With the advent of a new fluorescent spray used during surgery, doctors can visualize tumors with their naked eyes.

Scientists at the University of Tokyo published an article on November 23, 2011 in Science Translational Medicine disclosing a study for a new spray that causes carcinomas to glow green, facilitating more accurate and thorough tumor removal.

The spray consists of a gamma-glutamyltranspeptidase-activated fluorescent probe, which is expressed by rapid one-step cleaving of glutamate with gamma-glutamyltranspeptidase (γ-GGT). This enzyme is not expressed in normal tissue, but is overexpressed on the cell membrane of various cancer cells. The fluorescent property of the probe is activated during passage into the cancerous cell, such that the probe only glows green once inside the diseased tissue. Through this process, cancerous cells glow twenty times brighter than surrounding cells, allowing surgeons to clearly visualize the precise locations and borders of cancerous tissue in the patient.

This study has significant and exciting implications for patients with a variety of cancers. With some cancers, like colon or breast, doctors are able to remove excess tissue surrounding tumors to ensure complete cancer removal. However, for brain cancer the tissue removal must be more precise to avoid removing functional tissue surrounding the diseased area. Thus, the surgeon must know the precise foci and accurate borders between the cancer and normal tissue during surgery or endoscopy. This new fluorescent probe makes such accuracy possible.

Furthermore, many cancers have a tendency to spread rapidly, leaving small tumors (less than one millimeter in size) scattered around the abdominal cavity or other diseased area. While magnetic resonance imaging (MRI) and the naked eye can detect larger tumors, these tiny deposits of cancerous tissue can often go undetected. With this new probe, doctors can readily visualize even the smallest tumors during the course of the surgery, ensuring complete cancer removal.

This precision may in turn obviate the need for chemotherapy or radiation treatments, which are currently employed to wipe out the smaller tumors that doctors may have missed during surgery. While MRI may still be used to identify the general cancerous area and larger tumors, the γ-GGT probe may ultimately facilitate complete cancer removal without the need for supplementary treatments, many of which, though effective, have significant deleterious side effects.

This is not the first attempt scientists have made in experimenting with glowing cancer cells. Earlier this month, scientists experimented with an injectable drug that causes a build-up of fluorescent chemicals in brain tumors, making them glow pink. That process, however, takes several hours between the initial injection and the subsequent tumor visualization. Other tumor imaging procedures can take up to several days to take effect. In lab studies, the γ-GGT probe spray achieved rapid fluorescence in less than ten minutes in vitro, and in less than one minute in mice injected with human ovarian tumors.

Japanese scientists conducting this study have yet to identify any serious side effects to administering this spray, and are hopeful that the probe will be used in hospitals within the next few years.