Department of Orthopedic Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Department of Diagnostic and Biomedical Sciences, The University of Texas Health Science Center at Houston, School of Dentistry, Houston, Texas.
Mol Cancer Ther. 2020 Jun;19(6):1266-1278. doi: 10.1158/1535-7163.MCT-19-0174. Epub 2020 Mar 27.
Renal cell carcinoma bone metastases (RCCBM) are typically osteolytic. We previously showed that BIGH3 (beta Ig-h3/TGFBI), secreted by 786-O renal cell carcinoma, plays a role in osteolytic bone lesion in RCCBM through inhibition of osteoblast (OSB) differentiation. To study this interaction, we employed three-dimensional (3D) hydrogels to coculture bone-derived 786-O (Bo-786) renal cell carcinoma cells with MC3T3-E1 pre-OSBs. Culturing pre-OSBs in the 3D hydrogels preserved their ability to differentiate into mature OSB; however, this process was decreased when pre-OSBs were cocultured with Bo-786 cells. Knockdown of BIGH3 in Bo-786 cells recovered OSB differentiation. Furthermore, treatment with bone morphogenetic protein 4, which stimulates OSB differentiation, or cabozantinib (CBZ), which inhibits VEGFR1 and MET tyrosine kinase activities, also increased OSB differentiation in the coculture. CBZ also inhibited pre-osteoclast RAW264.7 cell differentiation. Using RCCBM mouse models, we showed that CBZ inhibited Bo-786 tumor growth in bone. CBZ treatment also increased bone volume and OSB number, and decreased osteoclast number and blood vessel density. When tested in SN12PM6 renal cell carcinoma cells that have been transduced to overexpress BIGH3, CBZ also inhibited SN12PM6 tumor growth in bone. These observations suggest that enhancing OSB differentiation could be one of the therapeutic strategies for treating RCCBM that exhibit OSB inhibition characteristics, and that this 3D coculture system is an effective tool for screening osteoanabolic agents for further studies.
肾细胞癌骨转移（RCCBM）通常为溶骨性。我们之前的研究表明，BIGH3（β Ig-h3/TGFBI）由 786-O 肾癌细胞分泌，通过抑制成骨细胞（OSB）分化在 RCCBM 溶骨性骨病变中发挥作用。为了研究这种相互作用，我们采用三维（3D）水凝胶共培养骨源性 786-O（Bo-786）肾癌细胞与 MC3T3-E1 前成骨细胞。在 3D 水凝胶中培养前成骨细胞保留了分化为成熟 OSB 的能力；然而，当前成骨细胞与 Bo-786 细胞共培养时，这一过程减少了。Bo-786 细胞中 BIGH3 的敲低恢复了 OSB 分化。此外，骨形态发生蛋白 4（刺激 OSB 分化）或卡博替尼（CBZ）（抑制 VEGFR1 和 MET 酪氨酸激酶活性）的处理也增加了共培养物中的 OSB 分化。CBZ 还抑制前破骨细胞 RAW264.7 细胞的分化。在 RCCBM 小鼠模型中，我们表明 CBZ 抑制了 Bo-786 肿瘤在骨中的生长。CBZ 治疗还增加了骨体积和 OSB 数量，减少了破骨细胞数量和血管密度。在转导过度表达 BIGH3 的 SN12PM6 肾癌细胞中进行测试时，CBZ 也抑制了 SN12PM6 肿瘤在骨中的生长。这些观察结果表明，增强 OSB 分化可能是治疗表现出 OSB 抑制特征的 RCCBM 的治疗策略之一，并且该 3D 共培养系统是筛选用于进一步研究的促骨合成药物的有效工具。
