Increasing cell mobility is the basis of tumor invasion and metastasis, and is therefore a therapeutic target for preventing the spread of many types of cancer. Septins are a family of cytoskeletal proteins with GTPase activity, and play a role in many important cellular functions, including cell migration. SEPT9 isoform 1 protein (SEPT9_i1) has been associated with breast tumor development and the enhancement of cell migration; however, the exact mechanism of how SEPT9_i1 might affect breast cancer progression remains to be elucidated. Here, we report that the expression of SEPT9_i1 positively correlated with paxillin, and both were significantly upregulated in invasive breast cancer tissues of patients with lymph node metastases. Lentivirus-mediated shRNA knockdown of SEPT9 in MCF-7 cells diminished tumor cell migration, focal adhesion (FA) maturation and the expression of β-actin, β-tubulin, Cdc42, RhoA, and Rac, whereas overexpression of SEPT9_i1 in SEPT9-knockdown MCF-7 cells promoted cell migration, FA maturation and relevant protein expression. Furthermore, overexpression of SEPT9_i1 in MCF-7 cells markedly increased FAK/Src/paxillin signaling, at least in part through RhoA/ROCK1 upstream activation. Transcriptome profiling suggested that SEPT9_i1 may directly affect “Focal adhesion” and “Regulation of actin cytoskeleton” signaling mechanisms. Finally, overexpression of SEPT9_i1 markedly enhanced lung metastases in vivo 6 weeks after tumor inoculation. These findings suggest that a mechanism of Septin-9-induced aberrant cancer cell migration is through cytoskeletal regulation and FA modulation, and encourages the use of SEPT9 as novel therapeutic target in the prevention of tumor metastasis.

To explore the inhibitory effect in different positions siRNA on hTERT mRNA expression in MCF-7 cells at the different time points, we Designed and chemically synthesized four pairs of siRNA which aimed at human telomerase reverse transcriptase (hTERT) gene specifically, which were transfected into the MCF-7 cells by liposome method, and then the expression of hTERT mRNA in MCF-7 cells was tested respectively by half-quantity RT-PCR at 12 h, 24 h, 48 h, 72 h, and 5 d after transfection. Compared with the control groups, there were three pieces of siRNA that inhibit the expression of hTERT mRNA at 12 h after transfection among the four pieces. The highest inhibition ratio occurred at 48 h after transfection, and after 72 h the ratio descended, when the siRNA sequence was located at the relative simple structure site in the secondary structure of hTERT mRNA had the highest inhibition ratio, which was 75%(P<0.01), which indicated that the specific siRNA had obvious inhibition effect on hTERT gene, and the effect was dependant positionally and timely dependence.