Evaluation of apoptosis-induction by newly synthesized phthalazine derivatives in breast cancer cell lines.

Newly synthesized phthalazine derivatives including copper and platinum complexes were evaluated for cytotoxicity in human breast cancer cell lines. The cells were incubated with the compounds (100 microM) for 72 h and cytotoxicity, apoptosis and DNA content were measured by flow cytometery. Our results suggest that the parent (H1-2), copper (C1-2)- and platinum (P1-2)-derivatized compounds were relatively more active in inducing apoptosis and cell killing in both human breast cancer cell lines, MDA-MB-231 cells being the more sensitive.

Defective repair of UV-induced DNA damage in cultured primary skin fibroblasts from Saudi thyroid cancer patients.

This study was conducted to examine the sensitivity of primary skin fibroblasts from Saudi thyroid cancer (TC) patients to ultraviolet (UV) irradiation. Cell survival was studied by a colony forming assay and DNA repair defects with a host cell reactivation (HCR) assay using UV-irradiated Herpes Simplex Virus (HSV). In addition, p53 gene expression was examined in the same TC cells exhibiting enhanced radiosensitivity.

Novel Marine Compounds: Anticancer or Genotoxic?

In the past several decades, marine organisms have generously gifted to the pharmaceutical industries numerous naturally bioactive compounds with antiviral, antibacterial, antimalarial, anti-inflammatory, antioxidant, and anticancer potentials. But till date only few anticancer drugs (cytarabine, vidarabine) have been commercially developed from marine compounds while several others are currently in different clinical trials. Majority of these compounds were tested in the tumor xenograft models, however, lack of anticancer potential data in the chemical- and/or oncogene-induced pre-initiation animal carcinogenesis models might have cost some of the marine anticancer compounds an early exit from the clinical trials.

Synthesis, characterization and cytotoxicity evaluation of some new platinum(II) complexes of tetrazolo[1,5-a]quinolines.

Several new platinum(II) complexes of the general formulae cis-[PtCl(2)(DMSO)L], where L is a Schiff base or hydrazone derived from tetrazolo[1,5-a]quinoline-4-carboxaldehyde as carrier ligands, have been synthesized and characterized physicochemically and spectroscopically. These platinum complexes which are structurally analogues to what so called cisplatin [cis-[PtCl2(NH3)2]; the first generation anticancer agent] were evaluated for their cytotoxicity on HL-60 (human promyelocytic leukemia) cells. Two of the platinum complexes were almost similar in their activity to cisplatin, while the remaining three complexes have demonstrated higher efficacy than that of cisplatin.

Multiplicity of strand incision at G:T base mismatches in DNA by human cell extracts.

Cell extract from the HT29 human colon carcinoma cell line (lacking mutator phenotype) was used to study the ATP-dependent G:T mismatch repair. We found that when a 45-bp (model) DNA with a single CpG/TpG mispair was incubated with the cell extract and ATP, it was incised immediately 5' and 3' to the mismatched T, and we noted that the actual 5'- and 3'-labeled fragments were similar to the cleaved products of thymine DNA glycosylase (TDG). This TDG-like cleavage product was enhanced (5-fold) with stimulation of several novel fragments, as inferred from the effect on incision at CpG/TpG site of the addition of G:U competitor DNA and ATP to the HT29 extract.

Deficiency in the repair of UV-induced DNA damage in human skin fibroblasts compromised for the ATM gene.

Ataxia-telangiectasia (A-T), is an autosomal recessive disease characterized by neurological and immunological symptoms, radiosensitivity and cancer predisposition. A-T cells exhibit a greatly decreased survival and a reduction in DNA synthesis inhibition as well as p53 induction in response to ionizing radiation. Occasionally, some strains of A-T cells have been reported to manifest a slightly enhanced sensitivity with no consistent observations of a deficiency in either cell cycle control or the repair of DNA damage after treatment with ultraviolet (UV) light.

Substrate specificity and sequence preference of G:T mismatch repair: incision at G:T, O6-methylguanine:T, and G:U mispairs in DNA by human cell extracts.

Extracts of two human glioma cell lines (lacking O6-methylguanine DNA-methyltransferase) (i.e., A1235 and its alkylation-resistant derivative A1235-MR4) were examined for their ability to execute strand incision at different base mismatches in model (45-bp) DNA.

p53 is dispensable for UV-induced cell cycle arrest at late G(1) in mammalian cells.

Genotoxic agents, including gamma-rays and UV light, induce transient arrest at different phases of the cell cycle. These arrests are required for efficient repair of DNA lesions, and employ several factors, including the product of the tumor suppressor gene p53 that plays a central role in the cellular response to DNA damage. p53 protein has a major function in the gamma-ray-induced cell cycle delay in G(1) phase.

Cellular radiosensitivity of patients with papillary thyroid cancer.

Cultured skin fibroblasts from patients with papillary (differentiated) thyroid carcinomas were compared to those from healthy subjects, ataxia telangiectasia (AT) homozygotes and AT heterozygotes for colony-forming ability after low dose-rate irradiation, and post-irradiation DNA synthesis as indicated by uptake of [3H]-thymidine. The cells from the cancer patients exhibited enhanced radiosensitivity (intermediate between normal and AT) and less than normal level of radioinduced inhibition of DNA synthesis.

Exposure of organic extracts of air particulates to sunlight leads to metabolic activation independence for mutagenicity.

Air particulates were collected on Whatman, GFA glass fibre filters using a RADECO constant-flow air sampler from a car-parking basement and an open roadside adjacent to the basement. While the basement was not exposed to sunlight, the roadside from where air samples were collected was exposed to regular daylight in the month of July (peak summer month). The filters were soaked and sonicated in acetone to dislodge the particulates and then a residue was obtained after evaporation of acetone.

rqh1+, a fission yeast gene related to the Bloom's and Werner's syndrome genes, is required for reversible S phase arrest.

In eukaryotic cells, S phase can be reversibly arrested by drugs that inhibit DNA synthesis or DNA damage. Here we show that recovery from such treatments is under genetic control and is defective in fission yeast rqh1 mutants. rqh1+, previously known as hus2+, encodes a putative DNA helicase related to the Escherichia coli RecQ helicase, with particular homology to the gene products of the human BLM and WRN genes and the Saccharomyces cerevisiae SGS1 gene.

Molecular analysis of hus1+, a fission yeast gene required for S-M and DNA damage checkpoints.

The structure of hus1+, a Schizosaccharomyces pombe gene required for S-M and DNA damage checkpoints, has been determined. Expression of hus1+ requires splicing of five exons, including a microexon that is only 13 nucleotides long. hus1+ is predicted to encode a 33 kDa protein with no similarity to sequences in any database, including the entire S.

The Schizosaccharomyces pombe hus5 gene encodes a ubiquitin conjugating enzyme required for normal mitosis.

Normal eukaryotic cells do not enter mitosis unless DNA is fully replicated and repaired. Controls called 'checkpoints', mediate cell cycle arrest in response to unreplicated or damaged DNA. Two independent Schizosaccharomyces pombe mutant screens, both of which aimed to isolate new elements involved in checkpoint controls, have identified alleles of the hus5+ gene that are abnormally sensitive to both inhibitors of DNA synthesis and to ionizing radiation.

14-3-3 protein homologs required for the DNA damage checkpoint in fission yeast.

During the cell cycle, DNA is replicated and segregated equally into two daughter cells. The DNA damage checkpoint ensures that DNA damage is repaired before mitosis is attempted. Genetic studies of the fission yeast Schizosaccharomyces pombe have identified two genes, rad24 and rad25, that are required for this checkpoint.

Identification and characterization of new elements involved in checkpoint and feedback controls in fission yeast.

To investigate the mechanisms that ensure the dependency relationships between cell cycle events and to investigate the checkpoints that prevent progression through the cell cycle after DNA damage, we have isolated mutants defective in the checkpoint and feedback control pathways. We report the isolation and characterization of 11 new loci that define distinct classes of mutants defective in one or more of the checkpoint and feedback control pathways. Two mutants, rad26.

DNA repair mutants defining G2 checkpoint pathways in Schizosaccharomyces pombe.

We have tested mutants corresponding to 20 DNA repair genes of the fission yeast Schizosaccharomyces pombe for their ability to arrest in G2 after DNA damage. Of the mutants tested, four are profoundly defective in this damage dependent G2 arrest. In addition, these four mutants are highly sensitive to a transient inhibition of DNA synthesis by hydroxyurea.

Variation in herpes simplex virus type 1 glycoproteins produced in kidney cells from different species.

Viral glycoproteins from herpes simplex virus, type 1 (HSV-1) infected NBL-1, Vero, and BHK-21 cells were labelled with 14C-glucosamine and studied by SDS-PAGE and Con-A chromatography. SDS-PAGE analysis demonstrated differences in the number and molecular weight of glycoproteins from these cells. Con-A chromatography resulted in similar binding of glycoproteins from NBL-1 and Vero cells of 10.