Photo: Breast Cancer Cell
Women with triple negative breast
cancer have poor survival rates;
© NCI Visual Online

That drug is arsenic trioxide, recently adopted by Western oncologists for a type of leukaemia. The cancer is triple negative breast cancer, which often doesn't respond well to chemotherapy. Women with triple negative breast cancer have a high risk of the cancer metastasizing and poor survival rates.

Prior to the research, arsenic hadn't been effective in solid tumours. After the drug was injected into the bloodstream, it was excreted too rapidly to work. The concentration of arsenic couldn't be increased, because it was then too toxic.

A new arsenic nanoparticle – designed to slip undetected through the bloodstream until it arrives at the tumour and delivers its poisonous cargo – solved all that. The nanoparticle, called a nanobin, was injected into mice with triple negative breast tumours. Nanobins loaded with arsenic reduced tumour growth in mice, while the non-encapsulated arsenic had no effect on tumour growth. The arsenic nanobins blocked tumour growth by causing the cancer cells to die by a process known as apoptosis.

The nanobin consists of nanoparticulate arsenic trioxide encapsulated in a tiny fat vessel and coated with a second layer of a cloaking chemical that prolongs the life of the nanobin and prevents scavenger cells from seeing it. The nanobin technology limits the exposure of normal tissue to the toxic drug as it passes through the bloodstream. When the nanobin gets absorbed by the abnormal, leaky blood vessels of the tumour, the nanoparticles of arsenic are released and trapped inside the tumour cells.

"The anti-tumour effects of the arsenic nanobins against clinically aggressive triple negative breast tumours in mice are extremely encouraging," said Vince Cryns, senior author of a paper on the research.

The nanoparticle technology has great potential for other existing cancer drugs that have been shelved because they are too toxic or excreted too rapidly, Cryns noted. "We can potentially make those drugs more effective against solid tumours by increasing their delivery to the tumour and by shielding normal cells from their toxicity," he said. "This nanotechnology platform has the potential to expand our arsenal of chemotherapy drugs to treat cancer."; Source: Northwestern University