• A cluster of cooperating tumor-suppressor gene candidates in chromosomal deletions.

      Xue, Wen; Kitzing, Thomas; Roessler, Stephanie; Zuber, Johannes; Krasnitz, Alexander; Schultz, Nikolaus; Revill, Kate; Weissmueller, Susann; Rappaport, Amy R; Simon, Janelle; et al. (2012-05-22)
      The large chromosomal deletions frequently observed in cancer genomes are often thought to arise as a "two-hit" mechanism in the process of tumor-suppressor gene (TSG) inactivation. Using a murine model system of hepatocellular carcinoma (HCC) and in vivo RNAi, we test an alternative hypothesis, that such deletions can arise from selective pressure to attenuate the activity of multiple genes. By targeting the mouse orthologs of genes frequently deleted on human 8p22 and adjacent regions, which are lost in approximately half of several other major epithelial cancers, we provide evidence suggesting that multiple genes on chromosome 8p can cooperatively inhibit tumorigenesis in mice, and that their cosuppression can synergistically promote tumor growth. In addition, in human HCC patients, the combined down-regulation of functionally validated 8p TSGs is associated with poor survival, in contrast to the down-regulation of any individual gene. Our data imply that large cancer-associated deletions can produce phenotypes distinct from those arising through loss of a single TSG, and as such should be considered and studied as distinct mutational events.
    • The promoter of human telomerase reverse transcriptase is activated during liver regeneration and hepatocyte proliferation.

      Sirma, Hüseyin; Kumar, Mukesh; Meena, Jitendra K; Witt, Britta; Weise, Julia M; Lechel, Andre; Ande, Satyanarayana; Sakk, Vadim; Guguen-Guillouzo, Christiane; Zender, Lars; et al. (2011-07)
      Telomerase activity has not been detected in healthy human liver biopsy samples, but it is up-regulated in most human liver tumors. It is not clear whether telomerase is activated in response to acute or chronic liver injury. Telomerase activity is closely associated with expression of its catalytic subunit, telomerase reverse transcriptase (TERT). We analyzed the activity of the human TERT (hTERT) promoter during liver regeneration in vivo and hepatocyte proliferation in vitro.