Institute of Biomedical Sciences

Title

TGFβ resistant Cord Blood derived NK cells as an "off the shelf" Immunotherapy for the treatment of Medulloblastoma

Poster Number

10

Document Type

Poster

Status

Graduate Student - Doctoral

Abstract Category

Cancer/Oncology

Keywords

Medulloblastoma, immunotherapy

Publication Date

Spring 2018

Abstract

Medulloblastoma (MB), the most common pediatric brain tumor, presents with a poor prognosis in a subset of patients with high risk disease. In these patients, current therapies are ineffective. Cord blood (CB) natural killer (NK) cells may be promising off the shelf effector cells for medulloblastoma immunotherapy because they recognize malignant cells without the need for a known target and are readily available from multiple banks. However, they are currently limited by immune suppressive cytokines such as Transforming Growth Factor β (TGF-β) in the MB tumor microenvironment.

To overcome the detrimental effects of TGF-β, we transduced CB-derived NK cells with a retrovirus expressing a dominant negative TGF-β receptor II (DNRII) (mean transduction efficiency of 39.54%, range 20.8 to 75.1%) and evaluated their ability to kill medulloblastoma in the presence of TGF-β.

Following manufacture using GMP compliant methodologies and transduction with DNRII, CB-derived DNRII-transduced NK cells expanded to clinically relevant numbers (mean 769 +/- 308 fold expansion) and retained both their killing ability (mean 21.16+/-8.26% for nontransduced NK cells at E:T of 5:1 vs 18.71+/-7.46% for transduced NK cells, n=5) and their secretion of IFN-γ upon activation. We observed that MB cell killing of CB-NK cells without DNRII expression was reduced (non-transduced cell killing at E:T 5:1 was reduced by 5% from 21.16+/-8.26% to 15.46+/-11.12% in TGF- β rich environment, n=5) while MB cell killing of CB-NK expressing DNRII was increased (mean 12.41+/-10.24% to 20.41+/-10.40% in TGF- β rich environment, n=4). More importantly they exhibit efficacy in vivo, migrating to the site of disease (mean 54.35 cells, n=2), and increasing survival in mice that were engrafted with a MB cell line (p=0.0175 vs untreated animals by Gehan-Breslow-Wilcoxon analysis, n=5 per group).

We have also begun looking at primary medulloblastoma samples, and show that these cells also secrete TGF-β.

In summary, CB NK cells expressing a DNRII have a functional advantage over unmodified NK cells in the presence of TGF-beta-secreting MB and may be an important therapeutic approach for patients with high risk disease.

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TGFβ resistant Cord Blood derived NK cells as an "off the shelf" Immunotherapy for the treatment of Medulloblastoma

Medulloblastoma (MB), the most common pediatric brain tumor, presents with a poor prognosis in a subset of patients with high risk disease. In these patients, current therapies are ineffective. Cord blood (CB) natural killer (NK) cells may be promising off the shelf effector cells for medulloblastoma immunotherapy because they recognize malignant cells without the need for a known target and are readily available from multiple banks. However, they are currently limited by immune suppressive cytokines such as Transforming Growth Factor β (TGF-β) in the MB tumor microenvironment.

To overcome the detrimental effects of TGF-β, we transduced CB-derived NK cells with a retrovirus expressing a dominant negative TGF-β receptor II (DNRII) (mean transduction efficiency of 39.54%, range 20.8 to 75.1%) and evaluated their ability to kill medulloblastoma in the presence of TGF-β.

Following manufacture using GMP compliant methodologies and transduction with DNRII, CB-derived DNRII-transduced NK cells expanded to clinically relevant numbers (mean 769 +/- 308 fold expansion) and retained both their killing ability (mean 21.16+/-8.26% for nontransduced NK cells at E:T of 5:1 vs 18.71+/-7.46% for transduced NK cells, n=5) and their secretion of IFN-γ upon activation. We observed that MB cell killing of CB-NK cells without DNRII expression was reduced (non-transduced cell killing at E:T 5:1 was reduced by 5% from 21.16+/-8.26% to 15.46+/-11.12% in TGF- β rich environment, n=5) while MB cell killing of CB-NK expressing DNRII was increased (mean 12.41+/-10.24% to 20.41+/-10.40% in TGF- β rich environment, n=4). More importantly they exhibit efficacy in vivo, migrating to the site of disease (mean 54.35 cells, n=2), and increasing survival in mice that were engrafted with a MB cell line (p=0.0175 vs untreated animals by Gehan-Breslow-Wilcoxon analysis, n=5 per group).

We have also begun looking at primary medulloblastoma samples, and show that these cells also secrete TGF-β.

In summary, CB NK cells expressing a DNRII have a functional advantage over unmodified NK cells in the presence of TGF-beta-secreting MB and may be an important therapeutic approach for patients with high risk disease.