Novel strategies are necessary to improve
chemotherapy response in advanced and recurrent
endometrial cancer. Here, we demonstrate that
terpenoids present in the
Steam Distilled Extract of Ginger (SDGE) are potent inhibitors of proliferation of
endometrial cancer cells. SDGE, isolated from six different batches of ginger rhizomes, consistently inhibited proliferation of the
endometrial cancer cell lines Ishikawa and ECC-1 at IC(50) of 1.25 µg/ml. SDGE also enhanced the anti-proliferative effect of radiation and
cisplatin. Decreased proliferation of Ishikawa and ECC-1 cells was a direct result of SDGE-induced apoptosis as demonstrated by
FITC-
Annexin V staining and expression of cleaved
caspase 3. GC/MS analysis identified a total of 22 different
terpenoid compounds in SDGE, with the isomers
neral and
geranial constituting 30-40%.
Citral, a mixture of
neral and
geranial inhibited the proliferation of Ishikawa and ECC-1 cells at an IC(50) 10 µM (2.3 µg/ml). Phenolic compounds such as
gingerol and
shogaol were not detected in SDGE and
6-gingerol was a weaker inhibitor of the proliferation of the
endometrial cancer cells. SDGE was more effective in inducing
cancer cell death than
citral, suggesting that other
terpenes present in SDGE were also contributing to
endometrial cancer cell death. SDGE treatment resulted in a rapid and strong increase in intracellular
calcium and a 20-40% decrease in the mitochondrial membrane potential. Ser-15 of p53 was phosphorylated after 15 min treatment of the
cancer cells with SDGE. This increase in p53 was associated with 90% decrease in Bcl2 whereas no effect was observed on Bax. Inhibitor of p53,
pifithrin-α, attenuated the anti-
cancer effects of SDGE and apoptosis was also not observed in the p53(neg) SKOV-3 cells. Our studies demonstrate that
terpenoids from SDGE mediate apoptosis by activating p53 and should be therefore be investigated as agents for the treatment of
endometrial cancer.