SEMAPHORINS and their receptors: focus on the crosstalk between melanoma and hypoxia

Atherosclerotic plaque instability in symptomatic non-significant carotid stenoses

Objective

Carotid endarterectomy for symptomatic carotid stenosis is recommended for patients with >70% stenosis, but not in those with <50%. Because non-significant, low-degree stenoses may still cause strokes, refined risk stratification is necessary, which could be improved by assessing biological features of plaque instability. To challenge risk-stratification based on luminal narrowing, we compared biological features of carotid plaques from symptomatic patients with low-degree (<50%) vs high-degree (>70%) stenosis and explored potential mechanisms behind plaque instability in low-degree stenoses.

Methods

Endarterectomy specimens were taken from symptomatic patients with high-degree (n = 204) and low-degree (n = 34) stenosis, all part of the Biobank of Karolinska Endarterectomies. Patient demographics, image-derived plaque morphology, and gene expression analyses of extracted lesions were used for comparisons. Plaque biology was assessed by transcriptomics using dimensionality reduction, differential gene expression, and gene-set enrichment analyses. Immunohistochemistry was used to study proteins corresponding to upregulated genes.

Results

The demographics of the two groups were statistically similar. Calcification, lipid-rich necrotic core, intraplaque hemorrhage, plaque burden, and fibrous cap thickness were similar in both groups, whereas the sum of lipid-rich necrotic core and intraplaque hemorrhage was higher (P = .033) in the high-degree stenosis group. Dimensionality reduction analysis indicated poor clustering separation of plaque gene expression in low-compared with high-degree stenosis lesions, whereas differential gene expression showed upregulation of hypoxia-inducible factor 3A (log2 fold change, 0.7212; P = .0003), and gene-set enrichment analyses identified pathways related to tissue hypoxia and angiogenesis in low-degree stenoses. Hypoxia-inducible factor 3-alpha protein was associated with smooth muscle cells in neo-vascularized plaque regions.

Conclusions

Plaques from symptomatic patients with non-significant low-degree carotid stenoses showed morphologic and biological features of atherosclerotic plaque instability that were comparable to plaques from patients with high-degree stenoses, emphasizing the need for improved stroke risk stratification for intervention in all patients with symptomatic carotid stenosis irrespective of luminal narrowing. An increased expression of hypoxia-inducible factor 3A in low-degree stenotic lesions suggested mechanisms of plaque instability associated with tissue hypoxia and plaque angiogenesis, but the exact role of hypoxia-inducible factor 3A in this process remains to be determined.

Clinical relevance

Carotid plaques from symptomatic patients with <50% stenosis show morphologic and biological features of plaque instability, comparable to high-degree stenosis, which emphasizes the need for improved stroke risk stratification beyond stenosis severity.

NK/DC crosstalk-modulating antitumor activity via Sema3E/PlexinD1 axis for enhanced cancer immunotherapy

The complex relationship between natural killer (NK) cells and dendritic cells (DCs) within the tumor microenvironment significantly impacts the success of cancer immunotherapy. Recent advancements in cancer treatment have sought to bolster innate and adaptive immune responses through diverse modalities, aiming to tilt the immune equilibrium toward tumor elimination. Optimal antitumor immunity entails a multifaceted interplay involving NK cells, T cells and DCs, orchestrating immune effector functions. Although DC-based vaccines and NK cells' cytotoxic capabilities hold substantial therapeutic potential, their interaction is frequently hindered by immunosuppressive elements such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells. Chemokines and cytokines, such as CXCL12, CCL2, interferons, and interleukins, play crucial roles in modulating NK/DC interactions and enhancing immune responses. This review elucidates the mechanisms underlying NK/DC interaction, emphasizing their pivotal roles in augmenting antitumor immune responses and the impediments posed by tumor-induced immunosuppression. Furthermore, it explores the therapeutic prospects of restoring NK/DC crosstalk, highlighting the significance of molecules like Sema3E/PlexinD1 in this context, offering potential avenues for enhancing the effectiveness of current immunotherapeutic strategies and advancing cancer treatment paradigms. Harnessing the dynamic interplay between NK and DC cells, including the modulation of Sema3E/PlexinD1 signaling, holds promise for developing more potent therapies that harness the immune system's full potential in combating cancer.

Mechanosensory entities and functionality of endothelial cells

The endothelial cells of the blood circulation are exposed to hemodynamic forces, such as cyclic strain, hydrostatic forces, and shear stress caused by the blood fluid's frictional force. Endothelial cells perceive mechanical forces via mechanosensors and thus elicit physiological reactions such as alterations in vessel width. The mechanosensors considered comprise ion channels, structures linked to the plasma membrane, cytoskeletal spectrin scaffold, mechanoreceptors, and junctional proteins. This review focuses on endothelial mechanosensors and how they alter the vascular functions of endothelial cells. The current state of knowledge on the dysregulation of endothelial mechanosensitivity in disease is briefly presented. The interplay in mechanical perception between endothelial cells and vascular smooth muscle cells is briefly outlined. Finally, future research avenues are highlighted, which are necessary to overcome existing limitations.

SEMA3G functions as a novel prognostic biomarker associated with Wnt pathway in clear cell renal cell carcinoma

Renal cell cancer (RCC) is one of the most common cancer, and the incidence of clear cell renal cell cancer rank at the first among multiple subtypes of RCC. Tumor heterogeneity and limited therapies expedite researches and studies on prognostic biomarkers and molecular mechanism. SEMA3G mediates various bimolecular processes but few studies have assessed the influence of SEMA3G on ccRCC. The expression of SEMA3G at mRNA level in ccRCC was analyzed using 4 TCGA datasets. The expression at protein level was verified by immunohistochemistry and western blot. Biological pathway was explored by GSEA and western blot. At both mRNA and protein level, SEMA3G expressed significantly lower in ccRCC tissues compared with normal renal tissues, and the expression was highly associated with clinical stage and pathological grade. Low expression of SEMA3G indicated a poorer overall survival and disease specific survival. Transwell and wound-healing assays showed that overexpressed SEMA3G inhibited the cell motility of renal cancer cells. Upregulated SEMA3G suppressed the invasion and proliferation of both 769-P and 786-O cells. Wnt signaling pathway was tested to work in the interfering of SEMA3G on tumorigenesis and progression of ccRCC. The results provide novel insight into the role of SEMA3G in ccRCC, suggesting the prognostic value and potential suppressor role of SEMA3G.

Sema4D silencing increases the sensitivity of nivolumab to B16-F10 resistant melanoma via inhibiting the PI3K/AKT signaling pathway

Melanoma is a common skin tumor that causes a high rate of mortality, especially in Europe, North America and Oceania. Immunosuppressants such as anti-PD-1 have been used in the treatment of malignant melanoma, however, nearly 60% of patients do not respond to these treatments. Sema4D, also called CD100, is expressed in T cells and tumor tissues. Sema4D and its receptor, Plexin-B1, play crucial roles in the process of immune regulation, angiogenesis, and tumor progression. The role of Sema4D in melanoma with anti-PD-1 resistance is poorly understood. Through a combination of molecular biology techniques and in silico analysis, the role of Sema4D in improving anti-PD-L1 sensitivity in melanoma was explored. The results showed that the expression of Sema4D, Plexin-B1 and PD-L1 was significantly increased in B16-F10R cells. Sema4D knockdown synergizes with anti-PD-1 treatment, cell viability, cell invasion and migration were significantly decreased, while the apoptosis was increased, the growth of tumors on the mice was also inhibited. Mechanistically, bioinformatics analysis revealed that Sema4D is involved in the PI3K/AKT signaling pathway; the downregulation of p-PI3K/PI3K and p-AKT/AKT expression were observed in Sema4D knockdown, therefore, nivolumab resistance is related to Sema4D and Sema4D silencing can improve sensitivity to nivolumab via inhibition of the PI3K/AKT signaling pathway.

SEMA6A/RhoA/YAP axis mediates tumor-stroma interactions and prevents response to dual BRAF/MEK inhibition in BRAF-mutant melanoma

Background

Despite the promise of dual BRAF/MEK inhibition as a therapy for BRAF-mutant (BRAF-mut) melanoma, heterogeneous responses have been observed in patients, thus predictors of benefit from therapy are needed. We have previously identified semaphorin 6A (SEMA6A) as a BRAF-mut-associated protein involved in actin cytoskeleton remodeling. The purpose of the present study is to dissect the role of SEMA6A in the biology of BRAF-mut melanoma, and to explore its predictive potential towards dual BRAF/MEK inhibition.

Methods

SEMA6A expression was assessed by immunohistochemistry in melanoma cohort RECI1 (N = 112) and its prognostic potential was investigated in BRAF-mut melanoma patients from DFCI and TCGA datasets (N = 258). The molecular mechanisms regulated by SEMA6A to sustain tumor aggressiveness and targeted therapy resistance were investigated in vitro by using BRAF-mut and BRAF-wt melanoma cell lines, an inducible SEMA6A silencing cell model and a microenvironment-mimicking fibroblasts-coculturing model. Finally, SEMA6A prediction of benefit from dual BRAF/MEK inhibition was investigated in melanoma cohort RECI2 (N = 14).

Results

Our results indicate higher protein expression of SEMA6A in BRAF-mut compared with BRAF-wt melanoma patients and show that SEMA6A is a prognostic indicator in BRAF-mut melanoma from TCGA and DFCI patients cohorts. In BRAF-mut melanoma cells, SEMA6A coordinates actin cytoskeleton remodeling by the RhoA-dependent activation of YAP and dual BRAF/MEK inhibition by dabrafenib+trametinib induces SEMA6A/RhoA/YAP axis. In microenvironment-mimicking co-culture condition, fibroblasts confer to melanoma cells a proliferative stimulus and protect them from targeted therapies, whereas SEMA6A depletion rescues the efficacy of dual BRAF/MEK inhibition. Finally, in BRAF-mut melanoma patients treated with dabrafenib+trametinib, high SEMA6A predicts shorter recurrence-free interval.

Conclusions

Overall, our results indicate that SEMA6A contributes to microenvironment-coordinated evasion of melanoma cells from dual BRAF/MEK inhibition and it might be a good candidate predictor of short-term benefit from dual BRAF/MEK inhibition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02354-w.