Adipose-derived exosomal miR-421 induces epigenetic reprogramming in ovarian cancer cells by targeting CBX7 (2291)

Document Type

Conference Proceeding

Publication Date


Publication Title

Gynecol Oncol


Objectives: Chromobox protein homolog 7 (CBX7), a member of the Polycomb repressor complex, is a potent epigenetic regulator and gene silencer. Our group previously reported that CBX7 functions as a tumor suppressor in ovarian cancer cells, and its loss accelerated the formation of carcinomatosis and drove tumor progression in an ovarian cancer mouse model. The goal of this study was to identify specific signaling pathways in the ovarian tumor microenvironment that can downregulate CBX7. Adipocytes are an integral component of the peritoneal cavity and the ovarian tumor microenvironment. Given its known pro-tumor functions, we hypothesized that the adipose microenvironment might be a main regulator of CBX7 expression. We report the characterization of exosomes derived from adiposities that regulate OC cell differentiation by releasing mir-421, a major regulator of CBX7 expression. Methods: Normal omentum was collected from female patients undergoing surgery for either benign or malignant conditions (age range: 30–80), and adipose-conditioned media (ACM) were obtained from these organ cultures. Human ovarian cancer cells used in this study include ATCC ovarian cancer (A2780, OVCA432, OVCAR3) and in-house cell lines (R182). Exosomes were isolated by serial centrifugation. Size and granularity were characterized using Nanosight, and cellular origin was determined using Exoview. mRNA and protein levels were determined by qPCR and western blot, respectively. Transfections were performed using a Lipofectamine transfection reagent. Results: Exosomes isolated from ACM decrease CBX7 protein levels without affecting its mRNA. These exosomes were characterized by higher expression of CD36 (adipocyte marker) compared to CD11b (macrophage marker) and showed a characteristic pattern of higher granularity suggesting a more complex cargo. Furthermore, they showed high levels of mir-421. Pre-treatment of ovarian cancer cells with the endocytosis inhibitor, nystatin, before culturing with ACM or exosomes, abolished the effect on CBX7. Furthermore, treatment of OC cells with anti-mir-421, but not control anti-mir, prior to the addition of adipose-derived exosomes abolished the effect on CBX7 expression. The direct binding of mir-421 to CBX7 3’ UTR was demonstrated by a significant decrease in luciferase activity when CBX7 3’ UTR plasmid was co-transfected with mir-421 (P = 0.0005, compared to control miRNA). Conclusions: We identified adipose-derived exosomal mir-421 as a specific signaling pathway in the ovarian tumor microenvironment that can downregulate CBX7 and induce an epigenetic change in ovarian cancer cells, which can drive disease progression. These findings open new venues to determine the value of targeting mir-421 to curtail ovarian cancer progression.

PubMed ID

Not assigned.



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