Heterotypic mouse models of canine osteosarcoma recapitulate tumor heterogeneity and biological behavior

Purpose: The goals of this study were to establish in vivo models that recapitulated the heterogeneous behavior of osteosarcoma and to develop an approach to distinguish genes expressed from tumor cells apart from those expressed from host cells in next generation sequencing (NGS) data from xenograft tumors. Methods: We used cell lines derived from two spontaneous canine osteosarcoma tumors with distinctly different biological behaviors for heterotypic in vivo modeling. NGS was used to compare the transcriptome profiles of the xenograft tumors to the transcriptome profiles of the parental cell lines and to study the tumor microenvironment of the xenograft tumors. Sequenced reads were trimmed for adaptor sequence, and masked for low-complexity or low-quality sequence, then mapped to a HISAT2 index for mapping which was built from a multi-sequence fasta file containing both the canine (canFam3) and murine (mm10) genomes with the HISAT2 aligner (2.0.2-beta) using default parameters. Rsubread featureCounts (1.4.6) was used to estimate transcript abundance using default parameters. The Bioconductor package ‘edgeR’ (version 3.12.1) was used for differential gene expression analysis and Partek Genomic Suite (version 6.6) was used for clustering and visualization. Qiagen's Ingenuity Pathway Analysis application (version 01-04) and Thomson Reuter's MetaCore software suite were used for pathway and upstream regulator analysis with differentially expressed genes. Results: We document that orthotopic canine osteosarcoma xenografts preserve the biological, molecular, and heterotypic biology observed in the tumors from which they were derived. The data also provide insight into the tumor-host interactions and identify targets that could play a role in treatment strategies. Conclusions: Our study represents the first detailed analysis of xenograft transcriptomes with an approach that allows for accurate examination of tumor-intrinsic properties, as well as organotypic tumor-stromal interaction that may influence tumor progression. mRNA profiles of xenograft tumor from cell lines derived from two spontaneous canine osteosarcoma tumors with different biological behavior (OS-1 and OS-2) were generated by deep sequencing, in quarduplicate, using Illumina HiSeq 2500.