Alkaline Agarose Gel Research Articles

Abstract B010: A novel hybrid with anti-angiogenic and DNA crosslinking activities potently suppresses the growth of colorectal cancer cells and patient-derived organoids in mice

Abstract Background: Colorectal cancer (CRC) is the second-leading death of all cancers in the world. Metastasis is the basis for cause of death in patients with CRC. Currently, combination of anti-VEGF therapy and DNA damaging agents, such as Bevacizumab + FOLFOX, has become the first-line therapy in managing colorectal cancer progression. To mimic the first-line therapy, we have conjugated the angiogenesis inhibitory and the DNA damaging moieties to form a bifunctional hybrid molecule. The purpose of this study is to prove the efficacy and safety of the novel hybrid molecule in treatment of CRC cells in mouse models. Materials and methods: The novel hybrid molecule, designated as BO-2762, was synthesized as previously reported. The anti-proliferative activity was analyzed by PrestoBlue® assay in a variety of CRC cell lines and CRC patient derived organoids (PDO). DNA damage was analyzed by alkaline gel electrophoresis and comet assay. Antiangiogenic property was assessed using the docking model, in vitro tube formation, and in vivo angiogenesis methods. Anti-tumor efficacy of BO-2762 was determined using xenografts of CRC cell lines and PDOs at 20 mg/kg via tail vein injection. For safety profiling and toxicology study, the ICR mice model was adopted for various pathological analyses. Results: The values of anti-proliferative IC50 of BO-2762 against a panel of 11 CRC and 10 PDO cell lines were ranged between 0.5 to 4.5 µM. Subsequently, we demonstrated that BO-2762 induced DNA inter-strand cross-linking (ICL) by alkaline agarose gel electrophoresis. Apparently, ICLs caused significant cell cycle arrest at the S phase, and subsequently triggered apoptosis. The angiogenesis inhibition by BO-2762 was also confirmed by in vitro tube formation assay and Direct In Vivo Angiogenesis Assay. The anti-CRC activity of BO-2762 was assessed using xenografts of CRC cells, derived from metastatic sites (LoVo and SW620 cells) and from primary sites (LS1034 and HT-29 cells). Via tail vein injection of BO-2762 at 20 mg/kg for 10 times, the growth of LoVo, SW620, LS1034, and HT-29 cells was suppressed by 85.8%, 83.0%, 75.4%, and 44.8% respectively. In addition, BO-2762 also significantly suppressed the growth of metastatic PDOs (T53 and T112) by 90%. Biosafety analysis showed promising safety parameters in blood chemistry and major organs. Conclusions: Our present results have shown that conjugated hybrid molecule with DNA cross-linking and anti-angiogenic activity is likely a novel approach to treat patients with CRC. Citation Format: Vaikar Navakanth Rao, Kuo-Chu Lai, Chin-Hung Liu, Shung-Haur Yang, Jeou-Yuan Chang, Tsann-Long Su, Te-Chang Lee. A novel hybrid with anti-angiogenic and DNA crosslinking activities potently suppresses the growth of colorectal cancer cells and patient-derived organoids in mice [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr B010.

Alkaline Agarose Gel Electrophoresis.

Alkaline agarose gels are run at high pH, which causes each thymine and guanine residue to lose a proton and thus prevents the formation of hydrogen bonds with their adenine and cytosine partners. The denatured DNA is maintained in a single-stranded state and migrates through an alkaline agarose gel as a function of its size. Other denaturants such as formamide and urea do not work well because they cause the agarose to become rubbery.

Sickle cell trait among blood donors in the democratic republic of the Congo: which transfusion policy for Sickle cell patients?

BackgroundPrevalence of sickle cell trait is high in the Democratic Republic of Congo (DRC). Blood services, therefore, face the risk of collecting blood units from donors with sickle cell trait.ObjectiveThis study aimed to determine the frequency of haemoglobin S among blood donors in Kinshasa.Materials and MethodsThe study was carried out in the period from 1 January 2014 to 31 December 2015, and 250 blood donors, who gave their consent, were selected using convenience sampling method when donating blood at the National Blood Transfusion Centre in Kinshasa, the Democratic Republic of the Congo. For the testing, blood samples (2 ml) were obtained at the time of blood donation, added to EDTA tubes, mixed and processed within 24 h. The haemoglobin variants were determined by electrophoresis on alkaline agarose gel and confirmed on acid gel.ResultsAmong the 250 blood donors, 20·8 % were female and 79·2%, male. Blood donors in the age range from 25 to 29 years were the most represented, accounting for 23·2%. The youngest donor was 19 years old and the oldest, 58 years old. None of the donors were aware of the HbS status and all have donated previously. According to the haemoglobin variants, 23·6% were confirmed as AS and 76·4%, as AA.ConclusionThe proportion of blood donors with HbS is high in the DRC. The possibility of implementing the compulsory routine screening of sickle cell trait (SCT), using sickle cell rapid test, should be explored and the supply of blood units from donors with SCT to patients with sickle cell disease (SCD) should be avoided, whenever possible.

Design, synthesis and antitumour evaluation of pyrrolo[1,2-f]-phenanthridine and dibenzo[f,h]pyrrolo[1,2-b]isoquinoline derivatives

A series of 1,2-bis(hydroxymethyl)pyrrolo[1,2-f]phenanthridine derivatives and their alkyl (ethyl and isopropyl) carbamates and 12,13-bis(hydroxymethyl)-9,14-dihydro-dibenzo[f,h]pyrrolo[1,2-b]isoquinoline derivatives were synthesized for antiproliferative evaluation. The preliminary antitumour studies revealed that these two types of bis(hydroxymethyl) derivatives showed significant antitumour activities and were able to inhibit the growth of various human tumour cell lines in vitro. Several of the derivatives were demonstrated to cause DNA interstrand cross-links by an alkaline agarose gel shifting assay. These conjugates were cytotoxic to a variety of cancer cell lines by inducing DNA damage, delaying cell cycle progression in the G2/M phase and triggering apoptosis. Compound 21a, dissolved in a vehicle suitable for intravenous administration, was selected for antitumour studies in animal models. We demonstrated that at a dose that did not cause body weight loss in mice, compound 21a could significantly suppress the growth of tumour xenografts of human lung cancer H460 and colorectal cancer HCT-116 cells in nude mice. Our present results confirm the antitumour activities of these conjugates.

Crystal structure, DNA crosslinking and photo-induced cytotoxicity of oxovanadium(IV) conjugates of boron-dipyrromethene

Cis-dichloro-oxovanadium(IV) complexes [VO(L1/L2)Cl2], where L1 is N-(4-(5,5-difluoro-1,3,7,9-tetramethyl-5H-4ʎ4,5ʎ4-dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinin-10-yl)benzyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine in 1 and L2 is N-(4-(5,5-difluoro-2,8-diiodo-1,3,7,9-tetramethyl-5H-4ʎ4,5ʎ4-dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinin-10-yl)benzyl)-1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine in 2) having 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene as boron-dipyrromethene (BODIPY) appended dipicolylamine bases were prepared, characterized and their photocytotoxicity studied. X-ray crystal structure of 1 showed distorted octahedral geometry with a VIVON3Cl2 core having Cl-V-Cl angle of 91.93(4)°. The complexes showed variable solution conductivity properties. They were non-electrolytes in dry DMF at 25 °C but showed 1:1 electrolytic behavior in an aqueous medium due to dissociation of one chloride ligand as evidenced from the mass spectral study. Complexes 1 and 2 showed absorption bands at 500 and 535 nm, respectively. The calf thymus DNA melting study revealed their interaction through DNA crosslinking on exposure to light which was further confirmed from the alkaline agarose gel electrophoresis using plasmid supercoiled pUC19 DNA. Complex 2 showed disruption of the mitochondrial membrane potential in the JC-1 (1,1′,3,3′-tetraethyl-5,5′,6,6′-tetrachloroimidacarbocyanine iodide) assay. The complexes were photocytotoxic in visible light (400–700 nm, power: 10 J cm−2) in cervical cancer HeLa and breast cancer MCF-7 cells. Complex 2 having a photoactive diiodo‑boron-dipyrromethene moiety gave a singlet oxygen quantum yield (ΦΔ) value of ~0.6. It showed singlet oxygen mediated apoptotic photodynamic therapy activity with remarkably low IC50 (half maximal inhibitory concentration) value of ~0.15 μM. The cis-disposition of chlorides gave a cis-divacant 4-coordinate intermediate structure from the density functional theory (DFT) study thus mimicking the DNA crosslinking property of cisplatin.

Evaluation of hemogram in patients with homozygous sickle cell disease: about 87 cases

La drépanocytose homozygote, fait partie des hémoglobinopathies les plus fréquentes au Maroc. La drépanocytose est caractérisée par une grande variabilité d’expressions clinique et biologique qui dépendent des facteurs génétiques modulateurs et environnementaux. Elle se manifeste par une anémie régénérative de gravité très variable selon les individus. L’évolution spontanée en l’absence de traitement est le décès précoce. La drépanocytose est caractérisée par une grande variabilité d’expression clinique et biologique qui dépend des facteurs génétiques et environnementaux. Un tableau clinique sévère marqué par une fréquence de transfusion élevée et précoce, des complications infectieuses graves et une mortalité précoce. Un état inflammatoire constant caractérisé par des protéines inflammatoires élevées et état nutritionnel compromis. L’objectif est de déterminer le profil des paramètres hématologiques du drépanocytaire homozygote (SS) marocain au cours des stades stationnaires. Nous avons fait une étude descriptive transversale de 87 patients drépanocytaires (SS). Nous avons réalisé une étude biologique comportant: l’hémogramme avec étude morphologique des globules rouges en coloration MGG et numération automatique des réticulocytes. Les électrophorèses de l’hémoglobine à pH alcalin (8.8) sur gel d’agarose avec intégration densitométrique. L’âge moyen est de 13.22 ans ± 16.36 avec un sex- ratio (H/F) de 1.175 et des extrêmes allant de 0.6 à 36 ans. La répercussion de l’anémie sur le plan biologique, est intense chez 88.5% des patients, 67.8% ont une anémie normocytaire contre 29.9% présentant une microcytose, et 2.3% qui présentaient une macrocytose. Le degré d’anisocytose est lié au degré d’anémie, très évocatrice chez les drépanocytaires homozygotes S/S (95,4%). Une réticulocytose était observée chez nos patients (81,6%) et 52.9% présentaient une thrombocytose. Une leucocytose était observée chez 64.4% des patients et 80.5% ont présenté une neutropénie. Les paramètres de l’hémogramme serviront de base de comparaison lors des crises et permettront d’évaluer l’efficacité de la prise en charge par le clinicien. Les valeurs élevées des globules blancs, plaquettes et CCHM semblent déterminants dans l’expression sévère de la drépanocytose au Maroc. Le profil hématologique du drépanocytaire marocain montre des données semblables à celles rapportées en littérature chez ceux de l’Afrique centrale, avec une leucocytose. Les résultats de notre étude suggèrent que, la drépanocytose est un problème de santé le plus fréquent chez les marocains et que nos résultats sont comparables à ceux décrits dans le syndrome drépanocytaire majeur.

Thioredoxin, the Processivity Factor, Sequesters an Exposed Cysteine in the Thumb Domain of Bacteriophage T7 DNA Polymerase

Gene 5 protein (gp5) of bacteriophage T7 is a non-processive DNA polymerase. It achieves processivity by binding to Escherichia coli thioredoxin (trx). gp5/trx complex binds tightly to a primer-DNA template enabling the polymerization of hundreds of nucleotides per binding event. gp5 contains 10 cysteines. Under non-reducing condition, exposed cysteines form intermolecular disulfide linkages resulting in the loss of polymerase activity. No disulfide linkage is detected when Cys-275 and Cys-313 are replaced with serines. Cys-275 and Cys-313 are located on loop A and loop B of the thioredoxin binding domain, respectively. Replacement of either cysteine with serine (gp5-C275S, gp5-C313S) drastically decreases polymerase activity of gp5 on dA(350)/dT(25). On this primer-template gp5/trx in which Cys-313 or Cys-275 is replaced with serine have 50 and 90%, respectively, of the polymerase activity observed with wild-type gp5/trx. With single-stranded M13 DNA as a template gp5-C275S/trx retains 60% of the polymerase activity of wild-type gp5/trx. In contrast, gp5-C313S/trx has only one-tenth of the polymerase activity of wild-type gp5/trx on M13 DNA. Both wild-type gp5/trx and gp5-C275S/trx catalyze the synthesis of the entire complementary strand of M13 DNA, whereas gp5-C313S/trx has difficulty in synthesizing DNA through sites of secondary structure. gp5-C313S fails to form a functional complex with trx as measured by the apparent binding affinity as well as by the lack of a physical interaction with thioredoxin during hydroxyapatite-phosphate chromatography. Small angle x-ray scattering reveals an elongated conformation of gp5-C313S in comparison to a compact and spherical conformation of wild-type gp5.

Abstract 1765: Potent antitumor BO-1922, derivative of indolizino[6,7-b]indole, against human colon, lung, and pancreatic cancers in xenograft model

Abstract Our previously studies demonstrated that bis(hydroxymethyl)cyclopenta[a]indenes, which bear a bis(hydroxymethyl)pyrrolidine pharmacophore, exhibited potent antitumor activity in inhibiting various human tumor xenografts. We also demonstrated that these agents showed strong synergistic therapeutic efficacy in combination with arsenic trioxide (ATO) against acquire or inherited MDR human tumors in xenograft model (human lung H460 or bladder cancer resistant to cisplatin NTUB1/P). Based on these findings, we have recently synthesized a series of 1,2-bis(hydroxymethyl)indolizino[6,7-b]indols and their bis(alkylcarbomate) derivatives for antitumor evaluation. These new agents were easily prepared starting from L-tryptophane in 5 steps. The in vitro cytotoxicity studies showed that the newly synthesized derivatives possessed a broad spectrum of anticancer activity against human lymphoblastic leukemia and various solid tumor cell growth in vitro. Of these analogues, 1,2-bis(hydroxymethyl)-3,6-dimethylindolizino[6,7-b]indole (BO-1922) was selected for further antitumor studies. We found that this agent displayed potent therapeutic efficacy against human colon cancer HT-29, lung adenocarcinoma lung A549, and primary pancreatic adenocarcinoma BX-PC3 xenografts. The antitumor activity of BO-1922 was compared with Irinotecan (CPT-11) in animal xenograft model. It revealed that BO-1922 is more potent than CPT-11 against human colon cancer HT-29 xenograft; complete tumor suppression on day 20 after mice treated with BO-1922 (25 mg/kg, QD×4, intravenous injection), while, tumor relapsed on day 9 after mice treated with CPT-11 (60 mg/kg, Q2D×3, iv. inj.). Under the same drug administration conditions (dosage and schedule), BO-1922 is as potent as CPT-11 against lung cancer A549 and pancreatic cancer BX-PC3 xenografts. Although the bodyweight of all drug treated mice recovered after ceasing of treatment, it was found that BO-1922 is less toxic to the host based on the average body-weight loss. The alkaline agarose gel shifting assay showed that this agent is able to induce DNA double strand cross-linking. Flow cytomeric assay revealed that BO-1922 induced cell cycle arrest at G1/S phase in non-small cell lung carcinomas H1299. These results suggest that BO-1922 is a promising candidate for clinical application and is currently undergoing preclinical studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1765. doi:1538-7445.AM2012-1765

Synthesis and antitumor evaluation of novel Benzo[d]pyrrolo[2,1-b]thiazole derivatives

A series of novel 2,3-bis(hydroxymethyl)benzo[d]pyrrolo[2,1-b]thiazoles and their bis(alkylcarbamate) derivatives were synthesized starting from benzothiazole via reaction with dimethyl acetylenedicarboxylate (DMAD)/tetra-fluoro boric acid, catalytic hydrogenation, and alkylcarbamoylation. The anti-proliferative activity of these agents against human leukemia and various solid tumor cell growth in vitro was studied. The structure–activity relationship studies revealed that the bis(alkylcarbamates) derivatives are generally more cytotoxic than the corresponding bis(hydroxymethyl) congeners in inhibiting human lymphoblastic leukemia CCRF-CEM and various human solid tumor cell growth in culture. These agents have no cross-resistance to taxol or vinblastine. Studies on the therapeutic effect against human breast carcinoma MX-1 xenograft showed that complete tumor remission (CR) were achieved by treating with C1-4′-F- or C1-4′-Cl-Ph-bis(i-propylcarbamates) derivatives (19b and 19c, respectively) and more than 99% tumor suppression by the corresponding bis(ethylcarbamates) 18b and 18c at the maximal tolerated dose. Alkaline agarose gel shifting assay revealed that the newly synthesized compounds are able to induce DNA interstrand cross-linking. The present studies generated a series of new potent DNA interstrand cross-linking agents, which have potential for further antitumor drug development.

Testicular Nuclear Receptor 4 (TR4) Regulates UV Light-induced Responses via Cockayne Syndrome B Protein-mediated Transcription-coupled DNA Repair

UV irradiation is one of the major external insults to cells and can cause skin aging and cancer. In response to UV light-induced DNA damage, the nucleotide excision repair (NER) pathways are activated to remove DNA lesions. We report here that testicular nuclear receptor 4 (TR4), a member of the nuclear receptor family, modulates DNA repair specifically through the transcription-coupled (TC) NER pathway but not the global genomic NER pathway. The level of Cockayne syndrome B protein (CSB), a member of the TC-NER pathway, is 10-fold reduced in TR4-deficient mouse tissues, and TR4 directly regulates CSB at the transcriptional level. Moreover, restored CSB expression rescues UV hypersensitivity of TR4-deficient cells. Together, these results indicate that TR4 modulates UV sensitivity by promoting the TC-NER DNA repair pathway through transcriptional regulation of CSB. These results may lead to the development of new treatments for UV light-sensitive syndromes, skin cancer, and aging.

Low-level infrared laser effect on plasmid DNA

Low-level laser therapy is used in the treatment of many diseases based on its biostimulative effect. However, the photobiological basis for its mechanism of action and adverse effects are not well understood. The aim of this study, using experimental models, was to evaluate the effects of laser on bacterial plasmids in alkaline agarose gel electrophoresis and Escherichia coli cultures. The electrophoretic profile of bacterial plasmids in alkaline agarose gels were used for studying lesions in DNA exposed to infrared laser. Transformation efficiency and survival of Escherichia coli AB1157 (wild-type), BH20 (fpg/mutM(-)), BW9091 (xth(-)), and DH5αF'Iq (recA(-)) cells harboring pBSK plasmids were used as experimental models to assess the effect of laser on plasmid DNA outside and inside of cells. Data indicate low-level laser: (1) altered the electrophoretic profile of plasmids in alkaline gels at 2,500-Hz pulsed-emission mode but did not alter at continuous wave, 2.5- and 250-Hz pulsed-emission mode; (2) altered the transformation efficiency of plasmids in wild-type and fpg/mutM(-) E. coli cells; (3) altered the survival fpg/mutM(-), xthA(-) and recA(-) E. coli cultures harboring pBSK plasmids. Low-level infrared laser with therapeutic fluencies at high frequency in pulsed-emission modes have effects on bacterial plasmids. Infrared laser action can differently affect the survival of plasmids in E. coli cells proficient and deficient in DNA repair mechanisms, therefore, laser therapy protocol should take into account fluencies, frequencies and wavelength of laser, as well as tissue conditions and genetic characteristics of cells before beginning treatment.

Abstract 2534: Novel and stable water-soluble N-mustards with potent therapeutic efficacy against human tumor xenografts in nude mice

Abstract The bioavailability of drugs is one of the important factors to determine whether a drug can be successfully developed for clinical application. Consequently, the physicochemical properties, including solubility, permeability, stability pKa, and lipophilicity/hydrophilicity balance, are key factors that influence the bioavailability of drugs. Compounds with poor solubility usually have a higher risk of difficulties to overcome during the period of new drug discovery and development because these properties may affect antitumor evaluations in animal models as well as pharmacokinetic and pharmacodynamic properties of the compound. In the present studies, we have synthesized a series of novel water-soluble N-mustard-benzene conjugates bearing a urea linker were synthesized. The benzene moiety contains a variety of hydrophilic side chains. These side chains are linked to the meta- or para-position of the urea linker via a carboxamide or an ether linkage. Compounds having a carboxamide hydrophilic side-chain can be converted into water-soluble hydrochloride or mesylate. The preliminary antitumor studies revealed that these conjugates exhibited potent cytotoxicity in vitro and antitumor therapeutic efficacy against human tumor xenografts in vivo. Furthermore, these derivatives have little or no cross-resistance to either Taxol or Vinblastine. Among these conjugates, compound WS-1707, which bearing a N,N-dimethylaminoethylcarboxamide hydrochloride water-soluble side-chain possessed potent therapeutic efficacy in nude mice bearing human breast carcinoma MX-1 (Remarkably, complete tumor remission in nude mice bearing human breast carcinoma MX-1 xenograft (complete tumor remission), prostate adenocarcinoma PC-3 xenograft (>99% suppression), and human colon cancer HCT-116 xenograft (>95% suppression) at the maximal tolerable dose 30 mg/kg, Q2D×5, intravenous injection. We also compared the therapeutic potency of WS-1707 with Carbopltin, and Doxetaxol in nude mice bearing prostate cancer HL2 xenograft (orthotopic implantation). It reveals that WS-1707 is as potent as Doxetaxol (>82% tumor suppression), but significantly more potent than Carboplatin. Study on the mechanism of action that this agent is able to induce DNA cross-linking through alkaline agarose gel shift assay. Early pharmacokinetic study shows that this conjugates has acceptable profile in rats with a half-life of 0.56 h. These results suggest that this agent is a promising candidate for preclinical studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2534. doi:10.1158/1538-7445.AM2011-2534

Design, synthesis and antitumor evaluation of phenyl N-mustard-quinazoline conjugates

A series of N-mustard-quinazoline conjugates was synthesized and subjected to antitumor studies. The N-mustard pharmacophore was attached at the C-6 of the 4-anilinoquinazolines via a urea linker. To study the structure–activity relationships of these conjugates, various substituents were introduced to the C-4 anilino moiety. The preliminary antitumor studies revealed that these agents exhibited significant antitumor activity in inhibiting various human tumor cell growths in vitro. Compounds 21b, 21g, and 21h were selected for further antitumor activity evaluation against human breast carcinoma MX-1 and prostate PC-3 xenograft in animal model. These agents showed 54–75% tumor suppression with low toxicity (5–7% body-weight changes). We also demonstrate that the newly synthesized compounds are able to induce DNA cross-linking through alkaline agarose gel shift assay and inhibited cell cycle arrest at G2/M phase.

Novel bifunctional alkylating agents, 5,10-dihydropyrrolo[1,2-b]isoquinoline derivatives, synthesis and biological activity

A series of linear pyrrolo[1,2-b]isoquinoline derivatives was synthesized for antitumor evaluation. The preliminary antitumor studies reveal that both bis(hydroxymethyl) and their bis(alkylcarbamate) derivatives show significant antitumor activity in inhibiting various human tumor cell growth in vitro. 1,2-Bis(hydroxymethyl)-3-methyl-5,10-dihydropyrrolo[1,2-b]isoquinoline (20a) was selected for antitumor studies in animal models. The results show that this agent can induce complete tumor remission or significant suppression in nude mice bearing human breast (MX-1) xenograft and ovarian (SK-OV-3) xenografts, respectively. Alkaline agarose gel shifting assay showed that 20a is able to cross-link with DNA. Studies on the cell cycle inhibition revealed that this agent induces cell arrest at G2/M phase. The results warrant further antitumor investigation against other human tumor growth in animal models.

Design, synthesis, and biological evaluation of novel water-soluble N-mustards as potential anticancer agents

A series of novel water-soluble N-mustard-benzene conjugates bearing a urea linker were synthesized. The benzene moiety contains various hydrophilic side chains are linked to the meta- or para-position of the urea linker via a carboxamide or an ether linkage. The preliminary antitumor studies revealed that these agents exhibited potent cytotoxicity in vitro and therapeutic efficacy against human tumor xenografts in vivo. Remarkably, complete tumor remission in nude mice bearing human breast carcinoma MX-1 xenograft and significant suppression against prostate adenocarcinoma PC3 xenograft were achieved by treating with compound 9aa' at the maximum tolerable dose with relatively low toxicity. We also demonstrate that the newly synthesized compounds are able to induce DNA cross-linking through alkaline agarose gel shift assay. A pharmacokinetic profile of the representative 9aa' in rats was also investigated. The current studies suggest that this agent is a promising candidate for preclinical studies.

Quantification of Cyclobutane Pyrimidine Dimers Induced by UVB Radiation in Conidia of the Fungi Aspergillus fumigatus, Aspergillus nidulans, Metarhizium acridum and Metarhizium robertsii

Conidia are responsible for reproduction, dispersal, environmental persistence and host infection of many fungal species. One of the main environmental factors that can kill and/or damage conidia is solar UV radiation. Cyclobutane pyrimidine dimers (CPD) are the major DNA photoproducts induced by UVB. We examined the conidial germination kinetics and the occurrence of CPD in DNA of conidia exposed to different doses of UVB radiation. Conidia of Aspergillus fumigatus, Aspergillus nidulans and Metarhizium acridum were exposed to UVB doses of 0.9, 1.8, 3.6 and 5.4 kJ m(-2). CPD were quantified using T4 endonuclease V and alkaline agarose gel electrophoresis. Most of the doses were sublethal for all three species. Exposures to UVB delayed conidial germination and the delays were directly related both to UVB doses and CPD frequencies. The frequencies of dimers also were linear and directly proportional to the UVB doses, but the CPD yields differed among species. We also evaluated the impact of conidial pigmentation on germination and CPD induction on Metarhizium robertsii. The frequency of dimers in an albino mutant was approximately 10 times higher than of its green wild-type parent strain after exposure to a sublethal dose (1.8 kJ m(-2)) of UVB radiation.

Two Modes of Interaction of the Single-stranded DNA-binding Protein of Bacteriophage T7 with the DNA Polymerase-Thioredoxin Complex

The DNA polymerase encoded by bacteriophage T7 has low processivity. Escherichia coli thioredoxin binds to a segment of 76 residues in the thumb subdomain of the polymerase and increases the processivity. The binding of thioredoxin leads to the formation of two basic loops, loops A and B, located within the thioredoxin-binding domain (TBD). Both loops interact with the acidic C terminus of the T7 helicase. A relatively weak electrostatic mode involves the C-terminal tail of the helicase and the TBD, whereas a high affinity interaction that does not involve the C-terminal tail occurs when the polymerase is in a polymerization mode. T7 gene 2.5 single-stranded DNA-binding protein (gp2.5) also has an acidic C-terminal tail. gp2.5 also has two modes of interaction with the polymerase, but both involve the C-terminal tail of gp2.5. An electrostatic interaction requires the basic residues in loops A and B, and gp2.5 binds to both loops with similar affinity as measured by surface plasmon resonance. When the polymerase is in a polymerization mode, the C terminus of gene 2.5 protein interacts with the polymerase in regions outside the TBD. gp2.5 increases the processivity of the polymerase-helicase complex during leading strand synthesis. When loop B of the TBD is altered, abortive DNA products are observed during leading strand synthesis. Loop B appears to play an important role in communication with the helicase and gp2.5, whereas loop A plays a stabilizing role in these interactions.

Abstract 3517: Complete remission of xenograft tumor in nude mice induced by N-mustard-quinoline conjugates bearing hydrazinecarboxamide linker

Abstract Designing DNA-directed alkylating agents is a promising strategy to overcome the drawbacks of alkylating agents by enhancing DNA specific cross-linking and reducing the chemical reactivity of N-mustard. These compounds are generally synthesized by linking the alkylating warhead (such as alkyl or phenyl N-mustard pharmacophore) to the DNA-affinic carrier (such as DNA intercalating or groove binding agents). Recently, we reported that N-mustard-9-anilinoacridine conjugates via a urea, carbamate, or carbonate linker exhibited potent cytotoxicity and therapeutic efficacy against various human tumor xenografts indicating that these linkers are able to stabilize the reactive alkylating war head. Thus, these derivatives have a long half-life in plasma. Some of these conjugates are able to induce complete tumor remission (CR) in inhibiting human tumor xenograft model with low toxicity. To continue our research in finding potent DNA-directed alkylating agents, we have recently synthesized a series of N-mustard-quinoline conjugates bearing a hydrazinecarboxamide linker. These conjugates were prepared in good yield by the condensation of appropriate 4-hydrazinoquinolines with 4-bis(2-chloroethyl)- aminophenyl isocynate. The results showed that these conjugates possessed significant cytotoxicity against human lymphoblastic leukemia (CCRF-CEM) and various solid tumor xenografts (such as MX-1, HCT-116, H1299, CL 1-0, CL 1-5, PC3 and MCF-7) cell growth in vitro. Among these agents, BO-1392 and BO-1393 were able to induce CR against human breast carcinoma MX-1 xenograft and significantly suppress against human ovarian SK-OV3 xenograft in animal model with relative low toxicity. Interestingly, we found that BO-1393 (iv. injection) can significantly prolong the life span of nude mice bearing human glioma SK-NA-S xenograft (orthotropic implanted in brain). The experiment was compared with Temozolomide (oral administration). The modified comet assay and alkaline agarose gel shift assay showed that these conjugates are capable of inducing DNA interstrand cross-linking in human non-small lung cancer H1299 cells. In conclusion, the present studies demonstrated that the newly synthesized N-mustard-quinoline conjugates having a hydrazinecarboxamide linker exhibited a broad spectrum of antitumor activity and are chemically stable. The remarkable therapeutic efficacy of BO-1393 demonstrated that this agent has high potential for clinical development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3517.

Potent DNA-directed alkylating agents: Synthesis and biological activity of phenyl N-mustard–quinoline conjugates having a urea or hydrazinecarboxamide linker

A series of N-mustard–quinoline conjugates bearing a urea or hydrazinecarboxamide linker was synthesized for antitumor evaluation. The in vitro cytotoxicity studies revealed that compounds with hydrazinecarboxamide linkers were generally more cytotoxic than the corresponding urea counterparts in inhibiting human lymphoblastic leukemia and various solid tumor cell growths in culture. The therapeutic efficacy against human tumor xenografts in animal model was studied. It was shown that complete tumor remission in nude mice bearing human breast carcinoma MX-1 xenograft by 17a, i and 18c, d was achieved. In the present study, it was revealed that both linkers are able to lower the chemically reactive N-mustard pharmacophore and thus the newly synthesized conjugates possess a long half-life in rat plasma. Moreover, the new N-mustard derivatives are able to induce DNA cross-linking either by modified comet assay or by alkaline agarose gel shift assay.

Evidence for the Failure of Adeno-associated Virus Serotype 5 to Package a Viral Genome ≥8.2 kb

Limited packaging capacity hinders adeno-associated virus (AAV) gene therapy. A recent study seems to have provided a solution to this problem. Allocca et al. reported that AAV-5 could package an 8.9 kb vector genome. Here we tested whether this approach can be used to deliver a large genome for Duchenne muscular dystrophy (DMD) gene therapy. We first evaluated AAV-5 packaging of an 8.2 kb genome. This vector carries two independent reporter gene cassettes, one for alkaline phosphatase (AP) and another for LacZ. Viral yield was log-fold lower than that of a regular AAV-5. Nevertheless, both AP and LacZ genes were detected in purified virus. Injection to dystrophic muscle resulted in both AP and LacZ expression. On electron microscopy, virion structure appeared normal. Surprisingly, we did not find the full-length single-stranded viral genome by alkaline gel electrophoresis. Neither did we see the full-length double-stranded replication forms in adenovirus coinfected cells. We suspect that AP and LacZ expression may have come from partially packaged 5' or 3'-half of the genome. Additional studies revealed failure of AAV-5 to package and express an 8.7 kb minidystrophin gene cassette. In summary, our results do not support the extraordinary packaging capacity of AAV-5.