BTG3 is identified as a tumor suppressor gene in some malignancies. Btg3-deficient mice display a higher incidence of lung cancer. These results suggest that BTG3 plays an important role in lung tumorigenesis, although the underlying mechanisms are unknown. The BTG3 expression was detected using immunohistochemical staining and our results showed that the expression of BTG3 was reduced in lung cancer compared to benign lung tissues. We identified two BTG3 isoforms present in lung cancer: Full-length BTG3 and BTG3b lacking the 44 amino acids. BTG3 was predominantly expressed in benign lung tissues, whereas its expression was generally undetectable in lung cancer and cancer cell lines. Functional analysis revealed that BTG3 but not BTG3b inhibited lung cancer growth. Our results disclosed an important role of BTG3 in lung tumorigenesis. (C) 2013 Elsevier Inc. All rights reserved.