Summary Muscle-invasive bladder cancers (MIBCs) are biologically heterogeneous and have widely variable clinical outcomes and responses to conventional chemotherapy. We discovered 3 molecular subtypes of MIBC that resembled established molecular subtypes of breast cancer. Basal MIBCs shared biomarkers with basal breast cancers and were characterized by p63 activation, squamous differentiation, and more aggressive disease at presentation. Luminal MIBCs contained features of active PPARγ and estrogen receptor (ER) transcription and were enriched with activating FGFR3 mutations and potentially FGFR inhibitor sensitivity. p53-like MIBCs were consistently resistant to neoadjuvant MVAC chemotherapy, and all chemoresistant tumors adopted a p53-like phenotype after therapy. Our observations have important implications for prognostication, the future clinical development of targeted agents, and disease management with conventional chemotherapy.

Fibroblast growth factor receptors (FGFRs) are activated by mutation and overexpressed in bladder cancers (BCs), and FGFR inhibitors are currently being evaluated in clinical trials in BC patients. However, BC cells display marked heterogeneity in their responses to FGFR inhibitors, and the biological mechanisms underlying this heterogeneity are not well defined. Here we used a novel inhibitor of FGFRs 1–3 and RNAi to determine the effects of inhibiting FGFR1 or FGFR3 in a panel of human BC cell lines. We observed that FGFR1 was expressed in BC cells that also expressed the “mesenchymal” markers ZEB1 and vimentin, whereas FGFR3 expression was restricted to the E-cadherin- and p63-positive “epithelial” subset. Sensitivity to the growth-inhibitory effects of BGJ-398 was also restricted to the “epithelial” BC cells and it correlated directly with FGFR3 mRNA levels but not with the presence of activating FGFR3 mutations. In contrast, BGJ-398 did not strongly inhibit proliferation but did block invasion in the “mesenchymal” BC cells in vitro. Similarly, BGJ-398 did not inhibit primary tumor growth but blocked the production of circulating tumor cells (CTCs) and the formation of lymph node and distant metastases in mice bearing orthotopically implanted “mesenchymal” UM-UC3 cells. Together, our data demonstrate that FGFR1 and FGFR3 have largely non-overlapping roles in regulating invasion/metastasis and proliferation in distinct “mesenchymal” and “epithelial” subsets of human BC cells. The results suggest that the tumor EMT phenotype will be an important determinant of the biological effects of FGFR inhibitors in patients.

Overexpression of TGFb inducible early gene (TIEG1) mimics TGFb action and induces apoptosis. In this study, we found that TIEG1 was significantly up-regulated during apoptosis induced by homoharringtonine or velcade. Overexpression of TIEG1 could induce apoptosis in K562 cells and promote apoptosis induced by HHT or velcade. TIEG1-induced apoptosis was shown to involve Bax and Bim up-regulation, Bcl-2 and Bcl-XL down-regulation, release of cytochrome c from mitochondria into the cytosol, activation of caspase 3 and disruption of the mitochondrial membrane potential (DWm). We concluded that TIEG1 is a key regulator which induces and promotes apoptosis through the mitochondrial apoptotic pathway.

SNS-032 is a potent inhibitor of cyclin-dependent kinases (Cdk) 2, 7, and 9 that regulate the cell cycle and transcription. Our studies in indolent primary chronic lymphocytic leukemia cells showed that SNS-032 inhibited transcription, diminished the antiapoptotic protein Mcl-1, and induced apoptosis. The present study focuses on evaluating this compound in four proliferating mantle cell lymphoma lines (Jeko-1, Granta 519, Mino, and SP-53). Consistent with its action against Cdk9 and Cdk7, SNS-032 inhibited the phosphorylation of RNA pol II in all four lines and blocked RNA synthesis. The transcripts and protein levels of short-lived proteins decreased, including cyclin D1 and Mcl-1. Cell growth was inhibited in a concentration-dependent manner in all lines. Apoptosis was induced in JeKo-1, Mino, and SP-53 cells without disrupting cell cycle distribution. However, apoptosis was limited in Granta cells; rather, there was a significant reduction of clonogenic survival. Small interfering RNA was used to specifically knock down Mcl-1 and cyclin D1 in JeKo-1 and Granta cells. Knocking down Mcl-1 induced significant apoptosis in Jeko-1 cells but not Granta cells. Reducing cyclin D1, rather than Mcl-1, was associated with loss of clonogenic survival in Granta cells. Thus, these results indicated that mantle cell lymphoma cell lines have distinct mechanisms sustaining their survival, and the mechanism of action of SNS-032 is dependent on the biological context of an individual line.