Cutaneous malignant melanoma (CMM) is a skin-related devastating cancer characterized by complicated internetwork, and many genetic factors participate in its progression[1, 5]. For years, the traditional therapeutic methods, such as immunotherapies, chemotherapies, and targeted-therapies, have improved patients’ survival to some extent[17]. However, early-stage diagnostic markers and effective therapies for CMM patients are unavailable at present. Indeed, many patients in clinical suffered drug resistance and allergic by adapting these therapies and result in poor prognosis[3]. Therefore, more patient-friendly therapeutic and valuable prognostic molecules must be established. In recent years, owing to bioinformatics methods evolving that ensure researchers have access to the public database to explore and offer a new angle to carcinoma-involved molecules.
In this study, we divided all the cases downloaded from the TCGA platform into two different groups marked high and low immune/stromal scores, respectively. Then, 908 DEGs (900 upregulation and eight down-regulation) were screened from the immune score and stromal score based on the ESTIMATE algorithm[8]. The functional enrichment analysis indicated that immune response and inflammatory response were firmly involved in CMM tumorigenesis. GO annotation mainly enriched in T cell activation (GO:0042110), regulation of lymphocyte activation (GO:0051249), and regulation of T cell activation (GO:0050863). We conclude that immune cells in extracellular space are of significant importance to tumorigenesis. The results of KEGG pathways in DEGs, including Cytokine-cytokine receptor interaction (hsa04060), Hematopoietic cell lineage (hsa04640) and Cell adhesion molecules (CAMs) (hsa04514), which indicated cytokine and its receptor, coupled with immune cells, played a dominant role in the progression of CMM. Then, the PPI network unveiled the interaction network among these DEGs and demonstrated the intricate interaction of them. We identified ten hub genes and three major modules based on scores, respectively. The core genes are as follows: CCL5, CXCL10, CD74, CXCL9, CD247, IL10, CXCL11, CXCR3, CD3E, and SYK.
C–X–C motif ligand 9,10,11 (CXCL9, CXCL10, CXCL11) is a member of the CXC family chemokine. They are principally expressed by immune cells such as macrophages and T cells, and they play a significant role in immune cell infiltration into the tumour bed. They are supposed to act as a tumour-suppressive molecule[18, 19]. CXCR3, the receptor for CXCL9 and CXCL10, is highly expressed on CD8+ and CD4+ immune-infiltrating lymphocytes, it is highly likely that local production of CXCL9/10 can modulate T-cell recruitment and activation in human cancers[18–20]. These chemokines are increased following expose to anti-PD-1 and that they are crucial for therapeutic activity and correlate with patient prognosis[21]. The expression of CXCL11 correlated with improved responses to atezolizumab and was the most significantly upregulated gene in macrophages responding to immune checkpoint blockade and its function highly relative to CXCL9 and CXCL10[22, 23]. C–C motif ligand 5, CCL5, is a small protein that belongs to a large family of cytokines and displays chemotaxis activity for it is involved in promoting the migration of several leukocytes into inflammation sites. CCL5 is secreted by a wide variety of cells, including T cells, NKs, and some tumour cells. Previous data showed that targeting CCL5 was sufficient to inhibit the infiltration of NK cells significantly and subsequently enhance the tumour growth[24, 25]. Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine and serves as a regulator of the innate immune system. Studies have shown that MIF induces an immune-suppressive environment that supports melanoma progression and metastasis. CD74 is the central receptor for MIF and the invariant chain of the MHC class II, which plays an essential role in antigen presentation. MIF and CD74 are attractive targets for immunotherapy. MIF binding to CD74 activates the PI3K/AKT and MAPK signalling pathways, and both these pathways have been related to monocyte immune-suppression and macrophage M2-like polarization to regulate the immune response against metastatic melanoma[26–28]. Spleen tyrosine kinase (SYK) functions as a non-receptor kinase, mediating signal transduction of cellular transmembrane receptors and act as immunoreceptors and integrins. SYK has been demonstrated to be a critical regulator of the target of rapamycin (mTOR) activity in B-cell lymphoma[29, 30]. IL-10 is a potent anti-inflammatory molecule produced by innate and adaptive immune cells, including T cells, NK cells, as well as tumour cells. IL-10 is an immune-regulatory cytokine that may exert immune-stimulatory effects on CD8+ T cells, depending on their state of activation[21]. CD247 plays a crucial role in triggering the TCR signalling pathway, and high expression levels of CD247 was associated with poor overall survival in lower-grade glioma[2]. Nevertheless, the correlation of CD247 and CMM patients’ overall survival has been no reported in recent years.
Then, we used a univariate Cox model to determine prognostic-related genes highly correlated with overall survival (OS). We combined the identified prognostic-related genes with the immune-related DEGs from the PPI network, and CD247 was the intersection gene for further explored, pair-difference analysis between tumour cases and normal cases and overall survival curve was performed for CD247. The results showed that CD247 highly expressed in tumour samples and possessed a better prognosis than lower expressed samples. In these findings, WGCNA analysis showed that 11 modules were identified. Then, the relationship between each module traits was studied. Specifically, genes belong to module brown had the highest positive correlation with CMM patients’ prognosis, and CD247 included in this module, which suggested CD247 higher expressed samples have a better prognosis.
Moreover, CMM patients with high expression of the ten genes (CCL5, CXCL10, CD74, CXCL9, CD247, IL10, CXCL11, CXCR3, CD3E, and SYK) were associated with better OS. IHC results from the HPA verified that IL10, CXCR3, SYK, CD247, CD74, CXCL11 were significantly overexpressed in CMM tissues. The results suggested that CD247 was an essential biomarker in CMM tumorigenesis, progress, and prognosis. Also, the expressions of CD247 was positively correlated with six immune cells infiltration (CD8+ T cell, MacrophagesM1, activated CD4 memory T cell, regulatory T cell, helper follicular T cell, and activated NK cell). Previous studies suggested that high levels of immune cell infiltration are associated with favourable outcomes. Increasing levels of CD8+ T cells, MacrophagesM1, activated CD4 memory T cell, NK cell, were related to longer survival time in CMM patients. More critical, CMap analysis tool was used to search for potential drugs or compounds to cure CMM. It was reported that L-securinine inhibits prostate cancer cell growth and metastasis via regulating mitochondrial and AGTR1/MEK/ERK apoptotic pathways and may be a promising candidate medicine for CMM[31]. However, there is no relevant research on the effect of these compounds on CMM.
Even though the paramount role of TME in CMM has been reported, many engaged in the immune infiltrating CD8+ T cell. Notably, our study embraces several merits. First, we examined the correlation between immune infiltrating macrophages (M0, M1, M2) and CD247 expression, which is indicated that macrophages, an indispensable part of the microenvironment (TME), was involved in CMM tumorigenesis and progression. Second, the RNA-seq profiling matrix was collected from the TCGA platform, which contained 468 CMM cases. We explored the OncoLnc website, the HPA resource, and the GEPIA database to confirm the results. Finally, the TME and immune-related molecules interact in a changing procession, which subjected to numerous factors, such as immune cells and genetic aspects. We thoroughly investigated the underlying association of TME and immune-linked genes from the element of CMM microenvironment, stromal/immune condition, CD247, and other prognostic-relevant genes and immune cells infiltrating.