Oncogenic Role of ADAM32 in Hepatoblastoma: A Potential Molecular Target for Therapy

SIMPLE SUMMARY: Hepatoblastoma (HBL) is a rare hepatic malignancy occurring mainly in early childhood. Although recently developed treatment regimens have improved prognosis, many refractory cases still exist, and the anticancer drug cis-diamminedichloroplatinum—cisplatin—primarily used in HBL treatment often induces severe side effects. Therefore, more effective and safer therapies are needed. In this study, we demonstrate that the expression level of ADAM32 is particularly high in HBL tissue samples and is associated with poor prognosis in various cancer types through the regulation of cancer cell proliferation, stemness, migration, invasion, and acquired resistance to chemotherapy. Our results thus indicate that ADAM32 could be a promising candidate therapeutic target molecule, and provide new insights into the molecular mechanisms of HBL carcinogenesis. ABSTRACT: Outcomes of pediatric hepatoblastoma (HBL) have improved, but refractory cases still occur. More effective and safer drugs are needed that are based on molecular mechanisms. A disintegrin and metalloproteases (ADAMs) are expressed with high frequency in various human carcinomas and play an important role in cancer progression. In this study, we analyzed expression of ADAMs in HBL with a cDNA microarray dataset and found that the expression level of ADAM32 is particularly high. To investigate the role of ADAM32 in cancer, forced expression or knockdown experiments were conducted with HepG2 and HBL primary cells. Colony formation, cell migration and invasion, and cell viability were increased in HepG2 expressing ADAM32, whereas knockdown of ADAM32 induced a decrease in these cellular functions. Quantitative RT-PCR demonstrated an association between ADAM32 expression and the expression of genes related to cancer stem cells and epithelial–mesenchymal transition (EMT), suggesting a role of ADAM32 in cancer stemness and EMT. Furthermore, knockdown of ADAM32 increased cisplatin-induced apoptosis, and this effect was attenuated by a caspase-8 inhibitor, suggesting that ADAM32 plays a role in extrinsic apoptosis signaling. We conclude that ADAM32 plays a crucial role in progression of HBL, so it might be a promising molecular target in anticancer therapy.