The crystal structure and absolute configuration of the antitumor platinum complex trans(OH)-Pt(OH)2(malonato)(1R,2R-cyclohexanediamine)

The absolute configuration of the anti-tumor complex trans(OH)-Pt(OH)2(malonato)(1R,2R-cyclohexanediamine) was determined by X-ray anomalous scattering technique. The final unit cell was monoclinic, space group P2(1) with a = 9.142 A, b = 7.788 A, c = 11.946 A, beta = 96.48 degrees, Z = 2. The crystal structure was determined by direct method and difference Fourier synthesis, and refined to R = 0.025 and Rw = 0.033 based on 2768 independent reflections. The platinum atom has roughly octahedral coordination. The cyclohexane ring has the expected chair configuration, with two amino groups in equatorial positions while the malonato ligand, in contrast, shows a boat conformation for six membered Pt O-C-C-C-O ring.

Integration and expression of a rabbit liver cytochrome P-450 gene in transgenic Nicotiana tabacum

Cytochrome P-450 is involved in the oxidative metabolism of a broad range of substrates. We have made a chimeric construct, pSN002, containing the cDNA for rabbit liver cytochrome P-450 (IIC14) under the control of the TR2' promoter for mannopine synthase in the Agrobacterium Ti plasmid. Nicotiana tabacum was transformed with Agrobacterium tumefaciens harboring a cointegrated plasmid pSN002::pGV2260. The presence of mRNA and of the translated protein from the chimeric cytochrome P-450 gene in transgenic plants was confirmed by RNA blot hybridization and by Western blot and immunohistochemical analyses, respectively. The transformants in which the foreign cytochrome P-450 protein is expressed show marked phenotypic changes, notably a tendency rapidly to senesce. We detected 2-propenylpyrrolidine, a degradative metabolite of nicotine alkaloids, in transgenic tobacco showing this pronounced phenotypic change. Such metabolism is likely to be due to the effect of senescence and not directly to the presence of the cytochrome P-450.

Antibodies against (1R,2R)-cyclohexanediamineplatinum(II)-DNA adduct recognize the conformational differences of isomeric analogues of cyclohexanediamine

Antibodies reactive to (1R,2R)-cyclohexanediamineplatinum(II)-DNA ((1R,2R)-cyclohexanediamine: 1R,2R-dach) adducts were elicited by immunization of rabbit with calf thymus DNA modified by Pt(1R,2R-dach)Cl2 at a ratio of bound platinum per nucleotide ((D/N)b) of 0.0335. In an enzyme-linked immunosorbent assay (ELISA), the binding of specific antibodies to Pt(1R,2R-dach)-DNA adduct (60 microliters of 1.235 x 10(-7) M Pt in each wells) on the assay plate was competitively inhibited by Pt(1R,2R-dach)-DNA adduct ((D/N)b = 0.0653) in the solution. Almost equal inhibition was observed with Pt(1S,2S-dach)-DNA ((D/N)b = 0.0412), an optical isomer of 1R,2R-dach. Pt(1R,2S-dach)-DNA ((D/N)b = 0.0371) and Pt(1R,3S-dach)-DNA ((D/N)b = 0.0281) in which the cyclohexane ring is stereochemically perpendicular to the platinum chelate plane, also inhibited antibody binding, but these adducts gave only incomplete inhibition at higher Pt-DNA adduct concentrations. Although Pt(1R,2R-dach)-d(GpG) and Pt(1R,2R-dach)(NH3)2 inhibited antibody binding, the affinity of the antibody for Pt(1R,2R-dach)(NH3)2 was lower than with Pt(1R,2R-dach)-DNA, and the inhibition behavior of Pt(1R,2R-dach)-d(GpG) was biphasic, i.e., at the lower concentration the inhibition curve was consistent with that of Pt(1R,2R-dach)-DNA, but at the higher concentration it shifted to that of Pt(1R,2R-dach)(NH3)2. The affinity of the antibody for cis-DDP was markedly lower than with Pt(1R,2R-dach)(NH3)2. These facts suggest that the antibodies may bind to the substituents (the platinum and its surroundings) of the various Pt complexes rather than the DNA structure altered by platinum binding.

Antitumor activity of steroid-containing platinum (II) complexes of 1R,2R-cyclohexanediamine and 2-(aminomethyl)-cyclohexylamine isomers against leukemia L1210

Various steroid-containing platinum (Pt) complexes of 1R,2R-cyclohexanediamine (= 1R,2R-dach) and cis-dl- and trans-dl-2-(aminomethyl)cyclohexylamine (= amcha) were synthesized and their antitumor activity was screened against leukemia L1210 according to the Pt Analog Study Protocol. Among the Pt complexes prepared, Pt 1R,2R-dach complexes of cortisone, hydrocortisone, methylprednisolone, testosterone, estriol and progesterone showed very high antitumor activity. Pt complexes of cis-dl- and trans-dl-amcha prednisolone, Pt(17-OH-progesterone) (trans-dl-amcha), Pt complexes of cis-dl- and trans-dl-amcha progesterone were found to be very effective.

Interaction of zinc ions with arsanilazotyrosine-248 carboxypeptidase A

The interaction between arsanilazotyrosine-248 carboxypeptidase A ([(Azo-CPD)Zn]) and excess zinc ions has been studied by stopped-flow and spectrophotometric methods at pH 8.2 and 7.7, I = 0.5 M (NaCl), and 25 degrees C. When excess zinc ions bind to arsanilazotyrosine-248 carboxypeptidase A, the characteristic red color, which arises from the intramolecular complex of the arsanilazotyrosine-248 residue with the active site zinc of the enzyme, changes to yellow with the inhibition of peptidase activity of the enzyme. Excess zinc ions have two binding sites for arsanilazotyrosine-248 carboxypeptidase A, and the binding constants of the first site (3.9 X 10(5) M-1 at pH 8.2; 7.1 X 10(4) M-1 at pH 7.7) are much larger than those of the second site (1.8 X 10(3) M-1 at pH 8.2; 7 X 10(2) M-1 at pH 7.7). The binding of excess zinc ions to the first site is completely correlated with the inhibition of the enzyme peptidase activity and the color change of the enzyme. The results can be understood in terms of zinc ions reacting with only one of three conformational states of arsanilazotyrosine-248 carboxypeptidase A [Harrison, L. W., Auld, D. S., & Vallee, B. L. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 4356].(ABSTRACT TRUNCATED AT 250 WORDS)

Antitumor activity of l-OHP in mice

The isomeric mixtures of platinum complexes of diaminocyclohexane (DACH) had been found active on several murine tumors. A recent separation of the oxalato-platinum complex of trans-l-DACH isomer allowed more precise screening studies and permitted the selection of one compound: l-OHP was submitted to our murine tumor screening system. The drug was given: (a) at doses of 1-12 mg/kg i.p. or i.v. on day 1, 5 and 9 compared to identical doses of cis-dichlorodiamine platinum II (CDDP) in L1210 bearing mice and (b) to AkR leukemia, LGC lymphoma, glioma 26, B16 melanoma, MA 16-C mammary carcinoma and Lewis lung carcinoma bearing mice at 2 dosages: 5 mg/kg (minimal effective dose on L1210), and 8 mg/kg (subtoxic dose in L1210). Acute LD10 and LD50 appeared similar to CDDP and l-OHP. l-OHP administered i.p. was more active on L1210 than CDDP. On L1210 grafted intracerebrally and on LGC lymphoma l-OHP increased significantly the lifespan while CDDP was inactive. On AkR leukemia, both drugs were active but l-OHP was less toxic. Both drugs were inactive on murine solid tumors. No renal toxicity was observed with l-OHP as compared to CDDP.

Preparation of antitumor platinum(II) complexes of 1,2-diphenylethylenediamine isomers and their interactions with DNA and its purine moieties

A series of Pt(II) complexes containing 1,2-diphenylethylenediamine (stien) isomers were synthesized and tested for their antitumor activity against leukemia L1210. Among the Pt(II) complexes examined water-soluble Pt(II) complexes with sulfate, nitrate and D-glucuronate ions as leaving groups exhibited relatively high antitumor activity. Furthermore, the interactions between calf-thymus DNA and Pt(SO4) (stein) complexes were investigated by means of circular dichroism spectrometry. Dichroism enhancements observed in the interaction between DNA and Pt(SO4) (stien) complexes were analysed to be contributable to two factors: (1) vicinal effects of DNA on the d-d transitions of Pt(II) ions and (2) conformational changes of DNA caused by the coordination of cis-configurational Pt(II) complexes.

Selective binding behavior of zinc(II) and copper(II) ions to their native sites of apo-bovine superoxide dismutase

The four binding constants of zinc(II) ions to apo-bovine superoxide dismutase were measured by the method of equilibrium dialysis. The binding constants (10(11.1)-10(10.9) M-1) of zinc ions to the native zinc sites were much larger than those to the native copper sites (10(7.8)-10(6.5) M-1) at pH 6.25. The competitive reaction between copper(II) and zinc(II) ions for the native copper sites of copper free bovine superoxide dismutase was also investigated. The native copper sites of bovine superoxide dismutase selectively react with copper ions, because the binding constants of copper ions for the native copper sites were much larger (10(6) times) than those of zinc ions.

Relation of conformation to antitumor activity of platinum(II) complexes of 1,2-cyclohexanediamine and 2-(aminomethyl)cyclohexylamine isomers against leukemia P388

The antitumor activity of various platinum(II) complexes of 1,2-cyclohexanediamine and 2-(aminomethyl)cyclohexylamine isomers against leukemia P388 was evaluated by means of the platinum analogue study protocol recommended by the National Cancer Institute. For the former complexes, trans isomers are more efficacious than the corresponding cis isomers. For the latter complexes, cis isomers seem to be somewhat more active than trans isomers. 2-(Aminomethyl)cyclohexylamine platinum complexes exhibited higher activity than 1,2-cyclohexanediamine complexes in this tumor system. These findings encouraged us to determine the structural differences between 1,2-cyclohexanediamine and 2-(aminomethyl)cyclohexylamine complexes. Their structures of platinum complexes were elucidated from circular dichroism and 13C NMR spectral analyses, and it has been concluded that the cyclohexane ring of cis-1,2-cyclohexanediamine is nearly perpendicular to the chelate ring, while both rings of trans-1,2-cyclohexanediamine and trans-2-(aminomethyl)cyclohexylamine complexes lie in a common plane. The structure of cis-2-(aminomethyl)cyclohexylamine complexes is flexible, and the cyclohexane ring is not perpendicular to the chelate ring. The coplanarity of trans isomers and the flexibility of cis-2-(aminomethyl)cyclohexylamine complexes allow them easy approach to the target DNA. However, the perpendicular ring of cis-1,2-cyclohexanediamine complexes would prevent their interactions with dna molecules due to the steric hindrance.

Antitumor activity of platinum(II) complexes of 1,2-diamino-cyclohexane isomers

Dichloro, dibromo, oxalato, malonato, dinitrato, sulfato and mono and bis-(D-glucuronato) platinum(II) complexes of 1,2-diaminocyclohexane (dach) isomers were prepared and tested on L1210 mouse leukemia employing the NCI protocol for evaluation of Pt analogs. A large number of long-term survivors were observed with certain analogs, though the therapeutic indices (optimal dose/minimum effective dose) were not large. Among the analogs tested, the oxalato, malonato, dinitrato and mono-(D-glucuronato) Pt(II) complexes of trans-1,2-diaminocyclohexane were found to be particularly effective. The glucuronato Pt complexes appear to be promising candidates for clinical trial since they have the highest solubility in water.

Antitumor activity of water-soluble platinum(II) complexes of 1,2-cyclohexanediamine isomers

Dichloroplatinum(II) complexes of 1,2-cyclohexanediamine isomers were reported to have high antitumor activity against leukemia L-1210 and P-388, but they were hardly soluble in water and, therefore, dibromo- and diiodo-platinum(II) complexes of 1,2-cyclohexanediamine isomers were prepared. They were not soluble in water but showed high antitumor activity. When the chloride ions are replaced with sulfate ions, they become soluble and also they are anti-tumor active. Bismonobromoacetatoplatinum (II) complexes were synthesized and tested. Mono- and bis-(D-glucuronato)platinum(II) complexes of 1,2-cyclohexanediamine isomers were newly synthesized. All of them were freely soluble in water and showed high antitumor activity with low toxicity. The chelated mono(D-glucuronato)platinum(II) was found to be more effective than the monodentate bis(D-glucuronato)platinum (II) complexes.