Citrate shows specific, dose-dependent lympholytic activity in neoplastic cell lines

We have demonstrated cell membrane destruction activity by carboxylic acid derivatives (CADs) mainly tri-sodium citrate, in neoplastic cell lines and, to a far lesser extent, in normal human peripheral blood mononuclear cells (hPBMC). Flow cytometric (FACS) analysis was applied to Annexin-V and Propidium Iodide (PI) stained cells to evaluate the degree of the apoptosis induced by citrate in the following cell lines: CCRF-CEM (shortened to CEM), H9, and Jurkat (T-Cells), Raji and WIL2-NS (B-Cells), HL-60 (myeloblasts), K562 (myelocytes) and U937 (monocytes). We also tested normal hPBMC. Before staining with Annexin/PI, manual cell counts were performed on 24- and 48-h-old cell cultures. Cell supernatants were assayed for lactate dehydrogenase (LDH). LDH values in samples correlated with enhanced apoptosis by FACS analysis. For comparison, ascorbate and 2 other CADs including, acetate and lactate were also evaluated for the induction of apoptosis. In addition, the ability of tri-sodium citrate to induce apoptosis in the presence and the absence of several antineoplastic drugs, such as dexamethasone, arsenic trioxide, hydrocortisone, 6-mercaptopurine, and methotrexate were tested on Jurkat cells. FACS, LDH, and cell count values all demonstrated an enhanced degree of apoptotic cell death in Jurkat cells by citrate. In most of our investigated cells, except for the H9 cell line, citrate has induced a greater degree of apoptosis than acetate which induced a greater degree than lactate (see Fig. 1.0). The nature of the cell death by ascorbate appeared to be due to necrosis rather than apoptosis. Pilot studies on normal hPBMC showed that citrate alone or in combination with antineoplastic drugs caused minimal cell death. Thus citrate might be of benefit in some chemotherapy treatments in order to reduce drug toxicity or possibly enhance drug activities in certain neoplasias.