Relation of immune semaphorin/plexin signaling to carcinogenesis

Canine Somatic Mutations from Whole-Exome Sequencing of B-Cell Lymphomas in Six Canine Breeds-A Preliminary Study

Canine lymphoma (CL) is one of the most common malignant tumors in dogs. The cause of CL remains unclear. Genetic mutations that have been suggested as possible causes of CL are not fully understood. Whole-exome sequencing (WES) is a time- and cost-effective method for detecting genetic variants targeting only the protein-coding regions (exons) that are part of the entire genome region. A total of eight patients with B-cell lymphomas were recruited, and WES analysis was performed on whole blood and lymph node aspirate samples from each patient. A total of 17 somatic variants (GOLIM4, ITM2B, STN1, UNC79, PLEKHG4, BRF1, ENSCAFG00845007156, SEMA6B, DSC1, TNFAIP1, MYLK3, WAPL, ADORA2B, LOXHD1, GP6, AZIN1, and NCSTN) with moderate to high impact were identified by WES analysis. Through a Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of 17 genes with somatic mutations, a total of 16 pathways were identified. Overall, the somatic mutations identified in this study suggest novel candidate mutations for CL, and further studies are needed to confirm the role of these mutations.

SEMA6B Overexpression Predicts Poor Prognosis and Correlates With the Tumor Immunosuppressive Microenvironment in Colorectal Cancer

Background: Semaphorin 6b (SEMA6B) is a member of the semaphorin axon-guidance family and has been demonstrated to both induce and inhibit tumor progression. However, the role of SEMA6B in colorectal cancer (CRC) has remained unclear. This study sought to explore the promising prognostic biomarker for CRC and to understand the expression pattern, clinical significance, immune effects, and biological functions of SEMA6B.

Methods: SEMA6B expression in CRC was evaluated via multiple gene and protein expression databases and we identified its prognostic value through The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Correlations between SEMA6B expression and components of the tumor immune microenvironment were analyzed by packages implemented in R, Tumor Immune Estimation Resource (TIMER), Gene Expression Profiling Interactive Analysis (GEPIA), and Tumor-Immune System Interactions database (TISIDB). RNA interference was performed to silence the expression of SEMA6B to explore its biological roles in the colon cancer cell lines HCT116 and LoVo.

Results: The messenger RNA (mRNA) level of SEMA6B and the protein expression were higher in CRC tissues than adjacent normal tissues from multiple CRC datasets. High SEMA6B expression was significantly associated with dismal survival. Multivariate Cox regression analysis demonstrated that SEMA6B was an independent prognostic factor for progression-free survival (PFS). The nomogram showed a favorable predictive ability in PFS. Functional enrichment analysis and the Estimation of STromal and Immune cells in MAlignant Tumor tissues using Expression data (ESTIMATE) algorithm revealed that the gene cluster associated with the high SEMA6B group were prominently involved in immune responses and inflammatory activities. Notably, SEMA6B expression was positively correlated with infiltrating levels of CD4⁺ T cells, macrophages, myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), neutrophils, and dendritic cells. Moreover, SEMA6B expression displayed strong correlations with diverse marker sets of immunosuppressive cells in CRC. Integrative analysis revealed that immunosuppressive molecules and immune checkpoints were markedly upregulated in CRC samples with high SEMA6B expression. Furthermore, knockdown of SMEA6B in colon cancer cells significantly inhibited cell proliferation, migration, invasion and reduced the mRNA levels of immunosuppressive molecules.

Conclusion: Our findings provide evidence that high SEMA6B expression correlated with adverse prognosis and the tumor immunosuppressive microenvironment in CRC patients. Therefore, SEMA6B may serve as a novel prognostic biomarker for CRC, which offers further insights into developing CRC-targeted immunotherapies.

Suppression of tumor-derived Semaphorin 7A and genetic ablation of host-derived Semaphorin 7A impairs tumor progression in a murine model of advanced breast carcinoma

Solid tumors can generate a plethora of neurogenesis-related molecules that enhance their growth and metastasis. Among them, we have identified axonal guidance molecule Semaphorin 7A (SEMA7A) in breast cancer. The goal of this study was to determine the therapeutic effect of suppressing SEMA7A levels in the 4T1 murine model of advanced breast carcinoma. We used anti-SEMA7A short hairpin RNA (shRNA) to gene silence SEMA7A in 4T1 mammary tumor cells. When implanted into the mammary fat pads of syngeneic mice, SEMA7A shRNA-expressing 4T1 tumors exhibited decreased growth rates, deferred metastasis and reduced mortality. In vitro, SEMA7A shRNA-expressing 4T1 cells had weakened proliferative, migratory and invasive abilities, and decreased levels of mesenchymal factors. Atomic force microscopy studies showed that SEMA7A shRNA-expressing 4T1 cells had an increase in cell stiffness that corresponded with their decreased malignant potential. Genetic ablation of host-derived SEMA7A further enhanced the antitumor effects of SEMA7A shRNA gene silencing in 4T1 cells. Our preclinical findings demonstrate a critical role for SEMA7A in mediating mammary tumor progression.

Old friends, new story: The role of Slit2C signaling through PlexinA1

Growth cone guidance is driven by attractive and repulsive signaling cues. Until recently, repulsive signaling by semaphorins was thought to be mediated through Plexin receptors, whereas Slits-induced repulsion was solely mediated through Robo receptors. In a recent report published in Nature Neuroscience, Celine Delloye-Bourgeois and colleagues (2015) combined phenotypic analyses of transgenic mouse lines and in vitro biochemical experiments to identify PlexinA1 as a novel receptor for Slits. Strikingly, they uncovered for the very first time that the Slit2C-terminal fragment possesses some unique biological activity as binding partner for PlexinA1. Even more excitingly, the signaling cascade triggered by SlitC binding to PlexinA1 mediates growth cone collapse of commissural axons both in vivo and ex vivo and nicely complements Robo-Slit signaling in the developing spinal cord midline to prevent midline recrossing.

Genetic aspects of anti-neutrophil cytoplasmic antibody-associated vasculitis

The genetics of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a complex area of investigation because of the low frequency of AAVs, the rarity of familial cases and the complexity of disease phenotypes. However, recent studies have been able to gather significant numbers of patients, and multicentre collaborative efforts have allowed the performance of two genome-wide association studies (GWASs). Genetic association studies based on candidate gene approaches and the two GWASs have greatly contributed to our current understanding of the genetic basis of AAV. The central role of autoimmunity has been confirmed by the significant association with HLA polymorphisms; interestingly, the three main AAV subtypes are associated with distinct HLA variants, i.e. granulomatosis with polyangiitis (Wegener's GPA) with HLA-DP1, microscopic polyangiitis with HLA-DQ and eosinophilic GPA (Churg-Strauss) with HLA-DRB4. GWASs also revealed that polymorphic variants of genes encoding proteinase 3 (PR3), the predominant antigenic target of ANCA in GPA, and its main inhibitor, alpha-1 antitrypsin, are highly associated with GPA and, even more significantly, with PR3-ANCA positivity (regardless of the clinical diagnosis); this emphasizes the central pathogenic role of PR3 and humoral autoimmunity in PR3-ANCA positive vasculitis. Finally, candidate gene approach studies have shown associations with other variants involved in autoimmunity, such as those belonging to the CTLA-4 and PTPN22 genes, although these findings warrant replication in larger studies. Additional studies are underway to better characterize disease associations within the AAV spectrum, which could provide new pathogenetic clues and possibly new treatment targets.