A new method for visualizing tumor growth using glowing mice is shedding light on the formation and spread of cancer.
Researchers from the University of North Carolina Lineberger Comprehensive Cancer Center have developed a strain of mice that essentially turns on a gene that fireflies have when the normal p16 gene--which plays a role in aging and cancer suppression--is activated. In cells undergoing senescence--a tumor defense mechanism--the p16 gene is switched on, causing the affected tissue to glow.
As the mice got older, the progression of p16 increased, making the mice brighter. Sites of cancer formation became extremely bright, which allowed researchers to identify developing cancer at an early stage.
Researchers tracked the accumulation of senescent cells in aging mice by assessing how brightly each mouse glowed. Surprisingly, they found that the brightest animals were no more likely to die from spontaneous cancer than dimmer animals of the same age. In other words, the number of senescent cells in the mouse was not an accurate predictor of death.
"With these mice, we can visualize in real-time the activation of cellular senescence, which prevents cancer but causes aging," said Professor and Deputy Cancer Center Director Norman Sharpless. "We can literally see the earliest molecular stages of cancer and aging in living mice."
The luminescent mice could also help scientists better understand how cancers form. In the earliest stages of cancer, expression of p16 is activated to suppress cancer. Typically, this works to block the cancer, but sometimes this tumor suppressor fails and tumors develop while still activating the p16 gene. In the UNC study, all tumors forming in the mice glowed strongly, allowing researchers to monitor early tumor formation in different cancer types.
The research, which was published in the Jan. 18 issue of Cell, holds promise for humans. The modified mice are already being used by scientists at UNC and other institutions to identify early cancer development and to study how tumors respond to anticancer treatments. The researchers believe similar approaches to monitoring senescence can be developed in order to study aging and tumor development in people.
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