Kyung-Ae Lee

Both E6 and E7 Oncoproteins of Human Papillomavirus 16 Inhibit IL-18-Induced IFN-γ Production in Human Peripheral Blood Mononuclear and NK Cells

Cervical carcinoma is the predominant cancer among malignancies in women throughout the world, and human papillomavirus (HPV) 16 is the most common agent linked to human cervical carcinoma. The present study was performed to investigate the mechanisms of immune escape in HPV-induced cervical cancer cells. The presence of HPV oncoproteins E6 and E7 in the extracellular fluids of HPV-containing cervical cancer cell lines SiHa and CaSki was demonstrated by ELISA. The effect of HPV 16 oncoproteins E6 and E7 on the production of IFN-γ by IL-18 was assessed. E6 and E7 proteins reduced IL-18-induced IFN-γ production in both primary PBMCs and the NK0 cell line. FACS analysis revealed that the viral oncoproteins reduced the binding of IL-18 to its cellular surface receptors on NK0 cells, whereas there was no effect of oncoproteins on IL-1 binding to its surface IL-1 receptors on D10S, a subclone of the murine Th cell D10.G4.1. In vitro pull-down assays also revealed that the viral oncoproteins and IL-18 bound to IL-18R α-chain competitively. These results suggest that the extracellular HPV 16 E6 and E7 proteins may inhibit IL-18-induced IFN-γ production locally in HPV lesions through inhibition of IL-18 binding to its α-chain receptor. Down-modulation of IL-18-induced immune responses by HPV oncoproteins may contribute to viral pathogenesis or carcinogenesis.

Hesperidin Induces Apoptosis by Inhibiting Sp1 and Its Regulatory Protein in MSTO-211H Cells

Hesperidin, a flavanone present in citrus fruits, has been studied as potential therapeutic agents that have anti-tumor activity and apoptotic effects in several cancers, but there is no report about the apoptotic effect of hesperidin in human malignant pleural mesothelioma through the specificity protein 1 (Sp1) protein. We investigated whether hesperidin inhibited cell growth and regulated Sp1 target proteins by suppressing the levels of Sp1 protein in MSTO-211H cells. The IC50 value of hesperidin was determined to be 152.3 μM in MSTO-211H cells for 48 h. Our results suggested that hesperidin (0-160 μM) decreased cell viability, and induced apoptotic cell death. Hesperidin increased Sub-G1 population in MSTO-211H cells. Hesperidin significantly suppressed mRNA/protein level of Sp1 and modulated the expression level of the Sp1 regulatory protein such as p27, p21, cyclin D1, Mcl-1, and survivin in mesothelioma cells. Also, hesperidin induced apoptotic signaling including: cleavages of Bid, caspase-3, and PARP, upregulation of Bax, and down-regulation of Bcl-xl in mesothelioma cells. These results show that hesperidin suppressed mesothelioma cell growth through inhibition of Sp1. In this study, we demonstrated that Sp1 acts as a novel molecular target of hesperidin in human malignant pleural mesothelioma.

Development of screening systems for drugs against human papillomavirus-associated cervical cancer: based on E6-E6AP binding.

Human papillomavirus (HPV) E6 protein forms a ternary complex with the cell-cycle regulator p53 and the E6-associated protein (E6AP) known as an E3 ubiquitin protein ligase, leading to the degradation of p53 via the ubiquitination pathway. As an attempt to employ interaction between HPV viral oncogene E6 and a cellular protein E6AP for in vitro screening system of drugs against HPV infection, we primarily investigated the E6AP-E6 binding through pull down assay and enzyme-linked immunosorbent assay (ELISA). E6AP immobilized on the resin produced specifically complexes with bacterially expressed E6 in a dose-dependent manner, as determined by immunoblot analysis. This result was collinear with that shown in ELISA, which is a useful system for mass-screening potential drugs with rapidity and cheapness. Screening system based on the interaction between E6AP and E6 may be a promising system in the development of drugs against cervical cancer caused by HPV infection.