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BRCA1/2-mutant cells are hypersensitive to inactivation of poly(ADP-ribose) polymerase 1 (PARP-1). We recently showed that inhibition of PARP-1 by NU1025 is strongly cytotoxic for BRCA1-positive BT-20 cells, but not BRCA1-deficient SKBr-3 cells. These results raised the possibility that other PARP-1 inhibitors, particularly those tested in clinical trials, may be more efficacious against BRCA1-deficient SKBr-3 breast cancer cells than NU1025. Thus, in the presented study the cytotoxicity of four PARP inhibitors under clinical evaluation (olaparib, rucaparib, iniparib and AZD2461) was examined and compared to that of NU1025. The sensitivity of breast cancer cells to the PARP-1 inhibition strongly varied. Remarkably, BRCA-1-deficient SKBr-3 cells were almost completely insensitive to NU1025, olaparib and rucaparib, whereas BRCA1-expressing BT-20 cells were strongly affected by NU1025 even at low doses. In contrast, iniparib and AZD2461 were cytotoxic for both BT-20 and SKBr-3 cells. Of the four tested PARP-1 inhibitors only AZD2461 strongly affected cell cycle progression. Interestingly, the anti-proliferative and pro-apoptotic potential of the tested PARP-1 inhibitors clearly correlated with their capacity to damage DNA. Further analyses revealed that proteomic signatures of the two studied breast cancer cell lines strongly differ, and a set of 197 proteins was differentially expressed in NU1025-treated BT-20 cancer cells. These results indicate that BT-20 cells may harbor an unknown defect in DNA repair pathway(s) rendering them sensitive to PARP-1 inhibition. They also imply that therapeutic applicability of PARP-1 inhibitors is not limited to BRCA mutation carriers but can be extended to patients harboring deficiencies in other components of the pathway(s)., (© 2015 Wiley Periodicals, Inc.)

Prostate cancer (PCa) displays infrequent point mutations, whereas genomic rearrangements are highly prevalent. In eukaryotes, the genome is compartmentalized into chromatin loop domains by the attachment to the nuclear matrix (NM), and it has been demonstrated that several recombination hot spots are situated at the base of loops. Here, we have characterized the binding between NM proteins and matrix attachment regions (MARs) in PCa. Nontumor and 44 PCa tissues were analyzed. More aggressive tumors were characterized by an increase in the complexity of the NM protein patterns that was synchronous with a decrease in the number of proteins binding the MAR sequences. PARP-1 was the protein that showed the most evident changes. The expression of the PARP-1 associated with NM increased and it was dependent on tumor aggressiveness. Immunohistochemical analysis showed that the protein was significantly overexpressed in tumor cells. To explore the role of PARP-1 in PCa progression, PCa cells were treated with the PARP inhibitor, ABT-888. In androgen-independent PC3 cells, PARP inhibition significantly decreased cell viability, migration, invasion, chromatin loop dimensions and histone acetylation. Collectively, our study provides evidence that MAR-binding proteins are involved in the development and progression of PCa. PARP could play a key role in the compartmentalization of chromatin and in the development of the more aggressive phenotype. Thus, PARP can no longer be viewed only as an enzyme involved in DNA repair, but that its role in chromatin modulation could provide the basis for a new therapeutic approach to the treatment of PCa., (© 2015 UICC.)

Background: We have isolated a mycobacterial cell wall-DNA complex (MCC) possessing anti-cancer activity against bladder cancer cells. The anti-cancer activity of MCC appears to be due to two effects: a direct interaction with bladder cancer cells resulting in the induction of apoptosis and an indirect effect via the stimulation of monocytes and macrophages cytokine synthesis. In this study, the direct effect of MCC towards LNCaP cancer cells was evaluated., Methods: Inhibition of proliferation, cell cycle arrest and induction of apoptosis were evaluated in vitro using LNCaP cells treated with MCC. The synthesis of IL-12, GM-CSF, and TNF-alpha by LNCaP cells in response to MCC was also determined. Experiments were performed to gain insight into the mechanism of action of MCC towards LNCaP cells., Results: MCC caused a dose-dependent inhibition of the proliferation of LNCaP cells that was associated with cell cycle arrest at the G0/G1 phase. MCC-induced apoptosis of LNCaP cells was consistent with a mitochondrial pathway involving mitochondrial disruption, release of cytochrome c, and an increase in Bax protein levels leading to caspase-3 and -7 activation and cleavage of poly (ADP-ribose) polymerase and nuclear mitotic apparatus protein. Surprisingly, MCC also directly induced the synthesis of IL-12 and GM-CSF, but not TNF-alpha, by LNCaP cells., Conclusions: MCC possesses the ability to directly induce apoptosis of LNCaP cells and to trigger the synthesis of IL-12 and GM-CSF by these cells, suggesting a potential role of MCC for the treatment of prostate cancer., (Copyright 2001 Wiley-Liss, Inc.)

To gain insight into the gene regulation and signal transduction effects of active oxygen in tumour promotion and progression, we studied the effect of active oxygen generated extracellularly by xanthine/xanthine oxidase (X/XO) in promotion-insensitive (P-), promotion-sensitive (P+) and transformed (Tx) mouse epidermal JB6 cells. Active oxygen inhibited growth, particularly of P- cells and increased poly ADPR transferase activity and PKC activity more significantly in P- cells. No phenotypic differences in the distribution pattern of PKC isotypes alpha, beta and gamma were seen in JB6 cells. PKC alpha was expressed abundantly, whereas beta and gamma were not detected. Basal levels of the antioxidant enzymes catalase and CuZn. Superoxide dismutase were higher in P+ and Tx cells. X/XO resulted in an initial decrease in the activity of these enzymes, followed by recovery or transient induction in Tx and P+ cells. X/XO induced c-myc and c-fos expression in JB6 cells, with c-fos induction being more pronounced in P- cells, whereas a biphasic increase in c-jun was seen in P+ cells. These early genes may play a role in proliferation whereas post-translational poly ADP-ribosylation and, perhaps, phosphorylation suggest a genetic-epigenetic mechanism in oxidant tumour promotion and progression.

Two studies were conducted to determine whether Pseudomonas aeruginosa exoenzyme expression was increased during pulmonary exacerbations of cystic fibrosis (CF) and if it was reduced by antibiotic therapy. The first study was retrospective comparing in vitro exoenzyme levels expressed by P. aeruginosa sputum isolates from seriously ill, hospitalized patients with CF to those from P. aeruginosa strains isolated from CF clinic patients who were in relatively better health. Exoenzyme values were significantly greater in P. aeruginosa strains isolated from ill, hospitalized patients than in clinic patients (P = 0.0001). In the prospective study, in vitro exoenzyme levels were measured from sputum P. aeruginosa isolates of 9 hospitalized patients with CF. Exoenzyme values were greatest in nonmucoid strains on admission (P < 0.0025), and P. aeruginosa exoenzyme expression decreased significantly during hospitalization (P < 0.0025). Deterioration in CF lung disease was accompanied by increased P. aeruginosa exoenzyme production, especially by nonmucoid strains. Antibiotic treatment during hospitalization resulted in mean improvement of % predicted forced expiratory volume in 1 sec (FEV1) from 39 to 53% (P = 0.002). Thus, antibiotics may improve pulmonary function in patients with CF by decreasing P. aeruginosa exoenzyme expression.

To analyze the temporal relationship of poly(adenosine diphosphate [ADP]-ribosylation) signal with DNA replication and cell divisions, the effect of 3 aminobenzamide (3ABA), an inhibitor of the poly(ADP-ribose)synthetase, was determined in vivo during the first cleavage division of sea urchins. The incorporation of 3H-thymidine into DNA was monitored and cleavage division was examined by light microscopy. The poly(ADP-ribose) neosynthesized on CS histone variants was measured by labeling with 3H-adenosine during the two initial embryonic cell cycles and the inhibitory effect of 3ABA on this poly(ADP-ribosylation) was determined. The results obtained indicate that the CS histone variants are poly(ADP-ribosylated) de novo during the initial cell cycles of embryonic development. The synthesis of poly(ADP-ribose) is decreased but not abolished by 20 mM of 3ABA. The incubation of zygotes in 3ABA at the entrance into S1 phase decreased 3H-thymidine incorporation into DNA in phase S2, while S1 was unaltered. Alternatively, when the same treatment was applied to zygotes at the exit of S1 phase, a block of the first cleavage division and a retardation of S2 phase were observed. The inhibitory effect of 3ABA on both DNA replication and cell division was totally reversible by a release of the zygotes from this inhibition. Taking together these observations it may be concluded that the poly(ADP-ribosylation) signals related to embryonic DNA replication are not contemporaneous with S phase progression but are a requirement before its initiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Poly ADP-ribosylation is a post-translational modification of chromatin proteins catalyzed by the enzyme poly-ADPR transferase (poly-ADPRT) and affects the structure as well as the functional properties of chromatin. It is of particular relevance in carcinogenesis, as it represents an epigenetic mechanism for modulation of gene expression. In the present study, A431 cells were exposed to tumor promoters phorbol-12-myristate-13-acetate (PMA), benzoyl peroxide (BP), mezerein and 6-keto-lithocholic acid (KA), and their effect on poly-ADP-ribosylation was studied. All these tumor promoters increased the activity of poly-ADPRT in these cells--PMA 2.3-fold, BP and mezerein 2.2-fold each and KA 1.3-fold. The enzyme inhibitor 3-amino benzamide (3AB) partially prevented the stimulation of poly-ADPRT by these promoters. There was a concomitant decrease in NAD levels, the substrate for poly-ADPRT. The decrease was 44% for PMA, 46% for BP, 21% for KA and 34% for mezerein. The induction of poly-ADP-ribose synthesis by PMA and BP appears to be mediated at least in part by active oxygen species, as they induced an increase in superoxide anions and anti-oxidants prevented the increase of poly-ADPRT activity to varying extents.