Characterization of Apelin/APJ Axis Expression in Normal Testicular Tissue, Germ Cell Neoplasia in Situ, and Testicular Seminoma

Abstract

Aim: A testicular germ cell tumour is not observed widely, but its incidence and mortality rates have increased in recent years. One of the most common forms of this tumour is seminoma. Germ cell neoplasia in situ (GCNIS) is the precursor of seminoma. The apelin/APJ axis is increased in many cancers and is a pathway that plays an active role in angiogenesis, lymphangiogenesis, tumour growth, and migration. This study investigated the cellular distributions of apelin and APJ protein expressions in normal testicular tissue (TT), GCNIS, and seminoma.Material and Methods: Tissues from 18 patients who had undergone orchiectomy were used in this study. These tissues include areas of normal TT, GCNIS, and seminoma. Immunolocalisation of apelin and APJ were identified through the immunohistochemical method.Results: Apelin expression was significantly increased in seminoma and GCNIS compared to normal. Apelin expression were the same in GCNIS and seminoma. APJ expression was significantly increased in seminoma compared to normal and GCNIS. Normal and GCNIS APJ expressions were similar.Conclusion: Expressions of apelin and APJ proteins were significantly increased in seminoma in our study. Our findings were consistent with the results of relevant studies as increased expression of apelin/APJ has been observed in many different cancers. It can be predicted that the increase of this pathway in seminoma may support angiogenesis, lymphangiogenesis, migration, and metastasis. Therefore, the increase in mortality rates in seminoma patients may be related to apelin/APJ axis. Ultimately, the use of inhibitors of this pathway in these patients may reduce their mortality rate. New studies are needed before these inhibitors can be used clinically.