目的·探讨10号染色体磷酸酶和张力同源蛋白（phosphatase and tensin homolog，PTEN）对叉头框转录因子M1（forkhead box M1，FoxM1）可变剪接的调控，以及该调控作用对肿瘤细胞迁移的影响。方法·在人胚肾293T细胞，人前列腺癌DU145细胞，人结肠腺癌RKO细胞，人结肠癌SW480、SW620细胞中用短发夹RNA（short hairpin RNA，shRNA）敲低PTEN的mRNA水平。设计针对FoxM1及其亚型FoxM1B和FoxM1C的特异性引物，用实时荧光定量PCR（quantitative real-time PCR，qRT-PCR）检测FoxM1B和FoxM1C的mRNA表达水平在PTEN敲低前后的差异。在DU145细胞中分别过表达FoxM1B和FoxM1C，利用Transwell细胞迁移实验和划痕实验检测两者对肿瘤细胞迁移的影响。通过免疫荧光和双荧光素酶报告基因检测实验，探索FoxM1B和FoxM1C对肿瘤细胞迁移调控差异的潜在机制。结果·① 将293T、DU145、RKO、SW480和SW620细胞内的PTEN敲低后，qRT-PCR检测发现，与对照细胞相比，在PTEN敲低的细胞中FoxM1B的mRNA均显著增多，而FoxM1C的mRNA表现为减少或不变。PTEN敲低不影响FoxM1的转录水平，而影响FoxM1的可变剪接，促进了FoxM1B亚型的生成。② Transwell细胞迁移实验结果显示，与对照细胞相比，FoxM1B过表达组DU145细胞迁移数量增多（P=0.024），FoxM1C过表达组DU145细胞迁移数量减少（P=0.000）。细胞划痕实验结果显示，过表达FoxM1B的DU145细胞愈合能力显著增强（P=0.001），过表达FoxM1C的DU145细胞愈合能力减弱（P=0.021）。FoxM1B和FoxM1C对肿瘤细胞迁移具有相反的调节作用：FoxM1B促进肿瘤细胞迁移，而FoxM1C则抑制肿瘤细胞迁移。③ FoxM1B和FoxM1C过表达，均未引起β连环蛋白入核。双荧光素酶报告基因检测实验发现FoxM1B和FoxM1C的转录活性没有差别，FoxM1B和FoxM1C在调控肿瘤转移方面的差异不是由β连环蛋白转位介导的。结论·PTEN敲低影响肿瘤细胞内FoxM1的可变剪接，导致促迁移的FoxM1B表达增加，从而促进肿瘤细胞迁移。

Objective ·To study the effect of phosphatase and tensin homolog on chromosome 10 (PTEN) on alternative splicing of forkhead box M1 (FoxM1), and its impact on tumor cell migration. Methods ·PTEN was knocked down by short hairpin RNA (shRNA) in human embryonic kidney 293T cells, human prostate cancer DU145 cells, human colorectal adenocarcinoma RKO cells, and human colon cancer SW480 and SW620 cells. Specific primers were designed for FoxM1 and its subtypes FoxM1B and FoxM1C, and the mRNA expression levels of FoxM1B and FoxM1C were detected by quantitative real-time PCR (qRT-PCR). FoxM1B and FoxM1C were overexpressed in DU145 cells, and their effects on tumor cell migration were tested by Transwell assay and wound healing assay. Immunofluorescence and dual luciferase reporter gene assay were used to explore the potential mechanism of differential regulation of tumor cell migration by FoxM1B and FoxM1C. Results ·① PTEN was knocked down in 293T, DU145, RKO, SW480, and SW620 cell lines. qRT-PCR results showed that compared with the control cells, the mRNA expression level of FoxM1B significantly increased in PTEN knockdown cells, while the mRNA expression level of FoxM1C decreased or remained unchanged. Knockdown of PTEN did not affect the transcription level of FoxM1, but caused the variable splicing of FoxM1 and promoted the generation of FoxM1B. ② Compared with the control cells, the number of DU145 cells migrating to the below chamber increased in the FoxM1B overexpression group (P=0.024), while the number of migrating DU145 cells in the FoxM1C overexpression group was lower (P=0.000). The healing ability of DU145 cells was significantly enhanced in the FoxM1B overexpression group (P=0.001), while the healing ability of DU145 cells was weakened in the FoxM1C overexpression group (P=0.021). Overall, FoxM1B and FoxM1C had opposite effects on tumor cell migration. FoxM1B promoted tumor cell migration, while FoxM1C inhibited tumor cell migration. ③ Neither FoxM1B nor FoxM1C overexpression could induce β-catenin to enter the nucleus. Dual luciferase reporter gene assay showed no difference in the transcriptional activity of FoxM1B and FoxM1C. The difference between FoxM1B and FoxM1C in the regulation of tumor metastasis was also not mediated by β-catenin translocation. Conclusion ·Knockdown of PTEN regulates the alternative splicing of FoxM1, leading to increasing expression of transcript FoxM1B, which plays a positive role in tumor cell migration.