Overexpression of survivin and caspase 3 in oral carcinogenesis

Survivin is an inhibitor of apoptosis protein that inhibits caspase 3 function. While cytoplasmic survivin suppresses apoptosis, nuclear survivin regulates cell division. Little is known about the subcellular localization of survivin in oral carcinogenesis. This study examined the subcellular distribution of these 2 proteins in oral squamous cell carcinoma (OSCC) and premalignant lesions including oral leukoplakia (OL) with and without dysplasia. Expression of survivin and caspase 3 were immunohistochemically analyzed in 114 samples including OSCC, OL with and without dysplasia, and normal oral mucosa (NM). Cytoplasmic and nuclear positive cells were counted separately. The results were presented as the frequency of positive cases. The positive expression rates of cytoplasmic and nuclear survivin in OSCC were significantly higher than in NM, OL with and without dysplasia. NM showed a low rate of cytoplasmic survivin expression compared to OL with and without dysplasia. The numbers of cytoplasmic and nuclear expression of caspase 3 in OSCC were significantly higher than that of NM, OL with and without dysplasia. In conclusion, the overexpression of cytoplasmic survivin in OSCC and premalignant lesions suggest that suppression of apoptosis by survivin occurs at early and late stages of oral carcinogenesis. The elevated expression of nuclear survivin and caspase 3 in OSCC indicate that at the late stage survivin increases cell proliferation whereas caspase 3 promotes apoptosis.