研究认为异常分化是骨肉瘤恶性进展和化疗耐受的主要原因。我们前期实验中，mRNA测序分析发现BRINP3 mRNA在低分化人骨肉瘤组织中上调，下调人骨肉瘤细胞中BRINP3的表达可明显诱导细胞分化，抑制细胞增殖，提高细胞对DOX化疗敏感性。进一步实验发现，下调BRINP3的表达，可能通过激活TGF-β/Smad5/Runx-2信号通路促进骨形成重要蛋白Runx-2的表达，进而促进骨肉瘤细胞的分化。据此我们提出设想，联合BRINP3基因沉默和DOX可诱导骨肉瘤分化，抑制增殖，增强肿瘤对DOX的敏感性，提高化疗疗效，从而协同抑制骨肉瘤的恶性进展。本项目拟采用前期自主研发的多功能新型纳米级多糖聚合物Amy-g-PLLD负载BRINP3 shRNA和DOX，研究其在体内外诱导骨肉瘤分化和提高化疗疗效的协同作用，并阐明BRINP3调节骨肉瘤细胞分化的机制，开拓骨肉瘤治疗的新方法。

Abnormal differentiation is considered to be the main cause of malignant progression and chemotherapy tolerance of osteosarcoma. Our previous study found that BRINP3 mRNA was up-regulated in low-differentiated human osteosarcoma tissues by RNA sequencing analysis. Downregulation of BRINP3 expression in human osteosarcoma cells could significantly induce cell differentiation, inhibit cell proliferation and enhance cell sensitivity to DOX. Further study showed that down-regulation of BRINP3 expression might promote the expression of Runx-2, an important bone morphogenetic protein, by activating the TGF-beta/Smad5/Runx-2 signaling pathway, thus promoting the differentiation of osteosarcoma cells. Therefore, we propose that the combination of BRINP3 gene silencing and DOX could induce osteosarcoma cell differentiation, inhibit cell proliferation, enhance the sensitivity of tumor cells to DOX, and improve the efficacy of chemotherapy, thereby synergistically inhibiting the malignant progression of osteosarcoma. In this project, a novel multifunctional nano-polysaccharide polymer, Amy-g-PLLD loaded with BRINP3 shRNA and DOX will be used to study the synergistic effect of BRINP3 on inducing osteosarcoma differentiation and improving the efficacy of chemotherapy in vitro and in vivo, and to further elucidate the mechanism of BRINP3 regulating osteosarcoma cell differentiation, to explore a new method for the treatment of osteosarcoma.