Abstract
Germ cell development is influenced by activin and inhibin, which are produced by Sertoli cells. Activin also affects differentiation of mouse embryonal carcinoma cells, which, to a certain extent, resemble the embryonal carcinoma component of germ cell tumours. Therefore, the expression of inhibin/activin subunits, of activin receptors and of the activin-binding protein follistatin was studied in testicular germ cell tumours, using RNAase protection assays. Testicular germ cell tumours of adolescents and adults (TGCTs) and spermatocytic seminomas expressed activin type I and type II receptors (ActRI and ActRII respectively). Seminomas expressed significantly lower levels of ActRIIA (P<0.05, Mann-Whitney U-test) and higher levels of ActRIA (P<0.05) and ActRIB (P<0.05) compared with non-seminomas. All tumours expressed inhibin beta-subunit transcripts, which are a prerequisite for activin synthesis. Non-seminomas contained significantly higher levels of the inhibin betaA subunit (P<0.001) compared with seminomas. No activin betaC subunit transcripts could be demonstrated by RNAase protection. Inhibin alpha-subunit expression was absent in the spermatocytic seminomas, in six out of nine seminomas and in 10 out of 11 non-seminomas. Follistatin was expressed predominantly in non-seminomas and spermatocytic seminomas. This expression of activin type I and type II receptors in combination with expression of inhibin beta-subunits indicates that activin may act as a para- or autocrine factor in the regulation of growth and differentiation of tumours of human germ cells.
Highlights
We demonstrated the expression of activin type I and type II receptors, in combination with inhibin PA and,B subunits and follistatin mRNAs
The non-seminoma group consisted of one pure embryonal carcinoma (EC), two yolk sac tumours (YS), one mature teratoma (MT), one immature teratoma (IT), three tumours with two components and three mixed tumours consisting of EC/IT/MT/YS plus trophoblastic giant cells in combination with a seminoma component
The expression of mRNAs coding for activin type IA and IB and for activin receptors type IIA and IIB was demonstrated by reverse transcriptase- polymerase chain reaction (RT-PCR) on RNA isolated from two seminomas and two non-seminomas as described under Materials and methods
Summary
Human testicular tumour material, collected during operation at the collaborating hospitals, was divided into two representative portions. One of these portions was snap frozen in liquid nitrogen, while the other portion was fixed in 4% buffered formalin and embedded in paraffin. The non-seminoma group consisted of one pure embryonal carcinoma (EC), two yolk sac tumours (YS), one mature teratoma (MT), one immature teratoma (IT), three tumours with two components (one EC/YS and two MT/YS) and three mixed tumours consisting of EC/IT/MT/YS plus trophoblastic giant cells in combination with a seminoma component. Normal testis RNA was isolated from tissue provided by the Dr Daniel den Hoed Cancer Center or was obtained commercially from ClonTech (Palo Alto, CA, USA)
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