Abstract 2048: Stat3 downstream transthyretin stimulates tumor growth through regulation of tumor, immune and endothelial cells

Lung cancer is a very aggressive malignant form of cancer, and is one of the biggest public health challenges facing the United States and many other countries. Although incidence rates have been stabilized, an estimated 154,050 Americans are expected to die from lung & bronchus cancer in 2018, accounting for approximately 25.3 percent of all cancer deaths. Lung cancer is a difficult disease to detect in its early stages, with greater than 50% of patients diagnosed with lung cancer presenting with metastatic disease. Early detection of lung cancer is an important opportunity for decreasing mortality while it is still treatable and curable. The overall 5-year survival rate is ~15 percent. Thus, it is essential to better understand the mechanisms that initiate lung carcinogenesis and find easy-use biomarkers for more accurate lung cancer detection. Due to heterogeneity of lung cancers, a panel of biomarkers should be used for more accurate lung cancer detection and classification. Signal transducer and activator of transcription 3 (Stat3) is well known for its lung cancer-promoting activity. To assess the consequences of STAT3 persistent activation in the lung, a doxycycline-controlled CCSP-rtTA/(tetO)7-Stat3C bitransgenic mouse model was generated that over-expresses STAT3C (a constitutively active form of STAT3) in alveolar type II (AT II) epithelial cells. In sequential steps, Stat3C over-expression up-regulated pro-inflammatory molecules, increased inflammatory cell infiltration and caused adenocarcinomas in the lung. Using this lung tumor model, thirteen secretory proteins that are Stat3 downstream gene products were identified as a panel of biomarkers for lung cancer detection in human sera. This panel of biomarkers potentially differentiates different types of lung cancer for classification. Among them, the transthyretin (TTR) concentration was highly increased in human serum of lung cancer patients. TTR concentration was also induced in the serum, bronchoalveolar lavage fluid, alveolar type II epithelial cells and alveolar myeloid cells of the CCSP-rtTA/(tetO)7-Stat3C lung tumor mouse model. Recombinant TTR stimulated lung tumor cell proliferation and growth, which were mediated by activation of mitogenic and oncogenic molecules. TTR possesses cytokine functions to stimulate myeloid cell differentiation, which are known to play roles in tumor environment. TTR demonstrated a great influence on a wide spectrum of endothelial cell functions to control tumor and immune cell migration and infiltration. TTR-treated endothelial cells suppressed T cell proliferation. Taken together, Stat3 downstream inducible secretory protein biomarkers potentially can be used as clinical targets for lung cancer personalized treatment if their expression levels are increased in a given lung cancer patient in the blood. Citation Format: Xinchun Ding. Stat3 downstream transthyretin stimulates tumor growth through regulation of tumor, immune and endothelial cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2048.