Associations between CYP2A6 polymorphisms and outcomes of adjuvant S-1 chemotherapy in patients with curatively resected gastric cancer

PharmVar GeneFocus: CYP2A6

The Pharmacogene Variation Consortium (PharmVar) provides nomenclature for the human CYP2A gene locus containing the highly polymorphic CYP2A6 gene. CYP2A6 plays a role in the metabolism of nicotine and various drugs. Thus, genetic variation can substantially contribute to the function of this enzyme and associated efficacy and safety. This GeneFocus provides an overview of the clinical significance of CYP2A6, including its genetic variation and function. We also highlight and discuss caveats in the identification and characterization of allelic variation of this complex pharmacogene, a prerequisite for accurate genotype determination and prediction of phenotype status.

Impact of CYP2A6 Gene Polymorphism on the Efficacy and Safety of S-1 Therapy in Patients with Gastric Cancer: A Systematic Review and Meta-Analysis

INTRODUCTION

The relationship of CYP2A6 polymorphisms with S-1 therapy outcomes in gastric cancer is unclear. This review aimed to assess the association between CYP2A6 gene polymorphisms (CYP2A6*4, *7, *9, *10) and S-1 therapy outcomes in gastric cancer, aiming to identify predictive markers for S-1 efficacy and adverse reactions.

METHODS

We searched seven databases, using random or fixed-effect models to calculate hazard ratio (HR) and 95% confidence interval (CI) based on study heterogeneity.

RESULTS

A total of 1,143 articles were retrieved from multiple online databases as of March 28, 2023. After screening, seven articles containing seven investigations were included in the meta-analysis. Our results revealed a significant association between the CYP2A6 polymorphism site and the overall survival (OS) of variant/variant group (V/V) patients compared to wild-type/wild-type (W/W) or wild-type/variant (W/V) patients (HR = 2.73, 95% CI: 1.45-5.14, p = 0.002). S-1 was more beneficial for W/W or W/V patients than V/V patients in terms of progression-free survival (PFS) (HR = 3.15, 95% CI: 1.47-6.75, p = 0.003). There was no association between CYP2A6 polymorphism and hematological adverse reactions (OR = 0.52, 95% CI: 0.23-1.15, p = 0.104).

CONCLUSION

CYP2A6 polymorphisms correlate with S-1 efficacy (OS and PFS) in gastric cancer, suggesting their potential as predictive markers. However, the generalizability of findings is limited by the small number of studies from Eastern countries and variations in chemotherapy regimens and detection methods. Further, large-scale studies are needed to confirm these associations.

Pharmacogenomic-guided dosing of fluoropyrimidines beyond DPYD: time for a polygenic algorithm?

Fluoropyrimidines are chemotherapeutic agents widely used for the treatment of various solid tumors. Commonly prescribed FPs include 5-fluorouracil (5-FU) and its oral prodrugs capecitabine (CAP) and tegafur. Bioconversion of 5-FU prodrugs to 5-FU and subsequent metabolic activation of 5-FU are required for the formation of fluorodeoxyuridine triphosphate (FdUTP) and fluorouridine triphosphate, the active nucleotides through which 5-FU exerts its antimetabolite actions. A significant proportion of FP-treated patients develop severe or life-threatening, even fatal, toxicity. It is well known that FP-induced toxicity is governed by genetic factors, with dihydropyrimidine dehydrogenase (DPYD), the rate limiting enzyme in 5-FU catabolism, being currently the cornerstone of FP pharmacogenomics. DPYD-based dosing guidelines exist to guide FP chemotherapy suggesting significant dose reductions in DPYD defective patients. Accumulated evidence shows that additional variations in other genes implicated in FP pharmacokinetics and pharmacodynamics increase risk for FP toxicity, therefore taking into account more gene variations in FP dosing guidelines holds promise to improve FP pharmacotherapy. In this review we describe the current knowledge on pharmacogenomics of FP-related genes, beyond DPYD, focusing on FP toxicity risk and genetic effects on FP dose reductions. We propose that in the future, FP dosing guidelines may be expanded to include a broader ethnicity-based genetic panel as well as gene*gene and gender*gene interactions towards safer FP prescription.

Transcriptional profiling and network pharmacology analysis identify the potential biomarkers from Chinese herbal formula Huosu Yangwei Formula treated gastric cancer in vivo

Huosu Yangwei (HSYW) Formula is a traditioanl Chinese herbal medicine that has been extensively used to treat chronic atrophic gastritis, precancerous lesions of gastric cancer and advanced gastric cancer. However, the effective compounds of HSYW and its related anti-tumor mechanisms are not completely understood. In the current study, 160 ingredients of HSYW were identified and 64 effective compounds were screened by the ADMET evaluation. Furthermore, 64 effective compounds and 2579 potential targets were mapped based on public databases. Animal experiments demonstrated that HSYW significantly inhibited tumor growth in vivo. Transcriptional profiles revealed that 81 mRNAs were differentially expressed in HSYW-treated N87-bearing Balb/c mice. Network pharmacology and PPI network showed that 12 core genes acted as potential markers to evaluate the curative effects of HSYW. Bioinformatics and qRT-PCR results suggested that HSYW might regulate the mRNA expression of DNAJB4, CALD, AKR1C1, CST1, CASP1, PREX1, SOCS3 and PRDM1 against tumor growth in N87-bearing Balb/c mice.

Polymorphism in cytochrome P4502A6 reduces the risk to head and neck cancer and modifies the treatment outcome

The present case-control study consisting of 1300 cases of head and neck squamous cell carcinoma (HNSCC) and the equal number of controls aimed to investigate the association of functionally important polymorphisms in cytochrome P4502A6 (CYP2A6*1B, CYP2A6*4C, CYP2A6*9-rs28399433) with HNSCC and the treatment response in cases receiving a combination of chemotherapy/radiotherapy (CT/RT). A significant decrease in risk to HNSCC was observed in the cases with deletion (CYP2A6*4B and CYP2A6*4C) or reduced activity genotypes (CYP2A6*9) of CYP2A6. This risk to HNSCC was further reduced significantly in tobacco users among the cases when compared to nontobacco users among the cases. The risk was also reduced to a slightly greater extent in alcohol users among the cases when compared to nonalcohol users among the cases. In contrast with decreased risk to HNSCC, almost half of the cases with variant genotypes of CYP2A6 (CYP2A6*1A/*4C+*1B/*4C+*4C/*4C and *9/*9) did not respond to the treatment. Likewise, the survival rate in cases receiving the treatment, after 55 months of follow-up was significantly lower in cases with deletion (6.3%) or reduced activity (11.9%) allele than in the cases with common alleles (41%). The present study has shown that CYP2A6 polymorphism significantly reduces the risk to HNSCC. Our data further suggested that CYP2A6 polymorphism may worsen the treatment outcome in the cases receiving CT/RT.

A Rare Case of Reversible Cardiac Dysfunction Associated with Tegafur/Gimeracil/Oteracil (S-1) Therapy

For the past 20 years, S-1 has been used in the treatment of many types of cancer. However, the clinical importance of myocardial dysfunction attributed to S-1 remains to be unclear. Thus, in this study, we report on a patient with myocardial dysfunction associated with S-1.S-1 postoperative chemotherapy for gastric cancer was included as a treatment for a 65-year-old man. On day 8, S-1 treatment was discontinued after the patient developed an oral ulcer. He was then admitted to the hospital because of diarrhea caused by S-1. At approximately the same time, he developed dyspnea, and his chest X-rays revealed perihilar vascular engorgement and cardiac enlargement. Although his brain natriuretic peptide was 595.8 pg/mL, troponin I and creatine phosphokinase were unremarkable. Electrocardiograms showed no change in atrial fibrillations or new ST-T wave change. As per his transthoracic echocardiogram, noted were expansion of the left ventricle, global hypokinesis, and reduced left ventricular ejection fraction (approximately 40%). The patient was then diagnosed with S-1-related myocardial dysfunction. Furosemide, human atrial natriuretic peptide, dobutamine, enalapril, spironolactone, and bisoprolol were administered. Thirteen days after being diagnosed with heart failure, his symptoms disappeared, his echocardiogram showed that the left ventricular ejection fraction had increased to 65%, and the cardiothoracic ratio improved to 47% according to his chest X-rays.S-1-related myocardial dysfunction may be reversible, as it can improve after approximately 2 weeks.

Molecular Bases of Mechanisms Accounting for Drug Resistance in Gastric Adenocarcinoma

Gastric adenocarcinoma (GAC) is the most common histological type of gastric cancer, the fifth according to the frequency and the third among the deadliest cancers. GAC high mortality is due to a combination of factors, such as silent evolution, late clinical presentation, underlying genetic heterogeneity, and effective mechanisms of chemoresistance (MOCs) that make the available antitumor drugs scarcely useful. MOCs include reduced drug uptake (MOC-1a), enhanced drug efflux (MOC-1b), low proportion of active agents in tumor cells due to impaired pro-drug activation or active drug inactivation (MOC-2), changes in molecular targets sensitive to anticancer drugs (MOC-3), enhanced ability of cancer cells to repair drug-induced DNA damage (MOC-4), decreased function of pro-apoptotic factors versus up-regulation of anti-apoptotic genes (MOC-5), changes in tumor cell microenvironment altering the response to anticancer agents (MOC-6), and phenotypic transformations, including epithelial-mesenchymal transition (EMT) and the appearance of stemness characteristics (MOC-7). This review summarizes updated information regarding the molecular bases accounting for these mechanisms and their impact on the lack of clinical response to the pharmacological treatment currently used in GAC. This knowledge is required to identify novel biomarkers to predict treatment failure and druggable targets, and to develop sensitizing strategies to overcome drug refractoriness in GAC.

Pharmacokinetic and bioequivalence study between two formulations of S-1 in Korean gastric cancer patients

Purpose

S-1 is an oral fluoropyrimidine anticancer drug consisting of the 5-fluorouracil prodrug tegafur combined with gimeracil and oteracil. The purpose of this study was to evaluate the pharmacokinetic (PK), bioequivalence, and safety of a newly developed generic formulation of S-1 compared with the branded reference formulation, in Korean gastric cancer patients.

Methods

This was a single-center, randomized, open-label, single-dose, two-treatment, two-way crossover study. Eligible subjects were randomly assigned in a 1:1 ratio to receive the test formulation or reference formulation, followed by a one-week washout period and administration of the alternate formulation. Serial blood samples were collected at 0 hrs (predose), 0.25, 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36, and 48 hrs after dosing in each period. The plasma concentrations of tegafur, 5-FU, gimeracil, and oteracil were analyzed using a validated liquid chromatography-tandem mass spectrometry method. The PK parameters were calculated using a non-compartmental method.

Results

In total, 29 subjects completed the study. All of the 90% confidence intervals (CIs) of the geometric mean ratios (GMRs) fell within the predetermined acceptance range. No serious adverse events were reported during the study.

Conclusion

The new S-1 formulation met the Korean regulatory requirement for bioequivalence. Both S-1 formulations were well tolerated in all subjects.

Clinical trial registry:https://cris.nih.go.kr CRIS KCT0003855.

Variation in CYP2A6 Activity and Personalized Medicine

The cytochrome P450 2A6 (CYP2A6) enzyme metabolizes several clinically relevant substrates, including nicotine-the primary psychoactive component in cigarette smoke. The gene that encodes the CYP2A6 enzyme is highly polymorphic, resulting in extensive interindividual variation in CYP2A6 enzyme activity and the rate of metabolism of nicotine and other CYP2A6 substrates including cotinine, tegafur, letrozole, efavirenz, valproic acid, pilocarpine, artemisinin, artesunate, SM-12502, caffeine, and tyrosol. CYP2A6 expression and activity are also impacted by non-genetic factors, including induction or inhibition by pharmacological, endogenous, and dietary substances, as well as age-related changes, or interactions with other hepatic enzymes, co-enzymes, and co-factors. As variation in CYP2A6 activity is associated with smoking behavior, smoking cessation, tobacco-related lung cancer risk, and with altered metabolism and resulting clinical responses for several therapeutics, CYP2A6 expression and enzyme activity is an important clinical consideration. This review will discuss sources of variation in CYP2A6 enzyme activity, with a focus on the impact of CYP2A6 genetic variation on metabolism of the CYP2A6 substrates.

CYP2A6 Polymorphisms Associate with Outcomes of S-1 Plus Oxaliplatin Chemotherapy in Chinese Gastric Cancer Patients

Gastric carcinoma is a heterogeneous malignant disease involving genetic factors. To identify predictive markers for gastric cancer treatment in Chinese patients, we evaluated the association between polymorphisms of the gene encoding cytochrome P450 2A6 (CYP2A6) and outcomes of S-1 plus oxaliplatin (SOX) chemotherapy treatment. Clinical data on 60 consecutive gastric cancer patients receiving SOX regimen were collected prospectively. We sequenced all exons of CYP2A6 and a total of 22 different polymorphisms were detected in the present study. Comprehensive analyses of these genetic polymorphisms were performed to determine their association with both safety and efficacy of SOX regimen. Our results showed that polymorphisms of CYP2A6 were associated with the safety and efficacy of SOX treatment. Among them, missense mutations CYP2A6 rs60823196 and rs138978736 could be possible risk factors (P < 0.05) for severe diarrhea induced by SOX, whereas CYP2A6 rs138978736 could be a conceivable predictor for overall survival of patients treated with SOX adjuvant chemotherapy. Further large-scale randomized prospective studies are warranted to confirm these findings.

Genetic susceptibility variants for lung cancer: replication study and assessment as expression quantitative trait loci

Many single nucleotide polymorphisms (SNPs) have been associated with lung cancer but lack confirmation and functional characterization. We retested the association of 56 candidate SNPs with lung adenocarcinoma risk and overall survival in a cohort of 823 Italian patients and 779 healthy controls, and assessed their function as expression quantitative trait loci (eQTLs). In the replication study, eight SNPs (rs401681, rs3019885, rs732765, rs2568494, rs16969968, rs6495309, rs11634351, and rs4105144) associated with lung adenocarcinoma risk and three (rs9557635, rs4105144, and rs735482) associated with survival. Five of these SNPs acted as cis-eQTLs, being associated with the transcription of IREB2 (rs2568494, rs16969968, rs11634351, rs6495309), PSMA4 (rs6495309) and ERCC1 (rs735482), out of 10,821 genes analyzed in lung. For these three genes, we obtained experimental evidence of differential allelic expression in lung tissue, pointing to the existence of in-cis genomic variants that regulate their transcription. These results suggest that these SNPs exert their effects on cancer risk/outcome through the modulation of mRNA levels of their target genes.