Cell cycle regulatory proteins in oral epithelial dysplasia and oral squamous cell carcinomas from Sudan; Association with Toombak-use

Abstract

In Sudan, oral squamous cell carcinoma (OSCC) has been found to be associated with the use of the Sudanese snuff, locally known as toombak. Expression of the cell cycle regulatory proteins, p21WAF1, p16INK4a and Cyclin D1 have been found to be changed in OSCCs compared to normal oral mucosa (NOM). In this work, we aimed to investigate the expression of p21WAF1, p16INK4a and Cyclin D1, in potentially malignant and malignant oral lesions related to toombak- use. Formalin fixed, paraffin embedded tissue specimens from 104 subjects with OSCCs and 20 with oral epithelial dysplasia (OED) from users and non users of toombak were studied by immunohistochemistry (IHC). Ten NOM from non-users were included as controls. A significant difference in the expression of p21WAF1, p16INK4a and Cyclin D1 was found between NOM, OED and OSCC (p<0.001). In the OSCCs, expression of p21WAF1 was significantly higher in toombak- users compared to non- users (p<0.001). Compared to NOM, the expression of p16INK4a was found to be lower in both OSCCs and OED (p<0.001), (p<0.006) respectively. Expression of p16INK4a was found to be significant (p = 0.031) when related to the histological differentiation of the OSCCs and particularly in the toombak– users (p = 0.040). There was a high expression of Cyclin D1 in the OSCCs compared to both NOM and OED (p<0.001), but there was no significant difference between toombak- users and non- users. In conclusion, the expression of the cell cycle regulatory proteins p21WAF1 and Cyclin D1 was found to be increasing from NOM to OED to OSCCs. Patients with OSCCs who were toombak users had high expression of p21 WAF1. Our findings suggest that the difference in expression of these proteins may be important in potentially malignant and malignant oral lesions. In particular, the findings related to p21WAF1 indicate its possible role in the transformation process leading to malignancy in the habitual toombak users.