TTF1 and cancer: Recent evidence showed that TTF-1, as a lineage-specific oncogene, was dominantly expressed in lung cancer, but not other types of cancers, and its expression level was closely correlation with the prognosis of lung cancer patients.20, 21, 22, 23 These findings raise an interesting question whether promoter of TTF-1 gene might be an ideal candidate for therapeutic strategy of targeted expression of distinct genes in lung cancer, which remains to be elucidated.