Presentation Authors: Melanie von Brandenstein*, Barbara Köditz, Caroline Eich, Sibel Cakir, Axel Heidenreich, Jochen W.U. Fries, Cologne, Germany
Introduction: Recently our group showed that Vim3, a truncated variant of Vimentin, is overexpressed in oncocytoma and can be used as differentiating marker. Normally Vim3 is a marker for cells with metastasizing potential. Nevertheless, we know from unpublished data that Vim3 is responsible for mitochondrial overproduction. Oncocytoma harbors increased nonfunctional mitochondria. The second, for the differentiation used protein is called Mxi-2, Mxi-2 is the truncated version of MAPK p38, a protein which is involved in several different processes. We could show that Mxi-2 is overexpressed in clear cell RCCs. Furthermore the mechanism leading to the truncation of both proteins is known and correlates with two miRs which could both be detected in patient urine. Since the analysis of miRs is quit time consuming we wanted to know if it is possible to identify the truncated proteins in urine samples.
Methods: Urine samples were accessed through our biobank (n=350). From 100 Âµl urine samples, proteins were isolated and Western blot was performed. Furthermore, 50Âµl of each urine sample were analyzed with ELISA either for the detection of Vim3 or Mxi-2. A lateral flow assay was developed for the detection of Vim3 in urine samples.
Results: With an ELISA a significant increase of Vim3 in urines from patient with oncocytoma (n=20) was detectable compared to all other subtypes of RCCs (chromophobe (n=50), papillary (n=40), clear cell RCC (n=200) and controls (n=40) (*p < 0.01, **p < 0.001, ***p < 0.0001). Mxi-2 was predominantly overexpressed in clear cell RCCs compared to all other subtypes. Lateral flow assay of Vim3 shows two bands in case of oncocytoma indicating specificity of this test.
Conclusions: Both truncated proteins (Vim3 and Mxi-2) were detectable in patient urine samples and can be used for the differentiation between benign and malignant RCCs. The lateral flow for Vim3 shows high specificity.