Syngeneic model of carcinogen-induced tumor mimics basal/squamous, stromal-rich, and neuroendocrine molecular and immunological features of muscle-invasive bladder cancer

Abstract

IntroductionBladder cancer is a heterogenous disease and the emerging knowledge on molecular classification of bladder tumors may impact treatment decisions based on molecular subtype. Pre-clinical models representing each subtype are needed to test novel therapies. Carcinogen-induced bladder cancer models represent heterogeneous, immune-competent, pre-clinical testing options with many features found in the human disease.MethodsInvasive bladder tumors were induced in C57BL/6 mice when continuously exposed to N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) in the drinking water. Tumors were excised and serially passed by subcutaneous implantation into sex-matched syngeneic C57BL/6 hosts. Eight lines were named BBN-induced Urothelium Roswell Park (BURP) tumor lines. BURP lines were characterized by applying consensus molecular classification to RNA expression, histopathology, and immune profiles by CIBERSORT. Two lines were further characterized for cisplatin response.ResultsEight BURP tumor lines were established with 3 male and 3 female BURP tumor lines, having the basal/squamous (BaSq) molecular phenotype and morphology. BURP-16SR was established from a male mouse and has a stromal-rich (SR) molecular phenotype and a sarcomatoid carcinoma morphology. BURP-19NE was established from a male mouse and has a neuroendocrine (NE)-like molecular phenotype and poorly differentiated morphology. The established BURP tumor lines have unique immune profiles with fewer immune infiltrates compared to their originating BBN-induced tumors. The immune profiles of the BURP tumor lines capture some of the features observed in the molecular classifications of human bladder cancer. BURP-16SR growth was inhibited by cisplatin treatment, while BURP-24BaSq did not respond to cisplatin.DiscussionThe BURP lines represent several molecular classifications, including basal/squamous, stroma-rich, and NE-like. The stroma-rich (BURP-16SR) and NE-like (BURP-19NE) represent unique immunocompetent models that can be used to test novel treatments in these less common bladder cancer subtypes. Six basal/squamous tumor lines were established from both male and female mice. Overall, the BURP tumor lines have less heterogeneity than the carcinogen-induced tumors and can be used to evaluate treatment response without the confounding mixed response often observed in heterogeneous tumors. Additionally, basal/squamous tumor lines were established and maintained in both male and female mice, thereby allowing these tumor lines to be used to compare differential treatment responses between sexes.

A combinatorial genetic strategy for exploring complex genotype–phenotype associations in cancer

“…We further confirmed the relevance of our FHBT models by projecting their RNA expression patterns onto principle component analysis plots of tumors from the TCGA-BLCA cohort (Fig. 2i ) and established N -butyl- N -(4-hydroxybutyl)-nitrosamine (BBN)-induced mouse bladder cancer models 15 (Extended Data Fig. 7b ) to show that they occupy overlapping space on the basis of histologic classification, indicating that the transcriptional features with the greatest variance between tumor subtypes are also conserved with FHBT models.…”

Preclinical models for bladder cancer therapy research

“…Histopathologic and molecular characterization showed that the eight established tumour lines represented basal/squamous (BaSq), stromal-rich (SR) and neuroendocrine (NE)-like molecular subtypes. As reported for human tumours, cisplatin exhibited antineoplastic effects in a SR tumour line, while a BaSq line was found to be resistant [39 ▪ ]. To assess the effects of the histone deacetylase (HDAC) inhibitor chidamide on BC, Wang et al generated orthotopic models by instillation of N-methyl-N-nitrosourea (MNU) in the bladders of female Sprague–Dawley rats.…”