Abstract
Little is known regarding the subclone evolution process in advanced bladder cancer, particularly with respect to the genomic alterations that lead to the development of metastatic lesions. In this project, we identify gene expression signatures associated with metastatic bladder cancer through mRNA expression profiling of RNA isolated from 33 primary bladder cancer and corresponding lymph node (LN) metastasis samples. Gene expression profiling (GEP) was performed on RNA isolated using the Illumina DASL platform. We identified the developmental transcription factor TCF21 as being significantly higher in primary bladder cancer compared with LN metastasis samples. To elucidate its function in bladder cancer, loss- and gain-of-function experiments were conducted in bladder cancer cell lines with high and low expression of TCF21, respectively. We also performed GEP in bladder cancer cell lines following TCF21 overexpression. We identified 2,390 genes differentially expressed in primary bladder cancer and corresponding LN metastasis pairs at an FDR cutoff of 0.1 and a fold change of 1. Among those significantly altered, expression of TCF21 was higher in the primary tumor compared with LN metastasis. We validated this finding with qPCR and IHC on patient samples. Moreover, TCF21 expression was higher in luminal cell lines and knockdown of TCF21 increased invasion, tumor cell dissemination, and metastasis. In contrast, overexpression of TCF21 in highly metastatic basal bladder cancer cell lines decreased their invasive and metastatic potential. IMPLICATIONS: TCF21 is differentially overexpressed in primary bladder cancer compared with matched LN metastasis, with in vitro and in vivo studies demonstrating a metastasis suppressor function of this transcription factor.
Highlights
Bladder cancer accounts for nearly 200,000 deaths worldwide and is a source of significant morbidity, with over 500,000 new cases diagnosed each year
We describe the results of our efforts to use gene expression profiling to identify differences between primary bladder cancer tissue and their corresponding metastatic lesions, based on mRNA expression profiling on matched lymph node (LN) tissue from human specimens
GSEA plots for significant Hallmark pathways (FDR q value < 0.01) for LN metastasis and primary bladder cancer are shown in Supplementary Figs
Summary
Bladder cancer accounts for nearly 200,000 deaths worldwide and is a source of significant morbidity, with over 500,000 new cases diagnosed each year. Of patients diagnosed with bladder cancer are diagnosed with urothelial carcinoma, a heterogenous epithelial malignancy with a high somatic mutation rate [4, 5]. Phylogenetic reconstructions have demonstrated that tumors can exhibit an evolutionary pattern of growth, with metastatic lesions demonstrating greater intratumoral heterogeneity than the primary tumor [11, 12]. This heterogeneity can confer challenges in personalizing therapy, and additional investigation into the genomic drivers of metastatic lesions in bladder cancer is required
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