Abstract 2837: Single-cell heterogeneity with transcriptional memory confers resistance to cancer therapy

Abstract

Abstract Targeted therapies for cancer are a promising class of drugs that inhibit the specific molecular alterations that underlie the uncontrolled proliferation seen in cancer. The primary shortcoming of targeted therapy is disease relapse, which is driven by a subpopulation of cells that are resistant to these drugs. This phenomenon is generally thought to be genetic in origin; however, our recent work on melanoma shows that nongenetic cellular plasticity may provide a mechanism of resistance to these therapies. Furthermore, we showed that through the addition of the drug itself, cells transition from this transient plasticity into a new, stably resistant cell state via cellular reprogramming, suggesting that the time an individual cell exists in a state is important for producing the divergent resistance phenotype. However, there are currently no methods available to quantify the timescale of these fluctuations for the whole transcriptome. Thus, broadly generalizing this concept of timescales for cellular plasticity, we developed a novel method for genome-wide quantification of the timescales of gene expression memory based on a modern version of the ingenious Luria-Delbrück fluctuation analysis. Specifically, we isolated individual cells, allowed them to expand, and then performed RNA sequencing on each of the samples. For genes with uniform expression, all the samples should have similar RNA sequencing counts; however, for genes that occasionally turn on in a subset of cells, the RNA sequencing counts across all samples should show high variance. In melanoma, this method revealed the gene expression state of rare cells resistant to targeted therapy. In a completely new model, triple-negative breast cancer, this method revealed a novel rare subpopulation of cells exhibiting resistance to chemotherapy. More generally, this method has the potential to reveal other new phenotypes associated with rare cell biology, including metastasis and the early stages of stem cell differentiation. Citation Format: Sydney Shaffer, Benjamin Emert, Arjun Raj. Single-cell heterogeneity with transcriptional memory confers resistance to cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2837.