Abstract 424: Depletion of serum levels of miRNA-150 indicates bone marrow damage following total body irradiation.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Total body irradiation (TBI) is part of the preparative regimen for bone marrow transplantation in lymphoma and leukemia patients. Depending on the aggressiveness of the disease, patients receive a dose between 2 -12 Gray, in 2 Gray fractions over three days. Fast and accurate estimation of the absorbed dose is critical for evaluation of the depletion of cancer cells prior to transplantation. Physical dosimeters and the available biologics have limitations to accurately evaluate the effect of radiation because the normal tissue toxicity as well as the radiation response in cancer cells varies depending on individual's genetics, immune status and other confounding factors. We sought to identify and validate robust and fast responding biomarkers of radiation response, which are repeatedly assayable from body fluids. We have utilized an amplification-free, hybridization based quantitative assay utilizing the nCounter multiplex platform developed by nanoString Technologies to compare the relative abundance of over 600 miRNAs in body fluids. Our studies have identified several evolutionarily and functionally conserved miRNAs in serum and urine collected from two different strains of mice. Development of a novel normalization strategy using multiple spike-in oligonucleotides allowed the accurate measurement of changes in serum and urine miRNAs after TBI. miRNAs with good dose response were further investigated for their potential for development as radiation biodosimeters. Hierarchical clustering followed by comparison of changes in individual miRNAs with varying dose (1 - 12 Gray) and time points (1 - 7 days) has identified miRNA-150 as a very promising biomarker for radiation biodosimetry. miRNA-150 is expressed at high level in mature lymphocytes and the abundance of circulating miRNA-150 seems correlating with that of lymphocyte counts. With acute single doses of 1, 2, 4, 6 and 8 Gray, a 30%, 38%, 48% 70% and 72% statistically significant reduction in serum miRNA-150 was observed at 24 hrs, which was further reduced at later time points. Consistent with this data, a time and dose dependent reduction of miRNA-150 was observed after fractionation, with a near complete depletion by 24 hrs after completion of 12 Gray. The kinetics of depletion of serum miRNA-150 following radiation indicate its potential as an alternative to complete blood count (CBC) to evaluate lymphocyte depletion, and hence evaluating damage to the hematopoietic system. The effect of relevant acute single doses and fractionated radiation treatment at various time points will be presented. The utilization of these readouts for understanding the effects and mechanism of action of radioprotectors will also be discussed. Citation Format: Naduparambil K. Jacob, James V. Cooley, Arnab Chakravarti. Depletion of serum levels of miRNA-150 indicates bone marrow damage following total body irradiation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 424. doi:10.1158/1538-7445.AM2013-424