The expression of p53, p16 proteins and prevalence of apoptosis in oral squamous cell carcinoma. Correlation with mode of invasion grading system.
OBJECTIVE
Inactivation of p53 and p16 tumor suppressor genes, and apoptosis which is crucial in carcinogenesis have commonly been studied in oral squamous cell carcinoma (OSCC). However, their prognostic value has not yet been clearly established.


METHODS
This study was conducted in the Department of Oral Pathology, Faculty of Dentistry, Gazi University, Ankara, Turkey during the period 2002 to 2003 on formalin-fixed paraffin embedded tissue specimens of 12 lip and 18 intraoral primary squamous cell carcinoma cases. The expression of p53 and p16 proteins were studied by immunohistochemistry, and the apoptosis by TdT-mediated dUTP-biotin nick end-labeling (TUNEL) methods. The possible prognostic value of p53, p16 expression and apoptotic index (AI) value in OSCC were examined on the basis of their correlation with mode of invasion (MI) grading system.


RESULTS
Seven lip (58%) and 9 intraoral cancer (50%) cases showed p53 positivity; where 5 lip (42%) and 15 intraoral cancer (83%) cases showed loss of p16 protein. P53 positive cases increased parallel to MI grade where the AI value decreased. There was not any correlation either between p16 expression and MI grade or AI value. The mean AI value was found as 1,884. Apoptotic index values were higher in invasive site of tumors, and it was statistically significant in MI grade 2 OSCC cases. Apoptotic index value of both central and invasive sites were lowest in MI grade 4 cases.


CONCLUSIONS
The present findings revealed that p53 mutations alone, may play a role in pathogenesis of lip cancers but not in intra OSCC. P16 may have a greater role in the development of intra OSCC. P53 positivity and low AI value may be a predictor of poor prognosis in OSCC.
Tokman
Benay
B
Department of Oral Pathology, Faculty of Dentistry, Gazi University, 8. cadde 84. Sok. 06510, Emek, Ankara, Turkey. benay@gazi.edu.tr
Gultekin
Sibel E
SE
Sezer
Cem
C
Alpar
Reha
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000502:physiology*; D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D008048:Lip Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000473:pathology; D009062:Mouth Neoplasms / Q000473:pathology*; D009361:Neoplasm Invasiveness; D011379:Prognosis; D016159:Tumor Suppressor Protein p53 / Q000032:analysis*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D016159:Tumor Suppressor Protein p53