[Effect of GTPase activating protein Git2 on metastasis in breast cancer]

To investigate the effect of GTPase activating protein Git2 on metastasis in breast cancer.

Git2 gene over-expression was induced by Git2 cDNA, and Git2 gene knockdown was induced by Git2 ShRNA lentivirus in four breast cancer cell lines. Six-week old wide type female mice were also used in this study. The cells were tagged with luciferase and injected into wide type female mice by tail vein or 4(th) mammary fat pad, respectively, to establish a cancer metastasis model. In vivo real time imaging system and immunohistochemical staining were used to detect the cancer metastasis.

The relative mRNA expression level of Git2 (normalized by GAPDH) in the 4T1, 4TO7, 168FARN and 67NR cells were 0.91±0.03, 0.125±0.06, 0.131±0.04 and 0.92±0.04, respectively. The expression of EMT marker E-cadherin was inhibited and N-cadherin and vimentin were enhanced when Git2 was over-expressed in 168FARN cells and 4TO7 cells expressing low level of Git2, whereas the expression of E-cadherin was increased and N-cadherin and vimentin were decreased when Git2 was knocked down in 67NR cells and 4T1 cells expressing high level of Git2. Furthermore, over-expression of Git2 promoted 4TO7 cells to progress from micro-metastasis to macro-metastasis. The down-regulation of Git2 pushed 67NR cells to intravasate into blood circulation and suppressed the metastatic ability of 4T1 cells. The number of bioluminescence photos of lung metastatic 4T1-Luc-KD cells was (0.4±0.05)×10(6,) compared with (3.0±0.04)×10(6) in the control 4T1-Luc cells, showing a significant difference (P<0.05).

Our results indicate that Git2 is involved in breast cancer initiation and metastatic colonization.