Die Kombination der therapeutischen Antikörper Cetuximab und Trastuzumab mit einem TIGIT-blockierenden Antikörper steigert die Zytotoxizität von NK-Zellen gegen EGFR- und ERBB2-positive primäre Glioblastomzellen

Natural Killer (NK) cells are emerging as promising tools in cellular immunotherapy for cancer treatment. In contrast to T cells, NK cells are devoid of recombined immunoreceptors and recognize tumor cells by a set of inherited natural cytotoxicity receptors as well as activating and inhibitory receptors of the immunoglobulin and lectin superfamily. Glioblastoma (GBM) cells express inhibitory ligands for NK cell receptors, such as CD155/poliovirus receptor (PVR), which dampen NK cell activity by engaging the inhibitory receptor TIGIT (T cell immunoreceptor with Ig and ITIM domains) on NK cells. Interestingly, TIGIT expression is upregulated on both activated NK cells and on NK cells derived from cancer patients. This study aimed to explore whether TIGIT-blockade improves cytotoxic responses of NK cells against GBM cells treated with therapeutic antibodies Cetuximab and Trastuzumab.

Primary NK cells were isolated from the blood of healthy donors. On the day of isolation and after 10 days in co-culture with a PC-3 feeder cell line constitutively expressing IL-2, membrane-bound IL-15 and 4-1BBL, NK cells were analyzed by flow cytometry for immune checkpoint molecules and activating and inhibitory receptors. Subsequently, the cytotoxicity of the in vitro expanded NK cells against the CD155+ primary GBM cell lines HT7606, HT18584, HT12347, HT16360-1 and HT18328-3 constitutively expressing mKATE2 was investigated by IncuCyte assays employing combinations of TIGIT-blocking antibody, Cetuximab and Trastuzumab.

Expanded NK cells showed a higher expression of TIGIT than fresh NK cells from peripheral blood. Blocking of TIGIT lead to an increase in NK cell-mediated specific lysis of GBM cell lines (HT18584: median 21.6%, HT16360-1: median 44.8%) compared to control NK cells (HT18584: median 10.8%, HT16360-1: median 37.2%). The combination of a TIGIT-blocking antibody and either Cetuximab (HT18584: median 34.7%, HT16360-1: median 49.5%) or Trastuzumab (HT18584: median 33.9%, HT16360-1: median 55.1%) lead to an even higher percentage of NK cell-mediated specific killing of GBM cell lines.

The results demonstrate that the combination of Cetuximab/Trastuzumab and a TIGIT-blocking antibody leads to an improved cytotoxicity of in vitro expanded primary NK cells towards glioblastoma cells by overcoming the immunosuppressive effect of CD155. Therefore, TIGIT serves as promising target structure for future studies and clinical approaches.