Rashad M Alghamdi,a
Mohammed A. Hassan,a,b
Mohammed Kaleem,a
Asaad Kayali,a
Majed A Halwani,c
Mazin A Zamzami,a,d
Hani Choudhry,a,d
Mahmoud Alhosin,a,d✽
a Biochemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia. b Department of Basic Medical Sciences, College of Medicine and Health Sciences, Hadhramout University, Mukalla, Yemen. c Nanomedicine Department, King Abdullah International Medical Research Center (KAIMRC), King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia. d Cancer Metabolism and Epigenetic Unit, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
Eur. J. Cell. Sci., Volume 2, Issue 1, pp. 20-26 (2020) Available online August 15th 2020
Abstract:
The tumor suppressor p73 is a member of p53 family and has a high degree of similarity with p53 function and structure. Like p53, p73 can also induce the expression of several genes involved in cell cycle and apoptosis. p73 expression is downregulated in many tumors by several mechanisms including the ubiquitination pathway. Thus, understanding the ubiquitin-proteasome pathway in p73 regulation will help in targeting this later and develop a new promising therapeutic strategy for cancer with p53 mutations. The aim of this study was to evaluate the effect of Thymoquinone (TQ), the major biologically active compound of the black seed oil on the expression of several E3 ubiquitin ligase enzymes known to be regulators of p73 and the related events in cancer cells with p53 mutation, such as the human acute lymphoblastic leukemia Jurkat cells, the human triple-negative breast cancer (MDA-MB-468 cells) and human promyelocytic leukemia HL60 cells. RNA-seq data showed that several E3 ubiquitin-ligase enzymes, well documented to be involved in the degradation of p73 including Itch, Pirh2, E3s Pin2, Mdm2, TRIM32 and SCFFBXO45 were downregulated in Jurkat cells. Among the target genes, Itch was significantly downregulated in TQ-treated Jurkat cells as compared with control cells. TQ-induced Itch downregulation was confirmed by real-time RT-PCR in Jurkat cells, MDA-MB-468 cells and HL60. Treating Jurkat cells with either TQ or the proteasome inhibitor MG132 induced an upregulation of p73. The present study indicates that TQ could be a promising inhibitor of the E3-ubiquitin ligase Itch leading to the upregulation of tumor suppressor p73 in cancers expressing mutant p53.