Expression of the preproenkephalin A gene in tumor cells and brain glioma: a northern and in situ hybridization study.

Preproenkephalin A (PPA) mRNA expression was studied by Northern blot and in situ hybridization in cell lines (rat glioma C6, rat hepatoma HTC, human neuroblastoma IMR32, mouse neuroblastoma NS20Y, rat fibroblast FR3T3, human bladder carcinoma EJ, human vulva carcinoma A431, myelocytic leukemia HL60, rat adrenal carcinoma Y1) and in brain tumours (implanted C6 cells). C6 glioma in cell culture, as well as in brain tumours, expressed high levels of PPA mRNA as compared to the caudate nucleus of the rat brain. EJ and FR3T3 cell lines also expressed the PPA mRNA, which was not detectable in A431, Y1, NS20Y, IMR32, HTC, HL60 cell lines as well as in the rat liver. This observation provides an interesting model to study the mechanisms by which the malignant transformation can induce in glial cells the derepression of a gene which is usually expressed in neurons or in neuron-like cells.