Chimeric antigen receptor (CAR) T cells have been proven effective for the treatment of B-cell-mediated malignancies. Currently, the development of efficient tools that supply CAR T cells for the treatment of other malignancies would have great impact. In this study, interleukin (IL)-15 and C-C motif chemokine ligand 19 (CCL19) were introduced into natural killer group 2D (NKG2D)-based CARs to generate 15×19 CAR T cells, which remarkably increased T-cell expansion and promoted the production of central memory T (Tcm) cells. 15×19 CAR T cells showed greater cytotoxicity to gastric cell lines than conventional CAR T cells and produced higher levels of IL-15 and CCL-19, which resulted in increased responder T cell chemotaxis and reduced expression of T cell exhaustion markers. A live zebrafish model was used for single-cell visualization of local cytotoxicity and metastatic cancers. Administration of 15×19 CAR T cells resulted in significant shrinking of gastric cancer xenograft tumors and expansion of 15×19 CAR T cells in zebrafish models. Taken together, these findings demonstrate that 15×19 CAR T cells are highly efficient in killing gastric cancer cells, are effective to avoid off-target effects, and migrate to local and metastatic sites for long-term surveillance of cancers.

The efficacy of conventional treatments for pancreatic cancer remains unsatisfactory, and immunotherapy is an emerging option for adjuvant treatment of this highly deadly disorder. The tumor-associated antigen (TAA) MUC1 is expressed in a variety of human cancers and is overexpressed in more than 90% of pancreatic cancer, which makes it an attractive target for cancer immunotherapy. As a self-protein, MUC1shows a low immunogenicity because of immune tolerance, and the most effective approach to breaking immune tolerance is alteration of the antigen structure. In this study, the altered MUC1 1068-1076Y1 epitope (YLQRDISEM) by modification of amino acid residues in sequences presented a higher immunogenicity and elicited more CTLs relative to the wild-type (WT) MUC1 1068-1076 epitope (ELQRDISEM). In addition, the altered MUC1 1068-1076Y1 epitope was found to cross-recognize pancreatic cancer cells expressing WT MUC1 peptides in an HLA-A0201-restricted manner and trigger stronger immune responses against pancreatic cancer via the perforin/granzyme apoptosis pathway. As a potential HLA-A0201-restricted CTL epitope, the altered MUC1 1068-1076Y1 epitope is considered as a promising target for immunotherapy of pancreatic cancer. Alteration of epitope residues may be feasible to solve the problem of the low immunogenicity of TAA and break immune tolerance to induce immune responses against human cancers.

Objective: Neoantigens arising from gene mutations in tumors can induce specific immune responses, and neoantigen-based immunotherapies have been tested in clinical trials. Here, we characterized the efficacy of altered neoepitopes in improving immunogenicity against gastric cancer. Methods: Raw data of whole-exome sequencing derived from a patient with gastric cancer were analyzed using bioinformatics methods to identify neoepitopes. Neoepitopes were modified by P1Y (the first amino acid was replaced by tyrosine) and P2L (the second amino acid was replaced by leucine). T2 binding and stability assays were used to detect the affinities between the neoepitopes and the HLA molecules, as well as the stabilities of complexes. Dendritic cells (DCs) presented with neoepitopes stimulated naïve CD8 + T cells to induce specific cytotoxic T lymphocytes. ELISA and carboxyfluorescein succinimidyl ester were used to detect IFN-γ and TNF-α levels, and T cell proliferation. Perforin was detected by flow cytometry. The cytotoxicity of T cells was determined using the lactate dehydrogenase assay. Results: Bioinformatics analysis, T2 binding, and stability assays indicated that residue substitution increased the affinity between neoepitopes and HLA molecules, as well as the stabilities of complexes. DCs presented with altered neoepitopes stimulated CD8 + T cells to release more IFN-γ and had a greater effect on promoting proliferation than wild-type neoepitopes. CD8 + T cells stimulated with altered neoepitopes killed more wild-type neoepitope-pulsed T2 cells than those stimulated with wild-type neoepitopes, by secreting more IFN-γ, TNF-α, and perforin. Conclusions: Altered neoepitopes exhibited greater immunogenicity than wild-type neoepitopes. Residue substitution could be used as a new strategy for immunotherapy to target neoantigens.

High‐frequency mutation of the TP53 tumor suppressor gene is observed in multiple human cancers, which promotes cancer progression. However, the mutated gene‐encoded protein may serve as a tumor antigen to elicit tumor‐specific immune responses. In this study, we detected widespread expression of shared TP53‐Y220C neoantigen in hepatocellular carcinoma with low affinity and low stability of binding to HLA‐A0201 molecules. We substituted the amino acid sequences VVPCEPPEV with VLPCEPPEV in the TP53‐Y220C neoantigen to yield a TP53‐Y220C (L2) neoantigen. This altered neoantigen was found to increase affinity and stability and induce more cytotoxic T lymphocytes (CTLs), indicating improvements in immunogenicity. In vitro assays showed the cytotoxicity of CTLs stimulated by both TP53‐Y220C and TP53‐Y220C (L2) neoantigens against multiple HLA‐A0201‐positive cancer cells expressing TP53‐Y220C neoantigens; however, the TP53‐Y220C (L2) neoantigen showed higher cytotoxicity than the TP53‐Y220C neoantigen against cancer cells. More importantly, in vivo assays demonstrated greater inhibition of hepatocellular carcinoma cell proliferation by TP53‐Y220C (L2) neoantigen‐specific CTLs relative to TP53‐Y220C neoantigen in zebrafish and nonobese diabetic/severe combined immune deficiency mouse models. The results of this study demonstrate enhanced immunogenicity of the shared TP53‐Y220C (L2) neoantigen, which has the potential as dendritic cells or peptide vaccines for multiple cancers.