Background Fibroblast growth factor (FGF) and tumor growth factor-β (TGFβ) have emerged as pivotal regulators during the progression of osteosarcoma (OS). LHX9 is one crucial transcription factor controlled by FGF, however, its function in OS has not been investigated yet. Methods The expression of LHX9, FRS2, BMP4, TGF-beta R1, SMAD2, beta-catenin and metastasis-related proteins was measured by real-time quantitative PCR (RT-qPCR) and Western blot. CCK-8 assay and colony formation assay were employed to determine the proliferation of OS cells, while scratch wound healing assay and transwell assay were used to evaluate their migration and invasion, respectively. In vivo tumor growth and metastasis were determined by subcutaneous or intravenous injection of OS cells into nude mice. Results LHX9 expression was evidently up-regulated in OS tumor tissues and cell lines. Knockdown of LHX9 impaired the proliferation, migration, invasion and metastasis of OS cells. Mechanistically, LHX9 silencing led to the down-regulation of BMP-4, β-catenin and metastasis-related proteins, which was also observed in beta-catenin knockdown OS cells. By contrast, FRS2 knockdown conduced to the up-regulation of LHX9, BMP4, β-catenin and TGF-βR1, while TGF-beta inhibition repressed the expression of LHX9 and metastasis-related proteins. Additionally, let-7c modulates LHX9 and metastasis-related proteins by suppressing TGF-beta R1 expression on transcriptional level. Conclusions This study revealed LHX9 was essential for the proliferation, migration, invasion, and metastasis of OS cells via FGF and TGF-β/β-catenin signaling pathways.

中文翻译：

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FGF 诱导的 LHX9 通过 FRS2/TGF-β/β-catenin 通路调节骨肉瘤的进展和转移。

背景 成纤维细胞生长因子 (FGF) 和肿瘤生长因子-β (TGFβ) 已成为骨肉瘤 (OS) 进展过程中的关键调节因子。LHX9 是一种受 FGF 控制的关键转录因子，但其在 OS 中的功能尚未被研究。方法采用实时定量PCR（RT-qPCR）和Western blot检测LHX9、FRS2、BMP4、TGF-βR1、SMAD2、β-catenin及转移相关蛋白的表达。采用CCK-8测定和集落形成测定来确定OS细胞的增殖，而划痕伤口愈合测定和transwell测定分别用于评估它们的迁移和侵袭。通过将 OS 细胞皮下或静脉注射到裸鼠中来确定体内肿瘤的生长和转移。结果LHX9在OS肿瘤组织和细胞系中的表达明显上调。敲低 LHX9 会损害 OS 细胞的增殖、迁移、侵袭和转移。从机制上讲，LHX9 沉默导致 BMP-4、β-连环蛋白和转移相关蛋白的下调，这也在 β-连环蛋白敲低的 OS 细胞中观察到。相比之下，FRS2 敲低导致 LHX9、BMP4、β-连环蛋白和 TGF-βR1 的上调，而 TGF-β 抑制抑制 LHX​​9 和转移相关蛋白的表达。此外，let-7c 通过抑制转录水平上的 TGF-β R1 表达来调节 LHX9 和转移相关蛋白。结论 本研究揭示 LHX9 通过 FGF 和 TGF-β/β-catenin 信号通路对 OS 细胞的增殖、迁移、侵袭和转移至关重要。