No abstract

Members of the recently identified family of

Urokinase-type plasminogen activator (uPA) is implicated in the regulation of hepatic regeneration by activating hepatocyte growth factor (HGF). Here, we investigated its role in the hepatic regeneration after Fas-mediated massive hepatocyte death employing mice deficient in either uPA or its inhibitor, plasminogen activator inhibitor-1 (PAI-1). We measured kinetics of hepatic levels of proliferating cell nuclear antigen (PCNA)-labeling index, plasmin activity, mature HGF, and its phosphorylated receptor, c-Met. In the genetically targeted and wild-type mice, hepatocytes fell into the same extent of apoptosis 6 to 12 hours after an intraperitoneal injection with anti-Fas antibody, as judged from histologic analysis and a histon-DNA enzyme-linked immunosorbent assay (ELISA). In the wild-type mice, mature HGF emerged in the liver 6 hours following anti-Fas injection, and hepatic PCNA-labeling index started to increase following 24 hours and peaked at 48 hours. In the uPA ؊/؊ mice, emergence of mature HGF was delayed 12 hours and hepatic regeneration peaked at 96 hours. Supplementation with the uPA gene to the uPA ؊/؊ mice by in vivo lipofection restored hepatic plasmin levels, and improved a delay in the expression of both mature HGF and phosphorylated c-Met, accompanying a normal rate of liver regeneration. In contrast, PAI-1 ؊/؊ mice showed accelerated liver regeneration; mature HGF emerged as early as 3 hours, and PCNA-labeling index increased at 24 hours. This accelerated regeneration was abolished by administration with anti-HGF antibody. These results strongly suggest a physiologic role of uPA in the proteolytic maturation of HGF, and thereby in hepatic regeneration after Fas-mediated massive hepatocyte death. (HEPATOLOGY 2001;33:569-576.)

Our results suggest that AUR, I3C, ACA, NOB, and ACE might exert tumor-preventive action through apoptosis- and/or cell proliferation-dependent mechanisms and, on the other hand, CGA, PA, SIN, HE, DIO, and GL might be apoptosis- and cell proliferation-independent. These assays provided an initial tool for further mechanical studies of tumor-preventive agents and future applications to mechanism-based chemopreventive studies.

The usefulness of mucin-depleted foci (MDF), which have recently been proposed as a new preneoplastic biomarker in rat colon carcinogenesis, was histologically investigated in rat colonic tissues treated with 1,2-dimethylhydrazine dihydrochloride (DMH). The relationship among aberrant crypt foci (ACF), MDF and β β β β-catenin accumulated crypts (BCAC) was examined by comparing the corresponding computer-captured images. Twelve male F344 rats were given DMH s.c. at a dose of 40 mg/kg body weight, once a week for 2 weeks, and randomly divided into two groups. Rats in group 1 were given normal drinking water, while those in group 2 were given drinking water containing indomethacin (IND) at 16 ppm for 6 weeks. All animals were sacrificed 8 weeks after the first DMH treatment. The resected colons were fixed in 10% formalin, and stained with Alcian blue for observation of ACF and MDF. Histological and immunohistochemical analysis revealed that the numbers of ACF, MDF and overlapping lesions in group 2 (treated with IND) were significantly decreased, compared with those in group 1. The number of BCAC in group 2 was also significantly lower than that in group 1. The reduction (61.5%) of MDF by IND was much greater than that (29.3%) of ACF. Analyses of the computer-captured images indicated that MDF had more frequent dysplastic changes and overexpression of β β β β-catenin than did ACF. MDF having over 4 crypts or MDF with the appearance of ACF corresponded well to BCAC. These results suggest that MDF may be useful as an early biomarker in colon carcinogenesis. eliable biomarkers for colon carcinogenesis are needed for screening of chemicals for carcinogenic risk or potential chemopreventive efficacy on colon carcinogenesis. Aberrant crypt foci (ACF), which were originally described by Bird in unsectioned murine colon exposed to a colon-specific carcinogen, azoxymethane (AOM), have been recognized as early preneoplastic lesions. 1) Subsequently, ACF induced by several kinds of chemical carcinogens have been widely used as a biomarker in short-term tests for prediction of colon carcinogenesis. 2) However, some researchers have reported a lack of correlation between ACF induction and tumor development. [3][4][5] Previously, we reported β-catenin accumulated crypts (BCAC) as a new biomarker for rat colon carcinogenesis, strongly predisposing to colon cancer. 6, 7) In addition to the accumulation of oncogenic β-catenin protein, the lesions harbored frequent β-catenin (Ctnnb1) gene mutations that are involved in the development of colon cancer. [8][9][10][11][12] Histological observations of BCAC showed dysplasia, a hallmark of malignant potential, and increasing size with time after the carcinogen exposure. 7) These observations indicate that BCAC are more likely to progress to malignant transformation than are ACF. However, their identification, based on immunohistochemical methods, is difficult in unsectioned colon and the procedure is complicated.Recently, MDF (mucin-depleted foci) have been described to be preneoplastic ...