other genes did not differ significantly among the cell lines. The cytotoxicity of 5FU was enhanced 2.3- to 2.8 fold by leucovorin (LV) against three of the four 5FU-resistant cell lines.

CONCLUSIONS

Collectively, LV enhanced the cytotoxicity of 5FU not only against the parent gastric cancer cell lines, but also against the 5FU-resistant cell lines, even those with elevated TS expression levels. These results suggest that clinical studies of a combination of 5FU and LV are warranted in patients who have recurrent gastric cancer after 5FU-based therapy.

Data-driven assessment of the association of polymorphisms in 5-Fluorouracil metabolism genes with outcome in adjuvant treatment of colorectal cancer

A major challenge in the assessment of medicines, treatment options, etc., is to establish a framework for the comparison of risks and benefits of many different types and magnitudes, a framework that at the same time allows a clear distinction between the roles played by the statistical analyses of data and by judgements based on personal experience and expertise. The purpose of this study was to demonstrate how clinical data can be weighted, scored and presented by the use of an eight-step data-driven benefit-risk assessment method, where two genetic profiles are compared. Our aim was to present a comprehensive approach that is simple to apply, allows direct comparison of different types of risks and benefits, quantifies the clinical relevance of data and is tailored for the comparison of different options. We analysed a cohort of 302 patients with colorectal cancer treated with 5-Fluorouracil (5-FU). Endpoints were cure rate, survival rate, time-to-death (TTD), time-to-relapse (TTR) and main adverse drug reactions. Multifactor dimensionality reduction (MDR) was used to identify genetic interaction profiles associated with outcome. We have been able to demonstrate that a specific MDR-derived combination (the MDR-1 group) of dihydropyrimidine dehydrogenase and thymidylate synthase polymorphisms is associated with increased and clinically significant difference for cure and survival rates, TTD and probably also for TTR, which are seen as the most important endpoints. An inferior profile was observed for severe myocardial ischaemia. A probably inferior profile was seen for severe arthralgia/myalgia and severe infections. A clear superior profile was seen for severe mucositis/stomatitis. The proposed approach offers comprehensive, data-driven assessment that can facilitate decision processes, for example, in a clinical setting. It employs descriptive statistical methods to highlight the clinically relevant differences between options.

Introduction of a fluorine atom at C3 of 3-deazauridine shifts its antimetabolic activity from inhibition of CTP synthetase to inhibition of orotidylate decarboxylase, an early event in the de novo pyrimidine nucleotide biosynthesis pathway

The antimetabolite prodrug 3-deazauridine (3DUrd) inhibits CTP synthetase upon intracellular conversion to its triphosphate, which selectively depletes the intracellular CTP pools. Introduction of a fluorine atom at C3 of 3DUrd shifts its antimetabolic action to inhibition of the orotidylate decarboxylase (ODC) activity of the UMP synthase enzyme complex that catalyzes an early event in pyrimidine nucleotide biosynthesis. This results in concomitant depletion of the intracellular UTP and CTP pools. The new prodrug (designated 3F-3DUrd) exerts its inhibitory activity because its monophosphate is not further converted intracellularly to its triphosphate derivative to a detectable extent. Combinations with hypoxanthine and adenine markedly potentiate the cytostatic activity of 3F-3DUrd. This is likely because of depletion of 5-phosphoribosyl-1-pyrophosphate (consumed in the hypoxanthine phosphoribosyl transferase/adenine phosphoribosyl transferase reaction) and subsequent slowing of the 5-phosphoribosyl-1-pyrophosphate-dependent orotate phosphoribosyl transferase reaction, which depletes orotidylate, the substrate for ODC. Further efficient anabolism by nucleotide kinases is compromised apparently because of the decrease in pK(a) brought about by the fluorine atom, which affects the ionization state of the new prodrug. The 3F-3DUrd monophosphate exhibits new inhibitory properties against a different enzyme of the pyrimidine nucleotide metabolism, namely the ODC activity of UMP synthase.

Design and selection of Toca 511 for clinical use: modified retroviral replicating vector with improved stability and gene expression

Retroviral replicating vectors (RRVs) are a nonlytic alternative to oncolytic replicating viruses as anticancer agents, being selective both for dividing cells and for cells that have defects in innate immunity and interferon responsiveness. Tumor cells fit both these descriptions. Previous publications have described a prototype based on an amphotropic murine leukemia virus (MLV), encoding yeast cytosine deaminase (CD) that converts the prodrug 5-fluorocytosine (5-FC) to the potent anticancer drug, 5-fluorouracil (5-FU) in an infected tumor. We report here the selection of one lead clinical candidate based on a general design goal to optimize the genetic stability of the virus and the CD activity produced by the delivered transgene. Vectors were tested for titer, genetic stability, CD protein and enzyme activity, ability to confer susceptibility to 5-FC, and preliminary in vivo antitumor activity and stability. One vector, Toca 511, (aka T5.0002) encoding an optimized CD, shows a threefold increased specific activity in infected cells over infection with the prototype RRV and shows markedly higher genetic stability. Animal testing demonstrated that Toca 511 replicates stably in human tumor xenografts and, after 5-FC administration, causes complete regression of such xenografts. Toca 511 (vocimagene amiretrorepvec) has been taken forward to preclinical and clinical trials.

The association of polymorphisms in 5-fluorouracil metabolism genes with outcome in adjuvant treatment of colorectal cancer

AIM

The purpose of this study was to investigate whether specific combinations of polymorphisms in 5-fluorouracil (5-FU) metabolism-related genes were associated with outcome in 5-FU-based adjuvant treatment of colorectal cancer.

METHODS

We analyzed two cohorts of 302 and 290 patients, respectively, one cohort for exploratory analyses and another cohort for validating the exploratory analyses. A total of ten polymorphisms in genes involved in 5-FU pharmacodynamics and pharmacokinetics were studied. End points were disease-free survival (DFS) and overall survival. Multifactor dimensionality reduction was used to identify genetic interaction profiles associated with outcome.

RESULTS

Low-expression alleles in thymidylate synthase (TYMS) were associated with decreased DFS and overall survival (DFS:hazard ratio [HR] exploration 2.65 [1.40-4.65]; p = 0.004, HR validation 1.69 [1.03-2.66]; p = 0.03). A specific multifactor dimensionality reduction derived combination of dihydropyrimidine dehydrogenase and TYMS polymorphisms was associated with increased DFS (HR exploration 0.69 [0.49-0.98]; p = 0.04, HR validation 0.66 [0.45-0.95]; p = 0.03). Specific combinations of functional polymorphisms in DPYD and TYMS were demonstrated to be associated with DFS and overall survival in patients receiving adjuvant 5-FU-based treatment. Specifically high TYMS expression alleles seem to be associated with decreased DFS.

S-1 and the treatment of gastric cancer with peritoneal dissemination

Peritoneal dissemination is the most common metastatic pattern of gastric cancer. We frequently face the necessity for gastrectomy in the event of gastric stenosis or gastric bleeding. However, the indication for palliative gastrectomy and the effectiveness of palliative chemotherapy are not clear. We retrospectively evaluated the prognostic factors after palliative gastrectomy in 121 gastric cancer patients with peritoneal dissemination. The expression of orotate phosphoribosyl transferase (OPRT) was examined immunohistochemically. The median survival time of all patients after palliative gastrectomy was 8.8 months. In the multivariate analyses, we adjusted the data of 82 patients without liver metastases for the background of 5-fluouracil (5-FU)-based chemotherapy regimen. The analysis revealed that the degree of peritoneal dissemination (multiple vs. a few metastases or cytology-positive; P= 0.01) and chemotherapy (S-1 vs. other 5-FU; P=0.01) were independent predictors of survival. Particularly, S-1 treatment was associated with a more favorable prognosis of the patients with high levels of OPRT expression compared to that of the patients with low expression. Patients with peritoneal dissemination are considered as terminal and inoperable. However, S-1 treatment may improve the survival after palliative gastrectomy in patients selected according to the degree of peritoneal dissemination and high OPRT expression.

Quantitative analysis of the enzymes associated with 5-fluorouracil metabolism in prostate cancer biopsies

Orotate phosphoribosyl transferase (OPRT) is the initial enzyme of 5-FU activation, in which 5-FU is converted to 5-fluorouridinemonophosphate. Dihydropyrimidine dehydrogenase (DPD) is a degrading enzyme that catabolizes 5-FU. In this study, we investigated the expression of these enzymes in normal prostate gland (NP), hormone-sensitive prostate cancer (HSPC), and hormone-refractory prostate cancer (HRPC). The prostatic tissue specimens were obtained from patients who had undergone prostate needle biopsies without any treatments or with PSA failure after initial androgen deprivation. The tissue samples derived from formalin-fixed, paraffin-embedded (FFPE) sections were prepared by laser-capture microdissection, and from them RNA was extracted. The levels of OPRT and DPD mRNA expression were examined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). The level of OPRT mRNA expression in the HSPC or the HRPC specimens was significantly higher than that in the NP specimens. There was a significant correlation between OPRT mRNA expression levels and the tumor pathological grade. Furthermore, the OPRT/ DPD expression ratio, a powerful predictive factor to evaluate 5-FU sensitivity, in the HRPC group was significantly higher than that in the low-grade HSPC group. Thus, the quantitative evaluation for these enzymes based on phosphorylation of 5-FU may be an effective option for some prostate cancer patients, particularly HRPC group.

Pharmacogenetic analyses of a phase III trial in metastatic gastroesophageal adenocarcinoma with fluorouracil and leucovorin plus either oxaliplatin or cisplatin: a study of the arbeitsgemeinschaft internistische onkologie

PURPOSE

To evaluate the association of germ-line polymorphisms of genes that may impact treatment outcome of platinum and fluorouracil combination chemotherapy in advanced gastric cancer (AGC).

PATIENTS AND METHODS

Blood samples of 156 patients enrolled onto a phase III study comparing fluorouracil, leucovorin, and oxaliplatin with fluorouracil, leucovorin, and cisplatin were collected. Polymorphisms within genes of TS, MTHFR, MTR, OPRT, XPD, ERCC1, XRCC1, XPA, GSTP1, GSTT1, and GSTM1 were genotyped using polymerase chain reaction-based techniques.

RESULTS

Median overall survival (OS) was 11.8 months (95% CI, 9.75 to 13.79 months) and median progression-free survival (PFS) was 5.8 months (95% CI, 4.99 to 6.61 months). The TS-3R/+6 haplotype (P = .004), the GSTT1 deletion polymorphism (P = .015), and genotypes of OPRT-Gly213Ala (P = .003) and XRCC1-Arg399Gln (P = .023) could be identified as independent predictors of OS. For PFS analyses, the TS-3R/+6 haplotye (P = .003) and MTR-A2756G (P = .01) were identified as independent positive predictors. The association between the GSTT1 deletion polymorphism and PFS showed only borderline significance (P = .053). Treatment related hematotoxicity in terms of grade 3/4 leukopenia was lowest among TS-3R/+6 haplotype carriers (P = .037). Grade 3/4 neutropenia was directly associated with the MTR-2756G/G genotype (P = .011), GSTP1-105Ile/Ile genotype (P = .02), and with the ERCC1-118T/8092C-haplotype (P = .042). In addition, significant associations between GSTP1-105Ile/Ile genotype and neurotoxicity and between the XPD-Asn312/751Gln haplotype and nephrotoxicity could be identified (P = .028 and P = .005, respectively).

CONCLUSION

These findings underline the hypothesis that germ-line polymorphisms may play an important role in individualizing chemotherapy in AGC and deserve further prospective evaluation in AGC patients.