Cholesterol induction in CD8+ T cell exhaustion in colorectal cancer via the regulation of endoplasmic reticulum-mitochondria contact sites.

BACKGROUND: Hypercholesterolemia is one of the risk factors for colorectal cancer (CRC). Cholesterol can participate in the regulation of human T cell function and affect the occurrence and development of CRC. OBJECTIVE: To elucidate the pathogenesis of CRC immune escape mediated by CD8+ T cell exhaustion induced by cholesterol. METHODS: CRC samples (n = 217) and healthy individuals (n = 98) were recruited to analyze the relationship between peripheral blood cholesterol levels and the clinical features of CRC. An animal model of CRC with hypercholesterolemia was established. Intraperitoneal intervention with endoplasmic reticulum stress (ERS) inhibitors in hypercholesterolemic CRC mice was performed. CD69, PD1, TIM-3, and CTLA-4 on CD8+ T cells of spleens from C57BL/6 J mice were detected by flow cytometry. CD8+ T cells were cocultured with MC38 cells (mouse colon cancer cell line). The proliferation, apoptosis, migration and invasive ability of MC38 cells were detected by CCK-8 assay, Annexin-V APC/7-AAD double staining, scratch assay and transwell assay, respectively. Transmission electron microscopy was used to observe the ER structure of CD8+ T cells. Western blotting was used to detect the expression of ERS and mitophagy-related proteins. Mitochondrial function and energy metabolism were measured. Immunoprecipitation was used to detect the interaction of endoplasmic reticulum-mitochondria contact site (ERMC) proteins. Immunofluorescence colocalization was used to detect the expression and intracellular localization of ERMC-related molecules. RESULTS: Peripheral blood cholesterol-related indices, including Tc, low density lipoproteins (LDL) and Apo(a), were all increased, and high density lipoprotein (HDL) was decreased in CRCs. The proliferation, migration and invasion abilities of MC38 cells were enhanced, and the proportion of tumor cell apoptosis was decreased in the high cholesterol group. The expression of IL-2 and TNF-α was decreased, while IFN-γ was increased in the high cholesterol group. It indicated high cholesterol could induce exhaustion of CD8+ T cells, leading to CRC immune escape. Hypercholesterolemia damaged the ER structure of CD8+ T cells and increased the expression of ER stress molecules (CHOP and GRP78), lead to CD8+ T cell exhaustion. The expression of mitophagy-related proteins (BNIP3, PINK and Parkin) in exhausted CD8+ T cells increased at high cholesterol levels, causing mitochondrial energy disturbance. High cholesterol enhanced the colocalization of Fis1/Bap31, MFN2/cox4/HSP90B1, VAPB/PTPIP51, VDAC1/IPR3/GRP75 in ERMCs, indicated that high cholesterol promoted the intermolecular interaction between ER and mitochondrial membranes in CD8+ T cells. CONCLUSION: High cholesterol regulated the ERS-ERMC-mitophagy axis to induce the exhaustion of CD8+ T cells in CRC.

Analysis of T lymphocyte-related biomarkers in pancreatic cancer.

BACKGROUND: Pancreatic cancer remains one of the most lethal cancers. OBJECTIVE: This study aimed to analyze T cell-related biomarkers and their molecular network in pancreatic cancer. METHODS: RNAseq sequencing data and clinical data of pancreatic cancer were obtained from TCGA database. The STromal and Immune cells in MAlignant Tumours using Expression data (ESTIMATE) algorithm was used to screen the DEGs related to the tumor immune cells. The pearson correlation analysis were used to analyze the relationships between DEGs and T cells. Additionally, the T cell-related DEGs were subjected to protein-protein interaction, competing endogenous RNA (ceRNA), and chemical small molecule-target network construction. Furthermore, the prognosis-associated DEGs were screened. RESULTS: A total of 412 stromal score-associated and 312 immune score-associated DEGs were obtained. From these DEGs, 50 CD4+ T cell-related genes and 13 CD8+ T cell-related genes were selected. The PPI networks associated with immune cell-related genes were constructed and found that CD22, SELL, and OLR1 had higher degrees in the PPI network. The number of ceRNA regulatory relation pairs obtained from CD4+ T cells and CD8+ T cells were 59 and 48, respectively. Additionally, both CD4+ T cell- and CD8+ T cell-related genes predicted 29 small molecules. CXCL9 and GIMAP7 were screened out from CD4+ T cell-related genes, which were related with the survival of pancreatic cancer. CONCLUSION: We mapped T cell-related gene profile in pancreatic cancer and constructed their potential regulatory network.

Effects of postoperative adjuvant chemotherapy and palliative chemotherapy on the gut microbiome in colorectal cancer.

BACKGROUND: The gut microbiome changes are related to the colorectal cancer (CRC). Chemotherapy is one of the main treatment methods for CRC. PURPOSE: To explore the effect of chemotherapy on the gut bacteria and fungi in CRC. METHODS: Total of 11 advanced CRC patients treated with the FOLFIRI regimen, 15 postoperative CRC patients treated with the XELOX regimen, and corresponding CRC patients without surgery and chemotherapy were recruited. The 16S ribosomal RNA and ITS sequences were sequenced, and bioinformatics analysis was executed to screen for the distinctive gut microbiome. RESULTS: The abundances of Veillonella, Humicola, Tremellomycetes and Malassezia were increased in postoperative CRC patients treated with the XELOX regimen. The abundances of Faecalibacterium, Clostridiales, phascolarctobacterium, Humicola and Rhodotorula were decreased, and the abundances of Candida, Magnusiomyces, Tremellomycetes, Dipodascaceae, Saccharomycetales, Malassezia and Lentinula were increased in advanced CRC patients treated with the FOLFIRI regimen. The abundances of Humicola, Rhodotorula, and Magnusiomyces were decreased, and the abundances of Candida, Tremellomycetes, Dipodascaceae, Saccharomycetales, Malassezia and Lentinula were increased in advanced CRC patients treated with the FOLFIRI regimen combined with cetuximab compared with those treated with the FOLFIRI regimen alone. CONCLUSIONS: The community structure of gut bacteria and fungi changes in chemotherapy on CRCs.