Cellular H- and M-type lactate dehydrogenase (LDH) isoenzymes and tumour diagnosis--an immunohistochemical assessment

Comparative Proteome Analysis of Breast Cancer Tissues Highlights the Importance of Glycerol-3-phosphate Dehydrogenase 1 and Monoacylglycerol Lipase in Breast Cancer Metabolism

BACKGROUND/AIM

Breast cancer (BC) incidence and mortality rates have been increasing due to the lack of appropriate diagnostic tools for early detection. Proteomics-based studies may provide novel targets for early diagnosis and efficient treatment. The aim of this study was to investigate the global changes occurring in protein profiles in breast cancer tissues to discover potential diagnostic or prognostic biomarkers.

MATERIALS AND METHODS

BC tissues and their corresponding healthy counterparts were collected, subtyped, and subjected to comparative proteomics analyses using two-dimensional gel electrophoresis (2-DE) and two-dimensional electrophoresis fluorescence difference gel (DIGE) coupled to matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF/TOF) to explore BC metabolism at the proteome level. Western blot analysis was used to verify changes occurring at the protein levels.

RESULTS

Bioinformatics analyses performed with differentially regulated proteins highlighted the changes occurring in triacylglyceride (TAG) metabolism, and directed our attention to TAG metabolism-associated proteins, namely glycerol-3-phosphate dehydrogenase 1 (GPD1) and monoacylglycerol lipase (MAGL). These proteins were down-regulated in tumor groups in comparison to controls.

CONCLUSION

GPD1 and MAGL might be promising tissue-based protein biomarkers with a predictive potential for BC.

Queuosine modification of tRNA: its divergent role in cellular machinery

tRNAs possess a high content of modified nucleosides, which display an incredible structural variety. These modified nucleosides are conserved in their sequence and have important roles in tRNA functions. Most often, hypermodified nucleosides are found in the wobble position of tRNAs, which play a direct role in maintaining translational efficiency and fidelity, codon recognition, etc. One of such hypermodified base is queuine, which is a base analogue of guanine, found in the first anticodon position of specific tRNAs (tyrosine, histidine, aspartate and asparagine tRNAs). These tRNAs of the ‘Q-family’ originally contain guanine in the first position of anticodon, which is post-transcriptionally modified with queuine by an irreversible insertion during maturation. Queuine is ubiquitously present throughout the living system from prokaryotes to eukaryotes, including plants. Prokaryotes can synthesize queuine de novo by a complex biosynthetic pathway, whereas eukaryotes are unable to synthesize either the precursor or queuine. They utilize salvage system and acquire queuine as a nutrient factor from their diet or from intestinal microflora. The tRNAs of the Q-family are completely modified in terminally differentiated somatic cells. However, hypomodification of Q-tRNA (queuosine-modified tRNA) is closely associated with cell proliferation and malignancy. The precise mechanisms of queuine- and Q-tRNA-mediated action are still a mystery. Direct or indirect evidence suggests that queuine or Q-tRNA participates in many cellular functions, such as inhibition of cell proliferation, control of aerobic and anaerobic metabolism, bacterial virulence, etc. The role of Q-tRNA modification in cellular machinery and the signalling pathways involved therein is the focus of this review.

Effect of TNF-alpha on Raji cells at different cellular levels estimated by various methods

Tumor necrosis factor (TNF)-alpha, a pleiotropic cytokine, has been shown to induce diverse and opposite effects on lymphoid malignancy depending on TNF receptor system expression. Based on this, we investigated its in vitro dose- and time-related effect on the malignant B-cell line Raji, derived from Burkitt lymphoma patients, at different intracellular levels. The membrane alteration was estimated by lactate dehydrogenase (LDH) release and by flow cytometry; intracellular metabolic energy by determination of the total intracellular LDH activity; total cytosole protein mass by sulforhodamine B assay; and cell growth by incorporation of [3H]thymidine into DNA. Significant increase of LDH through cell membrane alteration was accompanied by decrease of intracellular metabolized energy and total protein mass. TNF-alpha at lower concentrations (125 and 250 pg/ml) significantly induced cell proliferation in comparison with 1,000 pg/ml of TNF-alpha, which induced more cell death. TNF-alpha induced maximal apoptosis rate up to 30% after 24 h, showing more effects for a necrotic form of cell death. Here we reported opposite and diverse effects of TNF-alpha at different intracellular levels in Raji cells, when applied in different assays, showing characteristics for every cellular compartment.

The comparison of spontaneous LDH release activity from cultured PBMC with sera LDH activity in non-Hodgkin's lymphoma patients

Based on the fact that lactate dehydrogenase (LDH) enzyme is a very sensitive indicator of the cellular metabolic state, aerobic or anaerobic direction of glycolysis, activation status, and malignant transformation, in this study we compared values of the spontaneous LDH release from circulating PBMC with sera LDH activity in 53 different subtypes of non-Hodgkin's lymphoma (NHL) patients. Results shows that serum LDH was significantly (p < 0.05) elevated in comparison to the range values only in the advance clinical stage (III and IV) in all investigated subtypes of NHL according to The Working and REAL classification. On the other hand, the spontaneous LDH release from cultures PBMC is significantly (p < 0.01) elevated in early and advanced stage in all investigated forms of NHL in comparison to healthy controls. Based on consideration that an increase in spontaneous LDH release appears before elevated sera LDH activity, we conclude that determination of spontaneous LDH release by microassay from cultured cells together with other findings may help in the diagnosis of NHL patients, especially in patients with early stage of disease.

Biochemical changes in the efferent lymph plasma after oxazolone stimulation

The lymph node is a specialized microenvironment for the regulation of immune responses. The reticular network of the lymph node provides a structure that facilitates not only intercellular interactions, but the intranodal flow of lymph fluid. To assess biochemical changes in the nodal lymph plasma after antigen stimulation, prescapular lymph nodes in sheep were stimulated with the epicutaneous antigen oxazolone. The efferent lymph from both antigen-stimulated and contralateral control prescapular lymph nodes was continuously monitored for more than 120 h. The oxazolone-stimulated lymph plasma was associated with a selective increase in cholesterol content during the 'recruitment' phase of lymph node enlargement. The peak in cholesterol was followed closely by a significant increase in lymph plasma LDH concentration. In contrast, there was no significant difference between oxazolone-stimulated and control lymph plasma in the concentration of triglycerides, albumin, alkaline phosphatase, and alanine transferase. These selective biochemical changes in the efferent lymph appeared to reflect the dynamics of lymphocyte activation within the lymph node as well as provide a practical measure of the lymph node response to antigen stimulation.

Association of NK cell dysfunction with changes in LDH characteristics of peripheral blood lymphocytes (PBL) in breast cancer patients

The cytotoxic activity of NK (natural killer) cells is very important in immunological surveillance against the appearance and especially the spread of malignant disease. The aim of this study was to investigate the function of this subpopulation of cells in breast cancer patients in different clinical stages of disease prior to therapy. NK cell activity was determined in breast cancer patients and healthy controls by three different methods: standard 51-chromium-release assay and by the original colorimetric uncorrected and corrected lactate dehydrogenase (LDH) release assay. A discrepancy was shown between the assays, as the uncorrected LDH assay showed, not only, much higher values, but no stage-dependent depression in NK cell activity compared to the chromium-release assay. Further analyses of separately cultured peripheral blood lymphocytes (PBL) revealed that this difference arose from an increasing, clinical stage-dependent, spontaneous LDH release from PBL of breast cancer patients. Furthermore, a stage-dependent increase in intracellular LDH activity of PBL was found, although without difference in LDH-H and LDH-M isotype ratio, compared to controls. Increased spontaneous LDH release and intracellular LDH activity was more evident in young patients, under 40 years. Correction of the original LDH-release assay for the spontaneous LDH release activity from PBL present in the assay, gave values of NK cell activity comparable to those determined by the chromium assay and indicated that breast cancer patients have a significant depression in NK cell activity which correlates with the stage-dependent increase in spontaneous LDH release. Moreover, as both assays measure the secretory, perforin-mediated, NK cell cytotoxic pathway against tumor cells, it can be concluded that the appearance of spontaneous LDH release is an indicator of cell membrane damage which not only allows the loss of LDH, but also of the components of the secretory killing pathway, resulting in NK cell dysfunction with the progression of disease. The novel findings obtained in this work reveal the association of PBL membrane damage with clinical stage of breast cancer that can, aside from reflecting NK cell depression, underlie the defect in other PBL subsets and subsequently facilitate progression of the malignant process.

Lactate dehydrogenase (LDH) isoenzymes and proliferative activity of lymphoid cells--an immunocytochemical study

In a recent immunohistochemical study, we suggested that elevation of LDH isoenzymes is generally related to cell proliferation. To explore this relationship further, we have now examined the expression of H- and M-type LDH isoenzymes immunocytochemically in human resting and mitogen-activated B and T lymphocytes. In the resting state, T lymphocytes showed strong staining for H-type LDH but showed little or no staining for M-type LDH, while B lymphocytes showed only weak staining for M-type LDH. During activation of T cells, M-type LDH started to increase when cells entered the early stages of the cell cycle. The staining intensity increased to a maximum when the percentage of the T cells at the S/G2/M phases of the cell cycle reached its peak. M-type LDH expression declined when the activated T cells returned to their resting state. Staining for H-type LDH remained strong in T cells during activation. In B lymphocytes, both H- and M-type LDH isoenzymes increased concomitantly following activation and the staining intensity also correlated well with the percentage of the S/G2/M fraction. The expression of H- and M-type LDH was also determined in fresh leukaemia and a variety of lymphoid cell lines. It was noted that cells of chronic lymphocytic leukaemia (CLL) and pro-lymphocytic leukaemia (PLL), morphologically similar to normal lymphocytes, showed a LDH staining pattern resembling that of resting B lymphocytes, while lymphoblasts in T cell acute lymphoblastic leukaemia (T-ALL), high grade B cell lymphoma and Epstein-Barr virus (EBV) transformed cell lines showed a LDH staining pattern similar to that in activated T or B lymphocytes. Taken together, our results have demonstrated a significant correlation between expression of LDH and proliferative activity of cells. Immunostaining with the MoAbs to H- and M-type LDH can, therefore, provide a useful means not only for identification of T and B lymphocytes but also for rapid evaluation of the proliferating fraction of normal and neoplastic human cell populations.