CDH12 and the development of the neuronal subtype in MIBC.

Abstract

e16579 Background: We discovered a novel cell epithelial cell population we termed “C3” in muscle-invasive bladder cancer (MIBC) that is negatively prognostic for surgery and chemotherapy. This cell population shares similarities with the neuronal subtype MIBC (NEBC) which has limited treatment options and is driven by unclear molecular mechanisms. The objective of the study was to determine if NEBC is driven by some of the genes that are overexpressed in C3 cells. A top overexpressed and C3 cell specific gene that is also enriched in normal neuronal tissue is Cadherin 12 (N-Cadherin 2, CDH12). Hence, we initiated a study of this gene. Methods: We overexpressed CDH12 in two murine MIBC cell lines (NA13 and MB49) and then inoculated them into mice. Tumor growth kinetics were studied, and single-nucleus RNA sequencing (snRNA-seq) and bulk RNA sequencing were then used to evaluate the tumors. Tissue samples from patients with MIBC were also analyzed using snRNA-seq and Co-detection by Indexing (CODEX) multiplexed immunofluorescence, and our bioinformatics analysis combined transcriptomic profiles from > 2000 MIBC samples from published datasets, to characterize the transcriptional programs induced by enforcing CDH12 expression. Results:Enforced expression of CDH12 led to enhanced tumor growth and the appearance of the neuroendocrine tumor phenotype. NEBC from human samples showed the highest expression of CDH12, and snRNA-seq results showed that NEBC also has the highest proportion of CDH12 epithelial cells and demonstrated co-expression of CDH12 and neuronal markers (NCAM1, CHGA, and SYP). RNA velocity analysis in murine and human tumors implicated CDH12 as a driver for the development of the neuronal subtype. Conclusions: To our knowledge, this study provides the first identification of a genetic driver leading to NEBC and implicates a novel gene, CDH12 in this process.