서강대학교

초록/요약

The carcinogenesis is a complex, long-term, and multi-step process requiring several genetic modifications. Cancer chemoprevention is defined as a use of phytochemicals, to inhibit, delay or reverse the carcinogenesis or prevent the development of cancer. Therefore, halt or at least retard the carcinogenic process by phytochemicals, can help prevent the formation of tumors or interrupt the later stages of cancer progression. Cancer stem cells (CSCs) are cancer cells that possess the ability to self-renewal and to cause the heterogeneous lineages of cancer cells that comprise the tumor. It has been involved in throughout the cancer development including tumor formation, migration, invasion, metastasis therapeutic resistance, and recurrence. In this study, cancer preventive effects of phytochemicals on CSCs model were evaluated. In the preliminary research, it was investigated the potential CSCs inhibition by phytochemical, it was utilized the octamer-binding transcription factor (Oct4) luciferase assay system which contains a binding site of Oct4 as a screening tool for potential CSCs inhibitors from phytochemicals. Oct4 is a key regulator of pluripotent cell maintenance in embryonic stem cells (ESCs) or CSCs. According to preliminary research, two phytochemicals, curcumin (CUR) and phenethyl isothiocyanate (PEITC) highly inhibited the Oct4 transcriptional activity among 203 phytochemicals tested in luciferase assay system. In the first research part as described in chapter III, it was investigated for the mechanism study of CUR against Oct4 signaling in NCCIT human embryonic carcinoma cells which express high levels of endogenous Oct4. CUR significantly inhibited Oct4 mRNA and protein levels as well as increased apoptotic cell death as confirmed by sub-G0/G1 contents, cleaved caspases, and proapoptotic protein levels and a series of loss-of-function experiments using Oct4 siRNA. Furthermore, CUR induced marked GSK-3β activation, resulting in an increase in apoptotic cell death. In the second research part as described in chapter IV, it was evaluated for the effect of PEITC on CSC model in vitro and in a xenograft model using cell surface antibody-based sorting system. In order to sort CSCs, it was used the specific CSCs-surface marker such as epithelial cell adhesion molecule (EpCAM). EpCAM is involved in increasing the functionality of the CSCs. PEITC treatment suppressed expression of the pluripotency factors in this model as well as the self-renewal capacity and clonogenicity. PEITC also inhibited tumor formation in a mouse model of tumorigenesis. In the third research part as described in chapter V, it was performed the additional studies for role of microRNAs (miRNAs) in CSCs using miRNA sequencing. MiRNAs are known to be involved in the maintenance of CSCs. It was investigated the differential expression of miRNAs in SK-OV-3 human ovarian CSCs compared to non-CSCs using two ovarian CSC-specific surface markers, CD44 and CD117. It was detected the four up-regulated miRNAs and miR-424-5p was only validated by real-time qPCR. Moreover, pathway analysis indicated that most miR-424-5p target genes are involved in cancer-related biological pathways. Taken together, CUR and PEITC could be developed as potential cancer chemopreventive agents for prevent or treatment of human cancer by suppressing CSC and the therapeutic strategies targeted CSC-related miRNAs may be effective for cancer chemoprevention and/or therapy.