EAU 2018: 4N1K-peptide Derived From Thrombospondins Acts as a Tumour Suppressor in Bladder Cancer in Vivo And in Vitro: Potential Therapeutic Agents for Intra-vesical Therapy

Copenhagen, Denmark (UroToday.com) There has long been an effort to identify an effective salvage therapy for NMIBC patients who fail intravesical BCG. Unfortunately, at this time, radical cystectomy remains the best option for these patients. Many agents have been tested and failed to demonstrate significant benefit. However, many newer agents, including immunotherapy agents, are currently in clinical trial. The advantages of an effective BCG salvage are obvious – avoiding cystectomy is an important goal for many patients and physicians, due to the significant impact on patients QOL.

In this study, the authors specifically focus on the 4N1K-peptide (KRFYVVMWKK). Thrombospondin (TSP)-1 and -2 are recognized as strong angiogenesis inhibitors in various types of cancers. The 4N1K-peptide (KRFYVVMWKK) is derived from TSP-1 and TSP-2, and its expression is significantly associated with tumour progression and survival in several cancers.

EAU image8

In this study, the authors investigated the pathological significance of 4N1K-peptide expression in bladder cancer (BC) specifically, and then went on to evaluate the anti-cancer effects of intra-vesical therapy with 4N1K-peptide using in-vitro cell line studies and an animal model of BC.

They examined 206 BC tissues using immunohistochemistry for 4N1K-peptide expression and then correlated this to clinical outcomes. There were 125 positive patients and 81 negative patients.

4N1K-peptide expression was negatively associated with higher grade (P < 0.001), T-stage (P < 0.001), and metastasis (P = 0.025). Positive 4N1K-peptide expression was associated with improved PFS.

In vitro analyses demonstrated that the percentage of apoptotic cells in 4N1K-peptide positive specimens (mean / SD = 4.7 / 1.8 %) was significantly higher (P < 0.001) than that in 4N1K-peptide-negative specimens (3.8 / 1.8 %). For angiogenesis, 4N1K-peptide expression was negatively associated with micro-vessel density (P = 0.024). Similar analyses were performed for 4NGG-peptide, which has a similar structure to 4N1K-peptide, but does not have any biological activity. n T24 cells, the mean/SD percentage of apoptotic cells in 4N1K-peptide-transfected cells was 7.9 / 1.1%, which was remarkably higher than that in 4NGG-peptide-transfected or non-transfected cells (1.6 / 0.2%). These changes were concentration-dependent.

The orthotopic model was a N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced bladder cancer model, which mimics BC development and heterogeneity quite well. A total of 9 8-week-old mice were treated with intra-vesical injection of 4N1K-peptide (50 mM, twice a week) or saline for 16 weeks. 4 of the 9 mice treated with saline died because of cancer-related symptoms, and muscle invasive cancer was detected in 8 mice (88.9%). In contrast, all mice were alive and muscle invasive disease was not observed at 24 weeks of age in 9 mice treated with 4N1K-peptide. No comment on replicability was made.

Obviously, these results are quite promising. But, much more work needs to be done to establish true causation. The orthotopic model assessment needs to be repeated to establish replicability. Safety was not commented on in the abstract. These all must be assessed prior to translation to clinical trial.

Speaker: Y. Miyata

Co-Authors: Asai A., Yasuda T., Nakamura Y., Sagara Y., Matsuo T., Ohba K., Sakai H.

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd, at the 2018 European Association of Urology Meeting EAU18, 16-20 March, 2018 Copenhagen, Denmark