Carbon Nanotubes Kill Breast Cancer Stem Cells
Breast cancer stem cells, the slow-growing, hard-to-kill malignant cells that are thought to be responsible for the growth and spread of breast cancer, have proven remarkably resistant to traditional chemotherapy and radiation therapy. Now, researchers at Wake Forest Baptist Medical Center have shown that multi-walled carbon nanotubes (MWCNTs) injected into breast tumors and irradiated with a quick, 30-second laser beam, are effective at killing breast cancer stem cells.
Suzy Torti led the research team that conducted this work. She and her colleagues published their finding in the journal Biomaterials. Earlier work by Dr. Torti's research team had demonstrated that MWCNTs irradiated with short laser pulses generate heat that can kill kidney tumors.
Using a mouse model of human breast cancer, the researchers injected tumors containing breast cancer stem cells with MWCNTs, which consist of concentric tubes of graphite. By themselves, nanotubes do not kill tumors, but if they are exposed to laser-generated, near-infrared radiation they start to vibrate and produce heat. This combination can produce a local region in the tumor that is hot enough to kill any tumor cell, not just those that are growing rapidly.
Using this method, the group was able to stop the growth of tumors that were largely composed of breast cancer stem cells. Breast cancer stem cells have high levels of the protein hsp90 which enables them to adapt to higher temperature fluctuations. The investigators showedthat rapid induction of high temperatures by the laser induces cell death by a process known as necrosis even when hsp90 is present. In fact, tumor-bearing mice treated with this therapy experienced complete tumor regression and long-term survival. These findings suggest that nanotube-mediated thermal treatment can eliminate both the differentiated cells that constitute the bulk of the tumor and the cancer stem cells that drive tumor growth and recurrence.
This work, which was supported in part by the National Cancer Institute, is detailed in a paper titled, "The resistance of breast cancer stem cells to conventional hyperthermia and their sensitivity to nanoparticle-mediated photothermal therapy." An abstract of this paper is available at the journal's website.