Investigation of the DNA damage response to SFOM-0046, a new small-molecule drug inducing DNA double-strand breaks

N-Phenyl ureidobenzenesulfonates, a novel class of human dihydroorotate dehydrogenase inhibitors inducing differentiation and apoptosis in acute myeloid leukemia cells

N-Phenyl ureidobenzensulfonates (PUB-SOs) are a novel family of dihydroorotate dehydrogenase (DHODH) inhibitors. Herein, we investigate the potential of PUB-SOs to induce acute myeloid leukemia (AML) cell differentiation and apoptosis. To that end, we screened our chemolibrary to select the most potent PUB-SOs based on their antiproliferative activity and their ability to arrest the cell progression of AML cells in the S phase. The most promising PUB-SOs show antiproliferative activity in the range of 0.13-23 µM against THP-1, MOLM-13 and HL-60 AML cells. Moreover, those PUB-SOs arrested the cell cycle progression in the S phase. In addition, molecular docking studies evidenced their potential to bind in the brequinar-binding site located on DHODH which was confirmed using the DHODH inhibition assay showing that PUB-SOs are potent DHODH inhibitors (half maximal inhibitory concentration (IC50) = 7.7-1000 nM). Our results also show that selected PUB-SOs induced the differentiation of THP-1 and HL-60 cells into cluster of differentiation (CD) 11b+/CD14+ phenotypes, up to 74 % and 50 %, respectively. They also promoted CD11b+ differentiation in MOLM-13 cells (up to 44 %). Additionally, the prototypical PUB-SOs SFOM-0046 induced lactate dehydrogenase (LDH) release, mitochondrial stress and mitochondrial membrane potential loss in MOLM-13 cell line. Furthermore, SFOM-0046 induced apoptosis in MOLM-13 cells, which was confirmed by the increase of annexin V/propidium iodide (PI) and caspase 3/7 positive cells. In summary, our results highlight PUB-SOs as a novel family of DHODH inhibitors inducing both cell differentiation and apoptosis in AML cells, underscoring their potential as therapeutic agents for AML treatment.

Evaluation of DNA double-strand break repair capacity in human cells: Critical overview of current functional methods

DNA double-strand breaks (DSBs) are highly deleterious lesions, responsible for mutagenesis, chromosomal translocation or cell death. DSB repair (DSBR) is therefore a critical part of the DNA damage response (DDR) to restore molecular and genomic integrity. In humans, this process is achieved through different pathways with various outcomes. The balance between DSB repair activities varies depending on cell types, tissues or individuals. Over the years, several methods have been developed to study variations in DSBR capacity. Here, we mainly focus on functional techniques, which provide dynamic information regarding global DSB repair proficiency or the activity of specific pathways. These methods rely on two kinds of approaches. Indirect techniques, such as pulse field gel electrophoresis (PFGE), the comet assay and immunofluorescence (IF), measure DSB repair capacity by quantifying the time-dependent decrease in DSB levels after exposure to a DNA-damaging agent. On the other hand, cell-free assays and reporter-based methods directly track the repair of an artificial DNA substrate. Each approach has intrinsic advantages and limitations and despite considerable efforts, there is currently no ideal method to quantify DSBR capacity. All techniques provide different information and can be regarded as complementary, but some studies report conflicting results. Parameters such as the type of biological material, the required equipment or the cost of analysis may also limit available options. Improving currently available methods measuring DSBR capacity would be a major step forward and we present direct applications in mechanistic studies, drug development, human biomonitoring and personalized medicine, where DSBR analysis may improve the identification of patients eligible for chemo- and radiotherapy.

PARP1-Inhibition Sensitizes Cervical Cancer Cell Lines for Chemoradiation and Thermoradiation

Simple Summary

Five-year survival rates from patients with locally advanced cervical cancer (LACC) are between 40% and 60%. These patients are usually treated with chemoradiation or radiotherapy in combination with hyperthermia (thermoradiation). The aim of our study was to enhance chemoradiation or thermoradiation by adding PARP1-inhibition to these conventional therapies. To study this, different cervical cancer cell lines were used to measure cell reproductive death and analyze DNA double strand breaks and cell death. By looking into the surviving fractions and DNA double strand breaks, our results suggest that PARP1-i sensitizes cervical cancer cells for the conventional therapies. The results of the live cell imaging suggest that effects are solely additive.

Abstract

Radiotherapy plus cisplatin (chemoradiation) is standard treatment for women with locoregionally advanced cervical cancer. Both radiotherapy and cisplatin induce DNA single and double-strand breaks (SSBs and DSBs). These double-strand breaks can be repaired via two major DNA repair pathways: Classical Non-Homologous End-Joining (cNHEJ) and Homologous Recombination. Besides inducing DNA breaks, cisplatin also disrupts the cNHEJ pathway. Patients contra-indicated for cisplatin are treated with radiotherapy plus hyperthermia (thermoradiation). Hyperthermia inhibits the HR pathway. The aim of our study is to enhance chemoradiation or thermoradiation by adding PARP1-inhibition, which disrupts both the SSB repair and the Alternative NHEJ DSB repair pathway. This was studied in cervical cancer cell lines (SiHa, HeLa, C33A and CaSki) treated with hyperthermia (42 °C) ± ionizing radiation (2–6 Gy) ± cisplatin (0.3–0.5 µM) ± PARP1-inhibitor (olaparib, 4.0–5.0 µM). Clonogenic assays were performed to measure cell reproductive death. DSBs were analyzed by γ-H2AX staining and cell death by live cell imaging. Both chemoradiation and thermoradiation resulted in lower survival fractions and increased unrepaired DSBs when combined with a PARP1-inhibitor. A quadruple modality, including ionizing radiation, hyperthermia, cisplatin and PARP1-i, was not more effective than either triple modality. However, both chemoradiation and thermoradiation benefit significantly from additional treatment with PARP1-i.

Pinocembrin attenuates benzo(a)pyrene-induced CYP1A1 expression through multiple pathways: An in vitro and in vivo study

Benzo(a)pyrene [B(a)P], which is a carcinogen, is a substance most typically known in cigarette smoke and considered as an important intermediary of lung cancer. The enzyme CYP1A1 is crucial for the metabolic conversion of B(a)P into the intermediates that induce carcinogenesis. Stimulation of the aryl hydrocarbon receptor, which is regulated by B(a)P, is thought to induce numerous signaling cascades. Interruption in the mitogen-activated protein kinase (MAPK) pathway causes changes in cellular processes and may alter the AhR pathway. The aim of this investigation is to examine the potential ability of a flavonoid pinocembrin (PCB) to alleviate B(a)P toxicity and analyze the underlying molecular mechanisms. We found that PCB inhibited DNA adduct formation by attenuating CYP1A1 expression through the suppression of the AhR/Src/ERK pathways. PCB mitigated the B(a)P-stimulated DNA damage, inhibited Src and ERK1/2 expression, decreased CYP1A1 expression, and reduced the B(a)P-induced stimulation of NF-κB and MAPK signaling in lung epithelial cells. Finally, the activity of CYP1A1 and Src in lung tissues from mice supplemented with PCB was noticeably decreased and lower than that in lung tissues from mice supplemented with B(a)P alone. Collectively, these data suggest that PCB may alleviate the toxic effects of PAHs, which are important environmental pollutants.

N-phenyl ureidobenzenesulfonates, a novel class of promising human dihydroorotate dehydrogenase inhibitors

N-phenyl ureidobenzenesulfonates (PUB-SOs) is a new class of promising anticancer agents inducing replication stresses and cell cycle arrest in S-phase. However, the pharmacological target of PUB-SOs was still unidentified. Consequently, the objective of the present study was to identify and confirm the pharmacological target of the prototypical PUB-SO named 2-ethylphenyl 4-(3-ethylureido)benzenesulfonate (SFOM-0046) leading to the cell cycle arrest in S-phase. The antiproliferative and the cytotoxic activities of SFOM-0046 were characterized using the NCI-60 screening program and its fingerprint was analyzed by COMPARE algorithm. Then, human dihydroorotate dehydrogenase (hDHODH) colorimetric assay, uridine rescuing cell proliferation and molecular docking in the brequinar-binding site were performed. As a result, SFOM-0046 exhibited a mean antiproliferative activity of 3.5 μM in the NCI-60 screening program and evidenced that leukemia and colon cancer cell panels were more sensitive to SFOM-0046. COMPARE algorithm showed that the SFOM-0046 cytotoxic profile is equivalent to the ones of brequinar and dichloroallyl lawsone, two inhibitors of hDHODH. SFOM-0046 inhibited the hDHODH in the low nanomolar range (IC₅₀ = 72 nM) and uridine rescued the cell proliferation of HT-29, HT-1080, M21 and MCF-7 cancer cell lines in the presence of SFOM-0046. Finally, molecular docking showed a binding pose of SFOM-0046 interacting with Met43 and Phe62 present in the brequinar-binding site. In conclusion, PUB-SOs and notably SFOM-0046 are new small molecules hDHODH inhibitors triggering replication stresses and S-phase arrest.

Anticancer Activity of Platinum (II) Complex with 2-Benzoylpyridine by Induction of DNA Damage, S-Phase Arrest, and Apoptosis

OBJECTIVE

To overcome the disadvantages of cisplatin, numerous platinum (Pt) complexes have been prepared. However, the anticancer activity and mechanism of Pt(II) complexed with 2-benzoylpyridine [Pt(II)- Bpy]: [PtCl2(DMSO)L] (DMSO = dimethyl sulfoxide, L = 2-benzoylpyridine) in cancer cells remain unknown.

METHODS

Pt(II)-Bpy was synthesized and characterized by spectrum analysis. Its anticancer activity and underlying mechanisms were demonstrated at the cellular, molecular, and in vivo levels.

RESULTS

Pt(II)-Bpy inhibited tumor cell growth, especially HepG2 human liver cancer cells, with a halfmaximal inhibitory concentration of 9.8±0.5μM, but with low toxicity in HL-7702 normal liver cells. Pt(II)- Bpy induced DNA damage, which was demonstrated through a marked increase in the expression of cleavedpoly (ADP ribose) polymerase (PARP) and gamma-H2A histone family member X and a decrease in PARP expression. The interaction of Pt(II)-Bpy with DNA at the molecular level was most likely through an intercalation mechanism, which might be evidence of DNA damage. Pt(II)-Bpy initiated cell cycle arrest at the S phase in HepG2 cells. It also caused severe loss of the mitochondrial membrane potential; a decrease in the expression of caspase-9 and caspase-3; an increase in reactive oxygen species levels; the release of cytochrome c and apoptotic protease activation factor; and the activation of caspase-9 and caspase-3 in HepG2 cells, which in turn resulted in apoptosis. Meanwhile, changes in p53 and related proteins were observed including the upregulation of p53, the phosphorylation of p53, p21, B-cell lymphoma-2-associated X protein, and NOXA; and the downregulation of B-cell lymphoma 2. Moreover, Pt(II)-Bpy displayed marked inhibitory effects on tumor growth in the HepG2 nude mouse model.

CONCLUSION

Pt(II)-Bpy is a potential candidate for cancer chemotherapy.

Targeting DNA Repair through Podophyllotoxin and Rutin Formulation in Hematopoietic Radioprotection: An in Silico, in Vitro, and in Vivo Study

Drug discovery field has tremendously progressed during last few decades, however, an effective radiation countermeasure agent for the safe administration to the victims of radiation exposure is still unavailable. This multi-model study is aimed at elucidating the mechanistic aspects of a novel podophyllotoxin and rutin combination (henceforth referred as G-003M) in the hematopoietic radioprotection and its involvement in the DNA damage and repair signaling pathways. Using in silico study, we identified the binding sites and structural components of G-003M and validated in vitro. We further studied various in vivo endpoints related to the DNA repair and cell death pathways in mice pre-administered with G-003M, irradiated and subsequently euthanized to collect blood and bone marrow cells. In silico study showed the binding of podophyllotoxin to β-tubulin and presence of a functional hydroxyl group in the rutin, suggested their involvement in G2/M arrest and the free radical scavenging respectively. This experimentation was further validated through in vitro studies. In vivo mice studies confirmed that G-003M pre-administration attenuated DNA damage and enhanced repair after whole body exposure. We further noticed a decrease in the levels of γH2AX, p53BP1, and ATM kinase and an increase in the levels of DNA pk, Ku 80, Ligase IV, Mre 11, Rad 50 and NBS 1 in the blood and bone marrow cells of the G-003M pre-administered and irradiated mice. We noticed an overall increase in the pro-survival factors in the G-003M pre-treated and irradiated groups establishing the radioprotective efficacy of this formulation. The lead obtained from this study will certainly help in developing this formulation as a safe and effective radioprotector which could be used for humans against any planned or emergency exposure of radiation.

Elastic-Fluid Model for DNA Damage and Mutation from Nuclear Fluid Segregation Due to Cell Migration

When cells migrate through constricting pores, they incur DNA damage and develop genomic variation. Experiments show that this damage is not due to DNA breakage from mechanical stress on chromatin in the deformed nucleus. Here we propose a model for a mechanism by which nuclear deformation can lead to DNA damage. We treat the nucleus as an elastic-fluid system with an elastic component (chromatin) and fluid component that can be squeezed out when the nucleus is deformed. We couple the elastic-fluid model to the kinetics of DNA breakage and repair by assuming that the local volume fraction of the elastic component controls the rate of damage per unit volume due to naturally occurring DNA breaks, whereas the volume fraction of the fluid component controls the rate of repair of DNA breaks per unit volume by repair factors, which are soluble in the fluid. By comparing our results to a number of experiments on controlled migration through pores, we show that squeeze-out of the fluid, and hence of the mobile repair factors, is sufficient to account for the extent of DNA damage and genomic variation observed experimentally. We also use our model for migration through a cylindrical pore to estimate the variation with tissue stiffness of the mutation rate in tumors.

Activation of Phenyl 4-(2-Oxo-3-alkylimidazolidin-1-yl)benzenesulfonates Prodrugs by CYP1A1 as New Antimitotics Targeting Breast Cancer Cells

Prodrug-mediated utilization of the cytochrome P450 (CYP) 1A1 to obtain the selective release of potent anticancer products within cancer tissues is a promising approach in chemotherapy. We herein report the rationale, preparation, biological evaluation, and mechanism of action of phenyl 4-(2-oxo-3-alkylimidazolidin-1-yl)benzenesulfonates (PAIB-SOs) that are antimicrotubule prodrugs activated by CYP1A1. Although PAIB-SOs are inert in most cells tested, they are highly cytocidal toward several human breast cancer cells, including hormone-independent and chemoresistant types. PAIB-SOs are N-dealkylated into cytotoxic phenyl 4-(2-oxo-3-imidazolidin-1-yl)benzenesulfonates (PIB-SOs) in CYP1A1-positive cancer cells, both in vitro and in vivo. In conclusion, PAIB-SOs are novel chemotherapeutic prodrugs with no equivalent among current antineoplastics and whose selective action toward breast cancer is tailored to the characteristic pattern of CYP1A1 expression observed in a large percentage of human breast tumors.

The natural terthiophene α-terthienylmethanol induces S phase cell cycle arrest of human ovarian cancer cells via the generation of ROS stress

Ovarian cancer is the most lethal gynecological malignancy worldwide. Thiophenes such as terthiophene have been shown to have anti-tumor effects on several cancer cell lines, including ovarian cancer cells. However, the underlying mechanisms behind the anti-proliferative effect of thiophenes are poorly understood. In this study, we investigated the molecular mechanisms underlying the anti-proliferative effect of α-terthienylmethanol, a terthiophene isolated from Eclipta prostrata (False Daisy), on human ovarian cancer cells. We found that α-terthienylmethanol is a more potent inhibitor of cell growth than is cisplatin in human ovarian cancer cells. α-Terthienylmethanol induces cell cycle arrest in ovarian cancer cells, as shown by the accumulation of cells in S phase. In addition, α-terthienylmethanol induced a change in S phase-related proteins cyclin A, cyclin-dependent kinase 2, and cyclin D2. Knockdown of cyclin A using specific siRNAs significantly compromised α-terthienylmethanol-induced S phase arrest. We further demonstrated that α-terthienylmethanol induced an increase in intracellular ROS, and the antioxidant N-acetyl-l-cysteine significantly reversed the S phase arrest induced by α-terthienylmethanol. Moreover, α-terthienylmethanol significantly increased the levels of p-H2AX, a DNA damage marker. These results suggest that α-terthienylmethanol inhibits the growth of human ovarian cancer cells by S phase cell cycle arrest via induction of ROS stress and DNA damage.