The Effect Of Octreotide On Colonic Cancer Cell SW480 And Its Wnt/β-Catenin Signal Transduction Pathway In Vitro

Objectives To study the effect of somatosatin analogue octreotide at different concentrations on proliferation,apoptosis,cell cycle in colonic cancer cell line. To explore the effect of octreotide on expression of the related genes,β-catenin and phosphorylatedβ-catenin proteins in Wnt/β-Cateninsignal transduction pathway in colonic cancer cell line , to find out the targets somatostatin targeted and to elucidate furtherly the anti-tumor mechanism of somatostatin.Methods Human colonic cancer cell line SW480 was studied in the experiment. MTT assay was used to analyse the effect of octreotide at different concentrations on the proliferation of SW480 cell. Flow cytometry with propidium iodide (PI) labeling method was employed to evaluate the effect of octreotide on apoptosis,cell cycle in SW480 cell. Microarray was used to detect the effect of octreotide at different concentrations on expression of the related genes in Wnt/β-Catenin signal transduction pathway in colonic cancer cell line SW480,the differentiatedly expressed genes were analysed. Western blotting assay was used to evaluate the protein level ofβ-catenin and phosphorylatedβ-catenin in SW480 cell treated by octreotide . Results1 Assays in vitro showed that octreotide inhibited proliferation of colonic cancer cell line SW480 in a dose-dependent manner in a range from 10-12 M to 10-10M and in a time-dependent manner within 48 hours. The inhibitory effect of octreotide at 10-10M was the most significant. Octreotide below 10-13 M had no effect on the growth of colonic cancer cell line SW480.2. In a range from 10-12 M to 10-10M, octreotide induced apoptosis in colonic cancer cell line SW480 in a dose-dependent manner.3. G1 phase rate gradually increased ,S phase rate gradually decreased in colonic cancer cell line SW480 treated by octreotide (10-12-10-10M) for 48 hours.4 .The results of microarray revealed the thirty pieces of genes related to Wnt/β-Catenin signal transduction pathway were differentiatedly expressed in SW480 cell treated by octreotide at 10-10M . Among them, thirteen pieces of genes were upregulated, mainly involving the genes which promote the degradation ofβ-catenin, and seventeen pieces of genes were down-regulated, involving Wnt gene ,down-stream genes and the genes which participate in the transduction of Wnt signal.5 Twenty-seven pieces of genes related to Wnt/β-Catenin signal transduction pathway were differentiatedly expressed in SW480 cell treated by octreotide at 10-14M which had no effect on the growth of SW480 cell. Among them, twenty-one pieces of genes were upregulated, mainly involving the genes which promote the degradation ofβ-catenin, and six pieces of genes were down-regulated, involving Wnt gene and the genes which participate in the transduction of Wnt signal.6. Octreotide reduced the amount ofβ-catenin protein expression in SW480 cell in a dose-dependent and time-dependent manner.7. Otreotide increased the amount of phosphorylatedβ-catenin protein expression in a dose-dependent and time-dependent manner.Conclusion1. Octreotide can inhibit proliferation, induce apoptosis and arrest cell cycle G1 phase of colonic cancer cell line effectively in a dose-dependent and time-dependent manner in a certain degree.2. The present study has testified first and foremost that otreotide can suppress Wnt/β-Catenin signal transduction pathway.3. Otreotide can down-regulate the genes related to Wnt signal transduction and up-regulate the genes which can promote the degradation ofβ-catenin protein.4. Otreotide can down-regulate theβ-catenin protein level and up-regulate phosphorylated beta-catenin protein level.5. The dose at which otreotide suppresses Wnt/β-Catenin signal transduction pathway in colonic cancer cell is much lower than that at which otreotide inhibits the growth of colonic cancer.