Presentation Authors: John P Sfakianos, Harry Anastos, Jorge Daza*, Geoffrey Bryant, Rohan Bareja, Olivier Elemento, Bishoy Faltas, Ketan Badani, Matthew D Galsky, David J Mulholland, New York, NY
Introduction: Tumor heterogeneity occurs in most cancer types including those of urothelial in origin. Despite this, studies have increasingly applied gene expression signatures to classify bladder cancers into distinct mRNA subtypes. Such tumor stratification assumes that each tumor has a predominant signature that is sufficient to predict progression kinetics, patient survival and response to therapy. We hypothesize that such distinct classification does not consider the marked intra-tumor heterogeneity that can occur in primary and metastatic disease and the impact that disease progression may have on the equilibrium of lineage composition.
Methods: We developed a mouse model of muscle invasive bladder cancer capable of orthotopic transplant. This was achieved using OHBBN induced carcinogenesis in mice with global GFP and luciferase expression Tg(CAG-luc-eGFP) (Fig. 1). Implants of sorted GFP+ cancer cells to the muscle wall of naive FVB/NJ mice allows for the distinction of tumor cells from host cells (stromal, immune). Using defined surface antigens (CD49f, Epcam, CD44, CD24) to isolate defined lineage populations, we conducted in vivo implants to determine the potential for lineage plasticity and redistribution during bladder cancer progression. Single cell and bulk RNA sequencing analysis was used to assess the coinciding expression of multiple clinical subtypes in a single primary OHBBN bladder tumor.
Results: We demonstrated that: (1) OHBBN Tg(CAG-luc-eGFP) mouse bladder tumors contain lineage-defining mRNA expression subtypes identifiable in human bladder cancers including basal, luminal, p53-like, EMT & claudin and neuroendocrine. (2) Identified surface antigens that discriminate clinical mRNA subtypes in mouse tumors. (3) Identified clinically defined lineages within a single mouse bladder tumor capable of tumor initiation, lineage plasticity and redistribution to other lineage subtypes during progression and therapy.
Conclusions: While clinical reports have argued that the use of a single mRNA subtype can be assigned to human bladder muscle invasive bladder cancers, our modeling argues that multiple subtypes exist and that these populations or clusters of cancer cells are dynamic both during progression and therapy. These data also have implications towards acquired resistance in clinical disease.