Differential expression of protein kinase C epsilon protein in lung cancer cell lines by ionising radiation

The effect of ionising radiation on the regulation of gene and protein expression is complex. This study focuses on the translational regulational of the epsilon isoform of protein kinase C by ionising radiation. We found that protein kinase C epsilon is rapidly increased in the human lung adenocarcinoma cell line A549 following irradiation. Western blots showed increased accumulation of this protein at doses as low as 75 cGy after 15 min post irradiation. Maximal induction (11-fold over unirradiated cells) of PKC epsilon occurred at 150 cGy within 1 h after treatment by X-rays in A549 cells. The increased levels of PKC epsilon protein after X-rays does not require de novo protein or RNA synthesis, suggesting that this increase is post-translationally controlled. In contrast to A549 cells PKC epsilon levels in the large cell lung carcinoma cell line NCI H661 were not induced by radiation. In the small cell lung carcinoma cell line NCI N417, PKC epsilon was also not induced but a higher molecular weight PKC epsilon protein, suggestive of phosphorylation, appeared at 2 h after irradiation. The variation in induction or phosphorylation of PKC epsilon by ionising radiation in the cell lines tested in this study suggested that no clear correlation existed between intrinsic radiation sensitivity and PKC epsilon induction. To determine whether PKC epsilon does play a role in cell survival to irradiation, we used the protein kinase inhibitor staurosporin to decrease PKC activity and found that staurosporin sensitised cells to killing by ionising radiation. Pulsed field gel electrophoresis, however, indicated that DNA double-strand break repair was not decreased, suggesting that PKC epsilon is modifying the fidelity of rejoining and not the overall magnitude of repair. The regulation of PKC by ionising radiation will be discussed with respect to the biological consequences of gene induction by DNA damage agents.

Rhodococcus equi cavitary pneumonia in HIV-infected patients: an unsuspected opportunistic pathogen

Two patients seropositive for human immunodeficiency virus (HIV) and with no previous acquired immunodeficiency syndrome-defining conditions developed cavitary pneumonia and pleural disease caused by Rhodococcus equi. R. equi was isolated from these patients' sputum and lung biopsy specimens, respectively, but the microorganism was initially considered to be a contaminant (patient 1) or misidentified as a nontuberculous mycobacterium (patient 2). The R. equi infection was fatal in one patient, who died after 4 months without specific antimicrobial therapy; the second patient was unresponsive to combination therapy with various antimicrobial agents. R. equi may cause life-threatening infections in HIV-infected patients. Microbiology laboratories should be cognizant of the need to exclude R. equi as a cause of infection in highly immunosuppressed patients.

Central venous catheter sepsis caused by unusual Gordona (Rhodococcus species: identification with a digoxigenin-labeled rDNA probe

We describe central line sepsis caused by Gordona (Rhodococcus) species in two patients, which complicated receipt of long-term total parenteral nutrition at home. Species identification was attempted by conventional biochemical analysis and analysis of polymorphisms in the ribosomal RNA genes with use of a digoxigenin-labeled rDNA probe. Using these techniques, we identified our first patient's isolate as Gordona terrae. The isolate from our second patient was biochemically atypical and could not be reliably matched to any of the recognized Gordona (Rhodococcus) species. To our knowledge, these patients are the first to have been reported with systemic infection caused by Gordona (Rhodococcus) species. The first patient's infection resolved after 6 weeks of intravenous therapy with vancomycin with the catheter left in situ; however, infection in the second patient required catheter removal for cure. These cases show that immunocompetent patients receiving long-term parenteral nutrition may develop central line infections with these unusual species of microorganisms.

Infections due to Nocardia transvalensis: clinical spectrum and antimicrobial therapy

Nocardia transvalensis, a rare Nocardia species, has previously been recognized as a cause of actinomycotic mycetoma. In a retrospective review of N. transvalensis isolates referred to the Centers for Disease Control (Atlanta) during the period January 1981 through January 1990, we identified 15 patient isolates. Four N. transvalensis isolates originated from one Australian reference laboratory; one patient's isolate that was identified by the Australian laboratory but that was not received at the Centers for Disease Control was also included in our study. A review of the cases of these 16 patients found that N. transvalensis caused infection in 10 patients and colonization in two patients. Six (75%) of eight patients with primary pulmonary or disseminated N. transvalensis infections had an underlying immunologic disorder or were receiving immunosuppressive therapy; three patients with disseminated infection died. All nine infected patients for whom specific antimicrobial therapy was prescribed received trimethoprim-sulfamethoxazole. Results of in vitro antimicrobial susceptibility tests of 11 N. transvalensis isolates revealed increased antimicrobial resistance to amikacin and other drugs when compared with that of other Nocardia species. Severely immunocompromised patients are predisposed to N. transvalensis pneumonia or disseminated infection, and the lung may be the portal of entry.

Repair of DNA and chromosome breaks in cells exposed to SR 4233 under hypoxia or to ionizing radiation

3-Amino-1,2,4-benzotriazine-1,4-dioxide (SR 4233) is a bioreductive anticancer drug which has a high selective toxicity to hypoxic cells. We have characterized the DNA and chromosome damage in wild-type Chinese hamster ovary (CHO) cells and mutant XR-1 cells after exposure to SR 4233 under hypoxia and compared it to the damage produced by ionizing radiation (gamma-rays). Using the technique of pulsed field gel electrophoresis, we found that the kinetics of rejoining of DNA double-strand breaks in CHO cells after treatment with SR 4233 was concentration dependent, varying from 95% (less than 50 microM) to 10% (200 microM) by 24 h. This contrasted with the dose-independent kinetics exhibited in cells after gamma-ray exposure. XR-1 cells were deficient in rejoining double-strand breaks produced by either SR 4233 or gamma-rays. XR-1 cells were 2-fold more sensitive than wild-type CHO cells to SR 4233 but were 10-fold more sensitive than CHO to gamma-rays. These results suggested that DNA double-strand breaks are involved in hypoxic cell killing by SR 4233, but the specific type of lesion produced is not identical with that causing cell killing by gamma-rays. To further investigate this, we measured chromosome breaks in CHO cells by premature chromosome condensation after equitoxic doses of SR 4233 under hypoxia and gamma-rays. SR 4233 produced lower initial but similar final (after 6 h of repair) numbers of chromosome breaks compared to gamma-rays at equitoxic doses. These results suggest that, at low doses, chromosome breaks can entirely account for hypoxic cell killing by SR 4233 and that chromosome breaks produced by SR 4233 are more damaging and/or more difficult to repair than those produced by gamma-rays.

The spectrum of β thalassaemia in Burma

The molecular defects causing beta thalassaemia have been analysed in 85 unrelated Burmese patients. The patients included 14 with homozygous beta thalassaemia, 70 with HbE/beta thalassaemia and one with HbS/beta thalassaemia. Using a combination of allele-specific oligoprobe hybridization and direct sequencing of genomic DNA amplified by the polymerase chain reaction, 95/99 of the beta-thalassaemia alleles have been characterized. Six mutations have been identified of which three, the G-T at IVS-1 position 1, the G-C at IVS-1 position 5 and the deletion of TCTT in codons 41/42, accounted for 85% of the alleles. Despite the diversity of ethnic groups in Burma, the number of beta-thalassaemia alleles in Burma is relatively small. Thus, diagnosis of the majority of the beta thalassaemias would be possible using a limited number of oligonucleotide probes.

The use of asymmetric-field inversion gel electrophoresis to predict tumor cell radiosensitivity

The success of a predictive assay for radiotherapy relies on the use of one or more tumor cell traits that equate with tumor radioresistance or radiosensitivity. These traits can be divided into intrinsic (genetic) and extrinsic (epi-genetic) factors. Most probably, a tumor's response to radiotherapy will be influenced by both of these sets of traits. Radiobiological analysis of cultured cells derived from explanted tumors of head and neck patients has shown that in vitro survival of tumor cells is not the only factor affecting tumor radiocurability. Two possible reasons are the high degree of selection involved in growing the cells in vitro and the inability to assess the contribution of the cell-cell contact effect with cultured cells. A possible means of overcoming both of these problems would be an assessment of the radiosensitivity of the cell population immediately after removal from the tumor. Since a good correlation exists between intrinsic cellular radioresistance and DNA double-strand break repair (DSBR) as assayed by the Neutral Elution technique [21], we have investigated the feasibility of using asymmetric field inversion gel electrophoresis (AFIGE) in identifying resistant tumor cells in vitro. AFIGE has several advantages over neutral elution in that it is faster (approximately 60-80 samples can be run on the same agarose gel) and, most importantly, one can visualize DNA damage and repair by staining the DNA with ethidium bromide.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification and epidemiological typing of clinical and environmental isolates of the genus Rhodococcus with use of a digoxigenin-labeled rDNA gene probe

Rhodococcus species are ubiquitous in the environment, and several species have been reported to have pathogenic potential for humans. Rhodococcus equi, in particular, has been reported to cause infections in patients with AIDS. However, the identification of Rhodococcus species with use of conventional biochemical tests is problematic, and no simple and reproducible method exists for their rapid identification and differentiation. We found that the type strains of the 20 recognized species in the genus Rhodococcus could be clearly distinguished with use of a combination of the Pvu II and Pst I rRNA gene restriction endonuclease patterns and a digoxigenin-labeled Escherichia coli rDNA probe. Analysis of four clinical or environmental isolates confirmed as Rhodococcus bronchialis showed no interstrain variation of rRNA gene bands. Analysis of 15 isolates confirmed as R. equi from 13 patients showed 11 different rRNA gene patterns. No discernible difference was observed in the ribotype patterns between R. equi isolates from patients for whom AIDS had been diagnosed and those from patients who did not have AIDS, and there was no evidence of geographic clustering of R. equi ribotype patterns. Three of five Rhodococcus species isolates that could not be differentiated with use of conventional biochemical methods were identified with use of ribotype analysis. Therefore, ribotype analysis may provide an important adjunct to current biochemical identification of environmental and clinical isolates of Rhodococcus species.

Hox-4 gene expression in mouse/chicken heterospecific grafts of signalling regions to limb buds reveals similarities in patterning mechanisms

The products of Hox-4 genes appear to encode position in developing vertebrate limbs. In chick embryos, a number of different signalling regions when grafted to wing buds lead to duplicated digit patterns. We grafted tissue from the equivalent regions in mouse embryos to chick wing buds and assayed expression of Hox-4 genes in both the mouse cells in the grafts and in the chick cells in the responding limb bud using species specific probes. Tissue from the mouse limb polarizing region and anterior primitive streak respecify anterior chick limb bud cells to give posterior structures and lead to activation of all the genes in the complex. Mouse neural tube and genital tubercle grafts, which give much less extensive changes in pattern, do not activate 5′-located Hox-4 genes. Analysis of expression of Hox-4 genes in mouse cells in the grafted signalling regions reveals no relationship between expression of these genes and strength of their signalling activity. Endogenous signals in the chick limb bud activate Hox-4 genes in grafts of mouse anterior limb cells when placed posteriorly and in grafts of mouse anterior primitive streak tissue. The activation of the same gene network by different signalling regions points to a similarity in patterning mechanisms along the axes of the vertebrate body.

Distribution and antimicrobial susceptibility of Rhodococcus equi from clinical specimens

Rhodococcus equi, an unusual gram positive aerobic actinomycete, was first described as a respiratory pathogen of livestock in 1923. Reports of human clinical illness have emphasized R. equi as a cause of invasive pulmonary infection in severely immunocompromised patients and, recently, have implicated it as a cause of pneumonia, bacteremia and disseminated infection in HIV-infected patients. To determine the distribution of R. equi we evaluated 107 isolates referred to the Centers for Disease Control (CDC) during the period January 1973 through December 1990. The sites of these 107 isolates (101 patient and 6 animal isolates) were: blood (32 isolates), sputum (30), lung tissue (13) and other site (32). Before 1983, when the first R. equi isolate from an HIV-infected patient was received, CDC received a total of 52 patient isolates. In addition, during this 10 year period, R. equi isolates were received from more than one site from only one patient. However, during the two year period 1989-1990, we identified 8 patients with underlying HIV infection and R. equi pneumonia who accounted for 29 of 35 (83%) R. equi patient isolates; 6 of these patients also had bacteremia and three died with disseminated R. equi infection. No isolates were resistant to amoxicillin-clavulanate, ampicillin-sulbactam, gentamicin or imipenem, and few (less than 5%) isolates were resistant to erythromycin, rifampin, tetracycline, and trimethoprim-sulfamethoxazole. These results suggest that HIV-infected patients, in particular, are predisposed to develop invasive pulmonary, fatal disseminated R. equi infection (or both), and appropriate antimicrobial susceptibility testing of clinical isolates may improve the effectiveness of therapy of R. equi-infected patients.

Outbreak of pseudoinfection with Tsukamurella paurometabolum traced to laboratory contamination: efficacy of joint epidemiological and laboratory investigation

From January 1988 to May 1989, one hospital in South Carolina reported 12 isolates of Tsukamurella paurometabolum from 10 patients. There were no common risk factors among the patients. Case-control studies revealed that the positive specimens were significantly more likely to have been processed in the TB/fungal room, to have been tissue samples, and to have been handled by one technician. Typing on the basis of biochemical, antimicrobial resistance, Southern blot, and ribotype profiles showed that the isolates from the outbreak were essentially identical and that they were distinguishable from each of two isolates obtained after the outbreak and from two type strains. These findings support the hypothesis of a common-source outbreak of pseudoinfection. There are reasons to believe that T. paurometabolum is present both in the environment and as a culture contaminant more often than has been recognized and that it is very rarely the true cause of infection in humans. Typing results show differences between one type strain and all of the other isolates studied in terms of colonial morphology, biochemistry, antimicrobial susceptibility, and ribotyping; these differences suggest that the nomenclature of T. paurometabolum may require further clarification.

Neutrophils contribute to TNF induced myocardial tolerance to ischaemia

Sublethal endotoxin (ETX) pretreatment of rats induces protection from cardiac ischaemia-reperfusion injury. This protective state is associated with increased endogenous myocardial catalase activity. Since tumour necrosis factor (TNF) is one mediator of ETX effects, we hypothesized that (TNF) pretreatment of the rat (30 micrograms/kg ip) 36 h prior to cardiac ischaemia-reperfusion could induce myocardial protection. We found that TNF administration increased both myocardial tolerance to ischaemia reperfusion injury (modified Langendorff, buffer perfusion, global, normothermic ischaemia) and myocardial catalase activity at 36 h. Moreover, we found that 6 h after TNF administration, myocardial hydrogen peroxide (H2O2, assessed by aminotriazole-H2O2 inactivation of catalase) and myocardial neutrophil accumulation (assessed by histology) were both increased. When neutrophil function was inhibited either by neutrophil depletion (vinblastine) or by ibuprofen treatments of the rat before TNF, the protection previously apparent at 36 h was blocked. We conclude that TNF can induce myocardial resistance to ischaemia reperfusion injury. This protection is related to prior tissue neutrophil accumulation and concomitant increases in H2O2 levels.

Expression of Hox-4 genes in the chick wing links pattern formation to the epithelial-mesenchymal interactions that mediate growth

The relationship between the expression of Hox-4 genes in the mesenchyme and the apical ectodermal ridge was investigated in both normal chick wing buds and wing buds treated with retinoic acid. Two conclusions emerge. One is that the activation of Hox-4 domains and the elaboration of Hox-4 gene expression patterns involve cooperation with a signal from the apical ridge. The second is that the domains of expression of 5'-located members of the complex correlate with the maintenance of the thickened ridge which is required for subsequent bud outgrowth.

Nonmycetomic Actinomadura madurae infection in a patient with AIDS

Actinomadura madurae is an aerobic actinomycete which is best known worldwide as the cause of actinomycotic mycetomas. It has not previously been reported to have caused invasive pulmonary or disseminated infection in humans. We describe an AIDS patient with opportunistic A. madurae-induced pneumonia and bacteremia. The isolate from the patient's blood was subjected to dilutional antimicrobial susceptibility tests with 12 antimicrobial agents and was found to have a wide spectrum of susceptibility. This unusual microorganism may be a cause of infections in severely immunosuppressed patients.

Cardiac 5'-nucleotidase activity increases with age and inversely relates to recovery from ischemia

The metabolic basis for the enhanced tolerance of immature hearts to ischemia remains to be elucidated. Loss of high-energy phosphate nucleotides occurs during ischemia/reperfusion in mature (adult) hearts through the breakdown of adenosine triphosphate, diphosphate, and monophosphate (nondiffusible) to adenosine (freely diffusible). However, previous work has shown that after ischemia nondiffusible nucleotides are better retained by immature (neonatal) hearts than by mature hearts. The enzyme responsible for the conversion of adenosine monophosphate to adenosine is 5'-nucleotidase. We therefore hypothesized lower activity of this enzyme in neonatal than in adult myocardium. The purposes of this study were (1) to document 5'-nucleotidase activities in neonatal and adult rabbit myocardium and (2) to correlate differences of 5'-nucleotidase activity with functional recovery from ischemia. Neonatal (5- to 10-day-old) and adult (4- to 6-month-old) rabbit hearts were isolated and perfused (retrograde Langendorff). A left ventricular balloon measured functional parameters. Hearts were subjected to 20 minutes of global 37 degrees C ischemia and 10 minutes of reperfusion followed by freeze clamping. Tissue homogenates were assayed for 5'-nucleotidase by the linked formation of nicotinamide-adenine dinucleotide at 340 nm (Arkesteijn method). Postischemic recovery of developed pressure was 86% +/- 3% in neonates (n = 5) versus 38% +/- 3% in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). 5'-Nucleotidase activity was 4400 +/- 1208 nmol/min/gm in neonates (n = 5) versus 13,938 +/- 830 nmol/min/gm in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). We conclude that (1) 5'-nucleotidase activity is 68% lower in neonatal than in adult myocardium and (2) functional recovery after ischemia inversely relates to 5'-nucleotidase activity.

Activation of the heat shock transcription factor by hypoxia in normal and tumor cell lines in vivo and in vitro

Cells exposed to hypoxia increase their synthesis of a specific set of proteins called oxygen regulated proteins. Recently, three of these proteins have been identified as hemoxygenase, Glucose Regulated Protein 78 kilodaltons and Glucose Regulated Protein 94 kilodaltons. In contrast, reoxygenation from hypoxic conditions increases the synthesis of the heat shock proteins. Although the molecular signals required for regulation of both sets of proteins by hypoxia and reoxygenation are still under investigation, it is known that their expression is regulated at the transcriptional level. This finding suggests that these stresses work either singularly or together to control the activation of nuclear transcription factors which bind distinct regulatory sequences in the promoter region of these genes. One possible nuclear transcription factor which could act as a transcriptional regulator for both hypoxia and reoxygenation gene transcription is the heat shock transcription factor. In this report, we focused on the kinetics of HSF activation by hypoxia in normal and tumor cell lines of murine and human origins. In cell culture, both the normal diploid cell line AG1522 and the tumor cell line JSQ-3 possess the same kinetics of HSF activation (binding to the heat shock element) by hypoxia, with maximal induction at or after 3 hr. We have also shown that the activation of HSF occurs in the SCCVII tumor in vivo without clamping, but not in SCCVII cells grown in monolayers. When SCCVII tumors are dissociated and allowed to reoxygenate in cell culture, HSF binding decreased in 5 hr, and was undetectable after 18 hr. Furthermore, one human tumor biopsy tested for the presence of hypoxia by both the pO2 histograph (Eppendorf, Germany) and HSF binding showed good agreement for both techniques. These results suggest that HSF binding may be a useful marker for monitoring the tumor hypoxia.

The prediction of human tumor radiosensitivity in situ: an approach using chromosome aberrations detected by fluorescence in situ hybridization

No method of predicting the radiation sensitivity of individual human tumors is presently available, and recently published data show that other factors, in addition to the intrinsic radiosensitivity of the tumor cells, may play a role in the in vivo response of human tumors. Since these factors likely involve the tumor milieu (e.g., cell-cell contact and tumor hypoxia), an in situ assay of radiosensitivity is required. Although an analysis based on chromosome damage is the only suitable assay that would fit the requirements of sensitivity and speed of analysis, conventional examination of chromosome damage is impractical. By allowing the visualization of chromosomes in interphase cells, the technique of premature chromosome condensation (PCC) overcomes the need to culture the tumor cells in vitro, but the technical problem remains of counting a small excess number of breaks over the often large pretreatment chromosome number. We demonstrate here that the combination of fluorescence in situ hybridization (FISH) with PCC enormously simplifies the problem by focusing the analysis on a single chromosome. It also allows exchange aberrations to be scored easily. We demonstrate that the FISH technology may also be used to estimate radiation sensitivity from stable reciprocal translocations in metaphase identified by combining whole chromosome painting with a second color hybridization to the repeat sequences common to the centromeres. Since the frequency of stable translocations should correlate with initial chromosome damage, and since these translocations are not preferentially lost from the irradiated tumor cell population by cell death, an estimate of tumor cell killing following 1-5 dose fractions should be possible. Each of these two methods has its advantages, and a careful study of the two should establish which is superior for routine use to determine tumor radiosensitivity in situ.

Homogeneous Hydrogenation With Iridium Complexes. Evidence for Polyhydride Intermediates in the Reduction of α-Pinene

The hydrogenation of α-pinene by Crabtree's catalyst [(cycloocta-1,5-diene)(pyridine)(tricyclo-hexylphosphine)iridium hexafluorophosphate] in dichloromethane, occurs from the endo -face with high stereospecificity. Reaction is accompanied by reversible equilibration with β-pinene, which forms 2% of the equilibrium mixture. The hydrogenation of β-pinene is slower than its isomerization under these conditions. Reductions were carried out with deuterium in order to probe the reaction mechanism. Using the novel technique of 2H-decoupled 13C n.m.r., it was found that a complete analysis of the isotope distribution in the product could be obtained by analysis of the C1 signal, since the possible β-and y-perturbations gave rise to distinct spectral shifts. All possible isotopomers corresponding to deuterium substitution at C2, C3 and C10 were observed, and no other site of deuteration was detected. Analysis of the product demonstrated that iridium polyhydrides are likely to be involved, since the results are inconsistent with simpler mechanistic pathways.

Disseminated Nocardia transvalensis infection: an unusual opportunistic pathogen in severely immunocompromised patients

Nocardia infections are infrequently recognized in humans. Nocardia species may cause severe life-threatening infections among immunocompromised patients and have been reported to cause actinomycotic mycetomas, primarily in tropical areas. Two severely immunocompromised patients had disseminated N. transvalensis infections. One had underlying X-linked variant chronic granulomatous disease and died of disseminated N. transvalensis infection, which was diagnosed only at postmortem examination. The second patient developed N. transvalensis pneumonia within 3 months of undergoing renal transplantation and died of disseminated mixed Pseudallescheria boydii and N. transvalensis infections. Thus, N. transvalensis may cause invasive and potentially fatal pulmonary and disseminated infections. Accordingly, clinical microbiology laboratories should become proficient in identifying this uncommon aerobic actinomycete.

The frequency of translocations after treatment for Hodgkin's disease

We studied the frequency of translocations in peripheral blood lymphocytes of patients with Hodgkin's disease to determine the extent of chromosome changes induced by radiation or radiation and chemotherapy. Comparisons were made to patients with second cancers to determine if this population is more susceptible to the effects of treatment. Group one included six patients with newly diagnosed Hodgkin's disease who were treated with radiation only. Group two included Hodgkin's disease patients who were treated 12-24 years previously and have been continuously free of disease. Five of these patients were treated with radiation only and five patients received radiation and mechlorethaminehydrochloride, oncovin, procarbazine, prednisone (MOPP) chemotherapy for six cycles. Group three included three patients who developed a second cancer after successful treatment for Hodgkin's disease. Two of these patients had a sarcoma within the radiation field and one had breast cancer. Metaphase spreads were obtained from cultured lymphocytes and hybridized with a chromosome 4 specific probe. After fluorescein staining, approximately 1000 metaphases were scored per patient. In group one only one patient in six demonstrated translocations in chromosome 4 before treatment for a mean frequency of .0009. After treatment the frequency of translocations increased to a mean of .016 (p = .036) (range .006-.034). Group two patients treated with radiation only had a mean translocation frequency of .012 (range .004-.022) in comparison to the radiation/mechlorethaminehydrochloride, oncovin, procarbazine, prednisone chemotherapy treated patients who demonstrated a mean frequency of .016 (p = .425) (range .0009-.023). The third group of second cancer patients showed inconsistent translocation frequencies of .002, .020, and .035. Of these patients, the one who demonstrated the greatest frequency of translocations (.035) was treated with mechlorethaminehydrochloride, oncovin, procarbazine, prednisone/adriamycin, bleomycin, vinblastine, decadron) and radiation. Our data demonstrates a statistically significant increase in translocations detected after radiation. When compared to combined modality therapy a greater mean frequency of translocations is observed over radiation alone; however, this was not statistically significant. In the three patients who developed second cancers in our series we saw no consistent increase in translocation frequency compared to Hodgkin's disease patients who did not develop a second cancer.

Second-generation 1,2,4-benzotriazine 1,4-di-N-oxide bioreductive anti-tumor agents: pharmacology and activity in vitro and in vivo

SR 4233 (1,2,4-benzotriazine-3-amine 1,4-dioxide) will soon be entering Phase I clinical trials as a new bioreductive cytotoxic agent for the treatment of solid tumors in combination with fractionated radiotherapy. We have selected 3 from over 50 analogues of SR 4233 which showed particular promise as second generation bioreductive antitumor agents. These compounds, when compared to SR 4233, have higher hypoxic toxicity and comparable or higher oxic to hypoxic cytotoxicity ratios in vitro and similar animal toxicity. We have compared the effectiveness of these three compounds with SR 4233 in two tumor systems and have examined some pharmacokinetic properties. The results show that replacement of the amino group at the 3-position of SR 4233 with either a hydrogen or an N,N-dialkylaminoalkylamino group shortens the half-life of these compounds in the blood because of the combined effects of partition coefficients, basicity, and higher reactivity. SR 4754 and SR 4755, the N,N-dialkylaminoalkylamino derivatives, exhibited shorter plasma half-lives than SR 4233 but exhibited lower anti-tumor activity than SR 4233 based on equal mouse toxicity in a fractionated regimen. SR 4482, with the hydrogen substitution and very high electron affinity, possessed a very short blood half life yet retained similar anti-tumor activity as SR 4233.

Computerized histographic oxygen tension measurements of murine tumors

As further work on tumor oxygenation results in the development of agents capable of modulating hypoxic cell radiosensitivity, and chemotherapeutic agents capable of targeting hypoxic cells, knowledge of relative tumor oxygenation takes on greater importance. The pO2 Histograph was used to characterize the oxygen tension of a murine sarcoma (RIF1) and a murine carcinoma (SCCVII), each with different hypoxic fractions. These tumors were studied sequentially to assess the suitability of the Histograph both as a research tool and, ultimately, as a clinical monitor of tumor hypoxia.

NLA-1: a 2-nitroimidazole radiosensitizer targeted to DNA by intercalation

Targeting of electron affinic radiosensitizers to DNA via reversible non-covalent intercalative binding has potential for increasing sensitizer concentrations locally at the DNA target while decreasing accessibility to reductases responsible for bioactivation and cytotoxicity. We have prepared an DNA-targeted acridine-linked 2-nitroimidazole (NLA-1) as an example of such a compound. NLA-1 binds reversibly to DNA with an affinity similar to 9-aminoacridine, and is approximately 1000 times more potent than MISO as a cytotoxin, despite a similar reduction potential. It shows less enhancement of cytotoxicity under hypoxia (5- to 6-fold) than does MISO (approximately 11-fold), but is a potent hypoxia-selective radiosensitizer in AA8 cells with a concentration for an enhancement ratio of 1.6 (C1.6) of 9 microM. The mean intracellular concentration at the C1.6 is 400 microM, on which basis its potency is about twice that of MISO. The in vitro therapeutic index (aerobic cytotoxic potency/hypoxic C1.6) of NLA-1 is approximately 6-fold lower than that for MISO. NLA-1 lacks radiosensitizing activity against SCCVII or EMT6 tumors in vivo at the maximum tolerated dose (MTD) of 100 mumol.kg-1.