Urine concentrations of two tumor-specific proteins may have “substantial potential” for detecting renal cell carcinoma (RCC) in some patients, a new study suggests.

Researchers evaluated the clinical utility, sensitivity and specificity of urine aquaporin-1 (AQP1) and perilipin-2 (PLIN2) concentrations for renal cell carcinoma screening.
“Our findings validate the clinical utility of urine AQP1 and PLIN2 as biomarkers with applicability for early and noninvasive detection and screening for renal cell carcinoma, as well as differential diagnosis of imaged renal masses,” Dr. Jeremiah J. Morrissey of Washington University in St. Louis, Missouri told Reuters Health by email.

In a March 19 online paper in JAMA Oncology, Dr. Morrissey and colleagues note that today, the only way to screen for renal masses are with computed tomography (CT) and magnetic resonance imaging (MRI).

In previous studies, they have shown that AQP1 and PLIN2 are sensitive and specific in the early detection of clear cell or papillary subtypes of kidney cancer.

For the current work, they analyzed urine samples from 720 patients undergoing routine abdominal CT, plus 19 patients with confirmed RCC and 80 healthy controls.

Urine AQP1 and PLIN2 concentrations were significantly higher in the RCC group than in the healthy controls and in the main screening population.

Corresponding AQP1 median concentrations, normalized to urine creatinine concentration, were 225.0 ng/mg for the RCC group, 1.1 ng/mg in healthy controls, and 0.5 ng/mg in the screening population. For PLIN2, concentrations were 37.8, 3.1 and 0 absorbance U/mg.
Increases in urinary AQP1 concentration in combination with PLIN2 concentration resulted in 95% sensitivity and 98% specificity (area under the receiver operating characteristic curve, 0.990) in detecting RCC in validation studies.

In the screening population, three patients had biomarker concentrations suggestive of RCC and CT scans showed renal masses. Two had pathologically confirmed RCC in further evaluation.

The results are encouraging, but the researchers point out that “while AQP1 measurement is by ELISA and presently applicable for screening and diagnosis, the cumbersome nature of Western blotting precludes application of PLIN2 measurement to large-scale investigations or RCC screening.”

Dr. Brian I. Rini, coauthor of an accompanying editorial, told Reuters Health by email, “I think this article highlights both the promise and the challenge of developing clinically useful biomarkers.”

Dr. Rini, of the Cleveland Clinic Taussig Cancer Institute, Ohio concluded, “The authors show an association between their measured markers and RCC, although much more work needs to be done before these can be incorporated into daily practice.”

The Barnes-Jewish Hospital Foundation, Washington University School of Medicine, and the National Cancer Institute supported this research. Washington University holds a European patent on use of AQP1 to diagnose kidney cancer.