Background: DNA topoisomerase II alpha (topo II alpha) is associated with active cell proliferation of mammalian cells. Topo II alpha overexpression has been reported in a number of human malignancies and is considered to be related to their biological behaviors.
Materials and methods: We examined the expression of topo II alpha immunohistochemically in 136 cases of human esophageal squamous cell carcinoma, 10 foci of squamous dysplasia and 10 non-pathologic squamous epithelium. We calculated the labeling index (LI) or the percentage of immunopositive cells for Topo II alpha and Ki67, and Topo II alpha LI/Ki67 LI (T/K ratio). These findings were then correlated with clinicopathological features of the patients including their clinical outcome.
Results: Both topo II alpha and Ki67 immunoreactivity were detected in the nuclei. A significant positive correlation was obtained between Topo II alpha and Ki67 LIs in all the specimens examined. Topo II alpha LI and T/K ratio were 24.5 +/- 8.0% and 1.04 +/- 0.64 for carcinoma, 19.1 +/- 15.2% and 0.68 +/- 0.29 for dysplasia and 14.0 +/- 14.1% and 0.55 +/- 0.17 for non-pathologic epithelium, respectively. Topo II alpha LI and T/K ratio in carcinoma cases were significantly higher than those of normal epithelium. Topo II alpha LI alone did not correlate with any of clinicopathological parameters examined but among carcinoma cases, cases with lymph nodes metastasis or higher histological stages had significantly higher T/K ratio than those without lymph node metastasis or lower histological stages. In addition, carcinoma cases with T/K ratio of greater than 0.8 demonstrated significantly worse prognosis than those with T/K ratio of smaller than 0.8.
Conclusions: The relative overexpression of topo II alpha as compared with Ki67, i.e., increased T/K ratio was detected in esophageal squamous cell carcinoma and is considered to represent a dysregulation or qualitative alteration in topo II alpha, possibly associated with malignances, as reported in other human cancers. In addition, topo II alpha overexpression may also be correlated with the aggressive biological behavior of the patients with esophageal squamous cell carcinoma.