High expression of heme oxygenase-1 is associated with tumor invasiveness and poor clinical outcome in non-small cell lung cancer patients

Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, is known to play a role in the protection of cells against oxidative stress, inflammation, anomalous proliferation and apoptosis. As yet, the role of HO-1 expression in non-small cell lung cancer (NSCLC) development and metastasis remains unclear and insufficient data are available regarding its impact on the prognosis of NSCLC patients. Seventy NSCLC patients who underwent surgical resection were included in this HO-1 expression study and, concomitantly, clinical parameters were collected. Two lung adenocarcinoma cell lines (A549 and H441) were used to assess both invasive and migratory parameters in vitro. NSCLC patients with a high HO-1 expression ratio (tumor tissue/normal tissue) (> 1) exhibited a significantly poorer prognosis and a higher metastatic rate compared to those with a low HO-1 expression ratio (p < 0.05). The invasive and migratory abilities of A549 and H441 cells significantly increased after exogenous HO-1 over-expression and significantly decreased after siRNA-mediated HO-1 expression silencing. HO-1 up- and down-regulation also positively correlated with the expression of metastasis-associated proteins EGFR, CD147 and MMP-9. In addition, we found that HO-1 expression can be inhibited by PI3K and AKT inhibitors, but not by MAPK inhibitors. HO-1 is a poor prognostic NSCLC predictor and its over-expression may increase the metastatic potential of NSCLC. Based on our findings and those of others, HO-1 may be considered as a novel NSCLC therapeutic target.