Abstract 157: Single-cell DNA sequencing identifies a late dissemination model in metastatic colorectal cancer

Abstract

Abstract Metastatic colorectal cancer (mCRC) is a devastating disease with only 11% 5-year survival rate for stage IV patients. The genomic basis of metastasis has been difficult to study, in part due to the extensive intratumor heterogeneity at both the primary and metastatic tumor sites. Previous studies have applied bulk next-generation sequencing (NGS) methods, which have limited ability to resolve intratumor heterogeneity. To address this problem, we developed a highly-multiplexed single cell DNA sequencing method that combines flow-sorting of single nuclei, multiple-displacement-amplification, low-input library preparation, library barcoding, targeted capture and NGS to generate high-coverage data from single tumor cells. To increase throughput, we performed targeted single-cell DNA sequencing using a panel of 201-cancer genes to analyze single cells from primary tumors and liver metastases from two mCRC patients. In each patient, we sequenced 90 single tumor cells from the primary and metastatic tumor, to delineate the clonal architecture of the tumor and reconstruct their phylogenetic lineages. In addition, we sequenced populations of tumor cells at high coverage depth (200X). Our data identified a large number of nonsynonymous mutations that evolved in the root nodes during the earliest stages of primary tumor evolution and were maintained in all single cells during the clonal expansion of the tumor mass. We also identified a small number of mutations that were specific to the liver metastases, which are likely to play an important role in metastatic dissemination. Using the single cell data, we constructed phylogenetic trees, which revealed branched evolution at both organ sites. Collectively, our data suggest that both mCRC patients are consistent with a late-dissemination model, in which the primary tumors evolved for a long period of time prior to the dissemination of clones to distant organ sites. This model has important clinical implications, by suggesting that surgical intervention or therapeutic treatment of the primary CRC tumor can prevent metastasis, since single tumor cells do not disseminate at the earliest stages of tumor growth Citation Format: Marco L. Leung, Anna Casasent, Yong Wang, Emi Sei, Nicholas Navin. Single-cell DNA sequencing identifies a late dissemination model in metastatic colorectal cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 157.