c-MET proto-oncogene in malignant testicular germ cell tumours

THE THESIS EXPLAINED The biological issue: Testicular Germ Cell Tumours (TGCTs), seminomas and non-seminomas, represent the most frequent malignancy in Caucasian males (20–40 years). Even if diagnosed in an early stage, resulting in good prognosis, a small percentage of cases progress resulting in death in young men. 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 seminomas and non-seminomas is due to the combination of genetic, epigenetic and microenvironment-based alterations (genvironment). Hepatocyte Growth Factor (HGF) is available in the testicular microenvironment, together with its receptor c-MET, from early embryonic development to adult stage. Moreover, 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, that are Type II GCT representative cell lines, and the effect of c-MET activation/repression in the regulation of cancer biological processes. Moreover, we evaluated the immunoreactivity of c-MET in a cohort of patients affected by TGCTs with the aim to correlate in vitro study with clinical information. Results: Our results demonstrate that TCam-2 (seminoma cell line) and NT2D1 (embryonal carcinoma cell line) show multiple copies of c-MET gene, whereas NCCIT (mixed seminoma/non-seminoma cell line) show a normal gene copy number. They differentially express c-MET receptor, but they do not secrete HGF. Moreover, we found that NT2D1 cells, which have the higher availability of the protein, increase their proliferation, polarized migration and invasion in response to HGF administration. NCCIT respond to HGF stimulation only partially, whereas TCam-2 cells do not respond to HGF at least for the investigated parameters. Moreover, preliminary data show that HGF stimulation is able to modulate, in NT2D1 cells, the expression of several miRNAs, probably involved in cancer progression, but these results need further investigations. Interestingly, the immunohistochemical study of c-MET distribution pattern in TGCT histological samples confirm its presence both in seminoma and non-seminoma lesions with different scores. Noteworthy, we found a higher c-MET immunoreactivity in non-seminoma tumours, in particular in all the most differentiated cancer specimens. Conclusions: On the basis of the results herein reported, this study could shed light on the molecular pathways underlying TGCT onset and progression, and opens new fields of research on the use of c-MET receptor as a potential biomarker for testicular germ cell tumours, since this protein is differentially expressed and distributed in TGCT different histotypes. Moreover, a deeper investigation of HGF/c-MET system in this pathology could allow better prediction of clinical outcome and/or identification of patients at low/high risk of progression.