Bleomycin, an antibiotic that removes thymine from double-stranded DNA

Oxathiazinane derivatives display both antineoplastic and antibacterial activity: a structure activity study

PURPOSE

The Oxathiazinane substance class is characterized by a high diversity of chemical structures yet to be fully investigated. Our research group recently proved that the 1.4.5-oxathiazine-4.4-dioxide, known as substance GP-2250, possesses antineoplastic properties as shown on pancreatic carcinoma. This current study aims to gain insights into the structure and activity relationship of a series of different Oxathiazinanes regarding their antineoplastic activity and the potential correlation with antibacterial activity. We investigated the newly synthesized Oxathiazinane derivatives: 2255, 2256, 2287, 2289, 2293 and 2296 in comparison to GP-2250.

METHODS

The antineoplastic effect was evaluated in different cancer entities (breast, skin, pancreas and colon cancer cell lines) by viability, proliferation, and cell migration assays in vitro. Disc diffusion tests were performed on various bacteria strains to examine the antibacterial potential. Additionally, reactive oxygen species (ROS) assays were conducted to investigate mechanistic aspects.

RESULTS

The substances GP-2250, 2293, 2289 and 2296 not only showed antineoplastic activity in four different cancer entities but also antibacterial effects, as tested on multiple bacteria strains including MRSA (Methicillin-resistant Staphylococcus aureus). Furthermore, these substances also induced high ROS levels up to 110% in the treated cancer cell lines compared to untreated control cells. These results indicate a correlation between an antineoplastic capacity and antibacterial properties of these derivatives. Both activities appear to be ROS driven. The Oxathiazinane derivatives 2255, 2256 and 2287 lacked both, antineoplastic and antibacterial activity.

CONCLUSION

Thus, a comparable structure activity relationship became apparent for both the antineoplastic and antibacterial activity.

Polyphosphate Reverses the Toxicity of the Quasi-Enzyme Bleomycin on Alveolar Endothelial Lung Cells In Vitro

The anti-cancer antitumor antibiotic bleomycin(s) (BLM) induces athyminic sites in DNA after its activation, a process that results in strand splitting. Here, using A549 human lung cells or BEAS-2B cells lunc cells, we show that the cell toxicity of BLM can be suppressed by addition of inorganic polyphosphate (polyP), a physiological polymer that accumulates and is released from platelets. BLM at a concentration of 20 µg ml^-1 causes a decrease in cell viability (by ~70%), accompanied by an increased DNA damage and chromatin expansion (by amazingly 6-fold). Importantly, the BLM-caused effects on cell growth and DNA integrity are substantially suppressed by polyP. In parallel, the enlargement of the nuclei/chromatin in BLM-treated cells (diameter, 20-25 µm) is normalized to ~12 µm after co-incubation of the cells with BLM and polyP. A sequential application of the drugs (BLM for 3 days, followed by an exposure to polyP) does not cause this normalization. During co-incubation of BLM with polyP the gene for the BLM hydrolase is upregulated. It is concluded that by upregulating this enzyme polyP prevents the toxic side effects of BLM. These data might also contribute to an application of BLM in COVID-19 patients, since polyP inhibits binding of SARS-CoV-2 to cellular ACE2.

The plant WEE1 kinase is involved in checkpoint control activation in nematode-induced galls

Galls induced by plant-parasitic nematodes involve a hyperactivation of the plant mitotic and endocycle machinery for their profit. Dedifferentiation of host root cells includes drastic cellular and molecular readjustments. In such a background, potential DNA damage in the genome of gall cells is evident. We investigated whether DNA damage checkpoint activation followed by DNA repair occurred, or was eventually circumvented, in nematode-induced galls. Galls display transcriptional activation of the DNA damage checkpoint kinase WEE1, correlated with its protein localization in the nuclei. The promoter of the stress marker gene SMR7 was evaluated under the WEE1-knockout background. Drugs inducing DNA damage and a marker for DNA repair, PARP1, were used to understand the mechanisms for coping with DNA damage in galls. Our functional study revealed that gall cells lacking WEE1 conceivably entered mitosis prematurely, disturbing the cell cycle despite the loss of genome integrity. The disrupted nuclei phenotype in giant cells hinted at the accumulation of mitotic defects. In addition, WEE1-knockout in Arabidopsis and downregulation in tomato repressed infection and reproduction of root-knot nematodes. Together with data on DNA-damaging drugs, we suggest a conserved function for WEE1 in controlling G1/S cell cycle arrest in response to a replication defect in galls.

Adaptation of the neutral bacterial comet assay to assess antimicrobial-mediated DNA double-strand breaks in Escherichia coli

This study aimed to determine the mechanism of action of a natural antibacterial clay mineral mixture, designated as CB, by investigating the induction of DNA double-strand breaks (DSBs) in Escherichia coli. To quantify DNA damage upon exposure to soluble antimicrobial compounds, we modified a bacterial neutral comet assay, which associates the general length of an electrophoresed chromosome, or comet, with the degree of DSB-associated DNA damage. To appropriately account for antimicrobial-mediated strand fragmentation, suitable control reactions consisting of exposures to water, ethanol, kanamycin, and bleomycin were developed and optimized for the assay. Bacterial exposure to the CB clay resulted in significantly longer comet lengths, compared to water and kanamycin exposures, suggesting that the induction of DNA DSBs contributes to the killing activity of this antibacterial clay mineral mixture. The comet assay protocol described herein provides a general technique for evaluating soluble antimicrobial-derived DNA damage and for comparing DNA fragmentation between experimental and control assays.

Redox imbalance and pulmonary function in bleomycin-induced fibrosis in C57BL/6, DBA/2, and BALB/c mice

The development of bleomycin-induced pulmonary fibrosis (BLEO-PF) has been associated with differences in genetic background and oxidative stress status. The authors' aim was to investigate the crosstalk between the redox profile, lung histology, and respiratory function in BLEO-PF in C57BL/6, DBA/2, and BALB/c mice. BLEO-PF was induced with a single intratracheal dose of bleomycin (0.1 U/mouse). Twenty-one days after bleomycin administration, the mortality rate was over 50% in C57BL/6 and 20% in DBA/2 mice, and BLEO-PF was not observed in BALB/c. There was an increase in lung static elastance (p < .001), viscoelastic/inhomogeneous pressure (p < .05), total pressure drop after flow interruption (p < .01), and ΔE (p < .05) in C57BL/6 mice. The septa volume increased in C57BL/6 (p < .05) and DBA/2 (p < .001). The levels of IFN-γ were reduced in C57BL/6 mice (p < .01). OH-proline levels were increased in C57BL/6 and DBA/2 mice (p < .05). SOD activity and expression were reduced in C57BL/6 and DBA/2 mice (p < .001 and p < .001, respectively), whereas catalase was reduced in all strains 21 days following bleomycin administration compared with the saline groups (C57BL/6: p < .05; DBA/2: p < .01; BALB/c: p < .01). GPx activity and GPx1/2 expression decreased in C57BL/6 (p < .001). The authors conclude that BLEO-PF resistance may also be related to the activity and expression of SOD in BALB/c mice.

Clustered DNA lesion repair in eukaryotes: relevance to mutagenesis and cell survival

A clustered DNA lesion, also known as a multiply damaged site, is defined as ≥ 2 damages in the DNA within 1-2 helical turns. Only ionizing radiation and certain chemicals introduce DNA damage in the genome in this non-random way. What is now clear is that the lethality of a damaging agent is not just related to the types of DNA lesions introduced, but also to how the damage is distributed in the DNA. Clustered DNA lesions were first hypothesized to exist in the 1990s, and work has progressed where these complex lesions have been characterized and measured in irradiated as well as in non-irradiated cells. A clustered lesion can consist of single as well as double strand breaks, base damage and abasic sites, and the damages can be situated on the same strand or opposing strands. They include tandem lesions, double strand break (DSB) clusters and non-DSB clusters, and base excision repair as well as the DSB repair pathways can be required to remove these complex lesions. Due to the plethora of oxidative damage induced by ionizing radiation, and the repair proteins involved in their removal from the DNA, it has been necessary to study how repair systems handle these lesions using synthetic DNA damage. This review focuses on the repair process and mutagenic consequences of clustered lesions in yeast and mammalian cells. By examining the studies on synthetic clustered lesions, and the effects of low vs high LET radiation on mammalian cells or tissues, it is possible to extrapolate the potential biological relevance of these clustered lesions to the killing of tumor cells by radiotherapy and chemotherapy, and to the risk of cancer in non-tumor cells, and this will be discussed.

Bleomycin-mediated pulmonary toxicity: evidence for a p53-mediated response

Bleomycin damages DNA and causes lung injury and fibrosis. To determine whether bleomycin is associated with the appearance of DNA damage-inducible proteins, C3H mice received either 0.4 mg bleomycin or normal saline intratracheally and were killed 1 to 14 d later. The lungs were examined for expression of p53, p21(WAF1/PiCl), and proliferating cell nuclear antigen (PCNA) using immunohistochemistry and Western blotting. p53-positive cells first appeared at 5 d after treatment and peaked at 7 d; PCNA-positive cells appeared at 1 d after treatment and peaked at 7 d; and p21-positive cells appeared at 5 d and peaked at 9 d. Western blot analysis confirmed that bleomycin upregulated the DNA damage-inducible proteins in a similar fashion. This is the first evidence that bleomycin causes a p53-dependent response associated with acute injury in the lung.

Induction of mosaic sex-linked recessive lethals in the different germ cell stages of Drosophila melanogaster by bleomycin

The mutagenicity of bleomycin was studied in the different stages of spermatogenesis in Drosophila melanogaster. Following the injection of 2 microliters of 0.1 micrograms/ml of the chemical into young wild-type males, complete and mosaic sex-linked recessive lethals were scored by the Muller-5 method in five successive broods, mainly representing the different stages of spermatogenesis. The delayed mutagenic effect of the chemical was measured by the proportion of mosaic progeny produced. The results showed that bleomycin significantly increased the proportions of both complete and mosaic lethals in the broods representing the meiotic and pre-meiotic stages, but did not show any significant increase in these proportions in the broods representing the sperms and spermatids. The sizes of the mutated areas in the F1 gonads represented by the proportions of lethal-bearing females in F2 mosaic cultures were small, indicating that the genetic instabilities induced by bleomycin were transformed into actual mutations in later zygotic divisions. The significant divisions. The significant production of mosaic progeny in the F4 generation of the treated males showed that the mosaic F1 females produced by bleomycin were able to produce further mosaic progeny and suggested that bleomycin-induced instabilities can be transmitted as such for many future generations.

Induction and distribution of damage in CHO-K1 and the X-ray-sensitive hamster cell line xrs5, measured by the cytochalasin-B-cytokinesis block micronucleus assay

The micronucleus assay holds promise as a method for determining clastogenic effects of particular agents and for examining relative sensitivities of eukaryotic cells to such clastogens. In the following work, a detailed examination of the induction of micronuclei in radio-resistant Chinese hamster ovary fibroblasts (CHO-K1) and the DNA double-strand break repair-defective daughter cell line, xrs5, was performed. Cells were exposed to gamma-irradiation, bleomycin, etoposide, camptothecin and the restriction endonuclease PvuII. By a simplified statistical analysis of data, information on the expression of chromosomal damage, the distribution of damage and the role of cell cycle effects on damage expression was obtained from a relatively small number of cells. All 5 clastogens resulted in elevated levels of micronuclei in xrs5 compared to CHO-K1. An analysis of the distribution of micronuclei within treated populations revealed differences between the modes of damage. Significant deviation from the expected values indicated that expression of micronuclei does not follow an expected Poisson distribution. The frequencies of binucleated cells indicated micronucleus frequencies do not always correlate with inhibition of cell cycle progression. This work also demonstrates that caution is required in the interpretation of data obtained through micronucleus assays. In particular, it does not appear possible to proscribe simple numerical values of relative sensitivity or clastogenicity based on the relative number of micronuclei induced alone.

In vitro detection of endonuclease IV-specific DNA damage formed by bleomycin in vivo

Endonuclease IV of Escherichia coli has been implicated by genetic studies in the repair of DNA damage caused by the antitumor drug bleomycin, but the lesion(s) recognized by this enzyme in vivo have not been identified. We used the sensitive primer activation assay, which monitors the formation of 3'-OH groups that support in vitro synthesis by E.coli DNA polymerase I, to determine whether endonuclease IV-specific damage could be detected in the chromosomal DNA of cells lacking the enzyme after in vivo treatment with bleomycin. Chromosomal DNA isolated after a 1 h bleomycin treatment from wild-type, endonuclease IV-deficient (nfo-) and endonuclease IV-overproducing (p-nfo; approximately 10-fold) strains all supported modest polymerase activity. However, in vitro treatment with purified endonuclease IV activated subsequent DNA synthesis with samples from the nfo- strain (an average of 2.6-fold), to a lesser extent for samples from wild-type cells (2.1-fold), and still less for the p-nfo samples (1.5-fold). This pattern is consistent with the presence of unrepaired damage that correlates inversely with the in vivo activity of endonuclease IV. Incubation of the DNA from bleomycin-treated nfo- cells with polymerase and dideoxynucleoside triphosphates lowered the endonuclease IV-independent priming activity, but did not affect the amount of activation seen after endonuclease IV treatment. Primer activation with DNA from the nfo- strain could also be obtained with purified E.coli exonuclease III in vitro, but a quantitative comparison demonstrated that endonuclease IV was > or = 5-fold more active in this assay. Thus, endonuclease IV-specific damage can be detected after in vivo exposure to bleomycin. These may be 2-deoxy-pentos-4-ulose residues, but other possibilities are discussed.

Chromosome damage induced by nanomolar concentrations of bleomycin in porated mammalian cells

We have examined chromosome damage caused by a wide range of bleomycin (BLM) concentrations in Chinese hamster ovary (CHO-K1) cells reversibly porated by the bacterial cytotoxin streptolysin-O (SLO). Chromosome damage was measured using the micronucleus cytokinesis block technique (employing cytochalasin-B). Treatment of exponentially growing cells with 0.045 IU/mL SLO for 5 min resulted in up to a thousand-fold and a million-fold increase in biological effectiveness, compared to treatment in the absence of SLO for 24 hr and 5 min, respectively. Increases in micronuclei of 4-5 times background level were observed after only 5 min exposure to the drug in the presence of SLO at doses as low as 100 pg/mL (approximately 70 pmol/L). These results indicate that the use of SLO may facilitate the treatment of cells with BLM for periods of time resembling acute exposure to ionizing radiations.

Direct cleavage of a DNA fragment by a bleomycin-oligonucleotide derivative

Bleomycin A5 oligonucleotide derivative was used for direct cleavage of a DNA target. In the presence of Fe2+ ions and 2-mercaptoethanol, Blm-R-pd(CCAAACA) (I) damaged the target. pd(TGTTTGGCGAAGGA), with the yield of 80% , without affecting its own oligonucleotide tail. The sites of cleavage were T3-T5 and G6-G7. Unbound bleomycin A5 damaged the G6-G7-C8 site. Reagent I formed more stable complementary complexes with the target than parent oligonucleotide (ATm = 11 C).

Repeated measurement of spontaneous and clastogen-induced sister-chromatid exchange

Sister-chromatid exchanges (SCE), both spontaneous and chemically-induced [bleomycin (BLM), mitomycin-C (MMC), streptonigrin (SN), and 4-nitroquinoline-1-oxide (4NQO)], were studied in the lymphocytes of 24 normal individuals on 2 or 3 different occasions, separated by periods of up to 2 years. For all BLM-induced SCEs, the variation in SCE frequency among the samples from a single individual was significantly greater than the variation between replicate cultures on a given day. These results raise questions concerning the validity of conclusions based on a single observation of chemically-induced SCEs.

Bleomycin-treated DNA is specifically cleaved only by endonuclease IV in E. coli

We have isolated an endonuclease from E. coli active on bleomycin-treated DNA. Purification on DEAE-cellulose separated this activity in strains lacking endonuclease I, endonuclease III or exonuclease III. After DEAE chromatography, the enzyme was active in the absence of divalent cations and was not inhibited by tRNA or harmane. In addition, this enzyme was stable at 45 degrees C for 20 min. These properties are consistent with this activity being endonuclease IV. This was supported by our finding no activity in a strain lacking endonuclease IV.

Cytogenetical characterization of Chinese hamster ovary X-ray-sensitive mutant cells xrs 5 and xrs 6. III. Induction of cell killing, chromosomal aberrations and sister-chromatid exchanges by bleomycin, mono- and bi-functional alkylating agents

Two X-ray-sensitive mutants of CHO-K1 cells, xrs 5 and xrs 6, were characterised with regard to their responses to genotoxic chemicals, namely bleomycin, MMS, EMS, MMC and DEB for induction of cell killing, chromosomal aberrations and SCEs at different stages of the cell cycle. In addition, induction of mutations at the HPRT and Na+/K+ ATPase (Oua) loci was evaluated after treatment with X-rays and MMS. Xrs 5 and xrs 6 cells were more sensitive than wild-type CHO-K1 to the cell killing effect of bleomycin (3 and 13 times respectively) and for induction of chromosomal aberrations (3 and 4.5 times). In these mutants a higher sensitivity for induction of chromosomal aberrations to MMS, EMS, MMC and DEB was observed (1.5-3.5 times). The mutants also showed increased sensitivity for cell killing effects of mono- and bi-functional alkylating agents (1.7-2.5 times). The high cell killing effect of X-rays in these mutants was accompanied by a slight increase in the frequency of HPRT mutation. The xrs mutants were also more sensitive to MMS for the increased frequency of TGr and Ouar mutants when compared to wild-type CHO-K1 cells. Though bleomycin is known to be a poor inducer of SCEs, an increase in the frequency of SCEs in xrs 6 cells (doubling at 1.2 micrograms/ml) was found in comparison to no significant increase in xrs 5 or CHO-K1 cells. The induced frequency of SCEs in all cell types increased in a similar way after the treatment with mono- or bi-functional alkylating agents. MMS treatment of G2-phase cells yielded a higher frequency of chromatid breaks in the mutants in a dose-dependent manner compared to no effect in wild-type CHO-K1 cells. Treatment of synchronised mutant cells at G1 stage with bleomycin resulted in both chromosome- and chromatid-type aberrations (similar to the response to X-ray treatment) in contrast to the induction of only chromosome-type aberrations in wild-type CHO-K1 cells. The frequency of chromosomal aberrations chromosome and chromatid types) also increased with MMC treatment in G1 cells of xrs mutants. DEB treatment of G1 cells induced mainly chromatid-type aberrations in all cell types. The possible reasons for the increased sensitivity of xrs mutants to the chemical mutagens studied are discussed and the results are compared to cells derived from radiosensitive ataxia telangiectasia patients.

Heat shock phenomena in Aspergillus nidulans. II. Combined effect of heat and bleomycin to heat shock protein synthesis, survival rate and induction of mutations

The combined action of hyperthermia and Bleomycin on Aspergillus nidulans was studied at three different levels: mycelial protein synthesis, spore viability and induction of mutations. It was found that Bleomycin treatment of preincubated mycelia during the heat shock enhances the incorporation of 35S-methionine into heat shock bands. Furthermore, simultaneous treatment with hyperthermia (43 degrees C) and Bleomycin results in greater cytotoxic activity in spores and in a higher induction rate of point mutations.

Rejoining of double strand breaks in normal human and ataxia-telangiectasia fibroblasts after exposure to 60Co gamma-rays, 241Am alpha-particles or bleomycin

The rejoining of DNA double strand breaks (dsb) induced by 60Co gamma-rays, 241Am alpha-particles or bleomycin was measured by neutral filter elution. In agreement with their colony-forming ability, ataxia-telangiectasia cells (AT2BE) and normal fibroblasts exhibited similar dsb rejoining capacity following alpha-irradiation, but showed marked differences in the rejoining kinetics of dsb induced by gamma-rays or bleomycin.

Potentiation of the bleomycin, arabinofuranosylcytosine and adriamycin-caused inhibition of DNA synthesis in lymphocytes by bestatin in vitro

Combinations of 1-beta-D-arabinofuranosylcytosine (araC), bleomycin (BLM) or adriamycin (ADM) with the dipeptide bestatin do not result in an enhanced in vitro cytotoxicity in the macrophage-free L5178y mouse lymphoma cell system. However, in macrophage-containing murine spleen lymphocytes bestatin causes a potentiating effect of the cytostatic drugs araC, BLM and ADM with respect to their potencies to inhibit DNA synthesis. In the presence of 1 microgram bestatin/ml, the ED50 concentrations causing a 50% reduction of [3H]dThd incorporation were significantly lowered; 4.3-fold in the studies with araC and BLM, and 1.8-fold in the experiments with ADM. Bestatin, given alone, displays a stimulating effect on [3H]dThd incorporation into macrophage-containing lymphocyte cultures within the concentration range 0.1-10 micrograms/ml. In contrast to the bestatin-stimulated lymphocytes, ConA-stimulated as well as LPS-stimulated lymphocytes do not show a higher sensitivity to the selected drugs inhibiting DNA synthesis. These data should encourage the practical use of bestatin in combination with araC, BLM or ADM in cancer treatment.

Hypersensitivity and reduced inhibition of DNA synthesis in ataxia telangiectasia lymphoblasts treated with low levels of neocarzinostatin

The effects of neocarzinostatin (NCS) on lymphoblastoid cell lines (LCLs) established from ataxia telangiectasia (A-T) were determined. A-T lymphoblasts were found to be hypersensitive to low levels of NCS as measured by cell growth and cell survival. On the other hand, A-T lymphoblasts failed to postpone DNA synthesis to the same degree as normal lymphoblasts following treatment with NCS. LCLs established from Nijmegen breakage syndrome (NBS) could be distinguished from ataxia and normal cell lines by their intermediate level of survival following exposure to NCS.

Quantitative measurement of single- and double-strand breakage of DNA in Escherichia coli by the antitumor antibiotics bleomycin and talisomycin

We developed an assay in which single-strand breakage (ssb) and double-strand breakage (dsb) of intracellular DNA by chemical agents can be accurately quantitated and differentiated. Escherichia coli cells containing plasmid pBR322 DNA were incubated with the antitumor antibiotics bleomycin A2 (BLM A2) or talisomycin A (TLM A). The plasmid DNA was isolated and then analyzed by electrophoresis on 1% agarose gels to separate the following conformational forms of plasmid DNA: (i) native, covalently closed, super helical, form I; (ii) nicked, relaxed circular, form II; and (iii) double-strand broken, linear, form III. Quantitation by densitometric analysis of the gels showed that BLM A2 and TLM A were equally active in terms of the concentrations of drug necessary to reduce equivalent amounts of form I DNA in the cells, whereas in vitro (using isolated pBR322 DNA as a drug substrate) twofold more TLM A than BLM A2 was required to produce an equivalent amount of reduction in form I DNA. TLM A produced more intracellular dsb than did BLM A2. The intracellular dsb activities (dsb/ssb ratio) measured from BLM A2 and TLM A were equivalent to those measured for the respective agents when isolated pBR322 DNA was used as the substrate. In E. coli both ssb and dsb were repaired, but TLM A damage was repaired more slowly and to a lesser extent, which may reflect the relative frequency of dsb.

Nick translation--a new assay for monitoring DNA damage and repair in cultured human fibroblasts

An in vitro assay has been developed to detect DNA damage and repair following chemical treatment of human diploid fibroblasts. DNA damage is measured by following the Escherichia coli DNA polymerase I-catalyzed incorporation of radiolabeled deoxycytidine triphosphate (dCTP) into the DNA of lysolecithin-permeabilized cells. DNA strand breaks with free 3' OH termini serve as template sites for incorporation, and decrease of this incorporation with time, following removal of the test chemical, indicates loss (repair) of initial damage. Inhibition of the DNA excision repair process by the addition of the repair inhibitors arabinofuranosyl cytosine (ara-C) and hydroxyurea (HU) during the incubation period gives rise to an increased number of template sites, manifesting itself in increased incorporation and indicating the induction of long-patch excision repair. This nick translation assay, originally proposed by Nose and Okamoto [1983], is very sensitive, allows detection and quantitation of both DNA damage and repair, distinguishes between various types of induced damage, does not require radioactive prelabeling of cells, and circumvents some of the problems inherent in unscheduled DNA synthesis (UDS) assays. The assay is also useful in detecting those agents that inhibit replicative DNA synthesis and/or the excision repair process. Results presented demonstrate that all 14 direct-acting carcinogens tested and 8 of 14 carcinogens requiring metabolic activation give positive indication of DNA damage, repair, or both. Eleven of 14 noncarcinogens tested were scored as negative, the other 3 having previously been shown to interact with cellular DNA. This assay is shown to have predictive capability at least equal to that of UDS assays but to allow a broader spectrum of genotoxic effects to be analyzed.

Chemical clastogenicity in lymphoid cell lines of chromosomal instability syndromes

Long-term lymphoid cell lines (LCL) derived from normal individuals, patients with ataxia telangiectasia (A-T), xeroderma pigmentosum (XP), and Fanconi anemia (FA) were exposed to various concentrations of 11 chemical clastogens. The agents were chosen to represent a variety of suggested modes of action. In contrast to all other genotypes, the FA lines demonstrated significant rates of spontaneous chromosomal breakage and showed hypersensitivity to all of the clastogens employed. Variability among lines within a genotype suggested individual responses to specific agents. Computation of "corrected values" to address the problem of baseline disparity removed some of the significant differences between the FA and other lines. Nonetheless, following correction, the FA genotype was still delineated by clastogens which are not DNA cross-linkers. The A-T lines were specifically identified by the induction of chromosome damage by bleomycin and neocarzinostatin.

Biosynthetic mechanism of ribulose-1,5-bisphosphate carboxylase in the purple photosynthetic bacterium, Chromatium vinosum. III. Absence of extrachromosomal DNA

Inducible formation of ribulose-1,5-bisphosphate (RuBP) carboxylase in the cells of Chromatium vinosum under autotrophic conditions was not affected by six different inhibitors of DNA synthesis. Photosynthetic CO2 fixation and RuBP carboxylase activities were not influenced by seven reagents known to eliminate plasmids. Plasmids were not detectable by agarose gel electrophoresis employing either the cleared lysate or alkaline sodium dodecyl sulfate method, nor were they detected by ethidium bromide-CsCl density gradient centrifugation. Overall experimental results tend to indicate that plasmids are absent in the Chromatium cells and that the induction of RuBP carboxylase is presumably not regulated in the DNA replication process.

Potentiation of the cytostatic effect of bleomycin on L5178y mouse lymphoma cells by pepleomycin

Bleomycin (BLM) and pepleomycin (PEP) are two chemically related glycopeptide antitumor antibiotics which differ in their terminal residues only. Studying the growth-inhibitory potencies of BLM (clinical mixture), BLM-A2, BLM-B2 and PEP in the L5178y mouse lymphoma cell culture system, it was elucidated that the slopes of the dose-response curves at the ED50 concentration (around 1 microgram/ml) were steeper for PEP than for BLM. This result together with cytotoxicity determinations revealed a cytostatic action of PEP within a closer concentration range than BLM. Both drugs inhibit cell proliferation during S- and G2-phase. Given in combination, BLM and PEP inhibit cell proliferation in a highly significant synergistic way (FIC indexes: 0.25-0.46). This in vitro result, which might be of therapeutic importance, is correlated with differences on the molecular level. Determinations of the ratio between the number of single- and double-strand breaks in the DNA (the target molecule of the drugs) revealed a considerably lower value for DNA from BLM-treated cells (1.9:1) than for DNA from PEP-treated cells (13:1).

DNA replication and repair in ataxia telangiectasia cells exposed to bleomycin

A marked increase in sensitivity to bleomycin was observed in two ataxia telangiectasia (AT) lymphoblastoid cell lines compared to that in cell lines from two normal individuals. This sensitivity was obtained at two different concentrations of bleomycin. While normal cells showed a rapid recovery of ability to divide, there was no indication of such a recovery in AT cells up to 120 h after bleomycin treatment. A similar level of breakage of DNA occurred in both cell types after incubation with bleomycin. The rate of repair of these breaks was also the same. DNA synthesis was found to be more resistant to bleomycin in AT cells than in control cells. The latter data are in keeping with results previously obtained using ionizing radiation.

Increased clastogenicity and decreased inhibition of DNA synthesis by neocarzinostatin and tallysomycin in ataxia telangiectasia lymphoid cells

Cytogenetic damage in cells cultured from normal individuals and patients with ataxia telangiectasia (A-T) and xeroderma pigmentosum (XP) was induced by the chemotherapeutic antibiotics neocarzinostatin (NCS), tallysomycin (TLM) and bleomycin (BLM). Chromosomal breakage was specifically elevated in A-T cells when compared to the other genotypes tested. Similar results were not observed with the clastogens mitomycin C (MMC) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) as all cells responded similarly. All 5 chemical agents caused a marked suppression of de novo DNA synthesis in normal and XP long-term lymphoid cell lines while the A-T cells seemed resistant to this effect of NCS, TLM and BLM.

Isolation of cell cycle-dependent gamma ray-sensitive Chinese hamster ovary cell

A technique for the isolation of gamma ray-sensitive Chinese hamster ovary (CHO) cell mutants is described, which uses nylon cloth replica plating and photography with dark-field illumination to directly monitor colonies for growth after gamma irradiation. Two gamma ray-sensitive mutants were isolated using this method. One of these cells (XR-1) had a two-slope survival curve: an initial steep slope and then a flattening of the curve at about 10% survival. Subsequently, it was found that this cell is sensitive to gamma irradiation in G1, early S, and late G2 phases of the cell cycle, whereas in the resistant phase (late S phase) its survival approaches that of the parental cells. The D37 in the sensitive G1 period is approximately 30 rads, compared with 300 rads of the parental cell. This mutant cell is also sensitive to killing by the DNA breaking agent, bleomycin, but is relatively insensitive to UV light and ethyl methane sulfonate, suggesting that the defect is specific for agents that produce DNA strand breakage.

Bleomycin--mode of action with particular reference to the cell cycle

Over the last four years, investigations into the mechanism of interaction between bleomycin and DNA have been pursued at a rapid pace. This is, no doubt, because of the potential of bleomycin as a tool for molecular biology. It seems likely that the precise nature of the interaction between Fe(II), oxygen and bleomycin will be elucidated in the near future together with the nature of the binding between the complex and DNA. More information on the mechanism of strand scission including the involvement of free radical mechanisms and sequence specificity may also be expected. In contrast to this picture of rapid progress at the molecular level, interest in studies of bleomycin action at the cellular level appears to have waned. This is despite the fact that most of the important questions which have been raised regarding effects of the drug on cell cycle progression, the possibility of a selective action on on-cycling cells and the nature of 'recovery from potentially-lethal damage' remain unresolved. There is no doubt that, for most cell types, bleomycin produces a block at the early G2 stage of the cell cycle. There is considerable doubt, however, as to how many of the cells blocked for a significant period remain clonogenically viable. This question is amenable to being answered using a vital DNA stain, such as Hoechst 33342, and cell sorting but this does not appear to have been done. The relationship between G2 blockage and repair of DNA damage has also not been resolved. Neither has the question of whether or not DNA breaks which remain unrepaired are different in nature from the majority of repairable lesions. The data on the relative sensitivity of exponential and plateau phase cells are conflicting and their in vivo significance unclear. Well designed experiments to examine the bleomycin sensitivity of those cells in solid tumors which survive radiation treatment could help to answer this question. Evidence that the phenomenon of 'recovery from potentially lethal damage' is therapeutically-exploitable is mainly lacking. It would be of great relevance to known whether or not the effect can be observed in normal tissues. However, the evidence that the effect is not simply an artefact of clonogenic assay procedures is scanty and this possibility must be borne in mind.(ABSTRACT TRUNCATED AT 400 WORDS)

cdc9 ligase-defective mutants of Saccharomyces cerevisiae exhibit lowered resistance to lethal effects of bleomycin

Conditional ligase-deficient mutants of Saccharomyces cerevisiae were more sensitive than their parental (CDC9) strain to dose-dependent killing by bleomycin, even when mutant cells were pregrown and exposed to the antibiotic at permissive temperatures. Pretreatment incubation at the restrictive temperature (37 degrees C) under growing or nongrowing conditions enhanced bleomycin killing of both cdc9-1 and cdc9-9 mutants. This sensitization could be relieved by incubation at the permissive temperature before treatment.

Recombinogenic and mutagenic effects of the antitumor antibiotic bleomycin in Aspergillus nidulans

Bleomycin, an antibiotic and antineoplastic drug that inhibits DNA synthesis and causes several types of chromosomal aberration, was found to increase mitotic recombination in Aspergillus nidulans. Heterozygous prototrophic diploid strains grown on media containing bleomycin produced significant increases of yellow and white sectors compared with controls. Further, the increased colour segregants were due to mitotic crossing-over, whereas the non-dis junctional segregants remained at the control level. Bleomycin also induced point mutations in the methionine-suppressor system of the methGl biAl strain of Aspergillus nidulans. Conidia treated in suspension with various concentrations of bleomycin increased the methionine-independent mutants 30-fold and more.

On the mechanism of reductive activation in the mode of action of some anticancer drugs

Bioactivation of a number of DNA-specific antitumor drugs depends on oxidoreduction. Bleomycin, neocarzinostatin and anthracycline glycosides are the best known among such drugs in terms of reductive activation processes. Their reduction results in short-lived radical or electrophilic intermediates attacking DNA stereospecifically. The physico-chemical properties of these drugs and the nature of DNA damage are reviewed. Models for DNA-intercalation, electron-donor systems involved in drug metabolisation, and the role of oxygen in radical reactions, are discussed in the light of recent reports.

Modulation of bleomycin cytotoxicity

Lethal effects of a 75-microgram/ml concentration (approximately 5 X 10-5 M) of bleomycin on stationary-phase haploid or diploid cells of the eucaryote Saccharomyces cerevisiae were negated in the presence of 0.05 M phosphate buffer (pH 7). High cell densities (2 X 10(8) cells per ml) further inhibited killing. Multiphasic survival curves resulting after treatments in deionized water (pH 6.7) suggested the presence of cells with differing susceptibilities either at the start of treatment periods or as a result of resistance which developed during exposure to antibiotic. To identify a delayed effect, prolonged lethal consequences of the action of bleomycin were investigated under liquid-holding conditions. Survival of untreated early-stationary-phase yeast cells was not significantly affected by incubation without antibiotic for 6 or 36 h in non-nutrient buffer or water. However, increased killing resulted after bleomycin-treated cells were incubated in the absence of bleomycin or buffer. Moreover, cells which had never been exposed to the antibiotic lost considerable colony-forming ability as a result of incubation with bleomycin-treated cells, indicating the efflux of bleomycin or a reaction product. The findings have implications for both experimental cell studies and cancer therapy, as well as for the chemical mechanisms by which a metal bleomycin complex could cause killing.

The relationship between DNA and chromosome damage after bleomycin treatment: dose-response measurements

The molecular basis for chromosome aberration formation has been studied using the sensitive techniques of premature chromosome condensation and DNA alkaline elution. The dose response of Chinese hamster ovary cells to bleomycin treatment at the DNA and chromosome levels was compared. Each DNA elution curve showed a 2-component profile, with a more sensitive component apparent at low doses. The chromosome aberration curves also exhibited a 2-component profile when determined in G2-PCC; however, this phenomenon was less apparent when chromosome damage was enumerated in mitotic figures. These results suggest that differential sensitivity to bleomycin exists within the cellular chromatin. The effect of dose rate on aberration formation was examined by administering bleomycin at 2 concentrations that, with different treatment times, yielded equivalent amounts of DNA damage. The chromatid exchange rate was independent of dose rate, suggesting that rapidly repaired DNA lesions are not involved in the formation of exchanges.

The effect of bleomycin on DNA synthesis in ataxia telangiectasia lymphoid cells

Bleomycin, a radiomimetic glycopeptide, inhibits de novo DNA synthesis in ataxia telangiectasia lymphoblastoid B cells to a markedly lesser extent than in normal and xeroderma pigmentosum lymphoid cells. This observation is similar to that following ionizing radiation; however, the effect is slower following the chemical treatment. Recovery of the normal cells occurs 15-18 hours after treatment, whereas the ataxia telangiectasia lines do not attain normal levels of DNA synthesis during the entire 24-hour observation period. Similar differences were not observed following treatment with mitomycin C, a bifunctional alkylating agent, indicating a specific effect of bleomycin on DNA synthesis in ataxia telangiectasia cells. Following bleomycin treatment and preincubation with hydroxyurea, residual DNA synthesis in ataxia telangiectasia cells was similar to that in both normal and xeroderma pigmentosum lymphoid cells, suggesting that the capacity to repair the induced DNA lesion is present.

Synthesis by DNA polymerase I on bleomycin-treated deoxyribonucleic acid: a requirement for exonuclease III

phi X174 RFI DNA treated with bleomycin (BLM) under conditions permitting nicking does not serve as a template-primer for Escherichia coli DNA polymerase I. Purified exonuclease III from E. coli and extracts from wild-type E. coli strains are able to convert the BLM-treated DNA to suitable template-primer, but extracts from exonuclease III deficient strains are not. Brief digestion by exonuclease III is enough to create the template-primer, suggesting that the exonuclease III is converting the BLM-treated DNA by a modification of 3' termini. The exonucleolytic rather than the phosphatase activity of exonuclease III appears to be involved in the conversion. Comparative studies with micrococcal nuclease indicate that BLM-created nicks do not have a simple 3'-P structure. Bacterial alkaline phosphatase does not convert BLM-treated DNA to template-primer. The endonuclease VI activity associated with exonuclease III does not incise DNA treated with BLM under conditions not allowing nicking, in contrast to DNA with apurinic sites made by acid treatment, arguing that conversion does not require the endonuclease VI action on uncleaved sites.

DNA polymerase III-dependent repair synthesis in response to bleomycin in toluene-treated Escherichia coli

Bleomycin (BLM) is an antitumor drug which interacts with and damages DNA. We have reported a repair response dependent on DNA polymerase I in toluene-treated Escherichia coli. We report here that DNA polymerase III can also catalyze a repair response in toluene-treated E. coli following exposure to BLM. Polymerase III-mediated synthesis differs because it is ATP-dependent, whereas polymerase I-mediated repair synthesis is not. Polymerase III repair synthesis is independent of replicative synthesis, as demonstrated in a polA-, dnaBts strain, or use of Novobiocin to inhibit replication, and replication persists in the presence of repair synthesis. It appears that ATP-dependent repair synthesis in response to BLM is also present in polA+ strains. Repair synthesis does not require the uvrA gene product.

Relationship of DNA lesions and their repair to chromosomal aberration production

Though the roles of some specific DNA lesions in the production of chromosomal aberrations is clearly established, those of others remain unclear. While the study of aberration production in human genetic DNA repair deficiency diseases has been extremely rewarding already, eukaryotic repair systems are obviously complex, and one is tempted to feel that such studies may have raised as many questions as they have provided answers. For example, the "standard" sort of xeroderma pigmentosum is chromosomally sensitive to ultraviolet light and to those chemical agents inducing ultraviolet-type DNA repair. But both it and the variant form have been reported to also be sensitive to the crosslinking agent mitomycin C in one study [18], implying a common step or steps in the repair of pyrimidine cyclobutane dimers and DNA crosslinks. However, just to complicate matters, another study of chromosomal aberration production in xeroderma pigmentosum cells had found them no more sensitive to mitomycin C than normal cells [50]. Similarly, Fanconi's anemia cells, which are chromosomally sensitive to crosslinking agents, and appear to be defective in the "unhooking" of linked polynucleotide strands [15, 16, 49, 51], are reported to be chromosomally sensitive to ethyl methanesulfonate as well [29], and to be sensitive to ionizing radiation [7, 19, ]0], again implying overlapping repair systems. It seems certain that further study of chromosomal aberration production in repair deficient cells by agents inducing various DNA lesions will reveal even greater complexity in eukaryotic DNA repair systems and their role in chromosomal aberration production. Nevertheless, there seems hope, at least, that such studies may also ultimately lead to a complete understanding of the molecular mechanisms involved.