Streptococcus gallolyticus subsp. gallolyticus promotes colorectal tumor development
Human colon cancer cell lines HCT116 (A), HT29 (B), LoVo (C), SW480 (D), and SW1116 (E), human lung cancer cell line A549 (F), human kidney epithelial cell line HEK293 (G), and normal human colon epithelial cell lines CCD841CoN (H) and FHC (I) were tested. Cells were seeded into the wells of 6-well plates at 1x104 cells per well and incubated for 12 hours. Stationary phase bacteria were washed with sterile phosphate buffered saline, pH 7.4 (PBS) and resuspended in the appropriate cell culture media. Bacterial suspension or media only were then added to the wells at 1x102 cfu/well, and incubated for 24 or 48 hours. Cells were stained with trypan blue and counted in an automated cell counter. Each experiment was done with duplicate wells and repeated at least three times. Data are presented as the mean ± standard error of the mean (SEM). Two-way, two-tailed analysis of variance (ANOVA) followed by Student-Newman-Keuls (SNK) test was used to analyze the data. Significance shown in panels A-C is for comparison between cells co-cultured with TX20005 and those with L. lactis. *, p < 0.05; **, p < 0.01.