Supplementary Figure 1. MMP-9 activity is involved in EOC invasion through HPMC. Supplementary Figure 2. Inhibition of exosome secretion attenuates CD44 uptake by HPMCs and suppresses TYK-nu cell invasion. Supplementary Figure 3. Inhibition of exosome uptake attenuates CD44 expression in HPMCs. Supplementary Figure 4. Immunofluorescent analyses. Supplementary Figure 5. Not only CD44 but MMP-9 are strongly expressed in peritoneal mesothelial cells interacting with ovarian cancer cells. Supplementary Figure 6. Acquisition of CD44 of mouse omental tissues from ovarian cancer cells is dose-dependent. Supplementary Table 1. Clinical characteristics of ovarian cancer patients with stage III-IV consecutively treated at Osaka University Hospital between 2011 and 2015.
Funding
Ministry of Education, Science, Sports and Culture of Japan
Takeda Science Foundation
Osaka Medical Research Foundation
ARTICLE ABSTRACT
Epithelial ovarian cancer (EOC) cells metastasize within the peritoneal cavity and directly encounter human peritoneal mesothelial cells (HPMC) as the initial step of metastasis. The contact between ovarian cancer cells and the single layer of mesothelial cells involves direct communications that modulate cancer progression but the mechanisms are unclear. One candidate mediating cell–cell communications is exosomes, 30–100 nm membrane vesicles of endocytic origin, through the cell–cell transfer of proteins, mRNAs, or microRNAs. Therefore, the goal was to mechanistically characterize how EOC-derived exosomes modulate metastasis. Exosomes from ovarian cancer cells were fluorescently labeled and cocultured with HPMCs which internalized the exosomes. Upon exosome uptake, HPMCs underwent a change in cellular morphology to a mesenchymal, spindle phenotype. CD44, a cell surface glycoprotein, was found to be enriched in the cancer cell–derived exosomes, transferred, and internalized to HPMCs, leading to high levels of CD44 in HPMCs. This increased CD44 expression in HPMCs promoted cancer invasion by inducing the HPMCs to secrete MMP9 and by cleaning the mesothelial barrier for improved cancer cell invasion. When CD44 expression was knocked down in cancer cells, exosomes had fewer effects on HPMCs. The inhibition of exosome release from cancer cells blocked CD44 internalization in HPMCs and suppressed ovarian cancer invasion. In ovarian cancer omental metastasis, positive CD44 expression was observed in those mesothelial cells that directly interacted with cancer cells, whereas CD44 expression was negative in the mesothelial cells remote from the invading edge. This study indicates that ovarian cancer–derived exosomes transfer CD44 to HPMCs, facilitating cancer invasion.Implications: Mechanistic insight from the current study suggests that therapeutic targeting of exosomes may be beneficial in treating ovarian cancer. Mol Cancer Res; 15(1); 78–92. ©2016 AACR.
