Media conditioned for extended period with APP over-expressing CHO cells have greater inhibitory effect on tumor cell proliferation. MDA-MB231-L cells, B16F-L cells (500 cells/well), 7W and CHO cells (1000 cells/well) were seeded in separate 96 well plates. 7W and control CHO cells were grown for 36 hr, 60 hr and 84 hr before the media were harvested for incubation with tumor cells. The number of tumor cells was measured by BLI assay at 24 hr post medium replacement. (A) A representative image of MDA-MB231-L cells was acquired at 24 hr after the media were replaced with media conditioned with CHO or 7W cells for 36, 60 or 80 hr. (B) The relative number of cells grown in CM from 7W vs. CHO was calculated by dividing MDA-MB231-L cells grown in 7W-CM by those in CHO-CM. The values represent means ± SEM (n = 6), and the difference is statistically significant compared to cells in 36 hr-CM, as indicated by * P < 0.05.