EXPRESSION OF PITUITARY ADENYLATE-CYCLASE ACTIVATING POLYPEPTIDE AND RECEPTORS IN HUMAN BRAIN-TUMORS

The capacity of brain tumor samples to synthesize pituitary adenylate cyclase activating polypeptide (PACAP) was evaluated by the reverse tr anscriptase-polymerase chain reaction technique (RT-PCR). The expressi on of PACAP receptors was assessed by a combination of RT-PCR techniqu es, conventional binding techniques, and also by the ability of PACAP to stimulate adenylate cyclase activity. A weak PACAP mRNA and PACAP r eceptor mRNA expression was detected in only 3 of 16 meningiomas. A we ak PACAP stimulated adenylate cyclase activity (+20%) was detected in 10 of the 16 samples but binding of labeled PACAP was never observed. In the 16 gliomas studied (including two oligodendrogliomas and two ep endymomas), PACAP mRNA was identified in 13 samples and PACAP receptor mRNA in 15 samples. PACAP receptors were identified in all the sample s by binding studies and/or by PACAP stimulation of the adenylate cycl ase activity. PACAP mRNA was never detected in pituitary adenomas (thr ee prolactinomas, two mixed PRL-GH-producing tumors, three OH-secretin g tumors, three gonadotrophinomas, one ACTH-producing tumor, two nonse creting tumors) whereas PACAP receptor mRNA was highly expressed in al l the tumors except prolactinomas, where it was at the limit of detect ion, confirming the binding and adenylate cyclase activation results. Thus, it is unlikely that the neuropeptide PACAP could influence menin gioma's cell growth; PACAP secreted from extratumoral areas may influe nce pituitary tumors and PACAP could participate to gliomas developmen t.