Poster Presentation Australasia Extracellular Vesicles Conference 2017

Role of exosomes in chemotherapy resistance during ovarian cancer progression (#40)

Mona Alharbi 1 , Richard Kline 2 , Katrina Wade 2 , Carlos Palma 1 , Jacob Estes 1 , Gregory Rice 1 2 , John Hopper 3 , Carlos Salomon 1 2
  1. Exosome Biology Laboratory, The University of Queensland, Bris, QLD, Australia
  2. Department of Obstetrics and Gynecology, Ochsner Baptist Hospital, New Orleans, Louisiana, USA
  3. Mater Research Institute, University of Queensland, Translational Research Institute, Woolloongabba, QLD, Australia

Introduction: Hypoxia is a key regulatory factor of cancer progression via multiple processes, including enhanced resistance to chemotherapy drugs. Interestingly, the release of exosomes is higher under hypoxic conditions; however, the potential role of exosomes in chemotherapy resistance in ovarian cancer has yet to be established. We hypothesize that exosomes can induce chemotherapy resistance to neighboring cells.

Methods: CaOV-3 cells were used as models of ovarian cancer. Cells were cultured under 8% O2 (normoxia) and 1% O2 (hypoxia) for 48 hours. Exosomes were isolated from cell-conditioned media by differential and buoyant density centrifugation. Exosomes were characterized by nanoparticle tracking analysis, electron microscopy, and western blot (CD63 and TSG101). Cell migration was assessed by scratch assays using a 96-well plate Wound MakerTM in the presence of 8% or 1% O2 exosomes. For the chemo drug resistance, cells were incubated in the absence or in the presence of exosomes and with Paclitaxel (0.01-100 μM) or carboplatin (0.01-100 μM) for 48 hours. The effect of chemotherapy drugs on cell apoptosis were determined by quantifying Caspase3/7 using Incucyte. 

Results: Exosomes were identified as spherical vesicles, with a typical cup or spherical-shape, with diameters around 100 nm, and positivity for CD63 and TSG101. Hypoxia decreased cell apoptosis compared to normoxia in the presence of Paclitaxel: EC50: 1.74 ± 0.2 μM and 16.21 ± 0.29 μM; IC50: 0.18 ± 0.09 μM and 6.49 ± 0.11 μM for normoxic and hypoxic conditions, respectively; and carboplatin: EC50: 0.33 ± 0.17 μg/ml and 2.67 ± 0.07 μg/ml; IC50: 0.31 ± 0.09 μg/ml and 2.52 ± 0.08 μg/ml for normoxic and hypoxic conditions, respectively. Interestingly, exosomes isolated from cells cultured under hypoxia conditions induce cancer cell invasion and drug resistance in cells cultured under 8% O2.

Conclusions: In this study, we suggest that tumor cells use exosome-mediated transfer to communicate with neighboring cells to regulate their response to chemotherapy drugs.