Inhibin/activin subunits beta-A (-βA) and beta-B (-βB) are differentially localised in normal, hyperplastic and malignant human endometrial tissue

Summary ns (INHs) are dimeric glycoproteins composed of an alpha (-α) subunit and one of two possible beta (β-) subunits (βA or βB). The aims of this study were to determine the frequency and distribution of INH beta (βA and βB) subunits in normal, hyperplastic and malignant human endometrium. Endometrial tissue was obtained from normal, hyperplastic (simple, complex and atypical) and endometrioid adenocarcinoma (EC) and INH-α, -βA and -βB were labelled using immunohistochemistry and immunofluorescence. INH-βA and -βB labelling was increased significantly between the proliferative and secretory phase ( p < 0.0 5 ). The lowest labelling was demonstrated in EC, being significantly lower than in secretory phase ( p < 0.0 1 ) and in simple, complex and atypical hyperplastic tissue ( p < 0.0 5 ). For inhibin-βB, the most intense labelling was noted in atypical hyperplasia compared to EC ( p < 0.0 5 ). A strong colocalisation of inhibin-α and -βA could be demonstrated in malignant endometrial tissue, suggesting the production of inhibin A within the tumour. Additionally, only limited colocalisation of inhibin-βB with -α subunit could be observed, suggesting the synthesis of activin B rather than inhibin B in malignant endometrium. In conclusion, INH-βA and -βB were labelled in normal, hyperplastic and malignant endometrium. Hyperplastic tissue labelled more intensely than EC for the presence of INH-βA and -βB, suggesting a substantial function in endometrial pathogenesis and an important role in endometrial carcinogenesis.