Abstract 5075: Single-cell RNAseq of human prostate cancer-associated fibroblasts reveals distinct subpopulations that may promote inflammatory cell recruitment to the tumor microenvironment
Authors: Vickman Renee E. , Broman Meaghan M. , Atallah Nadia M. , Sudyanti Ayu , Franco Omar E. , Ratliff Timothy L. , Hayward Simon W. 
Published: August 2018

Abstract
Introduction: Carcinoma-associated fibroblasts (CAF) are a heterogeneous group of cells within the tumor microenvironment that can promote tumorigenesis in the prostate. The full extent of heterogeneity in CAF and its consequences are not understood. A more detailed description of the prostate tumor microenvironment could aid in overcoming major obstacles within the field, including defining indolent versus aggressive disease and uncovering novel therapeutic and disease-stabilizing pathways in a step toward personalized therapy.
Methods: These studies utilized Fluidgm's C1 Single-Cell Auto Prep System and library construction in preparation for single-cell (sc) RNAseq of human prostate CAF. Bioinformatics analysis was used to generate cell clusters. Further examination of the differentially expressed (DE) gene profiles for each cell cluster was performed to elucidate the function and means of communication among clusters and with other cells, particularly those within the immune/inflammatory network. Communication between CAF and immune cells was also analyzed by in vivo testing of tissue recombinants generated with CAF or normal fibroblasts. The resultant tumors were analyzed using FACS to assess the effects of the CAF on inflammatory cell recruitment.
Results: Principal component analysis and unsupervised cell clustering allows for visualization of at least three CAF subpopulations, each with distinct DE gene profiles. Further investigation into the DE genes for each cluster suggests these subpopulations have unique functions within the tumor microenvironment, including a role in immune/inflammatory cell recruitment. For example, one cluster expresses high levels of CCL11 and CXCL1, suggesting a role in the recruitment of neutrophils, myeloid cells, or other inflammatory cells, while a second cluster has decreased expression of chemokines but elevated expression of extracellular matrix-related genes such as COL1A1, MMP16, and FN1, suggesting an alternative, potentially structural, role for this CAF cluster. Previous analysis in vivo demonstrated that CAF drive tumorigenesis in a reporter epithelium. The speculated role of CAF in immune cell recruitment was supported by increased recruitment of myeloid cells, including macrophages and granulocytes, to prostate tissues in the presence of CAF compared to normal fibroblasts.
Conclusions: These studies demonstrate that CAF contain a limited number of distinct subpopulations of cells; the relatively small number of identified CAF clusters allows for feasible biologic study and mathematical modeling. Some CAF highly express extracellular mitotic and chemotactic signaling molecules that may be involved in the recruitment of inflammatory cells as well as direct growth regulation of the tumor by promoting an M2-dominant microenvironment.
Citation Format: Renee E. Vickman, Meaghan M. Broman, Nadia M. Atallah, Ayu Sudyanti, Omar E. Franco, Timothy L. Ratliff, Simon W. Hayward. Single-cell RNAseq of human prostate cancer-associated fibroblasts reveals distinct subpopulations that may promote inflammatory cell recruitment to the tumor microenvironment [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 5075.