Abstract
Lung cancer is the most frequent cancer worldwide, in terms of incidence and mortality. Due to challenges in the diagnosis of the disease, the 5-year overall survival rate is only ~16%. Previous studies have suggested that malignant transformations originate from adult stem cells, and malignant lesions may therefore express stem-cell-associated markers. The purpose of the present study is to investigate the expression and clinical significance of the stem cell-associated markers Sal-like protein 4 (SALL4) and leucine-rich repeat-containing G-protein coupled receptor 5 (LGR5) in lung cancer, and to provide novel diagnostic markers and targets for the treatment of lung cancer. The expression of the stem cell-associated markers SALL4 and LGR5 was analyzed by immunohistochemistry performed on 135 human lung cancer tissue specimens and 10 non-cancer lung tissue specimens. The clinical significance of the expression of these markers and correlation between their expression and clinical parameters was also assessed. SALL4 expression was highly upregulated in lung cancer tissues, but was not present in non-cancerous lung tissues, and the sensitivity and specificity of SALL4 reached 88% and 100%, respectively. By contrast, LGR5 demonstrated 97% sensitivity, but the specificity was poor. Therefore, SALL4 may be an extremely useful diagnostic marker for lung cancer, but LGR5 is not as useful.