Type II testicular germ cell tumors (TGCTs) represent the most frequent malignancy in Caucasian males (20–40 years). Even if diagnosed with disseminated disease, >80% of patients are cured; however, a small percentage of cases progress and result in death. It is commonly accepted that these cancers arise from a disturbed testicular embryonic niche that leads to the block of gonocyte differentiation. The subsequent development of the invasive seminomas and non-seminomas is due to a combination of genetic, epigenetic and microenvironment-based alterations (genvironment). Hepatocyte growth factor (HGF) is present in the testicular microenvironment, together with its receptor c-MET, from early embryonic development to an adult stage. In addition, c-MET is a well-known proto-oncogene involved in the onset and progression of various human cancers. Herein, we have investigated the expression and availability of HGF and c-MET in TCam-2, NCCIT and NT2D1 cells, which are type II (T)GCT representative cell lines, and the effect of c-MET activation/repression on the regulation of cancerous biological processes. We found that NT2D1 cells increase their proliferation, polarized migration, and invasion in response to HGF administration. NCCIT cells respond to HGF stimulation only partially, whereas TCam-2 cells do not respond to HGF, at least according to the investigated parameters. Interestingly, the immunohistochemical study of c-MET distribution in TGCTs confirm its presence in both seminoma and non-seminoma lesions with different patterns. Notably, we found the highest c-MET immunoreactivity in the epithelial elements of the various components of TGCTs: teratoma, yolk sac tumor and choriocarcinoma.

The study of how mechanical forces may influence cell behavior via cytoskeleton remodeling is a relevant challenge of nowadays that may allow us to define the relationship between mechanics and biochemistry and to address the larger problem of biological complexity. An increasing amount of literature data reported that microgravity condition alters cell architecture as a consequence of cytoskeleton structure modifications. Herein, we are reporting the morphological, cytoskeletal, and behavioral modifications due to the exposition of a seminoma cell line (TCam-2) to simulated microgravity. Even if no differences in cell proliferation and apoptosis were observed after 24 hours of exposure to simulated microgravity, scanning electron microscopy (SEM) analysis revealed that the change of gravity vector significantly affects TCam-2 cell surface morphological appearance. Consistent with this observation, we found that microtubule orientation is altered by microgravity. Moreover, the confocal analysis of actin microfilaments revealed an increase in the cell width induced by the low gravitational force. Microtubules and microfilaments have been related to autophagy modulation and, interestingly, we found a significant autophagic induction in TCam-2 cells exposed to simulated microgravity. This observation is of relevant interest because it shows, for the first time, TCam-2 cell autophagy as a biological response induced by a mechanical stimulus instead of a biochemical one.

c-MET pathway over-activation is the signature of malignancy acquisition or chemotherapy resistance of many cancers. We recently demonstrated that type II Testicular Germ Cell Tumours (TGCTs) express c-MET receptor. In particular, we elucidated that the non-seminoma lesions express c-MET protein at higher level, compared with the seminoma ones. In line with this observation, NTERA-2 clone D1 (NT2D1) non-seminoma cells increase their proliferation, migration and invasion in response to Hepatocyte Growth Factor (HGF). One of the well-known adaptor-proteins belonging to c-MET signaling cascade is c-Src. Activation of c-Src is related to the increase of aggressiveness of many cancers. For this reason, we focused on the role of c-Src in c-MET-triggered and HGF-dependent NT2D1 cell activities. In the present paper, we have elucidated that this adaptor-protein is involved in HGF-dependent NT2D1 cell proliferation, migration and invasion, since Src inhibitor-1 administration abrogates these responses. Despite these biological evidences western blot analyses have not revealed the increase of c-Src activation because of HGF administration. However, notably, immunofluorescence analyses revealed that cytoplasmic and membrane-associated localization of c-Src shifted to the nuclear compartment after HGF stimulation. These results shed new light in the modality of HGF-dependent c-Src recruitment, and put the basis for novel investigations on the relationship between c-Src, and TGCT aggressiveness.

Testicular vasculogenesis is one of the key processes regulating male gonad morphogenesis. The knowledge of the molecular cues underlining this phenomenon is one of today’s most challenging issues and could represent a major contribution toward a better understanding of the onset of testicular morphogenetic disorders. R-spondin 1 has been clearly established as a candidate for mammalian ovary determination. Conversely, very little information is available on the expression and role of R-spondin 1 during testicular morphogenesis. This study aims to clarify the distribution pattern of R-spondin 1 and other partners of its machinery during the entire period of testicular morphogenesis and to indicate the role of this system in testicular development. Our whole mount immunofluorescence results clearly demonstrate that R-spondin 1 is always detectable in the testicular coelomic partition, where testicular vasculature is organized, while Dickkopf-1 is never detectable in this area. Moreover, organ culture experiments of embryonic male UGRs demonstrated that Dickkopf-1 acted as an inhibitor of testis vasculature formation. Consistent with this observation, real-time PCR analyses demonstrated that DKK1 is able to slightly but significantly decrease the expression level of the endothelial marker Pecam1. The latter experiments allowed us to observe that DKK1 administration also perturbs the expression level of the Pdgf-b chain, which is consistent with some authors’ observations relating this factor with prenatal testicular patterning and angiogenesis. Interestingly, the DKK1 induced inhibition of testicular angiogenesis was rescued by the co-administration of R-spondin 1. In addition, R-spondin 1 alone was sufficient to enhance, in culture, testicular angiogenesis.

The direct impact of microgravity exposure on male germ cells, as well as on their malignant counterparts, has not been largely studied. In previous works, we reported our findings on a cell line derived from a human seminoma lesion (TCam-2 cell line) showing that acute exposure to simulated microgravity altered microtubule orientation, induced autophagy, and modified cell metabolism stimulating ROS production. Moreover, we demonstrated that the antioxidant administration prevented both TCam-2 microgravity-induced microtubule disorientation and autophagy induction. Herein, expanding previous investigations, we report that simulated microgravity exposure for 24 h induced the appearance, at an ultrastructural level, of cell-to-cell junctional contacts that were not detectable in cells grown at 1 g. In line with this result, pan-cadherin immunofluorescence analyzed by confocal microscopy, revealed the clustering of this marker at the plasma membrane level on microgravity exposed TCam-2 cells. The upregulation of cadherin was confirmed by Western blot analyses. Furthermore, we demonstrated that the microgravity-induced ROS increase was responsible for the distribution of cadherin nearby the plasma membrane, together with beta-catenin since the administration of antioxidants prevented this microgravity-dependent phenomenon. These results shed new light on the microgravity-induced modifications of the cell adhesive behavior and highlight the role of ROS as microgravity activated signal molecules.