A Novel Mouse-Human Xenograft Model of Osteogenesis

Objectives: Determine the cellular origin of ossification in CUHN015 and the identity of the inducing molecule(s).

Methods: RNA sequencing (RNA-seq) data from CUHN015 and CUHN022 (a non-bone forming xenograft) at passage four was subjected to a bioinformatics pipeline to define human and mouse transcripts. Secondary classification of transcripts based on association with intramembranous ossification was then performed. Xenografts of CUHN015 and CUHN022 were also propagated in the presence or absence of the fibroblast growth factor receptor inhibitor, AZD4547, and histologic analysis of tumors performed.

Results: RNA-seq revealed genes associated with ossification only upregulated in mouse reads, indicating that mouse stroma was attracted to the tumor and subsequently ossified. Notably, FGF3 expression was dramatically upregulated in human reads, with a concomitant increase in murine Fgfr2 expression. Repeating xenograft studies with CUHN015 in the presence or absence of AZD4547 illustrated that antagonizing FGFR signaling resulted in decreased expression of osteogenic markers in tumors and decreased abundance of mouse cells within the tumor.

Conclusions: CUHN015 promotes the formation of bone-containing tumors in part through FGFR signaling, which both attracts mouse cells to the human tumor and subsequently drives their ossification. These novel findings provide a novel model system that may unveil strategies to stimulate intramembranous ossification when treating bone disorders of the face and skull.