Conventional wisdom has been that arsenic trioxide, which works against some types of leukemia, cannot be used against solid tumors because of its extreme toxicity and rapid excretion from the body.
However, in a paper published in the July 2010 issue of the journal Clinical Cancer Research investigators at Northwestern University (Evanston, IL, USA) described a method for encapsulating arsenic trioxide inside nanoparticle-sized liposomal vesicles to form what they called "nanobins.” Efficacy of treatment with arsenic trioxide nanobins was evaluated in breast cancer-cell cultures and in a mouse model of human "triple-negative” breast cancer.
Results showed that while the nanobins were much less cytotoxic in vitro than free arsenic trioxide against the panel of human breast cancer-cell lines, they dramatically increased the therapeutic efficacy of arsenic trioxide in vivo in the mouse model of triple-negative breast cancer. Reduced plasma clearance, enhanced tumor uptake, and induction of tumor cell apoptosis were observed following nanobin treatment. None of these effects was seen in animals treated with arsenic trioxide alone or with empty nanobins.
"Everyone said you cannot use arsenic for solid tumors,” said senior author Dr. Tom O'Halloran, professor of chemistry and biochemistry at Northwestern University. "That is because they did not deliver it the right way. This new technology delivered the drug directly to the tumor, maintained its stability, and shielded normal cells from the toxicity. That is huge. Once you fine-tune this, you could use what would otherwise be a lethal or highly toxic dose of the drug, because a good deal of it will be directly released in the tumor.”
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