Department of Pathology, Childrens Hospital Los Angeles Saban Research Institute, Los Angeles, CA 90027, USA.
Oncogene. 2010 May 13;29(19):2772-83. doi: 10.1038/onc.2010.50. Epub 2010 Mar 1.
Although retinoic acid (RA) is a potent agent that coordinates inhibition of proliferation with differentiation of many cell types, RA-mediated signaling pathways in osteosarcoma cell differentiation are uncharacterized. In this study, we show that in human U2OS osteosarcoma cells, decreased phosphorylation of RA receptor alpha (RARalpha) by RA treatment or overexpressing a phosphorylation-defective mutant RARalphaS77A results in the inhibition of proliferation and induction of differentiation, and that U2OS cells transduced with RARalphaS77A suppresses tumor formation in nude mice. Moreover, using different human primary osteosarcoma cells and human mesenchymal stem cells for gene expression analysis, we found that either RA or RARalphaS77A induces many of the same differentiation response pathways and signaling molecules involved in U2OS cell differentiation. In addition, overexpression of the fibroblast growth factor 8f (FGF8f), one of the downstream targets induced by both RA and RARalphaS77A in U2OS cells, inhibits proliferation and induces expression of osteoblastic differentiation regulators. Hence, these data strongly suggest that RA-suppressed phosphorylation of RARalpha induces FGF8f expression to mediate differentiation response pathway in U2OS osteosarcoma cells.
尽管维甲酸（RA）是一种有效的试剂，可协调多种细胞类型的增殖抑制与分化，但 RA 介导的骨肉瘤细胞分化中的信号通路尚未阐明。在本研究中，我们表明，在人 U2OS 骨肉瘤细胞中，RA 处理或过表达磷酸化缺陷型突变体 RARalphaS77A 导致 RA 受体α（RARalpha）磷酸化减少，从而抑制增殖并诱导分化，并且转导 RARalphaS77A 的 U2OS 细胞抑制裸鼠肿瘤形成。此外，使用不同的人原发性骨肉瘤细胞和人间充质干细胞进行基因表达分析，我们发现 RA 或 RARalphaS77A 诱导许多相同的分化反应途径和信号分子参与 U2OS 细胞分化。此外，成纤维细胞生长因子 8f（FGF8f）的过表达，是 RA 和 RARalphaS77A 在 U2OS 细胞中诱导的下游靶标之一，抑制增殖并诱导成骨分化调节剂的表达。因此，这些数据强烈表明，RA 抑制的 RARalpha 磷酸化诱导 FGF8f 表达以介导 U2OS 骨肉瘤细胞中的分化反应途径。
