Altered keratin expression in buccal mucosal squamous cell carcinoma.

Cytokeratin pattern was analyzed in 14 moderately differentiated and 12 well-differentiated squamous cell carcinomas of buccal mucosa by SDS-PAGE, immunoblotting and two dimensional electrophoresis. These were compared with patterns of normal buccal mucosa and surrounding areas whenever possible. Normal buccal mucosa expresses keratin No. 4 (59Kd), 5 (58Kd), 13 (54Kd) and 14 (50Kd). Keratin No. 4 (59Kd) and 14 (50Kd) were expressed by 20 of 26 tumors studied, while many of the tumors did not express keratins No. 5 (58Kd) and 13 (54Kd). Keratin No. 1 (67Kd) and 16 (48Kd) were aberrantly expressed by 9 well-differentiated tumors. Keratin No. 17 (46Kd) and 18 (45Kd) were expressed by 10 and 8 tumors of 14 moderately differentiated tumors. Six tumors which showed involvement of alveolar mucosa, expressed some keratins expressed by its normal counterpart. Their altered expression was consistent with the differentiation pattern as stated earlier. Non-expression of keratins 5 and 13 seems to be the result of malignant transformation and is seen in the majority of tumors, while appearance of aberrant keratins seems to be related more to the degree of differentiation of the tumor.