Immunohistochemical detection of GLUT1, p63 and phosphorylated histone H1 in head and neck squamous intraepithelial neoplasia: evidence for aberrations in hypoxia‐related, cell cycle‐ and stem‐cell‐regulatory pathways

Abstract

Most epithelial malignancies are characterized by multistep progression from preinvasive/intraepithelial neoplasia to invasive malignancy. Detection and grading of early squamous intraepithelial neoplasia may at times be problematic. The aim of this study was to examine the ability of immunomarkers GLUT1, phospho-histone H1 and p63 to detect such early lesions. Sections of formalin-fixed paraffin-embedded tissue from 27 cases of squamous intraepithelial neoplasia, 26 associated with invasive carcinoma, were immunostained with anti-p63 (4A4; Santa Cruz), anti-GLUT1 (Chemicon) and anti-phospho-histone H1 (monoclonal 12D11) and compared with normal, hyperplastic and immature squamous metaplastic epithelium. Normal epithelium displayed phospho-histone H1 in scattered parabasal cells; p63 in the basal one-quarter to one-half of epithelium; and GLUT1 negativity or weak/equivocal mid-epithelial GLUT1+ foci. In hyperplasia phospho-histone H1+ cells were also limited to the parabasal layer; p63 positivity was essentially identical to that in normal epithelium; GLUT1 characteristically stained basal cells in rete-like areas. p63 staining in squamous intraepithelial neoplasia (grade 1) was indistinguishable from normal epithelial staining; in contrast, squamous intraepithelial neoplasia (grade 3) was readily apparent, with up to full-thickness p63 positivity. Squamous intraepithelial neoplasia (grade 1) was readily distinguishable from normal epithelium with both phospho-histone H1 and GLUT1 immunostaining; both markers were detected in cell layers above the parabasal layer. With both, progressively higher cell layers stained in proportion to the severity of the intraepithelial neoplasia, up to full thickness positivity in grade 3 squamous intraepithelial neoplasia. Squamous metaplasia and grade 3 squamous intraepithelial neoplasia were not distinguishable with p63 (both showed full-thickness staining) but were readily distinguishable with GLUT1 and phospho-histone H1 stains. GLUT1 appeared to be the most sensitive marker for all grades of intraepithelial neoplasia. Altered expression of all three markers was a common finding in squamous intraepithelial neoplasia, hence, dysregulation of cell cycle-promoting cyclin-dependent kinases (phospho-histone H1), altered stem cell regulatory pathways (p63) and enhancement of hypoxia-sensing pathways (GLUT1) are all early alterations in the progression of squamous malignancy of head and neck origin. A panel of all three may be a useful means of detecting squamous intraepithelial neoplasia.