【Abstract】
Background: Insulin-like growth factor 2 (IGF2) messenger RNA binding protein 3 (IMP3) has been testified to be overexpressed in prostate cancer and strongly related to patients』 poor prognosis. However, the functions of IMP3 and the underlying mechanisms in prostate cancer still remain unknown. Therefore, the current study was carried out to reveal the role and molecular mechanism of IMP3 in prostate cancer progression.
Methods: The expression levels of IMP3 in prostate cancer tissues and cells were detected by immunohistochemistry (IHC), western blotting and RT-PCR. CCK-8, clone formation, flow cytometry and in vivo tumor formation assays were used to determine cell growth, clone formation apoptosis and tumorigenesis, respectively. The effect of IMP3 on the expression levels of the key proteins in PI3K/AKT/mTOR signaling pathway, including PIP2, PIP3, p-AKT, AKT, p-mTOR, mTOR, PTEN and BAD activation of was determined by western blotting. IP (Immunoprecipitation) assay was used to evaluate the effects of IMP3 and SMURF1 (SMAD specific E3 ubiquitin protein ligase 1) on the ubiquitination of PTEN protein.
Results: IMP3 expression level was significantly increased in prostate cancer tissues and cell lines (LNCap, PC3 and DU145) as compared with the paracancerous normal tissues and cells (RWPE-1), respectively. High expression of IMP3 apparently promoted cell viability, tumorigenesis and inhibited cell apoptosis in prostate cancer LNCap, DU145 and PC3 cell lines. In mechanism, IMP3 upregulation significantly increased the phosphorylation levels of AKT and mTOR, and elevated PIP3 expression level, while induced significant reductions in the expression levels of BAD, PTEN and PIP2. And, IMP3 overexpression increased SMURF1 expression, which facilitated PTEN ubiquitination. In addition, SMURF1 overexpression enhanced prostate cancer cell viability and inhibited cell apoptosis. Silence of SMURF1 rescued the enhancements in cell proliferation and tumorigenesis and the inhibition in cell apoptosis rates induced by IMP3 in prostate cancer DU145 and LNCap cells.
Conclusion: This study reveals that IMP3 is overdressed in prostate cancer, which accelerates the progression of prostate cancer through activating PI3K/AKT/mTOR signaling pathway via increasing SMURF1-mediated PTEN ubiquitination.
【中文摘要】
背景:既往研究表明IMP3在前列腺癌組織中呈過表達,且和疾病的進展密切相關,但是其具體機制卻不明確。本研究的目的是揭示IMP3在前列腺癌中的作用以及其具體機制。
方法:通過免疫組化等方法檢測前列腺癌組織中IMP3的表達。通過流式細胞,CCK-8等方法檢測前列腺癌細胞的生長情況,此外,通過免疫共沉澱檢測蛋白質之間的相互關聯作用。
結果:IMP3在前列腺癌細胞以及前列腺癌患者的腫瘤組織中均呈高表達狀態,且IMP3高表達可以促進腫瘤細胞的增殖,並且抑制腫瘤細胞的凋亡。在前列腺癌細胞中,高表達的IMP3可以促進AKT和mTOR的磷酸化,促進PI3K的表達,進而激活PI3K/AKT/mTOR通路促進前列腺癌的發生發展 。進一步研究表明,IMP3可以通過促進SMURF1的表達引起前列腺癌細胞的增殖和抑制凋亡。而SMURF1可以通過促進PTEN的泛素化修飾,降低其胞內水平。
結論:前列腺癌細胞中高表達的IMP3通過增加SMURF1的表達,從而降低PTEN的表達水平,加速其泛素化修飾後,激活PI3K/AKT/mTOR通路,進一步促進前列腺癌細胞的增殖和抑制其凋亡。