Expression of RUNX3 protein in human lung adenocarcinoma: implications for tumor progression and prognosis

Runt-related transcription factor 3 belongs to the runt domain family of transcription factors that play a pivotal role during normal tissue development and tumorigenesis in several organs. We directed our attention to the expression of RUNX3 protein in human lung AC and non-neoplastic lung tissues, comparing the results with clinicopathological profiles. We evaluated the expression of RUNX3 protein in 17 pairs of lung AC and non-neoplastic lung tissue. Furthermore, 98 lung AC were studied to examine the frequency of RUNX3-positive cells. Western blot analysis showed a single band at 45 kDa in all 17 AC and non-neoplastic tissues. Immunohistochemistry revealed immunoreactivity in alveolar type II pneumocytes or Clara cells. RUNX3 was expressed more frequently in the carcinomas with a BAC component than in those without (P < 0.01). Lower RUNX3 levels were associated with poorly differentiated types (P = 0.049). The five-year survival rate was significantly higher in the 50 patients with higher levels of RUNX3 expression than in the 48 patients with lower levels (P = 0.027). The expression of RUNX3 protein in lung AC might play a pivotal role in tumor progression and patients' survival.