We determined whether in vivo transporter-mediated hepatobiliary clearance (CL) and hepatic concentrations of rosuvastatin (RSV) in the rat could be predicted by transport activity in sandwich-cultured rat hepatocytes (SCRHs) and/or transporter-expressing cell lines scaled by differences in transporter protein expression between SCRHs, cell lines, and rat liver. The predicted hepatobiliary CLs and hepatic concentrations of RSV were compared with our previously published positron emission tomography imaging data. Sinusoidal uptake CL ([Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] [Formula: see text] for Oatp protein expression. This is the first demonstration of the successful prediction of in vivo hepatobiliary CLs and hepatic concentrations of RSV using transporter-expressing cells and SCRHs.

Quantitative proteomics, using LC-MS/MS, is increasingly used to quantify drug transporters present in tissues and cells. Most of these investigations quantify total transporter expression in the cells by utilizing a total membrane fraction, not only the plasma membrane. Here, we report development and optimization of a biotinylation method to quantify protein expression of transporters in the plasma membrane of cells. The Pierce cell surface isolation protocol was optimized for plasma membrane isolation. Incubation of OATP1B1-expressing CHO cells with 0.78 mg/mL of membrane impermeable biotinylation reagent (sulfo-NHS-SS-biotin) at 37°C for 1 h resulted in optimum isolation of the plasma membrane. Subsequently, the expression of transporters in the plasma membrane as a percent of the total was determined by quantitative proteomics using LC-MS/MS. Mean (±SD) plasma membrane expression of OATP1B1 in plated OATP1B1-expressing CHO, MDCKII, and HEK293 cells was found to be 79.7% (±4.7%), 67.7% (±12.2%), and 65.3% (±6.8%) of total cell OATP1B1 expression. Mean (±SD) plasma membrane expression of OATP1B3 in plated OATP1B3-expressing HEK293 cells, OATP2B1 in plated OATP2B1-expressing MDCKII cells, and sodium/taurocholate co-transporting polypeptide (NTCP) in plated NTCP-expressing CHO cells was 63.2% (±1.6%), 37.1% (±15.7%), and 71.7% (±1.2%), respectively. This method of quantifying transporter protein expression in the plasma membrane will be useful in the future to predict transporter-mediated drug disposition.

For successful in vitro-to-in vivo extrapolation of hepatic drug uptake and drug-drug interactions (DDI), it is important to characterize the kinetic properties of the individual transporters involved, their fraction (ft) contribution to hepatic uptake, and their selective inhibitors. Here, we characterized the in vitro transport kinetics of two model drugs, rosuvastatin (RSV) and olmesartan acid (OLM), by rat hepatic organic anion transporting polypeptides (Oatp1a1, 1a4, and 1b2) and identified selective inhibitors of these transporters. [H]-RSV was transported by Oatp1a1, 1a4, and 1b2, and their Michaelis-Menten constant () values were estimated to be 9.61, 67.2, and 28.1 M, respectively. In contrast, [H]-OLM was transported by only Oatp1b2 (: 72.8 M). Digoxin (IC: 0.107 M) and rifamycin SV (IC: 0.140 and 0.088 M for RSV and OLM, respectively) were potent and selective inhibitors of Oatp1a4 and 1b2, respectively, and glyburide (100M) completely inhibited all three rat hepatic Oatps. These inhibitors can therefore be used alone and in combination to determine the contribution of each Oatp to hepatic influx. In addition, the magnitude of in vivo inhibition of sinusoidal uptake clearance of RSV by rifampin was well predicted using rifampin IC profiles for each Oatps and RSV ft by each Oatp. This is the first report to 1) detail the transport kinetics of RSV and OLM by rat hepatic Oatps, 2) identify selective inhibitor concentrations of rat Oatps, and 3) demonstrate successful prediction of the magnitude of transporter-mediated in vivo DDI from IC profiles of an inhibitor and ft of a drug by each transporter.

There is increasing evidence that thrombocytosis is associated with tumor invasion and metastasis formation. It was shown in several solid tumor types that thrombocytosis prognosticates cancer progression. The aim of this study was to evaluate preoperative thrombocytosis as a potential prognostic biomarker in isolated metastases, in patients with liver metastasis of colorectal cancer (mCRC). Clinicopathological data of 166 patients with mCRC who had surgical resection between 2001 and 2011 were collected retrospectively. All primary tumors have been already resected. The platelet count was evaluated based on the standard preoperative blood profile. The patients were followed-up on average for 28 months. Overall survival (OS) of patients with thrombocytosis was significantly worse both in univariate (HR = 3.00, p = 0.03) and in multivariate analysis (HR = 4.68, p = 0.056) when adjusted for gender, age, tumor size and surgical margin. Thrombocytosis was also a good prognosticator of disease-free survival (DFS) with HR = 2.7, p = 0.018 and nearly significant in multivariate setting (HR = 2.26, p = 0.073). The platelet count is a valuable prognostic marker for the survival in patients with mCRC.

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The use and significance of baicalin, the main bioactive component found in Radix Scutellaria, have been on the rise due to its interesting pharmacological properties. Baicalin, a low passive permeability compound, is directly absorbed from the upper intestine and its hepatic elimination is dominant. However, interaction but no transport studies have implicated organic anion‐transporting polypeptides in its cellular uptake. By using mammalian cells stably expressing the uptake transporters of interest, we are showing that baicalin is a potent substrate of Organic anion‐transporting polypeptide 2B1 (OATP2B1) and less potent substrate of OATP1B3. OATP2B1 and OATP1B3 transport baicalin and may play a role in the hepatic uptake of baicalin formed in the intestine.

The concentrative nucleoside transporters (CNT; solute carrier family 28 (SLC28)) and the equilibrative nucleoside transporters (ENT; solute carrier family 29 (SLC29)) are important therapeutic targets but may also mediate toxicity or adverse events. To explore the relative role of the base and the monosaccharide moiety in inhibitor selectivity we selected compounds that either harbor an arabinose moiety or a cytosine moiety, as these groups had several commercially available drug members. The screening data showed that more compounds harboring a cytosine moiety displayed potent interactions with the CNTs than compounds harboring the arabinose moiety. In contrast, ENTs showed a preference for compounds with an arabinose moiety. The correlation between CNT1 and CNT3 was good as five of six compounds displayed IC values within the threefold threshold and one displayed a borderline 4-fold difference. For CNT1 and CNT2 as well as for CNT2 and CNT3 only two of six IC values correlated and one displayed a borderline 4-fold difference. Interestingly, of the six compounds that potently interacted with both ENT1 and ENT2 only nelarabine displayed selectivity. Our data show differences between inhibitor selectivities of CNTs and ENTs as well as differences within the CNT family members.