Abstract 2605: Exosomal transfer of microRNA and growth factors by human Mesenchymal Stem Cells support to breast cancer cells.

Abstract

Introduction: Recently our laboratory has shown that Serum Deprived Mesenchymal Stem Cells (SD-MSCs) have the surprising ability to survive for long periods (more than 60 days) by using autophagy. In addition, these SD-MSCs aid in tumor survival/growth both by paracrine effects of the secretome and by miRNAs production that act as post-transcriptional regulators and affect the regulation of protein-coding. There has been an explosion of interest in understanding the role of secreted microRNA by MSCs, presumably through exosomes. Exosomes are 50-90 nm vesicles that are secreted by various types of cells and made up of a double membrane of phospholipids that contain proteins, mRNA, and miRNA. It has been shown that exosomes secreted by cells affect a recipient cell by modifying its protein translation, thus, inducing a cascade of signaling events. In this study we characterize the exosomal fraction of non-apoptotic secretome of SD-MSCs.

Materials and Methods: MSCs were cultured in α-MEM without serum for 30 days. The culture supernatant was centrifuged to remove floating large debris and concentrated 120 times using an ultrafiltration cellulose membrane (cutoff 1kDa) mounted on a N2 positive pressure system (Amicon). Concentrated supernatant was centrifuged 1 hour at 100,000g to collect the exosome fraction. miRNA contained in exosomes was extracted using miRVana kit (Ambion) and screened for 704 different miRNA using a RT miRNA PCR array (SABiosciences). Proteins from exosomes were extracted using RIPA buffer. The trypsin digest of the Rapigest(tm)-resuspended pellet was analyzed using both nanoLC MALDI-TOF/TOF and nanoRSLC-ESI-LTQ-OrbiTrap MS/MS analyses.

Results: Our results show that at least 110 different miRNAs are expressed in exosomes from serum deprived MSCs including miR-34a, miR-199, miR-23 and let-7 series. These play a role in tumor survival/angiogenesis. Interestingly, we observed an enrichment expression of “passenger” miRNA (miRNA* or miRNA-3p/-5p). Proteomics revealed the presence of at least 281 different proteins from serum deprived-MSCs exosomes including but not limited to growth factors (IGF-2, PAI-1), growth-factors binding proteins (IGFBP-2, -3, -5, -7), transcription factor (AEBP1), integrins (α5, α11, β1), Ras family members (Rab10, Rap1A, Rap1B) and metalloproteinase inhibitors (TIMP1, TIMP2). The identified proteins map to pathways involved in cell growth and proliferation, cell death, cell-to-cell signaling and metabolism.

Conclusion: Our study revealed the complexity of exosomes secreted by serum deprived MSCs. The miRNAs and proteins detected could act as indirect post-transcriptional regulators (miRNA) or as direct signaling pathway regulators (growth factors/integrins). This cell to cell communication through exosomes could reveal a novel mechanism for paracrine regulation of stromal cells in solid tumors.

Citation Format: Patrice Penfornis, Krishna C. Vallabhaneni, Francois Guillonneau, Griffin Orr, Santosh Dhule, Radhika Pochampally. Exosomal transfer of microRNA and growth factors by human Mesenchymal Stem Cells support to breast cancer cells. [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 2605. doi:10.1158/1538-7445.AM2013-2605