Cytidine deaminase single-nucleotide polymorphism is predictive of toxicity from gemcitabine in patients with pancreatic cancer: RTOG 9704

Proof-of-principle studies on a strategy to enhance nucleotide imbalance specifically in cancer cells

Highly specific and potent inhibitors of dihydroorotate dehydrogenase (DHODH), an essential enzyme of the de novo pyrimidine ribonucleotide synthesis pathway, are in clinical trials for autoimmune diseases, viral infections and cancer. However, because DHODH inhibitors (DHODHi) are immunosuppressants they may reduce the anticancer activity of the immune system. Therefore, there may be a need to improve the therapeutic index of DHODHi in cancer patients. The aim of this study was to find strategies to protect activated T cells from DHODHi and to identify cancer types hypersensitive to these inhibitors. First, we observed that like uridine supplementation, adding cytidine to the culture medium protects T cells from DHODH blockage. Next, we identified tumor types with altered expression of pyrimidine ribonucleotide synthesis enzymes. In this regard, we detected that the expression of cytidine deaminase (CDA), which converts cytidine into uridine, is low in an important proportion of cancer cell lines and consistently low in neuroblastoma samples and in cell lines from neuroblastoma and small cell lung carcinoma. This suggested that in the presence of a DHODHi, an excess of cytidine would be deleterious for low CDA expressing cancer cell lines. We show that this was the case (as could be seen almost immediately after treatment) when cells were cultured with fetal bovine serum but, was significantly less evident when cultures contained human serum. One interesting feature of CDA is that aside from acting intracellularly, it is also present in human plasma/serum. Altogether, experiments using recombinant CDA, human serum, pharmacologic inhibition of CDA and T cell/cancer cell co-cultures suggest that the therapeutic index of DHODHi could be improved by selecting patients with low-CDA expressing cancers in combination with strategies to increase cytidine or the cytidine/uridine ratio in the extracellular environment. Collectively, this proof-of-principle study warrants the discovery of agents to deplete extracellular CDA.

Metabolic syndrome related gene signature predicts the prognosis of patients with pancreatic ductal carcinoma. A novel link between metabolic dysregulation and pancreatic ductal carcinoma

Background

Pancreatic cancer is one of the most common malignancies worldwide. In recent years, specific metabolic activities, which involves the development of tumor, caused wide public concern. In this study, we wish to explore the correlation between metabolism and progression of tumor.

Methods

A retrospective analysis including 95 patients with pancreatic ductal adenocarcinoma (PDAC) and PDAC patients from The Cancer Genome Atlas (TCGA), the International Cancer Genome Consortium (ICGC), and The Gene Expression Omnibus (GEO) database were involved in our study. Multivariate Cox regression analysis was used to construct the prognosis model. The potential connection between metabolism and immunity of PDAC was investigated through a weighted gene co-expression network analysis (WGCNA). 22 types of Tumor-infiltrating immune cells (TIICs) between high-risk and low-risk groups were estimated through CIBERSORT. Moreover, the potential immune-related signaling pathways between high-risk and low-risk groups were explored through the gene set enrichment analysis (GSEA). The role of key gene GMPS in developing pancreatic tumor was further investigated through CCK-8, colony-information, and Transwell.

Results

The prognostic value of the MetS factors was analyzed using the Cox regression model, and a clinical MetS-based nomogram was established. Then, we established a metabolism-related signature to predict the prognosis of PDAC patients based on the TCGA databases and was validated in the ICGC database and the GEO database to find the distinct molecular mechanism of MetS genes in PDAC. The result of WGCNA showed that the blue module was associated with risk score, and genes in the blue module were found to be enriched in the immune-related signaling pathway. Furthermore, the result of CIBERSORT demonstrated that proportions of T cells CD8, T cells Regulatory, Tregs NK cells Activated, Dendritic cells Activated, and Mast cells Resting were different between high-risk and low-risk groups. These differences are potential causes of different prognoses of PDAC patients. GSEA and the protein–protein interaction network (PPI) further revealed that our metabolism-related signature was significantly enriched in immune‐related biological processes. Moreover, knockdown of GMPS in PDAC cells suppressed proliferation, migration, and invasion of tumor cells, whereas overexpression of GMPS performed oppositely.

Conclusion

The results shine light on fundamental mechanisms of metabolic genes on PDAC and establish a reliable and referable signature to evaluate the prognosis of PDAC. GMPS was identified as a potential candidate oncogene with in PDAC, which can be a novel biomarker and therapeutic target for PDAC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02378-w.

Comprehensive pharmacogenetic analysis of DPYD, UGT, CDA, and ABCB1 polymorphisms in pancreatic cancer patients receiving mFOLFIRINOX or gemcitabine plus nab-paclitaxel

Modified FOLFIRINOX (mFOLFIRINOX) and gemcitabine + nab-paclitaxel (GemNab) regimens represent a standard treatment in advanced pancreatic cancer (aPC). DPYD and UGT1A1 variants are relevant predictors of fluoropyrimidine and irinotecan-associated adverse events (AEs). Furthermore, data about the associations between polymorphisms in ABCB and CDA genes and GemNab-related toxicities are still controversial. The present study analyzes the association between DPYD, UGT, ABCB1, CDA variants, and AEs in aPC patients (pts) treated with mFOLFIRINOX or GemNab. Blood samples collected from 104 aPC pts treated with mFOLFIRINOX and 63 with GemNab were tested for DPYD c.1679T>G, IVS14+1G>A, c.2194G>A, c.2846A>T, UGT1A1*28, CDA c.79A>C, and ABCB1 c.1236C>T, c.2677G>T/A, c.3435C>T by real-time PCR and automatic sequencing. In mFOLFIRINOX cohort, DPYD IVS14+1GA genotype was associated with G4 hematological AEs, while the UGT1A1*28 significantly correlated with the risk of thrombocytopenia (p = 0.006). In the GemNab cohort, a significant association between CDA c.79CC and high-grade nausea was observed (p = 0.002). Moreover, the presence of at least a mutant allele in ABCB1 increased the risk of overall hematological AEs (p = 0.01), both further strengthened by the presence of CDA c.79CC (p = 0.0002). DPYD IVS14+1A allele is confirmed to be associated with fluoropyrimidine life-threatening toxicities, and UGT1A1*28 is related with a higher risk of hematologic AEs following irinotecan treatment. CDA c.79C and ABCB1 c.1236T, c.2677T/A, and c.3435T mutant alleles are predictive biomarkers of GemNab-related AEs. All these variants should be considered in aPC pts candidate to mFOLFIRINOX or GemNab treatments.

A Severe Case of Drug-Induced Liver Injury after Gemcitabine Administration: A Highly Probable Causality Grading as Assessed by the Updated RUCAM Diagnostic Scoring System

Gemcitabine is an antineoplastic drug used in several forms of advanced pancreatic, lung, breast, ovarian, and bladder cancer. Common side effects include bone marrow suppression, fatigue, diarrhea, nausea, gastrointestinal upset, rash, alopecia, and stomatitis. Transient serum enzyme elevations could be observed during therapy, but clinically significant acute liver injury has been rarely associated with its use. Few cases of acute liver injury have been reported in the literature. We reported the clinical case of a 73--year-old man who developed clinically significant acute hepatic injury after using gemcitabine. Possible causes, clinical presentation, and treatments are discussed. According to the updated RUCAM score, the case was rated 10 points and became a suspected drug-induced liver injury. Moreover, on the liver biopsy, there were histological findings of mild-to-moderate portal hepatitis, eosinophilia, bile duct injury, and mild perisinusoidal fibrosis, suggesting drug damage.

An initial genetic analysis of gemcitabine-induced high-grade neutropenia in pancreatic cancer patients in CALGB 80303 (Alliance)

OBJECTIVES

One of the standard of care regimens for advanced pancreatic cancer is gemcitabine-based chemotherapy. The efficacy of gemcitabine is limited by dose-limiting hematologic toxicities especially neutropenia. Uncovering the variability of these toxicities attributed to germline DNA variation is of great importance.

PATIENTS AND METHODS

CALGB 80303 was a randomized study in advanced pancreatic cancer patients treated with gemcitabine with or without bevacizumab. The study protocol included genotyping of genes of gemcitabine disposition (CDA, DCTD, SLC29A1, SLC28A1, and SLC29A2), as well as a genome-wide analysis. The clinical phenotype was time to early high-grade neutropenia event accounting for progression or death or other treatment-terminating adverse events as competing for informative events. The inference was carried out on the basis of the association between genotype and cause-specific hazard of a neutropenic event.

RESULTS

The primary analyses were carried out on the basis of 294 genetically estimated European pancreatic cancer patients. For CDA rs2072671 (A>C), AC and CC patients had a lower risk of neutropenia than AA patients (P=0.01, hazard ratio: 0.61, 95% confidence interval: 0.41-0.89). For SLC28A1 rs3825876 (G>A), AA patients have a higher risk of neutropenia than GA and GG patients (P=0.02, hazard ratio: 1.51, 95% confidence interval: 1.06-2.16). CDA rs2072671 was associated with increased mRNA expression in whole blood in three studies (P=2.7e-14, 6.61e-62, and 9.70e-65). In the genome-wide analysis, variants in TGFB2 were among the top hits (lowest P=1.62e-06) but had no effect in luciferase assays.

CONCLUSION

This is the first genetic analysis of gemcitabine-induced neutropenia using a competing risk model in a prospective randomized clinical study has proposed a potentially novel mechanism of the protective effect of the CDA rs2072671 variant. Further confirmation is needed.

An integrated epigenome and transcriptome analysis identifies PAX2 as a master regulator of drug resistance in high grade pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is notoriously difficult to treat due to its aggressive, ever resilient nature. A major drawback lies in its tumor grade; a phenomenon observed across various carcinomas, where highly differentiated and undifferentiated tumor grades, termed as low and high grade respectively, are found in the same tumor. One eminent problem due to such heterogeneity is drug resistance in PDAC. This has been implicated to ABC transporter family of proteins that are upregulated in PDAC patients. However, the regulation of these transporters with respect to tumor grade in PDAC is not well understood. To combat these issues, a study was designed to identify novel genes that might regulate drug resistance phenotype and be used as targets. By integrating epigenome with transcriptome data, several genes were identified based around high grade PDAC. Further analysis indicated oncogenic PAX2 transcription factor as a novel regulator of drug resistance in high grade PDAC cell lines. It was observed that silencing of PAX2 resulted in increased susceptibility of high grade PDAC cells to various chemotherapeutic drugs. Mechanistically, the study showed that PAX2 protein can bind and alter transcriptionally; expression of many ABC transporter genes in high grade PDAC cell lines. Overall, the study indicated that PAX2 significantly upregulated ABC family of genes resulting in drug resistance and poor survival in PDAC.

Associations of cytosine deaminase gene polymorphisms with effectiveness of gemcitabine/cisplatin chemotherapy in patients of Xinjiang Uyghur and Han nationality with non-small cell lung cancer

BACKGROUND

Cytidine deaminase (CDA) polymorphisms may affect the response to gemcitabine/cisplatin chemotherapy in patients with non-small cell lung cancer (NSCLC). This study is designed to investigate the associations of CDA-79A>C and 208G>A polymorphisms and gemcitabine/cisplatin chemotherapy effectiveness in Xinjiang Uyghur and Han patients.

METHODS

This prospective cohort study enrolled consecutive patients with stage IIIb/IV NSCLC administered gemcitabine/cisplatin chemotherapy at the First Affiliated Hospital, Medical College of Shihezi University and the First People's Hospital, Kashgar Region. CDA-A79C and CDA-G208A polymorphisms were detected by direct sequencing. Progression-free survival was analyzed by the Kaplan-Meier method. Associations of A79C and G208A polymorphisms with treatment effectiveness and progression-free survival were analyzed using logistic regression and multivariate Cox regression analyses. Subgroup analyses based on ethnicity were performed.

RESULTS

The study enrolled 120 patients. A79C and G208A polymorphisms followed the Hardy-Weinberg equilibrium. The frequencies of the AA, AC, and CC genotypes and the A and C alleles of A79C were 52.2%, 29.9%, 17.9%, 67.2%, and 32.8%, respectively, in Han patients and 75.4%, 18.9%, 5.7%, 84.9%, and 5.1%, respectively, in Uyghur patients. Uyghur patients had lower frequencies of A79C-AC/CC genotypes, A79C-C allele, G208A-GA genotype, and G208A-A allele (P<0.05). Compared with A79C-AA, the odds of ineffective chemotherapy were increased for A79C-AC (odds ratio [OR] 2.818; 95% confidence interval [95% CI] 1.031, 7.705; P=0.043) and A79C-CC (OR 9.864; 95% CI 1.232, 78.966; P=0.031). G208A polymorphisms did not influence chemotherapy effectiveness. Chemotherapy was more effective in Han patients than in Uyghur patients for A79C-AC and G208A-GG. Progression-free survival was longer for A79C-AA versus A79C-AC/CC (10 vs. 7 months, P=0.004) and G208A-GA/AA vs. G208A-AA (12 vs. 8 months, P=0.010). Polymorphisms of A79C (hazard ratio [HR] 1.617; 95% CI 1.009, 2.592; P=0.046) and G208A (HR 2.193; 95% CI 1.055, 4.557; P=0.035) were associated with progression-free survival.

CONCLUSION

For Uyghur and Han ethnic groups, A79C and G208A polymorphisms can be used as a promising biomarker for the chemotherapy efficacy and prognosis of NSCLC.

Cytoplasmic HuR Status Predicts Disease-free Survival in Resected Pancreatic Cancer: A Post-hoc Analysis From the International Phase III ESPAC-3 Clinical Trial

OBJECTIVES

We tested cytoplasmic HuR (cHuR) as a predictive marker for response to chemotherapy by examining tumor samples from the international European Study Group of Pancreatic Cancer-3 trial, in which patients with resected pancreatic ductal adenocarcinoma (PDA) received either gemcitabine (GEM) or 5-fluorouracil (5-FU) adjuvant monotherapy.

BACKGROUND

Previous studies have implicated the mRNA-binding protein, HuR (ELAVL1), as a predictive marker for PDA treatment response in the adjuvant setting. These studies were, however, based on small cohorts of patients outside of a clinical trial, or a clinical trial in which patients received multimodality therapy with concomitant radiation.

METHODS

Tissue samples from 379 patients with PDA enrolled in the European Study Group of Pancreatic Cancer-3 trial were immunolabeled with an anti-HuR antibody and scored for cHuR expression. Patients were dichotomized into groups of high versus low cHuR expression.

RESULTS

There was no association between cHuR expression and prognosis in the overall cohort [disease-free survival (DFS), P = 0.44; overall survival, P = 0.41). Median DFS for patients with high cHuR was significantly greater for patients treated with 5-FU compared to GEM [20.1 months, confidence interval (CI): 8.3-36.4 vs 10.9 months, CI: 7.5-14.2; P = 0.04]. Median DFS was similar between the treatment arms in patients with low cHuR (5-FU, 12.8 months, CI: 10.6-14.6 vs GEM, 12.9 months, CI: 11.2-15.4).

CONCLUSIONS

Patients with high cHuR-expressing tumors may benefit from 5-FU-based adjuvant therapy as compared to GEM, whereas those patients with low cHuR appear to have no survival advantage with GEM compared with 5-FU. Further studies are needed to validate HuR as a biomarker in both future monotherapy and multiagent regimens.

Severe acute toxicity following gemcitabine administration: A report of four cases with cytidine deaminase polymorphisms evaluation

Gemcitabine (GCB) is a pyrimidine antimetabolite widely used in various solid tumors as a single agent or as a component of multidrug regimens. In the majority of patients, GCB is well tolerated, however life-threatening complications occasionally occur. The current report presents four cases of severe acute toxicity, which included two that were fatal, following administration of GCB alone or in combination with cisplatin. Of the four cases, in one, a Naranjo Adverse Drug Reaction Probability Score was definite, in two, probable and in one possible. To determine the potential causes of these toxicities, polymorphic variants of cytidine deaminase, the primary enzyme involved in the hepatic metabolism of GCB, were assessed. The homogeneous c.435TT variant was detected in one patient and a heterozygotic c.435CT variant in two, one of whom additionally harbored a heterozygotic c.79AC variant.

Cytidine Deaminase Deficiency Reveals New Therapeutic Opportunities against Cancer

Purpose: One of the main challenges in cancer therapy is the identification of molecular mechanisms mediating resistance or sensitivity to treatment. Cytidine deaminase (CDA) was reported to be downregulated in cells derived from patients with Bloom syndrome, a genetic disease associated with a strong predisposition to a wide range of cancers. The purpose of this study was to determine whether CDA deficiency could be associated with tumors from the general population and could constitute a predictive marker of susceptibility to antitumor drugs.Experimental Design: We analyzed CDA expression in silico, in large datasets for cancer cell lines and tumors and in various cancer cell lines and primary tumor tissues using IHC, PDXs, qRT-PCR, and Western blotting. We also studied the mechanism underlying CDA silencing and searched for molecules that might target specifically CDA-deficient tumor cells using in silico analysis coupled to classical cellular experimental approaches.Results: We found that CDA expression is downregulated in about 60% of cancer cells and tissues. We demonstrate that DNA methylation is a prevalent mechanism of CDA silencing in tumors. Finally, we show that CDA-deficient tumor cells can be specifically targeted with epigenetic treatments and with the anticancer drug aminoflavone.Conclusions: CDA expression status identifies new subgroups of cancers, and CDA deficiency appears to be a novel and relevant predictive marker of susceptibility to antitumor drugs, opening up new possibilities for treating cancer. Clin Cancer Res; 23(8); 2116-26. ©2016 AACR.

Personalized fludarabine dosing to reduce nonrelapse mortality in hematopoietic stem-cell transplant recipients receiving reduced intensity conditioning

Patients undergoing hematopoietic cell transplantation (HCT) with reduced intensity conditioning (RIC) commonly receive fludarabine. Higher exposure of F-ara-A, the active component of fludarabine, has been associated with a greater risk of nonrelapse mortality (NRM). We sought to develop a model for fludarabine dosing in adult HCT recipients that would allow for precise dose targeting and predict adverse clinical outcomes. We developed a pharmacokinetic model from 87 adults undergoing allogeneic RIC HCT that predicts F-ara-A population clearance (Clpop) accounting for ideal body weight and renal function. We then applied the developed model to an independent cohort of 240 patients to identify whether model predictions were associated with NRM and acute graft versus host disease (GVHD). Renal mechanisms accounted for 35.6% of total F-ara-A Clpop. In the independent cohort, the hazard ratio of NRM at day 100 was significantly higher in patients with predicted F-ara-A clearance (Clpred) <8.50 L/h (P < 0.01) and area under the curve (AUCpred) >6.00 μg × h/mL (P = 0.01). A lower Clpred was also associated with more NRM at month 6 (P = 0.01) and trended toward significance at 12 months (P = 0.05). In multivariate analysis, low fludarabine clearance trended toward higher risk of acute GVHD (P = 0.05). We developed a model that predicts an individual's systemic F-ara-A exposure accounting for kidney function and weight. This model may provide guidance in dosing especially in overweight individuals and those with altered kidney function.

Pharmacokinetics and pharmacogenetics of Gemcitabine as a mainstay in adult and pediatric oncology: an EORTC-PAMM perspective

Gemcitabine is an antimetabolite ranking among the most prescribed anticancer drugs worldwide. This nucleoside analog exerts its antiproliferative action after tumoral conversion into active triphosphorylated nucleotides interfering with DNA synthesis and targeting ribonucleotide reductase. Gemcitabine is a mainstay for treating pancreatic and lung cancers, alone or in combination with several cytotoxic drugs (nab-paclitaxel, cisplatin and oxaliplatin), and is an option in a variety of other solid or hematological cancers. Several determinants of response have been identified with gemcitabine, i.e., membrane transporters, activating and inactivating enzymes at the tumor level, or Hedgehog signaling pathway. More recent studies have investigated how germinal genetic polymorphisms affecting cytidine deaminase, the enzyme responsible for the liver disposition of gemcitabine, could act as well as a marker for clinical outcome (i.e., toxicity, efficacy) at the bedside. Besides, constant efforts have been made to develop alternative chemical derivatives or encapsulated forms of gemcitabine, as an attempt to improve its metabolism and pharmacokinetics profile. Overall, gemcitabine is a drug paradigmatic for constant searches of the scientific community to improve its administration through the development of personalized medicine in oncology.

Gemcitabine resistant pancreatic cancer cell lines acquire an invasive phenotype with collateral hypersensitivity to histone deacetylase inhibitors

Gemcitabine based treatment is currently a standard first line treatment for patients with advanced pancreatic cancer, however overall survival remains poor, and few options are available for patients that fail gemcitabine based therapy. To identify potential molecular targets in gemcitabine refractory pancreatic cancer, we developed a series of gemcitabine resistant (GR) cell lines. Initial drug exposure selected for an early resistant phenotype that was independent of drug metabolic pathways. Prolonged drug selection pressure after 16 weeks, led to an induction of cytidine deaminase (CDA) and enhanced drug detoxification. Cross resistance profiles demonstrate approximately 100-fold cross resistance to the pyrimidine nucleoside cytarabine, but no resistance to the same in class agents, azacytidine and decitabine. GR cell lines demonstrated a dose dependent collateral hypersensitivity to class I and II histone deacetylase (HDAC) inhibitors and decreased expression of 3 different global heterochromatin marks, as detected by H4K20me3, H3K9me3 and H3K27me3. Cell morphology of the drug resistant cell lines demonstrated a fibroblastic type appearance with loss of cell-cell junctions and an altered microarray expression pattern, using Gene Ontology (GO) annotation, consistent with progression to an invasive phenotype. Of particular note, the gemcitabine resistant cell lines displayed up to a 15 fold increase in invasive potential that directly correlates with the level of gemcitabine resistance. These findings suggest a mechanistic relationship between chemoresistance and metastatic potential in pancreatic carcinoma and provide evidence for molecular pathways that may be exploited to develop therapeutic strategies for refractory pancreatic cancer.

Cytidine deaminase polymorphisms and worse treatment response in normal karyotype AML

The cytidine deaminase (CDA) catalyzes the irreversible hydrolytic deamination of the cytarabine (AraC) into a 1-β-D-arabinofuranosyluracil (AraU), an inactive metabolite that plays a crucial role in lowering the amount of AraC, a key chemotherapeutic drug, in the treatment of patients with acute myeloid leukemia (AML). In this study, we hypothesized that CDA polymorphisms were associated with the AraC metabolism for AML treatment and/or related clinical phenotypes. We analyzed 16 polymorphisms of CDA among 50 normal karyotype AML (NK-AML) patients, 45 abnormal karyotype AML (AK-AML) patients and 241 normal controls (NC). Several polymorphisms and haplotypes, rs532545, rs2072671, rs471760, rs4655226, rs818194 and CDA-ht3, were found to have a strong correlation with NK-AML compared with NC and these polymorphisms also revealed strong linkage disequilibrium with each other. Among them, rs2072671 (79A>C), which is located in a coding region and the resultant amino acid change K27Q, showed significant associations with NK-AML compared with NC (P=0.009 and odds ratio=2.44 in the dominant model). The AC and CC genotypes of rs2072671 (79A>C) were significantly correlated with shorter overall survival rates (P=0.03, hazard ratio=1.84) and first complete remission duration (P=0.007, hazard ratio=3.24) compared with the AA genotype in the NK-AML patients. Our results indicate that rs2072671 in CDA may be an important prognostic marker in NK-AML patients.

Cytidine deaminase polymorphism predicts toxicity of gemcitabine-based chemotherapy

BACKGROUND

The aim of this study was to ascertain whether single nucleotide polymorphisms of cytidine deaminase (CDA), a key enzyme in the metabolism pathway of gemcitabine, could predict clinical outcomes of cancer patients with gemcitabine-based chemotherapy.

METHODS

We searched MEDLINE and EMBASE up to January 2013 to identify eligible studies. A rigorous quality assessment of eligible studies was conducted according to the Newcastle-Ottawa Quality Assessment Scale. For each included study, the overall survival (OS), overall response rate (ORR) and toxicities were extracted and pooled using random-effects model.

RESULTS

In total, data from 13 studies were included. CDA 208A>G and CDA 435C>T were not included in quantified synthesis due to limited data. CDA 79A>C polymorphism was not significantly associated with OS; however, patients carrying the variant CDA 79C allele were likely to have a poor survival, hazard ratio (HR)=1.03, 95% CI 0.957-1.27 (AC+CC vs. AA). CDA 79A>C polymorphism did not correlated with ORR, odds ratio (OR)=0.719, 95% CI 0.363-1.425 (AC+CC vs. AA). However, patients with the variant CDA 79C allele would experience more grade ≥ 3 leucopenia (OR=2.933, 95% CI 1.357-6.605) and tended to have more severe neutropenia (OR=1.313, 95% CI 0.157-10.981).

CONCLUSIONS

These results suggest that CDA 79A>C polymorphisms is a potential biomarker for toxicity of gemcitabine-based chemotherapy and a CDA testing before gemcitabine administration is preferred.

Role of cytidine deaminase in toxicity and efficacy of nucleosidic analogs

INTRODUCTION

Nucleosidic analogs such as pyrimidine and purine derivatives are mainstay in the field of treating cancers, both in adults and in children. All these drugs act as antimetabolite compounds, that is, they interfere with the ability of cancer cells to synthesize the nucleosides or the nucleotides necessary for proliferation and progression. As with most cytotoxics, maintaining patients in their therapeutic window is challenging, and predicting changes in drug exposure is critical to ensure an optimal efficacy/toxicity balance.

AREAS COVERED

Among the antimetabolites, a small but widely prescribed number of drugs (i.e., gemcitabine, capecitabine, cytarabine, azacytidine) share a same metabolic pattern driven by a liver enzyme, cytidine deaminase (CDA), coded by a gene displaying several genetic and epigenetic polymorphisms. Consequently, CDA activity is erratic, ranging from deficient to ultra-rapid deaminator patients, with subsequent impact on drug pharmacokinetics and pharmacodynamics eventually. This review provides an update on the variety of clinical studies and case-reports investigating on CDA status as a marker for clinical outcome in cancer patients treated with nucleosidic analogs.

EXPERT OPINION

Whereas sorting patients on the basis of their CDA genotype remains tricky because of unclear genotype-to-phenotype relationships, developing functional strategies (i.e., phenotype-based status determination) could help to use CDA status as a biomarker for developing adaptive dosing strategies with nucleosidic analogs.

dCK expression correlates with 5-fluorouracil efficacy and HuR cytoplasmic expression in pancreatic cancer: a dual-institutional follow-up with the RTOG 9704 trial

Deoxycytidine kinase (dCK) and human antigen R (HuR) have been associated with response to gemcitabine in small studies. The present study investigates the prognostic and predictive value of dCK and HuR expression levels for sensitivity to gemcitabine and 5-fluorouracil (5-FU) in a large phase III adjuvant trial with chemoradiation backbone in pancreatic ductal adenocarcinoma (PDA). The dCK and HuR expression levels were determined by immunohistochemistry on a tissue microarray of 165 resected PDAs from the Radiation Therapy Oncology Group (RTOG) 9704 trial. Association with overall survival (OS) and disease-free survival (DFS) status were analyzed using the log-rank test and the Cox proportional hazards model. Experiments with cultured PDA cells were performed to explore mechanisms linking dCK and HuR expression to drug sensitivity. dCK expression levels were associated with improved OS for all patients analyzed from RTOG 9704 (HR: 0.66, 95% CI [0.47-0.93], P = 0.015). In a subset analysis based on treatment arm, the effect was restricted to patients receiving 5-FU (HR: 0.53, 95% CI [0.33-0.85], P = 0.0078). Studies in cultured cells confirmed that dCK expression rendered cells more sensitive to 5-FU. HuR cytoplasmic expression was neither prognostic nor predictive of treatment response. Previous studies along with drug sensitivity and biochemical studies demonstrate that radiation interferes with HuR's regulatory effects on dCK, and could account for the negative findings herein based on the clinical study design (i.e., inclusion of radiation). Finally, we demonstrate that 5-FU can increase HuR function by enhancing HuR translocation from the nucleus to the cytoplasm, similar to the effect of gemcitabine in PDA cells. For the first time, in the pre-treatment tumor samples, dCK and HuR cytoplasmic expression were strongly correlated (chi-square P = 0.015). This dual-institutional follow up study, in a multi-institutional PDA randomized clinical trial, observed that dCK expression levels were prognostic and had predictive value for sensitivity to 5-FU.

A meta-analysis of gemcitabine biomarkers in patients with pancreaticobiliary cancers

OBJECTIVES

The objective of this study was to summarize all clinical studies evaluating the prognostic role of gemcitabine (GEM) metabolic genes in pancreaticobiliary (PB) cancer patients receiving GEM therapy in the neoadjuvant, adjuvant, or palliative settings.

METHODS

Meta-analyses were performed to calculate the pooled hazard ratios for each gene by each clinical outcome (overall survival [OS], disease-free survival [DFS], and progression-free survival) using a random-effects approach.

RESULTS

The search strategy identified 16 eligible studies, composed of 632 PB patients total, with moderate quality. Compared with low expression, pooled hazard ratios for OS of hENT1, dCK, RRM1, RRM2, and DPD were 0.37 (95% confidence interval [CI], 0.28-0.47), 0.40 (95% CI, 0.20-0.80), 2.21 (95% CI, 1.12-4.36), 2.13 (95% CI, 1.00-4.52), and 1.91 (95% CI, 1.16-3.17), respectively. A similar trend was observed for each of these biomarkers in DFS and progression-free survival prognostication. Subgroup analyses for hENT1 showed a comparable survival correlation in the adjuvant and palliative settings.

CONCLUSIONS

High expression of hENT1 in PB cancer patients receiving GEM-based adjuvant therapy is associated with improved OS and DFS and may be the best examined prognostic marker to date. Evidence for other biomarkers is limited by a small number of publications investigating these markers.

Pancreatic cancer - cost for overtreatment with gemcitabine

Gemcitabine has been the standard chemotherapeutic agent in pancreatic cancer. However, two-thirds of pancreatic tumors display low expression of human equilibrative nucleoside transporter 1 (hENT1), which mediates cellular entry of the drug, and do not respond to gemcitabine therapy. The objective was to determine the costs of gemcitabine overtreatment and the cost-effectiveness of hENT1 testing using a Swedish pancreatic cancer cohort.

MATERIAL AND METHODS

The study population included 87 patients that were diagnosed with pancreatic cancer during 2008-2010 at Skåne University Hospital, Lund. A detailed review of treatments, side effects and resource utilization was performed. The proportion of hENT1-low was estimated at two-thirds based on previous evaluations of tumor samples from the Radiation Therapy Oncology Group (RTOG) trial 9704, the German AIO Pancreatic Cancer Group (AIO-PK) trial 0104, the Low hENT1 and Adenocarcinoma of the Pancreas (LEAP) trial and the authors' own institution. The cost of the hENT1 test was estimated at €50-200.

RESULTS

Sixty patients received gemcitabine and the other 27 best supportive care. Drug administration and hospitalization were the main expenditures. Grade 3 and 4 toxicities occurred in 42%, the most common being neutropenia (18%). The hospital costs related to gemcitabine overtreatment amounted to €5358 per pancreatic cancer patient, corresponding to as much as one-third of the total treatment cost. The health economical costs amounted to €9449 per patient when including indirect costs. Using hENT1 testing to select patients for gemcitabine therapy would save €8.6 million in Sweden each year.

CONCLUSION

Total costs related to gemcitabine overtreatment were high. Individualizing gemcitabine treatment is cost-saving and would reduce unnecessary treatment-related toxicity.

Pancreatic cancer: why is it so hard to treat?

No common malignancy is as rapidly and inevitably fatal as pancreatic ductal adenocarcinoma (PDA). This grim fact has driven substantial research efforts into this disease in recent decades. Unfortunately, the investment has yet to result in a meaningful increase in 5-year survival. This has prompted many pancreatic cancer researchers and advocates to redouble their efforts, but also requires one to step back and ask why the previous efforts were lacking and to consider why pancreatic cancer is so difficult to treat. The difficulties are legion. PDA is characterized by an insidious clinical syndrome, but is rarely diagnosed at a time when surgical resection is feasible. We lack markers of early detection and screening programs remain unproven even in high risk populations. The location of the tumor in the retroperitoneum, the advanced age of patients, and the systemic effects of disease limit the options for local therapy. Chemotherapy may provide a small benefit, but most efforts to improve on the current regimens consistently and stubbornly fail in advanced clinical trials. The molecular and cellular features of ductal pancreatic tumors are aggressive and underlay multiple levels of therapeutic resistance. Non-cell-autonomous features including stromal proliferation, reduced vascular density and immune suppression also contribute to therapeutic resistance. Growing awareness of these the fundamental features of PDA has begun to guide ongoing research efforts. Clinical trials are now specifically targeting these tumor properties and actively focusing on the therapeutic implications of tumor stroma. As reviewed here, reflecting on the fundamental question of why pancreatic cancer is so difficult to treat is a necessary and informative exercise that will aid our efforts to improve patient outcomes. These efforts will lead to improvements in clinical trial design, expand our focus to include the molecular and histologic implications of novel treatment paradigms, and ultimately change the lives of our patients.

Systemic therapies for pancreatic cancer--the role of pharmacogenetics

Effective systemic treatment of pancreatic cancer remains a major challenge, with progress hampered by drug resistance and treatment related toxicities. Currently available cytotoxic agents as monotherapy or in combination have provided only a modest survival benefit for patients with advanced disease. Disappointing phase III results with gemcitabine-based combinations in patients with advanced pancreatic cancer might be related to poor efficacy of systemic therapies in unselected patients. Future research strategies should prioritize identification of predictive markers through pharmacogenetic investigations. The individualization of patient treatment through pharmacogenetics may help to improve outcome by maximizing efficacy whilst lowering toxicity. This review provides an update on the pharmacogenetics of pancreatic cancer treatment and its influence on treatment benefits and toxicity.

Systemic therapies for pancreatic cancer--the role of pharmacogenetics

Effective systemic treatment of pancreatic cancer remains a major challenge, with progress hampered by drug resistance and treatment related toxicities. Currently available cytotoxic agents as monotherapy or in combination have provided only a modest survival benefit for patients with advanced disease. Disappointing phase III results with gemcitabine-based combinations in patients with advanced pancreatic cancer might be related to poor efficacy of systemic therapies in unselected patients. Future research strategies should prioritize identification of predictive markers through pharmacogenetic investigations. The individualization of patient treatment through pharmacogenetics may help to improve outcome by maximizing efficacy whilst lowering toxicity. This review provides an update on the pharmacogenetics of pancreatic cancer treatment and its influence on treatment benefits and toxicity.

Overcoming nucleoside analog chemoresistance of pancreatic cancer: a therapeutic challenge

Clinical refractoriness to nucleoside analogs (e.g., gemcitabine, capecitabine) is a major scientific problem and is one of the main reasons underlying the extremely poor prognostic state of pancreatic cancer. The drugs' effects are suboptimal partly due to cellular mechanisms limiting their transport, activation, and overall efficacy. Nonetheless, novel therapeutic approaches are presently under study to circumvent nucleoside analog resistance in pancreatic cancer. With these new approaches come additional challenges to be addressed. This review describes the determinants of chemoresistance in the gemcitabine cytotoxicity pathways, provides an overview of investigational approaches for overcoming chemoresistance, and discusses new challenges presented. Understanding the future directions of the field may assist in the successful development of novel treatment strategies for enhancing chemotherapeutic efficacy in pancreatic cancer.

Genomics and pharmacogenomics of pancreatic adenocarcinoma

The last decade has brought significant advances in the development of molecularly targeted therapies for treatment of a variety of human malignancies. In contrast to other solid tumors, however, the impact of novel therapeutic strategies on clinical outcomes in patients with pancreas adenocarcinoma (PAC) has been limited to date. Gemcitabine was established as a standard of care for treatment of advanced PAC in 1997 based on an observed improvement in clinical benefit as adjudicated principally by pain scores and analgesic consumption, and demonstration of an overall survival (OS) benefit in a randomized comparison with 5-fluorouracil (5-FU). Since then, multiple agents targeting oncogenic signaling pathways and mediators of angiogenesis have failed to improve outcomes in phase III clinical trials when compared with gemcitabine monotherapy. An exception to this is the anti-epidermal growth factor receptor therapy erlotinib, which yielded a survival benefit in patients with advanced disease in combination with gemcitabine compared with gemcitabine alone, although this was a marginal incremental improvement for which the clinical significant has been heavily debated. More recently, the most significant therapeutic advance in PAC has come from the combination of several cytotoxic agents; infusional 5-FU, irinotecan and oxaliplatin. This combination chemotherapy regimen, known as FOLFIRINOX, improved survival in patients with an excellent functional status and stage IV disease by 4.3 months compared with gemcitabine alone. This improvement in survival did come at the cost expectedly of a significant increase in toxicities, including gastrointestinal and hematologic particularly. Other gemcitabine-based combination chemotherapy regimens including gemcitabine and platinum analogs and gemcitabine and capecitabine have consistently shown an increased response rate but no OS benefit in individual trials; albeit pooled and meta-analyses have indicated a survival benefit in good performance status patient for both these cytotoxic combinations. Accordingly, the 5-year survival for patients with PAC remains <5%, with an annual disease-specific mortality which approaches the incidence. The challenge remains therefore, to develop more effective systemic therapies against this challenging malignancy. Recent progress toward understanding the genetic events in the development of PAC, in combination with advances in the field of pharmacogenomics offer hope that we may build on achievements to-date to develop more effective therapeutic strategies for PAC in years to come.

Rapid allele-specific PCR method for CDA 79A>C (K27Q) genotyping: a useful pharmacogenetic tool and world-wide polymorphism distribution

BACKGROUND

The CDA 79A>C (K27Q, rs2072671) functional SNP has recently shown a crucial role in the pharmacogenetics of cytidine-based anticancer drugs widely administered to different subsets of patients. Current gold standard in screening for the CDA rs2072671 is the sequence-based genotyping method. Here we developed a novel, rapid Allele-Specific PCR method for CDA rs2072671 genotyping.

METHODS

DNA was extracted from 324 healthy individuals from two different populations (Italian and Han Chinese). CDA rs2072671 genotyping was performed by Allele-Specific PCR. Sequencing was performed to validate the test results. Results obtained from population screening were compared to that already available in HapMap and in the literature.

RESULTS

Samples analyzed were successfully genotyped and the results were confirmed by sequencing. Genotype distribution does not differ significantly from that previously reported for each relative ethnic group. Also, the world-wide distribution of the CDA rs2072671 SNP is reported. A striking difference is present among the main ethnicities (p=1.715×10(-77)), with CDA*27Q allele showing the lowest frequency in African group (9.7%) and the highest in Caucasians (35.9%).

CONCLUSION

This Allele-Specific PCR method is a useful tool in pharmacogenetics research and a valid and reliable alternative for CDA rs2072671 screening where sequencing or Real-Time PCR is not available.