[Artemin promotes proliferation and invasion of malignant peripheral nerve sheath tumor cells through the PI3K/Akt pathway].

Objective: To investigate the expression of Artemin (ARTN) in malignant peripheral nerve sheath tumor (MPNST), its effect on the malignant behavior of MPNST cells, and its signaling pathway. Methods: Fifty-one MPNST paraffin embedded tissues through surgical resection at Tianjin Medical University Cancer Hospital from January 1995 to November 2011 were collected, the expression of the ARTN protein was detected by immunohistochemistry, and the relationship between the ARTN protein expression and the clinical pathological characteristics and prognosis were analyzed. In human MPNST cell lines ST-8814 (NF-1) and STS26T(sporadic), ARTN overexpression and low expression cell lines were constructed by transfecting ARTN overexpression plasmids and ARTN small interfering RNA (siRNA), respectively. The expression of ARTN mRNA was detected by real time quantitative polymerase chain reaction (RT-qPCR), the expression of the ARTN protein and Phosphoinositide 3-kinase(PI3K)/Akt signaling pathway related proteins were detected by Western blot. CCK-8 assay was used to detect cell proliferation ability, and cell invasion assay was used to detect cell invasion ability. The pathway proteins that interacted with ARTN were searched in the STRING database, and the functional pathways were clarified by Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. The PI3K/Akt pathway specific inhibitor LY294002 was used to block the PI3K/Akt pathway of ST-8814 and STS26T cells to observe the changes in cell proliferation and invasion. Results: Among the 51 MPNST tissue specimens, 22 cases showed a high expression of the ARTN protein and 29 cases showed a low expression of the protein. Higher expressions of the ARTN protein was associated with larger tumor diameters and disease progression (recurrence or metastasis) (both P＜0.05). The median disease-free survival (DFS) of patients with a low expression of the ARTN protein was 26.2 months, and the median overall survival (OS) was 66.9 months. The median DFS and median OS of patients with a high expression of the ARTN protein were 10.7 months and 53.8 months, respectively. The log rank test results showed that the progression free survival rate of patients with a high expression of the ARTN protein was worse than that of patients with a low expression (P=0.027), but the difference in overall survival rate between the two groups was not statistically significant (P=0.790), which was also confirmed by Cox regression analysis. The CCK-8 assay results showed that after 48 hours of transfection, the absorbance (A) values of ST-8814 and STS26T cells in the ARTN overexpression group were 1.35±0.01 and 1.10±0.02, respectively, which were higher than those in the empty plasmid control group (1.05±0.01 and 0.78±0.01, both P＜0.01), while the A values of ST-8814 and STS26T cells in the ARTN siRNA group were 0.35±0.01 and 0.61±0.01, respectively, which were lower than those in the control siRNA group (0.74±0.01 and 1.10±0.04, both P＜0.01). The results of cell invasion assay showed that the number of transmembrane cells in ST-8814 and STS26T cells overexpressing ARTN was (29.67±2.08) and (31.67±2.08), respectively, which were higher than those in the empty plasmid control group [(20.00±1.00) and (24.33±1.15), both P＜0.01]. The number of transmembrane cells in ST-8814 and STS26T cells in the ARTN siRNA group were (14.00±2.00) and (19.33±1.53), respectively, which were lower than those in the control siRNA group [(19.33±2.52) and (23.33±0.58), both P＜0.05].The KEGG results showed that ARTN is associated with multiple tumor signaling pathways, especially the PI3K/Akt signaling pathway. Western blot results showed that overexpression of ARTN upregulated the expression of p-PI3K and p-Akt proteins in ST-8814 and STS26T cells (both P＜0.01).After knocking down ARTN expression, the expression of p-PI3K and p-Akt proteins was significantly down regulated (both P＜0.01). LY294002 could significantly inhibit the effect of ARTN overexpression on ST-8814 and STS26T cells after blocking the PI3K/Akt pathway. The A values of ST-8814 and STS26T cells in the ARTN overexpression+LY294002 group were 1.09±0.06 and 0.82±0.01, respectively, which were lower than those in the ARTN overexpression group (1.50±0.01 and 1.29±0.01, respectively, both P＜0.01). The numbers of transmembrane cells in the cell invasion assay were 16.67±3.21 and 19.67±2.31, respectively, which were also lower than those in the ARTN overexpression group (29.67±2.08 and 31.67±2.08, respectively, both P＜0.01). Conclusions: In MPNST, a high expression of the ARTN protein was associated with larger tumor size, disease progression, and worse DFS. ARTN promotes the proliferation and invasion of MPNST cells through the PI3K/Akt signaling pathway.