Expression of organic anion-transporting polypeptides 1B3, 1B1, and 1A2 in human pancreatic cancer reveals a new class of potential therapeutic targets
Valentinos Kounnis1, Elli Ioachim2, Martin Svoboda3, Andreas Tzakos4, Ioannis Sainis1, Theresia Thalhammer3, Georg Steiner5, Evangelos Briasoulis1
1Cancer Biobank Center of the University of Ioannina, Greece; 2Pathology Department of Hatzikosta General Hospital, Ioannina Greece; 3Department of Pathophysiology and Allergy Research, Medical University of Vienna, Austria; 4Department of Chemistry, University of Ioannina, Greece; 5TissueGnostics GmbH, Vienna, Austria
Background: Organic anion-transporting polypeptides (OATPs) are influx transporters that mediate intracellular uptake of selective endogenous and xenobiotic compounds. Identification of new molecular targets and discovery of novel targeted therapies is top priority for pancreatic cancer, which lacks any effective therapy.
Materials and methods: We studied expression of OATP 1A2, 1B1, and 1B3 in pancreatic cancer tissue and in cell lines. Formalin-fixed paraffin-embedded biopsy material of 12 human pancreatic cancers was immunohistochemically assessed for protein expression of the three studied influx transporters. Immunohistochemistry was evaluated by experienced pathologists and quantified by use of an automated image analysis system. BxPC-3 and MIA PaCa-2 pancreatic cancer cell lines were used to quantify transcripts of OATP 1B1 and 1B3.
Results: OATP 1A2, 1B1, and 1B3 proteins were found ubiquitously expressed in all studied cases. Quantification performed by HistoQuest system revealed that mean intensity was 53 for 1A2, 45 for 1B1, and 167 for OATP 1B1/1B3 on a range scale 0–250 units. At mRNA level, 1B1 and 1B3 were overexpressed in both studied cancer cell lines but not in normal pancreatic tissue.
Conclusion: OATPs 1A2, 1B1, and 1B3 are highly expressed in pancreatic adenocarcinoma. We suggest that expression of these transporters in pancreatic cancer justify research efforts towards discovery of novel therapeutics targeting OATPs.
Keywords: organic anion-transporting polypeptides, targeted therapy, transporter
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