EXPRESSION OF THE AROMATIC L-AMINO-ACID DECARBOXYLASE MESSENGER-RNA IN HUMAN TUMOR-CELL LINES OF NEUROENDOCRINE AND NEUROECTODERMAL ORIGIN

Neuroendocrine differentiation of lung tumours is characterised by the expression of several neuroendocrine markers and is confined mostly t o specific histological subtypes, i.e. small cell carcinomas and carci noids. One of the markers seen in neuroendocrine tumours, high activit y of the aromatic L-amino acid decarboxylase (AADC), is helpful in dis tinguishing the classic and variant small cell lung tumour subtypes. H ere, we have analysed the expression and quantified the level of mRNA coding for AADC in human tumour cell lines by use of the reverse trans cription and polymerase chain reaction (RT-PCR). High amounts of mRNA were detected in classic small cell lung carcinomas and a neuroblastom a cell line. Other cell lines (melanomas, non-small cell lung carcinom as and osteosarcoma) also showed AADC expression, but the levels were 2-3 orders lower. Also, the tissue-specific (neuronal versus Liver-spe cific) mRNA type has been estimated. Small cell lung carcinomas, neuro blastoma and melanoma expressed messenger RNA specific for neuronal ti ssues. Importantly, the non-small cell lung carcinoma cell Lines expre ssed either liver-specific (non-neuronal) mRNA (cell line A549) or pre dominantly the neuronal (cell line NCI-H520) AADC message. These data indicate that a range of tumour cell lines transcribe the AADC gene an d that two distinct types of AADC mRNA which reflect the embryonal (ne uronal or non-neuronal) origin of the tumour may be produced in non-sm all cell lung cancer cells. (C) 1997 Elsevier Science Ltd.