Characterization of Metastasis Associated Genes and Development of Clinical Prognosis Assay for Lung Cancer
|Keywords:||肺癌;轉移;lung cancer;metastasis||Issue Date:||2006||Abstract:||
Research investigations on the molecular basis of lung carcinoma metastasis are helpful to identify therapeutic targets for metastasis. An accurate prognosis and selection of therapeutic modality determines the survival of cancer patients. Therefore, this thesis aims to characterize metastasis associated genes and develop clinical prognosis assay for lung cancer.
Firstly an in silico analysis approach was used to examine metastasis associated genes by a cell line model of human lung adenocarcinoma with different invasive abilities. After screening, one interesting gene was found, human kallikrein 8 (KLK8), a member of human tissue kallikrein gene family. The serine protease KLK8 protein (hK8) is known to be a favorable prognostic marker in ovarian cancer, but the biological basis of this is not understood. The experimental results showed that overexpressing the KLK8 gene in highly invasive lung cancer cell lines suppressed their invasiveness. This role in invasiveness was further confirmed by the fact that inhibition of endogenous KLK8 expression with a specific short hairpin RNA enhanced cancer cell invasiveness. In situ degradation and cell adhesion assays showed that proteins produced from KLK8 splice variants modify the extracellular microenvironment by cleaving fibronectin. DNA microarray experiments and cell staining for actin filaments revealed that the degradation of fibronectin by hK8 suppresses integrin signaling and retards cancer cell motility by inhibiting actin polymerization. In addition, studies in a mouse model coupled with detection of circulating tumor cells by quantitative PCR for the human Alu sequence demonstrated that KLK8 suppresses tumor growth and invasion in vivo. Furthermore, studies of clinical specimens from non-small cell lung cancer (NSCLC) patients showed a 52% recurrence rate for early-stage (stage I & II) patients with low KLK8 expression in their tumor cells and a 23% recurrence rate for patients with high KLK8 expression. Collectively, these findings show that KLK8 retards cancer metastasis and that further investigation of KLK8 as a prognostic marker for NSCLC is warranted.
The most promising way to improve prognosis is by means of early metastasis detection. Thus, the other project in this thesis study is focused on detection of disseminated cancer cells of non-small cell lung cancer patients in their peripheral blood. Current lung cancer staging and prognosis methods are based on imaging methods which may not be sensitive enough for early and accurate detection of metastasis. A panel of markers was validated for circulating cancer cell detection to improve the accuracy of cancer staging, prognosis, and as a rapid assessment of therapeutic response. NCI-CGAP database was used to identify potential marker genes for the detection of circulating cancer cells in peripheral blood. A panel of 4 marker genes was identified and experimentally validated. With these marker genes, the results achieved an overall positive detection rate of 72% for circulating cancer cells in the peripheral blood of 54 NSCLC patients. Nested real-time quantitative PCR (qPCR) and a scoring method using cancer cell load, Lc, were employed to correlate the amount of circulating cancer cells with clinical outcomes in NSCLC patients. Patients who had higher Lc values had worse outcomes and shorter survival times. Patients with poor therapeutic response were revealed by positive detection of circulating cancer cells after therapy. The results correlated well with the patients’ survival time. Circulating cancer cell detection by a panel of markers and the Lc scoring method can supplement the current TNM staging method for improved prognosis and for rapid assessment of therapeutic response. Together, they may facilitate the design of better therapeutic strategies for the treatment of NSCLC patients.
|Appears in Collections:||分子醫學研究所|
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