ID4 and lung adenocarcinoma: Furthermore, ID4 was significantly down-regulated in lung adenocarcinoma in the Okayama [26], Beer [22], Landi [24], Su [23], Garber [28], Stearman [29] and Hou [27] datasets, and also in squamous cell lung carcinoma (Garber [28] and Hou [27] datasets).