Program DHC-Virtual
20 - 21 January 2021
Abstracts Lymphoid session 3
Abstract
Serpin B9 expression in malignant cells confers resistance to Granzyme B-mediated killing
21 January
09:06 09:18
T. Kimman
Paper

Serpin B9 expression in malignant cells confers resistance to Granzyme B-mediated killing by engineered T or NK cells.

 

Thomas Kimman (1), Anne Slomp (1), Sarah Grabherr (1), Eline van Diest (1), Jan Meeldijk (2), Niels Bovenschen (2), J├╝rgen Kuball (1,3), Zsolt Sebestyen (1), Victor Peperzak (1)
(1) University Medical Center Utrecht, Center for Translational Immunology, Utrecht, (2) University Medical Center Utrecht, Department of Pathology, Utrecht, (3) University Medical Center Utrecht, Department of Hematology, Utrecht
No potential conflicts of interest
Introduction

Chimeric antigen receptor (CAR) T cell therapies, are an effective form of immune therapy that found its way to the clinic. These gene modified T cells use granzyme B to kill tumor cells. Importantly, it was recently reported that expression of granzyme B-inhibitor serpin B9 promotes T cell dysfunction in case of cancer. The goal of our study is to test the effect of serpin B9 expression on the killing capacity of cytotoxic cells, including CAR T cells and NK cells.

Methods

Therefore, Serpin B9 of tumor cells was manipulated either by lentiviral-transduction to overexpress Serpin B9 or by siRNA transfection to transient knockdown serpin B9. We generated CD20 CAR T cells by retroviral transduction of primary T cells. We analyzed serpin B9 expression by Western blot or intracellular flow cytometry. And finally assessed cell death of tumor cells by flow cytometry after a co-culture killing assay with CD20 CAR T cells or NK cells.

Results

First, we confirmed that serpin B9-overexpressing melanoma cells are less sensitive to recombinant granzyme B or to killing by NK cells. Next, we reveal that serpin B9 is expressed abundantly in different B cell malignancies and especially in chronic lymphocytic leukemia (CLL). Knock-down of serpin B9 in diffuse large B cell lymphoma (DLBCL) cells rendered them more sensitive towards killing by CD20 CAR T cells or NK cells. Finally, CD20 CAR T cells select for survival of high serpin B9-expressing primary CLL cells.

Conclusion

Combined, our data exposes serpin B9 as a potential mediator underlying resistance towards engineered T or NK cells and provides a rationale to improve their killing capacity by circumventing serpin B9-mediated inhibition of granzyme B.

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