Senescent bone marrow mesenchymal stem cells promote multiple myeloma cell proliferation through galectin-3

Abstract

BACKGROUND: Studies showed that multiple myeloma microenvironment has the function of inducing mesenchymal stem cells to become senescent phenotype, while the effect of senescent bone marrow mesenchymal stem cells on multiple myeloma cells is rarely reported. OBJECTIVE: To investigate the effect of senescent bone marrow mesenchymal stem cells on the proliferation of multiple myeloma cells through paracrine galectin-3. METHODS: Bone marrow blood was collected from healthy donors, and bone marrow mesenchymal stem cells were extracted by Ficoll density gradient centrifugation and adherent purification. The third-generation bone marrow mesenchymal stem cells were taken and induced with 200 µmol/L hydrogen peroxide solution for 2 h, then cultured with L-DMEM complete medium for 24 h to construct a senescent bone marrow mesenchymal stem cell model. The model was identified by β-galactosidase staining and senescence gene P21 expression. RT-qPCR was used to detect the expression of galectin-3 in senescent bone marrow mesenchymal stem cells. The supernatant of senescent bone marrow mesenchymal stem cells was collected and concentrated by centrifugation to prepare conditioned medium, which was used to culture multiple myeloma cell line U266 for 24 h. CCK-8 was used to detect U266 cell proliferation, flow cytometry was used to detect U266 cell apoptosis, and RT-qPCR and western blot were used to detect BCL-2 protein and mRNA expression in U266 cells. Bone marrow from multiple myeloma patients and healthy individuals was collected, and galectin-3 levels were detected by ELISA. RESULTS AND CONCLUSION: After hydrogen peroxide induction, the number of β-galactosidase positive cells significantly increased, and the mRNA expression of P21 and galectin-3 was upregulated (P < 0.01). Compared with the control group, after culturing U266 cells with senescent bone marrow mesenchymal stem cell conditioned medium for 24 h, cell proliferation increased (P < 0.05), apoptosis rate decreased (P < 0.05), and BCL-2 protein and mRNA expression levels increased (P < 0.05). The level of galectin-3 in bone marrow of multiple myeloma patients was significantly higher than that of healthy individuals (P < 0.05). The results indicate that senescent bone marrow mesenchymal stem cells may promote the proliferation of multiple myeloma cells by upregulating BCL-2 expression through paracrine galectin-3.

1. Introduction

Multiple myeloma (MM) is a malignant hematological disease characterized by clonal plasma cell proliferation, clinically presenting with overproduction of monoclonal immunoglobulin or its fragments (M protein). It ranks second in incidence among hematological malignancies, after lymphoma. Epidemiological data show an incidence of 4.5-6.0 per 100,000 in Europe and approximately 1 per 100,000 in China [1-3]. Current treatments, including autologous stem cell transplantation, immunomodulatory drugs, proteasome inhibitors, and monoclonal antibodies, have improved survival rates, yet patients often experience relapse and drug resistance, with a 5-year survival rate below 40% [4-5]. The high heterogeneity of MM, driven by intrinsic genetic diversity of clonal plasma cells and interactions with the bone marrow microenvironment, poses major therapeutic challenges [6-7]. Bone marrow mesenchymal stem cells (BMSCs), a heterogeneous cell population in the marrow microenvironment, are closely associated with MM cell growth and bone destruction [8].

Like other tumors, BMSCs support MM cell growth through complex interactions. Studies have shown that BMSCs from MM patients exhibit senescence features, including increased β-galactosidase expression, enlarged cell size, and elevated senescence-associated secretory phenotype (SASP) members [9-10]. Senescent cells secrete various bioactive proteins, potentially altering the tissue microenvironment and promoting tumorigenesis [11]. In most hematological malignancies, the bone marrow microenvironment drives tumor progression and is also remodeled by tumor cells, targeting BMSCs and altering their biological properties [8,12]. Recent evidence suggests that senescent BMSCs may participate in disease progression and relapse by modifying the tumor microenvironment [13]. MM-derived BMSCs display early senescence characteristics, which may influence MM progression through regulation of the microenvironment.