Abstract: Abstract: Objective To investigate the expression and clinical significance of myeloid cell leukemia-1 (MCL-1) and F-box and WD repeat domain-containing 7 (FBW7) in breast cancer polyploid induced by spindle poisons. Methods (1) Nocodazole spindle poison was used to treat breast cancer cell MDA-MB-231. The morphological changes of cells were ob⁃ served under microscope, and cells were harvested in 0, 6, 12, 24, 48 and 72 h. The cell cycle and DNA-ploidy changes were examined by flow cytometry. The expressions of FBW7 and MCL-1 proteins were detected by Western blot assay. (2) A multikinase inhibitor (Sorafenib) with Nocodazole or Taxol was used to treat MDA-MB-231 cells. MCL-1 protein expression was detected by Western blot assay after 48 h treatment. The cell cycle and DNA-ploidy changes were examined by flow cy⁃ tometry after 48 h treatment. MTT method was used to observe cell proliferation after 48 and 72 h treatment. Results (1)Af⁃ ter treatment by Nocodazole, polyploid characteristics of large cell size and nucleus were appeared. The percentages of octa⁃ ploid were (0.8±0.2)%, (8.5±2.3)%, (7.8±2.0)%, (9.9±0.9)%, (28.2±0.8)% and (35.1±4.9)% after 0, 6, 12, 24, 48 and 72 h treatment, showing the increasing trend in turn (P < 0.001). The number of polyploidy (tetraploid and octaploid) cells was as high as (97.6±0.7)% after 48 h treatment. The expression level of FBW7 protein was decreased significantly but the expres⁃ sion of MCL-1 protein was increased significantly after 48 h treatment. (2) After 48 h treatment, the expression level of MCL- 1 protein, polyploidy percentage and cell proliferation decreased significantly in Nocodazole+Sorafenib group and Taxol+Sorafenib group compared with those of Nocodazole group and Taxol group (P < 0.05). Conclusion The lower expression of FBW7 protein and over- expression of MCL- 1 protein are correlated with the formation of breast cancer polyploidy. Sorafenib can reduce polyploid tumor cells by inhibiting MCL-1 protein expression.

Key words: breast neoplasms, polyploidy, in vitro, myeloid cell leukemia-1, F-box and WD repeat domain-containing 7, spindle poison, Nocodazole, sorafeni