Punicalagin inhibited proliferation, invasion and angiogenesis of osteosarcoma through suppression of NF-κB signaling

Osteosarcoma is the most common primary malignant bone tumor among children and young people and is associated with poor prognosis. Punicalagin is an antioxidant ellagitannin found in pomegranate juice with known antiproliferation and anti-angiogenesis properties. However, the antitumor effect of punicalagin on osteosarcoma requires further investigation. In the present study, the inhibitory effect of punicalagin on proliferation and invasion was evaluated in one human osteoblast cell line (hFOB1.19) and three human osteosarcoma cell lines (U2OS, MG63 and SaOS2). The cancer cell apoptosis ratio was determined using flow cytometry. NF-κB signaling in these cells was also evaluated using western blotting analysis. A subcutaneous tumor xenograft model was initiated to study the efficacy of punicalagin on osteosarcoma development and angiogenesis in vivo. Punicalagin treatment significantly decreased osteosarcoma cell proliferation and increased apoptosis. In addition, the invasion potential of these cells in a transwell assay was also dramatically suppressed in osteosarcoma cells. Punicalagin not only induced the degradation of IκBα but also the nuclear translocation of p65, suggesting the attenuation of NF-κB signaling pathway following treatment. Moreover, punicalagin markedly downregulated interleukin (IL)-6 and IL-8 levels, which was consistent with the inhibition of NF-κB signaling. An NF-κB activator could reverse these effects. Using a tumor xenograft mouse model, it was demonstrated that punicalagin exposure inhibited osteosarcoma growth and angiogenesis in vivo. These observations confirmed the suppressive effect of punicalagin against osteosarcoma malignancies. The underlying molecular mechanisms may include inhibition of the NF-κB signaling pathway.