Abstract A067: Cellular cartography reveals transcriptional specificity and spatial organization of diverse luminal epithelial cells in the murine prostate

Abstract Introduction Prostate cancer (PCa) is the second most frequent malignancy in men. Genetically engineered PCa mouse models (GEMMs) do not faithfully recapitulate human PCa progression. Reasons include architectural differences between the multi-lobulated mouse prostate and the human organ, choice of gene promoter (such as probasin, Pbsn) used to regulate transgene expression in GEMMs and lobular differences in susceptibility to castration. Imaging studies showed that androgen deprivation (first line therapy for metastatic PCa) by castration leads to dramatic regression of ventral prostate (VP) by up to 70%. Hence delineating cell type equivalents between the human and mouse prostates and mapping their distribution across the distinct lobes will provide fundamental knowledge to improve GEMMs, to effectively model human PCa. Methods We performed single-cell RNA sequencing (scRNA-seq) of C57BL6 and FVB mice prostates (n=10) to delineate cell type composition. We also conducted sc multi-omics (10X Multiome gene expression+ ATAC) and spatial transcriptomics (10X Visium) of prostates from mice that were unperturbed or castrated (C57BL6) to study transcriptional module (TM) alterations and spatial gene expression among the luminal epithelial (LE) cell types upon castration. Results Analyses of scRNA-seq data from 9,439 cells identified 22 different cell types from epithelial, stromal, and immune compartments and includes 9 different LE cell types that are under-studied. The lack of a standard nomenclature describing murine prostate LE cells in previous scRNA-seq studies poses a challenge for integrative analysis. We resolved this by integrating 4 independent scRNA-seq studies with our data to arrive at unified nomenclature and simultaneously validate our findings by statistical analysis. Multi-omics data analysis revealed LE cells TM differences, suggesting that LE cell diversity is developmentally triggered. Spatial transcriptomics and matched RNA in situ hybridization captured the lobe specific distribution patterns of LE cell types. For e.g., Pbsn+ LE cells were predominantly found across the AP, dorsal and lateral prostate, while Spink1+LE cells containing stemness associated genes (e.g.Tacstd2) were enriched in the VP. Analysis of the castration model revealed susceptibility differences to androgen deprivation among LE populations. Multi-omics analysis also showed a reduction in both chromatin accessibility and transcription of androgen regulated genes upon castration. Finally, cell type enrichment analysis suggests LE cells of the mouse AP and VP as equivalents of human LE and putative cell lineage signatures were enriched in PCa profiles, possibly stratifying PCa patient population. Conclusion A comprehensive mouse prostate cell atlas was built from two mouse strains. We provide a practical reference for the transcriptional and spatial profiles of each epithelial population. LE cells from AP and VP were most sensitive to castration and best represent human LE and the cell type specific genes identified here can guide future GEMM development. Citation Format: Hanbyul Cho, Yuping Zhang, Jean Tien, Jie Luo, June E. Wilke, Saravana M. Dhanasekaran, Rahul Mannan, Lisha Wang, Fengyun Su, Rui Wang, Evan T. Keller, Xuhong Cao, Sethu Pitchaya, Arul M. Chinnaiyan. Cellular cartography reveals transcriptional specificity and spatial organization of diverse luminal epithelial cells in the murine prostate [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A067.