Member Biography

Eric Benson, M.D, Ph.D.

950 W. Walnut Street
R2 402
Indianapolis, IN 46202
Phone: (317) 274-7528

Research Program Membership

Associate member

Assistant Research Professor
Department of Medicine
Division of Clinical Pharmacology

Part-time Assistant Clinical Professor
Department of Medicine
Division of Clinical Pharmacology

Specific Aims: Exosomes have been reported as biomarkers of disease and drug response [1-7]. They are transport vesicles that are secreted from cells and deliver microRNAs, mRNA, and proteins to other cells; they can transport molecules to other local tissues, or to distant tissues through blood circulation. Both the exosomes and the target cells contain some surface molecules (e.g. lectin proteins) that appear to impact the rate (kinetics) and site of exosome uptake [8-10]. These delivery instructions are changed by the effects of disease or drug treatment and result in altered exosome uptake [1-7]. Thus, understanding these changes may elucidate new biomarkers that are associated with both diseases and drug responses. Collectively, these data indicate that critical unknowns are 1) what factors alter exosome kinetics and 2) how do those factors alter the delivery instructions. In this project, I will focus on understanding how alterations to the secreting cells alter the kinetics of the secreted exosomes. Due to the complexity of exosome transportation and the inherent difficulties of discerning the endogenous exosome transport system in humans, in vivo animal models have been used to directly study the transport paths of exosomes over time in blood. Exosome kinetics and transport, from here on, will be defined as the change in exosome concentration over time in animal blood. With the proper measurements of exosome concentration over time, all of the kinetic parameters including half-life, clearance, and volume of distribution can be determined using the same principles applied to the study of pharmacokinetics. The limitation of the published in vivo animal studies is that, in order to directly measure the exosomes, protein tags were inserted into the exosome membrane surface. It is uncertain how these fusion proteins in the exosome membrane may have directly altered the transport instructions. These insertions work well to develop exosomes for drug delivery, but do not work for the study of normal exosome biology and their use as biomarkers. To address this neglected aspect of exosome biology, I will study the kinetics of exosomes with unmodified-membrane surfaces by using exosomes with tagged cargo. My long-term goal is to improve the rational use of exosomal biomarkers to predict disease and treatment response. Understanding the exosome kinetics would help to optimize exosomal-biomarker validation study designs and may lead to studies that elucidate the mechanisms underlying biomarker associations. My broad objective for this proposal is to both detail cell type specific kinetics for secreted exosomes and detail the effects on the secreted exosome kinetics after drug treatments of cancer and normal cell types. My central hypothesis is that secreted exosomes from different cell types have different exosome kinetics and that the drug treatment of diseased and normal cells changes the kinetics of the secreted exosomes. To test this hypothesis I propose the following specific aims: Aim 1: To determine the in vivo exosome kinetics of exosomes secreted by different cell types. My working hypothesis is that exosomes originating from liver, kidney, and lung have different in vivo kinetic parameters (e.g. clearance, volume of distribution). To test this hypothesis, we will dose rats intravenously with exosomes isolated from cultured cells that have been loaded with tracer microRNAs (tagged cargo) and measure the disappearance of the tag’s concentration in the plasma over time. The exosome kinetic parameters will be calculated using the canonical methodology used to calculate the same parameters in pharmacokinetics. Aim 2: To determine the in vivo kinetic parameters of exosomes derived from drug treated cells. I have shown that circulating microRNAs change after carboplatin treatment in cancer patients and my preliminary data shows that exemestane induces changes in circulating microRNAs that may be in part due to changes in the circulating exosomes [11]. My working hypothesis is that estradiol and carboplatin induce changes in the in vivo kinetic parameters of exosomes. I will compare the in vivo kinetics of exosomes obtained from drug vs vehicle treated cells, using cell types relevant to drug efficacy and to toxicity for each drug. With the conclusion of these aims, I will have developed models that derive the kinetic parameters of exosomes in blood. By identifying conditions, such as cell type differences and drug treatments, that result in altered exosome kinetics, I will be able to pursue future R01 studies focused on the identification of the biochemical signals that regulate exosome transport and may be translated into clinically relevant biomarkers. In addition, these studies would also complement ongoing efforts by others both to use circulating miRNAs as biomarkers and to use exosomes for drug delivery. These aims will require training from my mentors and additional course work. I will fulfill my unmet educational needs in advanced bioinformatics and exosome-metrics with my co-mentors, Drs. Liu and Bies, and circulating microRNAs/exosome biology with my co-mentors, Drs. Nakshatri and Xu. New laboratory and analytic techniques will be developed in conjunction with my primary mentor, Dr. Skaar. From this K08 award, I expect to get the training, publications, data, and collaborations necessary to develop my academic career and obtain R01 funding.

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More Publications »

Fellowship - Indiana University School of Medicine, Indianapolis, IN 06/2014

Residency - Indiana University School of Medicine, Indianapolis, IN 06/2011

M.D. - Indiana University School of Medicine, Indianapolis, IN 05/2009

Ph.D. - Indiana University School of Medicine, Indianapolis, IN 05/2009