As a medical student Alex Kentsis was interested in the structure of proteins, so during residency he decided to see if he could use the emerging science of proteomics to discover biomarkers for common diseases. He chose to focus on urine since it is easily obtained and asked whether any specific changes in the urine occur in patients with appendicitis. The result, published recently in the Annals of Emergency Medicine, and featured nationally in stories in Time Magazine, in the Los Angeles Times and on BBC News, showed that several proteins had a high predictive value and that one, leucine-rich alpha-2-glycoprotein (LRG), was particularly predictive. LRG was enriched more than 9-fold in the urine of patients with appendicitis and the amount correlated with the severity of the disease. Sensitivity and specificity approached 100% (the receiver operating characteristic area was 97%). LRG was highly concentrated in the inflamed appendices. It is normally expressed in differentiating neutrophils, liver, and the high endothelial venules of the mesentery, including the appendix, and functions in leukocyte activation and chemotaxis, which may explain its specificity. Notably, the test was positive even in some patients with early appendicitis who had normal CT and ultrasound imaging. Preliminary testing indicates that elevated levels of LRG are also easily detected in the urine of patients with appendicitis by western blotting, which means that it should be possible to develop a dipstick immunoassay for rapid testing.
The study was paid for by funds set aside for resident research. It was greatly facilitated by the state-of-the-art proteomics facility at Boston Children's Hospital and by the enthusiasm and cooperation of Hanno Steen, who runs that facility, and the emergency room staff. With the multiple different mass spectrometers available and the other protein fractionation equipment, Alex was able to survey over 2000 unique urine proteins to identify his biomarkers. With such a large protein palette, it seems inevitable that markers of other diseases will soon be found.
Alex Kentsis is currently a fellow in hematology/oncology at Boston Children's Hospital and the Dana-Farber Cancer Institute.