Recently, endoplasmic reticulum (ER) stress has been shown to influence tumor progression and immune cell function in the tumor microenvironment (TME). However, the underlying role of ER stress-related gene patterns in colorectal cancer (CRC) development remains unclear. We analyzed the ER stress-related gene patterns in 884 patients with CRC from the Gene Expression Omnibus database and evaluated the cell-infiltrating patterns in the TME. Two ER stress-related patterns were identified in patients with CRC that had distinct cell-infiltrating patterns in the TME and clinical characteristics. A risk score and nomogram based on 14 screened prognosis-correlated genes was built and validated to predict patient survival. Patients with a higher risk score were shown to have an unfavorable prognosis, and the risk score was associated with cell infiltration and drug sensitivity. Furthermore, spatial transcriptomics data were utilized to explore ER stress-related gene patterns in CRC tissues, and it was shown that ER stress phenotype involves in the formation of the immunosuppressive TME. This study demonstrated that ER stress-related gene patterns play a role in influencing the TME and predicting prognosis. These analyses of ER stress in the TME of CRC might deepen our understanding of CRC progression and immune escape and provide novel insights into therapeutic strategies.

Background: Emerging evidence suggested that the gut microbiota associated with the development of immune-related adverse effects (irAEs) among cancer patients receiving immune checkpoint inhibitors (ICIs), but their roles remain largely unknown, and the causal associations are yet to be clarified. Methods: Bi-directional two-sample Mendelian randomization (MR) approach was employed to examine the potential causal relationship between the gut microbiome and irAEs (high-grade irAEs and all-grade irAEs). Instrumental variables (IVs) for gut microbiota were retrieved from the MiBioGen consortium (18,340 participants). GWAS summary data for instrument-outcome associations were gathered from an ICIs-treated cohort with 1,751 cancer patients. Inverse variance weighted (IVW), MR PRESSO, maximum likelihood (ML), weighted median, weighted mode, and cML-MA-BIC were used in the MR analysis. Reverse MR analysis was performed on the identified bacteria that were causally associated with irAEs. Results: Fourteen gut bacterial taxa identified by IVW and MR PRESSO were causally associated with irAEs, among which Lachnospiraceae was shown to increase the risk of both high-grade and all-grade irAEs. Akkermansia, Verrucomicrobiaceae, and Anaerostipes were found to exert protective roles in high-grade irAEs. Nevertheless, Ruminiclostridium6, Coprococcus3, Collinsella, and Eubacterium (fissicatena group) predispose to the development of high-grade irAEs. For all-grade irAEs, RuminococcaceaeUCG004, and DefluviitaleaceaeUCG011 were shown to have protective effects. While on the contrary, Porphyromonadaceae, Roseburia, Eubacterium (brachy group), and Peptococcus were associated with an elevated risk of all-grade irAEs. Conclusion: Our MR analysis found that Lachnospiraceae and Akkermansia et al. were causally associated with the development of irAEs, which warrants further investigation.

Background SLC5A7 (solute carrier family 5 member 7), also known as choline transporter 1 (CHT1), is downregulated in colorectal cancer (CRC) and functions as a tumor suppressor. However, the mechanisms underlying the inactivation of SLC5A7 in CRC remain to be elucidated. Results In the present study, two broad-spectrum demethylation agents (azacitidine and decitabine) employed to treat CRC cells significantly upregulated SLC5A7 expression. Further results based on the CRC cohort and TCGA database indicated that SLC5A7 promoter methylation inversely correlated with SLC5A7 expression, and the status of SLC5A7 promotor methylation showed a promising prognostic value for patients with CRC. Next, the dCas9-multiGCN4/scFv-TET1CD-based precision demethylation system was constructed, which could significantly and specifically promote SLC5A7 expression in CRC cells through sgRNA targeting the SLC5A7 promoter. Both in vitro and in vivo experiments demonstrated that targeted demethylation of SLC5A7 by dCas9-multiGCN4/scFv-TET1CD-sgSLC5A7 inhibited tumor growth by stabilizing p53 and regulating downstream targets. Conclusions Collectively, DNA promoter methylation caused inactivation of SLC5A7 in CRC, and targeted demethylation of SLC5A7 might be a therapeutic target for CRC and other cancers.