Human organic anion transporting polypeptide 1B3 (OATP1B3) is a hepatocyte drug transporter that facilitates
uptake of various therapeutic drugs from the circulatory system. Shortly after its initial identification in the
liver, OATP1B3 expression was also reported in various solid cancer tissues. In the years since that time, it has
been presumed that the OATP1B3 expressed in cancer tissues is identical to that expressed in the liver. However,
we have recently identified a new OATP1B3 mRNA variant in cancer tissues, which we have named cancer-type
OATP1B3 (Ct-OATP1B3). Given that the identification of Ct-OAT1B3 as a bona fide cancer-associated isoform
revises a longstanding study premise, it is essential to fully elucidate the molecular function of Ct-OATP1B3 in
cancer cells. Based on the predicted Ct-OATP1B3 protein structure, it is reasonable to assume that it functions as a transporter, but there
are a number of ongoing arguments regarding Ct-OATP1B3 protein expression and its functions. With the above points in mind, this review
will summarize current knowledge of Ct-OATP1B3 mRNA expression features in cancer tissues and its proposed, yet currently
controversial, functions. Based on that background, our future perspectives related to Ct-OATP1B3 studies will also be presented.
Keywords: Cancer, cancer biomarker, cancer-specific molecule, OATP1B3, SLCO1B3, splice variant, transporter.
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