Poly(ADP-ribose) polymerase signaling of topoisomerase 1-dependent DNA damage in carcinoma cells

Abstract

A molecular approach to enhance the antitumour activity of Topoisomerase 1 (TOP1) inhibitors relies on the use of chemical inhibitors of poly(ADP-ribose)polymerases (PARP). Poly(ADP-ribosyl)ation is involved in the regulation of many cellular processes such as DNA repair, cell cycle progression and cell death. Recent findings showed that poly(ADP-ribosyl)ated PARP-1 and PARP-2 counteract camptothecin action facilitating resealing of DNA strand breaks. Moreover, repair of DNA strand breaks induced by poisoned TOP1 is slower in the presence of PARP inhibitors, leading to increased toxicity.In the present study we compared the effects of the camptothecin derivative Topotecan (TPT), and the PARP inhibitor PJ34, in breast (MCF7) and cervix (HeLa) carcinoma cells either PARP-1 proficient or silenced, both BRCA1/2 +/+ and p53 +/+ .HeLa and MCF7 cell lines gave similar results: i) TPT-dependent cell growth inhibition and cell cycle perturbation were incremented by the presence of PJ34 and a 2 fold increase in toxicity was observed in PARP-1 stably silenced HeLa cells; ii) higher levels of DNA strand breaks were found in cells subjected to TPT+PJ34 combined treatment; iii) PARP-1 and -2 modification was evident in TPT-treated cells and was reduced by TPT+PJ34 combined treatment; iv) concomitantly, a reduction of soluble/active TOP1 was observed. Furthermore, TPT-dependent induction of p53, p21and apoptosis were found 24-72 h after treatment and were increased by PJ34 both in PARP-1 proficient and silenced cells. The characterization of such signaling network can be relevant to a strategy aimed at overcoming acquired chemoresistance to TOP1inhibitors.

Altered Processing of Amyloid Precursor Protein in Cells Undergoing Apoptosis

“…Western blot analysis of the lysates from H4-APP cells treated with CPT showed a time-dependent increase in p53 levels, suggesting that the cell death we observed is p53-dependent (Figure 1E, top panel). Next, we examined the levels of poly-ADP ribose polymerase (PARP), an enzyme involved in several cellular functions including DNA repair, cell cycle progression, and cell death [30], [31], in cells treated with CPT. PARP is an approximately 116 kDa protein which, under apoptotic conditions, gets cleaved by caspases to generate fragments of approximately 89 kDa and 24 kDa [32].…”

Inhibition of Poly(ADP-Ribose) Polymerase Enhances Radiochemosensitivity in Cancers Proficient in DNA Double-Strand Break Repair

“…As anticipated, blockade of PARP by ABT-888 led to increased radiochemotherapy cytotoxicity. The lethal effects of PARP inhibition were more pronounced when cells were challenged to correct topotecan-poisoned replication forks, an observation likely linked to conversion of tolerable single-strand nicks to lethal double-strand breaks [30,31]. This work stands out by demonstrating enhanced cell death by IR or topotecan with PARP inhibition in cells having an augmented chance of repairing DNA readily as a consequence of a high deoxynucleotide output from RNR.…”

The polypyrimidine/polypurine motif in the mouse mu opioid receptor gene promoter is a supercoiling-regulatory element

“…The existence of diverse topological isomers of pBMPPy/u-AS suggests that the mouse MOR PPy/u element could drive DNA transactions such as DNA damage repair, while the human MOR PPy/u element is normally religated without activating DNA damage-coupled transcription. Indeed, DNA damage in cells induces many genes whose products facilitate DNA repair (D’Onofrio et al, 2011). Poly(ADP-ribose) polymerase (PARP) is a nuclear protein that recognizes DNA lesions and protects cells against the genome-destabilizing effects of DNA damage.…”