Report of new haplotype for ABCC2 gene: rs17222723 and rs8187718 in cis

The association between statin use, genetic variation, and prostate cancer risk

BACKGROUND

The association between statin medication use and prostate cancer remains inconclusive. Evidence shows that genetic variation modifies lipid-lowering efficacy of statins, however, there are limited data on the pharmacogenomics of statins in prostate cancer chemoprevention.

METHODS

Clinical and germline data were extracted from the prostate biopsy database at the University Health Network, Toronto, Canada (1996-2014). A genome-wide association study (GWAS) and a custom array of 54 single nucleotide polymorphisms (SNPs) related to statin metabolism were performed. Using a case-control design, we examined the associations between statin use and overall and high-grade (Grade Group ≥2) prostate cancer risk. A case-only design was employed to explore interactions between candidate/GWAS SNPs and the statin-cancer association.

RESULTS

Among 3481 patients, 1104 (32%) were using statins at biopsy. Statin users were older and had higher body mass index, greater number of positive cores, and higher Gleason scores. In total, 2061 participants (59%) were diagnosed with prostate cancer, with 922 cases (45%) classified as high-grade. When adjusted for baseline characteristics, the use of statins was not associated with decreased risk of overall or high-grade prostate cancer. Two unique SNPs implicated in statin metabolism showed significant interaction with the statin-cancer association. In particular, statin users harboring the GG genotype (n = 668; 24%) of rs10276036 had significantly lower prostate cancer risk (HR 0.71, 95% CI 051-1.00). However, none of the SNPs achieved genome-wide significance.

CONCLUSIONS

In our study, statin use was not associated with either prostate cancer or high-grade prostate cancer risk. While one candidate SNP that influences statin metabolism may be associated with a lower cancer risk among statin users and thus warrants further study, neither this nor any other SNPs achieved genome-wide significance. Thus, our findings do not add evidence in support of a prostate cancer chemopreventive role for statins.

Association Between ABCG2, ABCB1, ABCC2 Efflux Transporter Single-Nucleotide Variants and Irinotecan Adverse Effects in Patients With Colorectal Cancer: A Real-Life Study

Among patients treated with irinotecan, homozygous carriers of the UGT1A1*28 allele are at increased risk for neutropenia, but UGT1A1 genotype alone does not account for irinotecan-induced toxicity. Our aim was to study the association between single-nucleotide variants in genes encoding for efflux transporters of irinotecan (ABCG2, ABCB1, and ABCC2) and toxicity in real life. The source population was a cohort of patients with colorectal cancer (CRC) in Northern Israel, who had undergone genome-wide association study. From the source population we chose the patients with CRC prescribed irinotecan, and a comparative cohort of patients with CRC treated with other anticancer systemic therapies. Using Clalit Health Services electronic medical records (including laboratory results) we ascertained hematological and gastrointestinal adverse effects and mortality, within 90 days of the first dose, as a composite outcome. There were 601 patients with CRC who received irinotecan, and 756 patients with CRC treated with other anticancer regimens. The minor allele in rs2231142 (ABCG2) was associated with lower incidence of the composite outcome (odds ratio (OR) = 0.54 (0.33, 0.91); P = 0.02) in irinotecan-treated patients with CRC, but not in patients with CRC treated with other regimens. ABCB1 rs1045642 and ABCC2 rs3740066 were not associated with the composite outcome. In a sensitivity analysis, adjusted for UGT1A1 status and for possible demographic and clinical confounders, adjusted OR was 0.56 (0.33, 0.94) for the association between rs2231142 (ABCG2) and the composite outcome. In conclusion, we describe a novel association between the minor allele of rs2231142 in the efflux transporter gene ABCG2 and protection against severe side effects in CRC patients treating with irinotecan.

New ABCC2 rs3740066 and rs2273697 Polymorphisms Identified in a Healthy Colombian Cohort

Multidrug resistance-associated proteins (MRP) 1 and 2 belong to the ABC (ATP-Binding Cassette) transporters. These transport proteins are involved in the removal of various drugs and xenobiotics, as well as in multiple physiological, pathological, and pharmacological processes. There is a strong correlation between different polymorphisms and their clinical implication in resistance to antiepileptic drugs, anticancer, and anti-infective agents. In our study, we evaluated exon regions of MRP1 (ABCC1)/MRP2 (ABCC2) in a Colombian cohort of healthy subjects to determine single nucleotide polymorphisms (SNPs) and to determine the allelic and genomic frequency. Results showed there are SNPs in our population that have been previously reported for both MRP1/ABCC1 (rs200647436, rs200624910, rs150214567) and MRP2/ABCC2 (rs2273697, rs3740066, rs142573385, rs17216212). Additionally, 13 new SNPs were identified. Evidence also shows a significant clinical correlation for polymorphisms rs3740066 and rs2273697 in the transport of multiple drugs, which suggests a genetic variability in regards to that reported in other populations.

Assessing the Risk of Drug-Induced Cholestasis Using Unbound Intrahepatic Concentrations

Inhibition of the bile salt export pump (BSEP) has been recognized as a key factor in the development of drug-induced cholestasis (DIC). The risk of DIC in humans has been previously assessed using in vitro BSEP inhibition data (IC50) and unbound systemic drug exposure under assumption of the "free drug hypothesis." This concept, however, is unlikely valid, as unbound intrahepatic drug concentrations are affected by active transport and metabolism. To investigate this hypothesis, we experimentally determined the in vitro liver-to-blood partition coefficients (Kpuu) for 18 drug compounds using the hepatic extended clearance model (ECM). In vitro-in vivo translatability of Kpuu values was verified for a subset of compounds in rat. Consequently, unbound intrahepatic concentrations were calculated from clinical exposure (systemic and hepatic inlet) and measured Kpuu data. Using these values, corresponding safety margins against BSEP IC50 values were determined and compared with the clinical incidence of DIC. Depending on the ECM class of a drug, in vitro Kpuu values deviated up to 14-fold from unity, and unbound intrahepatic concentrations were affected accordingly. The use of in vitro Kpuu-based safety margins allowed separation of clinical cholestasis frequency into three classes (no cholestasis, cholestasis in ≤2%, and cholestasis in >2% of subjects) for 17 out of 18 compounds. This assessment was significantly superior compared with using unbound extracellular concentrations as a surrogate for intrahepatic concentrations. Furthermore, the assessment of Kpuu according to ECM provides useful guidance for the quantitative evaluation of genetic and physiologic risk factors for the development of cholestasis.