The Epitope Basis of Embryonic Stem Cell-Induced Antitumor Immunity against Bladder Cancer

Engineered Genetic Circuits Activated by Bezafibrate Improve ESC-Based TAA Cancer Vaccine Efficacy and PD-L1 Nanobody Therapy

Immunotherapy targeting tumor antigens and immune checkpoint inhibitors has garnered significant attention in cancer treatment. Synthetic gene circuits are developed, encoded in plasmids, which regulate the expression of tumor antigens shared with embryonic stem cells (ESCs) and PD-L1 nanobody (PD-L1 nb) in response to bezafibrate stimulation. This approach significantly minimizes side effects and improved therapeutic efficacy. The transcriptional switches leverage the interaction between the bezafibrate-responsive transcriptional activator PPARγ and RXRα, which are fused with the VPR/VP64/p65 activation domains (AD) and the Gal4 DNA-binding domain (DBD), respectively. These synthetic constructs are validated and their ability to modulate gene expression upon bezafibrate treatment are confirmed. Notably, the gene expression is precise and tunable in response to bezafibrate administration. HEK293T cells or ESCs are employed to deliver this gene circuit, or the plasmids containing the circuit into the tumor are directly injected. Administration of bezafibrate reduces tumor growth, increases specific CD8+ T cells, and mitigates CD8+ T cell exhaustion, underscoring the feasibility and effectiveness of the approach. ESC-based and intratumoral delivery of the synthetic gene circuits and cargo genes, particularly PD-L1 nb, significantly inhibit tumor growth. PD-L1 nb effectively blocks PD-L1 expression both in vitro and in vivo, as confirmed by using a mutant PD-L1 nb sequence.

Enhancing immune responses of ESC-based TAA cancer vaccines with a novel OMV delivery system

Embryonic stem cell (ESC)-derived epitopes can act as therapeutic tumor vaccines against different types of tumors Jin (Adv Healthc Mater 2023). However, these epitopes have poor immunogenicity and stimulate insufficient CD8+ T cell responses, which motivated us to develop a new method to deliver and enhance their effectiveness. Bacterial outer membrane vesicles (OMVs) can serve as immunoadjuvants and act as a delivery vector for tumor antigens. In the current study, we engineered a new OMV platform for the co-delivery of ESC-derived tumor antigens and immune checkpoint inhibitors (PD-L1 antibody). An engineered Staphylococcal Protein A (SpA) was created to non-specifically bind to anti-PD-L1 antibody. SpyCatcher (SpC) and SpA were fused into the cell outer membrane protein OmpA to capture SpyTag-attached peptides and PD-L1 antibody, respectively. The modified OMV was able to efficiently conjugate with ESC-derived TAAs and PD-L1 antibody (SpC-OMVs + SpT-peptides + anti-PD-L1), increasing the residence time of TAAs in the body. The results showed that the combination therapy of ESC-based TAAs and PD-L1 antibody delivered by OMV had significant inhibitory effects in mouse tumor model. Specifically, it was effective in reducing tumor growth by enhancing IFN-γ-CD8+ T cell responses and increasing the number of CD8+ memory cells and antigen-specific T cells. Overall, the new OMV delivery system is a versatile platform that can enhance the immune responses of ESC-based TAA cancer vaccines.