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A new study in mice reports that injection of gold nanoparticles into breast tumors can make the tumor cells more sensitive to radiation therapy. Gold nanoshell technology is currently undergoing clinical trials, which may provide additional impetus for killing tumor cells in patients with refractory breast cancer. The study was published online October 27 in the journal Science Translational Medicine.
One of the biggest obstacles to combating breast cancer is that there is a small group of cancer stem cells in the tumor, which are more resistant to radiotherapy and chemotherapy than the main tumor cells; the tumor regeneration after treatment is often attributed to These cancer stem cells. In an effort to kill as many cancer cells as possible, scientists have invented new technologies that accompany radiotherapy and other conventional therapies, including hyperthermia, which involves exposing body tissues to temperatures as high as 45 degrees Celsius. Previous studies have shown that hot temperatures can damage and kill cancer cells, and can make cancer stem cells more sensitive to radiotherapy, while also minimizing damage to normal tissues. However, in the past few years, hyperthermia for breast cancer has largely been abandoned because it is difficult to rapidly warm the tumor without burning the surrounding tissue. To solve this problem, Rachel Atkinson and colleagues designed gold nanoparticles to warm cancer stem cells and make them more sensitive to radiation therapy. They demonstrated that the implementation of hyperthermia using gold nanoparticles can effectively suppress cancer stem cells in a mouse breast cancer model.
Gold is an ideal coating for nanospheres (ie, very small spherical silica blocks) because it is less toxic in biological tissues than other metals. In this test, a dose of gold nanospheres was injected directly into the tumor of mice. These gold nanospheres leak out of the blood vessels and accumulate in the tumor and cause local warming when activated by the laser. This warming induced by the nanosphere shell prevents tumor cells from repairing the double-strand DNA breaks caused by radiation, thus increasing their sensitivity to radiation therapy. One day after the injection of the gold nanospheres, the mice received a single dose of radiation or a single dose of radiation and 20 minutes of hyperthermia.
After 2 days of treatment, those cells that received only radiotherapy split faster and would develop more tumors more actively than those who did not. On the other hand, those who received radiotherapy and heating therapy had slower onset of cancer cells and fewer tumors, suggesting that hyperthermia prevented the growth of cancer stem cells and may have altered their rapid growth characteristics.
The researchers went on to conduct further experiments: the above experiments were repeated for human breast tumor cells that were propagated in mice. Once again, they saw that the warming effect induced by the nanosphere shell made human breast cancer stem cells more sensitive to radiotherapy.