Nimbolide is a
tetranortriterpenoid isolated from the leaves and flowers of Azadirachta indica which has been shown to exhibit anticancer,
antioxidant, anti-inflammatory, and anti-invasive properties in a variety of
cancer cells. However, the anti-
tumor effect on human
renal cell carcinoma (RCC) cells is unknown. In this study, we found that
nimbolide treatment had a cytotoxic effect on 786-O and A-498 RCC cells in a dose-dependent manner. According to flow cytometric analysis,
nimbolide treatment resulted in G2/M arrest in 786-O and A-498 cells accompanied with an increase in the phosphorylation status of p53, cdc2, cdc25c, and decreased expressions of
cyclin A,
cyclin B, cdc2, and cdc25c.
Nimbolide also caused DNA damage in a dose-dependent manner as determined by comet assay and measurement of γ-H2AX. In addition, apoptotic cells were observed in an
Annexin V-FITC/
propidium iodide double-stained assay. The activities of
caspase-3, -9, and
poly ADP-ribose polymerase (PARP) were increased, and the expression of
pro-caspase-8 was decreased in
nimbolide-treated 786-O and A-498 cells. Western blot analysis revealed that the levels of intrinsic-related apoptotic
proteins Bax and extrinsic-related
proteins (DR5, CHOP) were significantly increased in
nimbolide-treated 786-O and A-498 cells. In addition, the expressions of Bcl-2 and Mcl-1 were decreased in 786-O and A-498 cells after
nimbolide treatment. We conclude that
nimbolide can inhibit the growth of human RCC cells by inducing G2/M phase arrest by modulating cell cycle-related
proteins and cell apoptosis by regulating intrinsic and extrinsic
caspase signaling pathways.
Nimbolide may be a promising therapeutic strategy for the treatment of RCC.