Terpenoids from Zingiber officinale (Ginger) induce apoptosis in endometrial cancer cells through the activation of p53.

Yang Liu,Manish S Patankar,Rebecca J Whelan,Enkateswar Subudhi,Shitanshu Uppal,Mildred Felder,Noah Zucker,Bikash R Pattnaik,Arvinder Kapur,Kai Ludwig,Nick Claussen,Helen Rowland,David M Kushner,Abdelilah Aboussekhra

doi:10.1371/journal.pone.0053178

Abstract

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 IC50 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 IC50 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 p53neg 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.

Highlights

In the year 2011, approximately 8,010 women died due to endometrial cancer and nearly 47,130 patients were newly diagnosed with this cancer [1]
In the current study we demonstrate that the steam distilled extracts of ginger are potent mediators of apoptosis in endometrial cancer cells
We demonstrate that treatment of the endometrial cancer cells with the steam distilled extract of ginger results in significant increase in intracellular calcium, decrease in the mitochondrial membrane potential, increase in the expression of caspase 3, phosphorylation of P53, and a significant decrease in the expression of Bcl-2

Summary

Introduction

In the year 2011, approximately 8,010 women died due to endometrial cancer and nearly 47,130 patients were newly diagnosed with this cancer [1]. Combination regimens show higher response rates, but the progression free period with these therapies is relatively low (5–7 months) with higher morbidity and continued lack of cure [10] These statistics highlight the need for the development of novel and effective chemopreventive and chemotherapeutic agents for endometrial cancer. Our lab is currently investigating the anti-cancer properties of compounds present in the rhizomes of ginger (Zingiber officinale). These studies are supported by previous investigations demonstrating that dry ginger powder or solvent extracts of ginger roots induce cell cycle arrest and apoptosis in skin, breast, prostate, colon, and ovarian cancer cells [12,13,14,15,16,17]. Topical application of the ethanolic extract of ginger decreased the incidence, size, and the number of DMBA/TPA induced tumors in SENCAR mice [18]

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Conclusion