PTGS2 and squamous cell carcinoma: Generally, constitutive activation of COX-2 has been demonstrated in various tumors of the lung, including atypical adenomatous hyperplasia [3], adenocarcinoma [4], squamous cell carcinoma [5] and bronchiolar alveolar carcinoma [6], and its over-expression has been associated with poor prognosis and short survival of lung cancer patients [7].