Introduction: Our previous study has demonstrated that 15-Lipoxygenase-2 (15-LOX-2) is significantly reduced in carcinoma cells of head and neck in vivo and in vitro and is a tumor suppressor in head and neck cancer. CCAAT/enhancer binding protein alpha (C/EBPα)is a transcriptional factor that belongs to the basic leucine zipper protein family and plays a crucial role in regulating the balance between cell proliferation and differentiation. In this study, we investigate if 15-LOX-2 promoter is regulated by C/EBPα in carcinoma cells of head and neck. Method: In this study, we independently cloned 15-LOX-2 promoter fragments [LF1 (-1533/-87), LF2 (-628/+87), LF3 (-253/+87), LF4 (-153/+87) and LF5 (-33/+87)], and assessed an activity of each promoter fragment in normal human adult keratinocytes (NHEK) and human carcinoma cells of head and neck (Fadu). Furthermore, each of the above 15-LOX-2 promoter fragments was co-transfected with C/EBPα expression vector in the Fadu cells. Forty eight hours later, the cells were harvested into lysis buffer for a subsequent measurement of luciferase activity. Lysates containing equal amounts of protein were assayed for luciferase activity using luciferase assay kit. Result: The luciferase reporter assay showed that 15-LOX-2 promoter fragments (LF1, LF2, LF3, LF4 and LF5) are active in the NHEK and Fadu cells. The pattern of the relative activity profile is similar in both NHEK and Fadu cells; the relative activity of the fragment LF3 (-253/+87) was highest in both cell lines. Overexpression of C/EBP α significantly enhance the luciferase activity of the 15-LOX-2 promoter fragments (LF1, LF2, and LF3), but has no effect on the luciferase activity of the LF4 and LF5. The luciferase activity of the LF2 fragment (-628/+87) which contains 10 binding elements of C/EBP α mainly was the highest (two-fold). Conclusion: The results from this study indicate that C/EBPα is able to regulate the 15-LOX2 promoter in carcinoma cells of head and neck. Additional studies are needed to confirm the binding of C/EBPα to 15-LOX-2 promoter.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA