Abstract
Mitotic progression is regulated by the phosphorylation of heat shock transcription factor 1 (HSF1) by polo-like kinase 1 (PLK1); however, this interaction is often deregulated in tumors. High expression levels of PLK1 and HSF1 have been observed in various types of human cancer. In the present study, it was investigated whether small interfering (si)RNA against PLK1 or HSF1 could suppress tumor growth in vitro and in vivo. In vitro transfection of PLK1 and HSF1 siRNA into PKL1- and HSF1-positive human breast tumor MDA-MB-231 and human cervical carcinoma HeLa cells inhibited cell growth via suppression of PLK1 and HSF1 mRNA expression, respectively. However, the transfection of PLK1 or HSF1 siRNA did not significantly affect the cytotoxicity of doxorubicin in HeLa cells. Furthermore, injection of PKL1 or HSF1 siRNA into mice with liver HeLa metastasis suppressed tumor growth. From these findings, PLK1 and HSF1 may be considered to be promising targets for antitumor therapy.