Background: Immune checkpoint inhibitors (ICIs), including anti-PD-1 therapy, have limited efficacy in patients with microsatellite stable (MSS) colorectal cancer (CRC). Interleukin 17A (IL-17A) activity leads to a protumor microenvironment, dependent on its ability to induce the production of inflammatory mediators, mobilize myeloid cells and reshape the tumor environment. In the present study, we aimed to investigate the role of IL-17A in resistance to antitumor immunity and to explore the feasibility of anti-IL-17A combined with anti-PD-1 therapy in MSS CRC murine models. Methods: The expression of programmed cell death-ligand 1 (PD-L1) and its regulation by miR-15b-5p were investigated in MSS CRC cell lines and tissues. The effects of miR-15b-5p on tumorigenesis and anti-PD-1 treatment sensitivity were verified both in vitro and in colitis-associated cancer (CAC) and APC^min/+ murine models. In vivo efficacy and mechanistic studies were conducted using antibodies targeting IL-17A and PD-1 in mice bearing subcutaneous CT26 and MC38 tumors. Results: Evaluation of clinical pathological specimens confirmed that PD-L1 mRNA levels are associated with CD8+ T cell infiltration and better prognosis. miR-15b-5p was found to downregulate the expression of PD-L1 at the protein level, inhibit tumorigenesis and enhance anti-PD-1 sensitivity in CAC and APC^min/+ CRC models. IL-17A led to high PD-L1 expression in CRC cells through regulating the P65/NRF1/miR-15b-5p axis. Combined IL-17A and PD-1 blockade had efficacy in CT26 and MC38 tumors, with more cytotoxic T lymphocytes cells and fewer myeloid-derived suppressor cells in tumors. Conclusions: IL-17A increases PD-L1 expression through the p65/NRF1/miR-15b-5p axis and promotes resistance to anti-PD-1 therapy. Blocking IL-17A improved the efficacy of anti-PD-1 therapy in MSS CRC murine models. IL-17A might serve as a therapeutic target to sensitize patients with MSS CRC to ICI therapy.

Background: Although numerous studies have indicated that activated pyroptosis can enhance the efficacy of antitumour therapy in several tumours, the precise mechanism of pyroptosis in colorectal cancer (CRC) remains unclear.Methods: Pyroptosis in CRC cells treated with antitumour agents was assessed using various techniques, including Western blotting, lactate dehydrogenase release assay and microscopy analysis. To uncover the epigenetic mechanisms that regulate NLRP3, chromatin changes and NLRP3 promoter histone modifications were assessed using Assay for Transposase‐Accessible Chromatin using sequencing and RNA sequencing. Chromatin immunoprecipitation‒quantitative polymerase chain reaction was used to investigate the NLRP3 transcriptional regulatory mechanism. Additionally, xenograft and patient‐derived xenograft models were constructed to validate the effects of the drug combinations.Results: As the core molecule of the inflammasome, NLRP3 expression was silenced in CRC, thereby limiting gasdermin D (GSDMD)‐mediated pyroptosis. Supplementation with NLRP3 can rescue pyroptosis induced by antitumour therapy. Overexpression of HDAC2 in CRC silences NLRP3 via epigenetic regulation. Mechanistically, HDAC2 suppressed chromatin accessibility by eliminating H3K27 acetylation. HDAC2 knockout promotes H3K27ac‐mediated recruitment of the BRD4‐p‐P65 complex to enhance NLRP3 transcription. Inhibiting HDAC2 by Santacruzamate A in combination with classic antitumour agents (5‐fluorouracil or regorafenib) in CRC xenograft‐bearing animals markedly activated pyroptosis and achieved a significant therapeutic effect. Clinically, HDAC2 is inversely correlated with H3K27ac/p‐P65/NLRP3 and is a prognostic factor for CRC patients.Conclusion: Collectively, our data revealed a crucial role for HDAC2 in inhibiting NLRP3/GSDMD‐mediated pyroptosis in CRC cells and highlighted HDAC2 as a potential therapeutic target for antitumour therapy.Highlights: Silencing of NLRP3 limits the GSDMD‐dependent pyroptosis in colorectal cancer. HDAC2‐mediated histone deacetylation leads to epigenetic silencing of NLRP3. HDAC2 suppresses the NLRP3 transcription by inhibiting the formation of H3K27ac/BRD4/p‐P65 complex. Targeting HDAC2 activates pyroptosis and enhances therapeutic effect.

Homeobox B9 (HOXB9) is involved in the occurrence and development of malignant tumors. However, the functions and underlying molecular mechanisms of HOXB9 in pancreatic cancer have yet to be identified. In this study, we find that both HOXB9 mRNA and protein levels are down-regulated in pancreatic cancer tissues and cell lines. Kaplan-Meier survival plots of 150 pancreatic cancer cases show that higher expression of HOXB9 in pancreatic cancer patients is associated with higher survival rates. We also find that over-expression of HOXB9 inhibits pancreatic cancer cell proliferation both in cell lines and the nude mouse xenograft as well as PDX models. Applying cell cycle PCR array analysis, Flow CytoMetry, ChIP-qPCR, and luciferase experiments, we observe that HOXB9 blocks cell cycle progression in the G0/G1 phase via up-regulating RBL2 and inhibiting c-Myc, and we further find that DNMT1 inhibits the expression of HOXB9 in pancreatic cancer by promoting the methylation of its promoter. Our findings highlight a novel mechanism of the DNMT1/HOXB9/RBL2/c-Myc pathway in regulating the cell cycle and proliferation of pancreatic cancer cells and provide a research basis for the prognosis and therapeutic application of HOXB9 in pancreatic cancer.

Spontaneous clearance of hepatitis B virus (HBV) is frequent in adults (95%) but rare in infants (5%), emphasizing the critical role of age-related hepatic immunocompetence. However, the underlying mechanisms of hepatocyte-specific immunosurveillance and age-dependent HBV clearance remain unclear. Here, we identified PGLYRP2 as a hepatocyte-specific pattern recognition receptor with age-dependent expression, and demonstrated that phase separation of PGLYRP2 was a critical driver of spontaneous HBV clearance in hepatocytes. Mechanistically, PGLYRP2 recognized and potentially eliminated covalently closed circular DNA via phase separation, coordinated by its intrinsically disordered region and HBV DNA-binding domain (PGLYRP2 ^{IDR/209–377} ) in the nucleus. Additionally, PGLYRP2 suppressed HBV capsid assembly by directly interacting with the viral capsid, mediated by its PGRP domain. This interaction promoted the nucleocytoplasmic translocation of PGLYRP2 and subsequent secretion of the PGLYRP2/HBV capsid complex, thereby bolstering the hepatic antiviral response. Pathogenic variants or deletions in PGLYRP2 impaired its ability to inhibit HBV replication, highlighting its essential role in hepatocyte-intrinsic immunity. These findings suggest that targeting the PGLYRP2-mediated host-virus interaction may offer a potential therapeutic strategy for the development of anti-HBV treatments, representing a promising avenue for achieving a functional cure for HBV infection.

AT-rich interactive domain-containing protein 1A (ARID1A), a core constituent of the switch/sucrose nonfermentable (SWI/SNF) complex, is mutated in approximately 10% of colorectal cancers. Whereas ARID1A deficiency corresponds to heightened immune activity in colorectal cancer, immune checkpoint inhibitors (ICI) have shown limited efficacy in these tumors. The discovery of targetable vulnerabilities associated with ARID1A deficiency in colorectal cancer could expand treatment options for patients. In this study, we demonstrated that arachidonic acid (AA) metabolism inhibitors synergize with ICIs in ARID1A-deficient colorectal cancer by enhancing the activity of CD8+ T cells and inhibiting vasculogenic mimicry. Epigenetic analysis using ATAC-seq and ChIP–qPCR revealed that the lack of ARID1A results in reduced levels of PTGS1 and PTGS2, the key enzymes that control the AA pathway. Low PTGS1 and PTGS2 expression generated a reliance on the remaining functionality of the AA pathway in ARID1A-deficient cells. The AA pathway inhibitor aspirin selectively inhibited the growth of ARID1A-deficient colorectal cancer, and aspirin sensitized tumors lacking ARID1A to immunotherapy. Together, these findings suggest that blocking AA metabolism can enhance immune responses against tumors by activating CD8+ T cells and inhibiting vasculogenic mimicry, which synergizes with ICIs to improve treatment of ARID1A-deficient colorectal cancer. Significance: The arachidonic acid pathway is a metabolic vulnerability in ARID1A-deficient colorectal cancer that can be targeted with aspirin to suppress tumor growth and enhance sensitivity to immunotherapy, providing a promising therapeutic strategy.

Background/Aims: Cell surface morphology plays pivotal roles in malignant progression and epithelial-mesenchymal transition (EMT). Previous research demonstrated that microvilli play a key role in cell migration of non-small cell lung cancer (NSCLC). In this study, we report that Forkhead box class O1 (FOXO1) is downregulated in human NSCLC and that silencing of FOXO1 is associated with the invasive stage of tumor progression. Methods: The cell proliferation, migration, and invasion were characterized in vitro, and we tested the expression of the Epithelial-mesenchymal transition (EMT) marker by immunofluorescence staining and also identified the effect of FOXO1 on the microvilli by scanning electron microscopy (SEM). Results: Functional analyses revealed that silencing of FOXO1 resulted in an increase in NSCLC cell proliferation, migration, and invasion; whereas overexpression of FOXO1 significantly inhibited the migration and invasive capability of NSCLC cells in vitro. Furthermore, cell morphology imaging showed that FOXO1 maintained the characteristics of epithelial cells. Immunofluorescence staining and western blotting showed that the E-cadherin level was elevated and Vimentin was reduced by FOXO1 overexpression. Conversely, the E-cadherin level was reduced and Vimentin was elevated in cells silenced for FOXO1. Furthermore, scanning electron microscopy (SEM) showed that FOXO1 overexpression increased the length of the microvilli on the cell surface, whereas FOXO1 silencing significantly reduced their length. Conclusions: FOXO1 is involved in human lung carcinogenesis and may serve as a potential therapeutic target in the migration of human lung cancer.