삼중음성유방암에서 STC-1의 기능과 STC-1 억제제로서 zerumbone의 역할 규명

Abstract

Breast cancer is a leading cause of cancer deaths among woman cancer and is routinely assessed for diagnosis through expression of estrogen receptor (ER) positive, human epidermal growth factor receptor type 2 (HER2, also called ERBB2) amplified and triple negative breast cancer (TNBC) by mRNA expression and immunohistochemistry (IHC). In recent years, Hierarchical clustering with gene expression pattern has been classified to four different subtypes with distinct clinical outcomes: a luminal group (luminal A, B), a HER2 amplified group, and a basal-like group (predominantly lack of ER, PR, and HER2 expression). Unlike ER or HER2 amplified breast cancer subtypes, TNBC has only limited clinical choice such as chemotherapy and surgery. TNBC has a potent metastatic capacity via aberrant expression of various signaling molecules, including receptors and chemokines. In the second part of this study, the role of Stanniocalcin-1 (STC-1) was investigated in TNBC cells. Although STC-1 is involved with prognosis in several cancers, the role of STC-1 has not been fully elucidated in breast cancer. Using the publicly available datasets, I found that the level of STC-1 expression was associated with poor prognosis such as relapse free survival (RFS). So I investigated the level of STC-1 expression in various breast cancer cell lines. My results showed that the level of STC-1 expression was higher in TNBC cells than in non-TNBC cells. Interestingly, the cell invasion rates of TNBC were significantly increased by recombinant human STC-1 treatment. In contrast, STC-1 siRNA overexpressed TNBC cells were decreased cell invasion rates. To verify the regulatory mechanism of STC-1-induced cell invasion, I treated TNBC cells with recombinant human STC-1. I found that recombinant human STC-1 triggered the phosphorylation of JNK in Hs578T and MDA-MB231 TNBC cells. STC-1-induced cell invasion was dramatically decreased by SP600125, JNK inhibitor, or STC-1-blocking antibody. Thus, I demonstrated that STC-1 is associated with poor prognosis of TNBC and its induction directly regulated the cell invasion of TNBC through the activation of JNK. Next, I investigated a cause of aberrant STC-1 expression in TNBC cells. Using the chemokine array, I found that Interleukin 1β (IL-1β) expression significantly increased in Hs578T TNBC cells compared with MCF7 non-TNBC cells. In general, IL-1β has been related to tumor proliferation, invasion and metastasis in various cancers including breast cancer. Interestingly, the basal level of STC-1 expression was increased by IL-1β treatment. In addition, my results showed that IL-1β triggered the phosphorylation of Akt and NF-κB in Hs578T cells. So, I transiently transfected Hs578T cells with constitutively active Akt1 (CA-Akt) and wild type NF-κB genes. STC-1 expression was significantly increased by CA-Akt or NF-κB overexpression in Hs578T cells. So, I investigated whether Akt1 is crosstalk to NF-κB. Interestingly, IL-1β-induced p-NF-κB p65 was inhibited by LY294002, PI-3K inhibitor in Hs578T cells. CA-Akt1 also led phosphorylation of NF-κB p65 in Hs578T cells. Therefore, I demonstrated that STC-1 expression upregulated through PI-3K/Akt/NF-κB dependent pathway in TNBC cells. In third part, the effect of zerumbone (ZER) as STC-1 inhibitor was investigated. ZER is phytochemical substance isolated from the subtropical plant zingiber zerumbet Smith, which possesses anti-inflammatory activity in several cancers. I found that ZER significantly decreased STC-1 expression in breast cancer cells. I also observed that ZER suppresses basal level of NF-κB and Akt activity in Hs578T cells. IL-1β-induced STC-1 expression was also decreased by ZER treatment. Interestingly, ZER only suppressed IL-1β-induced NF-κB phosphorylation but not Akt phosphorylation. Finally, IL-1β-induced cell invasion were decreased by ZER in Hs578T cells. Conclusively, ZER suppresses basal as well as IL-1β-induced cell invasion of TNBC through the down-regulation of STC-1. Therefore, I suggest that ZER could be a promising therapeutic drug for treatment of TNBC patients.