INHIBIN ALPHA,BETA(A) SUBUNIT AND ACTIVIN TYPE-II RECEPTOR MESSENGER-RNAS ARE EXPRESSED IN HUMAN BRAIN-TUMORS

Inhibin and activin were initially isolated as regulators of pituitary or gonadal hormone and are now known to be growth factors belonging to the TGF-beta family with diverse influences on the differentiation and proliferation of various tissues. To investigate the rule of inhibin and activin in human brain tumors, the expression of inhibin alpha, and beta(A) mRNA as well as activin type II receptor (ACTR II) mRNA were studied in various human brain tumors. The tumors were divided into the following 4 groups: 3 Rathke's cleft cysts and 2 craniopharyngiomas (group 1), 8 meningiomas (group 2), 8 malignant gliomas (group 3), and various other tumors including 1 each of germinoma, astrocytoma, hemangioblastoma, and osteochondroma as well as 2 malignant lymphomas and 2 metastatic squamous cell carcinomas (group 4). Immediately after resection, tumor tissues were homogenized in guanidine thyiocyanate to extract total RNA. PCR was then performed with reverse-transcribed cDNA and the respective amplification primers. DNA bands were obtained by agarose gel electrophoresis. Messenger RNA for the inhibin beta(A) subunit was demonstrated in all of the tissues studied. In contrast, inhibin ct subunit mRNA was expressed in 60%, 50%, 75%, and 75% of the tumors in groups 1, 2, 3 and 4, respectively, whereas ACTR II mRNA was demonstrated in 20%, 37.5%, 62.5% and 50% of the tumors in each group. Coexpression of mRNAs for the inhibin alpha, and beta(A) subunits and ACTR II occurred in some brain tumors. The levels of inhibin alpha and ACTR II mRNA tended to be higher in the tumors with a higher grade of malignancy. These results indicate that some human brain tumors express receptors for activin, and that inhibin and activin may play an autocrine or paracrine role in brain tumor tissue.