Immunotherapy based on immune checkpoint inhibitors (ICIs) has provided revolutionary results in treating various cancers. However, its efficacy in colorectal cancer (CRC), especially in microsatellite stability-CRC, is limited. This study aimed to observe the efficacy of personalized neoantigen vaccine in treating MSS–CRC patients with recurrence or metastasis after surgery and chemotherapy. Candidate neoantigens were analyzed from whole-exome and RNA sequencing of tumor tissues. The safety and immune response were assessed through adverse events and ELISpot. The clinical response was evaluated by progression-free survival (PFS), imaging examination, clinical tumor marker detection, circulating tumor DNA (ctDNA) sequencing. Changes in health-related quality of life were measured by the FACT-C scale. A total of six MSS–CRC patients with recurrence or metastasis after surgery and chemotherapy were administered with personalized neoantigen vaccines. Neoantigen-specific immune response was observed in 66.67% of the vaccinated patients. Four patients remained progression-free up to the completion of clinical trial. They also had a significantly longer progression-free survival time than the other two patients without neoantigen-specific immune response (19 vs. 11 months). Changes in health-related quality of life improved for almost all patients after the vaccine treatment. Our results shown that personalized neoantigen vaccine therapy is likely to be a safe, feasible and effective strategy for MSS–CRC patients with postoperative recurrence or metastasis.

Neoantigens play a crucial role in cancer immunotherapy. However, the effectiveness and safety of neoantigen-based immunotherapies in patients with colorectal cancer (CRC), particularly in the Chinese population, have not been well studied. This study explored the feasibility and effectiveness of neoantigens in the treatment of CRC. Whole-exome sequencing (WES) and transcriptome sequencing were used to identify somatic mutations, RNA expression, and human leukocyte antigen (HLA) alleles. Neoantigen candidates were predicted, and immunogenicity was assessed. The neoantigens TSHZ3-L523P, RARA-R83H, TP53-R248W, EYA2-V333I, and NRAS-G12D from Patient 4 (PW4); TASP1-P161L, RAP1GAP-S215R, MOSPD1-V63I, and NAV2-D1973N from Patient 10 (PW10); and HAVCR2-F39V, SEC11A-R11L, SMPDL3B-T452M, LRFN3-R118Q, and ULK1-S248L from Patient 11 (HLA-A0201⁺PW11) induced a heightened neoantigen-reactive T cell (NRT) response as compared with the controls in peripheral blood lymphocytes (PBLs) isolated from patients with CRC. In addition, we identified neoantigen-containing peptides SEC11A-R11L and ULK1-S248L from HLA-A0201⁺PW11, which more effectively elicited specific CTL responses than the corresponding native peptides in PBLs isolated from HLA-A0201⁺PW11 as well as in HLA-A2.1/K^b transgenic mice. Importantly, adoptive transfer of NRTs induced by vaccination with two mutant peptides could effectively inhibit tumor growth in tumor-bearing mouse models. These data indicate that neoantigen-containing peptides with high immunogenicity represent promising candidates for peptide-mediated personalized therapy. Abbreviations: CRC: colorectal cancer; DCs: dendritic cells; ELISPOT: enzyme-linked immunosorbent spot; E:T: effector:target; HLA: human leukocyte antigen; MHC: major histocompatibility complex; Mut: mutant type; NGS: next-generation sequencing; NRTs: neoantigen-reactive T cells; PBMCs: peripheral blood mononuclear cells; STR: short tandem repeat; PBLs: peripheral blood lymphocytes; PBS: phosphate-buffered saline; PD-1: programmed cell death protein 1; TILs: tumor-infiltrating lymphocytes; RNA-seq: RNA sequencing; Tg: transgenic; TMGs: tandem minigenes; WES: whole-exome sequencing; WT: wild-type.

Hitherto, it has been identified that numerous basic-helix-loop-helix (bHLH) transcription factors play vital roles in tumor initiation and progression. Atonal homolog 8 (ATOH8) is a member of the bHLH family of transcription factors, which participates in embryogenesis and the development of various tissues. Several studies have demonstrated that ATOH8 is involved in the progression of malignancies; however, the effects of ATOH8 in colorectal cancer (CRC) remain unknown. The aim of the present study was to explore the expression and function of ATOH8 in CRC. The present study included 106 paired CRCs and peritumoral samples. The expression of ATOH8 was evaluated by immunohistochemistry, and the results were compared with the clinical outcomes of the patients. Furthermore, cell proliferation, cell cycle distribution, wound healing and cytotoxicity assays were performed in colon cancer cell line SW620. Immunohistochemical analyses revealed that the expression of ATOH8 in CRC tissues was significantly increased compared with the peritumoral tissues, and that the high expression of ATOH8 was associated with a high serum carcinoembryonic antigen (CEA) level and a worse overall survival. In vitro assays revealed that ATOH8 knockdown in colon cancer cells inhibited cell proliferation, induced cell cycle arrest at the S phase, and increased the percentage of apoptotic cells and sensitivity to 5-fluorouracil (5-FU). The present study suggests that ATOH8 promotes the progression of CRC and may potentially serve as a novel prognostic predictor and potential therapeutic target in CRC.

Besides participating in diverse pathological and physiological processes, extracellular vesicles (EVs) are also excellent drug‐delivery vehicles. However, clinical drugs modulating EV levels are still lacking. Here, we show that proton pump inhibitors (PPIs) reduce EVs by enhancing macropinocytosis‐mediated EV uptake. PPIs accelerate intestinal cell endocytosis of autocrine immunosuppressive EVs through macropinocytosis, thereby aggravating inflammatory bowel disease. PPI‐induced macropinocytosis facilitates the clearance of immunosuppressive EVs from tumour cells, improving antitumor immunity. PPI‐induced macropinocytosis also increases doxorubicin and antisense oligonucleotides of microRNA‐155 delivery efficiency by EVs, leading to enhanced therapeutic effects of drug‐loaded EVs on tumours and acute liver failure. Mechanistically, PPIs reduce cytosolic pH, promote ATP6V1A (v‐ATPase subunit) disassembly from the vacuolar membrane and enhance the assembly of plasma membrane v‐ATPases, thereby inducing macropinocytosis. Altogether, our results reveal a mechanism for macropinocytic regulation and PPIs as potential modulators of EV levels, thus regulating their functions.

Several studies have demonstrated that calpain‑1 is involved in a variety of pathophysiological processes, including tumorigenesis. However, the clinical relevance and role of calpain‑1 in colorectal cancer (CRC) are unclear. Filamin A (FLNA) is an actin‑binding protein that participates in cancer progression and can be cleaved by calpain‑1. In the present study, the protein expression levels of calpain‑1 and FLNA were detected by immunohistochemistry in 467 matched cancerous and paracancerous tissues from patients with CRC. The staining results and the clinicopathological characteristics of the patients were comprehensively analyzed. A high expression level of calpain‑1 was strongly associated with age, metastasis, Dukes stage and survival time but not with sex, histologic grade, tumour location or tumor size. By contrast, a low expression level of FLNA was significantly associated with tumor size, histological grade, metastasis, Dukes stage and survival time, but not with age, sex, or tumor location. Kaplan‑Meier survival analysis demonstrated that patients with calpain‑1 overexpression had a shorter mean overall survival (OS) than patients with lower levels of calpain‑1 expression. Unlike high levels of calpain‑1, high levels of FLNA were associated with longer OS than lower levels of FLNA expression. Furthermore, calpain‑1 expression was inversely correlated with FLNA expression. The relationship between calpain‑1 and FLNA was further confirmed using CRC cell lines in vitro. When calpain‑1 expression decreased in CRC cells, FLNA expression increased. Furthermore, calpain‑1 knockdown in CRC cells resulted in decreased proliferation, colony formation, migration and invasion. The present findings suggest that calpain‑1 overexpression predicted a poor outcome in patients with CRC and promoted tumor progression, possibly via FLNA downregulation.