Effects of CYP2B6 genetic polymorphisms in patients receiving cyclophosphamide combination chemotherapy for breast cancer

Single nucleotide polymorphisms: impact on susceptibility to chemotherapy in patients with colorectal cancer

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in enzyme-coding genes play a role in susceptibility to anti-cancer therapy.

MATERIALS & METHODS

A prospective study was performed of the relationship between enzyme activity and treatment response, drug toxicity and hypersensitivity reactions in 51 patients with colorectal cancer treated with fluoropyrimidine-based chemotherapy. SNP analysis was performed in 22 enzyme-coding genes with a previously described role in treatment efficacy.

RESULTS

SLC6 and MTHR enzyme activity was related with rates of progressive disease, GSTP1 activity with anti-EGFR antibodies-related skin toxicity, CYP3A5 and MTHR with chemotherapy dose reduction, CYP2B6, IL10, MTHR and TYMS activity with the risk of drug hypersensitivity reactions.

CONCLUSION

Pharmacogenetics is a valuable predictive marker in oncology, related to chemotherapy treatment response, toxicity and hypersensitivity.

The Role of Pharmacogenetic-Based Pharmacokinetic Analysis in Precise Breast Cancer Treatment

Given the high prevalence of breast cancer and the diverse genetic backgrounds of patients, a growing body of research emphasizes the importance of pharmacogenetic-based pharmacokinetic analysis in optimizing treatment outcomes. The treatment of breast cancer involves multiple drugs whose metabolism and efficacy are influenced by individual genetic variations. Genetic polymorphisms in drug-metabolizing enzymes and transport proteins are crucial in the regulation of pharmacokinetics. Our review aims to investigate the opportunities and challenges of pharmacogenomic-based pharmacokinetic analysis as a precision medicine tool in breast cancer management.

Pharmacogenomics in Lebanon: current status, challenges and opportunities

Pharmacogenomics (PGx) research and applications are of utmost relevance in Lebanon considering its population genetic diversity. Moreover, as a country with regional leadership in medicine and higher education, Lebanon holds a strong potential in contributing to PGx research and clinical implementation. In this manuscript, we first review and evaluate the available PGx research conducted in Lebanon, then describe the current status of PGx practice in Lebanon while reflecting on the local and regional challenges, and highlighting areas for action, and opportunities to move forward. We specifically expand on the status of PGx at the American University of Beirut Faculty of Medicine and Medical Center as a case study and guide for the further development of local and regional comprehensive PGx research, teaching, and clinical implementation programs. We also delve into the status of PGx knowledge and education, and prospects for further advancement such as with online courses and certificates.

Association between CYP2B6 genetic variability and cyclophosphamide therapy in pediatric patients with neuroblastoma

Cyclophosphamide, an oxazaphosphorine prodrug is frequently used in treatment of neuroblastoma, which is one of the most prevalent solid organ malignancies in infants and young children. Cytochrome P450 2B6 (CYP2B6) is the major catalyst and CYP2C19 is the minor enzyme in bioactivation and inactivation pathways of cyclophosphamide. CYP-mediated metabolism may contribute to the variable pharmacokinetics of cyclophosphamide and its toxic byproducts leading to insufficient response to the therapy and development of clinically significant side effects. The aim of the study was to reveal the contribution of pharmacogenetic variability in CYP2B6 and CYP2C19 to the treatment efficacy and cyclophosphamide-induced side effects in pediatric neuroblastoma patients under cyclophosphamide therapy (N = 50). Cyclophosphamide-induced hematologic toxicities were pivotal in all patients, whereas only moderate hepatorenal toxicity was developed. The patients' CYP2B6 metabolizer phenotypes were associated with the occurrence of lymphopenia, thrombocytopenia, and monocytopenia as well as of liver injury, but not with kidney or urinary bladder (hemorrhagic cystitis) toxicities. Furthermore, the patients' age (< 1.5 years, P = 0.03) and female gender (P ≤ 0.02), but not CYP2B6 or CYP2C19 metabolizer phenotypes appeared as significant prognostic factors in treatment outcomes. Our results may contribute to a better understanding of the impact of CYP2B6 variability on cyclophosphamide-induced side effects.

Potential of Cytochrome P450, a Family of Xenobiotic Metabolizing Enzymes, in Cancer Therapy

Significance: Targeted cancer therapy with minimal off-target consequences has shown promise for some cancer types. Although cytochrome P450 (CYP) consists of 18 families, CYP1-4 families play key role in metabolizing xenobiotics and cancer drugs. This eventually affects the process of carcinogenesis, treatment outcomes, and cancer drug resistance. Differential overexpression of CYPs in transformed cells, together with phenotypic alterations in tumors, presents a potential for therapeutic intervention. Recent Advances: Recent advances in molecular tools and information technology have helped utilize CYPs as cancer targets. The precise expression in various tumors, X-ray crystal structures, improved understanding of the structure-activity relationship, and new approaches in the development of prodrugs have supported the ongoing efforts to develop CYP-based drugs with a better therapeutic index. Critical Issues: Narrow therapeutic index, off-target effects, drug resistance, and tumor heterogeneity limit the benefits of CYP-based conventional cancer therapies. In this review, we address the CYP1-4 families as druggable targets in cancer. An emphasis is given to the CYP expression, function, and the possible mechanisms that drive expression and activity in normal and transformed tissues. The strategies that inhibit or activate CYPs for therapeutic benefits are also discussed. Future Directions: Efforts are needed to develop more selective tools that will help comprehend molecular and metabolic alterations in tumor tissues with biological end-points in relation to CYPs. This will eventually translate to developing more specific CYP inhibitors/inducers. Antioxid. Redox Signal. 38, 853-876.

Cyclophosphamide bioactivation pharmacogenetics in breast cancer patients

PURPOSE

Genetic variation in the activation of the prodrug cyclophosphamide (CP) by cytochrome P450 (CYP) enzymes has been shown to influence outcomes. However, CYP are also subject to phenoconversion due to either the effects of comedications or cancer associated down-regulation of expression. The aim of this study was to assess the relationship between CP bioactivation with CYP2B6 and CYP2C19 genotype, as well as CYP2C19 phenotype, in breast cancer patients.

METHODS

CP and the active metabolite levels were assessed in breast cancer patients (n = 34) at cycle 1 and cycle 3 of treatment. Patients were genotyped for a series of SNP known to affect CYP2B6 and CYP2C19 function. The activity of CYP2C19 was also assessed using a probe drug.

RESULTS

We found a significant linear gene-dose relationship with CYP2B6 coding SNP and formation of 4-hydroxycyclophosphamide. A possible association with CYP2C19 null genotype at cycle 1 was obscured at cycle 3 due to the substantial intra-individual change in CP bioactivation on subsequent dosing.

CONCLUSION

Comedications may be the cause for this inter-occasion variation in bioactivation of cyclophosphamide and the ensuing phenoconversion may account for the conflicting reports in the literature about the relationship between CYP2C19 genotype and CP bioactivation pharmacokinetics. Trial registration ANZCTR363222 (6/11/2012, retrospectively registered).

Phenotyping Study of Cyclophosphamide 4-Hydroxylation in Malay Cancer Patients

Background

Cyclophosphamide (CP) is an anticancer alkylating group (nitrogen mustard) and a prodrug that will be metabolized to form its active metabolite, 4-hydroxycyclophosphamide (4-OHCP). The various enzymes involved in its bioactivation can cause a wide range of CP expression and activity among patients and ultimately affect the metabolism, efficacy and toxicity of this drug. The effectiveness of CP therapy can be determined by 4-OHCP level in dried blood spot (DBS).

Aim

The purpose of this study was to conduct the phenotyping of CP 4-hydroxylation rate in Malay cancer patients.

Methodology

Phenotyping study of CP 4-hydroxylation rate to 40 subjects of Malay cancer patients was done based on the value of its bioactivity ratio (4-OHCP to CP levels).

Results

The result shown the cyclophosphamide 4-hydroxylation rate of 80% (n=32) subjects as ultrarapid metabolizer (UM) and 20% (n=8) as poor metabolizer (PM).

Conclusion

Phenotyping study of CP 4-hydroxylation in Malay cancer patients can be conducted by quantifying CP bioactivity ratio (4-OHCP to CP level) in dried blood spot. In majority of Malay cancer patients, cyclophosphamide would be bioactivated through 4-hydroxylation in hepar rapidly as indicated by the high value of the bioactivity ratio or the increased CP clearance and 4-OHCP level.

Analysis of CYP450 gene allelic variants can predict ifosfamide toxicity in Mexican paediatric patients

Context: Ifosfamide (IFA) is an effective antineoplastic for solid tumours in children, although it is associated with high levels of systemic toxicity and causes death in some cases. Objective: The aim of this study was to determine whether the presence of certain allelic variants of genes CYP2B6, CYP2C9, CYP3A4 and CYP3A5 increases the risk of toxicity in children with solid tumours treated with ifosfamide.Materials and methods: A total of 131 DNA samples were genotyped by real-time polymerase chain reaction (RT-PCR) using TaqMan probes. Toxicity was assessed using WHO criteria, and survival analysis was performed using Kaplan-Meier curves.Results: The rs3745274 allelic variant in CYP2B6 was associated with haematological toxicity, affecting neutrophils; CYP3A4 variant rs2740574 was also associated with toxicity, affecting both leukocytes and neutrophils. Additionally, the CYP3A5 gene variant rs776746 was found to affect haemoglobin.Conclusions: Our results show that allelic variants rs3745274 (CYP2B6), rs2740574 (CYP34) and rs776746 (CYP3A5) increase the risk for high haematological toxicity.Clinical trial registration: 068/2013.

Toxicity and Pharmacogenomic Biomarkers in Breast Cancer Chemotherapy

Breast cancer (BC) is one of the most prevalent types of cancer worldwide with high morbidity and mortality rates. Treatment modalities include systemic therapy, in which chemotherapy is a major component in many cases. Several chemotherapeutic agents are used in combinations or as single agents with many adverse events occurring in variable frequencies. These events can be a significant barrier in completing the treatment regimens. Germline genomic variants are thought of as potential determinants in chemotherapy response and the development of side effects. Some pharmacogenomic studies were designed to explore germline variants that can be used as biomarkers for predicting developing toxicity or adverse events during chemotherapy in BC. In this review, we reassess and summarize the major findings of pharmacogenomic studies of chemotherapy toxicity during BC management. In addition, deficiencies hampering utilizing these findings and the potential targets of future research are emphasized. Main insufficiencies in toxicity pharmacogenomics studies originate from study design, sample limitations, heterogeneity of selected genes, variants, and toxicity definitions. With the advent of high throughput genotyping techniques, researchers are expected to explore the identified as well as the potential genetic biomarkers of toxicity and efficacy to improve BC management. However, to achieve this, the limitations of previous work should be evaluated and avoided to reach more conclusive and translatable evidence for personalizing BC chemotherapy.

The importance of both CYP2C19 and CYP2B6 germline variations in cyclophosphamide pharmacokinetics and clinical outcomes

Cyclophosphamide is an alkylating agent used in the treatment of solid and haematological malignancies and as an immunosuppressive agent. As a prodrug, it is dependent on bioactivation to the active phosphoramide mustard metabolite to elicit its therapeutic effect. This focused review will highlight the evidence for the role of germline pharmacogenetic variation in both plasma pharmacokinetics and clinical outcomes. There is a substantial indication from 13 pharmacokinetic and 17 therapeutic outcome studies, in contexts as diverse as haematological malignancy, breast cancer, systemic lupus erythematosus and myeloablation, that pharmacogenetic variation in both CYP2C19 and CYP2B6 influence the bioactivation of cyclophosphamide. An additional role for pharmacogenetic variation in ALDH1A1 has also been reported. Future studies should comprehensively assess these 3 pharmacogenes and undertake appropriate statistical analysis of gene-gene interactions to confirm these findings and may allow personalised treatment regimens.

CYP2J2∗7 Genotype Predicts Risk of Chemotherapy-Induced Hematologic Toxicity and Reduced Relative Dose Intensity in Ethiopian Breast Cancer Patients

Chemotherapy-induced hematologic toxicity is the primary reasons of dose reductions and/or delays, low relative dose intensity (RDI), and predicts anticancer response. We investigated the incidence and predictors of chemotherapy-induced hematologic toxicities and reduced RDI in Ethiopian breast cancer patients, and implication of pharmacogenetics variations. Breast cancer patients (n = 249) were enrolled prospectively to receive cyclophosphamide based chemotherapy. Hematological toxicity (neutropenia, anemia, and thrombocytopenia) were monitored throughout chemotherapy cycle. The primary and secondary outcomes were incidence of grade 3 or 4 toxicity and reduced RDI, respectively. CYP2B6^∗6, CYP3A5^∗3, CYP2C9 (^∗2,^∗3), CYP2C19 (^∗2,^∗3), CYP2J2^∗7, POR^∗28, and ABCB1 (rs3842) genotyping were done. Cox proportional hazard and logistic regression were used to estimate risk predictors of toxicity and reduced RDI, respectively. Majority (73.5%) of the patients were < 45 years of age. The incidence of grade 3 or 4 hematological toxicity was 51.0% (95% CI = 44.54–57.46%). Multivariate Cox proportional hazard regression indicated CYP2J2^∗7 genotype [Hazard ratio (HR) = 1.82; 95% CI = 1.14–2.90], pretreatment grade 1 leukopenia (HR = 2.75; 95% CI = 1.47–5.15) or grade 1 or 2 neutropenia (HR = 2.75; 95% CI = 1.73–4.35) as significant predictors of hematologic toxicities. The odds of having hematologic toxicities was lower in CYP2C9^∗2 or ^∗3 carriers (p = 0.024). The prevalence of reduced RDI was 56.6% (95% CI = 50.3–62.9%). Higher risk of reduced RDI was associated with CYP2J2^∗7 allele [Adjusted odds ratio (AOR) = 2.79; 95% CI = 1.21–6.46], BMI ≤ 18.4 kg/m² (AOR = 5.98; 95% CI = 1.36–26.23), baseline grade 1 leukopenia (AOR = 6.09; 95% CI = 1.24–29.98), and baseline neutropenia (AOR = 3.37; 95% CI = 1.41–8.05). The odds of receiving reduced RDI was lower in patients with CYP2B6 ^∗6/^∗6 genotype (AOR = 0.19; 95% CI = 0.06–0.77). We report high incidence of chemotherapy-induced hematological toxicities causing larger proportion of patients to receive reduced RDI in Ethiopian breast cancer patients. Patients carrying CYP2J2^∗7 allele and low baseline blood counts are at a higher risk for chemotherapy-induced hematologic toxicities and receiving reduced RDI, and may require prior support and close follow up during chemotherapy.

The Pharmacogenetics Laboratory of the Department of Pharmacology and Toxicology at the American University of Beirut Faculty of Medicine

The pharmacogenetics (PGx) laboratory at the Department of Pharmacology and Toxicology at the American University of Beirut Faculty of Medicine was established in October 2007. Several projects on the genetic polymorphisms of drug metabolizing enzymes and transporters with treatment of noncommunicable diseases such as cardiac diseases and cancers are ongoing. We have been applying the 'candidate gene' PGx approach, and recently started using higher throughput analyses. The more recent research projects are geared towards performing more extensive genotyping and including bigger and more representative population samples such as by developing research registries and prospectively following up patients. Furthermore, many technologies and research applications, such as next-generation sequencing and pharmacoepigenetics that complement and enhance PGx research and applications, are being actively pursued.

An integrated method for the identification of novel genes related to oral cancer

Cancer is a significant public health problem worldwide. Complete identification of genes related to one type of cancer facilitates earlier diagnosis and effective treatments. In this study, two widely used algorithms, the random walk with restart algorithm and the shortest path algorithm, were adopted to construct two parameterized computational methods, namely, an RWR-based method and an SP-based method; based on these methods, an integrated method was constructed for identifying novel disease genes. To validate the utility of the integrated method, data for oral cancer were used, on which the RWR-based and SP-based methods were trained, thereby building two optimal methods. The integrated method combining these optimal methods was further adopted to identify the novel genes of oral cancer. As a result, 85 novel genes were inferred, among which eleven genes (e.g., MYD88, FGFR2, NF-κBIA) were identified by both the RWR-based and SP-based methods, 70 genes (e.g., BMP4, IFNG, KITLG) were discovered only by the RWR-based method and four genes (L1R1, MCM6, NOG and CXCR3) were predicted only by the SP-based method. Extensive analyses indicate that several novel genes have strong associations with cancers, indicating the effectiveness of the integrated method for identifying disease genes.

Association of ABCB1 and SLC22A16 Gene Polymorphisms with Incidence of Doxorubicin-Induced Febrile Neutropenia: A Survey of Iranian Breast Cancer Patients

Breast cancer is the most common cancer in women worldwide. Doxorubicin-based chemotherapy is used to treat breast cancer patients; however, neutropenia is a common hematologic side effect and can be life-threatening. The ABCB1 and SLC22A16 genes encode proteins that are essential for doxorubicin transport. In this study, we explored the effect of 2 common polymorphisms in ABCB1 (rs10276036 C/T) and SLC22A16 (rs12210538 A/G) on the development of grade 3/4 febrile neutropenia in Iranian breast cancer patients. Our results showed no significant association between these polymorphisms and grade 3/4 febrile neutropenia; however, allele C of ABCB1 (rs10276036 C/T) (p = 0.315, OR = 1.500, 95% CI = 0.679–3.312) and allele A of SLC22A16 (rs12210538 A/G) (p = 0.110, OR = 2.984, 95% CI = 0.743–11.988) tended to have a greater association with grade 3/4 febrile neutropenia, whereas allele T of ABCB1 (rs10276036) (p = 0.130, OR = 0.515, 95% CI = 0.217–1.223) and allele G of SLC22A16 (rs12210538) (p = 0.548, OR = 0.786, 95% CI = 0.358–1.726) tended to protect against this condition. In addition to breast cancer, a statistically significant association was also observed between the development of grade 3/4 febrile neutropenia and other clinical manifestations such as stage IIIC cancer (p = 0.037) and other diseases (p = 0.026). Our results indicate that evaluation of the risk of grade 3/4 neutropenia development and consideration of molecular and clinical findings may be of value when screening for high-risk breast cancer patients.

The pharmacoepigenetics of drug metabolism and transport in breast cancer: review of the literature and in silico analysis

The focus of this manuscript is on DNA methylation and miRNA regulation of drug-metabolizing enzymes and drug transporters involved in the disposition of drugs commonly used in breast cancer. We start with a review of the available scant literature and follow with an in silico analysis of the CpG islands and miRNA binding sites of genes of interest. We make the case that there is room for further research to include more genes and miRNAs despite the extensive sharing of miRNA targets by candidate genes of interest. We also stress on the role of peripheral blood as a source of pharmacoepigenetic biomarkers, and point out the lack of toxicoepigenetic studies in breast cancer.

CYP2B6rs2279343 Is Associated with Improved Survival of Pediatric Rhabdomyosarcoma Treated with Cyclophosphamide

Background

Rhabdomyosarcoma (RMS) is a small round blue cell malignant tumor, representing 7% of childhood malignancies, and over 50% of all soft tissue sarcomas. Cyclophosphamide (CPA) is a prodrug and is the mainstay of RMS treatment. CYP2B6 is a highly polymorphic drug metabolizing enzyme involved in CPA bioactivation. The influence of CYP2B6 single nucleotide polymorphisms (SNPs) on the survival of RMS is still unknown.

Methods

We genotyped CYP2B6SNPs rs2279343, rs3745274, and rs3211371 by restriction fragment polymorphism (RFLP) after PCR amplification in a cohort of 73 pediatric RMS patients treated with CPA-based first line treatment. We then analyzed the association between those genotypes and survival outcome of RMS.

Results

The frequencies of CYP2B6 rs2279343, rs3745274, and rs3211371 were 63%, 45.2%, and 5.5%, respectively. There was no association between rs3745274, rs3211371 genotypes and survival outcomes of RMS. However, the carriers of at least one mutant allele CYP2B6rs2279343 had significantly longer event-free survival (p-value = 0.03).

Conclusion

Our results demonstrated that CYP2B6 rs2279343 may predict EFS in RMS patients and warrants future studies to clarify the pharmacogenetics of CPA in pediatrics. If validated, integration of genetic factors with clinical and molecular characteristics could be used for a composite algorithm to better stratify risk prior to treatment.

Incidence of Febrile Neutropenia in Korean Female Breast Cancer Patients Receiving Preoperative or Postoperative Doxorubicin/Cyclophosphamide Followed by Docetaxel Chemotherapy

PURPOSE

Doxorubicin/cyclophosphamide followed by docetaxel chemotherapy (AC-D) is an intermediate risk factor (incidence of 10%-20%) for febrile neutropenia (FN) in breast cancer. However, the reported incidence of FN while using this regimen was obtained mostly from Western breast cancer patients, with little data available from Asian patients. This study aimed to assess the incidence of FN in Korean breast cancer patients and to describe clinical variables related to FN.

METHODS

From September 2010 to February 2013, data from the Yonsei Cancer Center registry of breast cancer patients who received neoadjuvant or adjuvant chemotherapy with four cycles of AC-D (60 mg/m(2) doxorubicin, 600 mg/m(2) cyclophosphamide every 3 weeks for four cycles followed by 75 mg/m(2) or 100 mg/m(2) docetaxel every 3 weeks for four cycles) were analyzed. The incidence of FN, FN associated complications, dose reduction/delays, and relative dose intensity (RDI) were investigated.

RESULTS

Among the 254 patients reported to the registry, the FN incidence after AC-D chemotherapy was 29.5% (75/254), consisting of 25.2% (64/254) events during AC and 4.7% (12/254) during docetaxel chemotherapy. Dose reductions, delays, and RDI less than 85.0% during AC were observed in 16.5% (42/254), 19.5% (47/254), and 11.0% (28/254) of patients, respectively. Patients with FN events frequently experienced dose reduction/delays, which eventually led to a decreased RDI.

CONCLUSION

The incidence of FN during AC-D neoadjuvant or adjuvant chemotherapy was higher than expected in Korean breast cancer patients. Whether these patients should be classified as a high-risk group for FN warrants future prospective studies.