CDKN1A and squamous cell carcinoma: Additional human microarray studies that assessed lung tissue from smokers [44], and tumor tissue from patients with AC and squamous cell carcinoma, another NSCLC, identified other unique genes [41,42,45] such as Cdkn1a, cyclin-dependent kinase inhibitor 1A (P21), up in BALBLps-d (Table 1).