Although MM is a rare disease, it is the second most common malignant tumor of the blood system6. In the past few decades, treatment options for MM have continuously increased and improved, starting with the initial use of autologous stem cell transplantation, and developing to the application of new treatment options such as immunomodulatory drugs and proteasome inhibitors. Currently, in the treatment of MM, immunotherapy is routinely used. Immunomodulatory drugs such as lenalidomide, thalidomide, and later pomadolide have been shown to be effective in treating MM and significantly improve survival. MM can downregulate the recognition of cellular immune antigens and regulate the bone marrow microenvironment, thereby promoting the proliferation, anti-apoptotic ability, and immune escape ability of tumor cells, further inhibiting the anti-tumor immune ability. M. Swamydas et al. believe that immunomodulatory drugs, proteasome inhibitors, monoclonal antibodies (mAbs), checkpoint inhibitors, NK and T cell therapy have the potential to reverse immunosuppression and restore effective immune monitoring1. Through bioinformatics analysis, the study explored the potential immune-related hub genes and immune infiltration patterns in patients with MM, providing new biomarkers for the treatment and evaluation of therapeutic effectiveness of MM.
Two data sets GSE24870 and GSE146649 were included in the study. Seven different co-expression modules were established through WGCNA, with brown modules significantly associated with the pathogenesis of MM. The GO and KEGG enrichment analysis of immune-key genes showed that immune-key genes were mainly enriched in immune response, cell surface receptor signaling pathways, T cell co-stimulation, immune synapses, transmembrane signal receptor activity, CD4 receptor binding, and T cell receptor binding. Pathway enrichment is mainly concentrated in osteoclast differentiation, immune cell related receptor signaling pathways, malignant tumor immune checkpoint pathways, and signal transduction pathways.
Further immune infiltration analysis revealed that there were 6 different types of infiltrating immune cells between MM and healthy control samples: activated CD8 T cells, activated dendritic cells, monocytes, macrophages, plasmacytoid dendritic cells, and natural killer cells. By using LASSO logistic regression analysis and identifying the expression levels of immune-related hub genes in the gene dataset GSE6651 and GSE47552, the study considers ADAM8, CR2, and TNFSF14 to be the most valuable.
Research has found that7 the ADAM family is involved in mediating the degradation of extracellular matrix in cartilage in osteoarthritis. ADAM8 is one of the ADAM proteases, also known as CD156, which is expressed in macrophages, neutrophils, and NK cells12, 2. M.D. Zack et al. believe that9 ADAM8 is a fibronectin in human osteoarthritis chondrocytes and an important mediator in cartilage catabolism. In addition, ADAM8 has also been identified as a regulator of osteoclast formation and bone erosion associated with rheumatoid arthritis3, 5. CR2, also known as CD21, is a membrane glycoprotein that is one of numerous cell surface proteins that bind to the activation and processing fragments of the complement system6 Suppl. CD21 plays an important role in the selection of high affinity B cells and the development and maintenance of B cell memory10. K. Thorarinsdottir et al. believe that2 low expression or deletion of CD21 can mediate joint destruction in patients with rheumatoid arthritis. In addition, a study on B-cell chronic lymphoblastic leukemia reported that32 low expression of CD21 can predict a decrease in overall survival in patients with B-cell chronic lymphoblastic leukemia, and is significantly associated with adverse clinical outcomes. TNFSF14(LIGHT) is a protein that is mainly expressed on activated T cells, activated natural killer cells, and immature dendritic cells12. The expression of LIGHT in tumors has a profound impact on the host's immune response to tumors and the remodeling of tumor microenvironment. Some studies have shown that24 LIGHT can cause the development of MM osteopathy through direct osteoclast promotion and indirect inhibition of osteogenic reactions. G. Brunetti and R Research by Rizzi, G reported tha high LIGHT levels produced by immune cells contribute to osteoclast formation and bone destruction in MM related bone diseases.
CD8 T cells are important participants in innate and adaptive immune defense mechanisms, and are the body's defense line against various harmful factors2. In a study targeting various cancers, it was found that11 the abundance of CD8 T cells in tumors is the best predictor of response to anti PD-1/PD-L1 therapy. The use of immune checkpoint inhibitors can increase the effector function of CD8 T cells in patients with MM and control the progression of MM16.
Macrophages are a ubiquitous cellular component that exists in all tissues under stable physiological conditions12. The interaction between immune cells and osteoclasts in the bone marrow or joint cavity is the basis of bone immunity, and the macrophage osteoclast axis plays a crucial role. Fusion and multinucleation of macrophages are key to the formation of osteoclasts to control bone balance17. Y. Zheng et al. found that17 macrophages can help suppress anti-tumor immunity, enable survival of myeloma cells, and increase resistance to chemotherapy in MM.
Plasmacytoid dendritic cells are a unique cell lineage derived from bone marrow, mainly present in the blood and lymphatic organs. It is reported that4 plasmacytoid dendritic cells accumulate in the bone marrow of patients with MM. These plasmacytoid dendritic cells not only stimulate the proliferation of T cells, but also promote the growth and survival of myeloma cells. Research by A. Ray, Z. Tian et al. found that8 the number of plasmacytoid dendritic cells in the bone marrow microenvironment of MM increased, which not only contributes to the immune dysfunction of MM, but also promotes the progression and drug resistance of myeloma cells.
The study ultimately concluded that three immune hub genes (ADAM8, CR2, and TNFSF14) and three main types of peripheral immune cells (activated CD8 T cells, macrophages, and plasmacytoid dendritic cells) are closely related to the pathogenesis of MM. In addition, the study found that the expression level of TNFSF14 (LIGHT) in peripheral blood of patients with MM significantly decreased after treatment, and compared with healthy patients, TNFSF14 (LIGHT) showed a high expression state in myeloma patients. In addition, the relationship between immune hub genes and immune cells was discussed previously, suggesting that the high expression of TNFSF14 may be significantly related to the activity of CD8 T cells and macrophages.
In future research, it is necessary to focus on the mechanisms of ADAM8, CR2, and TNFSF14. The abnormal expression of these genes is closely related to the immunopathological process of MM. Further research has revealed the correlation between ADAM8, CR2, and TNFSF14 and immune cells, supporting the crucial role of these genes in MM by regulating immune infiltration, This may provide a better understanding of molecular targeted treatment strategies for improving MM.