Panoply™ Human MDK Over-expressing Stable Cell Line

Ovarian cancer (OC) is a highly lethal disease, primarily due to intratumoral heterogeneity, resistance to conventional chemotherapy, and poor responses to targeted therapies and immunotherapies. Interferon-gamma (IFN-γ) is a promising therapeutic cytokine that has demonstrated efficacy in several clinical trials for ovarian cancer. However, its clinical application faces significant hurdles: high doses cause severe toxicity, whereas low doses trigger significant pro-metastatic side effects. Here, researchers discovered that ovarian cancer cells employ an adaptive strategy involving the upregulation of midkine (MDK); this mechanism simultaneously counteracts IFN-γ-induced anti-tumor activity and promotes IFN-γ-induced tumor metastasis. The study identifies MDK as a critical downstream target of IFN-γ in ovarian cancer, noting that this regulatory process is dose-dependent and mediated by STAT1. Gain-of-function experiments demonstrated that MDK overexpression promotes ovarian cancer cell proliferation and metastasis; this indicates that IFN-γ-activated MDK acts antagonistically to IFN-γ regarding tumor proliferation but synergistically regarding tumor metastasis. Furthermore, using the MDK inhibitor iMDK, the researchers evaluated the impact of MDK inhibition on IFN-γ-induced anti-proliferative and pro-metastatic effects. The results showed that inhibiting MDK significantly enhanced IFN-γ-induced growth inhibition and reversed IFN-γ-driven epithelial-mesenchymal transition (EMT) and metastasis in vitro.

To investigate the potential role of activated MDK in IFN-γ-mediated biological activities, researchers generated an MDK-overexpressing SKOV3 cell line and confirmed its expression at both the mRNA (Figure 1A) and protein (Figure 1B) levels. The study revealed a significant increase in the expression of the proliferation marker Ki67 in MDK-overexpressing SKOV3 cells (protein level: Figure 1B; mRNA level: Figure 1C), suggesting that MDK may promote ovarian cancer (OC) cell proliferation. Since the promotion of metastasis is a widely reported adverse effect of IFN-γ therapy, the researchers further evaluated the impact of MDK overexpression on OC metastasis. Transwell assays demonstrated that MDK overexpression significantly promoted the migration and invasion of OC cells (Figure 1D). The activation of epithelial-mesenchymal transition (EMT) is both a driver and a hallmark of cancer metastasis. By examining the expression of EMT molecular markers, the researchers found that MDK overexpression led to marked EMT activation, characterized by the loss of epithelial markers ZO1 (tight junction protein 1) and E-cad (E-cadherin) alongside the concurrent upregulation of mesenchymal markers vimentin and Slug; these changes were confirmed at both the protein (Figure 1E) and mRNA (Figure 1F) levels. Given that IFN-γ strongly induces MDK expression (even at very low concentrations), the researchers hypothesized that MDK might be involved in the process by which IFN-γ promotes metastasis.

Figure 1. MDK promotes cell proliferation, migration, and invasion in SKOV3 cells. (Liu Q, et al., 2022)