The Notch Pathway Promotes Osteosarcoma Progression through Activation of Ephrin Reverse Signaling.

Despite significant advancements in the diagnosis and treatment of osteosarcoma, the molecular mechanisms underpinning disease progression remain unclear. This work presents strong clinical and experimental evidence demonstrating that Notch signaling contributes to osteosarcoma progression. First, using a cohort of 12 patients, Notch genes were upregulated in tumors compared with adjacent normal tissue, and high tumor expression of Notch1 intercellular domain (NICD1) and the Notch target gene correlated with poor chemotherapy response. Data mining of publicly available datasets confirmed that expression of Notch pathway genes is related to poor prognosis in osteosarcoma. On the basis of analysis, Notch signaling promoted osteosarcoma proliferation, enhanced chemoresistance, facilitated both migration and invasion, and upregulated stem cell-like characteristics. Xenograft models demonstrated that Notch signaling promotes primary tumor growth and pulmonary metastasis, and Notch inhibition is effective in reducing tumor size and preventing metastasis. Mechanistically, activated Notch signaling induces the expression of ephrinB1 and enhances the tumor-promoting ephrin reverse signaling. Overall, these findings provide functional evidence for Notch pathway genes as candidate biomarkers to predict prognosis in patients with osteosarcoma, and suggest a mechanistic rationale for the use of Notch inhibitors to treat osteosarcoma. IMPLICATIONS: The study provides preclinical evidence for Notch pathway as a molecular marker to predict osteosarcoma prognosis and as a therapeutic target against osteosarcoma. In addition, we identified a novel mechanism that ephrin reverse signaling acts as a key mediator of Notch pathway.