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

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.

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.

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)-β-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-β-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 β-catenin protein, increasing expressions of IL-6 and TNF-α, as well as activating mature TGF-β1 and some other metabolic pathways.

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.