[Overexpression of tumor metastasis suppressor gene 1 suppresses proliferation and invasion, but enhances apoptosis of human breast cancer cells MDA-MB-231 cells].

Objective: To investigate the effects of tumor metastasis suppressor gene 1 (TMSG-1) overexpression on the proliferation, invasion and apoptosis of breast cancer cells and to determine possible correlations of TMSG-1 and metastasis of breast cancer.
Methods: Full-length human TMSG-1 coding sequences were cloned into plasmid pcDNA3.0-FLAG. The recombinant plasmids constructs were transfeced into MDA-MB-231, a highly malignant breast cancer cell line. Parental, vector-only stable transfectant and TMSG-1 stable transfectant clones were tested by MTT, soft agar colony formation and Boyden chamber assays. At twenty-four hours and forty-eight hours post transient transfection, double staining with Annexin-V-FITC and PI were employed to distinguish apoptotic cells from living cells by flow cytometry analysis.
Results: Three TMSG-1 overexpression clones were selected. Compared with the control cells, TMSG-1 overexpression MDA-MB-231 cells showed strong inhibition of proliferation and decreased clonogenicity in soft agar (P<0.05). Transfection of TMSG-1 into MDA-MB-231 cells significantly suppressed the cell invasion ability in vitro (decreased numbers of cells trespassing the matrigel in three experiments: 72.3+/-8.1, 85.0+/-4.2, and 73.5+/-7.8) in comparison with nave cells without transfection (187.5+/-2.1) and cells transfected with the control vector (162.3+/-6.8) (P<0.01). Transient transfection of TMSG-1 into MDA-MB-231 cells could promote cell apoptosis at 24 and 48 hours after transfection (P<0.05).
Conclusions: TMSG-1 protein may have multiple functions in the regulation of proliferation, invasion and apoptosis of metastatic breast cancer cells, likely as a metastasis suppressor gene.