Plasma glutamate–a prognostic marker of cancer and of other immunodeficiency syndromes?

Abstract

Elevated plasma levels of glutamate (GLU) have been reported to occur in patients with malignancies and other immunodeficiency syndromes (IDS). To evaluate, whether GLU is useful as prognostic indicator, the plasma concentrations were determined in patients with colorectal carcinoma (CRC), with breast cancer (BRC), and with HIV-infection (HIV). The results were correlated with the disease-stages, and compared with data obtained from patients with benign diseases of the same organ, as well as from sex-matched healthy volunteers. GLU concentrations (volunteers: 27.4 +/- 17.6 mumol/l) were elevated in all BRC patients (range of mean values: 53.5-83.2 mumol/l), in CRC patients with T2-T4-tumours (means: 46.8-85.9), and in HIV+ patients of stage WR 5, 6 (means: 53.9-69.7 mumol/l). All CRC- and BRC-patients with metastases showed highly significant elevations of GLU concentrations (p less than 0.001), but there were no direct correlations between disease stages and GLU levels. Pre-operative patients with benign diseases (diverticulitis, adenoma = GID; and mastopathy = MTP) showed increased GLU levels, which were comparable to those of the tumour patients. The glutamine/GLU ratios (volunteers: 19.3 +/- 15.0) were decreased only in HIV-WR 6 (7.6 +/- 2.1), and BRC-stage 4 (8.0 +/- 1.7). From these results we deduce that the plasma GLU concentrations do not allow a discrimination either between patients with malignancies and without, and between persons of different disease stages.

Serum Concentration of Free Amino Acids in Dogs Suffering From Perianal Tumours

“…Previous studies in humans have revealed that glutamic acid concentration increases in tumour tissue when compared to unaffected tissues, and these changes are strongly related to advancement of malignancy stage of the neoplastic process (19,22,23). Similar results were reported in studies on dogs with mammary gland tumours and skin tumours, where evaluation of amino acids in malignant tumour tissues and serum has shown increased glutamic acid concentration in both these compartments when compared to healthy controls.…”

Glutamate Released by Dendritic Cells as a Novel Modulator of T Cell Activation

“…In fact, a significant number of clinical studies have consistently shown strong correlation between immunodeficiency, such as occurs in AIDS (16 -18) or in malignancies (19,20), and the deregulation of plasma glutamate levels. However, both the cells producing glutamate and the physiological mechanisms underlying glutamate actions in the immune response remain far from being elucidated.…”

Glutamine and Glutamate in Ascitic Fluid of Dogs

“…The glutamate concentration is higher in malignant and purulent effusions and lower in cardial and cirrhotic effusions. This may be due to incomplete deamidation of glutamine to glutamate as a result of hypoxia (8), and the secretion of glutamate by tumour cells (8,9). Glutamine can also be converted into glutamate by macrophages and fibroblasts (10).…”