Keun-Hong Park

Chemical priming of natural killer cells with branched polyethylenimine for cancer immunotherapy

BackgroundDue to their powerful immune surveillance activity and ability to kill and clear cancer cells, natural killer (NK) cells are an emerging anticancer immunotherapeutic agent. Therefore, there is much interest in developing efficient technologies that further enhance the therapeutic antitumor efficacy of NK cells.MethodsTo produce chemically primed NK cells, we screened polymers with various electric charges and examined their ability to enhance the cytotoxicity of NK cells. The effect of primary amine and electric charges of 25 kDa branched polyethylenimine (25KbPEI) was investigated by fluorination of the chemical. The role of 25KbPEI in determining the major priming mechanism was investigated in terms of calcium influx into NK cells. In vivo therapeutic efficacy of chemically primed NK cells was evaluated against solid tumor mouse model of triple negative breast and ovarian cancers.ResultsChem_NK that was produced by the priming activity of 25KbPEI showed potent antitumor activity to various cancer cells. Chem_NK showed an activated phenotype, which manifests as increased expression of activating/adhesion/chemokine receptors and perforin accumulation, leading to enhanced migration ability and antitumor activity. Chem_NK display potent therapeutic efficacy against in vivo mouse model of triple negative breast and ovarian cancers. Fluorination of the primary amine group reduces the activity of 25KbPEI to prime NK cells, indicating that the cationic charge on the chemical plays a critical role in NK cell activation. A major priming mechanism was 25KbPEI-mediated calcium influx into NK cells, which occurred mainly via the Ca2+-permeable non-selective cation channel transient receptor potential melastatin 2.ConclusionsNK cells can be chemically primed with 25KbPEI to express potent antitumor activity as well as enhanced migration ability. Because PEI is a biocompatible and Food and Drug Administration-approved chemical for biomedical use, these results suggest a cost-effective and simple method of producing therapeutic NK cells.

Destablilization of TRAF6 by DRAK1 Suppresses Tumor Growth and Metastasis in Cervical Cancer Cells

Abstract The adaptor protein TNF receptor-associated factor 6 (TRAF6) is a key mediator in inflammation. However, the molecular mechanisms controlling its activity and stability in cancer progression remain unclear. Here we show that death-associated protein kinase-related apoptosis-inducing kinase 1 (DRAK1) inhibits the proinflammatory signaling pathway by targeting TRAF6 for degradation, thereby suppressing inflammatory signaling-mediated tumor growth and metastasis in advanced cervical cancer cells. DRAK1 bound directly to the TRAF domain of TRAF6, preventing its autoubiquitination by interfering with homo-oligomerization, eventually leading to autophagy-mediated degradation of TRAF6. Depletion of DRAK1 in cervical cancer cells resulted in markedly increased levels of TRAF6 protein, promoting activation of the IL1β signaling-associated pathway and proinflammatory cytokine production. DRAK1 was specifically underexpressed in metastatic cervical cancers and inversely correlated with TRAF6 expression in mouse xenograft model tumor tissues and human cervical tumor tissues. Collectively, our findings highlight DRAK1 as a novel antagonist of inflammation targeting TRAF6 for degradation that limits inflammatory signaling-mediated progression of advanced cervical cancer. Significance: Serine/threonine kinase DRAK1 serves a unique role as a novel negative regulator of the inflammatory signaling mediator TRAF6 in cervical cancer progression.