Extracellular vesicles as dynamic surrogates for drug transporter expression. A new tool to personalize pharmacotherapy?

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The P-glycoprotein (P-gp/ABCB1), the multidrug resistance-associated protein 2 (MRP2/ABCC2) and the breast cancer resistance protein (BCRP/ABCG2) belong to the superfamily of ABC transporters (ATP binding cassette) and play a major role in drug pharmacokinetics. They are expressed in organs and tissues of high pharmacological relevance such as the liver, the kidneys, the intestine and the blood-brain barrier. In addition, they account for the resistance towards chemotherapeutic agents in cancer cells. The expression of ABC transporters is highly variable within the population and can be regulated by coadministered drugs, the diet and hormones, among other factors. This way, significant differences in the drug clearance between individuals as well as during the lifespan of an individual can be expected. In general, higher transporter expression leads to higher drug clearance and therapy failure. Lower transporter expression leads to lower drug clearance and toxicity. Thus, the individualized estimation of the expression of ABC transporters could aid to adjust the therapy to avoid cases of over- and under-exposure. So far, repeated extraction of biopsies would be the only option to measure ABC transporter expression in relevant tissues. However, due to its intrinsic invasive character, this cannot be performed routinely.Extracellular vesicles (EVs) are nanoparticles released by all cell types of the organism. The EV cargo consists of cellular proteins, RNA, and lipids, the array of these components representing a fingerprint of the cell of origin. The presence of EVs from a wide range of tissues in the blood, plus the presence of kidney EVs in the urine, would allow for an easy access to these nanoparticles in the clinical practice. The general aim of this project is to investigate the potential of the ABC transporter-cargo in EVs as a dynamic surrogate for the transporter expression in normal and tumoral cells and thus, for their drug excretion capacity. We will develop, optimize and validate an ultrasensitive UPLC-MS/MS assay for the absolute and simultaneous quantification of P-gp, MRP2 and BCRP in EVs and the cells of origin. This assay will be applied to analyze the correlation between the transporter expression in EVs and the expression and activity in the cells both under basal and inducing conditions. In tumor cells, the correlation between the transporter expression in EVs and the resistance to chemotherapeutic agents will also be investigated. Finally, a method to isolate cell-specific EVs from a multicellular model (blood-brain-barrier organoids) will be developed in order to elucidate the potential of EVs to estimate the cell-specific transporter expression in a more complex system. Altogether, the use of EVs to estimate the transporter expression could allow to stratify the patients based on their drug clearance capacity and, thus, adjust pharmacotherapy and, ultimately, prevent situations of toxicity or therapy failure.