Capturing the Physiologic Mechanisms of Early Stage Cancer with 3D Multi-Photon Fluorescence Microscopy

Researchers from Duke University's Pratt School of Engineering (Durham, NC, USA) reported that their findings in animals also suggest that the so-called multi-photon fluorescence microscopy--a technique that had generally been limited to the basic science laboratory--might also find a use in the clinic.

"We were able to capture physiological information about tissue in a living and breathing animal, in three dimensions,” said Dr. Nirmala Ramanujam, an associate professor of biomedical engineering. "We peered into individual cells in a very non-invasive way to see how things change as early cancer progresses.” The ability to examine live tissue is critical because tissue removal erases metabolic features that are hallmarks of cancer, added Dr. Melissa Skala, a former doctoral student in Dr. Ramanujam's laboratory.

Drs. Ramanujam and Skala's findings were published online November 19, 2007, in an early edition of the journal Proceedings of the U.S. National Academy of Sciences (PNAS). The microscope used in the new study is just one of several light-based, or photonic devices Dr. Ramanujam's group is investigating for their potential to identify biomarkers indicative of cancer.

Multi-photon microscopy utilizes pulses of laser light to excite molecules with the natural capacity to give off light, or fluoresce. In the new study, the researchers used the imaging technique to examine cell structure in fine detail and to quantify the relative amounts of two important metabolic coenzymes based on their fluorescence intensity. That ratio provides information about a cell's metabolic rate and oxygen supply, the researchers explained.

They also measured the coenzymes' "fluorescence lifetime”--the amount of time before they give off light--giving additional, though less well understood, insight into the metabolic environment within cells, according to Dr. Ramanujam.

The researchers captured images of cells in the cheek pouches of almost two dozen hamsters, including several cancer-free animals and others at various stages of early oral cancer. Those images revealed significant differences in the structural and metabolic characteristics of early cancer versus non-cancer. Their studies suggested that the fluorescence lifetime is the best indicator of pre-cancer state, making it a promising new way of disease detection.

"There is always a need to identify new biomarkers for cancer or for monitoring the response to cancer therapy,” Dr. Ramanujam said. "Our goal is to leverage biophotonics to compare well-established markers of cancer to ones that have yet to be exploited.”

While existing multiphoton microscopes themselves could be evaluated in the clinic, Dr. Ramanujam reported that her team's goal would be to design and construct simple devices that are customized for medical use.


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Duke University's Pratt School of Engineering