The pattern of expression of the 5T4 oncofoetal antigen on normal, dysplastic and malignant oral mucosa

The human 5T4 oncofoetal antigen is expressed by all types of trophoblast in pregnancy but is not detected on most adult tissues, although low levels are found on some epithelia. However, this antigen is strongly expressed by many cancers and tumour-associated labelling correlates with metastatic spread and poor clinical outcome for patients with gastric and colon cancer. Overexpression of the gene influences cell adhesion, shape and motility, which may be related to changes in the cellular localisation of the 5T4 oncofoetal antigen as malignancy develops. To establish whether the 5T4 oncofoetal antigen can serve as a tumour-specific marker for oral cancer and precancer, we have evaluated the pattern of expression on biopsies of normal, inflamed and dysplastic oral mucosa using immunohistochemistry. Oral mucosa, taken from different sites in the mouth. expressed the 5T4 oncofoetal antigen with varying intensity and pattern. The majority of the immunoreactivity was detected in the basal and suprabasal layers, with expression extending into the spinous cells at fully keratinised sites and when inflammation was present. This antigen was also detected in the underlying connective tissue. Oral squamous cell carcinoma showed a variety of patterns and intensity of staining corresponding to those found for normal mucosa. However, 21 of 41 cases showed no stromal labelling, a finding also observed for dysplastic lesions. The alterations in the pattern and intensity of 5T4 oncofoetal antigen expression were not related to clinicopathological features of the tumours examined. These data show that the 5T4 oncofoetal antigen is expressed on normal oral mucosa, such that this target cannot be used for detection of neoplastic or preneoplastic cells, although altered expression may contribute to the pathogenesis of these lesions, (C) 2001 Elsevier Science Ltd. All rights reserved.