Nuclear Localization of PTTG1 Promotes Migration and Invasion of Seminoma Tumor Through Activation of MMP-2.

Abstract Background: Seminoma is the most common subtype of testicular germ cell tumors (TGCTs) and its molecular patterns have not been fully clarified. The pituitary tumor-transforming gene 1 (PTTG1) is a securin, inhibitor of premature sister chromatid segregation during mitosis and is overexpressed in many cancers. PTTG1 shows the ability to sustain the invasiveness of several cancer types through its transcriptional activity. In the present study, we investigate the PTTG1 role on the invasive properties of seminoma.Methods: Three seminoma cell lines showing different proliferation rates and marker expression features were used as an in vitro model. Biochemical and immunofluorescence analyses were performed to evaluate PTTG1 levels and subcellular localization. Functional analyses, including wound healing, matrigel invasion assays and zymography were applied to study migratory and invasive capability of the cell lines. RNA interference studies and overexpression experiments were performed to address the PTTG1 role in seminoma cell lines invasiveness. Finally, the Atlas database was interrogated to study PTTG1 subcellular localization in seminoma and non-seminomas testicular tumors in order to analyze the PTTG1 and matrix metalloproteinase-2 (MMP-2) levels in these groups.Results: We found that PTTG1 was highly and differentially expressed in the seminoma cell lines. PTTG1 nuclear localization was positively correlated to the aggressive phenotype. Modulation of PTTG1 expression uncovered a direct causal link between PTTG1 and seminoma cell line invasiveness. Importantly, analysis of the human Atlas database revealed that PTTG1 was localized in the nucleus exclusively in seminoma compared with non-seminoma tumors and showed that MMP-2 levels was significant higher in seminomas.Conclusions: The results of the present research elucidate the role of nuclear PTTG1 in promoting invasiveness and metastatic process of seminoma cell lines. Analysis from the Atlas database strongly supported these results, revealing an exclusive PTTG1 nuclear localization and an increase of MMP-2 levels in seminoma versus non-seminoma tumors. Overall, these data lead to the hypothesis that nuclear PTTG1 is an eligible prognostic factor in seminomas.