In the present study, we identify TME-related genes from the TCGA database that contribute to the evaluation of survival in BRCA patients. CLEC10A is considered to be involved in the immune activity of the breast cancer tumor microenvironment. Importantly, a series of analyses suggested that CLEC10A may be a potential indicator of TME immune activity evaluation in BRCA patients.
TME plays a crucial role in the initiation and progression of tumorigenesis. Exploring potential therapeutic targets can help improve TME remodeling and the prognosis of BRCA patients. A large number of studies have revealed the importance of the immune microenvironment in tumorigenesis. The results of our transcriptomic analysis of BRCA data from the TCGA database suggested that the immune component of TME contributes to patient prognosis, although the stromal component may dominate BRCA progression (e.g., invasion). These results highlighted that the exchange between cancer cells, infiltrating immune cells and stromal cells affects the ecology of the breast cancer microenvironment, influencing disease progression and clinical outcome [11]. Immune infiltration plays an important role in breast cancer patients, especially in triple-negative breast cancer (TNBC) or her2-positive breast cancer patients [12]. New studies have confirmed that an increase in the percentage of tumor infiltrating lymphocytes (TIL) is associated with survival in patients with smaller volumes of primary breast cancer, with survival rates approaching 100% in patients with a TIL score of 30%, even in the absence of chemotherapy [13]. The efficacy of pembrolizumab monotherapy in patients with metastatic TNBC confirms that enrichment of CD8+ T cells predicts response to antitumor therapy [14]. Based on the transcriptomic analysis of BRCA in the TCGA database, we further found that the decreased expression of CLEC10A is closely related to the clinicopathological characteristics and poor prognosis of breast cancer. Therefore, it suggests that CLEC10A may be a potential prognostic marker and therapeutic target of TME in BRCA.
Protein glycosylation is known to have important effects in cell biological processes (such as proliferation, adhesion, differentiation, cell-cell interaction and immune response), and abnormal glycosylation is considered to be a hallmark of cancer [15]. Certain glycans with increased expression in tumor tissues compared to normal tissues are known as tumor-associated carbohydrate antigens (TACA) [16]. During tumor development, immune cells can detect the presence of TACA, which can enhance or weaken the immune response depending on the nature of the interaction [17]. The recognition of TACA is mediated by glycan binding protein, also known as lectin, whose binding specificity depends on their carbohydrate recognition domain (CRD). Macrophage galactose-type lectin (MGL; also known as CLEC10A or CD301), a member of the C-type lectin receptor (CLR) family [18], recognizes glycan structures in a Ca2+-dependent manner through the carbohydrate recognition domain (CRD) and plays an important role in both innate and adaptive immune responses [6]. CLEC10A is mainly expressed by antigen-presenting cells (APCs), such as tumor-associated dendritic cells (DCs) and macrophages [19], and which can specifically recognize terminal GalNAc residues (α- or β-linked) found in the (S)Tn antigens and LacdiNAc epitopes. [20]. It was found that the tumor-associated mucin MUC1 (MUC1-Tn) containing Tn antigen is frequently overexpressed in malignantly transformed epithelial adenocarcinomas (such as breast, pancreatic, colon), and binding to lectin receptors on mature dendritic cells activates T-cell activity to initiate anti-tumor immune responses, however, binding to immature dendritic cells may lead to immunosuppressive effects [21]. Our results suggest that CLEC10A expression is downregulated and associated with poor disease prognosis in the advanced stage of BRCA patients. The same results have been reported in hepatocellular carcinoma and colon cancer [22] [23]. Interestingly, in the MGL1 (human CLEC10A homolog) deficient mouse strain, mouse mite induced dermatitis is exacerbated [24] and tissue remodeling associated with chronic immune responses is almost completely absent [10], indicating that CLEC10A mediated immune infiltration may be involved in regulating stromal remodeling. Therefore, we further analyzed the relationship between CLEC10A expression and TME, and the GSEA results showed that the CLEC10A high expression group was significantly enriched in immune-related signaling pathways, such as antigen processing and presentation, B-cell signaling pathway, complement signaling pathway, and hematopoietic cell lineage. In the CLEC10A low expression group was enriched in glycosylphosphatidylinositol. All these results implied that CLEC10A may be involved in the regulation of immune infiltration in TME, especially the antitumor immune response. Importantly, the receptor ligand svL4 of CLEC10A (a peptide ligand mimic of MGL2) as a monotherapy for ovarian cancer has been proven to cause multiple-fold expansion of mature immune cell populations in the abdominal cavity and effectively inhibit the development of ascites in a mouse ovarian cancer model [25]. This may be an effective anti-cancer therapy.
In this article, CIBERSORT analysis of the proportion of TICs showed that activated memory CD4+ T cells, resting memory CD4+ T cells, and CD8+ T cells were positively correlated with CLEC10A expression in BRCA patients. In general, CD8+ cytotoxic T cells have been recognized as a key component of effective antitumor immunity, and breast cancer patients with higher CD8+ T cell infiltration have better survival [26]. However, lacking the help of sufficient CD4+ T cells, CD8+ T cells often fail to fully exploit their antitumor immunity in vivo[27]. As the main role of the immune system, CD4+ T cells play a vital role in many aspects of their recruitment, activation and regulation of adaptive immune responses. Their auxiliary functions in B cell and CD8+ cytotoxic T cell-mediated immune responses has been fully proven. However, tumor regulatory T cells (Treg) eliminate the early anti-tumor immune response induced by tumor-specific CD4+ T cells and CD8+ T cells and suppress multiple immune cells, such as CD4+ and CD8+ T cells, B cells, NK cells, NKT cells, dendritic cells (DCs) and macrophages [28]. Therefore, we predict that the downregulation of CLEC10A expression in advanced breast cancer tumors may be caused by the reduction of APC induced by regulatory T cells, which often leads to tumor cell immune tolerance. related studies are in progress.
In conclusion, our research indicates that CLEC10A is a valuable prognostic biomarker and immunotherapeutic target for breast cancer, and reveals that it may play an important role in the initiation of tumor immune response. With the development of sequencing technology, we believe that our model has great potential in clinical practice, thus further validating our results with clinical samples.