Stem-cell states converge in multi-stage cutaneous squamous cell carcinoma development [scRNA-seq]
Stem cells play a critical role in cancer development by contributing to cell heterogeneity, lineage plasticity, and drug resistance. We created gene expression networks from hundreds of mouse normal and tumor samples, and integrated these with lineage tracing and single-cell RNA-seq, to identify convergence of cell states in pre-malignant tumor cells expressing markers of lineage plasticity and drug resistance. Two of these cell states representing multilineage plasticity or proliferation were inversely correlated, suggesting a mutually exclusive relationship. Treatment of carcinomas in vivo with chemotherapy repressed the proliferative state and activated multilineage plasticity, while inhibition of differentiation repressed plasticity and potentiated responses to cell-cycle inhibitors. Manipulation of this cell state transition point may provide a rich source of potential combinatorial targets for cancer therapy.  These scRNAseq data encompass normal skin, papilloma, and squamous cell cacinoma samples. Overall design: To investigate cell state identities of individual cells in mouse squamous cell carcinomas as they grow from normal skin, to papilloma, to carcinoma, and are then treated with cisplatin.  These cancers were initiated with DMBA and promoted with TPA.  Several samples were lineage traced using Lgr6-EGFP-CreERT2 mice carrying the Rosa26-LSL-Tomato reporter (Lgr6eGFPtdTomato) lineage tracing system to track Lgr6+ cells (GRF+) and their progeny (tomato).