Dr. Johnson’s team analyzed frozen tumor tissue collected between 1991 and 2001. They examined metabolic differences in normal tissue compared to tumor tissue and also compared tissue from patients with early-onset and late-onset colorectal cancer. The team found that 91 metabolites were significantly altered between normal tissue and colorectal cancer tumor tissue. Of these, only one metabolite called homovanillic acid—a molecule produced during the breakdown of dopamine—was uniquely decreased in early-onset tumors. Dopamine levels are used clinically to screen for several kinds of cancerous tumors.
“Right now, we don’t know if homovanillic acid has any direct effect on the colon or colon cancer, but it could potentially be a marker for disruption to dopamine metabolism,” Dr. Johnson said.
Dr. Johnson’s lab plans to further investigate the dopamine pathway to determine how it may be altered in early-onset colorectal cancer. The lab is collecting samples at Yale New Haven Hospital to test if their findings are consistent across a larger cohort of patients. They also hope to validate their findings, not just in tumor tissue, but in blood samples.
The research is unique, Johnson said, because finding frozen tumor tissues for study is extremely difficult. “Normally in pathology, they’ll take the tumor and put it into paraffin, but in order to look at metabolites, you need to have the tumors frozen,” she said. “It’s actually quite hard to find biobanks that have frozen tissue.”