[The expression and clinical significance of SphK1 and nuclear factor-κB p65 in human colon carcinoma].

OBJECTIVE: To investigate the expression of sphingosine kinase 1 (SphK1) and NF-κB in colon carcinoma tissues and their correlation with clinicopathologic features. METHODS: Sixty-six paraffin-embedded colon carcinoma samples and 66 fresh colon carcinoma samples were tested using immunohistochemistry, RT-PCR and Western blot, respectively. RESULTS: In 66 fresh colon carcinoma samples, the positive rate of SphK1 and NF-κB mRNA expression were 84.85%(56/66) and 74.24% (49/66), while the positive rate of SphK1 and NF-κB protein detected by Western blot were 78.79% (52/66) and 69.70% (46/66). The positive rates were higher than those in the adjacent tissues [mRNA: 63.64% (42/66), 48.49% (32/66); protein: 57.58% (38/66), 45.45% (30/66)] and the normal mucosa [mRNA: 42.42% (28/66), 25.76% (17/66); protein: 36.36% (24/66), 24.24% (16/66)], with statistical significances (all P values < 0.05). The mean expressive levels of SphK1 and NF-κB mRNA and protein in colon carcinoma were both significantly higher than those in the adjacent tissues and the normal mucosa (mRNA: 0.55 ± 0.06 vs 0.35 ± 0.05 vs 0.25 ± 0.05, 0.75 ± 0.06 vs 0.43 ± 0.05 vs 0.30 ± 0.04; protein: 0.77 ± 0.05 vs 0.38 ± 0.06 vs 0.12 ± 0.03, 0.45 ± 0.08 vs 0.23 ± 0.05 vs 0.13 ± 0.03; all P values < 0.05). There was a close correlation between SphK1 and NF-κB expression levels (r = 0.459, P = 0.036). The results of immunohistochemistry were similar to those of RT-PCR and Western blot. Overexpression of SphK1 and NF-κB in colon carcinoma was related with depth of invasion, distant and lymph node metastasis and Dukes' stages (all P values < 0.05). The expression of SphK1 was also related with differentiation (P < 0.05). CONCLUSIONS: Overexpression of SphK1 and NF-κB may be involved in the pathogenesis and progression of colon carcinoma. Moreover, SphK1 and NF-κB may be correlated with the invasion and metastasis of colon carcinoma.

[Effect of sphingosine kinase 1 on the apoptosis, migration and invasion of colon cancer HT-29 cells and its molecular mechanisms].

OBJECTIVE: To investigate the effect of sphingosine kinase 1 (SphK1) on the proliferation, apoptosis, migration and invasion of colon cancer TH-29 cells and to explore its molecular mechanisms. METHODS: Phorbol 12-myristate 13-acetate (PMA) was used to induce the activity of SphK1 and N, N-dimethylsphingosine (DMS) was used to suppress the activity of SphK1. Cell prolieration and apoptosis were detected by MTT assay and flow cytometry, respectively. The migration and invasion capabilities of the cells were assessed in Transwell chambers. The activity of SphK1 was assayed by autoradiography. Western blot was used to evaluate the protein expression of SphK1, p38, phosphorylated p38 (p-p38) and SAPK/JNK. RESULTS: PMA and DMS were able to induce and suppress the activity and protein expression of SphK1 in a time-dependent manner, respectively. PMA enhanced and DMS suppressed the cell viability in a time- and dose-dependent manner. Being treated with 100 nmol/L PMA or 50 µmol/L DMS for 0, 6, 12, 24 h, the cell apoptosis rates of PMA group were (9.35 ± 0.84)%, (7.61 ± 0.48)%, (5.53 ± 0.76)% and (0.56 ± 0.33)%, contrastly, that of DMS group were (9.18 ± 0.94)%, (12.06 ± 1.41)%, (19.80 ± 2.36)% and (31.85 ± 3.60)%, respectively. Compared with the control group, the cell migration and invasion capabilities of the PMA group were significantly enhanced, and that of the DMS group were significantly suppressed. The migration cell number of control, PMA and DMS groups were 68.75 ± 6.15, 109.33 ± 11.63 and 10.83 ± 2.48, the invasion cell number of control, PMA and DMS groups were 55.42 ± 4.50, 90.58 ± 7.06 and 9.58 ± 2.39, respectively. With the elevating activity and expression of SphK1, the protein expressions of p38, p-p38 and SAPK/JNK were strikingly suppressed. On the contrary, after treating with DMS the protein expressions of p38, p-p38 and SAPK/JNK were enhanced. CONCLUSIONS: SphK1 potently enhances the prolieration, migration and invasion of colon cancer HT-29 cells, meanwhile suppresses the cell apoptosis. The suppressing of the p38 and SAPK/JNK signalling pathways may be one of its molecular mechanisms.