(235f) Engineering Peptides for an All-Inclusive Immune Response

Background: Cells swell, form bubbles and pores, and eventually burst in the process of pyroptosis; a recently defined programmed cell death.^1,2 Pyroptosis is initiated by cell membrane permeabilizing, results in release of damage-associated molecular patterns (DAMPs) and tumor associated antigens in cancer. Released DAMPs stimulate the protective immune response through cancer specific CD8 T cell activation. In a recent study tumor clearance was achieved via pyroptotic cell death on mice with a subsequent anti-tumor,³ which highlights the importance of pyroptosis as a potential cancer immunotherapy treatment. However, the current pyroptosis studies are based on genetically modified cell lines, as there is no drug available inducing solely pyroptosis, because the activation of these proteins are not fully elucidated. Only known initiators of pyroptosis are molecular pattern signals and amyloid fibers, as in amyloidosis.¹ By mimicking the key interactions in amyloids, we created a new peptide-based platform for an All-Inclusive Immune Response (PAIIR); consists of a pair of oppositely charged hexapeptides that self-assemble into and amyloid-like fibrillar structures, stick on the cell membrane immediately, initiate pyroptosis effectively on cancer cells.

Methods: The design and characterization of PAIIR has been studied fully based on its amyloid structure, via Congo red staining, FTIR, CD, AFM and TEM. The cell culture studies were done on highly resistant ovarian cancer cell line (OVCAR-8) and the proteins were analyzed via Western blotting and ELISA.

Results: The zwitterionic surface of PAIIR provides immediate interaction with the cell surface. Incubation of highly drug resistant ovarian cancer cell line OVCAR-8 with PAIIR for 6h resulted in significant cell death (Fig. 1). Pyroptosis is defined by the bubbles emerging from the plasma membrane (Fig. 1B) and caspase-3-GSDME pathway (Fig. 1C). We also demonstrated that PAIIR does not flow in the medium; therefore, it is unlikely that PAIIR will flow in the body and damage locations away from the site of injection.

We showed an engineered peptide-based platform, PAIIR, as an immune modulator peptide-assembly in this study, with high potential to use and improve the cancer immunotherapy. In vivo studies on eradicating various cancer types with PAIIR are ongoing. The results will include thorough cytokine analyses that will also identify the time-range of the immune response.

References:

(1) Liu, X.; Lieberman, J. Annual Review of Immunology 2020, 38 (1), 455–485.

(2) Ruan, J.; Xia, S.; Liu, X.; Lieberman, J.; Wu, H. Nature 2018, 557 (7703), 62–67.

(3) Zhang, Z.; Zhang, Y.; Xia, S.; Kong, Q.; Li, S.; I. et al. Nature 2020, 579 (7799), 415–420.