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FOXO4

Because of its importance in tumor invasion and metastasis, the epithelial-mesenchymal transition (EMT) has become a research focus in the field of cancer. Recently, evidence has been presented that FoxO4 might be involved in EMT. Our study aimed to detect the expression of FoxO4, E-cadherin and vimentin in non-small cell lung cancers (NSCLCs). We also investigated clinical features and their correlations with the markers. In our study, FoxO4, E-cadherin and vimentin were assessed by immunohistochemistry in a tissue microarray (TMA) containing 150 cases of NSCLC. In addition, the expression level of FoxO4 protein was determined by Western blotting. The percentages of FoxO4, E-cadherin and vimentin positive expression in NSCLCs were 42.7%, 38.7% and 55.3%, respectively. Immunoreactivity of FoxO4 was low in NSCLC when compared with paired normal lung tissues. There were significant correlations between FoxO4 and TNM stage (P<0.001), histological differentiation (P=0.004) and lymph node metastasis (P<0.001), but no significant links with age (P=0.323), gender (P=0.410), tumor size (P=0.084), smoking status (P=0.721) and histological type (P=0.281). Our study showed that low expression of FoxO4 correlated with decreased expression of E-cadherin and elevated expression of vimentin. Cox regression analysis indicated FoxO4 to be an independent prognostic factor in NSCLC (P=0.046). These data suggested that FoxO4 might inhibit the process of EMT in NSCLC, and might therefore be a target for therapy.

Previous studies have shown that dysregulation of microRNA-150 (miR-150) is associated with aberrant proliferation of human non-small cell lung cancer (NSCLC) cells. However, whether miR-150 has a critical role in NSCLC cell metastasis is unknown. Here, we reveal that the critical pro-metastatic role of miR-150 in the regulation of epithelial-mesenchymal-transition (EMT) through down-regulation of FOXO4 in NSCLC. In vitro, miR-150 targets 3'UTR region of FOXO4 mRNA, thereby negatively regulating its expression. Clinically, the expression of miR-150 was frequently up-regulated in metastatic NSCLC cell lines and clinical specimens. Contrarily, FOXO4 was frequently down-regulated in NSCLC cell lines and clinical specimens. Functional studies show that ectopic expression of miR-150 enhanced tumor cell metastasis in vitro and in a mouse xenograft model, and triggered EMT-like changes in NSCLC cells (including E-cadherin repression, N-cadherin and Vimentin induction, and mesenchymal morphology). Correspondingly, FOXO4 knockdown exhibited pro-metastatic and molecular effects resembling the effect of miR-150 over-expression. Moreover, NF-kappaB/snail/YY1/RKIP circuitry regulated by FOXO4 were likely involved in miR-150-induced EMT event. Simultaneous knockdown of miR-150 and FOXO4 abolished the phenotypic and molecular effects caused by individual knockdown of miR-150. Therefore, our study provides previously unidentified pro-metastatic roles and mechanisms of miR-150 in NSCLC.

OBJECTIVE: To examine the expression of forkhead transcription factor O4 (FOXO4) in prostate cancer and to explore its effect on prostate cancer cell invasion. Methods: Immunohistochemistry was used to detect the expression of FOXO4 in prostate hyperplasia tissues and prostate cancer tissues. Western blot was used to detect the expression of FOXO4 in prostate hyperplasia cell line BPH-1 and prostate cancer cell lines: PC-3 and DU145. PC-3 cells with high relative expression of FOXO4 were transfected with FOXO4 siRNA and scramble siRNA; DU145 cells with low expression of FOXO4 were transfected with FOXO4 plasmid and blank vector. Matrigel Transwell assay was used to detect the invasive ability of transfected cells. The expression of endothelial-mesenchymal transition (EMT)-related proteins E-cadherin, N-cadherin, and vimentin in the transfected cells was detected by Western blot. Results: The expression of FOXO4 in prostate cancer cells and tissues was significantly lower than that in the prostate hyperplasia cells and tissues (both P<0.05). In the prostate cancer tissues, the expression of FOXO4 in cancer tissues with prostate cancer specific antigen (PSA) value <4 was significantly higher than that in the tissues with 410 (all P<0.05). The expression of FOXO4 in cancer tissues with Gleason score <8 was significantly higher than that in the cancer tissues with Gleason >/=8 (P<0.05). The expression of FOXO4 in clinical stage T1-T2 prostate cancer tissues was higher than that in the clinical stage T3-T4 prostate cancer tissues (P<0.05). The expression of FOXO4 in prostate cancer tissues without lymph node metastasis was significantly higher than that in the prostate cancer tissues with lymph node metastasis (P<0.05). Down-regulation of FOXO4 in PC-3 cells could significantly promote the EMT and invasion, with the decreased expression of E-cadherin and the increased expression of N-cadherin and vimentin (all P<0.05); Up-regulation of FOXO4 in DU145 cells could inhibit the EMT and invasion of cells, with the increased expression of E-cadherin and the decreased expression of N-cadherin and vimentin (all P<0.05). Conclusion: FOXO4 is involved in prostate cancer progression, and it can inhibit prostate cancer cell invasion by regulating EMT of prostate cancer cells.