In vitro characterization of several bacterial strains’ properties on human tumor cells

MOLINA MA; AZPIROZ MB; LOMBARDO T; ÁLVAREZ EMC; CASTRO MS; MANGHI MA

Ciudad Autónoma de Buenos Aires

Congreso; First French-Argentine Immunology Congress (FAIC); 2010

Sociedad Argentina de Inmunología, Sociedad Francesa de Inmunología, Grupo Rioplatense de Citometría de Flujo, Sociedad Argentina de Pediatría

Our laboratory studies the immunomodulatory effects of the probiotic strain Enterococcus faecalis CECT7121, which shows anti-tumor effects on several models, either by direct inhibition of tumor cell proliferation as well as by stimulating the anti-tumor immune response. The aim of this work was to investigate the in vitro effects of several E. faecalis strains on 2 tumor cell lines: Raji and PL104. Stimuli employed included whole cell bacteria, purified cell walls, soluble lysates, and culture supernatant. Also, on PL104 cells, combinatory assays were performed with CAPE (anti-tumor drug). The tumor cells’ proliferation was determined by (3)H-thymidine uptake assays, on 48 h cultures. Our results show that Raji cell proliferation was inhibited in a dose-dependent manner by both whole cell bacteria and purified cell walls (ANOVA, ***p<0.001). These observations are shared by the different E. faecalis strains tested, but not when a Micrococcus luteus strain was employed as stimulus (different cell wall components). This inhibitory effect could not be achieved employing culture supernatants, indicating that the active compounds are not released to the culture media. In these studies, the strain E. faecalis CECT7121 showed the highest effect, comparing with the other Enterococcus strains (63%; ANOVA, **p<0.01). E. faecalis CECT7121, as well as its purified cell wall and soluble lysate, showed a dose-dependent inhibition on PL104 cell proliferation, specially when employing bacterial soluble compounds (ANOVA, ***p<0.001). These components, combined with CAPE, achieved a synergic effect on the inhibition of PL104 cells, as determined by the construction of an isobologram. Our results suggest that several bacterial components have an inhibitory effect on different hematological tumor cell lines. Further studies should be performed to identify and isolate the active components involved, and to characterize its behavior in several combinatory treatments.