Ganoderic acid Mf and S induce mitochondria mediated apoptosis in human cervical carcinoma HeLa cells

In this work, the effects of a pair of positional isomer of ganoderic acids (GAs), namely ganoderic acid Mf (GA-Mf) and ganoderic acid S (GA-S) purified from the fermented mycelia of Ganoderma lucidum, on induction of cell apoptosis and the apoptotic pathway in HeLa cells were investigated. The results demonstrate that both isomers decreased cell population growth on various human carcinoma cell lines by MTT assay, while GA-Mf had better selectivity between normal and cancer cells. The flow cytometry analysis indicated that treatment of HeLa cells with GA-S caused cell cycle arrest in the S phase, while GA-Mf caused cell cycle arrest in the G1 phase. Compared with GA-S, GA-Mf had more potent increase in the number of early and late apoptotic cells. Treatment of HeLa cells with each isomer decreased the mitochondria membrane potential and caused the release of cytochrome c from mitochondria into the cytosol. In addition, stimulation of caspase-3 and caspase-9 activity was observed. The Bax/Bcl-2 ratio was also increased in GA-treated HeLa cells. The results demonstrated that both isomers GA-Mf and GA-S induced apoptosis of human HeLa cells through a mitochondria mediated pathway, but they had the different cell cycle arrest specificity. The findings will be helpful to the development of useful cancer chemopreventive compounds from G. lucidum.     

Correlation between the affinity of flavonoids binding to the cytosolic site of Leishmania tropica multidrug transporter and their efficiency to revert parasite resistance to daunomycin

The C-terminal nucleotide-binding domain (NBD2) of a P-glycoprotein-like transporter, encoded by the ltrmdr1 gene in Leishmania tropica and involved in parasite multidrug resistance (MDR), was overexpressed in Escherichia coli as a hexahistidine tagged protein and purified. The L. tropica recombinant domain efficiently bound fluorescent derivatives of ATP, the hydrophobic steroid analogue RU 486, and different classes of flavonoids with the following efficiency: flavone > flavanone > isoflavone > glucorhamnosyl-flavone > chromone. The affinity for flavones was dependent on the presence of hydroxyl groups at positions 5 and 3 and was further increased by a hydrophobic 1,1-dimethylallyl substituent at position 8. When flow cytometry was used to measure daunomycin accumulation in a MDR L. tropica line, a reversing effect was observed with flavones such as dimethylallyl-kaempferide at low concentration or apigenin at higher concentration, but neither with the glucorhamnosyl derivative rutin nor with the isoflavone genistein. The in vivo reversing effect of dimethylallyl-kaempferide was correlated to a high inhibition of MDR cell growth in the presence of daunomycin. The results suggest that flavone inhibition of both daunomycin efflux and parasite growth in the presence of the drug correlates to direct binding of the compound to cytosolic domain of the P-glycoprotein-like transporter.     

Inhibition of the thermally driven B to Z transition by intercalating drugs

Poly(dG-m5dC) in phosphate buffer containing 50 mM NaCl and Mg2+ will undergo a reversible thermally driven conversion from the B to the left-handed Z conformation. The temperature at the midpoint of the thermally driven B to Z transition (denoted Tz) is dependent upon the total Mg2+ concentration, with [d(1/Tz)]/(d ln [Mg]) = 0.0134 K-1. The Mg2+ concentration at the midpoint of the equilibrium B to Z transition curve, denoted [Mg]1/2, is dependent on temperature, with (d ln [Mg]1/2)/(d ln T) = -1.02. Binding of the anticancer drug daunomycin to the polymer results in a pronounced increase in Tz, dependent on the molar ratio of added drug. Tz is increased by 71.9 degrees C with nearly saturating amounts of drug bound. Transition profiles are biphasic at less than saturating amounts of bound drug. By experiments monitoring such biphasic curves at a visible wavelength sensitive to the binding of daunomycin, it may be demonstrated that no drug is released until the later phase of the transition. These results are analogous to the effects of intercalating drugs on the thermal denaturation of DNA and indicate that drug molecules preferentially interact with B-form DNA and are redistributed to regions in the B conformation over the course of the transition. Comparative studies show that some intercalators stabilize right-handed DNA more effectively than others. At similar initial binding ratios, the following order, from most to least effective, was experimentally observed: actinomycin greater than daunomycin greater than ethidium greater than proflavin.     

Interaction of daunomycin antibiotic with histone H(1): ultraviolet spectroscopy and equilibrium dialysis studies

Using ultraviolet spectroscopy and equilibrium dialysis techniques, we have investigated the interaction of anticancer drug, daunomycin with calf thymus histone H(1) chromosomal protein in 20 mM phosphate buffer, pH 7.0, 1 mM EDTA at room temperature. The UV spectroscopy results show that daunomycin (5.0-100 microM) decreases the absorbance of histone H(1) at 210-230 nm and induces hypochromicity in the absorption spectrum of the protein. The equilibrium dialysis data show that daunomycin binds to histone H(1) and the binding process is positive cooperative with two binding sites as Scatchard plot and Hill coefficient confirm it. The results suggest that daunomycin binds to histone H(1) and changes its conformation.     

Immunotargeting of daunomycin to localized and metastatic human colon adenocarcinoma in athymic mice

Summary A monoclonal antibody (designated SF25), which recognizes a protein antigen expressed on a large number of human colon carcinomas, was used for drug targeting. Daunomycin-antibody conjugates were prepared by two previously described procedures. In one, the drug was bound to the antibody through a spacer of small molecular mass (cis-aconitic acid), while in the other a dextran bridge served as the link between drug and antibody. High substitution rates of drug to antibody were obtained using the latter binding procedure. Both conjugates were tested in vitro against two human colon carcinoma cell lines, LS180 and KM-12. The efficacy of a daunomycin-dextran-SF25 antibody conjugate was tested against colon carcinoma LS180 tumors transplanted at different sites into athymic mice. The specific conjugate was significantly more inhibitory to a subcutaneous tumor growth than its components or their mixture. SF25 antibody alone showed antitumoral effects against all three forms of transplanted tumor tested, namely, local, metastatic or intrahepatic, whereas daunomycin, on its own, was effective only against the subcutaneous tumor. Binding of daunomycin to dextran partially improved its inhibitory activity against the metastatic tumor. The conjugate, daunomycin-dextran-SF25 antibody reduced the number of metastatic foci, increased the survival rate and delayed death. Yet against lymph node metastases it was not significantly better than a mixture of both constituents. However, results obtained with an intrahepatic tumor, a model that mimics the natural progression of the disease, resembled those described with the subcutaneous tumor. Daunomycin-dextran-SF25 antibody was significantly more effective than all components separately and than a mixture of drug and antibody, provided a highly drug-substituted conjugate was used.     

Influence of template inactivators on the binding of DNA polymerase to DNA

The agents daunomycin, ethidium bromide, distamycin A and cytochrome c inhibit DNA dependent DNA polymerase I (E. coli) reaction competitively to DNA. The influence of these template inactivators on the binding of DNA polymerase to native as well as denatured DNA has been determined by affinity chromatography. Cytochrome c blocks the binding of the enzyme to double-stranded and to single-stranded DNA Sepharose. In contrast to these results daunomycin, ethidium bromide or distamycin A reduce the binding affinity only with denatured DNA Sepharose as matrix. These data are discussed with respect to the modification by template inactivators of the affinity of DNA to the different binding sites of the DNA polymerase.     

Synergistic in vitro and in vivo anti-tumor effect of daunomycin-anti-96-kDa melanoma-associated antigen monoclonal antibody CL 207 conjugate and recombinant IFN-gamma

The mAb CL 207 recognizes a 96-kDa melanoma-associated Ag. The latter is not modulated by antibody but is highly susceptible to induction by immune IFN-gamma on human carcinoma and melanoma cells. The mAb CL 207 does not mediate C- and cell-dependent lysis of human carcinoma and melanoma cells. Conjugation of daunomycin with mAb CL 207 causes a slight reduction of its immunoreactivity and affinity but does not affect its serologic specificity or the toxicity of daunomycin. In combination with IFN-gamma, the daunomycin-mAb CL 207 conjugate displays a selective in vitro and in vivo toxic effect on tumor cells that express the 96-kDa MAA. The synergistic effect of IFN-gamma and daunomycin-mAb CL 207 conjugate is specific. The in vivo toxicity is influenced by the interval between injection of human tumor cells into nude mice and that of IFN-gamma and daunomycin-mAb CL 207 conjugate. The present results suggest that the 96-kDa melanoma-associated Ag may be a useful model to investigate the combined use of IFN-gamma and mAb for the selective destruction of tumor cells.     

Effects of cholesterol and enantiomeric cholesterol on P-glycoprotein localization and function in low-density membrane domains

Multidrug resistance P-glycoprotein (Pgp) has been reported to localize in low-density, cholesterol-enriched membranes. However, effects of low-density membrane domains on function of Pgp remain unexplored in whole cell systems. In cells that express modest levels of the protein endogenously or through drug selection, Pgp predominantly localized to low-density membranes following separation on a sucrose gradient. When highly overexpressed in NIH 3T3 cells, a prominent amount of Pgp also was detected in high-density membranes. Removing cholesterol from cells with beta-methylcyclodextrin (CD), a sterol acceptor molecule, shifted fractions that contained Pgp from low toward high density, and this effect was reversed to a similar extent by restoring sterols with either cholesterol or enantiomeric cholesterol. However, function of human MDR1 Pgp as probed with Tc-Sestamibi, a transport substrate for Pgp, was not dependent on localization of Pgp in cholesterol-enriched membranes. Specific inhibition of MDR1 Pgp with GF120918 or LY335979 also was independent of cholesterol. Cell-type-specific effects of cholesterol content on function of human Pgp were detected by use of daunomycin, another substrate for Pgp, although efficacy of inhibitors remained independent of cholesterol. Conversely, both function and inhibition of hamster Pgp as measured with Tc-Sestamibi and daunomycin were in part dependent on normal cell content of cholesterol. These data show that Pgp preferentially localizes to low-density, cholesterol-enriched membrane domains, but acute depletion of cholesterol impacts Pgp-mediated drug transport in a substrate- and cell-type-specific manner.     

Study of the complex formation of daunomycin with deoxytetranucleotides with bases of differing sequence in an aqueous solution by 1H-NMR spectroscopy

The complex formation of the antibiotic daunomycin with deoxytetranucleotides of different base sequence in the chain, 5'-d(GpCpGpC), 5'-d(CpGpCpG), and 5'-d(TpGpCpA) in aqueous salt solution was studied by 1D and 2D (2M-TOCSY and 2M-NOESY) 1H-NMR spectroscopy. Concentration and temperature dependences of proton chemical shifts of molecules were measured. Based on these dependences, reaction equilibrium constants, relative content of various complexes depending on concentration and temperature, limiting values of chemical shifts of protons of daunomycin incorporated in various complexes, and the thermodynamic parameters delta H and delta S of complex formation were calculated. The analysis of the results enables the conclusion that the sites of predominant intercalation of daunomycin are triplet nucleotide sequences, the binding sites of the antibiotic with three consecutive GC pairs in the tetranucleotide duplex being more preferential. Daunomycin exhibits no sequence specificity upon binding to the single-stranded deoxynucleotide sequence. From the calculated values of induced chemical shifts of daunomycin protons and 2M-NOE data, the most probable spatial structures of complexes (1:2) of the antibiotic with deoxytetranucleotides were constructed. The binding of the second daunomycin molecule to both the single-stranded and duplex form of tetramers is of pronounced anticooperative mode, which is explained by the presence in the antibiotic of a positively charged amino sugar residue, which poses considerable steric constraints for the insertion of the second antibiotic molecule into the short tetranucleotide sequence. The results were compared with the data obtained under identical experimental conditions for typical intercalators proflavine and ethidium bromide.     

Binding of the Lactococcal Drug Dependent Transcriptional Regulator LmrR to Its Ligands and Responsive Promoter Regions

The heterodimeric ABC transporter LmrCD from Lactococcus lactis is able to extrude several different toxic compounds from the cell, fulfilling a role in the intrinsic and induced drug resistance. The expression of the lmrCD genes is regulated by the multi-drug binding repressor LmrR, which also binds to its own promoter to autoregulate its own expression. Previously, we reported the crystal structure of LmrR in the presence and absence of the drugs Hoechst 33342 and daunomycin. Analysis of the mechanism how drugs control the repressor activity of LmrR is impeded by the fact that these drugs also bind to DNA. Here we identified, using X-ray crystallography and fluorescence, that riboflavin binds into the drug binding cavity of LmrR, adopting a similar binding mode as Hoechst 33342 and daunomycin. Microscale thermophoresis was employed to quantify the binding affinity of LmrR to its responsive promoter regions and to evaluate the cognate site of LmrR in the lmrCD promoter region. Riboflavin reduces the binding affinity of LmrR for the promoter regions. Our results support a model wherein drug binding to LmrR relieves the LmrR dependent repression of the lmrCD genes.     

The cAMP-Epac-Rap1 pathway regulates cell spreading and cell adhesion to laminin-5 through the alpha3beta1 integrin but not the alpha6beta4 integrin

Laminin-5 is an important constituent of the basal lamina. The receptors for laminin-5, the integrins alpha3beta1 and alpha6beta4, have been associated with epithelial wound migration and carcinoma invasion. The signal transduction mechanisms that regulate these integrins are not well understood. We report here that the small GTPase Rap1 regulates the adhesion of a number of cell lines to various extracellular matrix proteins including laminin-5. cAMP also mediates cell adhesion and spreading on laminin-5, a process that is independent of protein kinase A but rather dependent on Epac1, a cAMP-dependent exchange factor for Rap. Interestingly, although both alpha3beta1 and alpha6beta4 mediate adhesion to laminin-5, only alpha3beta1-dependent adhesion is dependent on Rap1. These results provide evidence for a function of the cAMP-Epac-Rap1 pathway in cell adhesion and spreading on different extracellular matrix proteins. They also define different roles for the laminin-binding integrins in regulated cell adhesion and subsequent cell spreading.     

Interactions between an anthracycline antibiotic and DNA: molecular structure of daunomycin complexed to d(CpGpTpApCpG) at 1.2-A resolution

The crystal structure of a daunomycin-d(CGTACG) complex has been solved by X-ray diffraction analysis and refined to a final R factor of 0.175 at 1.2-A resolution. The crystals are in a tetragonal crystal system with space group P4(1)2(1)2 and cell dimensions of a = b = 27.86 A and c = 52.72 A. The self-complementary DNA forms a six base pair right-handed double helix with two daunomycin molecules intercalated in the d(CpG) sequences at either end of the helix. Daunomycin in the complex has a conformation different from that of daunomycin alone. The daunomycin aglycon chromophore is oriented at right angles to the long dimension of the DNA base pairs, and the cyclohexene ring A rests in the minor groove of the double helix. Substituents on this ring have hydrogen-bonding interactions to the base pairs above and below the intercalation site. O9 hydroxyl group of the daunomycin forms two hydrogen bonds with N3 and N2 of an adjacent guanine base. Two bridging water molecules between the drug and DNA stabilize the complex in the minor groove. In the major groove, a hydrated sodium ion is coordinated to N7 of the terminal guanine and the O4 and O5 of daunomycin with a distorted octahedral geometry. The amino sugar lies in the minor groove without bonding to the DNA. The DNA double helix is distorted with an asymmetrical rearrangement of the backbone conformation surrounding the intercalator drug. The sugar puckers are C1,C2'-endo, G2,C1'-endo, C11,C1'-endo, and G12,C3'-exo. Only the C1 residue has a normal anti-glycosyl torsion angle (chi = -154 degrees), while the other three residues are all in the high anti range (average chi = -86 degrees). This structure allows us to identify three principal functional components of anthracycline antibiotics: the intercalator (rings B-D), the anchoring functions associated with ring A, and the amino sugar. The structure-function relationships of daunomycin binding to DNA as well as other related anticancer drugs are discussed.     

Different distribution of daunomycin in plasma membranes from drug-sensitive and drug-resistant P388 leukemia cells.

When the anthracycline daunomycin (DNM) is incorporated into isolated plasma membranes from P388 murine leukemia cells, the drug partitions between 'deep' and 'surface' membrane domains. Such domains have been characterized on the basis of: (1) fluorescence resonance energy transfer between 1,6-diphenylhexa-1,3,5-triene or 1-[4-(trimethylamino)phenyl]-6-phenylhexa-1,3,5-triene as energy donors, which are well known in their positioning within the membrane, and daunomycin as the energy acceptor, and (2) quenching of the fluorescence of the membrane-associated drug by the water-soluble quencher iodide. The distribution of DNM between the two plasma membrane domains is different depending on the cellular phenotype. Thus, in membranes from drug-sensitive cells, DNM is preferentially confined to 'surface' domains, while in membranes from drug-resistant cells, the drug distributes more homogeneously between 'surface' and 'deep' domains. Experiments using artificial lipid vesicles suggest that differences in the relative levels of certain lipids in the plasma membranes from drug-sensitive and drug-resistant cells, namely phosphatidylserine and cholesterol, are partly responsible for the observed differences in the distribution of DNM. Since drug-membrane interactions are important in anthracycline cytotoxicity, it is possible that our observations on a different membrane distribution of daunomycin, may be related to the different sensitivity to the drug exhibited by these cells.     

The protein kinase kin1 is required for cellular symmetry in fission yeast

The fission yeast Schizosaccharomyces pombe is a highly polarized unicellular eukaryote with two opposite growing poles in which F-actin cytoskeleton is focused. The KIN1/PAR-1/MARK protein family is composed of conserved eukaryotic serine/threonine kinases which are involved in cell polarity, microtubule stability or cell cycle regulation. Here, we investigate the function of the fission yeast KIN1/PAR-1/MARK member, kin1p. Using a deletion allele (kin1Delta), we show that kin1 mutation promotes a delay in septation. Kin1p regulates the structure of the new cell end after cytokinesis by modulating cell wall remodeling. Abnormal shaped interphase kin1Delta cells misplace F-actin patches and the premitotic nucleus. Thus, mitotic kin1Delta cells misposition the F-actin ring assembly site that is dependent on the position of the interphase nucleus. The resulting asymmetric cell division produces daughter cells with distinct shapes. Overexpressed kin1p accumulates asymmetrically at the cell cortex and affects cell shape, F-actin organization and microtubules. Our results suggest that correct dosage of kin1p at the cortex is required for spatial organization of the fission yeast cell.     

Effective drug-antibody targeting using a novel monoclonal antibody against the proliferative compartment of mammalian squamous carcinomas

Summary mAb 174H.64, which selectively recognizes an epitope expressed on the proliferating cells of mammalian squamous carcinomas, was covalently coupled to daunomycin (DM) by an acid-sensitive linker and tested for its selective cytotoxicity for squamous carcinomas. A murine lung squamous carcinoma model for chemoimmunotherapy using mAb 174H.64-DM conjugates was developed. This model utilizes the KLN-205 cell line, which metastasizes to the lungs following i.v. injection and shows a pattern of growth similar to those of spontaneous squamous carcinomas, characterized by highly proliferative cells at the periphery of the tumor (reactive with 174H.64) with the keratinized differentiated cells toward the center (not reactive with 174H.64). 174H.64-DM conjugates showed marked and specific cytotoxicity against KLN-205 cells both in vitro and following i.v. injection of the immunoconjugate in mice with established lung metastases. The conjugate was nearly as effective as daunomycin alone when incubated in vitro with KLN-205 cells and much more effective than daunomycin alone in vivo or other control immunoconjugates, which were ineffective. Finally, while the free 174H.64 mAb produced a significantly increased time of survival of mice bearing KLN-205 metastases, a much greater survival was found with mice treated with the 174H.64-DM immunoconjugate, some mice apparently demonstrating long-term survival (>100 days). We conclude that mAb 174H.64 may have potential therapeutic benefit against squamous carcinoma.This work was supported by the Medical Research Council of Canada and Biomira Inc.     

Jacaric acid, a linolenic acid isomer with a conjugated triene system, has a strong antitumor effect in vitro and in vivo

In this study, we compared the cytotoxic effects of natural conjugated linolenic acids (CLnAs) on human adenocarcinoma cells (DLD-1) in vitro, with the goal of finding CLnA isomers with strong cytotoxic effects. The antitumor effect of the CLnA with the strongest cytotoxic effect was then examined in mice. The results showed that all CLnA isomers have strong cytotoxic effects on DLD-1 cells, with jacaric acid (JA) having the strongest effect. Examination of the mechanism of cell death showed that CLnAs induce apoptosis in DLD-1 cells via lipid peroxidation. The intracellular levels of incorporated CLnAs were measured to examine the reason for differences in cytotoxic effects. These results showed that JA was taken into cells efficiently. Collectively, these results suggest that the cytotoxic effect of CLnAs is dependent on intracellular incorporation and induction of apoptosis via lipid peroxidation. JA also had a strong preventive antitumor effect in vivo in nude mice into which DLD-1 cells were transplanted. These results suggest that JA can be used as a dietary constituent for prevention of cancer.     

Alterations of rx1 and pax6 expression levels at neural plate stages differentially affect the production of retinal cell types and maintenance of retinal stem cell qualities

rx1 and pax6 are necessary for the establishment of the vertebrate eye field and for the maintenance of the retinal stem cells that give rise to multiple retinal cell types. They also are differentially expressed in cellular layers in the retina when cell fates are being specified, and their expression levels differentially affect the production of amacrine cell subtypes. To determine whether rx1 and pax6 expression after the eye field is established simply maintains stem cell-like qualities or affects cell type differentiation, we used hormone-inducible constructs to increase or decrease levels/activity of each protein at two different neural plate stages. Our results indicate that rx1 regulates the size of the retinal stem cell pool because it broadly affected all cell types, whereas pax6 regulates more restricted retinal progenitor cells because it selectively affected different cell types in a time-dependent manner. Analysis of rx1 and pax6 effects on proliferation, and expression of stem cell or differentiation markers demonstrates that rx1 maintains cells in a stem cell state by promoting proliferation and delaying expression of neural identity and differentiation markers. Although pax6 also promotes proliferation, it differentially regulates neural identity and differentiation genes. Thus, these two genes work in parallel to regulate different, but overlapping aspects of retinal cell fate determination.     

Structural and activity changes in three bioactive anuran peptides when Asp is replaced by isoAsp

The Asp and isoAsp isomers of three bioactive peptides, Crinia angiotensin 11 [APGDRIYHPF(OH)], uperin 1.1 [pEADPNAFYGLM(NH₂)] and citropin 1.1 [GLFDVIKKVASVIGGL(NH₂)] were tested for changes in (i) susceptibility towards proteolytic cleavage, (ii) activity (smooth muscle activity for Crinia angiotensin 11 and uperin 1.1 isomers, and antimicrobial activity for the two isomers of citropin 1.1), and (iii) 3D structures in water, trifluoroethanol-d₃/water (1:1) and DPC micelles as determined by 2D nuclear magnetic resonance spectroscopy. Proteolytic cleavage with trypsin was identical for each pair of Asp/isoAsp isomers. Cleavage with chymotrypsin was the same for the Crinia angiotensin and uperin 1.1 isomeric pairs, but different for the two Asp/isoAsp citropin 1.1 isomers. Chymotrypsin cleaved at Phe3 (adjacent to Asp4) for citropin 1.1, but not at Phe3 (adjacent to isoAsp4) for isoAsp citropin 1.1. The smooth muscle activity of the isoAsp isomer of Crinia angiotensin 11 was less than that of the Asp isomer. The smooth muscle activity of isoAsp3-uperin 1.1 is greater than that of the Asp isomer at low concentration (<10⁻⁹ M) but no different from the Asp isomer at concentrations > 10⁻⁹ M. Citropin 1.1 is a wide-spectrum antibiotic against Gram positive organisms, while the isoAsp isomer is inactive against the test pathogens Staphylococcus aureus and Bacillus subtilis. The observed changes in activity are accompanied by changes in the 3D structures of isomers as determined by 2D nuclear magnetic resonance spectroscopy.     

Structural comparison of anticancer drug-DNA complexes: adriamycin and daunomycin

The anticancer drugs adriamycin and daunomycin have each been crystallized with the DNA sequence d(CGATCG) and the three-dimensional structures of the complexes solved at 1.7- and 1.5-A resolution, respectively. These antitumor drugs have significantly different clinical properties, yet they differ chemically by only the additional hydroxyl at C14 of adriamycin. In these complexes the chromophore is intercalated at the CpG steps at either end of the DNA helix with the amino sugar extended into the minor groove. Solution of the structure of daunomycin bound to d(CGATCG) has made it possible to compare it with the previously reported structure of daunomycin bound to d(CGTACG). Although the two daunomycin complexes are similar, there is an interesting sequence dependence of the binding of the amino sugar to the A-T base pair outside the intercalation site. The complex of daunomycin with d(CGATCG) has tighter binding than the complex with d(CGTACG), leading us to infer a sequence preference in the binding of this anthracycline drug. The structures of daunomycin and adriamycin with d(CGATCG) are very similar. However, there are additional solvent interactions with the adriamycin C14 hydroxyl linking it to the DNA. Surprisingly, under the influence of the altered solvation, there is considerable difference in the conformation of spermine in these two complexes. The observed changes in the overall structures of the ternary complexes amplify the small chemical differences between these two antibiotics and provide a possible explanation for the significantly different clinical activities of these important drugs.