EPIDERMAL GROWTH-FACTOR RECEPTOR EXPRESSION IN PANCREATIC LESIONS INDUCED IN THE RAT BY AZASERINE

In the present study, the expression of the epidermal growth factor re ceptor (EGFR) was investigated in putative preneoplastic and neoplasti c acinar cell lesions induced in the rat pancreas by azaserine, using Northern blotting, in situ hybridisation (ISH) and immunohistochemistr y. EGFR protein levels were decreased in putative preneoplastic eosino philic acinar cell lesions (atypical acinar cell nodules, AACN) in com parison with normal acinar cells of the pancreas. However, EGFR mRNA e xpression correlated positively with the volume of AACN in pancreatic homogenates and ISH showed equal or stronger EGFR mRNA expression in A ACN than in the surrounding normal acinar cells, Neither EGFR protein nor EGFR mRNA was detected in more advanced lesions such as acinar ade nocarcinomas (ill situ). Moreover, EGFR protein expression showed an i nverse relationship with the mitotic rate of the acinar cells. These f indings suggest that down-regulation of EGFR at the protein level may abrogate negative constraints on cell growth, which may stimulate the development of putative preneoplastic AACN to more advanced lesions an d, ultimately, acinar adenocarcinomas.