W188 - Improving NK Cell Immunotherapy Against Rhabdomyosarcoma

Lisa Marie Reindl – Goethe University Frankfurt; Lida Jalili – Goethe University Frankfurt; Victoria Grèze – Goethe University Frankfurt; philipp Wendel – Goethe University Frankfurt; Vinzenz Särchen – Goethe University Frankfurt; Winfried Wels – Georg Speyer Haus Frankfurt; Meike Vogler – Goethe University Frankfurt

Abstract Text: Natural killer (NK) cells are innate effector cells known for their high intrinsic cytotoxic capacity and the possibility to be safely applied as ‘off-the-shelf’ third party donor cell therapy. CD19-specific chimeric antigen receptor (CAR)-expressing NK cells showed promise for the treatment of B-cell malignancies, while so far only limited data exist on the potential of CAR-NK cells as a therapy for solid tumors.
Here, we investigated peripheral blood derived NK cells for the treatment of rhabdomyosarcoma (RMS), the most common soft tissue cancer in pediatric patients.

Relevant pathways in the NK-RMS interaction were studied by RNA sequencing analysis and RT-qPCR. The cytotoxic potential of NK cells was analyzed in 2D-cultures and 3D spheroids. Interestingly, we observed a decrease in NK cell cytotoxicity in rechallenge killing assays following pre-cultivation of NK with RMS cells (E:T=5:1) for 2 hours in comparison to non-challenged NK cells, indicating that the NK-RMS interaction impaired NK antitumor activity. Blocking the inhibitory NKG2A-HLA-E and the PD-1/PD-L1 axis by CRISPR/Cas9-mediated KO of the respective receptor in NK cells did not improve NK-cell mediated cytotoxicity.

To enhance tumor cell recognition, CAR-NK cells were engineered by lentiviral transduction to express a cetuximab-derived CAR (225.28.z) that targets the epidermal growth factor receptor (EGFR). EGFR-CAR NK cells showed stable CAR expression (35-60%), a similar surface marker profile as non-transduced NK cells, and significantly increased cytotoxicity against both, the alveolar RMS cell line RH30 and the embryonal RMS cell line RD. Efficacy of EGFR-CAR NK cells against chemotherapy-resistant RMS are currently investigated.