Introduction

Chimeric antigen receptors (CAR) consisting of an extracellular anti-body based single chain variable fragment (scFv) linked to a transmembrane and intracellular signaling domain can boost anti-tumor activities of effector cells. In this study, we focused on membrane-bound heat shock protein 70 (mHsp70) as a tumor specific target for the recognition by an anti-mHsp70 CAR in NK cell lines. We focused on targeting HNSCC tumors, due to limited treatment options available for late-stage tumors.

Material/Methods

The NK cell line KHYG1 and primary NK cells of a healthy donor were selected as CAR cell platforms and three HNSCC served as tumor target cells. The expression of activatory and inhibitory receptors and mHsp70 on the different NK cell types was performed by flow cytometry. The CAR expression was confirmed by confocal microscopy.

Results

Receptors expression pattern differed significantly in KHYG1 and primary NK cells. A successful transfection of scFv anti-mHsp70 CAR in KHYG1 cells could be confirmed. Due to a mHsp70 positivity of KHYG1 cells the anti-mHsp70 CAR resulted in fratricide among the effector cells. Therefore, we aim to continue with NK92 cells and primary NK cells lacking in mHsp70. Validation of the efficacy of anti-mHsp70 CAR will be performed by cytotoxicity assays.

Discussion

In contrast to CAR T cells causing partially severe side effects such as cytokine release syndrome (CRS) and graft-versus-host disease, our focus is to introduce NK cells of different origins as a platform for the transfection with an anti-mHsp70 to produce an over-the-counter NK cell-based drug.

Conflict of Interest

GM. Is founder and Chief Scientific Officer of multimmune GmbH