Macrophage migration inhibitory factor (MIF) is known to be a proinflammatory cytokine, glucocorticoid-induced immunomodulator. MIF is abundantly expressed in various cancer cells, and is considered to contribute to cell growth and differentiation. MIF inactivates the functions of wild-type p53. Consequently, if MIF expression in cancer cells can be suppressed, the functions of p53 and p21 will be restored and an anti-tumor effect can be expected due to the inducement of cell cycle arrest. In the p21 promoter there are three DNA binding sites of STAT-1, and p21 is induced without p53. In the present study, an investigation was made of associations between p53-p21 and STAT-1-p21 signal transmission by the introduction of antisense MIF plasmid and cell cycle. Two groups, namely a transfected antisense MIF plasmid group (antisense MIF group) and a transfected PBK group (PBK group, as a control), in a DLD-1 cell line were created and used in these experiments. The cell cycle, apoptosis, inhibition of growth by subcutaneous tumor, p21 promoter activity, p21 protein, p53 cis enhancer activity and STAT-1 protein were observed. In the antisense MIF group, a shift from the S phase to the G1 phase and an inhibition of growth was noted. Scarcely any apoptotic cells were noted in either group. In terms of p21 promoter, p53 cis enhancer and STAT-1 activity, an increase in activity was found in the anti-sense MIF group. In cancer cells with MIF expression, cell arrest via p21 began due to the inhibition of MIF expression, and increases in p53 transcription activity and in STAT-1 intervention at this time were confirmed.

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