Search PubMed⌕ Search

Biomedical subjects

S Amin

Publications and source records attributed to S Amin.

At least 127 records · Page 7Linked to original sources
PubMed1995

Chemoprevention of colon carcinogenesis by phenylethyl-3-methylcaffeate.

Previous studies from this laboratory have established that caffeic acid esters present in propolis, a natural resin produced by honey bees, are potent inhibitors of human colon adenocarcinoma cell growth, carcinogen-induced biochemical changes, and preneoplastic lesions in the rat colon. The present study was designed to investigate the chemopreventive action of dietary phenylethyl-3-methylcaffeate (PEMC) on azoxymethane-induced colon carcinogenesis and to examine the modulating effect of PEMC on phosphatidylinositol-specific phospholipase C (PI-PLC), phospholipase A2, lipoxygenase (LOX), and cyclooxygenase activities in the colonic mucosa and tumor tissues in male F344 rats. At 5 weeks of age, groups of rats were fed the control (modified AIN-76A) diet, or a diet containing 750 ppm of PEMC. At 7 weeks of age, all animals except those in the vehicle (normal saline)-treated groups were given 2 weekly s.c. injections of azoxymethane at a dose rate of 15 mg/kg body weight/week. All groups were maintained on their respective dietary regimen until the termination of the experiment 52 weeks after the carcinogen treatment. Colonic tumors were evaluated histopathologically. Both colonic mucosa and tumors were analyzed for PI-PLC, phospholipase A2, cyclooxygenase, and LOX activities. The results indicate that dietary administration of PEMC significantly inhibited the incidence and multiplicity of invasive, noninvasive, and total (invasive plus noninvasive) adenocarcinomas of the colon (P < 0.05-0.004). Dietary PEMC also suppressed the colon tumor volume by 43% compared to the control diet. Animals fed the PEMC diet showed significantly decreased activities of colonic mucosal and tumor PI-PLC (about 50%), but PEMC diet had no effect on phospholipase A2. The production of 5(S)-, 8(S)-, 12(S)-, and 15(S)-hydroxyeicosatetraenoic acids via the LOX pathway from arachidonic acid was reduced in colonic mucosa and tumors (30-60%) of animals fed the PEMC diet as compared to control diet. PEMC had no effect on the formation of colonic mucosal cyclooxygenase metabolites but inhibited the formation in colonic tumors by 15-30%. The precise mechanism by which PEMC inhibits colon tumorigenesis remains to be elucidated. It is likely that the chemopreventive action may be related, at least in part, to the modulation of PI-PLC-dependent signal transduction and LOX-mediated arachidonic acid metabolism.

Animals↗
PubMed1995

Red cell alloantibody development associated with heart and lung transplantation.

The development and persistence of clinically significant red cell alloantibodies were studied in 1132 patients who underwent a heart and/or lung transplant at Harefield Hospital. Clinically significant antibodies were detected in 15 patients (1.3%) preoperatively and appeared in a further 15 (2.1%) of 704 patients followed up 1-404 weeks after surgery. Anti-D developed in only 1 of 52 D-negative recipients of a D-positive donor graft and in only 2 of 6 D-negative patients who were transfused with between 6 and 32 units of D-positive red cells. Most antibodies that appeared after transplantation remained detectable for only a few weeks. Antibodies detected preoperatively that reacted only with papain-treated cells became persistently undetectable in 4 patients who were transfused with red cells expressing the corresponding antigen specificity. By contrast, antibodies detected preoperatively by indirect antiglobulin test were still detectable after periods of up to 260 weeks in 4 patients who received only antigen-negative red cells. Immunosuppressive therapy appeared to profoundly affect the natural history of red cell alloantibody production in these patients. The underlying mechanisms warrant further study.

ABO Blood-Group System↗
PubMed1995

Solution conformation of the (-)-trans-anti-5-methylchrysene-dG adduct opposite dC in a DNA duplex: DNA bending associated with wedging of the methyl group of 5-methylchrysene to the 3'-side of the modification site.

This paper reports on NMR-molecular mechanics structural studies of the (-)-trans-anti-[MC]dG adduct positioned opposite dC in the sequence context of the d(C1-C2-A3-T4-C5-[MC]G6-C7-T8-A9-C10-C11).d(G12-G13-T14++ +-A15-G16-C17-G18- A19-T20-G21-G22) duplex [designated (-)-trans-anti-[MC]dG.dC 11-mer duplex]. This adduct is derived from the trans addition at C4 of (-)-anti-1(S),2(R)-dihydroxy-3(R),4(S)-epoxy-1,2,3,4-tetrahydro-5-met hylchrysen e [(-)-anti-5-MeCDE] to the N2 position of dG6 in this duplex sequence. The 5-methyl group is located adjacent to the MC(C4) binding site, with these groups juxtaposed in a sterically crowded bay region in the adduct duplex. The 5-methylchrysenyl and the nucleic acid exchangeable and nonexchangeable protons were assigned following analysis of two-dimensional NMR data sets in H2O and D2O buffer solution. The solution structure of the (-)-trans-anti-[MC]dG.dC 11-mer duplex has been determined by incorporating DNA-DNA and carcinogen-DNA proton-proton distances defined by lower and upper bounds deduced from NOESY data sets as restraints in molecular mechanics computations in torsion angle space. The results establish that the [MC]dG6.dC17 base pair and flanking dC5.dG18 and dC7.dG16 base pairs retain Watson-Crick alignments upon adduct formation. The aromatic chrysenyl ring is positioned in the minor groove of a right-handed B-DNA helix and stacks predominantly over the sugar of the dC17 residue across from it on the unmodified complementary strand. The chrysenyl ring points toward the 3'-end of the modified strand with its 5-methyl group inserting between the modified [MC]dG6.dC17 and dC7.dG16 base pairs. The adduct duplex bends by approximately 47 degrees as a result of the wedged insertion of the 5-methyl group from the minor groove face of the duplex. The solution structure of the (-)-trans-anti-[MC] dG.dC 11-mer duplex is compared with that of the corresponding (-)-trans-anti-[BP]dG.dC 11-mer [De los Santos et al. (1992) Biochemistry 31, 5245-5252] in which the [BP]dG adduct is derived from the binding of (-)-anti-BPDE [7(S),8(R)-dihydroxy-9(R),10(S)-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene] to the N2 position in the same DNA sequence context. Although the solution structures of the (-)-trans-anti-stereoisomers of 5-methylchrysenyl-dG and benzo[a]pyrenyl-dG adducts opposite dC exhibit many features in common with each other, the [MC]dG adduct which contains a bay region methyl group bends the DNA helix to a greater extent than in the corresponding [BP]dG adduct, which lacks a bay region methyl group.(ABSTRACT TRUNCATED AT 400 WORDS)

Chrysenes↗
PubMed1995

Solution conformation of the (-)-trans-anti-benzo[c]phenanthrene-dA ([BPh]dA) adduct opposite dT in a DNA duplex: intercalation of the covalently attached benzo[c]phenanthrenyl ring to the 3'-side of the adduct site and comparison with the (+)-trans-anti-[BPh]dA opposite dT stereoisomer.

This paper reports on NMR-molecular mechanics structural studies of the (-)- trans-anti-benzo[c]phenanthrene-dA adduct positioned opposite dT in the sequence context of the d(C1-T2-C3-T4-C5-[BPh]A6-C7-T8-T9-C10-C11).d(G12- G13-A14-A15-G16-T17-G18-A19-G20-A21- G22) duplex (designated as the (-)-trans-anti-[BPh]dA.dT 11-mer duplex). This adduct is derived from the covalent binding of (-)-1,2-dihydroxy-3,4-epoxy-1,2,3,4-tetrahydro-benzo[c]phenanthrene [(-)-anti-BPhDE] to N6 of dA6 in this duplex sequence. The benzo[c]phenanthrenyl and nucleic acid exchangeable and nonexchangeable protons were assigned in the predominant conformation following analysis of two-dimensional NMR data sets in H2O and D2O buffer solution. The solution structure of the (-)-trans-anti-[BPh]dA.dT 11-mer duplex has been determined by incorporating intramolecular and carcinogen-DNA proton-proton distances defined by lower and upper bounds deduced from NOESY data sets as restraints in molecular mechanics computations in torsion angle space. The results show that the [BPh]dA6.dT17 base pair propeller twists and buckles slightly to permit the covalently attached benzo[c]phenanthrenyl ring to intercalate between the [BPh]dA6.dT17 and dC7.dG16 base pairs to the 3'-side of the [BPh]dA6 lesion site without disrupting the Watson-Crick hydrogen bond alignments in the modified duplex. The strain in the highly sterically hindered fjord region of the benzo[c]phenanthrenyl moiety is relieved by the propeller-like nonplanar geometry of the aromatic phenanthrenyl ring system, which stacks predominantly with the dG16 and dT17 bases on the unmodified strand. The benzylic ring adopts a distorted half-chair form, in which the H1 and H2 protons are pseudo-diequatorial and the H3 and H4 protons are pseudodiaxial. The current observation that the (-)-trans-anti-[BPh]dA positioned opposite dT intercalates to the 3'-side of the intact modified base pair contrasts with our previous demonstration that the stereoisomeric (+)-trans-anti-[BPh]dA adduct positioned opposite dT intercalates to the 5'-side of the intact modified base pair [Cosman, M., et al. (1993b) Biochemistry 32, 12488-12497]. These stereochemically induced structural differences between isomeric [BPh]dA lesions derived from the binding of chiral (+)- and (-)-anti-BPhDE enantiomers may in turn profoundly influence the interactions of the carcinogen-modified DNA with repair and replication enzymes in the cell.

Base Sequence↗
PubMed1995

Tumorigenicity in newborn mice of fjord region and other sterically hindered diol epoxides of benzo[g]chrysene, dibenzo[a,l]pyrene (dibenzo[def,p]chrysene), 4H-cyclopenta[def]chrysene and fluoranthene.

Diol epoxides of benzo[g]chrysene, dibenzo[a,l]pyrene (dibenzo[def,p]chrysene), 4H-cyclopenta[def]chrysene and fluoranthene were tested for tumorigenicity in newborn mice. The compounds tested were racemic trans-11,12-dihydroxy-anti-13,14-epoxy-11,12,13, 14-tetrahydrobenzo[g]-chrysene (BgCDE), trans-11, 12-dihydroxy-anti-13,14-epoxy-11,12,13,14-tetrahydrodibenzo [a,l]pyrene (DB[a,l]PDE), trans-1,2-dihydroxy-anti-3, 3a-epoxy,1,2,3,3a-tetrahydro-4H-cyclopenta[def]chrysene (C[def]C-1,3a-DE), trans-6,7-dihydroxy-anti-8,9-epoxy-10b,1, 2,3-tetrahydrofluoranthene (FDE). BgCDE and DB[a,l]PDE are fjord region diol epoxides and their tumorigenic activities were compared to those of trans-3,4-dihydroxy-anti-1, 2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (BcPDE), a fjord region diol epoxide with known high tumorigenicity and trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]-pyrene (BPDE), a highly tumorigenic bay region diol epoxide. The protocol called for testing of each compound at a total dose of 25 nmol per mouse, administered on days 1, 7 and 15 of life, with killing at age 35 weeks. BgCDE had similar activity as BcPDE for induction of lung tumors and was more active than BcPDE for induction of liver tumors in male mice. Both compounds were significantly more tumorigenic than BPDE. DB[a,l]PDE was highly toxic. All mice died within 1 week of the first dose. It was then tested in a second study using total doses of 5 and 1 nmol per mouse. Only the first dose of the intended 5 nmol total dose was given due to toxicity. The full course of doses with a total of 1 nmol per mouse was administered; DB[a,l]PDE induced a significant incidence and multiplicity of lung tumors and, in male mice, liver tumors at both doses. These results demonstrate that fjord diol epoxides are highly active tumorigens in newborn mice, with activity greater than that of the most active unsubstituted bay region diol epoxide, BPDE. C[def]C-1-3a-DE and C[def]-6-9-DE were compared to trans-1,2-dihydroxy-anti-3, 4-epoxy-1,2,3,4-tetrahydrochrysene (CDE), at a total dose of 500 nmol per mouse. FDE was also tested at this dose. The most active compound among the chrysene derivatives was C[def]C-1-3a-DE, followed by C[def]C-6-9-DE and CDE. C[def]C-1-3a-DE has a sterically constrained bay region, in which the benzylic carbon of the tri-substituted epoxide ring is part of a fused ring system. This feature is also present in FDE, which and considerable tumorigenic activity, greater than that of CDE in lung and greater than any of the chrysene derivatives in liver.(ABSTRACT TRUNCATED AT 400 WORDS)

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1995

Mammary carcinogenicity in female CD rats of a diol epoxide metabolite of fluoranthene, a commonly occurring environmental pollutant.

We examined the mammary carcinogenicity in CD rats of anti-2,3-dihydroxy-1,10b-epoxy-10b,1,2,3-tetrahydro-fluoranthene (FDE), a genotoxic metabolite of the environmental pollutant fluoranthene. FDE (2 mumol or 10 mumol) in 0.1 ml dimethyl sulfoxide (DMSO) was injected beneath each of the three left thoracic nipples of groups of 20 rats each, with 0.1 ml DMSO alone being injected under the right nipples. On the next day, the procedure was repeated for the three inguinal nipples on each side. anti-3,4-Dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]-phenanthrene (BcPDE, 2 mumol per nipple) was used as a positive control and DMSO alone as a negative control. Tumor development was assessed weekly by palpation and the experiment was terminated after 41 weeks. Eighty five percent of the rats in each of the FDE treated groups developed histologically confirmed mammary tumors, compared to 11% in the DMSO treated animals (P < 0.01). Most tumors were on the left side. The lower dose of FDE induced a significant number of adenomas while the higher dose induced significant incidences of both adenomas and adenocarcinomas compared to controls. BcPDE was a powerful mammary carcinogen, confirming our previous observation. The results of this study demonstrate the carcinogenicity of FDE to the CD rat mammary gland. Since FDE is a potentially transportable human metabolite of fluoranthene, its possible role as an etiologic factor in breast cancer deserves further study.

Animals↗
PubMed1995

Mammary carcinogenicity in female CD rats of fjord region diol epoxides of benzo[c]phenanthrene, benzo[g]chrysene and dibenzo[a,l]pyrene.

We compared the mammary carcinogenicity in female CD rats of three fjord region diol epoxides to test our hypothesis that such sterically hindered molecules would be potent carcinogens. The diol epoxides tested were racemic anti-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (BcPDE), anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrobenzo[g]chrysene (BgCDE) and anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l ]pyrene (DB[a,l]PDE). Each diol epoxide was dissolved in dimethylsulfoxide (DMSO) and injected under the six nipples on the left side of the rat, with DMSO only being injected under the nipples on the right side. The total dose of each diol epoxide was 1.2 mumol/rat and there were 20 rats/group. The experiment was terminated 41 weeks after treatment. All three diol epoxides were potent mammary carcinogens, with activity greater than previously observed for a bay region diol epoxide, anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). DB[a,l]PDE induced tumors most rapidly, followed by BcPDE and BgCDE. However, different types of tumors were induced. For induction of adenomas and adenocarcinomas, BcPDE and BgCDE had comparable potency; both were more active than DB[a,l]PDE. In contrast, for induction of sarcomas, DB[a,l]PDE was significantly more active than BcPDE and BgCDE. The results of this study support our hypothesis that sterically hindered fjord region diol epoxides are potent mammary carcinogens in the rat.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1995

Determination of stereospecificity of benzo[a]pyrene diolepoxide-DNA antisera with site-specifically modified oligonucleotides.

Antisera developed against benzo[a]pyrene diolepoxide (BPDE)-DNA adducts are sensitive tools for detection of DNA adducts in human samples. All antisera currently used for biomonitoring studies were produced against DNA or guanosine modified with racemic anti-BPDE. Using a non-competitive enzyme-linked immunosorbent assay (ELISA), Venkatachalam and Wani (Carcinogenesis, 15, 565-572, 1994) recently tested polyclonal and monoclonal (5D2) antisera for cross-reactivity against oligonucleotides containing (+)-and (-)-trans-anti-BPDE-N2-guanine or N6-adenine adducts and showed different stereospecificity for the two antisera. Because of the importance of antiserum specificity in human biomonitoring studies, we have tested several monoclonal (Mab 5D11 and 5D2) and polyclonal (Pab #29) antisera developed against racemic anti-BPDE-DNA adducts, and Mab 8E11 developed against anti-BPDE-guanosine adducts. Stereoisomeric anti-BPDE-modified oligonucleotide adducts in the sequence 5'-d(CC-AT-CG*CTACC)-3' where G* = anti-BPDE-N2-dG with (+)-trans, (-)-trans, (+)-cis and (-)-cis adduct stereochemistry at the C10 position of anti-BPDE were tested by competitive ELISA. Two structurally related 5-methylchrysene diolepoxide adducts with G* = (+)- and (-)-trans-anti-5-MeCDE-N2-dG in the same oligonucleotide were also tested. While Mab5D2 had the highest affinity for the (-)-trans-anti-BPDE-modified oligomer, Mab 5D11 and 8E11 and Pab #29 recognized the (+)-trans-anti-BPDE-modified oligomer better than the (-)-trans-anti-BPDE modified oligomer. Mab 5D11 and Pab #29 recognized racemic anti-BPDE-modified DNA adducts better than trans-anti-BPDE-modified oligonucleotides; however, Mab 8E11 showed similar sensitivity to racemic anti-BPDE-DNA adducts and (+)- and (-)-trans-anti-BPDE-modified oligomers. All antisera exhibited lower reactivities with both 5-MeCDE modified oligomers. Because of their sensitive detection of (+)-trans-anti-BPDE-dG adducts, the primary adduct produced in vivo, Mab 8E11 and 5D11 and Pab #29 are appropriate for measurement of most adducts formed in humans.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1995

Visceral leishmaniasis after cardiac surgery.

An English child developed visceral leishmaniasis (kala-azar) after cardiac surgery. Neither he nor his mother had ever been out of the UK, and his disease was probably transmitted by blood transfusion. Kala-azar should be considered in patients with unexplained fever and hepatosplenomegaly, even if there is no history of foreign travel.

Blood Transfusion↗
PubMed1995

Steel factor supports the cycling of isolated human CD34+ cells in the absence of other growth factors.

Steel factor (SF) acts synergistically with other hematopoietic growth factors to support the proliferation of progenitor cells in a variety of culture systems. To determine whether SF alone could directly stimulate proliferation of early hematopoietic progenitor cells, isolated CD34+ cells from adult bone marrow and umbilical cord blood were studied in a short-term suspension culture in serum-free medium. Numbers of CD34+ and proliferating cells were quantified by flow cytometry; proliferation was assessed by simultaneous measurement of expression of the nuclear antigen Ki67 and DNA content (propidium iodide [PI]). In the absence of growth factors, the numbers of CD34+ and cycling cells declined over 2 days. Cells cultured in the presence of SF alone maintained the number of CD34+ and cycling cells at levels equal to the starting population. Withdrawal of growth factors led to a dramatic decrease in the number of cells in G1. Compared to cells grown in the absence of growth factors, cells grown in the presence of SF had significantly higher numbers of CD34+ and cycling cells (mean fold increase = 1.3 and 2; p < 0.05 and 0.01, respectively). SF increased the numbers of cells in both G1 and later phases of the cell cycle. Addition of interleukin-3 (IL-3) to SF led to further significant increases in CD34+ and cycling cells. The effects of SF could not be attributed to inhibition of apoptosis. CD34+ cells isolated from peripheral blood (PB) from patients with chronic myelogenous leukemia (CML) displayed similar characteristics. As assessed by binding of phycoerythrin (PE)-labeled ligand and flow cytometry, c-kit was expressed on 65 +/- 6% of isolated CD34+ cells and was detected on HLA-DRlow, CD38low, and Thy1+ subsets, as well as on more mature progenitor cells. Thus, while the effects of SF are most marked in combination with other growth factors, SF appears to bind to and directly maintain the active cell-cycle characteristics of isolated CD34+ cells.

Antigens, CD↗
PubMed1994

Solution conformation of the (+)-trans-anti-[BP]dG adduct opposite a deletion site in a DNA duplex: intercalation of the covalently attached benzo[a]pyrene into the helix with base displacement of the modified deoxyguanosine into the major groove.

This paper reports on the solution structure of the (+)-trans-anti-[BP]dG adduct positioned opposite a deletion site in a DNA oligomer duplex which defines the alignment of this covalent benzo[a]pyrene-N2-deoxyguanosine stereosiomer relative to the deletion site. The combined NMR-molecular mechanics computation studies were undertaken on the (+)-trans-anti-[BP]dG adduct embedded in the d(C5-[BP]G6-C7).d(G16-G17) sequence context in a duplex containing 11 residues on the modified strand and 10 on the partner, with no base opposite the modification. The exchangeable and nonexchangeable protons of the benzo[a]pyrenyl moiety and the nucleic acid were assigned following analysis of two-dimensional NMR data sets in H2O and D2O solution. The solution conformation of the (+)-trans-anti-[BP]dG.del 11-mer duplex has been determined by incorporating intramolecular and intermolecular proton-proton distances defined by lower and upper bounds deduced from NOESY spectra as restraints in molecular mechanics computations in torsion angle space. The benzo[a]pyrene ring of [BP]dG6 is intercalated between intact Watson-Crick dC5.dG17 and dC7.dG16 base pairs with the deoxyguanosine base of [BP]dG6 displaced into the major groove. The intercalation site is wedge shaped, being narrower toward the dG16-dG17 step on the deletion-containing strand. The deoxyguanosine base of [BP]dG6 which is positioned in the major groove is inclined relative to the helix axis and stacks over the 5'-flanking dC5 residue in the solution structure. The intercalative-base displacement structure of the (+)-trans-anti-[BP]dG.del 11-mer duplex exhibits several unusually shifted proton resonances which can be readily accounted for by the ring current contribution of the deoxyguanosyl and pyrenyl rings of the [BP]dG6 adduct. This solution structure of the (+)-trans-anti-[BP]dG.del 11-mer duplex where the pyrene ring intercalates into the helix with displacement of the modified deoxyguanosine into the major groove strikingly contrasts with our previous study on the (+)-trans-anti-[BP]dG.dC 11-mer duplex [Cosman, M., et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 1914-1918] where the benzo[a]pyrene ring is positioned in the minor groove without disruption of the Watson-Crick pairing at the [BP]dG.dC modification site. Thus, generation of the deletion site following removal of the dC opposite the (+)-trans-anti-[BP]dG results in a displacement of the entire [BP]dG residue toward the major groove and intercalation of the benzo[a]pyrene ring into the helix.

Base Sequence↗
PubMed1994

Solution conformation of the (+)-cis-anti-[BP]dG adduct opposite a deletion site in a DNA duplex: intercalation of the covalently attached benzo[a]pyrene into the helix with base displacement of the modified deoxyguanosine into the minor groove.

We have applied a combined NMR-molecular mechanics approach to determine the solution structure of the (+)-cis-anti-[BP]dG adduct positioned opposite a deletion site in the sequence d(C5-[BP]G6-C7).d(G16-G17) at the DNA oligomer duplex level. Our structural studies establish that the benzo[a]pyrene ring intercalates into the helix opposite the deletion site while the modified deoxyguanosine is displaced into the minor groove with its plane parallel to the helix axis. The intercalation site is wedge-shaped with the benzo[a]pyrene ring stacked over intact flanking Watson-Crick dG.dC base pairs. The modified deoxyguanosine stacks over the minor groove face of the sugar ring of the 5'-flanking dC5 residue. The structure at the lesion site is consistent with the observed intermolecular NOEs which served as input restraints to guide the molecular mechanics calculations, and, in addition, the various stacking interactions explain the observed large ring current shifts associated with adduct formation. The solution structure of the (+)-cis-anti-[BP]dG adduct positioned opposite a deletion site reported in this study is similar to the corresponding structure of the same adduct positioned opposite dC reported previously [Cosman, M., de los Santos, C., Fiala, R., Hingerty, B. E., Luna, E., Harvey, R. G., Geacintov, N. E., Broyde, S., & Patel, D. J. (1993) Biochemistry 32, 4145-4155]. This is not surprising since the dC opposite the lesion site was looped out of the helix and it can be readily replaced by a deletion site through minor changes associated with buckling of the intercalation site. By contrast, the solution structures of the (+)-trans-anti-[BP]dG and (+)-cis-anti-[BP]dG adducts positioned opposite deletion sites in the same sequence context exhibit distinct surface topologies in the grooves of the DNA helix. Thus, even though the benzo[a]pyrene intercalates into the helix opposite the deletion site in both cases, the modified deoxyguanosine is displaced into the major groove for the (+)-trans-anti-[BP]dG adduct while it is displaced into the minor groove for the (+)-cis-anti-[BP]dG stereoisomer. The orientational differences reflect the chiral characteristics of the two [BP]-dG stereoisomeric adducts with the different alignments of the bulky DNA lesion opposite the deletion site likely to influence interactions with the cellular repair machinery.

Base Sequence↗
PubMed1994

STK-1, the human homolog of Flk-2/Flt-3, is selectively expressed in CD34+ human bone marrow cells and is involved in the proliferation of early progenitor/stem cells.

We cloned the cDNA for stem cell tyrosine kinase 1 (STK-1), the human homolog of murine Flk-2/Flt-3, from a CD34+ hematopoietic stem cell-enriched library and investigated its expression in subsets of normal human bone marrow. The cDNA encodes a protein of 993 aa with 85% identity and 92% similarity to Flk-2/Flt-3. STK-1 is a member of the type III receptor tyrosine kinase family that includes KIT (steel factor receptor), FMS (colony-stimulating factor 1R), and platelet-derived growth factor receptor. STK-1 expression in human blood and marrow is restricted to CD34+ cells, a population greatly enriched for stem/progenitor cells. Anti-STK-1 antiserum recognizes polypeptides of 160 and 130 kDa in several STK-1-expressing cell lines and in 3T3 cells transfected with a STK-1 expression vector. Antisense oligonucleotides directed against STK-1 sequences inhibited hematopoietic colony formation, most strongly in long-term bone marrow cultures. These data suggest that STK-1 may function as a growth factor receptor on hematopoietic stem and/or progenitor cells.

Amino Acid Sequence↗
PubMed1994

Potent mammary carcinogenicity in female CD rats of a fjord region diol-epoxide of benzo[c]phenanthrene compared to a bay region diol-epoxide of benzo[a]pyrene.

Two diol-epoxide metabolites of benzo[c]phenanthrene and benzo[a]pyrene, polynuclear aromatic hydrocarbons which occur in the environment, were tested for carcinogenicity by direct injection into the mammary fat pads of female CD rats. The compounds anti-3,4-dihydroxy-1,2-epoxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene (BcPDE), a fjord region diol-epoxide, and anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene, a bay region diol-epoxide, were applied at total doses of 12.2 mumol. 6-Nitrochrysene was applied at the same dose as a positive control (K. El-Bayoumy, A. Rivenson, P. Upadhyaya, Y-H. Chae, and S. S. Hecht, Cancer Res. 53: 3719-3722, 1993). The sterically hindered fjord region diol-epoxide BcPDE was a powerful mammary tumorigen and carcinogen, rapidly inducing significantly more fibroadenoma and adenocarcinoma than either of the other compounds. Anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene was a weaker mammary tumorigen than BcPDE and 6-nitrochrysene. The results of this study provide the first evidence for mammary tumorigenicity of polynuclear aromatic hydrocarbon diol-epoxides and demonstrate the potent mammary carcinogenicity of BcPDE.

Adenocarcinoma↗
PubMed1994

Contrasting incidence of ras mutations in rat mammary and mouse skin tumors induced by anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide.

Racemic anti-benzo[c]phenanthrene-3,4-diol-1,2-epoxide (anti-B[c]PhDE) is a powerful rat mammary carcinogen and is one of the most potent diol-epoxide tumorigens in mouse skin. Activation of ras genes has been proposed to be involved in tumorigenesis by this and related polynuclear aromatic hydrocarbon metabolites. Therefore, we analyzed rat mammary tumors and mouse skin tumors induced by anti-B[c]PhDE for mutations at codons 12, 13 and 61 of the Ki-ras and Ha-ras genes. No Ki-ras mutations were detected in either tumor type. In the rat mammary tumors, no Ha-ras mutations in codons 12 or 13 were observed in 25 tumors analyzed. Only one, a CAA-->CTA mutation, was detected in codon 61, of 42 tumors analyzed. These results indicate that Ki-ras and Ha-ras mutations are not involved in the induction of rat mammary tumors by anti-B[c]PhDE. Mutations in codon 61 of the Ha-ras gene were common, however, in mouse skin tumors induced by this diol-epoxide, being detected in 63% of the tumors analyzed; 90% of these mutations were CAA-->CTA. A dose-dependent difference in the occurrence of the CAA-->CTA mutations was observed; they were present in 75% of the tumors induced by a 100 nmol initiating dose of the diol-epoxide, but in only 34.5% of the tumors induced by a 400 nmol initiating dose. A CAA-->CTA mutation in codon 61 of Ha-ras was also detected in one of four acetone control tumors. In comparison with previous studies of other polynuclear aromatic hydrocarbons and their metabolites, the results suggest that the reactivity with DNA of anti-B[c]PhDE is one factor involved in the induction of A mutations in Ha-ras genes in mouse skin, but further studies are required to evaluate the significance of these mutations in mouse skin tumorigenesis.

Adenocarcinoma↗
PubMed1994

Tumor multiplicity, DNA adducts and K-ras mutation pattern of 5-methylchrysene in strain A/J mouse lung.

This study was undertaken to evaluate the carcinogenic potential of 5-methylchrysene (5-MeC) in strain A/J mouse lung and to correlate the 5-MeC-DNA adduct profile in lung tissue with the mutation spectrum in the K-ras gene of lung tumors. Strain A/J mice received a single i.p. injection of 5-MeC at doses of 10, 50, 100 and 200 mg/kg and after 24, 48 and 72 h their lungs were collected for DNA adduct analysis. Eight months later, lungs from the remaining mice were harvested and the lung tumors counted and collected for subsequent mutational analysis of the K-ras gene. 5-MeC was found to be a potent lung carcinogen in strain A/J mice, inducing more than 100 tumors/mouse at a concentration of 200 mg/kg. Six 5-MeC-DNA adducts were observed; one adduct comigrated with the standard N2-deoxyguanosine adduct of 5-MeC-diol-epoxide I [1R,2S,3S-trihydroxy-4R-(N2-deoxy-guanosyl-3'-phosphate)- 1,2,3,4-tetrahydro-5-methyl-chrysene], derived from the bay-region diol-epoxide of 5-MeC. DNAs isolated from 5-MeC-induced lung tumors were evaluated for activating mutations in the K-ras gene by polymerase chain reaction-single strand conformation polymorphism and direct DNA sequencing analysis. Mutations were detected in 44 of 49 (90%) 5-MeC-induced tumors and the mutations were GGT-->TGT (50%), GGT-->GTT (23%) and GGT-->CGT (27%) in codon 12 of the gene. These results suggest that the N2-deoxyguanosine adduct of 5-MeC-diol-epoxide I may be one of the promutagenic adducts of 5-MeC in strain A/J mouse lung.

Animals↗