The mitochondrial DNA HVI and HVII sequences and haplogroup distribution in a population sample from Vietnam

BACKGROUND

Mitochondrial DNA (mtDNA) analysis has been used in forensics and requires well-established population databases for statistical interpretations. However, high-quality mtDNA data from Vietnamese population samples have been limited.

AIM

To examine the mtDNA sequences and haplogroup compositions of a Vietnamese population to provide an mtDNA dataset that can further be used to construct a Vietnamese-specific reference database.

SUBJECTS AND METHODS

A total of 173 Vietnamese individuals were analysed for two hypervariable regions (HVI and HVII) of mtDNA. Forensic parameters were calculated and haplogroup assignment was performed based on the resulting mtDNA haplotypes. Genetic relationships between the Vietnamese and other Asian populations were investigated through principal component analysis (PCA) and pairwise F_st.

RESULTS

The Vietnamese population sample consisted of 145 different haplotypes with a random match probability of 0.96%, a power of discrimination of 0.9904, and a haplotype diversity of 0.9962. The samples were assigned to 83 haplogroups that were commonly reported in Asia. PCA and pairwise F_st revealed close relationships of the Vietnamese population with other Asian populations, especially with populations in proximity.

CONCLUSION

The results from this study can contribute to the current genetic information content as a supplementary mtDNA reference dataset for forensic investigations and phylogenetic research.

Pyr1-Mediated Pharmacological Inhibition of LIM Kinase Restores Synaptic Plasticity and Normal Behavior in a Mouse Model of Schizophrenia

The search for effective treatments for neuropsychiatric disorders is ongoing, with progress being made as brain structure and neuronal function become clearer. The central roles played by microtubules (MT) and actin in synaptic transmission and plasticity suggest that the cytoskeleton and its modulators could be relevant targets for the development of new molecules to treat psychiatric diseases. In this context, LIM Kinase - which regulates both the actin and MT cytoskeleton especially in dendritic spines, the post-synaptic compartment of the synapse - might be a good target. In this study, we analyzed the consequences of blocking LIMK1 pharmacologically using Pyr1. We investigated synaptic plasticity defects and behavioral disorders in MAP6 KO mice, an animal model useful for the study of psychiatric disorders, particularly schizophrenia. Our results show that Pyr1 can modulate MT dynamics in neurons. In MAP6 KO mice, chronic LIMK inhibition by long-term treatment with Pyr1 can restore normal dendritic spine density and also improves long-term potentiation, both of which are altered in these mice. Pyr1 treatment improved synaptic plasticity, and also reduced social withdrawal and depressive/anxiety-like behavior in MAP6 KO mice. Overall, the results of this study validate the hypothesis that modulation of LIMK activity could represent a new therapeutic strategy for neuropsychiatric diseases.

Immunization with the H5N1 Recombinant Vaccine Candidate Induces High Protection in Chickens against Vietnamese Highly Pathogenic Avian Influenza Virus Strains

Vietnam is one of the countries most affected worldwide by the highly pathogenic avian influenza (HPAI) virus, which caused enormous economic loss and posed threats to public health. Over nearly two decades, with the antigenic changes in the diversified H5Ny viruses, the limited protective efficacy of the available vaccines was encountered. Therefore, it is necessary to approach a technology platform for the country to accelerate vaccine production that enables quick response to new influenza subtypes. This study utilized a powerful reverse genetics technique to successfully generate a recombinant H5N1 vaccine strain (designated as IBT-RG02) containing two surface proteins (haemagglutinin (HA) and neuraminidase (NA)) from the HPAI H5N1 (A/duck/Vietnam/HT2/2014(H5N1)) of the dominant clade 2.3.2.1c in Vietnam during 2012–2014. Importantly, the IBT-RG02 vaccine candidate has elicited high antibody titres in chickens (geometric mean titre (GMT) of 6.42 and 6.92, log₂ on day 14 and day 28 p.i., respectively). To test the efficacy, immunized chickens were challenged with the circulating virulent strains. As results, there was a high protection rate of 91.6% chickens against the virulent A/DK/VN/Bacninh/NCVD-17A384/2017 of the same clade and a cross-protection of 83.3% against A/duck/TG/NAVET(3)/2013 virus of clade 1.1. Our promising results showed that we can independently master the reverse genetics technology for generation of highly immunogenic vaccine candidates, and henceforth, it is a timely manner to reformulate avian influenza virus vaccines against variable H5 clade HPAI viruses in Vietnam.

Association between diabetes mellitus and mortality among patients with tuberculosis in California, 2010-2014

SETTING

Studies of US populations have produced conflicting findings about the impact of diabetes mellitus (DM) on tuberculosis (TB) treatment outcomes.

OBJECTIVE

To investigate the association between DM and all-cause mortality among patients on anti-tuberculosis treatment in California, USA.

DESIGN

Using TB surveillance data, we conducted a retrospective analysis of California patients with culture-confirmed TB who started anti-tuberculosis treatment during 2010-2014. We used Cox proportional hazards models to estimate the association of DM with all-cause mortality and conducted a sensitivity analysis to estimate the attenuating effect of unmeasured confounding by body mass index.

RESULTS

Among 8461 patients with TB, 2124 (25.1%) had DM and 713 (8.4%) died during anti-tuberculosis treatment. A higher proportion of TB-DM patients died (13.1% vs. 6.8% TB-no DM). After adjusting for confounders, DM was associated with mortality (adjusted hazards ratio [aHR] 1.35, 95%CI 1.15-1.57). There was effect modification by human immunodeficiency virus (HIV) status, with HIV-positive patients having an aHR of 5.33 (95%CI 1.76-16.12).

CONCLUSION

TB patients with DM had a greater hazard of death during anti-tuberculosis treatment than those without DM. Further investigation into the impact of HIV on the relation of DM to death is necessary.

Aryl hydrocarbon receptor antagonism and its role in rheumatoid arthritis

Although rheumatoid arthritis (RA) is the most common autoimmune disease, affecting approximately 1% of the population worldwide, its pathogenic mechanisms are poorly understood. Tobacco smoke, an environmental risk factor for RA, contains several ligands of aryl hydrocarbon receptor (Ahr), also known as dioxin receptor. Ahr plays critical roles in the immune system. We previously demonstrated that Ahr in helper T-cells contributes to development of collagen-induced arthritis, a mouse model of RA. Other studies have shown that cigarette smoke condensate and pure Ahr ligands exacerbate RA by altering bone metabolism and inducing proinflammatory responses in fibroblast-like synoviocytes. Consistent with these findings, several Ahr antagonists such as α-naphthoflavone, resveratrol, and GNF351 reverse the effect of Ahr ligands in RA pathogenesis. In this review, we summarize the current knowledge of Ahr function in the immune system and the potential clinical benefits of Ahr antagonism in treating RA.

Measurement of the ββ decay half-life of 130Te with the NEMO-3 detector

We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of (130)Te in the form of enriched and natural tellurium foils. The ββ decay rate of (130)Te is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T(½)(2ν) = [7.0 ± 0.9(stat) ± 1.1(syst)] × 10(20) yr. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.

Non-soy legume consumption lowers cholesterol levels: a meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

Studies evaluating the effect of legume consumption on cholesterol have focused on soybeans, however non-soy legumes, such as a variety of beans, peas, and some seeds, are commonly consumed in Western countries. We conducted a meta-analysis of randomized controlled trials evaluating the effects of non-soy legume consumption on blood lipids.

METHODS AND RESULTS

Studies were retrieved by searching MEDLINE (from January 1966 through July 2009), EMBASE (from January 1980 to July 2009), and the Cochrane Collaboration's Central Register of Controlled Clinical Trials using the following terms as medical subject headings and keywords: fabaceae not soybeans not isoflavones and diet or dietary fiber and cholesterol or hypercholesterolemia or triglycerides or cardiovascular diseases. Bibliographies of all retrieved articles were also searched. From 140 relevant reports, 10 randomized clinical trials were selected which compared a non-soy legume diet to control, had a minimum duration of 3 weeks, and reported blood lipid changes during intervention and control. Data on sample size, participant characteristics, study design, intervention methods, duration, and treatment results were independently abstracted by 2 investigators using a standardized protocol. Data from 10 trials representing 268 participants were examined using a random-effects model. Pooled mean net change in total cholesterol for those treated with a legume diet compared to control was -11.8 mg/dL (95% confidence interval [CI], -16.1 to -7.5); mean net change in low-density lipoprotein cholesterol was -8.0mg/dL (95% CI, -11.4 to -4.6).

CONCLUSION

These results indicate that a diet rich in legumes other than soy decreases total and LDL cholesterol.

Benzo[e]pyridoindoles, novel inhibitors of the aurora kinases

Aurora kinases are serine/threonine protein kinases that are involved in cancer development and are important targets for cancer therapy. By high throughput screening of a chemical library we found that benzo[e]pyridoindole derivatives inhibited Aurora kinase. The most potent compound (compound 1) was found to be an ATP competitive inhibitor, which inhibited in vitro Aurora kinases at the nanomolar range. It prevented, ex vivo, the phosphorylation of Histone H3, induced mitosis exit without chromosome segregation, known phenomena observed upon Aurora B inactivation. This compound was also shown to affect the localization of Aurora B, since in the presence of the inhibitor the enzyme was delocalized on the whole chromosomes and remained associated with the chromatin of newly formed nuclei. In addition, compound 1 inhibited the growth of different cell lines derived from different carcinoma. Its IC(50) for H358 NSCLC (Non Small Cancer Lung Cells), the most sensitive cell line, was 145 nM. Furthermore compound 1 was found to be efficient towards multicellular tumor spheroid growth. It exhibited minimal toxicity in mice while it had some potency towards aggressive NSCLC tumors. Benzo[e]pyridoindoles represent thus a potential new lead for the development of Aurora kinase inhibitors.

Small-molecule inhibition of HIV pre-mRNA splicing as a novel antiretroviral therapy to overcome drug resistance

The development of multidrug-resistant viruses compromises antiretroviral therapy efficacy and limits therapeutic options. Therefore, it is an ongoing task to identify new targets for antiretroviral therapy and to develop new drugs. Here, we show that an indole derivative (IDC16) that interferes with exonic splicing enhancer activity of the SR protein splicing factor SF2/ASF suppresses the production of key viral proteins, thereby compromising subsequent synthesis of full-length HIV-1 pre-mRNA and assembly of infectious particles. IDC16 inhibits replication of macrophage- and T cell-tropic laboratory strains, clinical isolates, and strains with high-level resistance to inhibitors of viral protease and reverse transcriptase. Importantly, drug treatment of primary blood cells did not alter splicing profiles of endogenous genes involved in cell cycle transition and apoptosis. Thus, human splicing factors represent novel and promising drug targets for the development of antiretroviral therapies, particularly for the inhibition of multidrug-resistant viruses.

Structure-activity relationship in the 3-iodo-4-phenoxypyridinone (IOPY) series: The nature of the C-3 substituent on anti-HIV activity

As part of a systematic SAR study on the 3-iodo-4-phenoxypyridinone 3 (IOPY) type non-nucleoside reverse transcriptase inhibitors, the analogues 4a-4z bearing different C-3 substituents were synthesized and evaluated for their anti-HIV activity against wild-type HIV-1 and four of the principal HIV mutant strains (K103N, Y181C, Y188L, and I100L). The results show that the 3-vinyl analogue 4j is the only compound which displays anti-HIV activity comparable to IOPY 3, and in this respect represents a possible back-up to this lead molecule.

Crystal structures for HIV-1 reverse transcriptase in complexes with three pyridinone derivatives: a new class of non-nucleoside inhibitors effective against a broad range of drug-resistant strains

In the treatment of AIDS, the efficacy of all drugs, including non-nucleoside inhibitors (NNRTIs) of HIV-1 reverse transcriptase (RT), has been limited by the rapid appearance of drug-resistant viruses. Lys103Asn, Tyr181Cys, and Tyr188Leu are some of the most common RT mutations that cause resistance to NNRTIs in the clinic. We report X-ray crystal structures for RT complexed with three different pyridinone derivatives, R157208, R165481, and R221239, at 2.95, 2.9, and 2.43 A resolution, respectively. All three ligands exhibit nanomolar or subnanomolar inhibitory activity against wild-type RT, but varying activities against drug-resistant mutants. R165481 and R221239 differ from most NNRTIs in that binding does not involve significant contacts with Tyr181. These compounds strongly inhibit wild-type HIV-1 RT and drug-resistant variants, including Tyr181Cys and Lys103Asn RT. These properties result in part from an iodine atom on the pyridinone ring of both inhibitors that interacts with the main-chain carbonyl oxygen of Tyr188. An acrylonitrile substituent on R165481 substantially improves the activity of the compound against wild-type RT (and several mutants) and provides a way to generate novel inhibitors that could interact with conserved elements of HIV-1 RT at the polymerase catalytic site. In R221239, there is a flexible linker to a furan ring that permits interactions with Val106, Phe227, and Pro236. These contacts appear to enhance the inhibitory activity of R221239 against the HIV-1 strains that carry the Val106Ala, Tyr188Leu, and Phe227Cys mutations.

Selective modification of alternative splicing by indole derivatives that target serine-arginine-rich protein splicing factors

The prevalence of alternative splicing as a target for alterations leading to human genetic disorders makes it highly relevant for therapy. Here we have used in vitro splicing reactions with different splicing reporter constructs to screen 4,000 chemical compounds for their ability to selectively inhibit spliceosome assembly and splicing. We discovered indole derivatives as potent inhibitors of the splicing reaction. Importantly, compounds of this family specifically inhibit exonic splicing enhancer (ESE)-dependent splicing, because they interact directly and selectively with members of the serine-arginine-rich protein family. Treatment of cells expressing reporter constructs with ESE sequences demonstrated that selected indole derivatives mediate inhibition of ESE usage in vivo and prevent early splicing events required for HIV replication. This discovery opens the exciting possibility of a causal pharmacological treatment of aberrant splicing in human genetic disorders and development of new antiviral therapeutic approaches.

Antiviral activity of 4-benzyl pyridinone derivatives as HIV-1 reverse transcriptase inhibitors

In this overview, the antiviral properties of the Curie-pyridinone compounds, a new class of non-nucleoside reverse transcriptase inhibitors (NNRTIs) developed as anti-HIV agents, are described. These compounds are hybrids between hydroxyethoxymethyl-phenylthiothymine (HEPT) and Merck pyridinones. Several structure-activity relationships (SAR) studies between HIV-1 reverse transcriptase (RT) and the Curie-pyridinones are described. The Curie-pyridinones are potent inhibitors of both HIV-1 replication in cell culture and of HIV-1 RT activity in vitro. They are specific to HIV-1 and do not inhibit the replication of HIV-2. The mechanism of inhibition is non-competitive with respect to the natural substrate dGTP. For these reasons, the Curie-pyridinones can be considered as non-nucleoside inhibitors of HIV-1 RT. Moreover, they have the unusual ability to reach the reverse transcription complex inside the extracellular virions and may therefore be useful as retrovirucides. This might lead to the design and synthesis of new drugs able to interact with the retroviral enzyme inside the viral core.

4-Benzyl and 4-Benzoyl-3-dimethylaminopyridin-2(1H)-ones: In Vitro Evaluation of New C-3-Amino-Substituted and C-5,6-Alkyl-Substituted Analogues against Clinically Important HIV Mutant Strains

In a program to optimize the anti-HIV activity of the 4-benzyl and 4-benzoyl-3-dimethylaminopyridinones 9 and 10, lead compounds in a new class of highly potent non-nucleoside type inhibitors of HIV-1 reverse transcriptase, modification of the alkyl substitutents at the C-5 and C-6 positions on the pyridinone ring and of the substitutents on the C-3 amino group has been studied. Of the 17 new 5/6-modified analogues prepared, compounds 31b and 32b substituted at C-5 by an extended nonpolar chain containing an ether function and a C-6 methyl group and compound 35 bearing a C-5 ethyl/C-6 hydroxymethyl substituent pattern were selected on the basis of their in vitro activity against wild-type HIV and the three principle mutant strains, K103N, Y181C, and Y188L. When tested further, it was shown that these molecules, and in particular compound 35, are globally more active than 9, 10, and efavirenz against an additional eight single [L100I, K101E, V106A, E138K, V179E, G190A/S, and F227C] and four double HIV mutant strains [L100I + K103N, K101E + K103N, K103N + Y181C, and F227L + V106A], which are clinically relevant. Concerning modulation of the N-3 substituent, 36 new analogues were prepared. Of these, the N-methyl-N-(2-methoxyethyl)-substituted compounds 40, 42, and 62, as well as the doubly modified compounds 77a and 77b, were selected from the initial screen and were subsequently shown to be active at sub-micromolar concentrations (IC(50)'s) against all the other mutant strains except K103N + Y181C and F227L + V106A. Two possible, but distinct, modes of binding of these analogues in RT were suggested from molecular modeling studies. The preferred mode of binding for compound 62, corresponding to the predicted "orientation 1", was revealed in the X-ray crystal structure of the compound 62-RT complex.

4-Benzyl- and 4-Benzoyl-3-dimethylaminopyridin-2(1H)-ones, a New Family of Potent Anti-HIV Agents: Optimization and in Vitro Evaluation against Clinically Important HIV Mutant Strains

The 4-benzyl and 4-benzoyl-3-dimethylaminopyridinones 13 and 14 are representatives of a new class of highly potent non nucleoside type inhibitors of HIV-1 reverse transcriptase. To conduct SAR studies on these two lead compounds, 102 new analogues were prepared. Thirty-three compounds displayed nanomolar range activity in vitro against wild-type HIV-1, and among these, 18 were active against the 103N, Y181C, and Y188L mutant strains with IC50 values inferior to 1 microM. Evaluation of this group of analogues against an additional eight single [100I, 101E, 106A, 138K, 179E, 190A, 190S, 227C] and four double HIV mutant strains [100I + 103N, 101E + 103N, 103N + 181C, and 227L + 106A], which are often present in HIV infected patients, permitted the selection of eight compounds, 17x, 18b, 18c, 18f, 18g, 27, 30, and 42, which are globally more active than the lead molecules 13/14, emivirine and the currently used NNRTI, nevirapine. Further comparison of the 3'-CN-substituted benzoylpyridinone compound 18c, and the corresponding 3'-acrylonitrile-substituted analogue 30, to efavirenz, the reference molecule in anti-HIV therapy today, revealed that the pyridinone analogues displayed a superior inhibition profile in the in vitro cellular assay system. These results form a solid basis for continued optimization of the pyridinone series.

3-iodo-4-phenoxypyridinones (IOPY's), a new family of highly potent non-nucleoside inhibitors of HIV-1 reverse transcriptase

Building upon the potent anti-HIV-1 activities observed for the 3-dimethylamino-4-benzylpyridinone 2, and the corresponding 4-aryloxypyridinone analogue 3, a concise and efficient route to the 3-iodo-4-aryloxypyridinones 14a-c (IOPY's) was developed. This involved reaction of the 4-hydroxy substituted pyridinone 10 with the requisite dichloroiodobenzene reagent 11. IOPY compound 14c is active at IC(50)=1-45 nM against wild type HIV-1 and a panel of six major simple/double HIV mutant strains.

Non-nucleoside inhibitors of HIV-1 reverse transcriptase inhibit phosphorolysis and resensitize the 3'-azido-3'-deoxythymidine (AZT)-resistant polymerase to AZT-5'-triphosphate

Removal of 3'-azido-3'deoxythymidine (AZT) 3'-azido-3'-deoxythymidine 5'-monophosphate (AZTMP) from the terminated primer mediated by the human HIV-1 reverse transcriptase (RT) has been proposed as a relevant mechanism for the resistance of HIV to AZT. Here we compared wild type and AZT-resistant (D67N/K70R/T215Y/K219Q) RTs for their ability to unblock the AZTMP-terminated primer by phosphorolysis in the presence of physiological concentrations of pyrophosphate or ATP. The AZT-resistant enzyme, as it has been previously described, showed an increased ability to unblock the AZTMP-terminated primer by an ATP-dependent mechanism. We found that only mutations in the p66 subunit were responsible for this ability. We also found that three structurally divergent non-nucleoside reverse transcriptase inhibitor (NNRTI), nevirapine, TIBO, and a 4-arylmethylpyridinone derivative, were able to inhibit the phosphorolytic activity of the enzyme, rendering the AZT-resistant RT sensitive to AZTTP. The 4-arylmethylpyridinone derivative proved to be about 1000-fold more potent in inhibiting phosphorolysis than nevirapine or TIBO. Moreover, combinations of AZTTP with NNRTIs exhibited an exceptionally high degree of synergy in the inhibition of AZT-resistant enzyme only when ATP or PPi were present, indicating that inhibition of phosphorolysis was responsible for the synergy found in the combination. Our results not only demonstrate the importance of phosphorolysis concerning HIV-1 RT resistance to AZT but also point to the implication of this activity in the strong synergy found in some combinations of NNRTIs with AZT.

Synthesis and binding properties of oligo-2'-deoxyribonucleotides conjugated with triple-helix-specific intercalators: benzo[e] and benzo[g] pyridoindoles

DNA binding compounds, such as benzo[e] (BePI) and benzo[g] pyridoindole (BgPI) derivatives, exhibit preferential stabilization of triple helices. We report here the synthesis of a series of pyrimidine triple-helix-forming oligo-2'-deoxyribonucleotides conjugated with these molecules. BePI was coupled to the 5-position of 2'-deoxyuridine via two linkers of different sizes attached to its 11-position and placed at either the 5'-end, inside the sequence, or at both the 5'-end and the internal positions using periodate oxidation of a diol-containing oligonucleotide followed by reductive coupling with amino-linked BePI. The same BePI derivatives were also linked to the oligonucleotide chain via internucleotidic phosphorothiolate or phosphoramidate linkages. A mixture of diastereoisomers was prepared as well as separate pure Rp and Sp isomers. A BePI derivative, with two different linkers attached to its 3-position, and BgPI derivatives were also linked to the 5-position of a 2'-deoxyuridine located at either the 5'-end or inside the sequence, as well as to the beta- anomeric position of an additional 2'- deoxyribose placed inside the sequence. The binding properties of these oligonucleotide-benzopyridoindoles conjugates with their double-stranded DNA target was studied by absorption spectroscopy.

New concepts for nutrition education in an era of welfare reform

In response to welfare reform and the Food Stamp Nutrition Education Program's (FSNEP) goal of increasing clients' self-sufficiency, a literature review and small exploratory study were conducted to gain insight into a potential approach that would go beyond current nutrition education methods. Interviews with 17 FSNEP participants showed a widespread willingness to share food-related skills that others wanted to learn, some interest in cooperating on food-related projects, and frequent cases of social and geographic isolation. Based on these preliminary findings, we suggest the development and evaluation of nutrition education programs that appreciate and build on existing abilities of participants, provide opportunities for self-directed learning and activities, and build social support, social networks, and trust among participants while linking them to the broader community.

De novo establishment and cost-effectiveness of Papanicolaou cytology screening services in the Socialist Republic of Vietnam

BACKGROUND

Cervical carcinoma is the leading cause of cancer-related death among women in the developing world. The absence of cervical screening in Vietnam and other developing countries is due in large part to the perceived expense of implementing Papanicolaou cytology screening services, although, to the authors' knowledge, the cost-effectiveness of establishing such services has never been studied in a developing country.

METHODS

Using decision analytic methods, the authors assessed cost-effectiveness of Pap screening from a societal perspective in Vietnam, the world's 9th most populous developing country (estimated 1999 population, 79 million). Outcomes measured included life expectancy, cervical carcinoma incidence, cost per woman, and cost-effectiveness.

RESULTS

Total costs to establish a nationwide 5-year interval Pap screening program in Vietnam will average less than $148,400 annually during the 10-year time period assumed necessary to develop the program and may be considerably lower if only high risk geographic areas are targeted. Maintenance costs will average less than $0.092 annually per woman in the target screening population. Assuming 70% program participation, cervical carcinoma incidence will decrease from 26 in 100,000 to 14.8 in 100,000, and cost-effectiveness will be $725 per discounted life-year. Several assumptions used in this analysis constitute biases against the effectiveness of Pap screening, which in reality may be significantly more cost-effective than reported here.

CONCLUSIONS

Contrary to widespread belief, Pap screening in developing countries such as Vietnam is extraordinarily inexpensive and appears to be cost-effective. Because prospects are uncertain regarding useful alternatives to the Pap test, the evidence-based argument for establishing conventional Pap screening services in developing countries such as Vietnam is compelling. Population-based conventional Pap screening services have been established de novo in Vietnam and are now operational.

Outcomes of contact investigations of infectious tuberculosis patients

The objective of this study was to describe outcomes of tuberculosis (TB) contact investigations, factors correlated with those outcomes, and current successes and ways to improve TB contact investigations. We abstracted clinic records of a representative U.S. urban sample of 1,080 pulmonary, sputum-smear(+) TB patients reported to CDC July 1996 through June 1997 and the cohort of their 6,225 close contacts. We found a median of four close contacts per patient. Fewer contacts were identified for homeless patients. A visit to the patient's residence resulted in two additional (especially child) contacts identified. Eighty-eight percent of eligible contacts received tuberculin skin tests (TSTs). Recording the last exposure date to the infectious patient facilitated follow-up TST provision. Thirty-six percent of contacts were TST(+). Household contacts and contacts to highly smear(+) or cavitary TB patients were most likely to be TST(+). Seventy-four percent of TST(+) contacts started treatment for latent TB infection (LTBI), of whom 56% completed. Sites using public health nurses (PHNs) started more high-risk TST(-) contacts on presumptive treatment for LTBI. Using directly observed treatment (DOT) increased the likelihood of treatment completion. We documented outcomes of contact investigation efforts by urban TB programs. We identified several successful practices, as well as suggestions for improvements, that will help TB programs target policies and procedures to enhance contact investigation effectiveness.

Synthesis and antiviral activity of 4-benzyl pyridinone derivatives as potent and selective non-nucleoside human immunodeficiency virus type 1 reverse transcriptase inhibitors

Several 4-benzyl analogues of 5-ethyl-6-methyl-4-(phenylthio)pyridin-2(1H)-ones were synthesized and evaluated for their anti-HIV-l activities. Key transformations include metalation at the 4-C-position of 5-ethyl-2-methoxy-6-methyl-3-pivaloylaminopyridine (5) and its coupling with benzyl bromide or benzaldehyde derivatives. Biological studies revealed that some of the new 4-benzylpyridinones show potent HIV-1 specific reverse transcriptase inhibitory properties. Compounds 14, 19, and 27, which inhibit the replication of HIV-1 in CEM-SS cells, with IC(50) values ranging from 0.2 to 6 nM are the most active compounds in this series. Biochemical studies showed that compound 27 strongly inhibited the activity of a recombinant HIV-1 RT. Moreover, the infectivity of isolated HIV-1 particles was severely decreased after exposure to compound 27. Although cross resistance is frequently observed between non-nucleoside reverse transcriptase inhibitors, compound 27 was capable of inhibiting a virus resistant to nevirapine with an IC(50) of 40 nM.

Incidence of childhood cancer in Ho Chi Minh City, Vietnam, 1995-97

Incidence rates of childhood cancer for the city of Ho Chi Minh are presented for the first time. For the 3-year period 1995-97, a total of 302 cancer cases were registered in children under 15 years of age, with a male to female ratio of 1.1. The overall crude rate was 78.8 and the age-standardised incidence rate was 88.4 per million person-years, which was low in comparison with other countries in eastern Asia and with the predominantly white population of Australia. Leukaemia (principally acute lymphocytic), brain tumours and lymphomas were the most common childhood neoplasms, which is consistent with the pattern observed in other registries of the region. The rate of retinoblastoma was higher than in the other regional registries. On the other hand, no cases of hepatocellular carcinoma were registered.

Synthesis and evaluation of "AZT-HEPT", "AZT-pyridinone", and "ddC-HEPT" conjugates as inhibitors of HIV reverse transcriptase

To test the concept that HIV reverse transcriptase could be effectively inhibited by "mixed site inhibitors", a series of seven conjugates containing both a nucleoside analogue component (AZT 1, ddC 2) and a nonnucleoside type inhibitor (HEPT analogue 12, pyridinone 27) were synthesized and evaluated for their ability to block HIV replication. The (N-3 and C-5)AZT-HEPT conjugates 15, 22, and 23 displayed 2-5 microM anti-HIV activity, but they had no effect on the replication of HIV-2 or the HIV-1 strain with the Y181C mutation. The (C-5)AZT-pyridinone conjugates 34-37 were found to be inactive. In marked contrast, the ddC-HEPT molecule 26 displayed the same potency (EC(50) = 0.45 microM) against HIV-1 (wild type and the Y181C nevirapine-resistant strain) and HIV-2 in cell culture. No synergistic effect was observed for these bis-substrate inhibitors, suggesting that the two individual inhibitor components in these molecules do not bind simultaneously in their respective sites. Interestingly, however, the results indicate that the AZT-HEPT conjugates and the ddC-HEPT derivative 26 inhibit reverse transcriptase (RT) in an opposite manner. One explanation for this difference is that the former compounds interact preferentially with the hydrophobic pocket in RT, whereas 26 (after supposed triphosphorylation) inhibits RT through binding in the catalytic site.

A new family of sequence-specific DNA-cleaving agents directed by triple-helical structures: benzopyridoindole-EDTA conjugates

Sequence-specific DNA recognition can be achieved by oligonucleotides that bind to the major groove of oligopyrimidine x oligopurine sequences. These intermolecular structures could be used to modulate gene expression and to create new tools for molecular biology. Here we report the synthesis and biochemical characterization of triple helix-specific DNA cleaving reagents. It is based on the previously reported triplex-specific ligands, benzo[e]pyridoindole (BePI) and benzo[g]pyridoindole (BgPI), covalently attached to ethylenediaminotetraacetic acid (EDTA). In the presence of iron, a reducing agent and molecular oxygen, BgPI-EDTA x FeII but not BePI-EDTA x FeII induced a double-stranded cut in a plasmid DNA at the single site where a triplex-forming oligonucleotide binds. At single nucleotide resolution, it was found that upon triplex formation BePI-EDTA x FeII led to cleavage of the pyrimidine strand and protection of the purine strand. BgPI-EDTA x FeII cleaved both strands with similar efficiency. The difference in cleavage efficiency between the two conjugates was rationalized by the location of the EDTA x FeII moiety with respect to the grooves of DNA (major groove: BePI-EDTA x FeII, minor groove: BgPI-EDTA x FeII). This work paves the way to the development of a new class of triple helix directed DNA cleaving reagents. Such molecules will be of interest for sequence-specific DNA cleavage and for investigating triple-helical structures, such as H-DNA, which could play an important role in the control of gene expression in vivo.

Design of a triple-helix-specific cleaving reagent

BACKGROUND

Double-helical DNA can be recognized sequence specifically by oligonucleotides that bind in the major groove, forming a local triple helix. Triplex-forming oligonucleotides are new tools in molecular and cellular biology and their development as gene-targeting drugs is under intensive study. Intramolecular triple-helical structures (H-DNA) are expected to play an important role in the control of gene expression. There are currently no good probes available for investigating triple-helical structures. We previously reported that a pentacyclic benzoquinoquinoxaline derivative (BQQ) can strongly stabilize triple helices.

RESULTS

We have designed and synthesized the first triple-helix-specific DNA cleaving reagent by covalently attaching BQQ to ethylenediaminetetraacetic acid (EDTA). The intercalative binding of BQQ should position EDTA in the minor groove of the triple helix. In the presence of Fe(2+) and a reducing agent, the BQQ-EDTA conjugate can selectively cleave an 80 base pair (bp) DNA fragment at the site where an oligonucleotide binds to form a local triple helix. The selectivity of the BQQ-EDTA conjugate for a triplex structure was sufficiently high to induce oligonucleotide-directed DNA cleavage at a single site on a 2718 bp plasmid DNA.

CONCLUSIONS

This new class of structure-directed DNA cleaving reagents could be useful for cleaving DNA at specific sequences in the presence of a site-specific, triple-helix-forming oligonucleotide and also for investigating triple-helical structures, such as H-DNA, which could play an important role in the control of gene expression in vivo.

Effect of nucleoside analogs and non-nucleoside inhibitors of HIV-1 reverse transcriptase on cell-free virions

Reverse transcription takes place in the cytoplasm of infected cells, although it has been demonstrated that retroviruses can also initiate reverse transcription prior to infection of target cells. In addition to partial reverse transcripts, full-length proviral molecules have been detected in the plasma and seminal fluid of HIV-1 seropositive patients. Intravirion endogenous reverse transcription appears to be directly correlated with an increased level of infectivity. Therefore, the ability of an inhibitor to reach and inhibit the replication complex in the core of the free-virion may constitute an important part of its capacity to suppress viral infection. In this work we tested the ability of some reverse transcriptase inhibitors to decrease viral infectivity in pretreated highly purified virions. Our results showed that Curie pyridinone [Dollé et al. (1995), J Med Chem 38: 4,679-4,686], a non nucleoside RT inhibitor, strongly inhibited the infectivity of extracellular HIV-1 particles. Other non nucleoside inhibitors (TIBO R82913, HEPT, nevirapine) tested in these conditions were unable to do so. Our data indicate that the effect of Curie pyridinone on intact virions may be related to its capacity to tightly bind the target RT. This approach may lead to the design and synthesis of new drugs able to interact with the retroviral enzyme inside the viral core.

A pharmacokinetic and pharmacodynamic study of artesunate for vivax malaria

To investigate the pharmacokinetic and pharmacodynamic properties of artesunate (ARTS) and its active metabolite dihydroartemisinin (DHA) in Plasmodium vivax infections, 12 male Vietnamese adults with slide-positive vivax malaria received either intravenous ARTS (120 mg; group 1) or oral ARTS (100 mg; group 2) with the alternative preparation given 8 hr later in a randomized, open, cross-over study. Following intravenous injection, ARTS had a peak plasma drug concentration (Cmax) of 35.6 microM (13.7 mg/L), an elimination half-life (t1/2) of 2.2 min, a clearance (CL) of 3.0 L/hr/kg, and a volume of distribution (V) of 0.16 L/kg. Dihydroartemisinin had a Cmax of 7.7 microM (2.2 mg/L), a tmax of 8 min, a t1/2 of 37 min, an apparent CL of 1.1 L/hr/kg, and an apparent V of 0.9 L/kg. Following oral ARTS, the mean relative bioavailability of DHA was 85%, the Cmax was 3.0 microM (0.85 mg/L), the tmax was 75 min, and t1/2 was 40 min. The mean time to 50% reduction in the parasite count (PCT50) and median fever clearance time were 3 hr and 16 hr, respectively. Following intravenous ARTS (group 1), the PCT50 for total parasites, rings, trophozoites, and gametocytes was 3.3 hr, 3.2 hr, 4.0 hr, and 3.6 hr, respectively. This study confirms that ARTS is effective against P. vivax, with rapid clearance of sexual and asexual forms of the parasite. Artesunate is a suitable initial treatment for vivax malaria, or when the plasmodial species cannot be reliably identified.

Synthesis, properties and biological evaluation of substituted furo[3,2-e] and pyrano[3,2-e]pyrido[4,3-b]indoles

Furo[3,2-e]- and pyrano[3,2-e]pyrido[4,3-b] indoles were synthesized from 1,4,5-trisubstituted 8-hydroxy-5H-pyrido[4,3-b]indoles. The intermediates, 10-chloro-6H-furo[3,2-e]pyrido[4,3-b]indole (11), 10-chloro-2,6-dihydro-1H-furo[3,2-e]pyrido-[4,3-b]indole (10) and 11-chloro-2,3-dihydro-3H,7H-pyrano[3,2-e]pyrido[4,3-b]indole (15), were substituted by diamines under thermal conditions (180 degrees C). In contrast, 11-chloro-3H,7H-pyrano[3,2-e]pyrido[4,3-b]indole (14), 9-allyl-1-chloro-4,5-dimethyl-5H-pyrido[4,3-b]indole (9a) and 8-propargyloxy-4,5-dimethyl-5H-pyrido[4,3-b]indole (8) led mainly to 1-aminosubstituted 8-hydroxy-5H-pyrido[4,3-b]indole derivatives resulting from an unexpected C3 unit elimination. When examined in three tumour cell lines (L1210 leukaemia, the B16 melanoma and the MCF7 breast adenocarcinoma) the new amino substituted furo[3,2-e]-, dihydrofuro[3,2-e]- and dihydropyrano[3,2-e]-pyrido[4,3-b]indole derivatives revealed cytotoxic properties, especially important for the 2,6-dihydro-1H-furo[3,2-e]pyrido[4,3-b]indole series. The most active compound (12b) significantly inhibits both DNA topoisomerases I and II, and is as potent as Adriamycin at inhibiting cell proliferation and inducing a massive accumulation of L1210 cells in the G2 + M phase of the cell cycle. However, 12b was less active than Adriamycin when tested in vivo against P388 leukaemia or the B16 melanoma tumour models.

1-Amino-substituted 8-hydroxy-4,5-dimethyl-5H-pyrido[4,3-b]indoles with propyl- or methyl substituents at the 9-, and 7,9-positions: synthesis and biological evaluation

The title compounds were synthesized in 9-10 steps in order to compare their cytotoxic properties to that for 1-(3-dimethylaminopropyl)-amino-4,5-dimethyl- 8-hydroxy-5H-pyrido[4,3-b]indole. Whereas the latter is a potent cytotoxic agent, displaying significant antitumour activity, the corresponding 9-propyl (and 7,9-dimethyl) derivatives were found to be > 10-fold less cytotoxic.

Cancer incidence in Ho Chi Minh City, Viet Nam, 1995-1996

The results from the population-based cancer registry for the city of Ho Chi Minh in 1995-1996 represent the first information on the incidence of cancer in southern Viet Nam. A total of 4,080 cancer cases in males and 4,338 in females were registered, corresponding to age-standardized incidence rates (ASRs) of 130.9 per 100,000 in men and 100.7 per 100,000 in women. As elsewhere in South East Asia, the principal cancer of men was liver cancer (ASR 25.3), with moderately high rates of lung cancer (ASR 24.6) and stomach cancer (ASR 16.5); cancer of the penis, reportedly very common in early case series from Viet Nam, is now rarely seen. In women, cervical cancer was the dominant malignancy (ASR 26.0) followed by breast cancer (ASR 12.2) and stomach cancer (ASR 7.5). Although there may be some under-registration in these early years of operation, the recorded rates of cervical cancer and liver cancer are already high and suggest that southern Viet Nam would benefit from an effective cervical cancer screening programme, as well as efforts to interrupt the transmission of hepatitis B virus to reduce liver cancer incidence and effective anti-smoking programs.

Triple helices formed at oligopyrimidine*oligopurine sequences with base pair inversions: effect of a triplex-specific ligand on stability and selectivity

Oligonucleotide-directed triple helix formation is mostly restricted to oligopyrimidine*oligopurine sequences of double helical DNA. An interruption of one or two pyrimidines in the oligopurine target strand leads to a strong triplex destabilisation. We have investigated the effect of nucleotide analogues introduced in the third strand at the site opposite the base pair inversion(s). We show that a 3-nitropyrrole derivative (M) discriminates G*C from C*G, A*T and T*A in the presence of a triplex-specific ligand (a benzo[e]pyridoindole derivative, BePI). N6-methoxy-2,6-diaminopurine (K) binds to an A*T base pair better than a T*A, G*C or C*G base pair. Some discrimination is still observed in the presence of BePI and triplex stability is markedly increased. These findings should help in designing BePI-oligonucleotide conjugates to extend the range of DNA sequences available for triplex formation.

Rational design of a triple helix-specific intercalating ligand

DNA triple helices offer new perspectives toward oligonucleotide-directed gene regulation. However, the poor stability of some of these structures might limit their use under physiological conditions. Specific ligands can intercalate into DNA triple helices and stabilize them. Molecular modeling and thermal denaturation experiments suggest that benzo[f]pyrido[3, 4-b]quinoxaline derivatives intercalate into triple helices by stacking preferentially with the Hoogsteen-paired bases. Based on this model, it was predicted that a benzo[f]quino[3,4-b]quinoxaline derivative, which possesses an additional aromatic ring, could engage additional stacking interactions with the pyrimidine strand of the Watson-Crick double helix upon binding of this pentacyclic ligand to a triplex structure. This compound was synthesized. Thermal denaturation experiments and inhibition of restriction enzyme cleavage show that this new compound can indeed stabilize triple helices with great efficiency and specificity and/or induce triple helix formation under physiological conditions.

Complementary advantages of fluorescence and SIMS microscopies in the study of cellular localization of two new antitumor drugs

Low light level fluorescence microscopy studies have been carried out on MCF7-P human mammary tumor cells to localize the intracellular distribution of two new anticancer drugs, Pazelliptine and Intoplicine, which are currently under clinical evaluation. These two molecules are thought to act at the nuclear level, through DNA topoisomerase interactions. Because fluorescence of these compounds appears strongly quenched by intercalation in double strand DNA, secondary ion mass spectrometry (SIMS) imaging was used to check the presence of the drugs in the nuclear compartment. In spite of chemical structure similitudes, pazelliptine and intoplicine appear to be distributed in quite different ways within the cells. Incubation for 1 and 24 hours also allowed us to bring to light strong differences in the distribution kinetics. Pazelliptine quickly enters into the nucleoli but is no longer present in the nucleus after 24 hours incubation. Intoplicine was not detected by fluorescence in the nucleus, however SIMS microscopy allowed us to show its accumulation within this cellular compartment as a function of time of exposure. This study shows the complementarity of fluorescence and SIMS microscopies.

Conjugates of oligonucleotides with triplex-specific intercalating agents. Stabilization of triple-helical DNA in the promoter region of the gene for the alpha-subunit of interleukin 2 (IL-2R alpha)

The stabilization of triple-helical DNA under physiological conditions is an important goal for the control of gene expression using the antigen strategy, an approach whereby an oligonucleotide binds to the major groove of double-helical DNA to fom a triple helix. To this end, triplex-specific intercalators, namely benzopyridoindole (BPI) and benzopyridoquinoxaline (BPQ) derivatives, have been conjugated to the 5' end or to an internucleotide position of a 15-mer oligonucleotide. These conjugates were then tested, using thermal denaturation experiments, for their ability to form and stabilize a triple-helical structure involving a 42-mer duplex target. All of the conjugates were found to do so. The B[h]PQ derivatives stabilized particularly well when attached to the 5' end with a delta Tm of 15 degrees C and -delta delta G degrees 37 of 3.4 kcal mol-1 (pH 6.9, 140 mM KCI, 15 mM sodium cacodylate, 2 mM MgCl2, 0.8 mM spermine). Though most of the derivatives when attached to the internucleotide position were not able to stabilize triple-helical DNA as well as when attached to the 5' end, one B[f]PQ derivative with an internucleotide attachment did so, with a delta Tm of 13 degrees C and -delta delta G degrees 37 of 2.8 kcal mol-1. To a lesser degree, these conjugates were also able to stabilize duplex structures with single-stranded targets. Results were compared to the stabilization obtained with acridine conjugates as well as to a similar study performed with a different sequence.

Ligand-induced formation of triple helices with antiparallel third strands containing G and T

We have examined the effects of benzopyridoindole derivatives on triple helices with antiparallel third strands. Absorption spectroscopy, footprinting, and gel retardation experiments demonstrate that a benzopyridoindole derivative (BePI) is able to induce formation of a triple helix with an antiparallel (G, T)-containing third strand, which does not form in the absence of this ligand. This triple-helical complex is very stable with a half-dissociation temperature as high as 51 degrees C, and its formation is pH independent. Antiparallel oligonucleotides containing thymine and guanine bind strongly to double-helical DNA under physiological conditions in the presence of only 0.5 microM BePI. Formation of a BePI-stabilized triple helix strongly inhibits cleavage of the target duplex by DNase I.

Stabilization of triple helical DNA by a benzopyridoquinoxaline intercalator

Biophysical, footprinting, and chemical probing experiments are described which characterize the triple helix-stabilizing effects of a benzo[f]pyridoquinoxaline derivative BfPQ-4,3 structurally related to the previously reported benzo[f]pyridoindole compound BePI [Mergny et al. (1992) Science 256, 1681-1684]. Two parallel triple helix model systems have been investigated; one in which the third strand matched perfectly a 27 base pair purine-pyrimidine motif in target DNA and another in which the third strand was one nucleotide longer, i.e., a 28-mer. In the latter system, the pairing of the (Y)28 third strand to the (Y.R)27 target induces the formation of a bulge containing at least one unpaired base, which can be evidenced by chemical probing experiments with osmium tetroxide. BPQ, which uinwinds a duplex DNA by 17 degrees as judged by viscometric experiments and otherwise behaves as a typical nonspecific intercalculating drug, promotes the formation of Y.R.Y parallel triple helix containing both T.A.T and C.G.C+ triplets. Both DNase I and MPE.FeII footprinting experiments concur that triplex formation with the target (Y.R)27 sequence can be detected in the presence of BPQ at about 10-fold lower oligonucleotide concentrations than are required to produce an equivalent footprint in the absence of the drug. In addition, BPQ will promote binding to the polypurine-polypyrimidine target sequence by the longer mismatched oligonucleotide, providing significant stabilization of the parallel bulge-containing(Y.R)27,(Y)28 triplex with nearly the same efficiency as the bulge-free (Y.R)27.(Y)28 triplex. Thus in vivo BPQ might enhance the formation of both undesired and desired DNA triplexes. By performing an MPE*FeII probing reaction with a 5'-32 P-labeled oligonucleotide third strand, we have obtained evidence that BPQ is actually bound to the triplex region and may distort in a sequence-specific fashion.

Ligand-induced formation of hoogsteen-paired parallel DNA

INTRODUCTION

Based on molecular modeling studies, a model has been proposed for intercalation of triple-helix-specific ligands (benzopyridoindole (BPI) derivatives) into triple helices, in which the intercalating compounds interact mainly with the Hoogsteen-paired strands of the triple helix. We set out to test this model experimentally using DNA duplexes capable of forming parallel Hoogsteen base-paired structures.

RESULTS

We have investigated the possible formation of a parallel DNA structure involving Hoogsteen hydrogen bonds by thermal denaturation, FTIR spectroscopy and gel-shift experiments. We show that BPI derivatives bind to Hoogsteen base-paired duplexes and stabilize them. The compounds induce a reorganization from a non-perfectly matched antiparallel Watson- Crick duplex into a perfectly matched parallel Hoogsteen-paired duplex.

CONCLUSIONS

These results suggest that preferential intercalation of BPI derivatives in triple helices is due to their ability to interact specifically with the Hoogsteen-paired bases. The results are consistent with a model proposed on the basis of molecular modeling studies using energy minimization, and they open a new field of investigations regarding the biological relevance of Hoogsteen base-pairing.

A new series of pyridinone derivatives as potent non-nucleoside human immunodeficiency virus type 1 specific reverse transcriptase inhibitors

4-(Arylthio)-pyridin-2(1H)-ones variously substituted in their 3-, 5-, and 6-positions have been synthesized as a new series of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT)-pyridinone hybrid molecules. Biological studies revealed that some of them show potent HIV-1 specific reverse transcriptase inhibitory properties. Compounds 16 and 7c, the most active ones, inhibit the replication of HIV-1 at 3 and 6 nM, respectively.

Synthesis and biological evaluation of amino-substituted benzo[f]pyrido[4,3-b] and pyrido[3,4-b]quinoxalines: a new class of antineoplastic agents

In order to study the structure-activity relationships in the series of new intercalating polycyclic agents, 1-amino-substituted pyrido[3,4-b]quinoxalines, benzo[f]pyrido[4,3-b]quinoxaline derivatives bearing a dibasic side chain and their benzo[f]pyrido[3,4-b] isomers have been synthesized. Biological evaluation was carried out for topoisomerase I and II inhibition, and for in vitro and in vivo antitumor properties in several models. Results demonstrate that appropriately substituted benzo[f]pyrido[4,3-b]quinoxaline derivatives are inhibitors of topoisomerase I and II, and have significant antitumor properties in various experimental models. In addition, the most active compounds appear to be minimally recognized by tumor cells expressing the multidrug resistance phenotype.

Molecular interactions of DNA-topoisomerase I and II inhibitor with DNA and topoisomerases and in ternary complexes: binding modes and biological effects for intoplicine derivatives

Molecular interactions of intoplicine, dual DNA-topoisomerases (Topo) I and II inhibitor, with topoisomerases, plasmid DNA, in ternary cleavable complexes with enzymes and plasmid DNA, and in the reversed cleavable complexes were examined by means of surface-enhanced Raman scattering (SERS) and CD spectroscopy and by biochemical techniques. Detailed spectral analysis of intoplicine derivatives allowed us to assign SERS vibrational modes of chromophores and to propose the models for these complexes. Intoplicine was found to be able to interact specifically with the Topo II alone, but with Topo I only when in the presence of DNA. It shows at least two modes of binding to the DNA: the first was found to be dominant for its derivative 1c (most potent Topo I inhibitor), and the second was dominant for derivative 2a (most potent Topo II inhibitor). The possibility of forming these two types of complexes simultaneously is suggested to be one of the main factors enabling the drug to be a dual Topo I and Topo II inhibitor. The "deep intercalation mode" of the drug from the DNA minor groove with the long axis of the chromophore oriented roughly parallel to the dyad axis has been suggested to be responsible for induction of distortions of the DNA structure by the intercalating drug. Being involved in the formation of Topo I-mediated cleavable ternary complex, the molecules participating in the deep intercalation mode within the DNA do not change their molecular interactions as compared with their complex with the DNA alone. The stabilization of the Topo I-mediated cleavable complex was shown to be followed by the local denaturation of DNA in the AT-rich regions of the helix. When the ternary cleavable complex was reversed, the drug was shown to be in the complex with the plasmid. The "outside binding mode" from the DNA major groove via the hydroxyl group of the A-ring of the chromophore has been suggested to be responsible for Topo II inhibition. These molecules did not induce significant distortions of the DNA structure. Being involved in the formation of Topo II-mediated cleavable ternary complex, the drug changed its molecular interactions as compared with the complex with DNA alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Intoplicine (RP 60475) and its derivatives, a new class of antitumor agents inhibiting both topoisomerase I and II activities

Intoplicine (RP 60475, NSC 645008) is an antitumor derivative in the 7H-benzo[e]pyrido[4,3-b]indole series which is now being tested in clinical trials. Intoplicine strongly binds DNA (KA = 2 x 10(5) M-1) and thereby increases the length of linear DNA. These properties are consistent with DNA unwinding by intoplicine. Intoplicine was found to be a dual topoisomerase I and II inhibitor, with DNA sites of enzyme inhibition being different for these two enzymes. In this study, 22 analogues of intoplicine were evaluated for their effects on topoisomerase I- and II-mediated DNA cleavage reactions by using enzymes purified from calf thymus. Site-specific DNA cleavage mediated by topoisomerase I was observed with 7H-benzo[e]pyrido[4,3-b]indole derivatives but not with 11H-benzo[g]-pyrido[4,3-b]indole derivatives. Site-specific DNA cleavage mediated by topoisomerase II occurred with derivatives having hydroxyl groups at the 3-position on the 7H-benzo[e]pyrido[4,3-b]indole ring or at the 4-position on the 11H-benzo[g]pyrido[4,3-b]indole ring. Study of the relationships between the in vivo antitumor activity on P388 leukemia and the topoisomerase I- and/or II-mediated DNA cleavage activity revealed that the most highly active antitumor compounds possessed both topoisomerase I-and II-inhibitory properties. Compounds selectively inhibiting either topoisomerase I or II were less active. These results suggest that dual topoisomerase I and II inhibition is critical for the antitumor activity of this new series of antitumor compounds.