Determination of pyruvate kinase type tumor M2 in human renal cell carcinoma: a suitable tumor marker?

Renal cell carcinoma (RCC) expresses an isoform of the glycolytic enzyme pyruvate kinase (type M2). The dimeric form (TuM2-PK) is over expressed in tumor cells and is detectable in blood with a sensitive enzyme-linked immunosorbent assay (ELISA). The aim of the present study was to evaluate the clinical value of TuM2-PK as a tumor marker for RCC. The TuM2-PK concentration in EDTA-plasma was determined quantitatively and immunologically using an ELISA. We measured the TuM2-PK plasma levels of 83 patients before and after surgery. Ninety-seven patients with various non-malignant diseases were also recruited as a control group. The control group displayed mean levels of 11.37 U/ml of TuM2-PK. Values were elevated in patients with RCC prior to surgery (mean 21.88 U/ml). The plasma levels increased after surgery until day 5 (mean 53.97 U/ml). At day 10, marker levels started to decrease without reaching preoperative values (mean 43.5 U/ml). Plasma levels in the renal vein (obtained during surgery) were not different from those in the peripheral blood. Follow-ups after 2–6 months showed a decrease to below preoperative levels (mean 16.3 U/ml). A significant difference was obtained by comparing the patients according to their Robson score. We found a significant difference (P<0.01, Wilcoxon's two-sample test) in TuM2-PK levels between patients with RCC and the control group. Nevertheless, using the manufacturer's recommended cut-off value (15 U/ml), sensitivity was only 50.6% and specificity was 80.4%. Our results suggest that TuM2-PK is not a suitable tumor marker for RCC.