P03: A novel marker, alpha2-macroglobulin and GRP78, characteristic of rat hepatocellular preneoplastic and neoplastic lesions undetectable by Glutathione S-transferase placental form

Previously, we reported that alpha 2 -macroglobulin (alpha 2 M) was candidate for a novel marker characteristic for rat hepatocellular preneoplastic and neoplastic lesions, undetectable by well established cytochemical markers “Glutathione S-transferase placental form (GST-P)”. (Sukata et al. 2004 Am. J. Pathol.) In this study, we examined whether 78-kDa glucose-regulated protein (GRP78), which is a molecular chaperone and a member of the HSP70 family of heat shock proteins and is known as a receptor of alpha 2 M, also became a candidate for a new marker of these lesions. GST-P-negative hepatocellular altered foci (HAF), hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC) were generated by two initiation-promotion models with N-nitrosodiethylamine (DEN) and peroxisome proliferators, Wy-14,643 and clofibrate. Total RNAs isolated from laser-microdissected GST-P-negative HAF (amphophilic cell foci) and adjacent normal tissues were applied to microarray analysis. As a result, microarray analysis revealed that GRP78 mRNA expression was not increased in all GST-P negative lesions, regardless of overexpression of alpha 2 M mRNA. Immunohistochemical staining for GRP78 could be detectable in GST-P-negative HAF in the same way as alpha 2 M. GRP78-positive reaction was also detectable in HCC. Furthermore, GRP78 was recognized not only in HCC of rats, but also in HCC of mice. These results suggested that GRP78 was also candidate for a novel marker characteristic for GST-P negative rat hepatocellular preneoplastic and neoplastic lesions. More interestingly, since GRP78 was recognized in the mouse HCC, it is suggested that GRP78 has a possibility that it can become a liver carcinogenic marker beyond a species.