In experiments with laboratory mice that bearaggressive human breast cancers, UC Davis researchers have used hotnanoprobes to slow the growth of tumors — without damage to surroundinghealthy tissue. The researchers describe their work in the March issue ofthe Journal of Nuclear Medicine.
“We have demonstrated that the system is feasible in laboratory mice. Thenext step will be clinical testing in patients,” said Sally DeNardo, aprofessor of internal medicine and radiology at UC Davis and lead author ofthe study.
Many researchers have studied heat as a potential treatment for cancer, butthe difficulty of confining heat within the tumor and predicting aneffective heat dose has limited its use. The UC Davis research, carried outin collaboration with scientists from Triton BioSystems in Boston, seeks tosolve this problem.
The experimental system uses bioprobes created by wedding magnetizediron-oxide nanospheres to radiolabeled monoclonal antibodies. The bioprobesare cloaked in polymers and sugars that render them nearly invisible to thebody’s immune system.
DeNardo and her colleagues infused trillions of the probes — more than10,000 can fit on the end of a straight pin — into the bloodstreams oflaboratory mice bearing human breast tumors. Once in the bloodstream, theprobes began to seek out and latch onto receptors on the surface ofmalignant cells.
Three days later, the team applied an alternating magnetic field to thetumor region, causing the magnetic nanospheres latched onto the tumor cellsto change polarity thousands of times per second, instantaneouslygenerating heat. As soon as the AMF stopped, the bioprobes cooled down.
Mice in the study received a series of AMF bursts in a single 20-minutetreatment. Dosing was calculated using an equation that included tumorconcentration of bioprobes, heating rate of particles at differentamplitudes, and the spacing of AMF bursts.
Tumor growth rate slowed in the treated animals, a response that correlatedclosely with heat dose. No toxicity related to the bioprobes was observed.
“Using heat to kill cancer cells isn’t a new concept,” DeNardo said. “Thebiggest problems have been how to apply it to the tumor alone, how topredict the amount needed and how to determine its effectiveness. Bycombining nanotechnology, focused AMF therapy and quantitative molecularimaging techniques, we have developed a safer technique that could joinother modalities as a treatment for breast and other cancers.”