Sinomenine prevents metastasis of human osteosarcoma cells via S phase arrest and suppression of tumor-related neovascularization and osteolysis through the CXCR4-STAT3 pathway.

Osteosarcoma is the most common primary malignant tumor of the bone. The long-term survivals continue to be unsatisfactory for patients with metastatic and recurrent disease. Metastasis is still a severe challenge in osteosarcoma treatment. Sinomenine, an alkaloid from traditional Chinese medicine, has been proved to possess potent antitumor and anti-invasion effect on various cancers. However, the effect of sinomenine on human osteosarcoma and the underlying mechanisms remains unknown. We report here that sinomenine inhibited proliferation by inducing S phase arrest and suppressing the clone formation. Significant inhibitory effects were found in invasion and metastasis in osteosarcoma, but little cytotoxicity was observed in tested concentrations. Exposure to sinomenine resulted in suppression of invasion and migration in osteosarcoma cells as well as tube formation ability in the human umbilical vein endothelial cells (HUVEC) and U2OS cells. Furthermore, it demonstrated that CXCR4 played a key role contributing to invasion in osteosarcoma which is considered to be a core target site in sinomenine treatment. Sinomenine inhibited invasion by suppressing CXCR4 and STAT3 phosphorylation then downregulating the expression of MMP-2, MMP-9, RANKL, VEGF downstream. In addition, then RANKL-mediated bone destruction stimulated by osteoclastogenesis and VEGF-related neovascularization were restrained. Importantly, in vivo, sinomenine suppressed proliferation, osteoclastogenesis and bone destruction. Through these various comprehensive means, sinomenine inhibits metastasis in osteosarcoma. Taken together, our results revealed that sinomenine caused S phase arrest, inhibited invasion and metastasis via suppressing the CXCR4-STAT3 pathway and then osteoclastogenesis-mediated bone destruction and neovascularization in osteosarcoma. Sinomenine is therefore a promising adjuvant agent for metastasis control in osteosarcoma.

An RNA architectural locus control region involved in Dscam mutually exclusive splicing.

The most striking example of alternative splicing in a Drosophila melanogaster gene is observed in the Down syndrome cell adhesion molecule, which can generate 38,016 different isoforms. RNA secondary structures are thought to direct the mutually exclusive splicing of Down syndrome cell adhesion molecule, but the underlying mechanisms are poorly understood. Here we describe a locus control region that can activate the exon 6 cluster and specifically allow for the selection of only one exon variant in combination with docking site selector sequence interactions. Combining comparative genomic studies of 63 species with mutational analysis reveals that intricate, tandem multi-'subunit' RNA structures within the locus control region activate species-appropriate alternative variants. Importantly, strengthening the weak splice sites of the target exon can remove the locus control region dependence. Our findings not only provide a locus control region-dependent mechanism for mutually exclusive splicing, but also suggest a model for the evolution of increased complexity in a long-range RNA molecular machine.