Thymoquinone Selectively Induces Hepatocellular Carcinoma Cell Apoptosis in Synergism With Clinical Therapeutics and Dependence of p53 Status

Shah Jehan,Chen Zhong,Guangyue Li,Dangdang Li,Guangchao Sui,Syed Zulqarnain Bakhtiar

doi:10.3389/fphar.2020.555283

Abstract

Thymoquinone (TQ) is a natural compound extracted from the black seeds of Nigella sativa Linn. belonging to the Ranunculaceae family. TQ exhibits anti-inflammatory and antineoplastic activities against various cancers. Many therapeutics in hepatocellular carcinoma (HCC) treatments, such as doxorubicin (DOX) and cisplatin (DDP), exhibit considerable side effects on patients. We investigated cytotoxic effects of TQ, alone or in combination with DDP and DOX to HCC cells. TQ exhibited selective killing to HCC HepG2 and SMMC-7721 cells, but relatively low toxicity to normal liver HL-7702 cells. Importantly, when used with DOX or DDP, TQ showed synergistic inhibition of HCC cells, but not HL-7702 cells. We also discovered that Hep3B cells with a p53 null status were more sensitive to TQ than HepG2 and SMMC-7721 cells harboring wild type p53. Consistently, shRNA-mediated p53 silencing in HepG2 cells dramatically enhanced TQ-induced apoptosis, measured by caspase 3 and PARP cleavage. Furthermore, TQ-stimulated increase of reactive oxygen species (ROS) in p53-depleted cells was more pronounced than that in cells with intact p53. In summary, we discovered that TQ synergistically improves the anti-cancer activity of DOX and DDP, and loss of p53 sensitizes HCC cells to TQ-induced apoptosis.

Highlights

Hepatocellular carcinoma (HCC) is the fifth common malignancy and the third cancer-related cause of death in the world (Elkhoely et al, 2015; Gnutzmann et al, 2018)
30% to 40% of HCC patients can be treated with curative approaches, Abbreviations: DCFH-DA, 2’,7’-dichlorodihydrofluorescein diacetate; DDP, cisplatin; DMSO, dimethyl sulfoxide; DOX, doxorubicin hydrochloride; HCC, hepatocellular carcinoma; NAC, N-acetylcysteine; PI, propidium iodide; ROS, reactive oxygen species; TQ, thymoquinone
Our study revealed that TQ significantly boosted the antineoplastic activities of DDP and DOX. These combinatorial treatments strongly induced apoptosis of HCC cells by caspase activation, but exhibited relatively low cytotoxicity to normal liver cells compared to that observed with conventional therapeutics alone

Summary

Introduction

Hepatocellular carcinoma (HCC) is the fifth common malignancy and the third cancer-related cause of death in the world (Elkhoely et al, 2015; Gnutzmann et al, 2018). 30% to 40% of HCC patients can be treated with curative approaches, Abbreviations: DCFH-DA, 2’,7’-dichlorodihydrofluorescein diacetate; DDP, cisplatin; DMSO, dimethyl sulfoxide; DOX, doxorubicin hydrochloride; HCC, hepatocellular carcinoma; NAC, N-acetylcysteine; PI, propidium iodide; ROS, reactive oxygen species; TQ, thymoquinone. The last two options are considered to be useful and curative treatments for liver cancers, but only 15% of the patients are suitable to them because the majority are usually diagnosed at late stages (Roxburgh and Evans, 2008). Novel chemotherapeutic agents or strategies are urgently needed to treat liver cancer patients with minimal or tolerable side effects (Ashour et al, 2014)

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Conclusion