Role of Sp-Family in Lung Tumorigenesis

Lung cancer is the leading cause of cancer mortality and the prognosis for lung carcinoma patients is generally poor (5-yr survival rate < 15%) in Taiwan, even if diagnosed and treated successfully, patients with early stage of lung carcinoma have a 5-year survival rate of only 70% after surgical resection. Understanding of the molecular attributes of lung tumors provides clues to develop therapies targeted to correct defective cellular pathways for lung cancer. The transcription factor, specificity protein (Sp) 1 was found to be overexpressed in several human cancers and the Sp1 levels correlated with tumor grade/stage and poor prognosis. Sp1 was shown to be involved in tumor development through transcriptional regulation of genes related to cell survival and proliferation. However, whether Sp1 is required for oncogene-induced tumor development is still unknown. The role of Sp1 in tumor metastasis is also not well studied. The overall objective of the proposed research is to identify the potential contribution of Sp1 to Kras-induced lung tumor growth and metastasis. To achieve our purpose, it is important to ascertain Sp1 is involved in lung tumorigenesis. In specific aim 1, Sp1 level will be investigated in lung cancer patients and correlated with prognosis or metastasis. In specific aim 2, we will establish a pattern of gene expression in lungs from transgenic mice with doxycycline-induced KrasG12D activation in the presence or absence of Sp1 inhibitor, mithramycin A. In specific aim 3, the contribution of Sp1 to Kras-induced lung tumorigenesis in tamoxifen-inducible Sp1 knockout mice will be studied. In specific aim 4 whether Sp1 regulates lung tumor metastasis and epithelial-mesenchymal transition will be studied. Our preliminary results show that Sp1 was overexpressed in clinical resected human lung cancer compared to normal lung tissue and downregulated in stage IV of lung cancer. We have established a mouse model for doxycycline-induced lung tumorigenesis. Sp1 was increased significantly with doxycycline-induced upregulation of KrasG12D and appearance of lung adenocarcinomas. In addition, we also found that Sp1 level is overexpressed and downregulated in low and highly invasive lung cancer cells, respectively. Therefore, in this study, we will uncover mechanisms underlying Sp1-regulated lung tumorigenesis controlled by KrasG12D. To accomplish the proposed study, a doxycycline-inducible mouse model bearing lung tumor has been established and tamoxifen-inducible Sp1 knockout mice is under establishing now. Genotyping, histological analysis, Western blotting analysis, transfection, reporter assay, in vitro matrigel-combined transwell invasion assay and migration assay will be conducted in the proposal. We expect to finish this proposed study within 3 years. Understanding of functional role of Sp1 in lung tumorigenesis will provide information to develop a new therapeutic strategy targeting Sp1 or combinational therapies targeting Kras and Sp1 simultaneously for lung cancer therapy.