Carbonic anhydrase IX expression is associated with tumor progression and a poor prognosis of lung adenocarcinoma

Carbonic anhydrase (CA) IX catalyzes the hydration of carbon dioxide into carbonic acid and participates in a variety of physiological and biological processes. The aim of this study was to evaluate the prognostic significance of CA IX expression in patients with lung adenocarcinoma. Standard immunohistochemical techniques were used to study CA IX expression in 134 patients who underwent curative resection for adenocarcinoma of the lung at our hospital between January 1995 and December 1996. We evaluated the correlations between CA IX expression levels on cancer cells and clinicopathological factors. CA IX expression was not observed in normal lung tissue or specimens from non-invasive adenocarcinomas. CA IX immunostaining was detected in 33 (24.6%) invasive adenocarcinoma cases. Poor differentiated histological phenotype (p=0.0015), pathological stage (p=0.0400), vascular invasion (p=0.0009) and lymphatic permeation (p=0.0050) were significantly related to CA IX expression. On univariate analysis, CA IX positive cases showed significantly shorter overall survival (p=0.0083) and disease-free survival (p=0.0122). In particular, the overall and disease-free survivals in stages I+II were significantly shorter in the CA IX positive than in the CA IX negative cases (p=0.0269 and 0.0011, respectively). Our results suggest that CA IX expression is strongly associated with tumor progression and indicates a poor prognosis for patients with stages I+II lung adenocarcinoma.