Abstract 5131: TYMS overexpression - but not copy number alteration - is associated with cancer aggressiveness in urothelial bladder cancer
Authors: Plage Henning , Hofbauer Sebastian , Furlano Kira , Weinberger Sarah , Franz Antonia , Fendler Annika , Roßner Florian , Schallenberg Simon , Elezkurtaj Sefer , Frericks Adrian , Lennartz Maximilian , Marx Andreas H. , Samtleben Henrik , Fisch Margit , Rink Michael , Slojewski Marcin , Kaczmarek Krystian , Ecke Thorsten , Koch Stefan , Adamini Nico , Simon Ronald , Sauter Guido , Zecha Henrik , Weischenfeldt Joachim , Klatte Tobias , Minner Sarah , Horst David , Schlomm Thorsten , Kluth Martina 
Published: March 2024

Background: Thymidylate Synthetase (TYMS) is an import enzyme in the early stage of DNA biosynthesis. It is coded by the TYMS gene at 18p11.32, a region which has been found amplified in urothelial carcinoma. TYMS is a target enzyme for 5-fluorouracil (5-FU) and methotrexate. Elevated TYMS expression has been associated with poor prognosis and unfavorable therapy response in different cancer types. The aim of this study was to clarify the clinical relevance of TMYS expression in urothelial carcinoma and to determine the relationship between TYMS expression and gene amplification.

Design: TYMS expression was analyzed by immunohistochemistry and TYMS copy number status was determined by fluorescence in-situ hybridization on a tissue microarray (TMA) containing more than 2,700 urothelial carcinomas of the urinary bladder including &gt;600 patients who had undergone cystectomy for muscle-invasive disease and for which follow-up data were available.

Results: TMYS immunostaining was detectable in 83.1% of 1,799 analyzable bladder cancers, including 56.4% with weak, 14.4% with moderate, and 12.3% with strong staining. The rate of strongly TMYS positive cancers increased markedly from pTaG2 low (0.3%) to pTaG2 high (4.1%), and pTaG3 cancers (11.8%; p&lt;0.0001) and was even somewhat higher in pT2-4 cancers (16.7%; p=0.6401; pTaG3 vs pT2-4). In muscle-invasive cancers, the frequency of strong TMYS

immunostaining increased with tumor stage (p=0.0011) and grade (p=0.0007) but was lower in lymph node positive cancers (p=0.0018). No association was found between TYMS expression and patient prognosis. TYMS amplification was found in 3.1% and TMYS deletion in 1.2% of 1,775 analyzable bladder cancers. The rate of TYMS amplification increased from pTa (0.6%) to pT2-4 (3.7%; p&lt;0.0001) cancers whereas TYMS deletion was only found in pT2-4 (1.4%) cancers. In muscle invasive-cancers, TYMS copy number alterations were unrelated to tumor phenotype and patient prognosis. Strong TYMS positivity was significantly associated with TYMS amplification (p=0.0096) but only 28.6% of 42 amplified cancers showed a strong TMYS staining and only 7.2% of strongly TYMS positive cancers had a TYMS amplification.

Conclusion: The significant association between TYMS overexpression and parameters of aggressive phenotype are consistent with a role of TYMS in bladder cancer progression. The incomplete association between TYMS amplification and overexpression demonstrates that TYMS is not the critical target of 18p11 amplification in bladder cancer and that TYMS upregulation is in most cases due to other mechanisms than amplification.

Citation Format: Henning Plage, Sebastian Hofbauer, Kira Furlano, Sarah Weinberger, Antonia Franz, Annika Fendler, Florian Roßner, Simon Schallenberg, Sefer Elezkurtaj, Adrian Frericks, Maximilian Lennartz, Andreas H. Marx, Henrik Samtleben, Margit Fisch, Michael Rink, Marcin Slojewski, Krystian Kaczmarek, Thorsten Ecke, Stefan Koch, Nico Adamini, Ronald Simon, Guido Sauter, Henrik Zecha, Joachim Weischenfeldt, Tobias Klatte, Sarah Minner, David Horst, Thorsten Schlomm, Martina Kluth. TYMS overexpression - but not copy number alteration - is associated with cancer aggressiveness in urothelial bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5131.