Molecular profile of bladder cancer progression to clinically aggressive subtypes.

Bladder cancer is a histologically and clinically heterogenous disease. Most bladder cancers are urothelial carcinomas, which frequently develop distinct histological subtypes. Several urothelial carcinoma histological subtypes, such as micropapillary, plasmacytoid, small-cell carcinoma and sarcomatoid, show highly aggressive behaviour and pose unique challenges in diagnosis and treatment. Comprehensive genomic characterizations of the urothelial carcinoma subtypes have revealed that they probably arise from a precursor subset of conventional urothelial carcinomas that belong to different molecular subtypes - micropapillary and plasmacytoid subtypes develop along the luminal pathway, whereas small-cell and sarcomatoid subtypes evolve along the basal pathway. The subtypes exhibit distinct genomic alterations, but in most cases their biological properties seem to be primarily determined by specific gene expression profiles, including epithelial-mesenchymal transition, urothelial-to-neural lineage plasticity, and immune infiltration with distinct upregulation of immune regulatory genes. These breakthrough studies have transformed our view of bladder cancer histological subtype biology, generated new hypotheses for therapy and chemoresistance, and facilitated the discovery of new therapeutic targets.

Meta-Analysis of the Luminal and Basal Subtypes of Bladder Cancer and the Identification of Signature Immunohistochemical Markers for Clinical Use.

BACKGROUND: It has been suggested that bladder cancer can be divided into two molecular subtypes referred to as luminal and basal with distinct clinical behaviors and sensitivities to chemotherapy. We aimed to validate these subtypes in several clinical cohorts and identify signature immunohistochemical markers that would permit simple and cost-effective classification of the disease in primary care centers. METHODS: We analyzed genomic expression profiles of bladder cancer in three cohorts of fresh frozen tumor samples: MD Anderson (n=132), Lund (n=308), and The Cancer Genome Atlas (TCGA) (n=408) to validate the expression signatures of luminal and basal subtypes and relate them to clinical follow-up data. We also used an MD Anderson cohort of archival bladder tumor samples (n=89) and a parallel tissue microarray to identify immunohistochemical markers that permitted the molecular classification of bladder cancer. FINDINGS: Bladder cancers could be assigned to two candidate intrinsic molecular subtypes referred to here as luminal and basal in all of the datasets analyzed. Luminal tumors were characterized by the expression signature similar to the intermediate/superficial layers of normal urothelium. They showed the upregulation of PPARγ target genes and the enrichment for FGFR3, ELF3, CDKN1A, and TSC1 mutations. In addition, luminal tumors were characterized by the overexpression of E-Cadherin, HER2/3, Rab-25, and Src. Basal tumors showed the expression signature similar to the basal layer of normal urothelium. They showed the upregulation of p63 target genes, the enrichment for TP53 and RB1 mutations, and overexpression of CD49, Cyclin B1, and EGFR. Survival analyses showed that the muscle-invasive basal bladder cancers were more aggressive when compared to luminal cancers. The immunohistochemical expressions of only two markers, luminal (GATA3) and basal (KRT5/6), were sufficient to identify the molecular subtypes of bladder cancer with over 90% accuracy. INTERPRETATION: The molecular subtypes of bladder cancer have distinct clinical behaviors and sensitivities to chemotherapy, and a simple two-marker immunohistochemical classifier can be used for prognostic and therapeutic stratification. FUNDING: U.S. National Cancer Institute and National Institute of Health.

Endothelin-1 enhances the expression of the androgen receptor via activation of the c-myc pathway in prostate cancer cells.

Increasing evidence suggests that androgen independent prostate cancer (PC) maintains a functional androgen receptor (AR) pathway despite the low levels of circulating androgen following androgen withdrawal, the molecular mechanisms of which are not well defined yet. To address this question, we investigated the effects of endothelin-1 (ET-1) on AR expression. Western analysis and RT-PCR revealed that in the presence of ET-1, levels of AR significantly increased in a time- and dose-dependent manner in LNCaP cells. Pretreatments with inhibitors of Src and phosphoinositide kinase 3 (PI-3K) suppressed ET-1-induced AR expression. As ET-1 was reported to cause a transient increase in c-myc mRNA levels, we examined the involvement of c-myc in ET-1-mediated AR expression. Transient transfection of c-myc siRNA neutralized ET-1-induced AR expression, suggesting that AR induction by ET-1 is c-myc dependent. AR can regulate the transcription of its own gene via a mechanism in which c-myc plays a crucial role. Therefore, we assessed if ET-1-induced-c-myc leads to the enhancement of AR transcription. Reporter gene assays using the previously identified AR gene enhancer containing a c-myc binding site were conducted in LNCaP cells. We found that ET-1 induced reporter gene activity from the construct containing the wild-type but not mutant c-myc binding site. Chromatin immunoprecipitation assays confirmed that ET-1 increased interaction between c-myc and c-myc binding sites in AR enhancer, suggesting that ET-1-induced AR transcription occurs via c-myc-mediated AR transcription. Together, these data support the notion that ET-1, via Src/PI-3K signaling, augments c-myc expression leading to enhanced AR expression in PC.