Induction of p53-Dependent Apoptosis by Prostaglandin A2.

Su-Been Lee,Sangsun Lee,Ho-Shik Kim,Sun-Young Lee,Ji-Young Park

doi:10.3390/biom10030492

Su-Been Lee, Sangsun Lee + Show 3 more

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https://doi.org/10.3390/biom10030492

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Journal: Biomolecules	Publication Date: Mar 24, 2020
Citations: 19	License type: CC BY 4.0

Affiliation: Catholic University of Korea, Naresuan University

Abstract

Prostaglandin (PG) A2, one of cyclopentenone PGs, is known to induce activation of apoptosis in various cancer cells. Although PGA2 has been reported to cause activation of apoptosis by altering the expression of apoptosis-related genes, the role of p53, one of the most critical pro-apoptotic genes, on PGA2-induced apoptosis has not been clarified yet. To address this issue, we compared the apoptosis in HCT116 p53 null cells (HCT116 p53-/-) to that in HCT116 cells containing the wild type p53 gene. Cell death induced by PGA2 was associated with phosphorylation of histone H2A variant H2AX (H2AX), activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase 1 in HCT116 cells. Induction of apoptosis in PGA2-treated cells was almost completely prevented by pretreatment with a pan-caspase inhibitor, z-VAD-Fmk, or an inhibitor of protein synthesis, cycloheximide. While PGA2 induced apoptosis in HCT116 cells, phosphorylation of p53 and transcriptional induction of p53-target genes such as p21WAF1, PUMA, BAX, NOXA, and DR5 occurred. Besides, pretreatment of pifithrin-α (PFT-α), a chemical inhibitor of p53’s transcriptional activity, interfered with the induction of apoptosis in PGA2-treated HCT116 cells. Pretreatment of NU7441, a small molecule inhibitor of DNA-activated protein kinase (DNA-PK) suppressed PGA2-induced phosphorylation of p53 and apoptosis as well. Moreover, among target genes of p53, knockdown of DR5 expression by RNA interference, suppressed PGA2-induced apoptosis. In the meanwhile, in HCT116 p53-/- cells, PGA2 induced apoptosis in delayed time points and with less potency. Delayed apoptosis by PGA2 in HCT116 p53-/- cells was also associated with phosphorylation of H2AX but was not inhibited by either PFT-α or NU7441. Collectively, these results suggest the following. PGA2 may induce p53-dependent apoptosis in which DNA-PK activates p53, and DR5, a transcriptional target of p53, plays a pivotal role in HCT116 cells. In contrast to apoptosis in HCT116 cells, PGA2 may induce apoptosis in a fashion of less potency, which is independent of p53 and DNA-PK in HCT116 p53-/- cells

Highlights

Tumor suppressor gene, p53, which is one of the most crucial tumor suppressor genes, exerts its anti-cancer effect by activating cell death, including apoptosis and autophagic cell death, as well as cell cycle arrest in cancer cells [1]
We attempted to observe the difference in the level of apoptosis between HCT116 cells and HCT116 p53-/- cells treated with PGA2
These data suggested that PGA2 induces caspase-dependent apoptosis in a p53-dependent manner in HCT116 cells

Summary

Introduction

P53, which is one of the most crucial tumor suppressor genes, exerts its anti-cancer effect by activating cell death, including apoptosis and autophagic cell death, as well as cell cycle arrest in cancer cells [1]. The intracellular level of p53 protein is negatively regulated by the ubiquitin-proteasome system (UPS). P53 is ubiquitinylated by MDM2, an E3 ubiquitin ligase, and degraded in the 26S proteasome, thereby keeping the level of p53 protein at the minimum. Increased p53, in turn, stimulates the transcription of numerous genes, including PUMA, NOXA, and BAX which can trigger apoptosis as well as p21WAF1, an inhibitor of CDK4/6, and CDK2, which blocks the cell cycle progression in late G1 phase. P53 is considered as the most critical transcription factor that induces apoptosis in cancer cells, which is reflected by the fact that most anti-cancer therapeutics, including chemotherapy and radiotherapy, induce apoptosis by activating p53 [1,7]

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