Exploration of mechanisms of inhibition of exosome secretion by novel drugs in ovarian cancer cells

Abstract

Exosomes are small extracellular vesicles that contain macromolecular cargo and play a significant role in intercellular communication. Several studies have cited exosomes as having a role in ovarian cancer progression. Various drugs can inhibit exosome secretion in cancer cells through distinct mechanisms. Recent experiments in our laboratory identified two novel drugs called “Tumor EXosome inhibitors” (TEXi1 and TEXi2). We hypothesize that TEXi1 and TEXi2 will inhibit exosome secretion in ovarian cancer cells through mechanisms similar to known exosome inhibitors. We used two ovarian cancer cell lines (OVCAR-3 and OVCAR-4) and normal fallopian tube secretory epithelial cells (FT33). Cells were treated with solvent (DMSO), known exosome inhibitors (GW4869, Nexhinib20), Hsp70 inhibitor (MKT-077), TEXi1, or TEXi2 for 48 hours. Immunoblots were performed to evaluate expression of proteins involved in exosome biogenesis and secretion. Nanoparticle tracking analysis was used to determine if TEXi1 and/or TEXi2 treatment blocks total exosome secretion. We observed that TEXi1 and/or TEXi2 were effective in reducing exosome secretion as quantified by luciferase assay. Differential expression of several exosome markers was observed in the whole cell lysates following drug treatment. CD63 levels were reduced in exosomes following TEXi1 and TEXi2 treatment. These results were also validated using NanoSight. TEXi1 and TEXi2 inhibited exosome secretion in ovarian cancer cells, serving as potential treatment methods to prevent ovarian cancer progression. These findings can serve as further research to block ovarian cancer metastasis in vivo.