Henchy, C. | Search bioRxiv

bioRxiv2024

Gas1-Mediated Suppression of Hepatoblastoma Tumorigenesis

Background and AimsHepatoblastoma (HB), the most common pediatric liver cancer, often dysregulates the Wnt/{beta}-catenin, Hippo and NFE2L2/NRF2 pathways. Pairwise combinations of oncogenically active forms of the terminal transcription factor effectors of these pathways, namely {beta}-catenin (B), YAP (Y) and NRF2 (N) generate HBs in mice, with the triple combination (B+Y+N) being particularly potent. Each tumor group alters the expression of thousands of B-,Y- and N-driven unique and common target genes. Identifying those most responsible for transformation is thus an important question as it might reveal new mechanistic insights and therapeutic opportunities. Approach and ResultsTranscriptional profiling of >60 murine HBs driven by the above oncogenic combinations and different B mutants and in genetic backgrounds that impair tumor growth rates but not initiation has revealed a common set of 22 "BYN genes" that are similarly deregulated in all cases. Many are associated with multiple "Cancer Hallmarks" and their expression levels often correlate with survival in human HBs, hepatocellular carcinomas and other cancers. Among the most down-regulated of these is Gas1, which encodes a Glycosylphosphatidylinositol (GPI)-linked outer membrane protein. We show here that restoring Gas1 expression impairs B+Y+N-driven HB tumor growth in vivo and in HB-derived immortalized cell lines in vitro in a manner than requires membrane anchoring of the protein via its GPI moiety. ConclusionsOur findings implicate Gas1 as a proximal mediator of HB pathogenesis and validate the BYN gene set as one deserving of closer additional scrutiny in future studies.

cancer biology↗

bioRxiv2024

Efficient Derivation of Immortalized, Isogenic Cell Lines from Genetically Defined Murine Hepatoblastomas

Background & AimsMolecularly, hepatoblastoma (HB), the most common childhood liver cancer, is the simplest of all human neoplasms, with the vast majority deregulating the Wnt/{beta}-catenin, Hippo and/or NFE2/NRF2 signaling pathways. Murine HBs can be generated by over-expressing any pairwise or triple combination of mutant forms of these pathways terminal effectors, namely {beta}-catenin (B), YAP (Y) and NFE2L2/NRF (N). Each molecular subtypes displays distinct features resembling those of human HBs. However, research has been hampered by a paucity of established cell lines of any species. MethodsWe show here that immortalized cell lines can be routinely established from murine HBs that over-express B+Y and B+Y+N. This is facilitated by the concurrent in vivo, Crispr-mediated inactivation of the Cdkn2a tumor suppressor locus. ResultsEight BY and 3 BYN cell lines have been generated and characterized and are available to the HB research community. Ten of these lines can be regrown as subcutaneous and metastatic lung tumors in the immuno-competent mice from which they originated while retaining their original histologic features. During maintenance as spheroids in vitro, or during in vivo propagation, tumor cells express endothelial cell markers, particularly in regions that are hypoxic and/or in proximity to incipient blood vessels. ConclusionsThe ability to generate isogenic HB cell lines with defined oncogenic drivers should facilitate studies that are best performed in vitro. The approach may also be useful for deriving HB cell lines associated with less common molecular drivers and from human tumors. SynopsisThe derivation of multiple immortalized murine hepatoblastoma cell lines driven by defined oncogenes is described. These lines are isogenic, retain their tumorigenicity in immuno-competent mice, readily form spheroids and express endothelial markers in response to hypoxia. They will allow studies that have heretofore been difficult or impossible to perform in vivo.

cancer biology↗