A new imaging technique called optical metabolic imaging may be able to identify subtypes of cancer and also measure how tumors respond to drug treatments, according to a new study published in Cancer Research.

Researchers from Vanderbilt University in Tennessee used a custom-built, multiphoton microscope alongside a titanium laser to study whether metabolic activity in certain cancers could be visualized.

Cell metabolism is a good way to measure how well anti-cancer drugs are working, since cancerous cells consume more sugar for energy than normal cells.
By using new infrared laser technology, researchers were able to visualize two types of molecules involved in cellular metabolism — nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) — which naturally emit fluorescence when they are exposed to certain forms of light.

Researchers could then differentiate between cancerous and normal cells by measuring different levels of fluorescence in the cells. Furthermore, they could use this technique to identify different cancer cell types.

Researchers administered an anti-cancer drug to three breast cancer cell lines that respond differently to the drug. They found drug-sensitive cells exhibited lower levels of fluorescence following the treatments, while drug-resistant cells were unaffected.

The team then grew human breast tumors in live mice, and treated some of the mice with the anti-cancer drug. By using optimal metabolic imaging on the mice, researchers could measure a noticeable difference in fluorescence between drug-sensitive and drug-resistant tumors only two days after the first dose of the drug.

"The most surprising thing was how early we were able to detect the response — we knew it would be sensitive to the drug treatment but we didn't know it would be sensitive at such an early time point," said Melissa Skala, assistant professor of biomedical engineering and co-author of the study.

Throughout the study, this new imaging technique was compared against the standard cancer imaging technique, FDG for PET, which was not able to measure any response differences throughout the full 12-day experiment.

Researchers hope to one day use this imaging technique in endoscopes for live imaging for human cancers.

"We're working on clinical samples to see if this works on human tumors for patients — the hope is to have a screen for multiple drugs before the patient is treated so we can determine the best treatment course for each patient," said Skala.

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