Quantitative assessment of expression of cell adhesion molecule (CD44) splice variants: CD44 standard (CD44s) and v5, v6 isoforms in oral leukoplakias: An immunohistochemical study

Abstract

The aim of this study was to semiquantitatively analyze the immunohistochemical expression pattern of CD44 standard (CD44s) and variant (CD44v) isoforms in leukoplakias using a panel of monoclonal antibodies recognizing epitopes of CD44s and of the variant exons v5 and v6. To evaluate the efficacy of CD44s and CD44 v5, v6 immunoexpression as possible molecular markers in detecting high-risk leukoplakias when screening for this oral precancer. Samples of oral leukoplakia (40 cases) and of normal mucosa (10 cases) were evaluated. Oral leukoplakia was graded into: hyperkeratosis without dysplastic change (8 cases), mild dysplasia (13 cases), moderate dysplasia (10 cases), and severe dysplasias (9 cases). Expression of CD44s,v5, v6 was analyzed by immunohistochemistry in a semiquantitative manner. Three areas of epithelium were scored B, S, and C, i.e., stratum basale, stratum corneum, and stratum spinosum, respectively in leukoplakias. Scoring of all specimens followed a two-parameter system, which implemented percentage of positive cells and staining intensities. Statistical analyses for each parameter of all groups and normals, mean, and standard deviation were calculated by using computer software package EPISTAT. In normal epithelium CD44s, CD44v5, and CD44v6 were expressed as membranous proteins localized on the surface of epithelial cells. Both basal and spinous layer of epithelia expressed strong positive staining of CD44s, v5, v6 which then gradually faded into the negative staining of the superficial keratin layer. Profile of CD44s and v5 revealed that the mean levels of stratum B, S, and C in normal cases were comparable to the study cases and by Student 't' test P>0.05 not significant. There was, however, a statistically significant decrease in the expression of v6 with increasing grades of dysplasias when compared with normal mucosa. Among CD44s and its variant isoforms,v5, v6, in this study, variant isoform v6 may serve as a marker in detecting high-risk leukoplakias.