Loss of RanBP9 cooperates with p53 deficiency to promote sarcomagenesis

Methods

Bulk RNA sequencing was performed on livers from Ranbp9 knockout mice to identify dysregulated pathways. Mixed Ranbp9 and Trp53 deficient mice were bred to assess in vivo tumorigenesis. Tumors were characterized by histology and Ki-67 staining.

Western blotting was performed to assess protein expression. Functional assays in mixed RanBP9/p53 mouse embryonic fibroblasts (MEFs) were performed to evaluate proliferation and survival properties. Genomic alterations of CTLH subunits were evaluated in sarcoma patients using TCGA-SARC dataset.

Results: Loss of RanBP9 promoted an upregulation of proliferative signaling pathways, including MAPK/ERK, NOTCH, and JUN. Biallelic deletion of RanBP9 did not induce tumor development. In contrast, mice with combined heterozygous loss of Ranbp9 and Trp53 (R9/p53DHet) exhibited earlier tumor onset and increased soft tissue sarcoma development.

Histopathological analysis revealed increased mitotic activity, and Ki-67 confirmed elevated proliferative phenotype in R9/p53DHet sarcomas. Functional assays demonstrated increased proliferative capacity of R9/p53DHet MEF. Finally, TCGA-SARC dataset analysis showed that heterozygous loss of RanBP9 is frequent in sarcoma tumors.

Low mRNA expression of CTLH complex subunits, MKLN1 and RMND5B, was significantly associated with poor patient survival. Discussion: Loss of RanBP9 results in deregulation of signaling cascades that promote tumor growth and development. Our findings reveal a novel cooperative role between RanBP9 and p53 in repressing sarcoma development.

This mouse model provides a valuable platform to further study pathways regulated by the CTLH complex in sarcoma biology.