MicroRNA-503-5p Inhibits the CD97-Mediated JAK2/STAT3 Pathway in Metastatic or Paclitaxel-Resistant Ovarian Cancer Cells

CD97 shows a strong relationship with metastasis and poor clinical outcome in various tumors, including ovarian cancer. The expression of CD97 in metastatic ovarian cancer cells was higher than that in primary ovarian cancer cells. Mature miRNAs are frequently de-regulated in cancer and incorporated into a specific mRNA, leading to post-transcriptional silencing. In this study, we investigated whether the miR-503-5p targeting of the CD97 3′-untranslated region (3′-UTR) contributes to ovarian cancer metastasis as well as the underlying mechanism regulating cancer progression. In LPS-stimulated or paclitaxel-resistant ovarian cancer cells, stimulation with recombinant human CD55 (rhCD55) of CD97 in ovarian cancer cells activated NF-κB-dependent miR-503-5p down-regulation and the JAK2/STAT3 pathway, consequently promoting the migratory and invasive capacity. Furthermore, restoration of miR-503-5p by transfection with mimics or NF-κB inhibitor efficiently blocked CD97 expression and the downstream JAK2/STAT3 signaling pathway. Target inhibition of JAK with siRNA also impaired colony formation and metastasis of LPS-stimulated and paclitaxel-resistant ovarian cancer cells. Taken together, these results suggest that high CD97 expression, which is controlled through the NF-κB/miR-503-5p signaling pathway, plays an important role in the invasive activity of metastatic and drug-resistant ovarian cancer cells by activating the JAK2/STAT3 pathway.