STG does not associate with psoriasis in the Swedish population

C6orf15 promotes liver metastasis via WNT/β-catenin signalling in colorectal cancer

BACKGROUND

Colon cancer ranks third among global tumours and second in cancer-related mortality, prompting an urgent need to explore new therapeutic targets. C6orf15 is a novel gene that has been reported only in Sjogren's syndrome and systemic lupus erythematosus patients. We found a close correlation between increased C6orf15 expression and the occurrence of colon cancer. The aim of this study was to explore the potential of C6orf15 as a therapeutic target for colorectal cancer.

METHOD

RNA-seq differential expression analysis of the TCGA database was performed using the R package 'limma.' The correlation between target genes and survival as well as tumour analysis was analysed using GEPIA. Western blot and PCR were used to assess C6orf15 expression in colorectal cancer tissue samples. Immunofluorescence and immunohistochemistry were used to assess C6orf15 subcellular localization and tissue expression. The role of C6orf15 in liver metastasis progression was investigated via a mouse spleen infection liver metastasis model. The association of C6orf15 with signalling pathways was assessed using the GSEA-Hallmark database. Immunohistochemistry (IHC), qPCR and western blotting were performed to assess the expression of related mRNAs or proteins. Biological characteristics were evaluated through cell migration assays, MTT assays, and Seahorse XF96 analysis to monitor fatty acid metabolism.

RESULTS

C6orf15 was significantly associated with liver metastasis and survival in CRC patients as determined by the bioinformatic analysis and further verified by immunohistochemistry (IHC), qPCR and western blot results. The upregulation of C6orf15 expression in CRC cells can promote the nuclear translocation of β-catenin and cause an increase in downstream transcription. This leads to changes in the epithelial-mesenchymal transition (EMT) and alterations in fatty acid metabolism, which together promote liver metastasis of CRC.

CONCLUSION

Our study identified C6orf15 as a marker of liver metastasis in CRC. C6orf15 can activate the WNT/β-catenin signalling pathway to promote EMT and fatty acid metabolism in CRC.

C6orf15 acts as a potential novel marker of adverse pathological features and prognosis for colon cancer

OBJECTIVE

To investigate the expression of chromosome 6 open reading frame 15 (C6orf15) in colon cancer and its effects on clinicopathological features and prognosis.

METHODS

Using the transcriptome and clinical data of colon cancer and normal tissues in The Cancer Genome Atlas (TCGA) database, the expression of C6orf15 mRNA in colon cancer samples and its relationship with clinicopathological characteristics and prognosis were explored. The expression level of C6orf15 protein in 23 colon cancer tissues was detected by immunohistochemistry (IHC). The possible mechanism of C6orf15 involved in the occurrence and development of colon cancer was explored by gene set enrichment analysis (GSEA).

RESULTS

Compared with normal tissues, C6orf15 was highly expressed in colon cancer (1.207 ± 0.694 vs 0.276 ± 0.166, t = 8.281, P < 0.01). The expression level of C6orf15 was associated with tumor invasion depth (χ2 = 8.30, P = 0.04), lymph node metastasis (χ2 = 36.97, P < 0.001), distant metastasis (χ2 = 8.69, P = 0.003) and pathological stage (χ2 = 34.17, P < 0.001). High expression of C6orf15 was associated with poor prognosis (χ2 = 6.43, P < 0.05). The results of GSEA showed that C6orf15 promotes the occurrence and development of colon cancer by promoting the ECM receptor interaction pathway, Hedgehog signaling pathway and Wnt signaling pathway. Immunohistochemical results showed that the expression of C6orf15 protein in colon cancer tissues was correlated with the depth of invasion (P = 0.023) and lymph node metastasis (P = 0.048).

CONCLUSION

C6orf15 is highly expressed in colon cancer tissue and is related to adverse pathological features and poor prognosis of colon cancer. It is involved in multiple oncogenic signaling pathways and may serve as a prognostic marker of colon cancer.

HLA-Cw6 and psoriasis

Psoriasis is a multifactorial disease with a strong genetic background. HLA-Cw6 is one of the most strongly associated psoriasis susceptibility alleles. It is repeatedly observed to affect disease course, phenotypic features, severity, comorbidities and treatment outcomes. To the best of our knowledge, the roles of HLA-Cw6 in psoriasis have not yet been thoroughly reviewed. The worldwide frequency of the HLA-Cw6 allele varies greatly, with it being generally higher in white people than in Asians. The allele is associated with type I early-onset psoriasis. Stress, obesity and streptococcal pharyngitis are commonly observed in HLA-Cw6-positive patients. Phenotypically, HLA-Cw6 has been found to be associated with guttate psoriasis. In addition, patients carrying the allele are more likely to have arm, leg and trunk involvement, and the Koebner phenomenon. Patients with psoriatic arthritis with HLA-Cw6 more often have early onset and tend to show cutaneous symptoms before musculoskeletal symptoms. HLA-Cw6-positive patients have been shown in several studies to be more responsive to methotrexate and ustekinumab. However, this difference in ustekinumab efficacy was only moderate in a post-hoc analysis of a pivotal phase III study. HLA-Cw6 positivity also tends to be less frequent in high-need patients who fail conventional therapy. Small studies have also investigated the role of HLA-Cw6 in remission of psoriasis during pregnancy, and with the comorbidities of photosensitivity and atherosclerosis. Given the diverse nature of psoriasis pathogenesis, as well as the difference of HLA-Cw6 positivity in different ethnic groups, more studies are needed to confirm the role of HLA-Cw6 in psoriasis.

The association between non-melanoma skin cancer and a young dimorphic Alu element within the major histocompatibility complex class I genomic region

A non-melanoma skin cancer (NMSC) susceptibility locus within the major histocompatibility complex (MHC) class I region was previously identified telomeric of the HLA-C gene using high-density microsatellite markers. Here, we have extended the previous microsatellite study by using the same DNA samples obtained from 154 NMSC patients and 213 normal controls from the town of Busselton in Western Australia and examined the relationship between five polymorphic Alu insertions (POALINs) within the MHC class I region and their association with NMSC. The genotype distribution of the AluyTF insertion that is located within the NMSC susceptibility region telomeric of the HLA-C gene was significantly increased according to the Fisher's exact test in the NMSC patients, and it was not in Hardy-Weinberg equilibrium in the control group. There was no difference between the cancer patients and controls for the genotypes of the AluyMICB locus within intron 1 of the MICB gene and the other three POALINs (AluyHJ, AluyHG and AluyHF) that are located within the genomic region of the HLA-A, -G and -F gene cluster. The test for significant linkage disequilibrium for 10 pairs of POALIN loci and estimations of two locus POALIN haplotype frequencies also revealed AluyTF differences between the cases and controls. In conclusion, the MHC class I POALIN, AluyTF, that is located within the NMSC susceptibility locus and near the HLA-C gene was strongly associated with NMSC. This finding, using five different polymorphic Alu insertion markers, supports the previous microsatellite association study that one or more genes located in close proximity to the AluyTF insertion has a potential role in NMSC.

Sequence and haplotype analysis supports HLA-C as the psoriasis susceptibility 1 gene

Previous studies have narrowed the interval containing PSORS1, the psoriasis-susceptibility locus in the major histocompatibility complex (MHC), to an approximately 300-kb region containing HLA-C and at least 10 other genes. In an effort to identify the PSORS1 gene, we cloned and completely sequenced this region from both chromosomes of five individuals. Two of the sequenced haplotypes were associated with psoriasis (risk), and the other eight were clearly unassociated (nonrisk). Comparison of sequence of the two risk haplotypes identified a 298-kb region of homology, extending from just telomeric of HLA-B to the HCG22 gene, which was flanked by clearly nonhomologous regions. Similar haplotypes cloned from unrelated individuals had nearly identical sequence. Combinatorial analysis of exonic variations in the known genes of the candidate interval revealed that HCG27, PSORS1C3, OTF3, TCF19, HCR, STG, and HCG22 bore no alleles unique to risk haplotypes among the 10 sequenced haplotypes. SPR1 and SEEK1 both had messenger RNA alleles specific to risk haplotypes, but only HLA-C and CDSN yielded protein alleles unique to risk. The risk alleles of HLA-C and CDSN (HLA-Cw6 and CDSN*TTC) were genotyped in 678 families with early-onset psoriasis; 620 of these families were also typed for 34 microsatellite markers spanning the PSORS1 interval. Recombinant haplotypes retaining HLA-Cw6 but lacking CDSN*TTC were significantly associated with psoriasis, whereas recombinants retaining CDSN*TTC but lacking HLA-Cw6 were not associated, despite good statistical power. By grouping recombinants with similar breakpoints, the most telomeric quarter of the 298-kb candidate interval could be excluded with high confidence. These results strongly suggest that HLA-Cw6 is the PSORS1 risk allele that confers susceptibility to early-onset psoriasis.

Distinct HLA-C/KIR genotype profile associates with guttate psoriasis

Psoriasis is a multifactorial disease with a strong genetic background. It associates strongly to HLA-Cw*0602. HLA-C interacts with killer immunoglobulin-like receptors (KIR) on natural killer (NK) and some natural killer-T (NKT) cells. KIR's function is triggered by specific binding to HLA ligands, which depends on the amino acid 80 of the MHC class I alpha-chain. This permits classifying all HLA-C alleles into two functional groups: asparagine (N80) or lysine (K80) carrying alleles. Psoriasis patients recruited at disease onset were categorized as guttate, vulgaris without arthropathy and vulgaris with arthropathy plus skin lesions. Patients and carefully matched controls were genotyped for position 80 of HLA-C and for KIR. Based on possible HLA/KIR combinations, individuals were classified according to expected NK/NKT cell responses: balanced (B), excess inhibition (EI), excess activation (EA), or undetermined (U). HLA-Cw6 and position 80 genotyping associated strongly to disease, whereas KIR2DS1 associated weakly. Individuals of the U and EI classes were more common among guttate psoriasis patients, which related to HLA-Cw*0602 status. These results suggest that different levels for NK/NKT cell activation thresholds, not only reduction, contribute to immune deregulation in psoriasis. In the guttate phenotype, balanced HLA-C/KIR interactions might be altered by the presence of concomitant streptococcal infections.