Immunolocalization of c-Fos and c-Jun in human oral mucosa and in oral squamous cell carcinoma.

Background: Studies have addressed the relevance of c-Jun and c-Fos proteins in cancer development. In the present study, the expression of c-Jun and c-Fos, the major components of transcription factor activator protein (AP1), were evaluated to determine possible alterations to these factors in oral squamous cell carcinoma (OSCC).

Methods: Fifteen cases of normal oral mucosa and 20 cases of OSCC were retrieved from the Archives of the Surgical Pathology Service at the University of São Paulo. The samples of normal oral mucosa or OSCC originated from different oral mucosal sites. Tissues were submitted for immunohistochemical analysis to detect c-Jun and c-Fos proteins. The OSCC was classified as well, intermediate or poorly differentiated.

Results: The results showed that both c-Jun and c-Fos are expressed in normal oral mucosa and in OSCC. In normal mucosa, immunoreactivity for c-Jun was detected in the cytoplasm of the upper basal layers, while in OSCC, c-Jun was detected in the nuclei of the cells. C-Fos expression was observed in the nuclei of cells, both in normal mucosa and in OSCC, but its expression varied according to the cell layer in normal mucosa, and the differentiation of OSCC.

Conclusions: The nuclear expression of c-Jun in OSCC, in contrast to its cytoplasmic expression in normal oral mucosa, indicates that c-Jun may have a role in the development of oral cancer. In contrast, the absence of both c-Jun and c-Fos in poorly differentiated carcinoma might be useful in understanding the cell cycle events important in uncontrolled cell growth.