Phyllostachys edulis extract induces apoptosis signaling in osteosarcoma cells, associated with AMPK activation

Bamboo is distributed worldwide, and its different parts are used as foods or as a traditional herb. Recently, antitumoral effects of bamboo extracts on several tumors have been increasingly reported; however, antitumoral activity of bamboo extracts on osteosarcoma remains unclear. In the present study, we investigated effects of an aqueous Phyllostachys edulis leaf extract (PEE) on osteosarcoma cells and the underlying mechanism of inhibition.

The growth of human osteosarcoma cell lines 143 B and MG-63 and lung fibroblast MRC-5 cells was determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Apoptosis was demonstrated using TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay and flow cytometric analysis. Phosphorylation and protein levels were determined by immunoblotting.

After treatment with PEE, viability of 143 B and MG-63 cells was dose-dependently reduced to 36.3% ± 1.6% of control values, which were similar to AICAR (5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside) treatments. In parallel, ratios of apoptotic cells and cells in the sub-G1 phase were significantly increased. Further investigation showed that PEE treatments led to activation of caspase cascades and changes of apoptotic mediators Bcl2, Bax, and p53. Consistently, our results revealed that PEE activated adenosine monophosphate-activated protein kinase (AMPK) signaling, and the AMPK activation was associated with the induction of apoptotic signaling.

Our results indicated that PEE suppressed the growth of 143 B and MG-63 cells but moderately affected MRC-5 cells. PEE-induced apoptosis may attribute to AMPK activation and the following activation of apoptotic signaling cascades. These findings revealed that PEE possesses antitumoral activity on human osteosarcoma cells by manipulating AMPK signaling, suggesting that PEE alone or combined with regular antitumor drugs may be beneficial as osteosarcoma treatments.