The process of stromal invasion by cancer cells suggests a The histological observation that well-differentiated role of interstitial collagenase (MMP-1) in early HCC, becancer cells in early hepatocellular carcinoma (HCC) incause other MMPs cannot degrade interstitial stroma. The vade portal tracts and/or fibrous bands and that these purpose of the present study is to demonstrate differences in fibrous tissues then disappear suggests the participation MMP-1 expression at the level of both mRNA and protein of matrix metalloproteinase-1 (MMP-1) in the degradabetween early HCC and advanced HCC and to gain insight tion of fibrous tissue. To confirm this hypothesis, the into the mechanism of cancer invasion and growth in early authors investigated the localization of both the MMP-HCC.
protein and its messenger RNA (mRNA) in early HCC immunohistochemically and by in situ hybridization us-MATERIALS AND METHODS ing complementary DNA (cDNA) and synthetic antisense probe of MMP-1; they then compared the results with Study Samples and Tissue Preparation. Surgically resected materithose in advanced HCC. MMP-1 gene transcripts and als were obtained from seven patients with advanced HCC at the protein were observed in well-differentiated cancer cells Department of Surgery of Keio University Hospital and from another of early HCC but not in moderately or poorly differentiseven with early HCCs (smaller than 2 cm) at the Institute of Gastro- enterology of Tokyo Women's Medical College, Tokyo, Japan. Tissue ated cancer cells. Thus, cancer cells producing MMP-1 specimens were cut into 5-mm pieces within 30 minutes of resection, in early HCC may destroy the portal tract tissue adjafixed in 4% paraformaldehyde in phosphate-buffered saline, washed cent to the cancer lesion and/or the fibrous band of cirin phosphate-buffered saline, dehydrated, and embedded in paraffin, rhosis. These results seem to have demonstrated a differas reported previously. 5 Informed consent was obtained before surence in the mechanism of cancer growth and invasion gery. between early and advanced HCCs. (HEPATOLOGY In Situ Hybridization. For the tissue preparations, prehybridiza-1997;25:580-584.) tion and in situ hybridization methods were similar to those described by Hayashi et al. 6 and reported earlier. 5 The sterile hybridization mixture contained a labeled complementary DNA probe or Abbreviations: HCC, hepatocellular carcinoma; MMP-1, matrix metalloproteinase-1; antisense (5-GAA CCA GCT ATT AGC TTT CTG GAG AGT CAA mRNA, messenger RNA.