Cholelithiasis is a multifactorial process, and several mechanisms have been postulated. A decreased expression of the ileal apical sodium-dependent bile acid transporter (ASBT) and of the cytosolic ileal lipid binding protein (ILBP) was recently described in female non-obese patients. The role of the recently identified organic solute transporters a and b (OSTa, OSTb) in gallstone pathogenesis remains unclear. Therefore, we performed analysis of OSTa-OSTb in gallstone patients according to body weight. Ileal mucosal biopsies were collected during routine colonoscopy from female gallstone carriers (n 5 19) and controls (n 5 34). OSTa-OSTb mRNA expression was measured using the LightCycler sequence detection system; protein was analyzed by immunohistochemistry and Western blot. The mRNA expression of OSTa-OSTb was significantly reduced (OSTa: 3.3-fold, P 5 0.006; OSTb: 2.6-fold, P 5 0.03) in normal-weight but not overweight gallstone carriers compared with controls. OSTa-OSTb protein levels also showed a reduction by 40-67%. The expression of OSTaOSTb correlated positively with ASBT (r 5 0.65, 0.58, respectively), ILBP (r 5 0.77, 0.67), and the farnesoid X receptor (r 5 0.58, 0.50). Fibroblast growth factor-19 showed a 2.8-fold reduction (P 5 0.06), and liver receptor homolog-1 showed a 2-fold reduction (P 5 0.04) in nonobese patients. In conclusion, an impaired function of all three ileal bile acid transporters may lead to low ileal bile acid reabsorption and an altered bile acid pool composition and therefore may contribute to the formation of gallstones in non-obese patients. Bile acids are powerful detergents and play a critical role in multiple biological processes. They are synthesized in the liver, stored in the gallbladder, and released postprandially into the small intestine, where they are crucial for the absorption of lipophilic nutrients (1). The reuptake of bile acids from the terminal ileum is an important step in bile acid homeostasis and a major factor determining bile acid pool size (2). The major mechanism for ileal bile acid uptake is the active transport by the apical sodiumdependent bile acid transporter (ASBT), located in the brush border (3, 4). The subsequent intracellular transport of bile acids is mediated by the cytosolic ileal lipid binding protein (ILBP), which shuttles bile acids to the basolateral membrane (5, 6). Responsible for secretion of bile acids into the portal circulation are the basolateral organic solute transporters a and b (OSTa, OSTb) (7).In a recent study, we showed that female gallstone carriers exhibit a decreased ileal expression of ASBT and ILBP and their most relevant transcription factors, farnesoid X receptor (FXR) and hepatic nuclear factor 1 a (HNF1a) (8). This decrease was observed on both the mRNA and protein levels and may explain bile lithogenicity by an intestinal bile acid loss. However, compatible with differences in cholesterol handling in lean and obese subjects (9), this effect was weight specific and observed only in normal-weight subjects...

The efflux transporter breast cancer resistance protein BCRP/ABCG2 is well-known for its contribution to multi-drug resistance in cancer. Its relevance in cancer biology independent from drug efflux remains largely elusive. Our study aimed at elucidating the biological relevance and regulatory mechanisms of BCRP/ABCG2 in clear cell renal cell carcinoma (ccRCC) and disease progression. Two independent ccRCC-cohorts [Cohort 1 (KIRC/TCGA): n = 453, Cohort 2: n = 64] were investigated to elucidate BCRP/ABCG2 mRNA and protein expression and their association with survival. The impact of BCRP/ABCG2 on response to sunitinib treatment was investigated in two independent sunitinib-treated ccRCC-cohorts based on mRNA levels. Moreover, underlying regulatory mechanisms for interindividual variability of BCRP/ABCG2 expression were systematically assessed. Owing to redundant functional properties, mRNA and protein expression of the multidrug resistance protein MDR1/ABCB1 were additionally evaluated in these cohorts. In independent ccRCC-cohorts, low BCRP/ABCG2 and MDR1/ABCB1 mRNA and protein expression were associated with severity (e.g., tumor stage) of ccRCC and poor cancer-specific survival. BCRP/ABCG2 and MDR1/ABCB1 mRNA expression were linked to decreased progression-free survival after sunitinib treatment. Germline and somatic variants influenced interindividual variability of BCRP/ABCG2 expression only moderately. miR-212-3p and miR-132-3p were identified to regulate BCRP/ABCG2 posttranscriptionally by interaction with the ABCG2 3'UTR as confirmed through reporter gene assays in RCC cell lines. In summary, BCRP/ABCG2 expression in ccRCC underlies considerable interindividual variability with impact on patient survival and response to sunitinib treatment. While germline or somatic genetic variants and DNA methylation cannot explain aberrant BCRP/ABCG2 expression, miR-212-3p and miR-132-3p were identified to contribute to posttranscriptional regulation of BCRP/ABCG2.

BackgroundCholelithiasis is a multifactorial process and several mechanisms of gallstone formation have been postulated. As one of these mechanisms, a decreased expression of the ileal apical sodium-dependent bile acid transporter gene SLC10A2 in gallstone carriers was described previously. In this study the SLC10A2 gene was investigated to identify novel genetic variants and their association with gallstone formation.Methodology/Principal FindingsStudy subjects were selected with the presence or absence of gallstones confirmed by ultrasound and medical history. Genomic DNA was obtained from blood leukocytes. Sequence analysis was performed of all six exonic and flanking regions as well as of 2,400 base pairs of the SLC10A2 promoter in a cohort of gallstone carriers and control subjects from Stuttgart, Germany. Genotype frequencies of newly identified genetic variants (n = 6) and known single nucleotide polymorphisms (n = 24) were established using MALDI-TOF mass spectrometry. Six new genetic variants were found within the SLC10A2 gene. Although none of the variants was linked to gallstone disease in the Stuttgart cohort overall, the minor allele of SNP rs9514089 was more prevalent in male non-obese gallstone carriers (p = 0.06680, OR = 11.00). In a separate population from Aachen, Germany, the occurrence of rs9514089 was two-fold higher in gallstone patients (22%) than in corresponding controls (11%) (p = 0.00995, OR = 2.19). In the pooled Aachen/Stuttgart cohort rs9514089 was highly significantly linked to cholelithiasis (p = 0.00767, OR = 2.04). A more frequent occurrence was observed for male gallstone carriers (22%) compared to controls (9%) (p = 0.01017, OR = 2.99), for the total normal weight group (p = 0.00754, OR = 2.90), and for male non-obese gallstone patients (p = 0.01410, OR = 6.85). Moreover, for the minor allele of rs9514089 an association with low plasma cholesterol levels was found especially in gallstone carriers (p = 0.05).Conclusions/SignificanceWe have identified SLC10A2 as a novel susceptibility gene for cholelithiasis in humans. Comprehensive statistical analysis provides strong evidence that rs9514089 is a genetic determinant especially in male non-obese gallstone carriers. The minor allele of rs9514089 is related to differences in plasma cholesterol levels among the subjects.