CDA gene polymorphisms and enzyme activity: genotype–phenotype relationship in an Italian–Caucasian population

Genetic polymorphisms as potential pharmacogenetic biomarkers for platinum-based chemotherapy in non-small cell lung cancer

Platinum-based chemotherapy (PBC) is a widely used treatment for various solid tumors, including non-small cell lung cancer (NSCLC). However, its efficacy is often compromised by the emergence of drug resistance in patients. There is growing evidence that genetic variations may influence the susceptibility of NSCLC patients to develop resistance to PBC. Here, we provide a comprehensive overview of the mechanisms underlying platinum drug resistance and highlight the important role that genetic polymorphisms play in this process. This paper discussed the genetic variants that regulate DNA repair, cellular movement, drug transport, metabolic processing, and immune response, with a focus on their effects on response to PBC. The potential applications of these genetic polymorphisms as predictive indicators in clinical practice are explored, as are the challenges associated with their implementation.

Cytidine deaminase enzyme activity is a predictive biomarker in gemcitabine-treated cancer patients

BACKGROUND

Gemcitabine is a chemotherapeutic agent, widely used for the treatment of many types of cancer. Cytidine deaminase (CDA) enzyme plays an important role in the metabolism of gemcitabine. This study aimed to assess the power of serum CDA residual activity in predicting drug efficacy and toxicity in gemcitabine-treated cancer patients.

METHODS

This prospective observational study enrolled 63 patients with different types of malignancies who received gemcitabine chemotherapy between May 2019 and January 2022. Blood samples were obtained before the initiation of chemotherapy and serum CDA residual activity was determined using a modification of the Berthelot assay. The patients were followed up for at least 12 months up to 41 months. Overall survival was recorded and treatment-related toxicities were documented according to National Cancer Institute Common Terminology Criteria.

RESULTS

Kaplan-Meier analysis showed that patients with a lower than median CDA value (≤ 8.06 U/mg protein) had a significantly longer survival compared to patients with higher CDA values (> 8.06 U/mg, P ˂ 0.005). Among several potentially involved factors, a significant association between CDA activity and overall survival was observed in univariate analysis (HR = 4.219, 95% CI 1.40-12.74, P = 0.011). On the other hand, the rate of anemia was significantly higher in low-CDA patients compared to high-CDA individuals (P < 0.05).

CONCLUSION

These findings suggest that CDA activity could be a promising biomarker to predict survival and the occurrence of anemia in cancer patients treated with gemcitabine.

Cytidine deaminase status as a marker of response to azacytidine treatment in MDS and AML patients

Azacitidine (Aza) is a mainstay of treatment for patients with acute myeloid leukaemia (AML) ineligible for induction chemotherapy and other high-risk myelodysplastic syndromes (MDS). Only half of patients respond, and almost all will eventually relapse. There are no predictive markers of response to Aza. Aza is detoxified in the liver by cytidine deaminase (CDA). Here, we investigated the association between CDA phenotype, toxicity and efficacy of Aza in real-world adult patients. Median overall survival (OS) was 15 months and 13 months in AML and high-risk MDS patients respectively. In addition, our data suggest that delaying Aza treatment was not associated with lack of efficacy and should not be considered a signal to switch to an alternative treatment. Half of the patients had deficient CDA activity (i.e. <2 UA/mg), with a lower proportion of deficient patients in MDS patients (34%) compared to AML patients (67%). In MDS patients, CDA deficiency correlated with longer landmark OS (14 vs. 8 months; p = 0.03), but not in AML patients. Taken together, our data suggest that CDA is an independent covariate and may therefore be a marker for predicting clinical outcome in MDS patients treated with Aza.

Association of Single-Nucleotide Polymorphisms in Capecitabine Bioactivation Pathway with Adjuvant Therapy Safety in Colorectal Cancer Patients

Capecitabine, an oral prodrug of 5-fluorouracil (5-FU), is part of the standard treatment of colorectal cancer (CRC). Severe adverse dose limiting reactions that impair treatment safety and lead to treatment suspension remain a relevant concern. Single-nucleotide polymorphisms (SNPs) in genes involved in the activation of capecitabine may alter the bioavailability of 5-FU and thereby affect therapy outcomes. The aim of this study was to evaluate the association of these SNPs with severe toxicity and treatment suspension in patients with CRC treated with capecitabine-based therapy. An ambispective cohort study was conducted, including 161 patients with CRC. SNPs were analyzed using real-time PCR with TaqMan® probes. Toxicity was assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events v.5.0. CES1 rs71647871-A was associated with a severe hand-foot syndrome (p = 0.030; OR = 11.92; 95% CI = 1.46-73.47; GG vs. A). CDA rs1048977-CC (p = 0.030; OR = 2.30; 95% CI 1.09-5.00; T vs. CC) and capecitabine monotherapy (p = 0.003; OR = 3.13; 95% CI 1.49-6.81) were associated with treatment suspension due to toxicity. SNPs CES1 rs71647871 and CDA rs1048977 may act as potential predictive biomarkers of safety in patients with CRC under capecitabine-based adjuvant therapy.

Capecitabine-induced hand-foot syndrome: A pharmacogenetic study beyond DPYD

AIM OF THE STUDY

Occurrence of hand-foot syndrome (HFS) during capecitabine treatment often results in treatment interruptions (26 %) or treatment discontinuation (17 %), and can severely decrease quality of life. In this study, we investigated whether single nucleotide polymorphisms (SNPs) in genes involved in capecitabine metabolism - other than DPYD - are associated with an increased risk for capecitabine-induced HFS.

METHODS

Patients treated with capecitabine according to standard of care were enrolled after providing written informed consent for genotyping purposes. Prospectively collected blood samples were used to extract genomic DNA, which was subsequently genotyped for SNPs in CES1, CES2 and CDA. SNPs and clinical baseline factors that were univariably associated with HFS with P ≤ 0.10, were tested in a multivariable model using logistic regression.

RESULTS

Of the 446 patients eligible for analysis, 146 (32.7 %) developed HFS, of whom 77 patients (17.3 %) experienced HFS ≥ grade 2. In the multivariable model, CES1 1165-33 C>A (rs2244613, minor allele frequency 19 %) and CDA 266 + 242 A>G (rs10916825, minor allele frequency 35 %) variant allele carriers were at higher risk of HFS ≥ grade 2 (OR 1.888; 95 %CI 1.075-3.315; P = 0.027 and OR 1.865; 95 %CI 1.087-3.200; P = 0.024, respectively).

CONCLUSIONS

We showed that CES1 1165-33 C>A and CDA 266 + 242 A>G are significantly associated with HFS grade 2 and grade 3 in patients treated with capecitabine. Prospective studies should assess whether this increased risk can be mitigated in carriers of these SNPs, when pre-emptive genotyping is being followed by dose adjustment or by alternative treatment by a fluoropyrimidine that is not substrate to CES1, such as S1.

5'-nucleotidase, cytosolic ii genotype and clinical outcome in patients with acute myeloid leukemia with intermediate-risk cytogenetics

Acute myeloid leukemia (AML) is a complex disease, and its treatment needs to be adjusted to the risk, which is conferred by cytogenetics and molecular markers. Cytarabine is the main drug to treat AML, and it has been suggested that the genotype of cytarabine metabolizing enzymes may have a prognostic relevance in AML. Here we report the association between the 5'-nucleotidase, cytosolic II (NT5C2) rs10883841, cytidine deaminase (CDA) rs2072671 and rs532545 genotypes and the clinical outcome of 477 intermediate-risk cytogenetic AML patients receiving cytarabine-based chemotherapy. Patients younger than 50 years old with the NT5C2 rs10883841 AA genotype had lower overall survival (OS) (p: 0.003; HR 2.16, 95%CI 1.29 - 3.61) and lower disease-free survival (DFS) (p: 0.002; HR 2.45, 95%CI 1.41 - 4.27), associated to a higher relapse incidence (p: 0.010; HR 2.23, 95%CI 1.21 - 4.12). Interestingly, subgroup analysis showed that the negative effect of the NT5C2 rs10883841 AA genotype was detected in all subgroups except in patients with nucleophosmin mutation without high ratio FLT-3 internal tandem duplication. CDA polymorphisms were associated with the complete remission rate after induction chemotherapy, without influencing OS. Further studies are warranted to determine whether this pharmacogenomic approach may be helpful to individualize AML treatment.

Response and Toxicity to Cytarabine Therapy in Leukemia and Lymphoma: From Dose Puzzle to Pharmacogenomic Biomarkers

Simple Summary

In this review, the authors propose a crosswise examination of cytarabine-related issues ranging from the spectrum of clinical activity and severe toxicities, through updated cellular pharmacology and drug formulations, to the genetic variants associated with drug-induced phenotypes. Cytarabine (cytosine arabinoside; Ara-C) in multiagent chemotherapy regimens is often used for leukemia or lymphoma treatments, as well as neoplastic meningitis. Chemotherapy regimens can induce a suboptimal clinical outcome in a fraction of patients. The individual variability in clinical response to Leukemia & Lymphoma treatments among patients appears to be associated with intracellular accumulation of Ara-CTP due to genetic variants related to metabolic enzymes. The review provides exhaustive information on the effects of Ara-C-based therapies, the adverse drug reaction will also be provided including bone pain, ocular toxicity (corneal pain, keratoconjunctivitis, and blurred vision), maculopapular rash, and occasional chest pain. Evidence for predicting the response to cytarabine-based treatments will be highlighted, pointing at their significant impact on the routine management of blood cancers.

Abstract

Cytarabine is a pyrimidine nucleoside analog, commonly used in multiagent chemotherapy regimens for the treatment of leukemia and lymphoma, as well as for neoplastic meningitis. Ara-C-based chemotherapy regimens can induce a suboptimal clinical outcome in a fraction of patients. Several studies suggest that the individual variability in clinical response to Leukemia & Lymphoma treatments among patients, underlying either Ara-C mechanism resistance or toxicity, appears to be associated with the intracellular accumulation and retention of Ara-CTP due to genetic variants related to metabolic enzymes. Herein, we reported (a) the latest Pharmacogenomics biomarkers associated with the response to cytarabine and (b) the new drug formulations with optimized pharmacokinetics. The purpose of this review is to provide readers with detailed and comprehensive information on the effects of Ara-C-based therapies, from biological to clinical practice, maintaining high the interest of both researcher and clinical hematologist. This review could help clinicians in predicting the response to cytarabine-based treatments.

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.

The Emerging Role of Cytidine Deaminase in Human Diseases: A New Opportunity for Therapy?

The recycling activity of cytidine deaminase (CDA) within the pyrimidine salvage pathway is essential to DNA and RNA synthesis. As such, CDA deficiency can lead to replicative stress, notably in Bloom syndrome. Alternatively, CDA also can deaminate cytidine and deoxycytidine analog-based therapies, such as gemcitabine. Thus, CDA overexpression is often associated with lower systemic, chemotherapy-related, adverse effects but also with resistance to treatment. Considering the increasing interest of CDA in cancer chemoresistance, the aims of this review are to describe CDA structure, regulation of expression, and activity, and to report the therapeutic strategies based on CDA expression that recently emerged for tumor treatment.

Determinants of the interindividual variability in serum cytidine deaminase activity of patients with solid tumours

AIMS

Cytidine deaminase (CDA) activity in cancer patients' serum has been proposed as a predictive biomarker for efficacy and toxicity of nucleoside analogues. However, discrepant results about its predictive value have been reported due to the high interindividual variability in CDA activity. This study aimed at identifying determinants of this interindividual variability.

METHODS

From December 2014 to November 2015, 183 patients were prospectively included. Serum CDA activity, biological and clinical characteristics as well as five common single nucleotide polymorphisms (SNPs) in the CDA gene (c.-451C > T, c.-92A > G, c.-33_-31delC, c.79A > C, c.435 T > C) were analysed. Associations between clinical characteristics, pharmacogenetic variants and CDA activity were univariately tested. P < 0.1-candidate variables were analysed through a multivariate analysis. The association between CDA activity and toxicity was assessed for the 56 gemcitabine-treated patients. Intraindividual variability in CDA activity was explored in six pancreatic cancer patients treated with gemcitabine.

RESULTS

Median CDA activity was 3.97 U mg^-1 (range 1.53-15.49 U mg^-1 ). A univariate analysis showed that CDA activity was statistically associated with Eastern Cooperative Oncology Group performance status, mild or severe malnutrition, inflammatory syndrome, leucocyte count, neutrophil count, albumin, C-reactive protein and -c.-33_-31delC single nucleotide polymorphism. A multivariate analysis identified that only neutrophil count (P < 0.0001) and severe malnutrition (P = 0.0278) were independently associated with CDA activity. Low CDA activity (<2 U mg^-1 ) was not statistically associated with severe gemcitabine-related toxicities (P = 0.16). A decrease in CDA activity was observed during the longitudinal follow-up of six pancreatic cancer patients treated with gemcitabine (P = 0.03).

CONCLUSIONS

These results suggest that neutrophil count and malnutrition should be considered for the interpretation of pretherapeutic CDA activity.

CDA gene silencing regulated the proliferation and apoptosis of chronic myeloid leukemia K562 cells

Background

As a disease of hematopoietic stem cell, chronic myeloid leukemia (CML) possesses unique biological and clinical features. However, the biologic mechanism underlying its development remains poorly understood. Thus, the objective of the present study is to discuss the effect of cytidine deaminase (CDA) gene silencing on the apoptosis and proliferation of CML K562 cells.

Methods

CDA mRNA expression was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and enzymatic activity of CDA was measured by a nuclide liquid scintillation method. RT-qPCR and Western blot analysis were used to detect CDA mRNA and protein expression. Cell proliferation, apoptosis and cell cycle were measured by CCK-8 assay and flow cytometry. The expression of proteins relevant to cell proliferation, apoptosis and cell cycle was measured by Western blot analysis. Tumor xenografts were implanted in nude mice to verify the effect of CDA silencing on tumor growth in vivo.

Results

CML and AL patients showed increased mRNA expression and enzymatic activity of CDA. Compared with the blank group, the mRNA and protein expression of CDA in the shRNA-1 and shRNA-2 groups decreased significantly. As a result, the proliferation of K562 cells was inhibited after CDA silencing and the cells were mainly arrested in S and G2 phases, while the apoptosis rate of these cells was increased. In addition, CDA gene silencing in K562 cells led to down-regulated p-ERK1/2, t-AKT, p-AKT and BCL-2 expression and up-regulated expression of P21, Bax, cleaved caspase-3/total caspase-3 and cleaved PARP/total PARP. Finally, CDA gene silencing inhibited tumor growth.

Conclusion

Our study demonstrated that CDA gene silencing could inhibit CML cell proliferation and induce cell apoptosis. Therefore, CDA gene silencing may become an effective target for the treatment of leukemia.

Host genetic profiling to increase drug safety in colorectal cancer from discovery to implementation

Adverse events affect the pharmacological treatment of approximately 90% of colorectal cancer (CRC) patients at any stage of the disease. Chemotherapy including fluoropyrimidines, irinotecan, and oxaliplatin is the cornerstone of the pharmacological treatment of CRC. The introduction of novel targeted agents, as anti-EGFR (i.e. cetuximab, panitumumab) and antiangiogenic (i.e. bevacizumab, ziv-aflibercept, regorafenib, and ramucirumab) molecules, into the oncologist's toolbox has led to significant improvements in the life expectancy of advanced CRC patients, but with a substantial increase in toxicity burden. In this respect, pharmacogenomics has largely been applied to the personalization of CRC chemotherapy, focusing mainly on the study of inhered polymorphisms in genes encoding phase I and II enzymes, ATP-binding cassette (ABC)/solute carrier (SLC) membrane transporters, proteins involved in DNA repair, folate pathway and immune response. These research efforts have led to the identification of some validated genetic markers of chemotherapy toxicity, for fluoropyrimidines and irinotecan. No validated genetic determinants of oxaliplatin-specific toxicity, as peripheral neuropathy, has thus far been established. The contribution of host genetic markers in predicting the toxicity associated with novel targeted agents' administration is still controversial due to the heterogeneity of published data. Pharmacogenomics guidelines have been published by some international scientific consortia such as the Clinical Pharmacogenomics Implementation Consortium (CPIC) and the Dutch Pharmacogenetics Working Group (DPWG) strongly suggesting a pre-treatment dose adjustment of irinotecan based on UGT1A1*28 genotype and of fluoropyrimidines based on some DPYD genetic variants, to increase treatment safety. However, these recommendations are still poorly applied at the patient's bedside. Several ongoing projects in the U.S. and Europe are currently evaluating how pharmacogenomics can be implemented successfully in daily clinical practice. The majority of drug-related adverse events are still unexplained, and a great deal of ongoing research is aimed at improving knowledge of the role of pharmacogenomics in increasing treatment safety. In this review, the issue of pre-treatment identification of CRC patients at risk of toxicity via the analysis of patients' genetic profiles is addressed. Available pharmacogenomics guidelines with ongoing efforts to implement them in clinical practice and new exploratory markers for clinical validation are described.

MiR-608 regulating the expression of ribonucleotide reductase M1 and cytidine deaminase is repressed through induced gemcitabine chemoresistance in pancreatic cancer cells

PURPOSE

Gemcitabine resistance is the main problem in pancreatic adenocarcinoma patients. Hence, we aimed to identify the correlation between expression of RRM1 and CDA as the resistance genes and their predicted targeting miR-608 in the resistant pancreatic cancer cell lines to gemcitabine.

METHODS

Dual luciferase assay was performed to determine whether both RRM1 and CDA are targeted by miR-608 in 293T and pancreatic cancer cell lines. AsPC-1 and MIA PaCa-2 cell lines became gradually resistant to gemcitabine by exposing to the increasing doses of gemcitabine. After RNA and miRNAs extraction and cDNA conversion, the expressions of RRM1, CDA and miR-608 in all cell lines were studied by quantitative PCR. Pre-miR-608 transfection to the cell lines was done by calcium phosphate method. MTT assay was performed for analyzing the chemo sensitivity of different cell lines to gemcitabine.

RESULTS

Luciferase assays showed that miR-608 targeted RRM1 and CDA genes in 293T, AsPC-1 and MIA PaCa-2 cell lines. Compared to parental cell line, resistant MIA PaCa-2 and AsPC-1 cells demonstrated increased expression of RRM1 and CDA. On the other hand the expression of miR-608 in resistant MIA PaCa-2 and AsPC-1 cells was lower than parental cells. Furthermore, transfection of MIA PaCa-2 and AsPC-1 cells by miR-608 lead to decreased expression of RRM1 and CDA and lowered viability of the cells in comparison with scrambled microRNA transfected cells.

CONCLUSION

During resistance induction in pancreatic cancer cells, miR-608 which is targeting RRM1 and CDA is downregulated which leads to upregulation of these genes.

Single-nucleotide polymorphisms in the genes of CES2, CDA and enzymatic activity of CDA for prediction of the efficacy of capecitabine-containing chemotherapy in patients with metastatic breast cancer

We examined whether genetic polymorphisms (SNPs) in the capecitabine activation pathway and CDA enzymatic activity were associated with prognosis, benefit from capecitabine-containing treatment or capecitabine-related toxicities. The study population comprised 188 metastatic breast cancer patients of the ATX trial (EudraCT 2006-006058-83) randomized for first-line paclitaxel and bevacizumab with (ATX) or without capecitabine (AT). Cumulative capecitabine dose until grade ≥2 hand-foot syndrome or until first dose reduction were toxicity endpoints. We genotyped CDA c.-451C>T (rs532545), CDA c.-33delC (rs3215400) and CES2 c.-806C>G (rs11075646). CDA activity in baseline serum was measured with a spectrophotometric assay and values were analyzed using a median cut-off or as continuous variable. CDA c.-33delC was prognostic for overall survival (OS) independent of hormone receptor status. For the predictive analysis, progression-free survival benefit from ATX over AT was observed in patients with a CDA c.-33del/del or del/insC genotype, a CDA c.-451CC or CT genotype, and a CES2 c.-806CC genotype compared with their counterparts. There was a higher response rate for ATX over AT in patients with a CDA c.-451CT or TT genotype. Patients with high CDA enzymatic activity had more benefit from capecitabine, while this was marginally observed in the CDA low group. Toxicity endpoints were not associated with any candidate markers. In conclusion, CDA c.-33delC was associated with OS. Since particular SNPs in CDA and CES2 were associated with benefit from the addition of capecitabine to AT, their predictive value should be explored in a higher number of patients.

Influence of cytarabine metabolic pathway polymorphisms in acute myeloid leukemia induction treatment

Cytarabine is considered the most effective chemotherapeutic option in acute myeloid leukemia (AML). The impact of 10 polymorphisms in cytarabine metabolic pathway genes were evaluated in 225 adult de novo AML patients. Variant alleles of DCK rs2306744 and CDA rs602950 showed higher complete remission (p = .024, p = .045), with lower survival rates for variant alleles of CDA rs2072671 (p = .015, p = .045, p = .032), rs3215400 (p = .033) and wild-type genotype of rs602950 (p = .039, .014). Induction death (p = .033) and lower survival rates (p = .021, p = .047) were correlated to RRM1 rs9937 variant allele. In addition, variant alleles of CDA rs532545 and rs602950 were related to skin toxicity (p = .031, p = .049) and mucositis to DCK rs2306744 minor allele (p = .046). Other toxicities associated to variant alleles were hepatotoxicity to NT5C2 rs11598702 (p = .032), lung toxicity (p = .031) and thrombocytopenia to DCK rs4694362 (p = .046). This study supports the interest of cytarabine pathway polymorphisms regarding efficacy and toxicity of AML therapy in a coherent integrated manner.

The role of pharmacogenetics in capecitabine efficacy and toxicity

Capecitabine is an oral prodrug of 5-fluorouracil (5-FU) and approved for treatment of various malignancies. Hereditary genetic variants may affect a drug's pharmacokinetics or pharmacodynamics and account for differences in treatment response and adverse events among patients. In this review we present the current knowledge on genetic variants, commonly single-nucleotide polymorphisms (SNPs), tested in cohorts of cancer patients and possibly useful for prediction of capecitabine efficacy or toxicity. Capecitabine is activated to 5-FU by CES, CDA and TYMP, of which SNPs in CDA and CES2 were found to be associated with efficacy and toxicity. In addition, variants in genes of the 5-FU metabolic pathway, including TYMS, MTHFR and DPYD also influenced capecitabine efficacy and toxicity. In particular, well-known SNPs in TYMS and DPYD as well as putative DPYD SNPs had an association with clinical outcome as well as adverse events. Inconsistent findings may be attributable to factors related to ethnic differences, sample size, study design, study endpoints, dosing schedule and the use of multiple agents. Of the SNPs described in this review, dose reduction of fluoropyrimidines based on the presence of DPYD variants ^*2A (rs3918290), ^*13 (rs55886062), -2846A>T (rs67376798) and -1236G>A/HapB3 (rs56038477) has already been recommended. Other variants merit further validation to establish their definite role in explanation of interindividual differences in the outcome of capecitabine-based therapy.

Variants in CDA and ABCB1 are predictors of capecitabine-related adverse reactions in colorectal cancer

Adverse reactions to capecitabine-based chemotherapy limit full administration of cytotoxic agents. Likewise, genetic variations associated with capecitabine-related adverse reactions are associated with controversial results and a low predictive value. Thus, more evidence on the role of these variations is needed. We evaluated the association between nine polymorphisms in MTHFR, CDA, TYMS, ABCB1, and ENOSF1 and adverse reactions, dose reductions, treatment delays, and overall toxicity in 239 colorectal cancer patients treated with capecitabine-based regimens. The ABCB1*1 haplotype was associated with a high risk of delay in administration or reduction in the dose of capecitabine, diarrhea, and overall toxicity. CDA rs2072671 A was associated with a high risk of overall toxicity. TYMS rs45445694 was associated with a high risk of delay in administration or reduction in the dose of capecitabine, HFS >1 and HFS >2. Finally, ENOSF1 rs2612091 was associated with HFS >1, but was a poorer predictor than TYMS rs45445694. A score based on ABCB1-CDA polymorphisms efficiently predicts patients at high risk of severe overall toxicity (PPV, 54%; sensitivity, 43%) in colorectal cancer patients treated with regimens containing capecitabine. Polymorphisms in ABCB1, CDA, ENOSF1,and TYMS could help to predict specific and overall severe adverse reactions to capecitabine.

The influence of cytidine deaminase -33delC polymorphism on treatment outcome with high-dose cytarabine in Chinese patients with relapsed acute myeloid leukaemia

WHAT IS KNOWN AND OBJECTIVE

Identification of biomarkers that could predict high-dose cytarabine (Ara-C) efficacy and toxicity is a key issue in individualized therapy. The aim of our study was to evaluate the influence of cytidine deaminase (CDA) single nucleotide polymorphisms (SNPs) -451G>A (rs532545), 435C>T (rs1048977) and -33delC (rs3215400) on treatment outcome in patients with relapsed acute myeloid leukaemia (AML) after high-dose Ara-C chemotherapy.

METHODS

In total, 173 patients with relapsed AML, treated with high-dose Ara-C chemotherapy, were genotyped for three polymorphisms in CDA gene using the allele-specific matrix-assisted laser desorption/ionization time-of-flight mass spectrometry assays. Binary logistic regression was used to evaluate the influence of selected polymorphisms on tumour response and occurrence of treatment-related toxicity.

RESULTS AND DISCUSSION

The CC genotype at -33delC, a promoter polymorphism, increased the odds of overall response rate (odds ratio [OR] = 5·125; 95% confidence intervals (CI) = 2·446-10·74; P = 0·0008) and grade ≥3 infection toxicity incidence rate (OR = 3·572; 95% CI = 1·68-7·594; P = 0·003). In multivariable analysis, this polymorphism was a potential independent prognostic marker for the risk of overall response (P = 0·011), but not grade ≥3 infection toxicity incidence rate (P = 0·49). Two other polymorphisms, -451G>A and 435C>T, did not influence treatment outcome, including overall response rate, infection toxicity and nausea/vomiting, in patients with relapsed AML (P > 0·05).

WHAT IS NEW AND CONCLUSION

The findings suggest that CDA -33delC variant might be a potential marker for predicting treatment outcome in Chinese patients with relapsed AML given high-dose cytarabine chemotherapy.

Role of Genetic Polymorphisms of Deoxycytidine Kinase and Cytidine Deaminase to Predict Risk of Death in Children with Acute Myeloid Leukemia

Cytarabine is one of the most effective antineoplastic agents among those used for the treatment of acute myeloid leukemia. However, some patients develop resistance and/or severe side effects to the drug, which may interfere with the efficacy of the treatment. The polymorphisms of some Ara-C metabolizing enzymes seem to affect outcome and toxicity in AML patients receiving cytarabine. We conducted this study in a cohort of Mexican pediatric patients with AML to investigate whether the polymorphisms of the deoxycytidine kinase and cytidine deaminase enzymes are implicated in clinical response and toxicity. Bone marrow and/or peripheral blood samples obtained at diagnosis from 27 previously untreated pediatric patients with de novo AML were processed for genotyping and in vitro chemosensitivity assay, and we analyzed the impact of genotypes and in vitro sensitivity on disease outcome and toxicity. In the multivariate Cox regression analysis, we found that age at diagnosis, wild-type genotype of the CDA A79C polymorphism, and wild-type genotype of the dCK C360G polymorphism were the most significant prognostic factors for predicting the risk of death.