New insights into diagnosis and therapeutic options for proliferative hepatoblastoma.

Surgery and cisplatin-based treatment of hepatoblastoma (HB) currently guarantee the survival of 70%-80% of patients. However, some important challenges remain in diagnosing high-risk tumors and identifying relevant targetable pathways offering new therapeutic avenues. Previously, two molecular subclasses of HB tumors have been described, C1 and C2, with C2 being the subgroup with the poorest prognosis, a more advanced tumor stage, and the worst overall survival rate. An associated 16-gene signature to discriminate the two tumoral subgroups was proposed, but it has not been transferred into clinical routine. To address these issues, we performed RNA sequencing of 25 tumors and matched normal liver samples from patients. The transcript profiling separated HB into three distinct subgroups named C1, C2A, and C2B, identifiable by a concise four-gene signature: hydroxysteroid 17-beta dehydrogenase 6, integrin alpha 6, topoisomerase 2-alpha, and vimentin, with topoisomerase 2-alpha being characteristic for the proliferative C2A tumors. Differential expression of these genes was confirmed by quantitative RT-PCR on an expanded cohort and by immunohistochemistry. We also revealed significant overexpression of genes involved in the Fanconi anemia (FA) pathway in the C2A subgroup. We then investigated the ability of several described FA inhibitors to block growth of HB cells in vitro and in vivo. We demonstrated that bortezomib, a Food and Drug Administration-approved proteasome inhibitor, strongly impairs the proliferation and survival of HB cell lines in vitro, blocks FA pathway-associated double-strand DNA repair, and significantly impedes HB growth in vivo. CONCLUSION: The highly proliferating C2A subtype is characterized by topoisomerase 2-alpha gene up-regulation and FA pathway activation, and the HB therapeutic arsenal could include bortezomib for the treatment of patients with the most aggressive tumors. (Hepatology 2018;68:89-102).

Adaptation of the secretory pathway in cancer through IRE1 signaling.

The unfolded protein response (UPR) was originally identified as a signaling network coordinating adaptive and apoptotic responses to accumulation of unfolded proteins in the endoplasmic reticulum (ER). More recent work has shown that UPR signaling can be triggered by a multitude of cellular events and that the UPR plays a critical role in the prevention of cell transformation but also in tumor development. This has been particularly well illustrated with studies on one of the three major ER stress sensors, IRE1. This ER resident type I transmembrane protein senses luminal ER stress and transduce signals through its cytosolic RNase activity. IRE1 signaling has been shown to contribute to the progression of solid tumors through pro-angiogenic mechanisms. Herein, we expose the methodologies for investigating IRE1 signaling in tumor cells and in tumors. Moreover, we show that selective pharmacological inhibition of IRE1 RNase activity sensitizes tumor cells to ER stress.