Apoptosis in epithelial hyperplastic laryngeal lesions

The Fas receptor appears to be commonly expressed in all morphological types of epithelial laryngeal hyperplasia (HP). Fas-mediated apoptotic cell death would thus be a possible phenomenon in these lesions. We observed more anti-apoptotic bcl-2 protein in epithelia with simple HP compared to the more advanced types of HP. It is suggested that in simple HP there is not yet a need for an early selection for cell death. The observed overexpression of metallothionein (MT) in the basal layers of simple HP would also support such a theory. These basal cells are dividing, non-apoptotic cells, which have not yet been selected for death. All 20 cysteine residues in MT are involved in metal binding, interfering with the intracellular redox balance, and thereby possibly inhibiting certain apoptotic signals. MIB-1 positivity was found only in the atypical HP, CIS, and invasive carcinomas. Intuition suggests that high labelling would be associated with poor prognosis. The degree of apoptosis, evaluated by TUNEL, did not show any differences between different types of epithelia. Although TUNEL is sensitive and rather specific, we emphasise that all TUNEL positive cells have apoptotic type morphology, confirming good and appropriate use of the technique.