Objective      To investigate the effect of bone marrow-derived mesenchymal stem cells (BD-MSCs) on the proliferation and migration of colorectal cancer cell line HT29 and to study the possible mechanism.       Methods      HT29 cells co-cultured with BD-MSCs were defined as a co-culture group

and HT29 cells cultured alone were selected as a control group. The cell migration was detected by Transwell assay. CCK-8 assay

clone formation and sphere formation were applied to determine in vitro proliferation capacity of the HT29 cells. The tumorigenicity of the co-culture group and the control group was compared by in vivo test. Fluorescence quantitative PCR and Western blotting were used for detecting the expressions of E-cadherin

N-cadherin

vimentin

fibronectin

Snail1

Snail2

Twist1 and Twist2 in the 2 groups.       Results      After co-culture with BD-MSCs

the proliferation of the HT29 cells was significantly increased (P0.05). Compared with the control group

the cell migration of the co-culture group (259.6±19.23 vs 81.6±15.74 cells/field) was significantly enhanced (P0.05)

and the clone formation percentage [(37±2.94)% vs (15.33±2.87)%] and the sphere formation percentage [(31±3.27)% vs (10.33±2.62)%] were significantly improved (P0.05). The tumor formed in the experimental by injection of HT29 cells and BD-MSCs was significantly larger than that formed in the control group by injection of HT29 cells only

and the tumor weight was also statistically different (1.73±0.62 vs 0.54±0.81 g

P0.05). The co-culture group exhibited significant down-regulation of E-cadherin and up-regulation of vimentin and Twist1 compared with the control group.       Conclusion      BD-MSCs promote the proliferation and migration in colorectal cancer cell line HT29.