People with elevated levels of protein prostasin seem to have a higher risk of developing diabetes and dying from cancer, according to a large, prospective, population-based study. The finding may provide new insights into why people with diabetes have an increased risk of cancer.
The study claims to be the first to investigate the link between plasma prostasin levels and cancer mortality, the study authors wrote in Diabetologia. The study analyzed plasma prostasin samples from 4,297 older adults (average age, 57.5 years) from the Malmö (Sweden) Diet and Cancer Study Cardiovascular Cohort.
Dr. Gunnar Engström
“This study from the general population shows that prostasin, a protein that could be measured in blood, is associated with increased risk of developing diabetes,” senior author Gunnar Engström, MD, PhD, professor of epidemiology at Lund University in Malmö, Sweden, said in a comment. “Furthermore, it was associated with increased risk of death from cancer, especially in individuals with elevated glucose levels in the prediabetic range.
“The relationship between diabetes and cancer is poorly understood,” Dr. Engström said. “To our knowledge, this is the first big population study of prostasin and risk of diabetes.”
He noted previous studies have found a relationship between prostasin and cancer outcomes. “Prostasin could be a possible shared link between the two diseases and the results could help us understand why individuals with diabetes have increased risk of cancer.”
Patients in the study were assigned to quartiles based on prostasin levels. Those in the highest quartile had almost twice the risk of prevalent diabetes than did those in the lowest quartile (adjusted odds ratio, 1.95; 95% confidence interval, 1.39-2.76; P < .0001).
During the follow-up periods of 21.9 years for diabetes and 23.5 years for cancer, on average, 702 participants developed diabetes and 651 died from cancer. Again, the analysis found a significantly higher adjusted hazard ratio for participants in the fourth quartile: about 75% higher for diabetes (HR, 1.76; 95% CI, 1.41-2.19; P < .0001), and, after multivariable analysis, about 40% higher for death from cancer (HR, 1.43; 95% CI, 1.14-1.8; P = .0008).
Potential diabetes-cancer ‘interaction’
The study also identified what it called “a significant interaction” between prostasin and fasting blood glucose for cancer mortality risk (P = .022). In patients with impaired fasting blood glucose levels at baseline, the risk for cancer mortality was about 50% greater with each standard deviation increase in prostasin (HR, 1.52; 95% CI, 1.07-2.16; P = .019). Those with normal fasting blood glucose at baseline had a significantly lower risk with each SD increase in prostasin (HR, 1.11; 95% CI, 1.01-1.21; P = .025).
Further research is needed to validate the potential of prostasin as a biomarker for diabetes and cancer risks, Dr. Engström said. “The results need to be replicated in other studies. A study of cancer mortality in a big cohort of diabetes patients would be of great interest. We also need to examine whether prostasin is causally related to cancer and/or diabetes, or whether prostasin could act as a valuable risk marker in clinical settings. If causal, there could a possible molecular target for treatment.”
He added: “Biomarkers of diabetes and cancer are of great interest in the era of personalized medicine, both for disease prevention and for treatment of those with established disease.”
Dr. Li-Mei Chen
Li-Mei Chen, MD, PhD, a research associate professor at the University of Central Florida, Orlando, has studied the role of prostasin in epidemiology. She noted that one of the challenges of using prostasin in clinical or research settings is the lack of a standardized assay, which the Malmö study acknowledged. Dr. Engström and colleagues wrote that “prostasin levels were measured in arbitrary units (NPX values), and thus could not be compared directly with absolute values.”
Dr. Chen pointed out that the study reported a lower range of 0.24 pg/mL and an upper range of 7,800 pg/mL.
This means that, “in different groups that measure prostasin, the absolute quantity could have a difference in the thousands or tens of thousands,” she said. “That makes the judgment difficult of whether for this person you have a high level of prostasin in the blood and the other one you don’t if the difference is over a thousandfold.”
The Malmö study used the Proseek Multiplex Oncology I panel to determine plasma prostasin concentration, but Dr. Chen noted that she couldn’t find any data validating the panel for measuring prostasin. “It’s really hard for me to say whether this is of value or not because if the method that generated the data is not verified by another method, you don’t really know what you’re measuring.
“If the data are questionable, it’s really hard to say whether it means whether it’s a marker for cancer or diabetes,” Dr. Chen added. “That’s the biggest question I have, but actually the authors realize that.”
Dr. Engström confirmed that, “if prostasin is used to identify patients with increased risk of diabetes and cancer mortality, we also need to develop standardized assays for clinical use.”
Dr. Engström and coauthors had no disclosures. The study received funding from the Swedish Heart Lung Foundation, the National Natural Science Foundation of China, and the Natural Science Foundation of Jiangsu Province. The Malmö Diet and Cancer study received grants from the Swedish Cancer Society, the Swedish Medical Research Council, AFA Insurance, the Albert Påhlsson and Gunnar Nilsson Foundations, Malmö City Council, and Lund University. Dr. Chen had no relevant disclosures.