Critical Role for the Oct-2/OCA-B Partnership in Ig-Secreting Cells

Novel immune subtypes identification of HER2-positive breast cancer based on immunogenomic landscape

HER2 positive BC is heterogeneous. But few studies discussed the classification of HER2-positive BC based on immune-related signatures. Using three publicly BC genomics datasets, we classified HER2 positive BC based on 33 immune-related signatures and used unsupervised machine learning methods to predict and perform the classification. We grouped three HER2-positive BC subtypes that we called Immune-High (IM-H), Immune-Medium (IM-M), and Immune-Low (IM-L), and manifested this categorization was predictable, duplicable and reliable by analyzing another dataset. Compared to other subtypes, IM-H had a higher immune cell infiltration level and stronger anti-tumor immune activities, as well as better clinical survival outcome. Besides these signatures, there were some cancer-related pathways which were hyperactivated in IM-H, including cytokine-cytokine receptor interactions, antigen processing and presentation pathways, natural killer cell-mediated cytotoxicity, Th1 and Th2 cell differentiation, chemokine signaling pathway, Th17 cell differentiation, B and T cell receptor signaling, NF-kappa B signaling, PD-L1 expression and PD-1 checkpoint pathway in cancer, TNF signaling, IL-17 signaling, NOD-like receptor signaling and Toll-like receptor signaling. By contrast, IM-L showed depressed immune-related signatures and enhanced activation of lycosylphosphatidylinositol-anchor biosynthesis and mismatch repair. Moreover, we discovered a gene co-expression network focused on eight transcription factor genes (EOMES, TBX21, GFI1, IRF4, POU2AF1, CIITA, FOXP3 and TOX) and one tumor suppress gene (PRF1), which were closely related with tumor immune. We identified three HER2-positive BC subtypes based on immune-related signatures, which had potential clinical implications and promoted the optimal stratification of HER2-positive BC responsive to immunotherapy.

rs1944919 on chromosome 11q23.1 and its effector genes COLCA1/COLCA2 confer susceptibility to primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic, progressive cholestatic liver disease in which intrahepatic bile ducts are destroyed by an autoimmune reaction. Our previous genome-wide association study (GWAS) identified chromosome 11q23.1 as a susceptibility gene locus for PBC in the Japanese population. Here, high-density association mapping based on single nucleotide polymorphism (SNP) imputation and in silico/in vitro functional analyses identified rs1944919 as the primary functional variant. Expression-quantitative trait loci analyses showed that the PBC susceptibility allele of rs1944919 was significantly associated with increased COLCA1/COLCA2 expression levels. Additionally, the effects of rs1944919 on COLCA1/COLCA2 expression levels were confirmed using genotype knock-in versions of cell lines constructed using the CRISPR/Cas9 system and differed between rs1944919-G/G clones and -T/T clones. To our knowledge, this is the first study to demonstrate the contribution of COLCA1/COLCA2 to PBC susceptibility.

Germline variation in the 3'-untranslated region of the POU2AF1 gene is associated with susceptibility to lymphoma

Genetic variations in certain genes may alter the susceptibility to lymphoma. We searched electronic databases and selected candidate single-nucleotide polymorphisms (SNPs) located within 3'-untranslated regions (3'-UTRs) that might affect miRNA-binding ability in the 50 most dysregulated genes in lymphoma for further study. We found that rs1042752-located in the 3'-UTR of POU2AF1, which plays a vital role in lymphomagenesis-was significantly associated with lymphoma risk in a case-control study with 793 patients and 939 controls. Compared with individuals with the rs1042752TT genotype, those with the rs1042752CC genotype had a higher risk of lymphoma (OR = 2.14, 95% CI: 1.55-2.95, P < 0.001), even in stratified analysis for non-Hodgkin lymphoma (OR = 4.58, 95% CI: 2.38-8.81, P < 0.001), B-cell lymphoma (OR = 4.89, 95% CI: 2.46-9.73, P < 0.001), T-cell lymphoma (OR = 4.20, 95% CI: 1.76-10.05, P = 0.001), and Hodgkin lymphoma (OR = 3.62, 95% CI: 1.25-10.46, P = 0.018). Similar results were also observed in a recessive genetic model. Database findings suggested that rs1042752 might affect the interaction of POU2AF1 mRNA with hsa-miR-633. Functional assays confirmed that rs1042752C altered the binding site of hsa-miR-633 and increased POU2AF1 expression in Ramos, HuT 102, and Jurkat E6-1 cell lines. These findings demonstrate for the first time that functional polymorphism in the 3'-UTR of POU2AF1 is associated with susceptibility, and that SNP interaction with hsa-miR-633 affects gene expression and increases the risk of lymphoma.

Role of defective Oct-2 and OCA-B expression in immunoglobulin production and Kaposi's sarcoma-associated herpesvirus lytic reactivation in primary effusion lymphoma

Primary effusion lymphoma (PEL) is a distinct type of B-cell non-Hodgkin lymphoma characterized by the presence of Kaposi's sarcoma-associated herpesvirus (KSHV/human herpesvirus 8). Despite having a genotype and gene expression signature of highly differentiated B cells, PEL does not usually express surface or cytoplasmic immunoglobulin (Ig). We show the lack of Oct-2 and OCA-B transcription factors to be responsible, at least in part, for this defect in Ig production. Like Ig genes, ORF50, the key regulator of the switch from latency to lytic reactivation, contains an octamer motif within its promoter. We therefore examined the impact of Oct-2 and OCA-B on ORF50 activation. The binding of Oct-1 to the ORF50 promoter has been shown to significantly enhance ORF50 transactivation. We found that Oct-2, on the other hand, inhibited ORF50 expression and consequently lytic reactivation by competing with Oct-1 for the octamer motif in the ORF50 promoter. Our data suggest that Oct-2 downregulation in infected cells would be favorable to KSHV in allowing for efficient viral reactivation.

Contrasting mode of evolution between the MHC class I genomic region and class II region in the three-spined stickleback (Gasterosteus aculeatus L.; Gasterosteidae: Teleostei)

Major histocompatibility complex (MHC) class I molecules display peptides on cell surfaces for subsequent T-cell recognition and are involved in the immune response against intracellular pathogens. In this study, a BAC library was created from a single three-spined stickleback and screened for clones containing MHC class I genes. In a 163.2-kb genomic sequence segment of a single clone, we identified three MHC class I genes in the same transcriptional orientation. Two class I genes are potentially expressed and functional. In one class I gene, the transmembrane region is missing and could therefore present a pseudogene. Alternatively, it presents a functional gene that encodes a soluble MHC class Ib molecule. Despite genomic similarities to the MHC class II region, which is characterized by interlocus recombination, we did not find any evidence for this kind of recombination in the class I genes. It thus seems that interlocus recombination may play a rather minor role in generating class I diversity in stickleback and that the class I region displays a higher genomic stability (i.e., lower local recombination rate). In addition, two non-MHC genes (Oct-2 beta and Na(+),K(+)-ATPasealpha3) have been identified in the analyzed class I region. The Oct-2 beta gene is a transcription factor that is expressed primarily in B lymphocytes, in activated T-cells, and in neuronal cells. The Na(+),K(+)-ATPasealpha3 gene is primarily expressed in the brain and heart and mediates catalytic activities. Both genes are located on the same linkage group together with the MHC class I genes in the zebra fish. In humans, however, homologues of Oct-2 beta and ATPasealpha3 lie outside the MHC region, which indicates that the concentration of immune genes found in mammalian genomes is a derived state.

Epigenetic processes play a major role in B-cell-specific gene silencing in classical Hodgkin lymphoma

Many B-lineage-specific genes are down-regulated in Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (cHL). We investigated the involvement of epigenetic modifications in gene silencing in cHL cell lines and in microdissected primary HRS cells. We assessed the expression and methylation status of CD19, CD20, CD79B, SYK, PU.1, BOB.1/OBF.1, BCMA, and LCK, all of which are typically down-regulated in cHL. We could reactivate gene expression in cHL cell lines with the DNA demethylating agent 5-aza-deoxycytidine (5-aza-dC). Using methylation-specific polymerase chain reaction (MSP), bisulfite genomic sequencing, and digestion with methylation-sensitive endonuclease followed by polymerase chain reaction (PCR), we determined the methylation status of promoter regions of PU.1, BOB.1/OBF.1, CD19, SYK, and CD79B. Down-regulation of transcription typically correlated with hypermethylation. Using bisulfite genomic sequencing we found that in microdissected HRS cells of primary cHL SYK, BOB.1/OBF.1, and CD79B promoters were also hypermethylated. Ectopic expression of both Oct2 and PU.1 in a cHL cell line potentiated endogenous PU.1 and SYK expression after 5-aza-dC treatment. These observations indicate that silencing of the B-cell-specific genes in cHL may be the consequence of a compromised regulatory network where down-regulation of a few master transcription factors results in silencing of numerous genes.