Abstract
NOTCH receptor signaling plays a pivotal role in liver homeostasis and hepatocarcinogenesis. However, the role of NOTCH pathway mutations and the NOTCH target gene HES5 in liver tumorigenesis are poorly understood. Here we performed whole-exome sequencing of 54 human HCC specimens and compared the prevalence of NOTCH pathway component mutations with the TCGA-LIHC cohort (N = 364). In addition, we functionally characterized the NOTCH target HES5 and the patient-derived HES5-R31G mutation in vitro and in an orthotopic mouse model applying different oncogenic backgrounds, to dissect the role of HES5 in different tumor subgroups in vivo. We identified nonsynonymous mutations in 14 immediate NOTCH pathway genes affecting 24.1% and 16.8% of HCC patients in the two independent cohorts, respectively. Among these, the HES5-R31G mutation was predicted in silico to have high biological relevance. Functional analyses in cell culture showed that HES5 reduced cell migration and clonogenicity. Further analyses revealed that the patient-derived HES5-R31G mutant protein was non-functional due to loss of DNA binding and greatly reduced nuclear localization. Furthermore, HES5 exhibited a negative feedback loop by directly inhibiting the NOTCH target HES1 and downregulated the pro-proliferative MYC targets ODC1 and LDHA. Interestingly, HES5 inhibited MYC-dependent hepatocarcinogenesis, whereas it promoted AKT-dependent liver tumor formation and stem cell features in a murine model. Thus, NOTCH pathway component mutations are commonly observed in HCC. Furthermore, the NOTCH target gene HES5 has both pro- and anti-tumorigenic functions in liver cancer proposing a driver gene dependency and it promotes tumorigenesis with its interaction partner AKT.
Highlights
In recent years, large next-generation sequencing projects sought to identify functionally important mutations, which may allow for the development of targeted drugs
Multiple mutations in the NOTCH pathway but rare copy number alterations were observed in the TCGA-LIHC cohort (Fig. 1b, Supplementary Fig. S1B, and Supplementary Table S4)
Previous studies focused on the overexpression of hyperactive NOTCH intracellular domain (NICD) in selected mouse models; albeit the role of downstream signaling transcription factors is still elusive
Summary
Large next-generation sequencing projects sought to identify functionally important mutations, which may allow for the development of targeted drugs. These studies revealed cancer driver mutations, disease subtyping, tumor heterogeneity, downstream functional associations, and targeted precision therapies [1, 2]. In multiple tumor entities, including hepatocellular carcinoma (HCC), which is the most frequent form of liver cancer, only few genes are recurrently mutated [3,4,5]. In The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) HCC data set (N = 364), only six genes were found to be significantly mutated in >5% of patients, namely TP53, CTNNB1, ALB, AXIN1, ARID1A, and APOB [3]. As mutations of different genes within the same pathway may result in the same outcome, combining multiple genes of one pathway is a powerful approach to identify significantly altered pathways [4, 5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
