Abstract 3030: Mutant p53-driven metastasis explored utilizing a traceable, conditional osteosarcoma model

Abstract

Abstract TP53 is the most frequently mutated gene in cancer and missense mutations in particular account for the majority of mutations. Mutant p53 proteins exert oncogenic Gain-of-Function (GOF) properties that contribute to increased migration and invasion in culture and metastasis in vivo. To elucidate how mutant p53 drives metastasis, we developed a traceable somatic osteosarcoma model that initiates with a single p53 mutation (p53R172H or p53R245W), or p53 loss specifically in osteoblasts using Osx-cre. To mark tumor cells, we utilized the mTmG allele which expresses membrane-targeted Tomato (mT) prior to Cre-mediated excision and membrane-targeted green fluorescent protein (mG) after excision so the tumor cells become GFP+ and the stromal cells remain RFP+. In this high penetrant, short latency mouse model, tumor micro-metastasis can be detected by GFP expression in the context of a normal stroma and immune system. The cohort has developed osteosarcoma with complete penetrance and an average survival of 304± 65 day. We observed metastasis in 55% of p53 mutant osteosarcomas which was significantly higher than 26% metastasis observed in p53 null tumors (p<0.01). In p53 mutant osteosarcomas, the metastasis rate was found significantly associated with low p53 copy number. Spectral karyotyping (SKY) on early passage cells derived from somatic p53 mutant tumors exhibited marked aneuploidy with modal chromosome numbers near tetraploid. To characterize the transcriptional profile associated with mutant p53 GOF, we analyzed and compared the RNA-Seq transcriptomes of eight tumors derived from p53R172H mutant mice with eight p53 null tumors. Comparative analysis of gene expression identified a signature of snRNA genes to be strongly associated with mutant p53 gain of function. Functional annotation of upregulated genes in mutant tumors was also highly enriched for chromatin modifying enzymes. These findings contribute to our understanding of the role of mutant p53 GOF in metastasis. Our long term goal is to study how tumor-stromal interactions affect tumor development and metastasis. This understanding will have broad translational significance in diagnosis and treatment of tumors with mutant p53. Citation Format: Rasoul Pourebrahimabadi, Yun Zhang, Mark J. McArthur, Guillermina Lozano. Mutant p53-driven metastasis explored utilizing a traceable, conditional osteosarcoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3030. doi:10.1158/1538-7445.AM2017-3030