Exosomal Transfer of Stromal Cell-Derived miR21 Confers Taxol Resistance in High-grade Serous Ovarian Cancer Cells Through Down-Regulation of APAF1.

Advanced ovarian cancer usually spreads to the visceral adipose tissue of the omentum. However, the stromal cell-derived molecular determinants that modulate ovarian cancer growth have not been characterized. Here, we identified significantly higher levels of miR21 in exosomes and tissue lysate isolated from cancer associated adipocytes (CAA) and fibroblasts (CAF) compared to those from ovarian cancer cells. Functional studies and transcriptome analysis on miR21 transfected SKOV3 ovarian cancer cells revealed that miR21 could be transferred from CAA or CAF to ovarian cancer cells and modulate ovarian cancer apoptosis and chemoresistance through binding to its direct target APAF1. These data suggest that malignant phenotype of metastatic ovarian cancer cells can be modulated by miR21 delivered by exosomes derived from neighboring stromal cells in the omental tumor microenvironment. SKOV3 cells were transfected with either 5 nM miR21 precursor or negative control precursor miRNA for 24 h; and total RNAs were isolated using TRI reagent (Molecular Research Center). Purified RNA samples were amplified and labeled using MessageAmp™ Premier RNA Amplification Kit (Ambion) and then hybridized onto Affymetrix GeneChip Human Genome U133 Plus 2.0 microarrays (Affymetrix, Santa Clara, CA), according to the manufacturer’s protocol. The arrays were washed and stained using Affymetrix Fluidics Station 450 and GeneChip® Hybridization, Wash, and Stain Kit (Affymetrix). Scanning of the arrays were done at the Cancer Genomics Core Lab at MD Anderson Cancer Center using the GeneChip Scanner 3000 7G (Affymetrix).