Overexpression of ubiquitin ligases was variously observed among histological types: Skp2 was more frequently observed in SCC and SmCC, KPC in SCC and Pirh2 in AC, followed by SCC.
We used a siRNA plasmid vector, which has an advantage over synthetic siRNAs in determining the effects of decreasing the high constitutive levels of Skp2 protein in oral squamous cell carcinoma.
Elevated expression of SKP2 correlated significantly with positive lymph node metastasis (P = 0.007), with stage II or higher of the international TNM classification (P = 0.014), with poor or moderate differentiation (P < 0.001), and with the presence of squamous cell carcinoma (P = 0.037).
The Skp2 mRNA expression level was high in squamous cell carcinomas and was inversely related with the p27(Kip1) protein level in individual clinical samples.
The Skp2 mRNA expression level was high in squamous cell carcinomas and was inversely related with the p27(Kip1) protein level in individual clinical samples.
These findings indicate that (a) Skp2 may play an important role for the development of OSCC, (b) Skp2 can be a novel target for OSCC treatment as well as a strong prognostic marker, and (c) the reduction in p27(Kip1) protein may be brought about by enhancement of its degradation mediated by increased levels of Skp2 protein.