Knockdown of affects tumorigenesis in human H1299 lung cancer cells by regulating and .

The transforming growth factor β regulator 4 () gene, located on the 7p14-p13 chromosomal region, is implicated in numerous types of cancer. However, the contribution(s) of in human lung cancer remains unknown. In the present study, the expression of mRNA was investigated in the H1299 lung cancer cell line using the quantitative polymerase chain reaction (qPCR) following the knockdown of by a lentivirus-mediated small interfering RNA (siRNA). Results identified that the expression of within H1299 cells was significantly suppressed (P<0.01) by RNA interference, and 586 genes were differentially expressed following silencing. Ingenuity Pathway Analysis (IPA) revealed that these genes were often associated with infectious diseases, organismal injury, abnormalities and cancer functional networks. Further IPA of these networks revealed that knockdown in H1299 cells deregulated the expression of 21 downstream genes, including the upregulation of DNA damage-inducible transcript 3 (), also termed CCAAT/enhancer-binding protein homologous protein, and downregulation of caveolin 1 () and ribonucleotide reductase regulatory subunit M2 (). Results were validated using qPCR and western blotting. Furthermore, immunohistochemical staining of TBRG4 protein identified that expression was markedly increased in carcinoma compared with in normal tissue. In conclusion, serves a role in the tumorigenesis of lung cancer via deregulation of , and . The results of the present study may be important in contributing to our understanding of as a target for lung cancer treatment.