Dynamic change in Siglec-15 expression in peritumoral macrophages confers an immunosuppressive microenvironment and poor outcome in glioma

Expression of SIGLEC15 correlates with tumor immune infiltration, molecular subtypes, and breast cancer progression

Breast cancer (BRCA) is among the most prevalent cancers and is responsible for numerous patient fatalities. Immunotherapy has emerged as a promising approach to cancer treatment. Recent studies have identified Siglec-15 as a novel immune target that plays a crucial role in tumor immune evasion, suggesting its potential significance in BRCA. We utilized databases such as TCGA to investigate the relevance of SIGLEC15 in BRCA. The expression of the Siglec-15 protein in 74 breast cancer patients was detected using immunohistochemistry, and its association with clinicopathological features and overall survival was evaluated. The co-expression of Siglec-15, CD68, CK, and CD8 in BRCA tissues was identified through multiplex immunofluorescence staining. Our study revealed that SIGLEC15 expression in BRCA was significantly elevated compared to adjacent normal tissues. Kaplan-Meier analysis identified SIGLEC15 as a prognostic protective factor. According to the receiver operating characteristic curve analysis, SIGLEC15 could predict the luminal subtype of BRCA. Enrichment analysis demonstrated that SIGLEC15 involves various biological pathways, including immunity, metabolism, tumors, and infectious diseases. Correlation analysis revealed an association between SIGLEC15 expression and immune infiltration in BRCA. We also confirmed that the Siglec-15 protein is expressed in cancer cells, tumor-infiltrating T cells, and macrophages in BRCA tissues, significantly higher levels than in normal breast tissues. Consequently, SIGLEC15 correlates with tumor immune infiltration, molecular subtypes, and BRCA progression and prognosis. However, further research is required to elucidate the role of SIGLEC15 in breast cancer.

Siglec-15 expression in diffuse gliomas and its correlation with MRI morphologic features and apparent diffusion coefficient

BACKGROUND

Sialic acid-binding immunoglobulin-like lectin 15 (Siglec-15) enhances tumor immune escape and leads to tumor growth.

PURPOSE

To investigate the expression of Siglec-15 in diffuse gliomas and its correlation with tumor magnetic resonance imaging (MRI) features.

MATERIAL AND METHODS

This study included 57 patients with gliomas. Morphological MRI features, including the largest tumor diameter, enhancement category, location, calcification, cysts, and hemorrhage, were visually rated. Apparent diffusion coefficient (ADC) values were calculated in tumor region. MRI morphologic features and ADC were compared between patients with positive and negative Siglec-15 expression. Receiver operating characteristic (ROC) curves were further constructed to assess the diagnostic performance.

RESULTS

Siglec-15 was expressed in immunocytes, such as macrophages in the peritumoral area. Siglec-15 expression was positive in 20/57 (35.09%) patients, with higher expression in patients with IDH-mutant gliomas and lower grade gliomas. The tumor diameter was significantly smaller in patients with positive Siglec-15 expression than in those with negative expression for all patients (P = 0.017) and for patients with IDH-mutant gliomas (P = 0.020). Moreover, ADC values of the tumor were significantly higher in patients with positive Siglec-15 expression than in those with negative expression for all patients (P = 0.027). The areas under the ROC curve (AUCs) of the diameter and ADC were 0.702 and 0.686, respectively. A combination of these two parameters generated an improved AUC of 0.762.

CONCLUSION

Siglec-15 was expressed in immunocytes such as macrophages in the peritumoral area, with a positive rate of 35.09%. Positive Siglec-15 expression in diffuse gliomas was correlated with smaller tumor size and higher ADC values.

Pyroptotic-Spatiotemporally Selective Delivery of siRNA against Pyroptosis and Autoimmune Diseases

Small-interfering RNAs (siRNAs) offer promising prospects for treating pyroptosis-related autoimmune diseases. However, poor stability and off-target effects during in vivo transportation hinder their practical clinical applications. Precision delivery and adaptive release of siRNAs into inflamed tissues and immune cells could unleash their full therapeutic potential. This study establishes a pyroptotic-spatiotemporally selective siRNA delivery system (PMRC@siGSDME) that selectively targets inflammatory tissues, responds to pyroptosis, and exhibits remarkable therapeutic efficacy against various autoimmune diseases. Novel hybrid nanovesicles (NVs) are designed as a combination of pyroptotic macrophage membranes (PMs) and R8-cardiolipin-containing nanovesicles (RC-NVs). Evidence provides that PM-derived proteins involved in cell-cell interactions and membrane trafficking may contribute to the specificity of NVs to inflammatory tissue. In addition, cardiolipin anchored in the hybrid NVs increases its affinity for activated gasdermin E (GSDME) and achieves pyroptosis-adaptive release of siGSDME for the spatiotemporally selective suppression of immune responses. More importantly, PMRC@siGSDME displays significant anti-inflammatory and therapeutic effects in multiple mouse autoimmune disease models, including arthritis and inflammatory bowel disease (IBD). Collectively, an innovative siRNA delivery strategy precisely tailored for pyroptotic cells has been developed, paving the way for new treatments for autoimmune inflammatory diseases with minimal side effects and wide clinical applicability.

Phagocytosis Checkpoints in Glioblastoma: CD47 and Beyond

Glioblastoma multiforme (GBM) is one of the deadliest human cancers with very limited treatment options available. The malignant behavior of GBM is manifested in a tumor which is highly invasive, resistant to standard cytotoxic chemotherapy, and strongly immunosuppressive. Immune checkpoint inhibitors have recently been introduced in the clinic and have yielded promising results in certain cancers. GBM, however, is largely refractory to these treatments. The immune checkpoint CD47 has recently gained attention as a potential target for intervention as it conveys a "don't eat me" signal to tumor-associated macrophages (TAMs) via the inhibitory SIRP alpha protein. In preclinical models, the administration of anti-CD47 monoclonal antibodies has shown impressive results with GBM and other tumor models. Several well-characterized oncogenic pathways have recently been shown to regulate CD47 expression in GBM cells and glioma stem cells (GSCs) including Epidermal Growth Factor Receptor (EGFR) beta catenin. Other macrophage pathways involved in regulating phagocytosis including TREM2 and glycan binding proteins are discussed as well. Finally, chimeric antigen receptor macrophages (CAR-Ms) could be leveraged for greatly enhancing the phagocytosis of GBM and repolarization of the microenvironment in general. Here, we comprehensively review the mechanisms that regulate the macrophage phagocytosis of GBM cells.

Sialic acid and Siglec receptors in tumor immunity and immunotherapy

Immunotherapy, including immune checkpoint inhibition, has transformed cancer therapy in recent years, providing new and potentially curative options for patients with even advanced disease. However, only a minority of patients achieve long-lasting remissions, and resistance to immune checkpoint inhibition is common. Recently, the sialic acid-Siglec axis has been proposed as a new immune checkpoint that could overcome resistance to current immunotherapy options. In this review, we summarize the current preclinical knowledge about the role of the sialic acid-Siglec interaction in immune suppression in cancer and discuss potential approaches to block this inhibitory pathway to enhance anti-cancer immunity.

Identification of BACH1-IT2-miR-4786-Siglec-15 immune suppressive axis in bladder cancer

The sialic acid binding Ig like lectin 15 (Siglec-15) was previously identified as tumor immune suppressor gene in some human cancers with elusive molecular mechanism to be elucidated. The continuous focus on both clinical and basic biology of bladder cancer leads us to characterize aberrant abundance of BACH1-IT2 associating with stabilization of Siglec-15, which eventually contributes to local immune suppressive microenvironment and therefore tumor advance. This effect was evidently mediated by miR-4786-5p. BACH1-IT2 functions in this scenario as microRNA sponge, and competitively conceals miR-4786 and up-regulates cancer cell surface Siglec-15. The BACH1-IT2-miR-4786-Siglec-15 axis significantly influences activation of immune cell co-culture. In summary, our data highlights the critical involvements of BACH1-IT2 and miR-4786 in immune evasion in bladder cancer, which hints the potential for both therapeutic and prognostic exploitation.