[Expression of forkhead transcription factor O4 in prostate cancer and its effect on prostate cancer cell invasion]

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 4≤PSA≤10 and PSA>10 (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.