IBCN 2017: Novel Targets

Lisbon, Portugal (UroToday.com) Michèle J. Hoffmann from Heinrich-Heine-University, Duesseldorf, Germany presented her abstract ‘Combined pharmacological inhibition of BRD proteins and class-I HDACs synergistically induces apoptosis in urothelial carcinoma cells’. Combination of HDACi with JQ1, an inhibitor of bromodomain-containing acetylation reader proteins like BRD4 has shown efficacy in some cancers. They found JQ1 on its own induced cell cycle arrest and limited apoptosis in UCCs with strongly varying IC50 values. Comparable effects were achieved by siRNA-mediated knockdown of BRD4. Combined treatment with Romidepsin and JQ1 synergistically decreased viability, suppressed clonogenic growth of all UCCs and induced pronounced caspase-dependent apoptosis. At synergistic concentrations, toxicity in benign control cells was low. Concurrently, active Caspase 3 and PARP1 cleavage were increased, anti-apoptotic and oncogenic factors Survivin, BCL-2, BCL-XL, c-MYC, EZH2 and SKP2 were consistently downregulated. AKT phosphorylation was diminished, which may contribute to dramatic accumulation of cell cycle inhibitor p57KIP2. However, Cas9-mediated CDKN1C/p57KIP2 knockout did not rescue UC cells from apoptosis. In summary, despite its individual toxicity, FDA-approved Romidepsin could be applied in combination with JQ1 at relatively low, less toxic doses to treat urothelial carcinoma.

Alberto Contreras-Sanz from Vancouver Prostate Centre, Vancouver, BC, Canada presented his abstract ‘A Mouse Model of Bladder-Specific Over-Expression of NOTCH2 Confirms the Oncogenic Role of NOTCH2 in Bladder Cancer’. They have previously shown that NOTCH2 is an oncogene that drives bladder cancer (BCa) progression, and that this is particularly relevant in basal tumors. They tested whether NOTCH2 can promote BCa development in vivo via the establishment of a constitutively active NOTCH2 intracellular domain (N2ICD) mouse model. Luciferase activity indicating tumor growth was observed in the bladder of some mice 28 weeks into the experiment: 2 cases in the empty vector control group (2/15, 13.3%), 6 cases in the Upk2 group (6/15, 40%), and 5 cases in Krt5 group (5/15, 33.3%). The tumors in both Upk2 and Krt5 group showed not only urothelial, but also squamous cell carcinoma features. In the zebrafish model, metastasis was increased in the N2ICD over-expressed group compared to the wild-type cell lines. These results suggest that over-expression of wild-type N2ICD in the bladder wall could accelerate tumor development and possibly lead to more malignant phenotypes.

Armine K. Smith from Johns Hopkins, Baltimore, MD presented her abstract ‘Dysregulation of Estrogen Receptor Β Pathway as a Mechanism of Bacillus Calmette-Guérin (BCG) Resistance in Bladder Cancer’. They established cell lines resistant to direct and indirect effects of BCG by exposing mouse (MB49) and human (UMUC3) bladder cancer cells to BCG both in vitro and in vivo in mouse models. BCG treatment resulted in increased levels of cleaved caspases 3, 8 and 9 in all groups, whereas in the BCG-resistant line there were more cleaved caspase 9 and less cleaved caspase 8 production. There were notable differences in the expression of CREB, AKT 1/2/3, cJUN, Src and ERK1/2 proteins, all of which are known to be involved in the estrogen receptor-β (ERβ) signaling pathways. Tamoxifen significantly enhanced the effect of BCG in BCG-resistant, but not BCG-naïve cell lines, both in vitro and in vivo. In summary, dysregulation of ERβ signaling is a potential contributor to BCG resistance.

Speaker(s): Michèle J. Hoffmann, Heinrich-Heine-University, Duesseldorf, Germany; Alberto Contreras-Sanz, Vancouver Prostate Centre, Vancouver, BC, Canada; Armine K. Smith, Johns Hopkins, Baltimore, MD

Written by: Stephen B. Williams, M.D., Associate Professor, Division of Urology, The University of Texas Medical Branch, Galveston, TX. and Ashish M. Kamat, M.D. Professor, Department of Urology, Division of Surgery, The University of Texas MD Anderson Cancer Center, Houston, TX., at the International Bladder Cancer Network - October 21, 2017- Lisbon, Portugal