In vivo disposition of doxorubicin is affected by mouse Oatp1a/1b and human OATP1A/1B transporters

Abstract

Organic anion-transporting polypeptides (OATPs) are important drug uptake transporters, mediating distribution of substrates to several pharmacokinetically relevant organs. Doxorubicin is a widely used anti-cancer drug extensively studied for its interactions with various drug transporters, but not OATPs. Here, we investigated the role of OATP1A/1B proteins in the distribution of doxorubicin. In vitro, we observed ∼ 2-fold increased doxorubicin uptake in HEK293 cells overexpressing human OATP1A2, but not OATP1B1 or OATP1B3. In mice, absence of Oatp1a/1b transporters led to up to 2-fold higher doxorubicin plasma concentrations and 1.3-fold higher plasma AUC. Conversely, liver AUC and liver-to-plasma ratios of Oatp1a/1b(-/-) mice were 1.4-fold and up to 4.1-fold lower than in wild-type mice, respectively. Decreased doxorubicin levels in the small intestinal content reflected those in the liver, indicating a reduced biliary excretion of doxorubicin in Oatp1a/1b(-/-) mice. These results demonstrate important control of doxorubicin plasma clearance and hepatic uptake by mouse Oatp1a/1b transporters. This is unexpected, as the fairly hydrophobic weak base doxorubicin is an atypical OATP1A/1B substrate. Interestingly, transgenic liver-specific expression of human OATP1A2, OATP1B1 or OATP1B3 could partially rescue the increased doxorubicin plasma levels of Oatp1a/1b(-/-) mice. Hepatic uptake and bile-derived intestinal excretion of doxorubicin were completely reverted to wild-type levels by OATP1A2, and partially by OATP1B1 and OATP1B3. Thus, doxorubicin is transported by hepatocyte-expressed OATP1A2, -1B1 and -1B3 in vivo, illustrating an unexpectedly wide substrate specificity. These findings have possible implications for the uptake, disposition, therapy response and toxicity of doxorubicin, also in human tumors and tissues expressing these transporters.

Contribution of Organic Anion-Transporting Polypeptides 1A/1B to Doxorubicin Uptake and Clearance

“…To the best of our knowledge, this is the first report using polarized MDCKII cells transfected stably by OATP1A2 and MDR1 cDNA constructs for drug transport. Collectively, our data indicate doxorubicin is a good substrate for OATP1A2, which is in agreement with a previous report demonstrating OATP1A2-mediated doxorubicin transport in HEK293 cells (Durmus et al, 2014).…”

“…Our initial studies revealed doxorubicin to be an efficient substrate for human OATP1A2, but not OATP1B1 and OATP1B3, when assessed in detail using a recombinant vaccinia-based method in a HeLa cell system. However, for reasons that are not well-defined, OATP-mediated uptake of certain substrates, including drugs such as doxorubicin and docetaxel, has been noted by other groups to be variably discrepant in results among in vitro systems or when comparing in vitro to in vivo transport (Smith et al, 2005;de Graan et al, 2012;Durmus et al, 2014;Lee et al, 2015). Hence, absence of doxorubicin transport in HeLa cells does not preclude it to be transported in vitro by OATP1B transporters in another system.…”

“…Mice deficient in Oatp1a/1b transporters have been generated and functionally characterized for in vivo transport of endogenous or xenobiotic OATP substrates (van de Steeg et al, 2010;Zaher et al, 2008). Durmus et al (2014) demonstrated that doxorubicin disposition was affected by mouse and human OATP1A/1B transporters using Slco1a/1b2 2/2 mice and humanized transgenic mice. Slco1a/1b2 2/2 mice demonstrated significantly higher plasma concentrations and AUC than wildtype mice.…”

“…Because doxorubicin is a hydrophobic weak base and cation at physiologic pH, it had not been considered a potential substrate for OATP transporters. Recently, however, Durmus et al (2014) demonstrated that OATP1A/1B transporters play a substantial role in the in vivo disposition of doxorubicin. However, although doxorubicin is widely known to be a substrate for ABC-family drug efflux transporters such as P-glycoprotein (P-gp; MDR1), MRP2, and BCRP (Allen et al, 1999;van Asperen et al, 2000;Vlaming et al, 2006), significantly less is known regarding its interactions with drug uptake transporters that could mediate its cellular uptake and clearance.…”

Role of Organic Anion-Transporting Polypeptides (OATPs) in Cancer Therapy

“…Similarly, transgenic humanized OATP1A/1B mouse models were generated with liverspecific expression of OATP1B1, OATP1B3, and OATP1A2 in an Oatp1a/1b knockout background. This model was utilized to show that paclitaxel, methotrexate, SN-38, docetaxel, and doxorubicin are transported by OATP1A/1B in vivo (19,20,57,58).…”