ABSTRACT
Reactive oxygen species formed within the mammalian cell can produce 8-oxo-7,8-dihydroguanine (8-oxoG) in mRNA, which can cause base mispairing during gene expression. Here we found that administration of 8-oxoGTP in MTH1-knockdown cells results in increased 8-oxoG content in mRNA. Under this condition, an amber mutation of the reporter luciferase is suppressed. Using second-generation sequencing techniques, we found that U-to-G changes at preassigned sites of the luciferase transcript increased when 8-oxoGTP was supplied. In addition, an increased level of 8-oxoG content in RNA induced the accumulation of aggregable amyloid ß peptides in cells expressing amyloid precursor protein. Our findings indicate that 8-oxoG accumulation in mRNA can alter protein synthesis in mammalian cells. Further work is required to assess the significance of these findings under normal physiological conditions.
Subject(s)
Guanine/analogs & derivatives , Mutagenesis/genetics , Protein Biosynthesis/genetics , Transcription, Genetic/genetics , Amyloid beta-Peptides/genetics , Anticodon/genetics , Base Pairing , Codon, Nonsense , DNA Repair Enzymes/antagonists & inhibitors , DNA Repair Enzymes/genetics , Gene Knockdown Techniques , Genes, Reporter , Guanine/chemistry , HeLa Cells , Humans , Luciferases/genetics , Phosphoric Monoester Hydrolases/antagonists & inhibitors , Phosphoric Monoester Hydrolases/genetics , RNA Interference , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , RNA, Small Interfering/genetics , Reactive Oxygen SpeciesABSTRACT
The heterogeneous nature of tumour microenvironment (TME) underlying diverse treatment responses remains unclear in nasopharyngeal carcinoma (NPC). Here, we profile 176,447 cells from 10 NPC tumour-blood pairs, using single-cell transcriptome coupled with T cell receptor sequencing. Our analyses reveal 53 cell subtypes, including tumour-infiltrating CD8+ T, regulatory T (Treg), and dendritic cells (DCs), as well as malignant cells with different Epstein-Barr virus infection status. Trajectory analyses reveal exhausted CD8+ T and immune-suppressive TNFRSF4+ Treg cells in tumours might derive from peripheral CX3CR1+CD8+ T and naïve Treg cells, respectively. Moreover, we identify immune-regulatory and tolerogenic LAMP3+ DCs. Noteworthily, we observe intensive inter-cell interactions among LAMP3+ DCs, Treg, exhausted CD8+ T, and malignant cells, suggesting potential cross-talks to foster an immune-suppressive niche for the TME. Collectively, our study uncovers the heterogeneity and interacting molecules of the TME in NPC at single-cell resolution, which provide insights into the mechanisms underlying NPC progression and the development of precise therapies for NPC.
Subject(s)
Head and Neck Neoplasms/immunology , Head and Neck Neoplasms/metabolism , Nasopharyngeal Carcinoma/immunology , Nasopharyngeal Carcinoma/metabolism , Tumor Microenvironment/physiology , CD8-Positive T-Lymphocytes/enzymology , CD8-Positive T-Lymphocytes/metabolism , Cells, Cultured , Dendritic Cells/immunology , Dendritic Cells/metabolism , High-Throughput Nucleotide Sequencing , Humans , Male , T-Lymphocytes, Regulatory/immunology , T-Lymphocytes, Regulatory/metabolism , Tumor Microenvironment/immunologyABSTRACT
Esophageal squamous cell carcinoma (ESCC) is one of the deadliest cancers. We performed exome sequencing on 113 tumor-normal pairs, yielding a mean of 82 non-silent mutations per tumor, and 8 cell lines. The mutational profile of ESCC closely resembles those of squamous cell carcinomas of other tissues but differs from that of esophageal adenocarcinoma. Genes involved in cell cycle and apoptosis regulation were mutated in 99% of cases by somatic alterations of TP53 (93%), CCND1 (33%), CDKN2A (20%), NFE2L2 (10%) and RB1 (9%). Histone modifier genes were frequently mutated, including KMT2D (also called MLL2; 19%), KMT2C (MLL3; 6%), KDM6A (7%), EP300 (10%) and CREBBP (6%). EP300 mutations were associated with poor survival. The Hippo and Notch pathways were dysregulated by mutations in FAT1, FAT2, FAT3 or FAT4 (27%) or AJUBA (JUB; 7%) and NOTCH1, NOTCH2 or NOTCH3 (22%) or FBXW7 (5%), respectively. These results define the mutational landscape of ESCC and highlight mutations in epigenetic modulators with prognostic and potentially therapeutic implications.