Exosomes Secreted by Macrophages Facilitate Gemcitabine Resistance in Pancreatic Ductal Adenocarcinoma

Yoav Binenbaum 1 Jacob T. Cohen 1 Eran Fridman 1 Tomer Shlomi 2 Gil Ben-David 1 Ziv Gil 1,3
1Clinical Research Institute at Rambam Health Campus, Laboratory of Applied Cancer Science
2Department of Computer Science, Lokey Center for Life Science and Engineering, Technion-Israel Institute of Technology
3Research in the Medical Sciences, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology

Gemcitabine is the drug of choice for Pancreatic Ductal Adenocarcinoma(PDAC), albeit resistance to the drug is almost uniform. We recently demonstrated that tumor-associated macrophages(TAMs) cause Gemcitabine resistance by inducing Cytidine-deaminase(CDA) in the PDAC cell, an enzyme that metabolizes Gemcitabine to its inactive form, dFdUridine1. The goal of the present work was to elucidate the mechanism by which TAMs communicate with PDAC cells, inducing CDA expression.

Electron microscopy of TAM condition medium showed that its abundant with micro-vesicles expressing molecular markers of exosomes. Application of purified macrophage-derived-exosomes(MDEs) on PDAC cells doubled Gemcitabine`s LD50% from 4.7-2µM to 8.62µM. TAM MDEs were enriched with miR-365 as compared with exosomes from M1 macrophages. Transfection of TAMs co-cultured with PDAC cells with 365-antagomiR led to reversal of resistance, in contrast to Rab 27a-/-b-/- TAMs lacking exosome secretion2. Treatment of PDAC cells with miR-365 mimic or with MDEs, caused elevation in CDA expression followed by elevation in dFdUridine.

In an in-vivo adoptive immune-transfer experiment, mice were treated with Gemcitabine and either Rab 27a-/-b-/- macrophages; WT macrophages transfected with mock miR; or WT macrophages transfected with 365-antagomiR. By 63 days all mice in the WT transfer group died, but only half in the 365-antagomiR transfer group(P=0.03). Survival in the Rab 27a-/-b-/- control was similar to 365-antagomiR group. Tumors exhibited minimal CDA expression in the Rab 27a-/-b-/- group, moderate expression in the 365-antagomiR group, and high expression in the WT transfer group.

Our results demonstrate that Gemcitabine resistance is mediated by MDEs, shuttling miRNAs between TAMs and tumor cells. 365-antagomiR augments Gemcitabine efficacy in vitro and in vivo by mitigating CDA expression in the cancer cell, thus preventing inactivation of the drug.

1. Weizman etal. Oncogene (2013). doi:10.1038/onc.2013.357

2. Ostrowski etal. NatCellBiol. (2009). doi:10.1038/ncb2000









Powered by Eventact EMS