Spatially resolved single-cell analysis of cellular plasticity and mechanisms of drug resistance

Cellular heterogeneity adversely affects clinical stratification, treatment decisions, and development of therapeutic resistance in cancer. Heterogeneity manifests as variability in gene expression and scales with the number of unique cell types and/or the extent of phenotypic plasticity. Therefore, an incisive tool that effectively quantifies heterogeneity, robustly identifies rare cell populations, efficiently predicts cell state transitions, and preserves the associated phenotypic manifestations will provide key insights into the mechanisms of plasticity and development of drug resistance. To this end, we developed High-Throughput Single-cell analysis using single-molecule Fluorescence In Situ Hybridization (HITS-FISH) - a completely automated imaging-based tool that provides absolute quantification of gene expression (mature and immature transcripts that are coding or non-coding), while still preserving spatial and morphological information. Using a combination of HITS-FISH and single cell RNAseq, which provides a high-throughput readout of gene expression signatures, we find that multiple, potentially plastic cell states (genetic, epigenetic, and cell cycle) coexist within a seemingly homogeneous population of cancer cells from various tissues. HITS-FISH suggests that one of the major contributors of such heterogeneity is pervasive aneuploidy, which is accentuated during treatment of cancer cells with chemotherapeutic agents and subsequent development of resistance against such drugs. Currently, we are further characterizing these plastic cells via lineage tracing and single-cell analysis to identify pre-resistant cell states and drug-induced gene-expression reprogramming. Citation Format: Sethuramasundaram Pitchiaya, Jeremy D9silva, Nicole Lee, Sathiyapandi Narayanan, Xia Jiang, Saravana M. Dhanasekaran, Arul M. Chinnaiyan. Spatially resolved single-cell analysis of cellular plasticity and mechanisms of drug resistance [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 2836.