Interactions of Omentin and Lactotransferrin in the Progression of Metastatic Ovarian Cancer

Abstract

Advanced stage serous ovarian cancer metastasizes preferentially to the omentum, which is a major site of intra‐abdominal fat accumulation and is covered by a layer of mesothelial cells (mesothelium). Ovarian cancer cells first adhere to and then penetrate through the mesothelium. It was previously shown the expression of adipokine omentin (ITLN1) in mesothelial cells was down‐regulated when mesothelial cells were co‐cultured with ovarian cancer cells. Survival correlation studies demonstrated that patients with serum ITLN1 levels of >350 ng/mL at the time of first treatment experienced longer survival times than those with lower levels of ITLN1. In addition, wound‐healing assay and invasion assay demonstrated that ovarian cancer cells (SKOV3 and A224) treated with physiological levels of ITLN1 showed a significant decrease in motility and invasion potential. However, the molecular mechanism by which ITLN1 modulates these malignant phenotypes remains unknown. Cancer cells migrate using cell‐matrix mechanocoupling mechanisms through paths generated by the degradation and remodeling of the extracellular matrix (ECM) and by force‐mediated deformation (powered by cell traction force from cancer cells). To explore whether omentin suppresses ovarian cancer invasion potential via inhibiting ECM proteolysis, RNA sequencing and pathway analyses were performed on ITLN1 treated cancer cells. Significantly lower levels of MMP1 (matrix metalloproteinase‐1) was found in cancer cells treated with ITLN1 than untreated cells, which was confirmed by qRT‐PCR analysis. Since ITLN1 has been shown to interact with LTF (lactotransferrin), and binding of LTF to its receptors LRP1 (low‐intensity lipoprotein‐receptor‐related protein 1) can transcriptionally upregulate MMP1, an in vitro pull‐down assay on purified LTF and recombinant ITLN1 in serum‐free media was first performed to confirm that ITLN1 interacts and binds with LTF. To determine whether ITLN1 can interfere with the binding of LTF to LRP1 on ovarian cancer cells, a Duolink proximity ligation assay was performed using both anti‐LTF and anti‐LRP1 antibodies. There was a significant decrease in fluorescent signals in cells that were treated with ITLN1 compared to the control. The results suggested that ITLN1 interacts with LTF and prevents LTF from binding to its receptor LRP1 on ovarian cancer cells. Furthermore, ITLN1 abrogated the effects of LTF on MMP1 expression in a dose‐dependent manner in ovarian cancer cells. LTF not only induced MMP1 expression, but also triggered an increase of cytosolic Ca2+ and cell traction force in ovarian cancer cells, which were attenuated by pre‐incubation with ITLN1. Taken together, these data suggest that ITLN1 suppressed LTF's effect on the motility and invasion potential of ovarian cancer cells by decreasing MMP1 expression and cell traction force generation through modulating a calcium dependent LTF‐LRP1 signaling pathway.Support or Funding InformationDepartment of Defense: grant W81XWH‐17‐1‐0146This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.