Influence of polymorphisms of ABCB1 and ABCC2 on mRNA and protein expression in normal and cancerous kidney cortex

Abstract

There is increasing evidence that polymorphisms of the adenosine 5 0 triphosphate membrane transporters ABCB1 (P-glycoprotein, MDR1) may affect expression and function, whereas less information is available about the impact of ABCC2 (multidrug resistance-associated protein (MRP2)) single-nucleotide polymorphisms . Particularly, their role in human kidney for drug elimination and in the etiology of renal cell carcinoma is poorly understood. ABCB1 and ABCC2 mRNA and protein expression levels were determined by real-time polymerase chain reaction or immunohistochemistry in kidney cancer and adjacent unaffected cortex tissue of 82 nephrectomized renal cell cancer (RCC) patients (63 clear-cell RCC (CCRCC), 19 non-CCRCC). The DNA of all patients was genotyped for ABCB1 À2352G4A, À692T4C, 2677G4T/A (Ala893Ser/Thr), and 3435C4T, and ABCC2 À24C4T, 1249G4A (Val417Ile) and 3972C4T. ABCB1 and ABCC2 were less expressed in CCRCC than in normal cortex on mRNA as well as on protein level. Although the overall genotype frequency distribution did not differ between the patients and a matched control group, ABCB1 2677T/ A and 3435T genotypes were associated with higher (P ¼ 0.02 and P ¼ 0.04) and ABCC2 À24 T with lower mRNA levels in normal tissues (0.03). The expression of ABCB1 and ABCC2 was not related to genetic variants in RCC tissue. In a reporter gene assay in HepG2 cells, the ABCC2 À24T construct showed an 18.7% reduced activity (P ¼ 0.003). In conclusion, ABCB1 and ABCC2 genotypes modulate the expression in the unaffected renal cortex of RCC patients, possibly contributing to inter-individual differences in drug and xenobiotics elimination. Their role in RCC cancer susceptibility or chemotherapy resistance needs further elucidation.

Impact of ABCC2 haplotypes on transcriptional and posttranscriptional gene regulation and function

“…However, in renal cell cancer tissue we also could not find a significant difference of À24C4T on ABCC2 mRNA expression. 5 Moreover, the findings of this study enlarge the understanding of the previously described reporter gene assay. Usually, reporter gene assays are conducted to investigate the influence of polymorphisms on promoter activity.…”

“…7,8 In vitro assays in HepG2 cells revealed a reduced reporter gene activity for the variant construct. 5,7 Interestingly, Caucasian kidney transplant recipients (n ¼ 154) exhibited a significant higher allele frequency for the variant À24T allele than recently investigated healthy Caucasian controls (n ¼ 374) (35.4% vs 18.3%). 9,10 The polymorphism 1249G4A that causes a valin to isoleucin exchange at position 417 in the ABCC2 protein is associated with an increased intestinal efflux and a significant decreased bioavailability of the b-blocker talinolol.…”

“…[2][3][4] In non-cancerous renal cortex tissue À24C4T showed a significant decreased mRNA expression. 5 Non-small lung cancer patients exhibiting the variant allele showed a higher response to irinotecan therapy suggesting a higher bioavailability for this anti-neoplastic drug. 6 Moreover, hepatotoxicity of diclofenac and herbal remedies was associated with À24T.…”

Pharmacogenomic associations in ABCB1 and CYP3A5 with acute kidney injury and chronic kidney disease after myeloablative hematopoietic cell transplantation

“…10,11 The in vivo significance of ABCB1 polymorphisms has been conflicting as to their functional effect on renal P-gp expression. [22][23][24] Since significant linkage exists in the ABCB1 gene, it is important to understand the role of ABCB1 haplotypes in pharmacogenomic association studies. We investigated the LD in our cohort of patients, and while strong LD was observed between SNPs, the degree of LD varied.…”

Fetal polymorphisms at the ABCB1-transporter gene locus are associated with susceptibility to non-syndromic oral cleft malformations

“…These findings are consistent with previous studies reporting the rs2032582 and rs1045642 T-alleles were associated with lower expression of ABCB1 in term placentas. [27][28][29] In contrast, other studies have reported higher levels of ABCB1 mRNA expression in kidney 30 and heart 31 tissues of carriers of rs2032582 T-and A-alleles compared with G-allele carriers. However, regulation of ABCB1 expression may differ significantly from tissue to tissue.…”