STAT reporter cell line systems as a tool for cancer therapeutic target screening.

Abstract

Abstract Signal transducer and activator of transcription (STAT) proteins as cytoplasmic transcription factors respond to cytokines and growth factors that mediate downstream signaling. STATs are closely related with cancers as they are frequently found to be dysregulated in primary tumors, leading to enhanced survival of tumors and increased angiogenesis. Among seven STAT family members, STAT3, STAT4 and STAT5 are considered to primarily promote cancer development and progression, while STAT1 may function either as a tumor suppressor or tumor promoter. STAT3, 4 and 5 are persistently activated in many human cancer cell lines, leading to increased cancer cell survival. Several studies demonstrate that inhibition of STAT3 or STAT5 signaling decreases cancer cell proliferation leading to apoptosis. Taken together, these indicate that STAT proteins can be ideal targets for anti-cancer therapy, and so it is crucial to develop assay systems that can identify inhibitors targeting those pro-tumorigenic STATs. Hence we developed the four reporter cell lines, each of which stably expresses STAT1-, STAT3-, STAT4-, or STAT5-response element that controls an optimized Renilla luciferase reporter gene upon stimulation. Functional activity of each cell line was evaluated through dose response of various cytokines such as IFNs, IL-3 and IL-6. One of the STAT inhibitors, curcumin as well as other putative STAT suppressors were utilized to characterize how each STAT can differentially respond to each test molecule and how its response can affect the host cells.