Follistatin-like protein 1 sustains colon cancer cell growth and apoptosis

Abstract

Objective To investigated the functional role of Follistatin-like protein 1 (FSTL1) on the growth and apoptosis of colon cancer cells. Methods The expression of FSTL1 was dyregulated in DLD1 cells by transfection of FSTL1 small interfering RNA (siRNA). Cell counting kit-8 (CCK-8) and cell clone formation assays were employed to detect the cell viability and proliferation activity in vitro. The cell cycle was analyzed by flow cytometry. Annexin V/PI apoptosis assay was utilized to explore the apoptosis of DLD1 cells. The cell cycle regulating proteins (Cyclin E, E2F-1, p-Rb, p53 and p73), cell apoptosis related factors [Cytochrome C, B cell lymphoma/leukemia-2 associated X protein (bax), B cell lymphoma/leukemia-2 (bcl-2), cysteinyl aspartate-specific protease (Caspase)-3 and poly adenosine diphosphate-ribose polymerase (PARP)] as well as cell signaling pathway factors [phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), phosphorylated c-Jun N-terminal kinase (p-JNK), phosphorylated protein kinase B (p-Akt) and inhibitory κB (IκB)] were determined by Western blotting. Results The A value in blank control (BC) group and siRNA negative control (NC) group were 1.124±0.157 and 1.243±0.161 respectively, significantly higher than that of FSTL1 siRNA group (0.708±0.114) (F=11.172, P<0.01). The clones number in BC group and siRNA NC group were (154.7±16.2) and (183.8±12.6), significantly higher than that of FSTL1 siRNA group (42.3±6.5) (F=24.694, P<0.01). The apoptosis rate in BC group and siRNA NC group were (1.62±0.24)% and (1.84 0.27)%, significantly lower than that of FSTL1 siRNA group (12.32±1.96)% (F=29.687, P<0.01). Knockdown of FSTL1 also increased the levels of Cyclin E, E2F-1 and p-Rb as well as up-regulated the expression of p53 and p73. The F value were 18.694, 31.481, 28.043, 34.875 and 39.746, respectively. The P value were <0.01 and P<0.05, respectively. Silencing of FSTL1 induced DLD1 cell apoptosis through the up-regulation of Cytochrome C and bax as well as the proteolysis of PARP and Caspase 3. The F value were 18.694, 31.481, 28.043, 34.875 and 39.746, respectively. The P value were <0.01 and <0.001, respectively. Inhibition of FSTL1 drceased the levels of p-ERK1/2 and p-Akt in DLD1 cells. The F value were 35.184 and 15.274, respectively. The P value were <0.001 and <0.01, respectively. Conclusion The expression of FSTL1 is clearly associated with the growth and apoptosis of colon cancer cells. Key words: Colon tumorigenesis; Follistatin-like protein 1; Cell death