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 Hes1 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 in vitro 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.