Natural and glucosyl flavonoids inhibit poly(ADP-ribose) polymerase activity and induce synthetic lethality in BRCA mutant cells

ATM dysfunction in Chinese hamster XRCC8 mutants

XRCC8 is a member of the X-ray cross-complementing (XRCC) family, whose responsible gene has not been identified. Previous studies suggested ATM and other genes were potential candidates for XRCC8, but this was not confirmed. In this study, we characterized three V79-derived XRCC8 mutant cells: V-C4, V-E5, and V-G8. Western blot analysis showed reduced expression of the ATM protein in three XRCC8 mutants, and radiation-induced phosphorylated ATM foci were not detected by fluorescence immunocytochemistry. Both ATM knockout cells and XRCC8 mutants exhibited hypersensitivity to camptothecin. Through a cell fusion-based complementation test, we found that XRCC8 mutants were complemented by ATM-proficient cells, but not by ATM knockout cells, in terms of camptothecin sensitivity. Comprehensive sequencing of the ATM genome in XRCC8 mutants revealed unique mutations in each mutant. These results suggest that XRCC8 mutants carry ATM mutations, and their ATM is not properly functional, despite protein expression being detected. This is similar to missense mutations in some Ataxia Telangiectasia patients.

ATM and ATR gene editing mediated by CRISPR/Cas9 in Chinese Hamster cells

Chinese hamster-derived cell lines including Chinese hamster lung fibroblasts (V79) have been used as model somatic cell lines in radiation biology and toxicology research for decades and have been instrumental in advancing our understanding of DNA damage response (DDR) mechanisms. Whereas many mutant lines deficient in DDR genes have been generated more than over decades, several key DDR genes such as ATM and ATR have not been established in the Chinese hamster system. Here, we transfected CRISPR/Cas9 vectors targeting Chinese hamster ATM or ATR into V79 cells and investigated whether the isolated clones had the characteristics reported in human and mouse studies. We obtained two clones of ATM knockout cells containing an insertion or deletions in the targeted locus. The ATM knockouts with no detectable ATM protein expression exhibited increased sensitivity to radiation and DNA double strand break inducing agents, cell cycle checkpoint defects and defective chromatid break repair. These are all characteristics of defective ATM function. Among the obtained ATR cells, which contained mutations in both ATR alleles while maintaining normal levels of ATR protein expression, one clone exhibited hypersensitivity to UV and replication stress agents. In the present study, we successfully established CRISPR-Cas9 derived ATM knockout cells. We couldn't knock out the ATR gene but obtained ATR mutant cells. Our results showed that Chinese hamster origin ATM knockout cells and ATR mutant cells could be useful tools for further research to reveal oncogenic functions and effects of developing anti-cancer therapeutics.

Astaxanthin targets IL-6 and alleviates the LPS-induced adverse inflammatory response of macrophages

Numerous natural compounds are recognized for their anti-inflammatory properties attributed to antioxidant effects and the modulation of key inflammatory factors. Among them, astaxanthin (AST), a potent carotenoid antioxidant, remains relatively underexplored regarding its anti-inflammatory mechanisms and specific molecular targets. In this study, human monocytic leukemia cell-derived macrophages (THP-1) were selected as experimental cells, and lipopolysaccharides (LPS) served as inflammatory stimuli. Upon LPS treatment, the oxidative stress was significantly increased, accompanied by remarkable cellular damage. Moreover, LPSs escalated the expression of inflammation-related molecules. Our results demonstrate that AST intervention could effectively alleviate LPS-induced oxidative stress, facilitate cellular repair, and significantly attenuate inflammation. Further exploration of the anti-inflammatory mechanism revealed AST could substantially inhibit NF-κB translocation and activation, and mitigate inflammatory factor production by hindering NF-κB through the antioxidant mechanism. We further confirmed that AST exhibited protective effects against cell damage and reduced the injury from inflammatory cytokines by activating p53 and inhibiting STAT3. In addition, utilizing network pharmacology and in silico calculations based on molecular docking, molecular dynamics simulation, we identified interleukin-6 (IL-6) as a prominent core target of AST anti-inflammation, which was further validated by the RNA interference experiment. This IL-6 binding capacity actually enabled AST to curb the positive feedback loop of inflammatory factors, averting the onset of possible inflammatory storms. Therefore, this study offers a new possibility for the application and development of astaxanthin as a popular dietary supplement of anti-inflammatory or immunomodulatory function.

Green Cancer Prevention and Beyond

The concept of green chemoprevention was introduced in 2012 by Drs. Jed Fahey and Thomas Kensler as whole-plant foods and/or extract-based interventions demonstrating cancer prevention activity. Refining concepts and research demonstrating proof-of-principle approaches are highlighted within this review. Early approaches included extensively investigated whole foods, including broccoli sprouts and black raspberries showing dose-responsive effects across a range of activities in both animals and humans with minimal or no apparent toxicity. A recent randomized crossover trial evaluating the detoxification of tobacco carcinogens by a broccoli seed and sprout extract in the high-risk cohort of current smokers highlights the use of a dietary supplement as a potential next-generation green chemoprevention or green cancer prevention approach. Challenges are addressed, including the selection of dose, duration and mode of delivery, choice of control group, and standardization of the plant food or extract. Identification and characterization of molecular targets and careful selection of high-risk cohorts for study are additional important considerations when designing studies. Goals for precision green cancer prevention include acquiring robust evidence from carefully controlled human studies linking plant foods, extracts, and compounds to modulation of targets for cancer risk reduction in individual cancer types.

Artemisia vulgaris L., Artemisia alba Turra and their constituents reduce mitomycin C-induced genomic instability in human peripheral blood lymphocytes in vitro

This study aimed to evaluate the effect of aqueous and acetone extracts from Artemisia vulgaris L. (AV) and Artemisia alba Turra (AA), and two major polyphenols compounds (3,5-dihydroxybenzoic acid and quercetin-3-O-glucopyranoside) presented in both extracts of the plants against mitomycin C (MMC)-induced genomic instability. Genomic instability was measured using cytokinesis block micronucleus (MN) assay in human peripheral blood lymphocytes (PBLs) in vitro by analyzing two biomarkers - MN and nuclear division index (NDI). Extracts were tested in a concentration-dependent manner (10-250 µg/mL), while 3,5-dihydroxybenzoic acid and quercetin-3-O-glucopyranoside were tested in three different concentrations, in combination with 0.5 µg/mL of MMC. Aqueous and acetone extracts obtained from both plants significantly reduced MMC-induced MN frequency in PBLs, compared to positive control cells (p < 0.05). Extracts from AV did not affect NDI, whereas the concentrations of 10-100 μg/mL of aqueous and acetone AA extracts significantly elevated MMC-decreased NDI values in comparison to positive control cells (p < 0.05). Combined treatment of 3,5-dihydroxybenzoic acid and MMC showed a significant reduction of MMC-induced MN frequency, while quercetin-3-O-glucopyranoside increased MN frequency compared to positive control cells (p < 0.05). Both compounds decreased NDI values but only at the highest tested concentration of quercetin-3-O-glucopyranoside it was of greater significance. In conclusion, all extracts from AV and AA and 3,5-dihydroxybenzoic acid showed protective effect, whereby aqueous AA demonstrated the highest protective effect on MMC- induced genomic instability, while quercetin-3-O-glucopyranoside showed co-mutagen effect.

The contribution of high-LET track to DNA damage formation and cell death for Monoenergy and SOBP carbon ion irradiation

Carbon ion radiotherapy (CIRT) is a heavy ion charge particle therapy with 29 years of prominent use. Despite advantages like high relative biological effectiveness (RBE), improved quality of life, and reduced treatment time, challenges persist, especially regarding heavy nuclear fragments. Our research addresses these challenges in horizontal irradiation, aiming to comprehend Monoenergetic and Spread-Out Bragg peak (SOBP) carbon ion beam trajectories using cell survival analysis and visualizing biological effects through DNA damage (γ-H2AX). This reveals repair-related protein foci near the Bragg peak. CR-39, a plastic nuclear track detector, was explored to understand high-linear energy transfer (LET) tracks and radiation quality near the Bragg peak. Findings unveil high-LET DNA damage signatures through aligned γ-H2AX foci, correlating with LET values in SOBP. CR-39 visualized high-LET particle exposure, indicating comet-type etch-pits at the Bragg peak and suggesting carbon ion fragmentation. Unexpectedly, dot-type etch-pits in irradiated and post-Bragg peak regions indicated high-LET neutron production. This investigation highlights the intricate interplay of carbon ion beams, stressing the importance of understanding LET variations, DNA damage patterns, and undesired secondary exposure.

Palmitoyl ascorbic acid glucoside enhanced cell survival with post irradiation treatment

Radiation exposure poses a significant threat to cellular integrity by inducing DNA damage through the generation of free radicals and reactive oxygen species. Ascorbic acid, particularly its derivative Palmitoyl Ascorbic Acid 2-Glucoside (PA2G), has demonstrated remarkable radioprotective properties. While previous research focused on its pre-irradiation application, this study explores the post-irradiation radiomitigation potential of PA2G. Our findings reveal that post-irradiation treatment with PA2G enhances cell survival and accelerates DNA repair processes, particularly the non-homologous end-joining (NHEJ) repair pathway. Notably, PA2G treatment reduces the frequency of lethal chromosomal aberrations and micronuclei formation, indicating its ability to enhance the repair of complex DNA lesions. Furthermore, PA2G is shown to play a role in potentially lethal damage repair (PLDR). These radioprotective effects are specific to NHEJ and ATM pathways, as cells deficient in these mechanisms do not benefit from PA2G treatment. This study highlights PA2G as a versatile radioprotector, both pre- and post-irradiation, with significant potential for applications in radiation therapy and protection, offering new insights into its mechanism of action. Further research is required to elucidate the precise molecular mechanisms underlying PA2G's radiomitigation effects and its potential clinical applications.

Flavone-based dual PARP-Tubulin inhibitor manifesting efficacy against endometrial cancer

Structural tailoring of the flavone framework (position 7) via organopalladium-catalyzed C-C bond formation was attempted in this study. The impact of substituents with varied electronic effects (phenyl ring, position 2 of the benzopyran scaffold) on the antitumor properties was also assessed. Resultantly, the efforts yielded a furyl arm bearing benzopyran possessing a 4-fluoro phenyl ring (position 2) (14) that manifested a magnificent antitumor profile against the Ishikawa cell lines mediated through dual inhibition of PARP and tubulin [(IC50 (PARP1) = 74 nM, IC50 (PARP2) = 109 nM) and tubulin (IC50 = 1.4 µM)]. Further investigations confirmed the ability of 14 to induce apoptosis as well as autophagy and cause cell cycle arrest at the G2/M phase. Overall, the outcome of the study culminated in a tractable dual PARP-tubulin inhibitor endowed with an impressive activity profile against endometrial cancer.

Sulfoquinovosyl acylpropanediol (SQAP): Inhibition of poly(ADP-ribose) metabolism and enhanced cytotoxicity in homologous recombination repair-deficient Chinese hamster-derived cells

Sulfoquinovosyl acylpropanediol (SQAP; a synthetic derivative of the sulfoglycolipid natural product sulfoquinovosyl acylglycerol, SQAG), has anti-tumor and radiosensitizing activities in tumor xenograft mouse models. Here, we have studied the PARP inhibitory activity of SQAP and synthetic lethality in BRCA2-deficient cells. In initial screening studies with DNA repair-deficient Chinese hamster ovary cells, homologous recombination repair-deficient cell lines showed increased sensitivity to SQAP, compared to wild-type cells or other DNA repair-deficient mutants. Chinese hamster lung V79 cells and the derivative cell lines V-C8 (BRCA2-deficient) and V-C8 + BRCA2 gene corrections were used to test the role of BRCA2 in SQAP cytotoxicity. The findings were confirmed in studies of the human colon cancer cell lines DLD-1 and its BRCA2-knockout derivative. SQAP inhibited the enzymes poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG). SQAP pretreatment decreased H2O2induced poly(ADP-ribose) formation in V79 cells. SQAP caused DNA double-strand breaks and chromosome aberrations in V79 BRCA2-mutated cells but did not affect cells in the G2 phase. We have demonstrated that SQAP induces synthetic lethality in BRCA2-deficient Chinese hamster-derived cells via its effects on poly(ADP-ribose) metabolism, motivating further examination of its therapeutic potential, especially against tumors that are deficient in homologous recombination repair due to mutations in BRCA2 or other genes.

Artificial induction of chromosome aneuploidy in CHO cells alters their function as host cells

Chinese hamster ovary (CHO) cells are major host cells for biopharmaceuticals. During culture, the chromosome number of CHO cells alters spontaneously. Here, we investigated the effects of artificial changes in the chromosome number on productivity. When cell fusion between antibody-producing CHO-K1-derived cells was induced, we observed a wide range of aneuploidy that was not detected in controls. In particular, antibody productivities were high in clone-derived cell populations that retained a diverse chromosome number distribution. We also induced aneuploid cells using 3-aminobenzamide that causes chromosome non-disjunction. After induction of aneuploidy by 3-aminobenzamide, cells with an increased chromosome number were isolated, but cells with a decreased chromosome number could not be isolated. When antibody expression vectors were introduced into these isolated clones, productivity tended to increase in cells with an increased chromosome number. Further analysis was carried out by focusing on clone 5E8 with an average chromosome number of 37. When 5E8 cells were used as host, the productivity of multiple antibodies, including difficult-to-express antibodies, was improved compared with CHO-K1 cells. The copies of exogenous genes integrated into the genome were significantly increased in 5E8 cells. These findings expand the possibilities for host cell selection and contribute to the efficient construction of cell lines for recombinant protein production.

XRCC8 mutation causes hypersensitivity to PARP inhibition without Homologous recombination repair deficiency

PARP inhibitors inflict severe toxicity to homologous recombination (HR) repair deficient cells because DNA damages induced by PARP inhibition result in lethal DNA double strand breaks in the absence of HR repair during DNA replication. PARP inhibitors are the first clinically approved drugs designed for synthetic lethality. The synthetic lethal interaction of PARP inhibitors is not limited to HR repair deficient cells. We investigated radiosensitive mutants isolated from Chinese hamster lung origin V79 cells to identify novel synthetic lethal targets in the context of PARP inhibition. HR repair deficient BRCA2 mutant cells were used for positive control. Among tested cells, XRCC8 mutants presented hypersensitivity to PARP inhibitor, Olaparib. XRCC8 mutants showed elevated sensitivity to bleomycin and camptothecin similar to BRCA2 mutants. XRCC8 mutants presented an elevation of γ-H2AX foci formation frequency and S-phase dependent chromosome aberrations with Olaparib treatment. Enumerated damage foci following Olaparib treatment were observed to be elevated in XRCC8 as in BRCA2 mutants. Although this may suggest that XRCC8 plays a role in a similar DNA repair pathway as BRCA2 in HR repair, XRCC8 mutants presented functional HR repair including proper Rad51 foci formation and even elevated sister chromatid exchange frequencies with PARP inhibitor treatment. For comparison, RAD51 foci formation was suppressed in HR repair deficient BRCA2 mutants. Additionally, XRCC8 mutants did not display delayed mitotic entry with PARP inhibitors whereas BRCA2 mutants did. XRCC8 mutant cell line has previously been reported as possessing a mutation in the ATM gene. XRCC8 mutants displayed maximum cytotoxicity to ATM inhibitor among tested mutants and wild type cells. Furthermore, the ATM inhibitor sensitized XRCC8 mutant to ionzing radiation, however, XRCC8 mutant V-G8 expressed reduced levels of ATM protein. The gene responsible for XRCC8 phenotype may not be ATM but highly associated with ATM functions. These results suggest that XRCC8 mutation is a target for PARP inhibitor-induced synthetic lethality in HR repair independent manner via the disruption of cell cycle regulation. Our findings expand the potential application of PARP inhibitors in tumors lacking DNA damage responding genes other than HR repair, and further investigation of XRCC8 may contribute to this research.

Immunomodulatory, Anticancer, and Antimicrobial Effects of Rice Bran Grown in Iraq: An In Vitro and In Vivo Study

Emerging evidence supports the role of rice bran in cancer prevention. Studies were conducted on multiple rice cultivars. However, limited studies were conducted on rice cultivars in the Middle East. In this study, rice bran growing in Iraq (O. sativa ssp. Japonica, cultivars: Amber Barka) was evaluated for its effect on preventing cancer and stimulating the immune system. Rice bran was collected from local mills in Al-Najaf (south of Iraq). Several solvent extracts (ethanol, methanol, n-hexane, and water) were prepared by maceration. MTT assay was used to measure the antiproliferative effects of extracts against a panel of cancer cell lines. The ability of each extract to induce apoptosis and inhibit angiogenesis was measured using standard ELISA kits. The effect of extracts on the immune system was evaluated using a lymphocyte proliferation assay, a pinocytic activity assay, a phagocytic activity assay, and a Th1/Th2 cytokine detection kit. A microbroth dilution method was used to detect the antimicrobial activity of each extract against different microbial strains. LC-MS analysis was used to detect the phytochemical composition of extracts, while DPPH assay was used to determine the antioxidant activity. For the in vivo study, rice bran was added to mouse fodder at 10% and 20%. Mice were treated for two weeks using mouse fodder supplemented with rice bran. In the third week of the experiment, EMT6/P breast cancer cells (1 × 10⁶ cells/mL) were injected subcutaneously into the abdominal area of each mouse. The dimensions of the grown tumors were measured after 14 days of tumor inoculation. A microbroth dilution method was used to evaluate the antimicrobial activity of rice bran extracts against three bacterial strains. The highest antiproliferative activity was observed in ethanol and n-hexane extracts. Ethanol and methanol extract showed the highest activity to induce apoptosis and inhibit angiogenesis. Both extracts were also effective to enhance immunity by activating lymphocytes and phagocytes proliferation with modulations of cytokine levels. The incorporation of rice bran in mice food caused a 20% regression in tumor development and growth compared with the negative control. All extracts exhibited limited antimicrobial activity against tested microorganisms. Methanol extract showed antioxidant activity with an IC₅₀ value of 114 µg/mL. LC-MS analysis revealed the presence of multiple phytochemicals in rice bran including apiin, ferulic acid, and succinic acid. Rice bran is a rich source of active phytochemicals that may inhibit cancer and stimulate the immune system. Rice bran's biological activities could be due to the presence of multiple synergistically active phytochemicals. Further studies are needed to understand the exact mechanisms of action of rice bran.

Comparative Metabolomics Analysis of Stigmas and Petals in Chinese Saffron (Crocus sativus) by Widely Targeted Metabolomics

The dried stigmas of Crocus sativus, commonly known as saffron, are consumed largely worldwide because it is highly valuable in foods and has biological activities beneficial for health. Saffron has important economic and medicinal value, and thus, its planting area and global production are increasing. Petals, which are a by-product of the stigmas, have not been fully utilized at present. We compared the metabolites between the stigmas and petals of C. sativus using a non-targeted metabolomics method. In total, over 800 metabolites were detected and categorized into 35 classes, including alkaloids, flavonoids, amino acids and derivatives, phenols and phenol esters, phenylpropanoids, fatty acyls, steroids and steroid derivatives, vitamins, and other metabolites. The metabolite composition in the petals and stigmas was basically similar. The results of the study showed that the petals contained flavonoids, alkaloids, coumarins, and other medicinal components, as well as amino acids, carbohydrates, vitamins, and other nutritional components. A principal components analysis (PCA) and an orthogonal partial least-squares discriminant analysis (OPLS-DA) were performed to screen the different metabolic components. A total of 339 differential metabolites were identified, with 55 metabolites up-regulated and 284 down-regulated. The up-regulated metabolites, including rutin, delphinidin-3-O-glucoside, isoquercitrin, syringaresinol-di-O-glucoside, dihydrorobinetin, quercetin, and gallocatechin, were detected in the petals. The down-regulated metabolites were mainly glucofrangulin B, acetovanillone, daidzein, guaiazulene, hypaphorine, indolin-2-one, and pseudouridine. KEGG annotation and enrichment analyses of the differential metabolites revealed that flavonoid biosynthesis, amino acids biosynthesis, and arginine and proline metabolism were the main differentially regulated pathways. In conclusion, the petals of C. sativus are valuable for medicine and foods and have potential utility in multiple areas such as the natural spice, cosmetic, health drink, and natural health product industries.

Comparative study of the genotoxic activity of Artemisia vulgaris L. and Artemisia alba Turra extracts in vitro

In this study, the genotoxic activity of acetone and aqueous extracts of two species of genus Artemisia (Artemisia vulgaris L. and Artemisia alba Turra), and possible role of their polyphenolic composition in the observed activities were investigated. Polyphenolic contents were evaluated by high-performance liquid chromatography (HPLC-PDA), while the genotoxic activity was tested using cytokinesis block micronucleus (CBMN) assay on human peripheral blood lymphocytes (PBLs) in vitro. HPLC-PDA showed that both A. alba extracts were richer in polyphenolic contents than A. vulgaris extracts. The acetone A. alba extract was the richest of polyphenolic content where we detected six phenolic acids and two flavonoids. CBMN assay showed that aqueous extract of A. vulgaris significantly increased micronucleus (MN) frequency in the PBLs treated with all tested concentrations (10, 50, 100, and 250 µg/mL), while A. alba did not significantly affect the mean MN frequency. Further, both acetone extracts were genotoxic in all tested concentrations, except the lowest tested (10 µg/mL) of A. alba. All tested extracts affected the nuclear division index (NDI) except the aqueous A. alba extract (p < 0.05). Based on our results, we can conclude that both acetone and aqueous A. vulgaris extracts and A. alba acetone extract were genotoxic in PBLs in vitro. A. alba aqueous extract was not genotoxic and cytotoxic in tested concentrations. We suggest that the aqueous extract of A. alba can be used in treatment, which has been confirmed by traditional medicine, but with a high dose of caution and not in high concentrations.

A Comparative Study of Rutin and Rutin Glycoside: Antioxidant Activity, Anti-Inflammatory Effect, Effect on Platelet Aggregation and Blood Coagulation

The effects of rutin and rutin glycoside with different solubility were compared on antioxidant activity and anti-inflammatory effects in vitro and the effects on platelet aggregation and blood coagulation in vitro and in vivo. Rutin glycoside (consisting of rutin mono-glucoside and rutin di-glucoside) was prepared via enzymatic transglycosylation from rutin. Rutin glycoside showed a higher effect than rutin on radical scavenging activity in antioxidant assays. Rutin showed a higher toxicity than rutin glycoside in murine macrophage RAW264.7 cells. They had similar effects on the levels of nitric oxide (NO), prostaglandin E (PGE) 2 and pro-inflammatory cytokines (such as tumor necrosis factor (TNF)-α, and interleukin (IL)-6) in the cells. Both rutin and rutin glycosides similarly reduced the rate of platelet aggregation compared to controls in vitro. They also similarly delayed prothrombin time (PT) and activated partial thromboplastin time (APTT) in an in vitro blood coagulation test. The effect of repeated administration of rutin and rutin glycoside was evaluated in vivo using SD rats. The platelet aggregation rate of rutin and the rutin glycoside administered group was significantly decreased compared to that of the control group. On the other hand, PT and APTT of rutin and rutin glycoside group were not significantly delayed in vivo blood coagulation test. In conclusion, rutin and rutin glycoside showed differences in antioxidant activities in vitro, while they were similar in the reduction of NO, PGE2, TNF-α and IL-6 in vitro. Rutin and rutin glycoside also showed similar platelet aggregation rates, and blood coagulation both in vitro and in vivo condition. Comparing in vitro and in vivo, rutin and rutin glycoside were effective on platelet aggregation both in vitro and in vivo, but only in vitro on blood coagulation.

PARP-1-Associated Pathological Processes: Inhibition by Natural Polyphenols

Poly (ADP-ribose) polymerase-1 (PARP-1) is a nuclear enzyme involved in processes of cell cycle regulation, DNA repair, transcription, and replication. Hyperactivity of PARP-1 induced by changes in cell homeostasis promotes development of chronic pathological processes leading to cell death during various metabolic disorders, cardiovascular and neurodegenerative diseases. In contrast, tumor growth is accompanied by a moderate activation of PARP-1 that supports survival of tumor cells due to enhancement of DNA lesion repair and resistance to therapy by DNA damaging agents. That is why PARP inhibitors (PARPi) are promising agents for the therapy of tumor and metabolic diseases. A PARPi family is rapidly growing partly due to natural polyphenols discovered among plant secondary metabolites. This review describes mechanisms of PARP-1 participation in the development of various pathologies, analyzes multiple PARP-dependent pathways of cell degeneration and death, and discusses representative plant polyphenols, which can inhibit PARP-1 directly or suppress unwanted PARP-dependent cellular processes.

High LET-Like Radiation Tracks at the Distal Side of Accelerated Proton Bragg Peak

Proton therapy is a type of hadron radiotherapy used for treating solid tumors. Unlike heavy charged elements, proton radiation is considered to be low LET (Linear Energy Transfer) radiation, like X-rays. However, the clinical SOBP (Spread Out Bragg Peak) proton radiation is considered to be higher in relative biological effectiveness (RBE) than both X-ray and their own entrance region. The RBE is estimated to be 1.1–1.2, which can be attributed to the higher LET at the SOBP region than at the entrance region. In order to clarify the nature of higher LET near the Bragg peak of proton radiation and its potential cytotoxic effects, we utilized a horizontal irradiation system with CHO cells. Additionally, we examined DNA repair mutants, analyzed cytotoxicity with colony formation, and assessed DNA damage and its repair with γ-H2AX foci assay in a high-resolution microscopic scale analysis along with the Bragg peak. Besides confirming that the most cytotoxic effects occurred at the Bragg peak, extended cytotoxicity was observed a few millimeters after the Bragg peak. γ-H2AX foci numbers reached a maximum at the Bragg peak and reduced dramatically after the Bragg peak. However, in the post-Bragg peak region, particle track-like structures were sporadically observed. This region contains foci that are more difficult to repair. The peak and post-Bragg peak regions contain rare high LET-like radiation tracks and can cause cellular lethality. This may have caused unwanted side effects and complexities of outputs for the proton therapy treatment.

Molecular mechanisms of anticancer effect of rutin

Because of the extensive biological functions of natural substances such as bioflavonoids, and their high safety and low costs, they could have high priority application in the health care system. The antioxidant properties of rutin, a polyphenolic bioflavonoid, have been well documented and demonstrated a wide range of pharmacological applications in cancer research. Since chemotherapeutic drugs have a wide range of side effects and rutin is a safe anticancer agent with minor side effects so recent investigations are performed for study of mechanisms of its anticancer effect. Both in-vivo and in-vitro examinations on anticancer mechanisms of this natural agent have been widely carried out. Regulation of different cellular signaling pathways such as Wnt/β-catenin, p53-independent pathway, PI3K/Akt, JAK/STAT, MAPK, p53, apoptosis as well as NF-ĸB signaling pathways helps to mediate the anticancer impacts of this agent. This study tried to review the molecular mechanisms of rutin anticancer effect on various types of cancer. Deep exploration of these anticancer mechanisms can facilitate the development of this beneficial compound for its application in the treatment of different cancers.

Development and evaluation of poly adenosine 5'-diphosphate-ribose polymerase 1 immobilization-based receptor chromatography

Yanghe decoction is a traditional Chinese medicine prescription and has been used for breast cancer treatment for many years. However, the effective ingredients in the decoction have not been identified. The expression of poly(ADP-ribose) polymerase-1 is highly related to breast cancer. Using poly(ADP-ribose) polymerase-1 as a probe, we expressed the haloalkane dehalogenase-tagged protein in BL21(DE3) E. coli, immobilized it on hexachlorocaproic acid-modified macroporous silica gel, and established a poly(ADP-ribose) polymerase-1 chromatographic model. The feasibility of the model was verified by testing the retention behaviors of five drugs on the protein column. We applied the model in screening the bioactive components in yanghe decoction. Rutin, liquiritin, and a compound ([M-H]^- 681.7) were identified to be the potential bioactive ingredients. We studied the binding property between rutin and poly(ADP-ribose) polymerase-1 by injection amount dependent method, competitive studies, and molecular docking. We found that rutin can bind to the protein through the typical inhibitor binding site of the protein. Therefore, the chromatographic model is a useful tool to screen bioactive compounds from traditional Chinese medicine. The method is fast, reliable, and applicable to other functional proteins that can screen the potential lead compounds for the treatment of the related diseases.

Natural Compounds That Target DNA Repair Pathways and Their Therapeutic Potential to Counteract Cancer Cells

Resistance to current cancer treatments is an important problem that arises through various mechanisms, but one that stands out involves an overexpression of several factors associated with DNA repair. To counteract this type of resistance, different drugs have been developed to affect one or more DNA repair pathways, therefore, to test different compounds of natural origin that have been shown to induce cell death in cancer cells is paramount. Since natural compounds target components of the DNA repair pathways, they have been shown to promote cancer cells to be resensitized to current treatments. For this and other reasons, natural compounds have aroused great curiosity and several research projects are being developed around the world to establish combined treatments between them and radio or chemotherapy. In this work, we summarize the effects of different natural compounds on the DNA repair mechanisms of cancer cells and emphasize their possible application to re-sensitize these cells.

The Effects of Doxorubicin, Ethanol Extract and Flavonoid-rich Fraction of Euphorbia Splendida Mobayen on the PARP Level, and APC Gene Expression in HT-29 Human Colon Cancer Cell Line

Background: Natural products derived from various sources are being used to develop chemotherapeutic drugs. Euphorbiaceae is widely used to treat different types of cancers. Colorectal cancer (CRC) is the second and third cause of cancer in women and men, respectively. CRC is strongly associated with the deregulation of the Adenomatous polyposis coli (APC) gene and Poly [ADP-ribose] polymerase (PPAR) protein. Objectives: The current study aimed to examine the effect of doxorubicin, ethanol extract, and the flavonoid-rich fraction of Euphorbia Splendida Mobayen on colon cancer HT-29 cell line death, APC gene expression, and PPAR concentration. Methods: Following treatment of cells by Euphorbia ethanol extract, Euphorbia flavonoid-rich fraction, and doxorubicin, cell viability assay was used to investigate the viability status of the HT-29 cell line. Total RNA was isolated from the cell line and converted into cDNA. The expression level of the APC gene was determined by quantitative real-time PCR. Poly (ADP-ribose) polymerase (PPAR) protein was detected by the ELIZA method. Results: We found that Euphorbia ethanol extract, Euphorbia flavonoid-rich fraction, and doxorubicin can stimulate dose-dependent cell death in the HT-29 cell line, increase ACP gene expression (P = 0.001, P = 0.041, P = 0.019), and decrease PARP level (P = 0.001, P = 0.001, P = 0.001, respectively). Conclusions: The findings indicated that doxorubicin, ethanol extract, and the flavonoid-rich fraction of Euphorbia Splendida Mobayen had cytotoxic effects on human colon cancer HT-29 cell line by possibly stimulating apoptosis.

The Role of Poly(ADP-Ribose) Polymerase-1 in Cutaneous Wound Healing

Critical Issue: Chronic nonhealing wounds of the lower extremities resulting in major amputations are a major health problem worldwide. Significance: Diabetes and ischemia are two major etiologies of nonhealing wounds of the lower extremities. Hyperglycemia from diabetes and oxidative stress from ischemia activate polyadenosine diphosphate (ADP)-ribose polymerase-1 (PARP-1), which is a nuclear enzyme that is best known for its role in DNA repair. However, the exact function of PARP-1 in ischemic/diabetic wound healing has not been well studied. Recent Advances: Poly-ADP-ribose (PAR) polymer has been detected in the wound bed and many of the PARylation-related reactions (oxidative stress response, expression of inflammatory cytokines and chemokines, cell proliferation, and migration) are important in the wound healing process. However, the role of PARP-1 in wound healing and the potential of targeting PARP-1 therapeutically in wounds are only recently being elucidated, with much still unknown. This review summarizes the recent advances in this field, highlighting some of the mechanisms through which PARP-1 may affect normal wound closure. Future Directions: The review also presents a perspective on some of the downstream targets of PARP-1 that may be explored for their role in wound healing and discusses about the therapeutic potential of PARP inhibitors for wound healing.

Puerarin protects against high-fat high-sucrose diet-induced non-alcoholic fatty liver disease by modulating PARP-1/PI3K/AKT signaling pathway and facilitating mitochondrial homeostasis

As yet, there was no effective pharmacological therapy approved for non-alcoholic fatty liver disease (NAFLD). Here, we aimed to evaluate the therapeutic potential of puerarin against NAFLD and explored the underlying mechanisms. C57BL/6J mice were fed with a high-fat high-sucrose (HFHS) diet with or without puerarin coadministration intragastrically. The levels of hepatocellular injury, steatosis, fibrosis, and mitochondrial and metabolism alteration were detected. First, puerarin ameliorated histopathologic abnormalities due to HFHS. We observed a marked increase in hepatic lipid content, inflammation, and fibrosis level, which were attenuated by puerarin. Possible mechanisms were related to puerarin-mediated activation of PI3K/AKT pathway and further improvement in fatty acid metabolism. Puerarin restored the NAD+ content and beneficially affected the hepatic mitochondrial function, which attenuated HFHS-induced steatosis and metabolic disturbances. Finally, hepatic PARP-1 was activated due to excessive fat intake. Puerarin attenuated the PARP-1 expression in HFHS-fed mice, and PJ34, the PARP inhibitor, could mimic these protections of puerarin. However, pharmacological inhibition of PI3K disabled the protection of puerarin or PJ34 toward NAD+ refilling and mitochondrial homeostasis. In conclusion, our findings indicated that puerarin could be a promising and practical therapeutic strategy in NAFLD through modulating PARP-1/PI3K/AKT signaling pathway and further facilitating mitochondrial function.

The Effect of Green and Black Tea Polyphenols on BRCA2 Deficient Chinese Hamster Cells by Synthetic Lethality through PARP Inhibition

Tea polyphenols are known antioxidants presenting health benefits due to their observed cellular activities. In this study, two tea polyphenols, epigallocatechin gallate, which is common in green tea, and theaflavin, which is common in black tea, were investigated for their PARP inhibitory activity and selective cytotoxicity to BRCA2 mutated cells. The observed cytotoxicity of these polyphenols to BRCA2 deficient cells is believed to be a result of PARP inhibition induced synthetic lethality. Chinese hamster V79 cells and their BRCA2 deficient mutant V-C8, and V-C8 with gene complemented cells were tested against epigallocatechin gallate and theaflavin. In addition, Chinese hamster ovary (CHO) wild-type cells and rad51D mutant 51D1 cells were used to further investigate the synthetic lethality of these molecules. The suspected PARP inhibitory activity of epigallocatechin and theaflavin was confirmed through in vitro and in vivo experiments. Epigallocatechin gallate showed a two-fold increase of cytotoxicity to V-C8 cells compared to V79 and gene complimented cells. Compared to CHO wild type cells, 51D1 cells also showed elevated cytotoxicity following treatment with epigallocatechin gallate. Theaflavin, however, showed a similar increase of cytotoxicity to VC8 compared to V79 and gene corrected cells, but did not show elevation of cytotoxicity towards rad51D mutant cells compared to CHO cells. Elevation of sister chromatid exchange formation was observed in both tea polyphenol treatments. Polyphenol treatment induced more micronuclei formation in BRCA2 deficient cells and rad51D deficient cells when compared against the respective wild type cells. In conclusion, tea polyphenols, epigallocatechin gallate, and theaflavin may present selective cytotoxicity to BRCA2 deficient cells through synthetic lethality induced by PARP inhibition.

DNA Repair Deficient Chinese Hamster Ovary Cells Exhibiting Differential Sensitivity to Charged Particle Radiation under Aerobic and Hypoxic Conditions

It has been well established that hypoxia significantly increases both cellular and tumor resistance to ionizing radiation. Hypoxia associated radiation resistance has been known for some time but there has been limited success in sensitizing cells to radiation under hypoxic conditions. These studies show that, when irradiated with low linear energy transfer (LET) gamma-rays, poly (ADP-ribose), polymerase (PARP), Fanconi Anemia (FANC), and mutant Chinese Hamster Ovary (CHO) cells respond similarly to the non-homologous end joining (NHEJ) and the homologous recombination (HR) repair mutant CHO cells. Comparable results were observed in cells exposed to 13 keV/μm carbon ions. However, when irradiated with higher LET spread out Bragg peak (SOBP) carbon ions, we observed a decrease in the oxygen enhancement ratio (OER) in all the DNA of repair mutant cell lines. Interestingly, PARP mutant cells were observed as having the largest decrease in OER. Finally, these studies show a significant increase in the relative biological effectiveness (RBE) of high LET SOBP carbon and iron ions in HR and PARP mutants. There was also an increase in the RBE of NHEJ mutants when irradiated to SOBP carbon and iron ions. However, this increase was lower than in other mutant cell lines. These findings indicate that high LET radiation produces unique types of DNA damage under hypoxic conditions and PARP and HR repair pathways play a role in repairing this damage.

Targeting ubiquitin-proteasome pathway by natural, in particular polyphenols, anticancer agents: Lessons learned from clinical trials

The ubiquitin-proteasome pathway (UPP) is the main non-lysosomal proteolytic system responsible for degradation of most intracellular proteins, specifically damaged and regulatory proteins. The UPP is implicated in all aspects of the cellular metabolic networks including physiological or pathological conditions. Alterations in the components of the UPP can lead to stabilization of oncoproteins or augmented degradation of tumour suppressor favouring cancer appearance and progression. Polyphenols are natural compounds that can modulate proteasome activity or the expression of proteasome subunits. All together and due to the pleiotropic functions of UPP, there is a great interest in this proteasome system as a promising therapeutic target for the development of novel anti-cancer drugs. In the present review, the main features of the UPP and its implication in cancer development and progression are described, highlighting the importance of bioactive polyphenols that target the UPP as potential anti-cancer agents.

Interspecies Anticancer and Antimicrobial Activities of Genus Solanum and Estimation of Rutin by Validated UPLC-PDA Method

Solanaceae is one of the highly diverse plant families of which Solanum is the largest genera (1700 species) containing several pharmacological properties like anticancer and antimicrobial. This motivated us to explore the anticancer (against HepG2, HEK-293, and MCF-7 cells) and antimicrobial (against S. aureus, E. coli, P. aeruginosa, and C. albicans) properties of S. schimperianum, S. villosum, S. coagulans, S. glabratum, S. incanum, and S. nigrum along with rutin estimation by UPLC-PDA method. Of the studied Solanum extracts, S. nigrum exhibited significant cytotoxic property against HepG2 (IC50: 20.4 μg/mL) and MCF-7 (IC50: 30.1 μg/mL); S. coagulans showed toxicity against HepG2 (IC50: 28.4 μg/mL) and HEK-293 cells (IC50: 25.7 μg/mL) compared to 5-Fluorouracil (standard). Compared to these, extracts of S. coagulans and S. glabratum exhibited relatively high antimicrobial potency (MIC: 0.4-1.6 mg/mL). Nonetheless, all Solanum extracts significantly reduced the biofilm against PAO1-strain. Rutin was detected in all extracts with the highest content (53.79 μg/mg) in S. coagulans that supported its strong antimicrobial and anticancer properties. Molecular docking analysis showing strong binding of rutin with human DNA and proteins (DNA Topoisomerase IIα and E. coli DNA gyrase B) supported the anticancer and antimicrobial activities of Solanum species.

Design and evaluation of a novel flavonoid-based radioprotective agent utilizing monoglucosyl rutin

In this study, three novel flavonoid composite materials, created by combining an aglycone [quercetin (QUE), hesperetin (HES) or naringenin (NAR)] with monoglucosyl rutin (MGR), were designed to test for improved radioprotectivity compared with that provided by administration of MGR alone. Aglycone in the MGR-composite state was highly soluble in water, compared with aglycone alone dissolved in dimethyl sulfoxide or distilled water. The antioxidant activity of the three flavonoid composites was as high as that of MGR only. Next, the cytotoxicity test after 30 min treatment of an MGR composite showed a clear reduction in cell viability and suggested that a rapid introduction of aglycone into cells had taken place. In addition, QUE/MGR and HES/MGR composites strongly scavenged intracellular reactive oxygen species (ROS) induced by X-ray irradiation as well as MGR alone did. However, in the colony-formation assay using irradiated Chinese hamster ovary (CHO) cells, the HES/MGR composite showed a stronger radioprotective effect than MGR alone did, but the QUE/MGR composite showed no additional protective effect compared with the control. Furthermore, it was revealed that QUE and QUE/MGR composite treatment had the effect of reducing the glutathione (GSH) content in cells, and that QUE showed a stronger inhibition of PARP activity compared that of HES and NAR. Our data demonstrated that when designing a flavonoid composite as a radioprotective agent, it was necessary to select an appropriate aglycone, considering not only its antioxidant ability but also its inhibitory effect on cell recovery or DNA repair after radiation injury.

Novel PARP1/2 inhibitor mefuparib hydrochloride elicits potent in vitro and in vivo anticancer activity, characteristic of high tissue distribution

The approval of poly(ADP-ribose) polymerase (PARP) inhibitor AZD2281 in 2014 marked the successful establishment of the therapeutic strategy targeting homologous recombination repair defects of cancers in the clinic. However, AZD2281 has poor water solubility, low tissue distribution and relatively weak in vivo anticancer activity, which appears to become limiting factors for its clinical use. In this study, we found that mefuparib hydrochloride (MPH) was a potent PARP inhibitor, possessing prominent in vitro and in vivo anticancer activity. Notably, MPH displayed high water solubility (> 35 mg/ml) and potent PARP1/2 inhibition in a substrate-competitive manner. It reduced poly(ADP-ribose) (PAR) formation, enhanced γH2AX levels, induced G2/M arrest and subsequent apoptosis in homologous recombination repair (HR)-deficient cells. Proof-of-concept studies confirmed the MPH-caused synthetic lethality. MPH showed potent in vitro and in vivo proliferation and growth inhibition against HR-deficient cancer cells and synergistic sensitization of HR-proficient xenografts to the anticancer drug temozolomide. A good relationship between the anticancer activity and the PARP inhibition of MPH suggested that PAR formation and γH2AX accumulation could serve as its pharmacodynamic biomarkers. Its high bioavailability (40%~100%) and high tissue distribution in both monkeys and rats were its most important pharmacokinetic features. Its average concentrations were 33-fold higher in the tissues than in the plasma in rats. Our work supports the further clinical development of MPH as a novel PARP1/2 inhibitor for cancer therapy.

Histone Deacetylase Inhibitor Induced Radiation Sensitization Effects on Human Cancer Cells after Photon and Hadron Radiation Exposure

Suberoylanilide hydroxamic acid (SAHA) is a histone deacetylase inhibitor, which has been widely utilized throughout the cancer research field. SAHA-induced radiosensitization in normal human fibroblasts AG1522 and lung carcinoma cells A549 were evaluated with a combination of γ-rays, proton, and carbon ion exposure. Growth delay was observed in both cell lines during SAHA treatment; 2 μM SAHA treatment decreased clonogenicity and induced cell cycle block in G1 phase but 0.2 μM SAHA treatment did not show either of them. Low LET (Linear Energy Transfer) irradiated A549 cells showed radiosensitization effects on cell killing in cycling and G1 phase with 0.2 or 2 μM SAHA pretreatment. In contrast, minimal sensitization was observed in normal human cells after low and high LET radiation exposure. The potentially lethal damage repair was not affected by SAHA treatment. SAHA treatment reduced the rate of γ-H2AX foci disappearance and suppressed RAD51 and RPA (Replication Protein A) focus formation. Suppression of DNA double strand break repair by SAHA did not result in the differences of SAHA-induced radiosensitization between human cancer cells and normal cells. In conclusion, our results suggest SAHA treatment will sensitize cancer cells to low and high LET radiation with minimum effects to normal cells.

Hypersensitivity of BRCA2 deficient cells to rosemary extract explained by weak PARP inhibitory activity

Rosemary extract is used in food additives and traditional medicine and has been observed to contain anti-tumor activity. In this study, rosemary extract is hypothesized to induce synthetic lethality in BRCA2 deficient cells by PARP inhibition. Chinese hamster lung V79 cells and its mutant cell lines, V-C8 (BRCA2 deficient) and V-C8 with BRCA2 gene correction were used. Rosemary extract and its major constituent chemicals were tested for their cytotoxicity by colony formation assay in cells of different BRCA2 status. The latter chemicals were tested for inhibitory effect of poly (ADP-ribose) polymerase (PARP) activity in vitro and in vivo. Rosemary has shown selective cytotoxicity against V-C8 cells (IC50 17 µg/ml) compared to V79 cells (IC50 26 µg/ml). Among tested chemicals, gallic acid and carnosic acid showed selective cytotoxicity to V-C8 cells along with PARP inhibitory effects. Carnosol showed comparative PARP inhibitory effects at 100 µM compared to carnosic acid and gallic acid, but the selective cytotoxicity was not observed. In conclusion, we predict that within rosemary extract two specific constituent components; gallic acid and carnosic acid were the cause for the synthetic lethality.

PARP Inhibition by Flavonoids Induced Selective Cell Killing to BRCA2-Deficient Cells

High consumption of dietary flavonoids might contribute to a reduction of cancer risks. Quercetin and its glycosides have PARP inhibitory effects and can induce selective cytotoxicity in BRCA2-deficient cells by synthetic lethality. We hypothesized that common flavonoids in diet naringenin, hesperetin and their glycosides have a similar structure to quercetin, which might have comparable PARP inhibitory effects, and can induce selective cytotoxicity in BRCA2-deficient cells. We utilized Chinese hamster V79 wild type, V-C8 BRCA2-deficient and its gene-complemented cells. In vitro analysis revealed that both naringenin and hesperetin present a PARP inhibitory effect. This inhibitory effect is less specific than for quercetin. Hesperetin was more cytotoxic to V79 cells than quercetin and naringenin based on colony formation assay. Quercetin and naringenin killed V-C8 cells with lower concentrations, and presented selective cytotoxicity to BRCA2-deficient cells. However, the cytotoxicity of hesperetin was similar among all three cell lines. Glycosyl flavonoids, isoquercetin and rutin as well as naringin showed selective cytotoxicity to BRCA2-deficient cells; hesperidin did not. These results suggest that flavonoids with the PARP inhibitory effect can cause synthetic lethality to BRCA2-deficient cells when other pathways are not the primary cause of death.

Targeting NAD+ degradation: The therapeutic potential of flavonoids for Alzheimer's disease and cognitive frailty

Flavonoids are efficacious candidates as pharmaceuticals or nutraceuticals in the treatment of Alzheimer's disease (AD), aging and other age-related chronic inflammatory diseases. Natural flavonoids reduce pathological hallmarks, extracellular amyloid deposits and neurofibrillary tangles by mediating amyloid precursor protein (APP) processing, Aβ accumulation and tau pathology. The antioxidant and anti-inflammatory actions as well as modulation of sirtuins and telomeres are also involved in the amelioration of aging, neurodegeneration and other age-related diseases. Recently, some flavonoids were shown to inhibit poly (ADP-ribose) polymerases (PARPs) and cyclic ADP-ribose (cADP) synthases (CD38 and CD157), elevate intracellular nicotinamide adenine dinucleotide⁺ (NAD⁺) levels and activate NAD⁺ dependent sirtuin -mediated signaling pathways. We summarized how flavonoids reduce the degradation of NAD⁺ with an emphasis on the mechanisms through which flavonoids affect the NAD⁺-sirtuin axis to protect against AD. Aging and age-related diseases as well as a decline in the physiological reserve are the risk factors for cognitive frailty. Flavonoids with multiple therapeutic targets may also be potential candidates for the prevention and treatment of cognitive frailty.

Luteolinidin Protects the Postischemic Heart through CD38 Inhibition with Preservation of NAD(P)(H)

We recently showed that ischemia/reperfusion (I/R) of the heart causes CD38 activation with resultant depletion of the cardiac NADP(H) pool, which is most marked in the endothelium. This NADP(H) depletion was shown to limit the production of nitric oxide by endothelial nitric oxide synthase (eNOS), which requires NADPH for nitric oxide production, resulting in greatly altered endothelial function. Therefore, intervention with CD38 inhibitors could reverse postischemic eNOS-mediated endothelial dysfunction. Here, we evaluated the potency of the CD38 inhibitor luteolinidin, an anthocyanidin, at blocking CD38 activity and preserving endothelial and myocardial function in the postischemic heart. Initially, we characterized luteolinidin as a CD38 inhibitor in vitro to determine its potency and mechanism of inhibition. We then tested luteolinidin in the ex vivo isolated heart model, where we determined luteolinidin uptake with aqueous and liposomal delivery methods. Optimal delivery methods were then further tested to determine the effect of luteolinidin on postischemic NAD(P)(H) and tetrahydrobiopterin levels. Finally, through nitric oxide synthase-dependent coronary flow and left ventricular functional measurements, we evaluated the efficacy of luteolinidin to protect vascular and contractile function, respectively, after I/R. With enhanced postischemic preservation of NADPH and tetrahydrobiopterin, there was a dose-dependent effect of luteolinidin on increasing recovery of endothelium-dependent vasodilatory function, as well as enhancing the recovery of left ventricular contractile function with increased myocardial salvage. Thus, luteolinidin is a potent CD38 inhibitor that protects the heart against I/R injury with preservation of eNOS function and prevention of endothelial dysfunction.

Polyphenols and DNA Damage: A Mixed Blessing

Polyphenols are a very broad group of chemicals, widely distributed in plant foods, and endowed with antioxidant activity by virtue of their numerous phenol groups. They are widely studied as putative cancer-protective agents, potentially contributing to the cancer preventive properties of fruits and vegetables. We review recent publications relating to human trials, animal experiments and cell culture, grouping them according to whether polyphenols are investigated in whole foods and drinks, in plant extracts, or as individual compounds. A variety of assays are in use to study genetic damage endpoints. Human trials, of which there are rather few, tend to show decreases in endogenous DNA damage and protection against DNA damage induced ex vivo in blood cells. Most animal experiments have investigated the effects of polyphenols (often at high doses) in combination with known DNA-damaging agents, and generally they show protection. High concentrations can themselves induce DNA damage, as demonstrated in numerous cell culture experiments; low concentrations, on the other hand, tend to decrease DNA damage.

Puerarin protects against CCl4-induced liver fibrosis in mice: possible role of PARP-1 inhibition

Liver fibrosis, which is the pathophysiologic process of the liver due to sustained wound healing in response to chronic liver injury, will eventually progress to cirrhosis. Puerarin, a bioactive isoflavone glucoside derived from the traditional Chinese medicine pueraria, has been reported to have many anti-inflammatory and anti-fibrosis properties. However, the detailed mechanisms are not well studied yet. This study aimed to investigate the effects of puerarin on liver function and fibrosis process in mice induced by CCl4. C57BL/6J mice were intraperitoneally injected with 10% CCl4 in olive oil(2mL/kg) with or without puerarin co-administration (100 and 200mg/kg intraperitoneally once daily) for four consecutive weeks. As indicated by the ameliorative serum hepatic enzymes and the reduced histopathologic abnormalities, the data collected showed that puerarin can protect against CCl4-induced chronic liver injury. Moreover, CCl4-induced development of fibrosis, as evidenced by increasing expression of alpha smooth muscle actin(α-SMA), collagen-1, transforming growth factor (TGF)-β and connective tissue growth factor(CTGF) in liver, were suppressed by puerarin. Possible mechanisms related to these suppressive effects were realized by inhibition on NF-κB signaling pathway, reactive oxygen species(ROS) production and mitochondrial dysfunction in vivo. In addition, these protective inhibition mentioned above were driven by down-regulation of PARP-1 due to puerarin because puerarin can attenuate the PARP-1 expression in CCl4-damaged liver and PJ34, a kind of PARP-1 inhibitor, mimicked puerarin's protection. In conclusion, puerarin played a protective role in CCl4-induced liver fibrosis probably through inhibition of PARP-1 and subsequent attenuation of NF-κB, ROS production and mitochondrial dysfunction.

Comparative Effect of Quercetin and Quercetin-3-O-β-d-Glucoside on Fibrin Polymers, Blood Clots, and in Rodent Models

The present study evaluates the in vitro, in vivo, and ex vivo antithrombotic and anticoagulant effect of two flavonoids: quercetin and quercetin-3-O-β-d-glucoside (isoquercetin). The present results have shown that quercetin and isoquercetin inhibit the enzymatic activity of thrombin and FXa and suppress fibrin clot formation and blood clotting. The prolongation effect of quercetin and isoquercetin against epinephrine and collagen-induced platelet activation may have been caused by intervention in intracellular signaling pathways including coagulation cascade and aggregation response on platelets and blood. The in vivo and ex vivo anticoagulant efficacy of quercetin and isoquercetin was evaluated in thrombin-induced acute thromboembolism model and in ICR mice. Our findings showed that in vitro and in vivo inhibitory effects of quercetin were slightly higher than that of quercetin glucoside, whereas in vitro and ex vivo anticoagulant effects of quercetin were weaker than that of quercetin glucoside because of their structural characteristics.

Data for induction of cytotoxic response by natural and novel quercetin glycosides

The flavonoids quercetin, and its natural glycosides isoquercetin and rutin, are phytochemicals commonly consumed in plant-derived foods and used as a food beverage additive. Semi-synthetic maltooligosyl isoquercetin, monoglucosyl rutin and maltooligosyl rutin were developed by synthetic glycosylation to improve their water solubility for food and other applications. Using a system of Chinese hamster ovary (CHO) cells, this study examined the differences in cytotoxic responses induced by short and continuous exposure of natural and synthetic flavonoids. By assessing cell viability after short term exposure and clonogenicity with continuous exposure under various flavonoids, quercetin aglycone is confirmed to be the most cytotoxic flavonoids, and heavily glucosylated maltooligosyl rutin was the least cytotoxic. The other heavily glucosylated maltooligosyl isoquercetin showed intermediate cytotoxicity and similar toxicity as isoquercetin.

Hyperthermia-induced radiosensitization in CHO wild-type, NHEJ repair mutant and HR repair mutant following proton and carbon-ion exposure

The DNA repair mechanisms involved in hyperthermia-induced radiosensitization with proton and carbon ion radiation exposure were investigated in the present study. In a previous study, Chinese hamster ovary (CHO) cells were exposed to low linear energy transfer (LET) photon radiation. These cells can be sensitized by hyperthermia as a result of inhibition of homologous recombination (HR) repair. The present study used wild-type, non-homologous end joining (NHEJ) and HR repair-deficient CHO cells to define the contributions of each repair pathway to cellular lethality following hyperthermia-induced hadron radiation sensitization. The cells were exposed to ionizing radiation, followed by hyperthermia treatment (42.5°C for 1 h). Hyperthermia-induced radiosensitization was determined by the colony formation assay and thermal enhancement ratio. HR repair-deficient cells exhibited no hyper-sensitization to X-rays, protons, or low and high LET carbon ions when combined with hyperthermia. Wild-type and NHEJ repair-deficient cells exhibited significant hyperthermia-induced sensitization to low LET photon and hadron radiation. Hyperthermia-induced sensitization to high LET carbon-ion radiation was less than at low LET radiation. Relative biological effectiveness (RBE) between radiation alone and radiation combined with hyperthermia cell groups was not significantly different in any of the cell lines, with the exception of wild-type cells exposed to high LET radiation, which exhibited a lower RBE in the combined group. The present study investigated additional cell lines to confirm the lower RBE observed in DNA repair-deficient cell lines. These findings suggested that hyperthermia-induced hyper-sensitization to hadron radiation is also dependent on inhibition of HR repair, as was observed with photon radiation in a previous study.

Targeting Human Poly(ADP-Ribose) Polymerase-1 with Natural Medicines and Its Potential Applications in Ovarian Cancer Therapeutics

Targeting poly(ADP-ribose) polymerase-1 (PARP-1) has been established as an efficient therapeutics for advanced ovarian cancer. In this study, we describe an integrated procedure that combines virtual computer screening and an experimental enzyme assay to discover novel potent PARP-1 inhibitors from more than 130000 commercially available natural products. The protocol employed a stepwise strategy to fast exclude typical PARP-1 non-binders and then performing rigorous prediction to identify promising candidates with high potency against PARP-1. Consequently, eight natural products were hit and tested to determine their inhibitory activities against the PARP-1 catalytic domain. From these, four compounds, i.e., puerarin, phloretin, chlorogenic acid, and biochanin A, were found to have high or moderate potencies with inhibitory IC₅₀ values of 6, 470, 25, and 86 nM, respectively. The values are comparable to that (IC₅₀  = 1.94 nM) of the FDA-approved agent olaparib. Structural and energetic analyses of the modeled structures of the PARP-1 catalytic domain complexed with the newly identified inhibitors revealed a common binding mode in the complexes: the active site of PARP-1 is composed of a thin polar helix and a flat non-polar pocket; the inhibitors can form a number of hydrogen bonds and electrostatic forces with the helix, while tightly packing against the pocket to define chemical interactions.

Validation of 64Cu-ATSM damaging DNA via high-LET Auger electron emission

Radioactive copper (II) (diacetyl-bis N4-methylthiosemicarbazone) (Cu-ATSM) isotopes were originally developed for the imaging of hypoxia in tumors. Because the decay of a (64)Cu atom is emitting not only positrons but also Auger electrons, this radionuclide has great potential as a theranostic agent. However, the success of (64)Cu-ATSM internal radiation therapy would depend on the contribution of Auger electrons to tumor cell killing. Therefore, we designed a cell culture system to define the contributions to cell death from Auger electrons to support or refute our hypothesis that the majority of cell death from (64)Cu-ATSM is a result of high-LET Auger electrons and not positrons or other low-LET radiation. Chinese hamster ovary (CHO) wild type and DNA repair-deficient xrs5 cells were exposed to (64)Cu-ATSM during hypoxic conditions. Surviving fractions were compared with those surviving gamma-radiation, low-LET hadron radiation, and high-LET heavy ion exposure. The ratio of the D(10) values (doses required to achieve 10% cell survival) between CHO wild type and xrs5 cells suggested that (64)Cu-ATSM toxicity is similar to that of high-LET Carbon ion radiation (70 keV/μm). γH2AX foci assays confirmed DNA double-strand breaks and cluster damage by high-LET Auger electrons from (64)Cu decay, and complex types of chromosomal aberrations typical of high-LET radiation were observed after (64)Cu-ATSM exposure. The majority of cell death was caused by high-LET radiation. This work provides strong evidence that (64)Cu-ATSM damages DNA via high-LET Auger electrons, supporting further study and consideration of (64)Cu-ATSM as a cancer treatment modality for hypoxic tumors.

Embracing synthetic lethality of novel anticancer therapies

INTRODUCTION

The significant challenge posed by cancer to human healthcare has led to the exploration of new approaches to combat it. Synthetic lethality (SL) is one such emerging area in the development of novel anticancer therapies. SL can be described as lethality (cell death) resulting from the combination of the two mutations, wherein the mutation in either of the two codependent genes in normal or cancer cells is viable. This concept is specifically being exploited in cancer research for selectively targeting specific tumor cells.

AREAS COVERED

In this review, the authors summarize studies of SL-based novel anticancer therapies. The review highlights some of the selected advances in DNA damage response pathway-related SL pairs, particularly poly (ADP-ribose) polymerase (PARP) and SL pairs involved in mitochondrial death signaling pathways published in the last 3 years.

EXPERT OPINION

Most of the currently used chemotherapeutic agents will destroy cells irrespective of whether they are cancer cells or fast growing normal cells; but SL is one of the approaches being developed with potential as a selective cancer therapy. PARP inhibitors, such as olaparib, are useful in BRCA mutated cancer cells and are also used in combination with other drug to enhance their efficacy. Research on PARP inhibitors is progressing at a good pace but there are still some significant challenges that must be addressed.