Poly (ADP-ribose): A double-edged sword governing cancer cell survival and death

Poly(ADP-ribose)(PAR),a polymer of ADP-ribose,is synthesized by PAR po-lymerase and is crucial for the survival of cancer cells due to its vital functions in DNA repair and post-translational modifications.Beyond its supportive role,PAR also triggers cancer cell death by excessive accumulation of PAR leading to an energy crisis and parthanatos.This phenomenon underscores the potential of targeting PAR regulation as a novel anticancer strategy,and the rationale would present an engaging topic in the field of anticancer research.Therefore,this editorial provides an overview of the mechanisms determining cancer cell fate,emphasizing the central role of PAR.It further introduces promising methods for modulating PAR concentrations that may pave the way for innovative anticancer therapies.

Chrysophanol protects against doxorubicin-induced cardiotoxicity by suppressing cellular PARylation

The clinical application of doxorubicin(DOX) in cancer chemotherapy is limited by its lifethreatening cardiotoxic effects. Chrysophanol(CHR), an anthraquinone compound isolated from the rhizome of Rheum palmatum L., is considered to play a broad role in a variety of biological processes.However, the effects of CHR’s cardioprotection in DOX-induced cardiomyopathy is poorly understood. In this study, we found that the cardiac apoptosis, mitochondrial injury and cellular PARylation levels were significantly increased in H9 C2 cells treated by Dox, while these effects were suppressed by CHR. Similar results were observed when PARP1 activity was suppressed by its inhibitors 3-aminobenzamide(3 AB)and ABT888. Ectopic expression of PARP1 effectively blocked this CHR’s cardioprotection against DOX-induced cardiomyocyte injury in H9 C2 cells. Furthermore, pre-administration with both CHR and 3 AB relieved DOX-induced cardiac apoptosis, mitochondrial impairment and heart dysfunction in Sprague–Dawley rat model. These results revealed that CHR protects against DOX-induced cardiotoxicity by suppressing cellular PARylation and provided critical evidence that PARylation may be a novel target for DOX-induced cardiomyopathy.

Inhibition of poly(ADP-Ribose)polymerase:A promising strategy targeting pancreatic cancer with BRCAness phenotype

The use of chemotherapeutic regimens for the treatment of pancreatic cancer is still limited because pancreatic cancer is usually diagnosed at an advanced stage as a refractory disease in which symptoms are difficult to recognize in the early stages.Furthermore,at advanced stages,there are important challenges to achieve clinical benefit and symptom resolution,even with the use of an expanded spectrum of anticancer drugs.Recently,a point of reduced susceptibility to conventional chemotherapies by breast cancer susceptibility gene(BRCA)mutations led to a new perspective for overcoming the resistance of pancreatic cancer within the framework of increased genome instability.Poly(ADP-Ribose)polymerase(PARP)-1 is an enzyme that can regulate intrinsic functions,such as response to DNA damage.Therefore,in an environment where germline mutations in BRCAs(BRCAness)inhibit homologous recombination in DNA damage,resulting in a lack of DNA damage response,a key role of PARP-1 for the adaptation of the genome instability could be further emphasized.Here,we summarized the key functional role of PARP-1 in genomic instability of pancreatic cancer with the BRCAness phenotype and listed clinical applications and outcomes of PARP-1 inhibitors to highlight the importance of targeting PARP-1 activity.

The poly(ADP-ribosyl)ation of BRD4 mediated by PARP1 promoted pathological cardiac hypertrophy

The bromodomain and extraterminal(BET)family member BRD4 is pivotal in the pathogenesis of cardiac hypertrophy.BRD4 induces hypertrophic gene expression by binding to the acetylated chromatin,facilitating the phosphorylation of RNA polymerases II(Pol II)and leading to transcription elongation.The present study identified a novel post-translational modification of BRD4:poly(ADPribosyl)ation(PARylation),that was mediated by poly(ADP-ribose)polymerase-1(PARP1)in cardiac hypertrophy.BRD4 silencing or BET inhibitors JQ1 and MS417 prevented cardiac hypertrophic responses induced by isoproterenol(ISO),whereas overexpression of BRD4 promoted cardiac hypertrophy,confirming the critical role of BRD4 in pathological cardiac hypertrophy.PARP1 was activated in ISOinduced cardiac hypertrophy and facilitated the development of cardiac hypertrophy.BRD4 was involved in the prohypertrophic effect of PARP1,as implied by the observations that BRD4 inhibition or silencing reversed PARP1-induced hypertrophic responses,and that BRD4 overexpression suppressed the antihypertrophic effect of PARP1 inhibitors.Interactions of BRD4 and PARP1 were observed by coimmunoprecipitation and immunofluorescence.PARylation of BRD4 induced by PARP1 was investigated by PARylation assays.In response to hypertrophic stimuli like ISO,PARylation level of BRD4 was elevated,along with enhanced interactions between BRD4 and PARP1.By investigating the PARylation of truncation mutants of BRD4,the C-terminal domain(CTD)was identified as the PARylation modification sites of BRD4.PARylation of BRD4 facilitated its binding to the transcription start sites(TSS)of hypertrophic genes,resulting in enhanced phosphorylation of RNA Pol II and transcription activation of hypertrophic genes.The present findings suggest that strategies targeting inhibition of PARP1-BRD4 might have therapeutic potential for pathological cardiac hypertrophy.