High levels of mitotic progression-associated PLK1 and stress-associated HSF1 have been observed in various human cancers. In the present study, we investigated the effects of PLK1 and HSF1 knockdown on the proliferation of oral cancer cells using small interfering RNA. In human oral squamous cell carcinoma (SCC) tissues, the levels of PLK1 and HSF1 were higher compared to normal tissues. The expression levels of PLK1 and HSF1 were also elevated in the human oral SCC cell lines FaDu and HEp-2. Disruption of PLK1 induced cell cycle arrest at G2/M phase as well as apoptosis in oral cancer cells. Interestingly, knockdown of both PLK1 and HSF1 expression decreased cell proliferation while increasing apoptotic cell death in synergistic fashion. These results establish the potential value of PLK1 and HSF1 as targets for oral cancer therapy.

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