| Summary: | Alba Gomà,1,* Roser Mir,1–3,* Fina Martínez-Soler,1,4 Avelina Tortosa,4 August Vidal,5,6 Enric Condom,5,6 Ricardo Pérez–Tomás,6 Pepita Giménez-Bonafé1 1Departament de Ciències Fisiològiques II, Faculty of Medicine, Campus of Health Sciences of Bellvitge, Universitat de Barcelona, IDIBELL, Barcelona, Spain; 2División de Investigación Básica, Instituto Nacional de Cancerología, México DF, Mexico; 3Instituto de Física, Universidad Nacional Autónoma de México (UNAM), México DF, Mexico; 4Department of Basic Nursing, School of Nursing of the Health Campus of Bellvitge, Universitat de Barcelona, 5Department of Pathology, Hospital Universitari de Bellvitge, 6Department of Pathology and Experimental Therapeutics, Universitat de Barcelona, IDIBELL, Barcelona, Spain*These authors contributed equally to this work Background: One of the problems in prostate cancer (CaP) treatment is the appearance of the multidrug resistance phenotype, in which ATP-binding cassette transporters such as multidrug resistance protein 1 (MRP1) play a role. Different localizations of the transporter have been reported, some of them related to the chemoresistant phenotype.Aim: This study aimed to compare the localization of MRP1 in three prostate cell lines (normal, androgen-sensitive, and androgen-independent) in order to understand its possible role in CaP chemoresistance.Methods: MRP1 and caveolae protein markers were detected using confocal microscopy, performing colocalization techniques. Lipid raft isolation made it possible to detect these proteins by Western blot analysis. Caveolae and prostasomes were identified by electron microscopy.Results: We show that MRP1 is found in lipid raft fractions of tumor cells and that the number of caveolae increases with malignancy acquisition. MRP1 is found not only in the plasma membrane associated with lipid rafts but also in cytoplasmic accumulations colocalizing with the prostasome markers Caveolin-1 and CD59, suggesting that in CaP cells, MRP1 is localized in prostasomes.Conclusion: We hypothesize that the presence of MRP1 in prostasomes could serve as a reservoir of MRP1; thus, taking advantage of the release of their content, MRP1 could be translocated to the plasma membrane contributing to the chemoresistant phenotype. The presence of MRP1 in prostasomes could serve as a predictor of malignancy in CaP.Keywords: prostate cancer, MRP1, Caveolin-1, lipid rafts, caveolae, prostasomes
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