Stereoisomeric [1,2-bis(3-hydroxyphenyl)ethylenediamine]platinum(II) complexes, Part III: Evaluation of the mammary tumor inhibiting properties

[N-ethyl- and [N,N'-diethyl-1,2-bis(2,6-difluoro-3-hydroxyphenyl)-ethylenediamine]dichloroplatinum(II): structure and cytotoxic/estrogenic activity in breast cancer cells

N-Ethyl and N,N'-diethyl derivatives (erythro- and threo-2-PtCl2; meso- and D,L-3-PtCl2) of [meso- and [D,L-1,2-bis(2,6-difluoro-3-hydroxyphenyl)ethylenediamine]dichloroplatinum(II) (meso- and D,L-1-PtCl2) were synthesized and tested for cytotoxicity on the estrogen receptor-positive (ER+) human MCF-7 breast cancer cell line. In this test, only D,L-1-PtCl2 and threo-2-PtCl2 showed strong cytotoxic properties. This revealed the existence of at least one NH2 fragment as a prerequisite for antitumor activity. Furthermore, studies on the three-dimensional structure of the new compounds demonstrated that the aryl and alkyl residues at the five-membered chelate ring have to be arranged in equatorial positions for the triggering of cytotoxic effects, very likely due to the reaction with d(GpG) sequences in DNA resulting in GG-N7,N7 chelates. A contribution of the ER-mediated processes--(a) hindrance of the cellular processing of Pt-modified DNA by overexpression of high mobility group domain proteins and (b) interruption of the vicious circle of mutual growth stimulation of breast cancer cells and granulocytes/macrophages by reduction of the formation of key cytokines--to the anti-breast cancer activity of threo-2-PtCl2 is unlikely, since we did not observe transcription activation in the test on ER+ MCF-7 breast cancer cells stably transfected with luciferase reporter plasmid ERE(wtc)luc.

Development of Cobalt(3,4-diarylsalen) Complexes as Tumor Therapeutics

[1,6-Bis(2-hydroxyphenyl)-3,4-diaryl-2,5-diazahexa-1,5-diene]cobalt(II) complexes (cobalt(3,4-diarylsalen)) with 2-, 3-, or 4-OCH(3)/OH substituents in the 3,4-standing aryl rings were synthesized and tested for antitumor activity in vitro on the MCF-7, MDA-MB 231, and LNCaP/FGC cell lines. The cytotoxicity depended on both the configuration of the diene ligand and the kind of substituents in the 3,4-standing aromatic rings. d,l-7 (2-OCH(3)), d,l-8 (3-OCH(3)), and d,l-9 (4-OCH(3)) were equipotent to cisplatin, while the respective hydroxy-substituted complexes (d,l-10 (2-OH), d,l-11 (3-OH), and d,l-12 (2-OH)) as well as all of the meso-configured compounds (m-7 to m-12) did not influence the cell growth. Interestingly, a high catalytic potency and a rapid and high accumulation in MCF-7 cells (15- to 25-fold compared to the cell culture medium (5 microM)) were demonstrated for m-7 (2-OCH(3)), m-8 (3-OCH(3)), and m-9 (4-OCH(3)). Therefore, a mode of action based on a cobalt-catalyzed oxidative damage of the DNA is not very likely.

Effect of a diphenylethylenediamine platinum complex on steroidogenesis in rats

Although less cytotoxic, the new platinum complex [meso-1,2-bis(2,6-difluoro-4-hydroxyphenyl)-ethylenediamine]sulfatopl atinum (II) (2) is equipotent to cisplatin (1) in the oestrogen-dependent MXT mammary tumour of the mouse. As this may be due to oestrogen level-lowering properties, we compared the effect of 1 and 2 on steroidogenesis in the rat. A single dose of 1 and 2 (20 mumol/kg s.c.) decreased plasma testosterone level in male rats by 90% (1, day 3) and 80% (2, day 7). Luteinizing hormone level remained unchanged in intact and in ovariectomized rats. The activities of the following testicular enzymes were decreased (day 7): cholesterol side-chain cleavage enzyme (1: 33%; 2: 36%), 3 beta-hydroxysteroid dehydrogenase/delta 4,delta 5-isomerase (1: 31%; 2: 48%) and 17 alpha-hydroxylase/17,20-lyase (1: 21%; 2: 15%). Testicular microsomal cytochrome P450 content was also diminished (1: 60%; 2: 49%, day 7). Corticosterone level in plasma and biosynthesis in adrenal explants was not affected, indicating the selectivity of action at the gonadal level. In vitro, neither 1 nor 2 (2 and 20 microM) influenced binding of human chorionic gonadotropin to testis interstitial cells during an observation period up to 21 h. These results suggest that 1 and 2 act at the gonadal level by inhibiting the expression of the steroidogenic enzymes. They do not, however, inactivate the luteinizing hormone receptor.

Third generation antitumor platinum(II) complexes of the [1-(fluoro/difluorophenyl)-2-phenylethylenediamine]platinum(II) type

The diastereomeric 1-(fluoro/difluorophenyl)-2-phenylethylene-diamines (4-fluoro: erythro-1/threo-1; 2,4-difluoro: erythro-2/-threo-2; 2,6-difluoro: erythro-3/threo-3) and the diastereomeric 1-(4-fluorophenyl)-2-(3-hydroxyphenyl)ethylenediamines (erythro-4/-threo-4) were synthesized from appropriately substituted stilbenes by reaction with IN3 and subsequent LiAlH4 reduction. Coordination of the 1,2-diphenylethylenediamines to platinum was carried out by use of K2PtI4. The water-soluble aquasulfato-platinum(II) complexes (erythro/threo-1-PtSO4-erythro/threo-4-PtSO4) were obtained from the diiodoplatinum(II) complexes by reaction with Ag2SO4. Additionally erythro/threo-1-PtSO4 and erythro/threo-4-PtSO4 were transformed into the dichloroplatinum(II) complexes (erythro/threo-1-PtCl2, erythro/threo-4-PtCl2) by treatment with KCl. In contrast to the less effective erythro-configurated sulfatoplatinum(II) complexes the threo-analogues showed comparable or even superior activities to cisplatin on the human MDA-MB-231 breast cancer cell line. On the MXT-M-3.2 breast cancer of the mouse only erythro- and threo-4-PtSO4 caused similar effects like cisplatin. The strong inhibitory effect of the diastereomeric sulfatoplatinum(II) complexes on the P-388 leukemia of the mouse was equal to that of cisplatin. On the latter tumor threo-4-PtCl2 was the most active among the less toxic dichloroplatinum(II) derivatives.

1,3-Diphenylpropane-1,3-diamines, VI): DNA-interaction, estrogen receptor affinity, and cytostatic activity of 1,3-diphenylpropane-1,3-diamine-Pt(II) complexes

The Pt(II) complexes of 1,3-diphenylpropane-1,3-diamines (part IV2)) were tested for DNA interaction (UV-difference spectroscopy, Tables 1 and 2), for affinity to the estrogen receptor (calf uterus cytosol; scarcely any affinity), and for cytostatic activity at estrogen independent MDA-MB 231 cells (Tables 3 and 4) and estrogen dependent MCF-7 cells (Tables 5 and 6). The data are compared with those reported for the analogous 1,2-diphenylethane-1,2-diamine-Pt(II) complexes: most probably, the cytostatic activity is not mediated by the estrogen receptor.