Paired samples t test was performed for 60 cases of lung adenocarcinoma tissues (2.709±0.323) and adjacent normal tissues (3.163±0.21) in GSE19804 and 44 cases of that (2.128±0.308 vs 2.936±0.188) in GSE18842, finding that the expression of HHIP mRNA in cancer tissues significantly down-regulated(Fig 1A and 1B) and the difference were statistically significant (P < 0.001). The gene discussed is HHIP; the disease is cancer.