In vitro and in vivo efficacy of the novel oral proteasome inhibitor NNU546 in multiple myeloma.

Proteasome inhibition demonstrates highly effective impact on multiple myeloma (MM) treatment. Here, we aimed to examine anti-tumor efficiency and underlying mechanisms of a novel well tolerated orally applicable proteasome inhibitor NNU546 and its hydrolyzed pharmacologically active form NNU219. NNU219 showed more selective inhibition to proteasome catalytic subunits and less off-target effect than bortezomib ex vivo. Moreover, intravenous and oral administration of either NNU219 or NNU546 led to more sustained pharmacodynamic inhibitions of proteasome activities compared with bortezomib. Importantly, NNU219 exhibited potential anti-MM activity in both MM cell lines and primary samples in vitro. The anti-MM activity of NNU219 was associated with induction of G2/M-phase arrest and apoptosis via activation of the caspase cascade and endoplasmic reticulum stress response. Significant growth-inhibitory effects of NNU219 and NNU546 were observed in 3 different human MM xenograft mouse models. Furthermore, such observation was even found in the presence of a bone marrow microenvironment. Taken together, these findings provided the basis for clinical trial of NNU546 to determine its potential as a candidate for MM treatment.

Bioactive Compounds from Abelmoschus manihot L. Alleviate the Progression of Multiple Myeloma in Mouse Model and Improve Bone Marrow Microenvironment.

PURPOSE: Abelmoschus manihot (L.) Medik. (Malvaceae) derived Huangkui capsules (HKC) represent a traditional Chinese medicine that has been widely applied to the clinical therapy of kidney and inflammatory diseases. The present study aimed to determine the potential therapeutic effects and underlying mechanisms of the ingredients on Multiple Myeloma (MM), an incurable disease that exhibits malignant plasma cell clonal expansion in the bone marrow. METHODS: A 5TMM3VT syngeneic MM-prone model was established and treated with HKC. Murine pre-osteoblast MC3T3-E1 and pre-osteoclast Raw264.7 cells were treated with nine flavonoid compounds extracted from the flowers of Abelmoschus manihot. MC3T3-E1 and Raw264.7 cells were then examined by alizarin red staining and tartrate-resistant acid phosphatase activity staining, respectively. The proliferation of two human MM cells (ARP1, H929) was examined by performing an MTT assay following treatment with flavonoid compounds. Additionally, the cell cycle was analyzed via staining and flow cytometry. The differential expressions of certain proteins were detected via Western blotting, transcriptomic RNA-sequencing as well as RT-qPCR. RESULTS: The results revealed that MM-prone animals appeared to be protected following HKC treatment, as evidenced by a prolonged survival rate. Furthermore, four of the nine flavonoid compounds [Hyperin/Hyperoside, HK-2; Cannabiscitrin, HK-3; 3-O-kaempferol-3-O-acetyl-6-O-(p-coumaroyl)-ß-D-glucopyranoside, HK-11; 8-(2''-pyrrolidione-5''-yl)-quercetin, HK-B10] induced the differentiation of murine pre-osteoblast MC3T3-E1 cells. In addition, two compounds [Isomyricitrin, HK-8; quercetin-8-(2''-pyrrolidione-5"-yl)-3'-O-ß-D-glucopyranosid, HK-E3] suppressed osteoclastogenesis in murine Raw264.7 cells. HK-11 directly inhibited MM cells (ARP1 and H929) proliferation and induced G0/G1 cell cycle arrest, which may have involved the suppressing ß-catenin protein, increasing expressions of IL-6 and TNF-α, as well as activating mature TGF-ß1 and some other metabolic pathways. CONCLUSION: These results of the present study indicated that the bio-active ingredients of HKC exerted protective effects on MM mouse survival through promoting osteoblastogenesis and suppressing osteoclastogenesis, thus improving the bone marrow microenvironment to inhibit MM cell proliferation.

The impact of the bone marrow microenvironment on multiple myeloma (Review).

Multiple myeloma (MM) is characterized by the accumulation of monoclonal plasma cells in the bone marrow (BM). The interaction between the BM microenvironment and MM plasma cells can influence cell proliferation, drug resistance and prognosis of the disease. The BM microenvironment (BMME) consists of a cellular and non­cellular compartment. The cellular compartment includes stromal cells, endothelial cells, osteoclasts and osteoblasts, and the non­cellular compartment includes the extracellular matrix (ECM) and the liquid milieu, which contains cytokines, growth factors and chemokines. The complex interaction between the BM microenvironment and MM plasma cells influences disease development and prognosis. The present review focuses on the interaction between malignant plasma cells and the BM microenvironment during MM progression. An improved understanding of the interaction between MM plasma cells and their microenvironment will enable the development of novel therapeutic tools that can be used in the treatment of MM, a currently incurable blood cancer.

Targeting MK2 Is a Novel Approach to Interfere in Multiple Myeloma.

MAPKAPK2 (MK2), the direct substrate of p38 MAPK, has been well-acknowledged as an attractive drug target for cancer therapy. However, few studies have assessed the functions of it in multiple myeloma (MM). In the present study, MK2 expression of MM patients was analyzed by gene expression profiling (GEP) and array-based comparative genomic hybridization (aCGH). Several experiments in vitro including MTT assay, Western blot and flow cytometry analysis were performed to identify the function of MK2 in MM. In addition, we conducted mouse survival experiments to explain the effects of MK2 on MM in vivo. mRNA level of MK2 and chromosomal gain of MK2 locus in MM cells significantly increased compared to normal samples. Furthermore, MM patients with high expression of MK2 were associated with a poor outcome. Follow-up studies showed that MK2 exerted a remarkably positive effect on MM cell proliferation and drug-resistance. Further exploration focusing on MK2 inhibitor IV revealed its inhibitory action on MM growth and drug-resistance, as well as improving survival in mouse models. In addition, a combination of MK2 inhibitor IV and the key MM therapeutic agents including bortezomib, doxorubicin, or dexamethasone facilitated curative effects on inhibiting MM cell proliferation. Taken together, our study reveals the clinical relevance of MK2 inhibition in MM and demonstrates that targeting MK2 may afford a new therapeutic approach to MM.

BTK induces CAM-DR through regulation of CXCR4 degradation in multiple myeloma.

Cellular adhesion-mediated drug resistance (CAM-DR) occurs frequently in patients with relapsed or refractory multiple myeloma (MM). Elucidating the mechanism underlying CAM-DR and developing the corresponding treatment may prove to be promising for the clinical management of MM. Bruton's tyrosine kinase (BTK) has been attracting attention in relation to MM progression and drug resistance. BTK was reported to be associated with cell surface CXCR4, a classic cell adhesion molecule and homing factor. However, the exact association between BTK and CAM-DR in MM remains elusive. In this study, we demonstrated that promoting BTK expression induced MM cell adherence to the extracellular matrix (ECM) and stromal cells in vitro and in vivo, and that CAM-DR could be reversed by separating MM cells from ECM or stromal cells. Enhancing BTK expression levels increased CXCR4 expression in MM cells. In addition, BTK may bind directly with CXCR4 and prevent its ubiquitination-induced degradation. Finally, a BTK inhibitor exerted synergistic therapeutic effects with bortezomib in a 5TMM3VT MM mouse model. These findings revealed a novel role of BTK in CAM-DR and may provide a promising approach to MM treatment.

Loquat leaf polysaccharides improve glomerular injury in rats with anti-Thy 1 nephritis via peroxisome proliferator-activated receptor alpha pathway.

Chronic glomerulonephritis frequently develops into renal failure that cannot be completely cured. Based on the success of anti-inflammatory Chinese herbs in treating chronic nephritis, our goal was to investigate the therapeutic effects and mechanism of action of loquat leaf polysaccharides (LLPS) on chronic anti-Thy-1 nephritis. A rat model of glomerulonephritis was used to study the effects of 8 weeks of enalapril or LLPS treatment. Twenty-four-hour rat urinary protein excretions were measured every week for 8 weeks. Then, all animals were sacrificed, renal-related biochemical parameters were analyzed, and histology and electron microscopy examinations of renal tissue samples were conducted. Renal cortex tissue was used to detect markers of renal fibrosis. RNA sequencing (RNA-seq) and in vitro experiments explored the signaling pathway involved in LLPS treatment effects. Compared with the disease control group, LLPS treatment significantly decreased the levels of serum creatinine and blood urea nitrogen, reduced urinary protein excretion, glomerular mesangial cell proliferation, and extracellular matrix hyperplasia, and attenuated the expression of proteins associated with podocyte injury and renal fibrosis. RNA-seq results showed that peroxisome proliferator-activated receptor (PPAR) is a potential signaling pathway involved in LLPS treatment of chronic glomerulonephritis. Increases in PPARα and plasminogen activator inhibitor-1 (PAI-1) caused by glomerulonephritis were inhibited by LLPS in vitro. Furthermore, when an agonist of PPARα (BMS-687453) was used to stimulate PPARα activity, LLPS treatment suppressed the expression of fibrosis factor PAI-1 partially via PPARα inhibition. These findings demonstrate that LLPS improved glomerular injury in rats with anti-Thy 1 nephritis via the PPARα pathway.