It is known that the interruption of normal
iron metabolism with
chelators of
iron, toxic metals, toxic metals bound to
transferrin, or anti-
transferrin receptor antibodies leads to significant inhibition of
tumor cell growth in cell culture systems and animal models. In the present study, we found that
iron depletion was produced by the
iron chelator deferoxamine mesylate, the free toxic metals
gallium or
indium, and the toxic metals
gallium or
indium bound to
transferrin in the MCF-7 human
breast cancer cell line, and this induced the condensation and fragmentation of
chromatin, and the formation of
DNA fragments characteristic of apoptosis. The induction of apoptosis was quantitated with
acridine orange and
ethidium bromide staining of apoptotic cells, separation of fragmented
DNA from radiolabeled cells, and in situ
terminal deoxynucleotidyl transferase-mediated dUTP-
digoxigenin nick end labeling (TUNEL) assays. The apoptosis, caused by
deferoxamine mesylate, and
gallium or
indium bound to
transferrin in the MCF-7 cells, can be completely inhibited by excess
ferric chloride or equimolar
iron-loaded
transferrin.
Gallium-
transferrin and
indium-
transferrin complexes induced more apoptosis than their respective
salts in the MCF-7 cells.
Deferoxamine mesylate induced a small increase in the endogenous expression of both the bcl-2 and bax genes in the MCF-7 cells and this can be prevented by
ferric chloride. In the 13762NF rat mammary
adenocarcinoma model, in situ TUNEL assays showed that the
iron-deficiency following a low
iron diet or
intravenous injection of
deferoxamine mesylate produced 5.32 +/- 3.90% and 6.46 +/- 3.58% of apoptotic cells, respectively, compared to 2.01 +/- 1.20% of apoptotic cells in the control rats maintained on a normal diet (p < 0.05 and p < 0.01, respectively, Student's t-test). This is the first report of
iron depletion caused by a low
iron diet or
deferoxamine mesylate treatment inducing apoptosis in rats bearing the 13762NF marnmary
adenocarcinoma.