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 (H2 O2 ) levels from H2 O2 -releasing drugs causes their death. We therefore explored whether the tumoricidal effect of hWJSCs on
lymphoma cells was mediated via H2 O2 . 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, 100 kDa) for 48 h. Since, the 3 kDa-MWCO concentrate showed the greatest cell inhibition we then investigated whether the tumoricidal effect of the specific 3 kDa-MWCO concentrate on two different
lymphoma cell lines (Ramos and Toledo) was mediated via accumulation of H2 O2 . 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-3 kDa 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. H2 O2 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-3 kDa MWCO concentrate regulates cellular H2 O2 leading to a tumoricidal effect and may thus be a promising anti-
lymphoma agent. J. Cell. Biochem. 117: 2045-2055, 2016. © 2016 Wiley Periodicals, Inc.