The CSC hypothesis posits that there is a subset of tumors cells driving tumor growth and metastasis and that by targeting this population, tumors can be more efficiently eradicated. Recently it was shown that there are two types of CSCs in breast cancer, mesenchymal CSC’s characterized as CD44+/CD24- and an epithelial type marked by ALDH expression. The cellular plasticity of these CSC states may contribute to their metastatic capacity. However, little is known about the heterogeneity of these CSC populations or how they are regulated by the tumor microenvironment. To address these issues we have utilized Drop-Seq to generate single cell RNA-Seq data from thousands of cells across patient derived xenografts from various molecular subtypes of breast cancer. In order to monitor real-time state transitions between the determined cellular populations, we have also designed and constructed fluorescent reporter constructs for genes specific to critical cell populations and cancer stem cells. We used CRISPR/Cas9 to introduce these reporters into the native loci of the genes in order to recapitulate native gene expression patterns. Single cell transcriptomics will help to characterize the molecular heterogeneity of CSC populations. The addition of fluorescent reporters will help to elucidate the mechanisms that regulate breast CSC’s as well as their interaction with the tumor microenvironment and to identify potential therapeutic targets.

Citation Format: Michael D. Brooks, Max S. Wicha. Dissecting heterogeneity and population dynamics in breast cancer stem cells [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 929. doi:10.1158/1538-7445.AM2017-929