Myosin light chain kinase is responsible for high proliferative ability of breast cancer cells via anti-apoptosis involving p38 pathway

Aim: To investigate whether Myosin light chain kinase (MLCK) contributed to the high proliferative ability of breast Cancer cells.

Methods: Soft agar colony formation on the MCF-7 and LM-MCF-7 cell lines was determined. The cell cycles of MCF-7 and LM-MCF-7 were detected using flow cytometry analysis. Western blot analysis was performed to detect the expression levels of p-ERK1/2, total-ERK1/2, p-p38, total p38, p-JNK, total-JNK, Survivin, Bcl-2, p-MLC, caspase-9, cleaved caspase-9, and MLCK. After treatment with adriamycin (ADR), ML-7 and SB203580, Apoptosis was examined using flow cytometry analysis and Annexin V-FITC fluorescence microscopy.

Results: The breast Cancer LM-MCF-7 cell line with high metastasis potential (a metastitic sub-clone of MCF-7) had higher anti-apoptosis ability relative to MCF-7 cells in response to adriamycin treatment (Apoptosis rate: 6.76% vs 28.58%, P<0.05). Moreover, the expression level of MLCK was upregulated and the level of phosphorylated p38 (p-p38) was decreased in LM-MCF-7 cells. Flow cytometry analysis showed that ML-7, selective inhibitor of MLCK, could induce Apoptosis of the LM-MCF-7 cells, in which the level of p-p38 was increased. Meanwhile, the expression levels of Bcl-2 and Survivin were downregulated, while the caspase-9 was upregulated suggesting that the cells were undergone Apoptosis. Flow cytometry analysis showed that SB203580, an inhibitor of p38, abolished ML-7-induced Apoptosis, which resulted in the upregulation of Bcl-2 and Survivin, and downregulation of caspase-9, suggesting that Bcl-2, Survivin and caspase-9 are downstream effectors of p38.

Conclusion: MLCK is responsible for high proliferative ability of breast Cancer cells through anti-apoptosis, in which p38 pathway was involved.