ABCG2 polymorphism is associated with the low-density lipoprotein cholesterol response to rosuvastatin

In vitro and in vivo evidence for the importance of breast cancer resistance protein transporters (BCRP/MXR/ABCP/ABCG2)

The breast cancer resistance protein (BCRP/ABCG2) is a member of the G-subfamiliy of the ATP-binding cassette (ABC)-transporter superfamily. This half-transporter is assumed to function as an important mechanism limiting cellular accumulation of various compounds. In context of its tissue distribution with localization in the sinusoidal membrane of hepatocytes, and in the apical membrane of enterocytes ABCG2 is assumed to function as an important mechanism facilitating hepatobiliary excretion and limiting oral bioavailability, respectively. Indeed functional assessment performing mouse studies with genetic deletion or chemical inhibition of the transporter, or performing pharmacogenetic studies in humans support this assumption. Furthermore the efflux function of ABCG2 has been linked to sanctuary blood tissue barriers as described for placenta and the central nervous system. However, in lactating mammary glands ABCG2 increases the transfer of substrates into milk thereby increasing the exposure to potential noxes of a breastfed newborn. With regard to its broad substrate spectrum including various anticancer drugs and environmental carcinogens the function of ABCG2 has been associated with multidrug resistance and tumor development/progression. In terms of cancer biology current research is focusing on the expression and function of ABCG2 in immature stem cells. Recent findings support the notion that the physiological function of ABCG2 is involved in the elimination of uric acid resulting in higher risk for developing gout in male patients harboring genetic variants. Taken together ABCG2 is implicated in various pathophysiological and pharmacological processes.

Effect of central obesity, low high-density lipoprotein cholesterol and C-reactive protein polymorphisms on C-reactive protein levels during treatment with Rosuvastatin (10 mg Daily)

Plasma levels of high-sensitivity C-reactive protein (hsCRP) are an important predictor of cardiovascular disease, and achievement of lower targets of hsCRP with rosuvastatin treatment was associated with improved cardiovascular outcomes. The aim of this study was to examine whether hsCRP levels were related to genetic variants and traditional cardiovascular risk factors in Chinese patients treated with rosuvastatin 10 mg/day. The relations were analyzed between on-treatment plasma hsCRP concentrations and cardiovascular risk factors and 14 single-nucleotide polymorphisms in CRP and other candidate genes. In 281 patients with a median plasma hsCRP level of 0.81 mg/L (interquartile range 0.46 to 1.86), higher hsCRP levels were significantly associated with female gender, greater waist circumference (WC), having diabetes, higher triglycerides, and lower high-density lipoprotein (HDL) cholesterol. Three single-nucleotide polymorphisms (rs1205, 3872G>A and rs2808630, 5237A>G in CRP and rs1169288, I27L in HNF1A) were independently associated with hsCRP levels before and after adjustment for other variables. WC and the CRP rs1205 polymorphism showed the strongest relations with hsCRP, and in multiple regression analysis, gender, WC, diabetes, triglycerides, HDL cholesterol, and the 3 genetic variants explained 35.5% of the variance in hsCRP levels. The 2 CRP polymorphisms, female gender, higher WC, and lower HDL cholesterol were associated with risk for having CRP concentrations ≥ 1 mg/L. In conclusion, central obesity, low HDL cholesterol, and CRP polymorphisms are major determinants of higher hsCRP levels in Chinese patients receiving treatment with rosuvastatin.

The ABCG2 transporter and its relations with the pharmacokinetics, drug interaction and lipid-lowering effects of statins

IMPORTANCE OF THE FIELD

The ABCG2 efflux transporter is expressed in multiple tissues and plays an important role in the disposition of many statins. The functional 421C>A polymorphism in ABCG2 that reduces transporter activity has been found to be associated with increased systemic exposures to certain statins.

AREAS COVERED IN THIS REVIEW

We review and evaluate the associations of the ABCG2 polymorphism on the pharmacokinetics and clinical efficacy of statins.

WHAT THE READER WILL GAIN

This article gives a detailed overview of the ABCG2 transporter and extensively reviews its relations with the pharmacokinetics and lipid-lowering effects of statins. This review also discusses the potential role of the ABCG2 polymorphism in the clinical outcomes in statin-treated patients and statin-drug interactions.

TAKE HOME MESSAGE

The impact of the ABCG2 421C>A polymorphism on the disposition of the statins varies between different drugs and the effect on systemic exposure was greater in the case of rosuvastatin than other statins. This genetic variant was associated with greater low-density lipoprotein cholesterol response to rosuvastatin in Chinese and caucasian patients. The effect of the ABCG2 421C>A polymorphism on the lipid response to other substrate statins and clinical outcomes need to be evaluated in future studies.

Drug transport by breast cancer resistance protein

IMPORTANCE OF THE FIELD

The ATP-binding cassette transporter ABCG2 is a well-known major mediator of multi-drug resistance in cancers. Beyond multi-drug resistance, experimental and recent clinical studies demonstrate a role for ABCG2 as a determinant of drug pharmacokinetic, safety and efficacy profiles.

AREAS COVERED IN THIS REVIEW

The clinical evidence of the role of ABCG2 in pharmacokinetics and pharmacodynamics is reviewed. Key questions that arise from the perspective of preclinical drug evaluation are addressed, including the structure of ABCG2 and mechanisms of drug-transporter interactions, mechanisms responsible for the polyspecificity of ABCG2, methods suitable for studying drug-ABCG2 interactions in vitro and in silico prediction of ABCG2 substrates and inhibitors.

WHAT THE READER WILL GAIN

An update on current knowledge of the importance of ABCG2 in drug disposition with special emphasis on drug development.

TAKE HOME MESSAGE

The field of drug-ABCG2 interaction is rapidly advancing and beginning to expand into clinical practice. However, the structural understanding of drug binding and transport by ABCG2 is still incomplete. Incorporation of novel concepts of drug-transporter interactions such as electrostatic funneling might help explain the multispecificity of ABCG2 and enable in silico predictions.