Sphingosine kinase 1 enhances the proliferation and invasion of human colon cancer LoVo cells through up-regulating FAK pathway and the expression of ICAM-1 and VCAM-1

Abstract

To investigate the effects of sphingosine kinase 1 (SphK1) on the proliferation, migration and invasion of human colon cancer LoVo cells, and to explore the related mechanisms. Human colon cancer LoVo cells were divided into three groups: phorbol 12-myristate 13-acetate (PMA) was used to induce the activation of SphK1 in the PMA group, N,N-dimethylsphingosine (DMS) used to suppress the activity of SphK1 in DMS group, and the cells treated with equal amount of 0.9 % NaCl instead of drugs served as the control group. The activity of SphK1 was assayed by autoradiography, the cell proliferation was assessed by MTT assay, cell migration and invasion were examined by Boyden chamber assay, concentrations of sICAM-1 and sVCAM-1 were assayed by ELISA, and RT-PCR and Western blot were used to evaluate the mRNA and protein expression in the cells. The activity of SphK1 was efficiently induced by PMA and significantly suppressed by DMS. PMA induced cell proliferation in a time- and dose-dependent manner. On the contrast, DMS suppressed cell proliferation in a time- and dose-dependent manner. After treating with PMA, the number of migrating and invasing cells were increased to 143.36 ± 8.73 and 118.46 ± 6.25, significantly higher than those of the control group (75.48 ± 6.12 and 64.19 ± 5.36). After treating with DMS, the number of migrating and invasing cells were decreased to 38.57 ± 3.24 and 32.48 ± 4.27, significantly lower than those of the control group (P < 0.01). The relative expression levels of FAK, ICAM-1 and VCAM-1 mRNA in the PMA group were 0.82 ± 0.06, 0.74 ± 0.05 and 0.89 ± 0.09, and those in the DMS group were 0.23 ± 0.02, 0.26 ± 0.03 and 0.37 ± 0.04, with significant differences between the PMA, DMS and control groups (P < 0.01). Compared with the control group, the relative expression levels of FAK and p-FAK proteins in the PMA group (0.52 ± 0.06 and 0.51 ± 0.06) were significantly elevated, and those of the DMS group (0.20 ± 0.03 and 0.09 ± 0.02) were significantly decreased. In addition, the concentrations of sICAM-1 and sVCAM-1 were significantly elevated with the activation of SphK1. On the contrary, those of the DMS group were significantly reduced with the suppression of SphK1 (Both P < 0.01). SphK1 may enhance the proliferation, migration and invasion of colon cancer LoVo cells through activating FAK pathway and up-regulating the expression of ICAM-1 and VCAM-1.