Abstract 172: Adipocytes decrease daunorubicin concentration in acute lymphoblastic leukemia cells

Abstract

Abstract Obesity is associated with increased cancer incidence and mortality. Adipose tissue has been shown to play a role in several types of cancer, including acute lymphoblastic leukemia (ALL). We have demonstrated that murine ALL cells actively migrate into adipose tissue in mice, and that adipocytes protect ALL cells from daunorubicin (DNR) in vitro. We have further shown that media cultured by both adipocytes and ALL cells together (ALCM) can protect ALL cells from DNR. We hypothesize that adipocytes protect ALL cells from DNR by decreasing ALL cell intracellular drug accumulation. Human pre B ALL cells (BV173) were co-cultured with 3T3-L1 adipocytes using a transwell system. Intracellular DNR was visualized using con-focal fluorescence microscopy at various time points in leukemia cells during DNR treatment. Drug uptake in leukemia cells treated with DNR and co-cultured with adipocytes was measured by flow cytometry. By preloading cells with DNR, drug efflux assays were also performed with ALL cells. Gene expression of ABCB1a and cell surface expression of MDR1 were quantified using qPCR and flow cytometry, respectively, in ALL cells co-cultured with adipocytes. After 72 hours of DNR treatment, there were significantly more viable BV173 cells in the transwells placed over adipocytes than those over fibroblasts (290,000± 60,500 vs. 108,000± 13,000, p=0.008, n=4). Co-culture with adipocytes was associated with a lower intracellular DNR in BV173 cells. After 4 hours, DNR was 30% lower, and by 24 hours intracellular DNR was 80% less (n=1). However, co-culturing ALL cells with adipocytes was not associated with a significant increase in efflux rate of DNR from preloaded BV173 (half-life = 36±13 vs. 31±9 min., p=0.23, n=3). The mRNA expression of ABCB1a, the gene encoding MDR1, was increased in BV173 cells (130% increase, n=1) co-cultured with adipocytes for 24 hours. However, we did not detect an increase in surface MDR1 expression in BV713 co-cultured with adipocytes. We then tested whether adipocyte-secreted factors would cause efflux of DNR from ALL cells. There was a tendency for DNR efflux rate to be higher in BV173 cells cultured in ALCM (half-life = 36±13 vs. 27±10 min., p=0.08, n=3). Further investigation is needed to confirm this effect. These findings demonstrate that adipocytes may protect ALL cells from daunorubicin treatment in part by decreasing intracellular drug accumulation. However, it is not clear whether this effect is due to altered uptake, efflux, or intracellular drug action. Citation Format: Xia Sheng, Jonathan Tucci, James Behan, Steven D. Mittelman. Adipocytes decrease daunorubicin concentration in acute lymphoblastic leukemia cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 172. doi:10.1158/1538-7445.AM2014-172