Abstract 3992: Modes of metastasis evolution in human and murine cancer revealed by whole exome sequencing

Abstract

Abstract Despite that fact that 90% of cancer deaths are due to metastasis, relatively little is known about how metastases evolve from primary cancers. We subjected 101 trios consisting of primary tumor, brain metastasis, and normal reference tissue to whole exome sequencing (WES). To analyze the data, we developed novel computational tools to derive high quality allelic copy-number profiles directly from the WES data. These were used to perform an integrative analysis of somatic copy-number alterations (SCNAs) and somatic single nucleotide variants (SSNVs). This analysis allowed us to estimate the clonal architecture of the primary and metastatic samples from each patient, and to reconstruct a single phylogenetic tree relating all of the subclones detected in both samples. We determined that all of the matched metastases analyzed likely formed from a single clone. In all cases, we observed a sibling relationship between the metastasis and primary tumor samples, indicating that they share a common ancestor, but ongoing evolution in the primary tumor resulted in fully clonal mutations in the primary biopsy that were not present in the metastasis sample. An important corollary of this is that in no case was a metastasis-founding subclone detected in a primary tumor sample. Using mutational spectra associated with tobacco exposure in lung cancers, we determined that most of the evolution leading up to the brain metastasis like occurred within the lung. In contrast with these findings, analysis of related primary tumor and metastasis families in a mouse model of small cell lung cancer using identical methodology revealed evidence of more variable patterns of metastatic spread. Analysis of draining lymph nodes revealed that multiple subclones of the primary contributed to these metastases. In addition, we uncovered evidence for the sequential spread of metastases, consistent with multiregion sequencing of primary and metastatic human pancreatic cancer. The extension of this finding to a mouse cancer model suggests this may be a more frequent feature of cancer metastasis, and raises the possibility of genetically dissecting these processes in this experimental system. Citation Format: Scott L. Carter, Priscilla K. Brastianos, David G. McFadden, Thales Papagiannakopoulos, Amaro Taylor-Weiner, Kristian Cibulskis, Tyler Jacks, William Hahn, Gad Getz. Modes of metastasis evolution in human and murine cancer revealed by whole exome sequencing. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3992. doi:10.1158/1538-7445.AM2014-3992