Human Umbilical Cord Wharton's Jelly Stem Cell Conditioned Medium Induces Tumoricidal Effects on Lymphoma Cells Through Hydrogen Peroxide Mediation

Several groups have reported that human umbilical cord Wharton's jelly stem cells (hWJSCs) possess unique tumoricidal properties against many cancers. However, the exact mechanisms as to how hWJSCs inhibit tumor growth are not known. Recent evidence suggests that exposure of cancer cells to high hydrogen peroxide (H2O2) levels from H2O2-releasing drugs causes their death. We therefore explored whether the tumoricidal effect of hWJSCs on lymphoma cells was mediated via H2O2. We first exposed lymphoma cells to six different molecular weight cut-off (MWCO) concentrates of hWJSC-conditioned medium (hWJSC-CM) (3, 5, 10, 30, 50, 100kDa) for 48h. Since, the 3kDa-MWCO concentrate showed the greatest cell inhibition we then investigated whether the tumoricidal effect of the specific 3kDa-MWCO concentrate on two different lymphoma cell lines (Ramos and Toledo) was mediated via accumulation of H2O2. We used a battery of assays (MTT, propidium iodide, mitochondria membrane potential, apoptosis, cell cycle, oxidative stress enzymes, hydrogen peroxide, mitochondrial superoxide, hydroxyl radical, peroxynitrile anion, and lipid peroxidation) to test this mechanism. The hWJSC-CM-3kDa MWCO concentrate significantly decreased cell viability and mitochondrial membrane potential and increased cell death and apoptosis in both lymphoma cell lines. There were significant increases in superoxide dismutase with concomitant decreases in glutathione peroxidase, catalase, and thioredoxin peroxidase activities. H2O2 levels, mitochondrial superoxide, hydroxyl radical, peroxynitrile anion, and lipid peroxidation were also significantly increased in both lymphoma cell lines. The results suggested that the hWJSC-CM-3kDa MWCO concentrate regulates cellular H2O2 leading to a tumoricidal effect and may thus be a promising anti-lymphoma agent. J. Cell. Biochem. 117: 2045-2055, 2016. (c) 2016 Wiley Periodicals, Inc.