Although inappropriate activation of the Wnt/β-catenin pathway has been implicated in the development of hepatocellular carcinoma (HCC), the role of this signaling in liver carcinogenesis remains ...unclear. To investigate this issue, we constructed a mutant mouse strain, Apc lox/ lox, in which exon 14 of the tumor-suppressor gene adenomatous polyposis coli (Apc) is flanked by loxP sequences. i.v. injection of adenovirus encoding Cre recombinase (AdCre) at high multiplicity 109 plaque-forming units (pfu) per mouse inactivated the Apc gene in the liver and resulted in marked hepatomegaly, hepatocyte hyperplasia, and rapid mortality. β-Catenin signaling activation was demonstrated by nuclear and cytoplasmic accumulation of β-catenin in the hepatocytes and by the induction of β-catenin target genes (glutamine synthetase, glutamate transporter 1, ornithine aminotransferase, and leukocyte cell-derived chemotaxin 2) in the liver. To test a long-term oncogenic effect, we inoculated mice with lower doses of AdCre (0.5× 109 pfu per mouse), compatible with both survival and persistence of β-catenin-activated cells. In these conditions, 67% of mice developed HCC. β-Catenin signaling was strongly activated in these Apc-inactivated HCCs. The HCCs were well, moderately, or poorly differentiated. Indeed, their histological and molecular features mimicked human HCC. Thus, deletion of Apc in the liver provides a valuable model of human HCC, and, in this model, activation of the Wnt/β-catenin pathway by invalidation of Apc is required for liver tumorigenesis.
The taxonomic status of
Allolobophora chlorotica is still the subject of considerable discussion. After the recent experimental demonstration that the two regularly observed colour morphs (pink and ...green) were not fully interfertile and likely represent two distinct species, molecular analyses revealed a more complex picture with the occurrence of five mitochondrial lineages (named L1 to L5) in
A. chlorotica, two within the green morph and three within the pink morph. Although nuclear markers (AFLPs) confirmed that the pink morph might consist of three different taxa, AFLPs data suggested that the green morph may be a single taxon. In order to further characterize the population genetic structure within
A. chlorotica in addition to test for reproductive isolation between lineages, eight polymorphic microsatellite loci were developed using a microsatellite-enriched genomic library from an individual belonging to lineage L2. The number of alleles per locus varied from 9 to 29 in a set of individuals belonging to L2. Considerable sub-structure was observed within L2 populations suggesting a low dispersal capability in this species and a distribution of the individuals in patches that could function as panmictic units. These markers were transferable to the other lineages but only five loci could be amplified consistently in four of the lineages (L1, L2, L3 and L4). Microsatellite data confirmed that the green morph represents a single taxon. Although the integrity of the three previously documented lineages within the pink morph was also generally supported by the data, microsatellites provided evidence for hybridization between lineages and between morphs in the field. Moreover, mitochondrial data revealed the existence of two additional mitochondrial lineages within the pink morph. The taxonomic status of the pink morph remains thus unclear, requiring a thorough and comprehensive study.
We evaluated the possibility of using an experimental model of hepatocellular carcinoma to study oncomarkers of primary liver cancer and compared the diagnostic efficacy of alpha-fetoprotein and ...osteopontin in the experiment and in clinical practice. Experimental studies were performed on a model of hepatocellular carcinoma induced by administration of diethyl nitrosamine to Fisher-344 rats. In addition, the levels of α-fetoprotein and osteopontin were determined in 35 patients with hepatocellular carcinoma detected at stages I-II according to TNM classification. The proposed model of liver cancer in rats reflects the sequence of stages characteristic of hepatocellular carcinoma in humans: liver fibrosis—cirrhosis—cancer. This model is applicable for the study of tumor markers at the early stage of tumor development. Osteopontin was found to have a more powerful diagnostic potential then alpha-fetoprotein.
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