Abstract 4104: Expression of the immune checkpoint receptor TIGIT in seminoma

A characteristic feature of testicular seminoma is the abundance of immune cells in the tumor microenvironment, raising the possibility that immune checkpoint inhibitors could be a therapeutic option in these tumors. TIGIT (T cell immunoreceptor with Ig and ITIM domains) is an inhibitory immune checkpoint receptor in analogy to PD-1 and drugs targeting TIGIT are currently tested in clinical trials. Little is known about the expression of these proteins in testicular seminomas. Here, we employed immunohistochemistry to determine the relative abundance of TIGIT and PD-1 in relation to the total CD3+immune cell infiltration in a tissue microarray (TMA) constructed from 78 seminoma patients. The fraction of TIGIT+and PD-1+lymphocytes was highly variable in individual cancers and ranged from 2.3% to 69.4% (mean:32.2±14.7%) for TIGIT and from 0.8% to 56.5% (mean:21.6±13.2%) for PD-1. The same high degree of variability was also found for the ratio of PD-1 to TIGITpositive cells that varied from a dominance of TIGIT (PD-1:TIGIT ratio=0.02) in 74% of patients to a predominance of PD-1 (PD-1:TIGIT ratio=12.5) in 23% of patients. In summary, the immune checkpoint receptors TIGIT and PD-1 are abundantly expressed in human seminomas. Once available, anti-TIGIT antibodies, possibly in combination with anti-PD-1 drugs, may be a promising therapeutic option for clinical studies in this cancer type. Citation Format: Maximillian Lennartz, Niclas C. Blessin, Andrea Hinsch, Ronald Simon, Martina Kluth, Kristine Fischer, Claudia Hube-Magg, Wenchao Li, Tim Mandelkow, Nicolaus F. Debatin, Doris Hoflmayer, Guido Sauter, Jakob R. Izbicki, Sarah Minner, Franziska Buscheck, Ria Uhlig, David Dum, Till Krech, Andreas M. Luebke, Corinna Wittmer, Frank Jacbosen, Eike Burandt, Stefan Steurer, Waldemar Wilczak. Expression of the immune checkpoint receptor TIGIT in seminoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4104.