Nanocomplex-based TP53 gene therapy promotes anti-tumor immunity through TP53- and STING-dependent mechanisms

ABSTRACT

Loss or mutation of TP53 has been linked to alterations in anti-tumor immunity as well as dysregulation of cell cycle and apoptosis. We explored immunologic effects and mechanisms following restoration of wild-type human TP53 cDNA in murine oral cancer cells using the therapeutic nanocomplex scL-53. We demonstrated scL-53 induces dose-dependent expression of TP53 and induction of apoptosis and immunogenic cell death. We further demonstrated both TP53-dependent and independent induction of tumor cell immunogenicity through the use of blocking mAbs, nanocomplex loaded with DNA plasmid with or without TP53 cDNA, empty nanocomplex and siRNA knockdown techniques. TP53-independent immune modulation was observed following treatment with nanocomplex loaded with DNA plasmid lacking TP53 cDNA and abrogated in STING-deficient tumor cells, supporting the presence of a cytoplasmic DNA sensing, STING-dependent type-I IFN response. Cooperatively, TP53- and STING-dependent alterations sensitized tumor cells to CTL-mediated lysis, which was further enhanced following reversal of adaptive immune resistance with PD-1 mAb. In vivo, combination scL-53 and PD-1 mAb resulted in growth control or rejection of established tumors that was abrogated in mice depleted of CD8+ cells or in STING deficient mice. Cumulatively, this work demonstrates 1) a direct anti-tumor effects of functional TP53; 2) non-redundant TP53- and STING-dependent induction of tumor cell immunogenicity following scL-53 treatment; and 3) that adaptive immune resistance following scL-53 treatment can be reversed with PD-based immune checkpoint blockade, resulting in the rejection or control of syngeneic murine tumors. These data strongly support the clinical combination of scL-53 and immune checkpoint blockade.

KEYWORDS:

• adaptive immune resistance
• checkpoint inhibitor
• Gene therapy
• immunity
• nanocomplex
• STING
• TP53

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Disclosure of potential conflicts of interest

Dr. Chang is one of the inventors of the described nanodelivery technology, for which several patents owned by Georgetown University have been issued. The patents have been licensed to SynerGene Therapeutics Inc. for commercial development. Dr. Chang owns equity interests in SynerGene Therapeutics Inc. and serves as a non-paid scientific consultant to SynerGene Therapeutics Inc.

Financial support

This work was supported by the Intramural Research Program of the NIH, NIDCD, project number ZIA-DC000087 and DC000074.

Acknowledgments

We thank Drs. Ravindra Uppaluri and Nicole Schmitt for their critical review of this manuscript.

Funding

HHS | NIH | National Institute on Deafness and Other Communication Disorders (NIDCD), DC000074, HHS | NIH | National Institute on Deafness and Other Communication Disorders (NIDCD), DC000087