Kyu Kwang Kim

Mechanism of Inhibition of the MeTC7 Ligand That Covalently Binds to VDR To Reduce PD-L1 Expression

Cancer-associated overexpression of the Vitamin D Receptor (VDR) is associated with good or poor prognosis, depending on the cancer type and stage. Here, we show that VDR is overexpressed in ovarian malignant tissues and upregulates PD-L1 surface expression in tumor cells, enabling immune evasion by the tumors. MeTC7, a VDR antagonist, has demonstrated strong inhibition of PD-L1 expression in vitro and in vivo. Using structural mass spectrometry and biophysical methods, we showed that MeTC7 binds covalently to VDR in the canonical ligand-binding pocket. Using ligand excess, additional covalently bound molecules were observed. Hydrogen-deuterium exchange mass spectrometry revealed that MeTC7 binding prevents optimal folding of the C-terminal region of VDR and impacts H10, which is part of the dimerization interface. Overall, our findings highlight a new mechanism of action for a VDR antagonist ligand and provide support for the use of the MeTC7 antagonist to inhibit PD-L1 and block tumorigenesis.

Role of trypsin and protease-activated receptor-2 in ovarian cancer

Proteases have been implicated in the tumorigenesis and aggressiveness of a variety of cancer types. In fact, proteases have proven to be very clinically useful as tumor biomarkers in the blood of patients. Proteases are typically involved in complex systems of substrates, activators, and inhibitors, thus making our ability to establish their exact function in cancer more difficult. Trypsin, perhaps the most famous of proteases, has been shown to play a role in cancer progression, but its functional role in ovarian cancer has not been much studied. PAR2, a transmembrane receptor that is known to be activated by trypsin, has been reported to be associated with ovarian cancer. Here, we found that stimulation of ovarian cancer cell lines with trypsin or PAR2 activating peptide markedly increased MAPK signaling and cell proliferation. Additionally, HE4, a WAP-family glycoprotein and ovarian cancer biomarker, was found to inhibit trypsin degradation, thereby retaining its activity. Patient data seemed to support this phenomenon, as the serum of ovarian cancer patients with high HE4 expression, revealed significantly elevated trypsin levels. These data support the hypothesis that trypsin plays a tumorigenic role in ovarian cancer, which can be mediated by its receptor PAR2, and potentiated by HE4.

The NF-κB-HE4 axis: A novel regulator of HE4 secretion in ovarian cancer

Ovarian cancer is the leading cause of death among gynecologic malignancies. Despite recent advancements in targeted therapies such as PARP inhibitors, recurrence is common and frequently resistant to existing therapies. A powerful diagnostic tool, coupled with a comprehensive understanding of its implications, is crucial. HE4, a clinical serum biomarker for ovarian cancer, has shown efficacy in monitoring malignant phenotypes, yet little is known about its biological role and regulatory mechanisms. Our research demonstrates that HE4 expression in ovarian cancer can be regulated by the NF-κB signaling pathway. We found that the activation of NF-κB signaling by tumor necrosis factor (TNF)-α, a cytokine found in ovarian cancer tumors and ascites, enhanced the secretion of HE4 while its inhibition suppressed HE4 levels. Nuclear translocation of the NF-κB component p65 was found to be critical for HE4 expression; induced NF-κB activation through p65 expression or constitutive IKK2 activity elevated HE4 expression, while p65 knockdown had the opposite effect. Furthermore, we observed that NF-κB mediated HE4 expression at the transcriptional level. Our data also suggests that there is a regulatory role for HE4 in the expression of α5-Integrin, a crucial adhesion molecule in ovarian cancer metastasis; HE4 knockdown corresponded with reduced α5-Integrin expression, cell migration and cell adhesion to fibronectin.