Evaluation of ABCB5 immunostained epithelial stem cells in oral squamous cell carcinoma, inflammatory gingival hyperplasia and normal mucosa.

Oral cancer is the most prevalent head and neck cancer. Although tumor markers have been investigated for detecting the progression and prognosis of oral cancer, no reliable marker has been identified. We investigated the expression of ATP binding cassette subfamily B member 5 (ABCB5) positive stem cells in oral squamous cell carcinoma (OSCC) and in inflammatory gingival hyperplasia. We used tissue samples from normal subjects, patients with inflammatory gingival hyperplasia, and patients with OSCC. Samples were investigated using anti-ABCB5 monoclonal antibody immunohistochemistry to detect epithelial stem cells. Staining density, intensity, and immunoreactive scores of ABCB5 were analyzed for the three study groups. We found ABCB5 immunostaining in all three study groups, but different distributions of ABCB5 expression in different layers of the epithelium. We found no significant difference in staining intensity between inflammatory hyperplasia and normal mucosa, but we found significantly stronger expression in OSCC compared to normal and inflammatory hyperplasia individually. Elevated expression of ABCB5 in OSCC suggests an increased subpopulation of tumor cells with an undifferentiated stem cell phenotype, which facilitates cancer initiation and progression.