[Lactate dehydrogenase (LDH) in peripheral blood lymphocytes (PBL) of patients with solid tumors]

Serum LDH level is a prognostic factor in different malignancies as its increase reflects tumor mass and response to therapy. Serum LDH is the consequence of the disruption of the cell membrane of a large fraction of dividing malignant cells whose metabolic hallmark is anaerobic glycolysis that leads to increased LDH enzyme activity. Moreover, as we have previously shown that spontaneous LDH release from cells represents a measure of cell membrane damage, and this parameter is used for the estimation of cell destruction in cytotoxic assays, the aim of this study was to evaluate the characteristics of LDH activity of PBMC of patients with different solid tumors (non-Hodgkin's lymphomas--NHL, n=47; Hodgkin's disease--HD, n=45; ovarian cancer--OvCa, n=6; breast cancer--BrCa, n=34; thyroid cancer--TyCa, n=3; cancer of PVU--CaPVU, n=4 and head & neck--H&N, n=6) in all clinical stages of NHL and HD and in advanced clinical stages of disease for BrCa, OvCa, CaPVU and H&N. Spontaneous LDH release from PBMC was determined by the spectrophotometric method from supernatants of 8 x 10(6)/ml PBMC cultured for 2 h in RPMI 1640 without phenol red using and LDH substrate mixture. The total LDH activity was determined after lysis of PBMC by ultrasound. The obtained results indicate that PBMC in all the investigated malignancies, compared to control PBMC, demonstrate a significant increase (p<0.01) in spontaneous LDH release act, which correlates with advanced clinical stage in all malignancies except in Hodgkin's disease, in which the spontaneous LDH release was increased in all clinical stages. Contrary to this, the total LDH activity was not increased in PBMC in all investigated tumors. However, the "percent of spontaneous LDH release" was always increased, regardless of the total LDH activity, indicating that spontaneous LDH release is the consequence of PBMC membrane damage present in advanced stages of different solid tumors.