The marked activity of [meso-1, 2-bis(2, 6-difluoro-3-hydroxyphenyl)
ethylenediamine]
platinum(II) (meso-3-PtLL', L, L' = Cl(2) or L =
OH(2), L' = OSO(3)) on the
hormone-sensitive MXT-M-3, 2
breast cancer implanted in mice is most probably due to a mechanism based on the reduction of the endogenous
estrogen level. Cytotoxic effects which are poorly pronounced in experiments on several
breast cancer cell lines (e.g. MCF-7), do not significantly contribute to the anti-
breast cancer activity of this compound. In contrast to this, the standard
cisplatin and the structurally related comparison compound [meso-1, 2-bis(4-fluorophenyl)
ethylenediamine]
platinum(II) (meso-4-PtLL', L, L' = Cl(2) or L =
OH(2), L' = OSO(3)) are strongly active in vivo as well as in vitro. Both effects entail programmed cell death, which is responsible for the inhibition of the
tumor growth. The minor cytotoxicity of meso-3-PtLL' in
breast cancer cell cultures is caused neither by an inappropriate rate of reaction with bionucleophiles (e.g. by a too fast inactivation by
plasma proteins) nor solely by the observed poor absorption by the
tumor cells resulting in an insufficient drug concentration at the
DNA. Additionally, an impeded reaction with biologically important,
guanine-rich sequences of
DNA (owing to the 2, 6-standing F atoms which hinder the drug-target inter action) must be assumed as cause of its marginal cytotoxicity.