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

Cabozantinib Reverses Topotecan Resistance in Human Non-Small Cell Lung Cancer NCI-H460/TPT10 Cell Line and Tumor Xenograft Model

Cabozantinib (CBZ) is a small molecule tyrosine kinase receptor inhibitor, which could also inhibit the ABCG2 transporter function. Therefore, CBZ could re-sensitize cancer cells that are resistant to ABCG2 substrate drugs including topotecan (TPT). However, its reversal effect against TPT resistance has not been tested in a TPT-induced resistant cancer model. In this study, a new TPT selected human non-small cell lung cancer (NSCLC)-resistant cell model NCI-H460/TPT10 with ABCG2 overexpression and its parental NCI-H460 cells were utilized to investigate the role of CBZ in drug resistance. The in vitro study showed that CBZ, at a non-toxic concentration, could re-sensitize NCI-H460/TPT10 cells to TPT by restoring intracellular TPT accumulation via inhibiting ABCG2 function. In addition, the increased cytotoxicity by co-administration of CBZ and TPT may be contributed by the synergistic effect on downregulating ABCG2 expression in NCI-H460/TPT10 cells. To further verify the applicability of the NCI-H460/TPT10 cell line to test multidrug resistance (MDR) reversal agents in vivo and to evaluate the in vivo efficacy of CBZ on reversing TPT resistance, a tumor xenograft mouse model was established by implanting NCI-H460 and NCI-H460/TPT10 into nude mice. The NCI-H460/TPT10 xenograft tumors treated with the combination of TPT and CBZ dramatically reduced in size compared to tumors treated with TPT or CBZ alone. The TPT-resistant phenotype of NCI-H460/TPT10 cell line and the reversal capability of CBZ in NCI-H460/TPT10 cells could be extended from in vitro cell model to in vivo xenograft model. Collectively, CBZ is considered to be a potential approach in overcoming ABCG2-mediated MDR in NSCLC. The established NCI-H460/TPT10 xenograft model could be a sound clinically relevant resource for future drug screening to eradicate ABCG2-mediated MDR in NSCLC.

PARP inhibitors and epithelial ovarian cancer: Molecular mechanisms, clinical development and future prospective

Epithelial ovarian cancer (EOC) has a poor prognosis. Since the introduction of paclitaxel as antineoplastic agent >20 years ago, only a few phase III randomized trials have shown challenging data regarding different therapeutic options for facing its aggressive clinical course and granting active therapies to patients. Different studies have shown the utility of poly(ADP-ribose) polymerase (PARP) inhibitors in women with EOC with or without BRCA mutations, both germline and somatic. Three PARP inhibitors, olaparib, rucaparib and niraparib, have been recently approved by the Food and Drug Administration for clinical use in EOC patients, though with different clinical indications and profiles of toxicity, while two other molecules, veliparib and talazoparib, are still under clinical investigation. The aim of the present paper is to evaluate the current status of PARP inhibitors in terms of molecular activity, pharmacodynamic properties and clinical applications.

An integrated study on antimicrobial activity and ecotoxicity of quantum dots and quantum dots coated with the antimicrobial peptide indolicidin

This study attempts to evaluate the antimicrobial activity and the ecotoxicity of quantum dots (QDs) alone and coated with indolicidin. To meet this objective, we tested the level of antimicrobial activity on Gram-positive and Gram-negative bacteria, and we designed an ecotoxicological battery of test systems and indicators able to detect different effects using a variety of end points. The antibacterial activity was analyzed against Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 1025), Escherichia coli (ATCC 11229), and Klebsiella pneumoniae (ATCC 10031), and the results showed an improved germicidal action of QDs-Ind. Toxicity studies on Daphnia magna indicated a decrease in toxicity for QDs-Ind compared to QDs alone, lack of bioluminescence inhibition on Vibrio fisheri, and no mutations in Salmonella typhimurium TA 100. The comet assay and oxidative stress experiments performed on D. magna showed a genotoxic and an oxidative damage with a dose-response trend. Indolicidin retained its activity when bound to QDs. We observed an enhanced activity for QDs-Ind. The presence of indolicidin on the surface of QDs was able to decrease its QDs toxicity.

Automodification of PARP and fatty acid-based membrane lipidome as a promising integrated biomarker panel in molecular medicine

AIM

Establishing by statistical analyses whether the analyses of auto-modified poly(ADP-ribose)polymerase and erythrocyte membrane fatty acid composition (Fat Profile(®)), separately or in tandem, help monitoring the physio-pathology of the cell, and correlate with diseases, if present.

PATIENTS & METHODS

Ninety five subjects were interviewed and analyzed blindly. Blood lymphocytes and erythrocytes were prepared to assay poly(ADP-ribose)polymerase automodification and fatty acid based membrane lipidome, respectively.

RESULTS

Poly(ADP-ribose)polymerase automodification levels confirmed their correlation with DNA damage extent, and allowed monitoring disease activity, upon surgical/therapeutic treatment. Membrane lipidome profiles showed lipid unbalance mainly linked to inflammatory states. Statistically both tests were separately significant, and correlated each other within some pathologies.

CONCLUSION

In the laboratory routine, both tests, separately or in tandem, might be a preliminary and helpful step to investigate the occurrence of a given disease. Their combination represents a promising integrated panel for sensible, noninvasive and routine health monitoring.

A phase I-II evaluation of veliparib (NSC #737664), topotecan, and filgrastim or pegfilgrastim in the treatment of persistent or recurrent carcinoma of the uterine cervix: an NRG Oncology/Gynecologic Oncology Group study

PURPOSE

The aim of this study was to evaluate the tolerability and efficacy of poly(ADP-ribose) polymerase (PARP) inhibition by veliparib during cytotoxic topotecan administration with filgrastim or pegfilgrastim neutrophil support in women with persistent or recurrent uterine cervix cancer.

EXPERIMENTAL DESIGN

This phase I-II trial examined twice-daily oral veliparib (10 mg) given during once-daily intravenous topotecan (0.6 mg/m²) on days 1 to 5 of each treatment cycle. Cycles were repeated every 21 days until disease progression or until toxicity prohibited further therapy. Toxicity and objective response rate were primary endpoints.

RESULTS

Twenty-seven women were enrolled. Frequently reported grade 3 or higher treatment-related toxicities were anemia (59%), thrombocytopenia (44%), leukopenia (22%), and neutropenia (19%). There were 2 partial responses (7% [90% confidence interval, 1%-22%]). Four patients had a disease progression date more than 6 months after the start of veliparib-topotecan therapy. Patients with low immunohistochemical expression (0-1+) of PARP-1 in their primary uterine cervix cancer were more likely to have a longer progression-free interval (hazard ratio, 0.25; P = 0.02) and survival (hazard ratio, 0.12; P = 0.005) after veliparib-topotecan therapy.

CONCLUSIONS

Clinical activity of a veliparib-topotecan combination was minimal in women with persistent or recurrent uterine cervix cancer. Women whose uterine cervix cancers express PARP-1 at low levels may benefit preferentially from PARP inhibitors combined with cytotoxic therapies, suggesting further study of PARP expression as an integral triage biomarker.

Effect of poly(ADP-ribose)polymerase and DNA topoisomerase I inhibitors on the p53/p63-dependent survival of carcinoma cells

Depending on their genetic background (p53(wt) versus p53(null)), carcinoma cells are more or less sensitive to drug-induced cell cycle arrest and/or apoptosis. Among the members of the p53 family, p63 is characterized by two N-terminal isoforms, TAp63 and ΔNp63. TAp63 isoform has p53-like functions, while ΔNp63 acts as a dominant negative inhibitor of p53. We have previously published that TAp63 is involved in poly(ADP-ribose)polymerase-1 (PARP-1) signaling of DNA damage deriving from DNA topoisomerase I (TOP I) inhibition in carcinoma cells. In the present study, we treated MCF7 breast carcinoma cells (p53(+)/ΔNp63(-)) or SCC022 (p53(-)/ΔNp63(+)) squamous carcinoma cells with the TOP I inhibitor topotecan (TPT) and the PJ34 PARP inhibitor, to compare their effects in the two different cell contexts. In MCF7 cells, we found that PJ34 addition reverts TPT-dependent PARP-1 auto-modification and triggers caspase-dependent PARP-1 proteolysis. Moreover, TPT as single agent stimulates p53(ser15) phosphorylation, p53 PARylation and occupancy of the p21WAF promoter by p53 resulting in an increase of p21WAF expression. Interestingly, PJ34 in combination with TPT enhances p53 occupancy at the BAX promoter and is associated with increased BAX protein level. In SCC022 cells, instead, TPT+PJ34 combined treatment reduces the level of the anti-apoptotic ΔNp63α protein without inducing apoptosis. Remarkably, in such cells, either exogenous p53 or TAp63 can rescue the apoptotic program in response to the treatment. All together our results suggest that in cancer cells PARP inhibitor(s) can operate in the choice between growth arrest and apoptosis by modulating p53 family-dependent signal.

Biosorption and biodegradation of triphenyltin by Stenotrophomonas maltophilia and their influence on cellular metabolism

Triphenyltin (TPT), an endocrine disruptor, is polluting the global environment through its worldwide use. However, information concerning the mechanisms of TPT biodegradation and cellular metabolism is severely limited. Therefore, these processes were elucidated through experiments involving TPT biosorption and degradation, intracellular metabolite analysis, nutrient use, ion and monosaccharide release, cellular membrane permeability and protein concentration quantification. The results verified that TPT was initially adsorbed by the cell surface of Stenotrophomonas maltophilia and was subsequently transported and degraded intracellularly with diphenyltin and monophenyltin production. Cl(-), Na(+), arabinose and glucose release, membrane permeability and the extracellular protein concentration increased during TPT treatment, whereas K(+) and PO4(3-) utilization and intracellular protein concentration declined. The biosorption, degradation and removal efficiencies of TPT at 0.5mgL(-1) by 0.3gL(-1) viable cells at 10 d were 3.8, 77.8 and 86.2%, respectively, and the adsorption efficiency by inactivated cells was 72.6%.

Tyrosyl-DNA-phosphodiesterases (TDP1 and TDP2)

TDP1 and TDP2 were discovered and named based on the fact they process 3'- and 5'-DNA ends by excising irreversible protein tyrosyl-DNA complexes involving topoisomerases I and II, respectively. Yet, both enzymes have an extended spectrum of activities. TDP1 not only excises trapped topoisomerases I (Top1 in the nucleus and Top1mt in mitochondria), but also repairs oxidative damage-induced 3'-phosphoglycolates and alkylation damage-induced DNA breaks, and excises chain terminating anticancer and antiviral nucleosides in the nucleus and mitochondria. The repair function of TDP2 is devoted to the excision of topoisomerase II- and potentially topoisomerases III-DNA adducts. TDP2 is also essential for the life cycle of picornaviruses (important human and bovine pathogens) as it unlinks VPg proteins from the 5'-end of the viral RNA genome. Moreover, TDP2 has been involved in signal transduction (under the former names of TTRAP or EAPII). The DNA repair partners of TDP1 include PARP1, XRCC1, ligase III and PNKP from the base excision repair (BER) pathway. By contrast, TDP2 repair functions are coordinated with Ku and ligase IV in the non-homologous end joining pathway (NHEJ). This article summarizes and compares the biochemistry, functions, and post-translational regulation of TDP1 and TDP2, as well as the relevance of TDP1 and TDP2 as determinants of response to anticancer agents. We discuss the rationale for developing TDP inhibitors for combinations with topoisomerase inhibitors (topotecan, irinotecan, doxorubicin, etoposide, mitoxantrone) and DNA damaging agents (temozolomide, bleomycin, cytarabine, and ionizing radiation), and as novel antiviral agents.

Influence of MLH1 on colon cancer sensitivity to poly(ADP-ribose) polymerase inhibitor combined with irinotecan

Poly(ADP-ribose) polymerase inhibitors (PARPi) are currently evaluated in clinical trials in combination with topoisomerase I (Top1) inhibitors against a variety of cancers, including colon carcinoma. Since the mismatch repair component MLH1 is defective in 10-15% of colorectal cancers we have investigated whether MLH1 affects response to the Top1 inhibitor irinotecan, alone or in combination with PARPi. To this end, the colon cancer cell lines HCT116, carrying MLH1 mutations on chromosome 3 and HCT116 in which the wild-type MLH1 gene was replaced via chromosomal transfer (HCT116+3) or by transfection of the corresponding MLH1 cDNA (HCT116 1-2) were used. HCT116 cells or HCT116+3 cells stably silenced for PARP-1 expression were also analysed. The results of in vitro and in vivo experiments indicated that MLH1, together with low levels of Top1, contributed to colon cancer resistance to irinotecan. In the MLH1-proficient cells SN-38, the active metabolite of irinotecan, induced lower levels of DNA damage than in MLH1-deficient cells, as shown by the weaker induction of γ-H2AX and p53 phosphorylation. The presence of MLH1 contributed to induce of prompt Chk1 phosphorylation, restoring G2/M cell cycle checkpoint and repair of DNA damage. On the contrary, in the absence of MLH1, HCT116 cells showed minor Chk1 phosphorylation and underwent apoptosis. Remarkably, inhibition of PARP function by PARPi or by PARP-1 gene silencing always increased the antitumor activity of irinotecan, even in the presence of low PARP-1 expression.

Altered processing of amyloid precursor protein in cells undergoing apoptosis

Altered proteolysis of amyloid precursor protein is an important determinant of pathology development in Alzheimer's disease. Here, we describe the detection of two novel fragments of amyloid precursor protein in H4 neuroglioma cells undergoing apoptosis. Immunoreactivity of these 25-35 kDa fragments to two different amyloid precursor protein antibodies suggests that they contain the amyloid-β region and an epitope near the C-terminus of amyloid precursor protein. Generation of these fragments is associated with cleavage of caspase-3 and caspase-7, suggesting activation of these caspases. Studies in neurons undergoing DNA damage-induced apoptosis also showed similar results. Inclusion of caspase inhibitors prevented the generation of these novel fragments, suggesting that they are generated by a caspase-dependent mechanism. Molecular weight prediction and immunoreactivity of the fragments generated suggested that such fragments could not be generated by cleavage at any previously identified caspase, secretase, or calpain site on amyloid precursor protein. Bioinformatic analysis of the amino acid sequence of amyloid precursor protein revealed that fragments fitting the observed size and immunoreactivity could be generated by either cleavage at a novel, hitherto unidentified, caspase site or at a previously identified matrix metalloproteinase site in the extracellular domain. Proteolytic cleavage at any of these sites leads to a decrease in the generation of α-secretase cleaved secreted APP, which has both anti-apoptotic and neuroprotective properties, and thus may contribute to neurodegeneration in Alzheimer's disease.

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

Pharmacologic inhibitors of poly(ADP-ribose) polymerase (PARP) putatively enhance radiation toxicity in cancer cells. Although there is considerable information on the molecular interactions of PARP and BRCA1- and BRCA2-deficient cancers, very little is known of the PARP inhibition effect upon cancers proficient in DNA double-strand break repair after ionizing radiation or after stalled replication forks. In this work, we investigate whether PARP inhibition by ABT-888 (veliparib) augments death-provoking effects of ionizing radiation, or of the topoisomerase I poison topotecan, within uterine cervix cancers cells harboring an unfettered, overactive ribonucleotide reductase facilitating DNA double-strand break repair and contrast these findings with ovarian cancer cells whose regulation of ribonucleotide reductase is relatively intact. Cell lethality of a radiation-ABT-888 combination is radiation and drug dose dependent. Data particularly highlight an enhanced topotecan-ABT-888 cytotoxicity, and corresponds to an increased number of unrepaired DNA double-strand breaks. Overall, our findings support enhanced radiochemotherapy toxicity in cancers proficient in DNA double-strand break repair when PARP is inhibited by ABT-888.

p63 involvement in poly(ADP-ribose) polymerase 1 signaling of topoisomerase I-dependent DNA damage in carcinoma cells

Poly(ADP-ribose)polymerase 1 (PARP-1) inhibitors are thought as breakthrough for cancer treatment in solid tumors such as breast cancer through their effects on PARP's enzymatic activity. Our previous findings showed that the hydrophilic PARP inhibitor PJ34 enhances the sensitivity of p53 proficient MCF7 breast carcinoma cells to topotecan, a DNA Topoisomerase I (TOP 1) inhibitor. In the present study, we combine the classical TOP 1 poison camptothecin or its water-soluble derivative topotecan with PJ34 to investigate the potentiation of chemotherapeutic efficiency in MCF7 (p53(WT)), MDA-MB231 (p53(mut)) breast carcinoma cells and SCC022 (p53(null)) squamous carcinoma cells. We show that, following TPT-PJ34 combined treatment, MCF7 cells exhibit apoptotic death while MDA-MB231 and SCC022 cells are more resistant to these agents. Specifically, in MCF7, (i) PJ34 in combination with TPT causes a G2/M cell cycle arrest followed by massive apoptosis; (ii) PJ34 addition reverts TPT-dependent PARP-1 automodification and triggers caspase-dependent PARP-1 proteolysis; (iii) TPT, used as a single agent, stimulates p53 expression while in combination with PJ34 increases p53, TAp63α and TAp63γ protein levels with a concomitant reduction of MDM2 protein. The identification of p63 proteins as new players involved in the cancer cell response to TPT-PJ34 is relevant for a better understanding of the PARP1-dependent signaling of DNA damage. Furthermore, our data indicate that, in response to TPT-PJ34 combined chemotherapy, a functional cooperation between p53 and TAp63 proteins may occur and be essential to trigger apoptotic cell death.

Treatment with the PARP-inhibitor PJ34 causes enhanced doxorubicin-mediated cell death in HeLa cells

Adjuvant therapies can incorporate a number of different drugs to minimize the cardiotoxicity of cancer chemotherapy, decrease the development of drug resistance and increase the overall efficacy of the treatment regime. Topoisomerase IIα is a major target of many commonly used anticancer drugs, where cell death is brought about by an accumulation of double-strand DNA breaks. Poly (ADP-ribose) polymerase (PARP)-1 has been extensively studied for its role in the repair of double-strand DNA breaks, but its ability to add highly negative biopolymers (ribosylation) to target proteins provides a vast number of pathways where it can also be important in mediating cell death. In this study, we combine the classical topoisomerase IIα poison doxorubicin with the PARP inhibitor PJ34 to investigate the potentiation of chemotherapeutic efficiency in HeLa cells. We demonstrate that PJ34 treatment has the capacity to increase endogenous topoisomerase IIα protein by about 20%, and by combining doxorubicin treatment with PJ34, we observed a 50% improvement in doxorubicin-mediated cell death in HeLa cells. These results were correlated with the ribosylation of transcription factor specificity factor 1 after doxorubicin treatment, thereby altering its affinity for binding to known regulatory elements within the human topoisomerase IIα promoter. Taken together, these results highlight the synergistic potential of combining PARP inhibitors with classical topoisomerase IIα-targeting drugs.

Therapeutic intervention by the simultaneous inhibition of DNA repair and type I or type II DNA topoisomerases: one strategy, many outcomes

Many anticancer drugs reduce the integrity of DNA, forming strand breaks. This can cause mutations and cancer or cell death if the lesions are not repaired. Interestingly, DNA repair-deficient cancer cells (e.g., those with BRCA1/2 mutations) have been shown to exhibit increased sensitivity to chemotherapy. Based on this observation, a new therapeutic approach termed 'synthetic lethality' has been developed, in which radiation therapy or cytotoxic anticancer agents are employed in conjunction with selective inhibitors of poly(ADP-ribose)polymerase-1 (PARP-1). Such combinations can cause severe genomic instability in transformed cells resulting in cell death. The synergistic effects of combining PARP-1 inhibition with anticancer drugs have been demonstrated. However, the outcome of this therapeutic strategy varies significantly between cancer types, suggesting that synthetic lethality may be influenced by additional cellular factors. This review focuses on the outcomes of the combined action of PARP-1 inhibitors and agents that affect the activity of DNA topoisomerases.

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

The mu opioid receptor (MOR) is the principle molecular target of opioid analgesics. The polypyrimidine/polypurine (PPy/u) motif enhances the activity of the MOR gene promoter by adopting a non-B DNA conformation. Here, we report that the PPy/u motif regulates the processivity of torsional stress, which is important for endogenous MOR gene expression. Analysis by topoisomerase assays, S1 nuclease digests, and atomic force microscopy showed that, unlike homologous PPy/u motifs, the position- and orientation-induced structural strains to the mouse PPy/u element affect its ability to perturb the relaxation activity of topoisomerase, resulting in polypurine strand-nicked and catenated DNA conformations. Raman spectrum microscopy confirmed that mouse PPy/u containing-plasmid DNA molecules under the different structural strains have a different configuration of ring bases as well as altered Hoogsteen hydrogen bonds. The mouse MOR PPy/u motif drives reporter gene expression fortyfold more effectively in the sense orientation than in the antisense orientation. Furthermore, mouse neuronal cells activate MOR gene expression in response to the perturbations of topology by topoisomerase inhibitors, whereas human cells do not. These results suggest that, interestingly among homologous PPy/u motifs, the mouse MOR PPy/u motif dynamically responds to torsional stress and consequently regulates MOR gene expression in vivo.