[Bone Marrow Adipocytes Promote the Survival of Multiple Myeloma Cells and Up-Regulate Their Chemoresistance].

OBJECTIVE: To investigate the effect of adipocytes in the bone marrow microenvironment of patients with multiple myeloma (MM) on the pathogenesis of MM. METHODS: Bone marrow adipocytes (BMA) in bone marrow smears of health donors (HD) and newly diagnosed MM (ND-MM) patients were evaluated with oil red O staining. The mesenchymal stem cells (MSC) from HD and ND-MM patients were isolated, and in vitro co-culture assay was used to explore the effects of MM cells on the adipogenic differentiation of MSC and the role of BMA in the survival and drug resistance of MM cells. The expression of adipogenic/osteogenic differentiation-related genes PPAR-γ, DLK1, DGAT1, FABP4, FASN and ALP both in MSC and MSC-derived adipocytes was determined with real-time quantitative PCR. The Western blot was employed to detect the expression levels of IL-6, IL-10, SDF-1α, TNF-α and IGF-1 in the supernatant with or without PPAR-γ inhibitor. RESULTS: The results of oil red O staining of bone marrow smears showed that BMA increased significantly in patients of ND-MM compared with the normal control group, and the BMA content was related to the disease status. The content of BMA decreased in the patients with effective chemotherapy. MM cells up-regulated the expression of MSC adipogenic differentiation-related genes PPAR-γ, DLK1, DGAT1, FABP4 and FASN, but the expression of osteogenic differentiation-related gene ALP was significantly down-regulated. This means that the direct consequence of the interaction between MM cells and MSC in the bone marrow microenvironment is to promote the differentiation of MSC into adipocytes at the expense of osteoblasts, and the cytokines detected in supernatant changed. PPAR-γ inhibitor G3335 could partially reverse the release of cytokines by BMA. Those results confirmed that BMA regulated the release of cytokines via PPAR-γ signal, and PPAR-γ inhibitor G3335 could distort PPAR-γ mediated BMA maturation and cytokines release. The increased BMA and related cytokines effectively promoted the proliferation, migration and drug resistance of MM cells. CONCLUSION: The BMA and its associated cytokines are the promoting factors in the survival, proliferation and migration of MM cells. BMA can protect MM cells from drug-induced apoptosis and plays an important role in MM treatment failure and disease progression.

[Effect of the Connexin 43 Coupling to the Biobehavior of Multiple Myeloma Cells].

OBJECTIVE: To investigate the effect of gap junction intercellular communication (GJIC) combined by connexin43 (Cx43) and its signal to the biobehavior of multiple myeloma (MM) cells, and its possible mechanism. METHODS: The mesenchymal stem cell (MSC) cells were isolated and cultured from patients with MM and normal donors. The expression of connexin43 (Cx43) in MSC cells from different sources was detected by RT-PCR and Western blot. The side population (SP) cells were sorted by flow cytometry (FCM). The effect of MSC cells from different sources to the cell cycle, Cx43 expression, colony formation in vitro, stem cell related genes expression, cytokines secretion and chemoresistance in MM SP cells as well as with or without Cx43 inhibitor 18α-glycyrrhetinic acid (18α-GA) was observed. RESULTS: There was no significantly difference between the MSC isolated from normal donor and MM patients. Western blot showed that Cx43 expression in SP cells was up-regulated when the cells were incubated with MSC, and medium containing 18α-GA could partially inhibit it, moreover, it was more significant in MSC cells of MM patients. The ability of colony formation of SP cells in vitro was higher than those of MM cells and MM-MSC could promote the colony formation in a co-culture manner. The effect of MM-MSC to SP cells was down-regulated after 18α-GA was added. RT-PCR showed that there was several important stem cell-related genes including c-myc, Oct-4 Klf-4, and Sox-2 were found in RPMI 8226 cells, but those cells were up-regulated in SP cells (P<0.001). Meanwhile, MM-MSC could up-regulate the expression of c-myc, Klf-4 and Sox-2 (P<0.001), but down-regulate Oct-4 gene in the SP cells. The expression of those genes decreased after 18α-GA was added, but showed no significant difference (P>0.05). Cytometry bead array assays showed that MM-MSCs could secrete high level of IL-6, but the levels of IL-6, IL-10 and TGF-ß increased significantly when the MM-MSCs were co-cultured with SP cells (P<0.05), especially the levels of IL-6 and IL-10 were significantly higher than cultured alone. There was no significant change in the levels of bFGF and IL-17 before and after co-cultured. The levels of IL-6, IL-10 and TGF-ß in supernatant decreased significantly after GJ inhibitor 18α-GA was added. PI/Annexin V assay showed that MM cells were sensitive to bortezomib (BTZ)-induced apoptosis, but the sensitivity for SP cells was weaker. The ratio of cell apoptosis was 75.2%±0.77% and 8.12%±0.86% (P<0.001), respectively. MM-MSC could down-regulate the cell apoptosis induced by BTZ, while the sensitivity of MM cells to BTZ could be partially recovered after GJ inhibitor was added. CONCLUSION: MSC derived from MM patients can enhance GJIC to maintain its "hematopoiesis" by up-regulating the expression of Cx43 in MM cells, and at the same time promote cell proliferation and drug recistance by secreting multiple cytokines, which finally contributes to the relapse of MM.

EBV­BART­6­3p and cellular microRNA­197 compromise the immune defense of host cells in EBV­positive Burkitt lymphoma.

The present study aimed to identify the association between Epstein­Barr virus (EBV) microRNA (miRNA) and cellular miRNA in compromising the immune system, which contributes to the development of Burkitt lymphoma (BL). The present study selected cellular miR­197 as the focus of the experiments due to the previous report that it is differentially expressed and the observation that interleukin­6 receptor (IL­6R) is a virtual target of miR­197 and EBV­BamHI A region rightward transcript (BART)­6­3p. In the present study, IL­6R was confirmed as a target of cellular miR­197 using a luciferase assay, and the negative regulatory association between miRNA (miR­197 and EBV­BART­6­3p) and mRNA (IL­6R) was confirmed by the observation that IL­6R was downregulated in EBV­positive Burkitt lymphoma and that miR­197 was upregulated. Additionally, mimics of EBV­BART­6­3p and miR­197 were introduced into lymphoma cells, and it was found that EBV­BART­6­3p and miR­197 synergistically reduced the expression of IL­6R. These findings improved current understanding of the role of miR­197/ EBV­BART­6­3p and their target, IL­6R, in the development of EBV­positive BL, and they may offer potential as novel therapeutic targets for the treatment of EBV­positive malignancies.

[Study of biological behavior of stromal cell-derived factor-1 on multiple myeloma cell migration and adhesion].

OBJECTIVE: To investigate the biological behavior of stromal cell-derived factor-1 (SDF-1) on multiple myeloma (MM) cell migration and adhesion and it related signaling pathways. METHODS: Expression of adhesion molecules on MM cells of RPMI8226, XG-1 and XG-7 cells was analysed by flow cytometry, the influence of SDF-1 on CD29 and CD49e distribution by immunofluorescence, the effect of SDF-1 on chemotaxis of MM cells by transwell assay. Activation of phosphoinositide-3 kinase (PI3K) in MM cells treated with SDF-1 and by immunoblotting. RESULTS: 3 strains of MM cell line expressed many adhesion molecule. RPMI8226, XG-7 cells were all high level of expression of CD29 (> 70%). XG-1, XG-7 cells were all high level of expression of CD44 (> 80%), and XG-7 cells was of CD49d (> 90%). In all of 3 strains, the levels of expression of CD49e were low (< 30%). SDF-1 could not upregulate their expression, but could trigger the establishment of polarized morphology of MM cells and the redistribution of CD29 and CD49e. SDF-1 promoted MM cells adhesion to endothelial cells, stimulated phosphorylation of P85 subunit of PI3K in MM cells and induced MM cells migration, which were inhibited by G protein inhibitor PTX and PI3K inhibitor wortmannin. CONCLUSION: SDF-1 can promote MM cell adhesion to endothelial cells, trigger establishment of a polarized morphology of MM cells and redistribution of adhesion molecules and induce MM cells migration via PI3K signaling pathway.