Abstract IA13: Clonal dynamics of normal and malignant human mammary cell growth in xenografts

Most human breast cancers have diversified genomically and biologically by the time they become clinically evident and little is known about their origin from normal human mammary cells, or the cellular and molecular mechanisms that lead to their genesis and evolution. We have developed methods to quantify, purify and characterize different subsets of normal human mammary cells and have used these to identify properties that may influence their propensity for transformation. We have also developed methods for inducing the rapid transformation in vivo of these purified subsets following their transplantation into immunodeficient mice. The results demonstrate the ability of a single oncogene ( KRAS G12D ) to induce the formation of serially transplantable, polyclonal, invasive ductal carcinomas within 8 weeks of being introduced either subrenally or subcutaneously into immunodeficient mice. Both primary and secondary tumors are phenotypically heterogeneous and transcriptome analyses of primary tumors assign them to a “normal-like” category. DNA barcoding of the cells at the time of their initial transduction with KRAS G12D has revealed a dramatic change in the numbers and sizes of clones they generate after 2 weeks in vivo. DNA barcoding also showed the unexpected appearance of many “new” clones in tumors generated upon passage into secondary recipients, thus recapitulating some features of in vivo passaged human breast cancer cell lines and patients’ tumor xenografts. This system challenges previous concepts about the process of human mammary oncogenesis and provides a new system for analyzing factors that can influence its speed, efficiency and heterogeneity of outcomes. Citation Format: Connie J. Eaves, Long Nguyen, Davide Pellacani, Nagarajan Kannan, Sylvan Lefort, Sneha Balani, Claire Cox, Tomo Osako, Samuel Aparicio, Martin Hirst. Clonal dynamics of normal and malignant human mammary cell growth in xenografts. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr IA13.