Study On The Therapeutic Potentials Of PLK1 In Nasopharyngeal And Larynx Cnacer

The polo-like kinases (Plks) belongs to a family of serine/threonine kinases and are highly conserved from yeasts to mammals. Plk1 is the best-characterized member of the human Plk family. Numerous studies have shown that Plk1 plays critical roles during mitosis and regulates many mitotic events. Moreover, Plk1 was also found to be overexpressed in a broad range of human tumors and serves as a novel therapeutic target in cancer field. In the present study, we systematically investigate the role of Plk1 and its therapeutic potential in nasopharyngeal and larynx cancer. The results are summarized as following.(1) Quick screening of efficient Plk1 siRNA candidates.We designed and synthesized four different Plk1 siRNA candidates which were then are subjected to quick screening by detection of cell growth phenotype and gene expression analysis in Hep2 and HeLa cells. Cell growth analysis revealed that, all of these four Plk1 siRNA candidates efficiently inhibit the growth of Hep2 and HeLa cells. Cell cycle analyis indicated that, compared with control siRNA, Plk1 siRNA cause a significant mitotic cell cycle arrest 72-hours after transfection. In addition, Plk1 siRNA transfection also caused a significant increase in sub-G1 populations. RT-PCR and immunoblotting analysis revealed that all of these four Plk1 siRNA candidates efficiently resulted into the inhibition of Plk1 expression in both Hep2 and HeLa cells. Notably, among these four candidates, Plk1-siRNA-607, Plk1-siRNA-838, and Plk1-siRNA-484 have the strongest activity on cell growth inhibition and apoptosis induction. Moreover, we also tried to mainly use cell growth phenotype for Plk1 siRNA screening. Our results suggested that, compared with the traditional strategy, this method obviously has the advantages such as simplicity and high efficiency, and thus can be used for the high throughout screening of Plk1 siRNA and small molecule inhibitors.(2) The effects of Plk1 siRNA-607 on cell growth and proliferation in human nasopharygeal and larynx carcinoma cells.Furthermore, we investigated the effects of Plk1 siRNA-607 on cell growth and proliferation in human nasopharygeal and larynx carcinoma cells including Hep2 and HNE1. Cell growth analysis indicated that Plk1 siRNA-607 significantly inhibited the cellular growth in both Hep2 and HNE1 cells. FACS analysis indicated that Plk1 siRNA-607 caused a remarkable mitosis cell cyle arrest, the expression level of phosphor-histone H3 remarkably increased. Additionally, sub-G1 population cells also significantly increased after Plk1 siRNA-607 transfection suggestion the occurance of apoptosis. Annexin V-FITC apoptosis assay indicated that Plk1 siRNA-607 did resulted into apoptosis in both Hep2 and HNE1 cells. These results suggested that Plk1 may serve as an efficient therapeutic target in both nasopharygeal and larynx cancer.(3) The effects of siRNA-mediated Plk1 depletion on COS7 cells.The study of this part was designed to investigate the effects of siRNA-mediated Plk1 depletion on COS7 cells and the therapeutic potential of Plk1 in cancer treatment. Synthetic siRNA cocktail duplexes against Plk1 were introduced into COS7 cells. RT-PCR and immunoblotting analysis showed that Plk1 siRNA transfection resulted in a significant inhibition in Plk1 expression in the cells. Cell growth assay indicated that siRNA-mediated Plk1 depletion significantly inhibited the proliferation of COS7 cells. FACS analysis revealed that Plk1 depletion caused cell cycle arrest, resulting into large population of sub-G1 cells. These results are consistent with those obtained from Part one and two in HeLa, Hep2, and HNE1 cells, strongly suggesting that Plk1 may serve as an efficient therapeutic target in many types of cancers.Taken together, in the present study, we systematically investigate the role of Plk1 and its therapeutic potential in nasopharyngeal and larynx cancer. The results indicated that Plk1 might serve as an efficient therapeutic target in both nasopharygeal and larynx cancer.