PCR and in situ hybridization studies of telomerase subunits in human non-neoplastic livers

Telomerase, a ribonucleopmtein enzyme associated with cellular immortality, consists of human telomerase RNA component (hTERC), human telomerase prote in 1 (hTEP1), and human telomerase reverse transcriptase (hTERT). In this s tudy, the expression of these subunits was examined in non-neoplastic liver s [13 cases of chronic viral hepatitis (CVH), 16 of primary biliary cirrhos is (PBC), two of primary sclerosing cholangitis, and six normal livers], us ing the reverse transcription-polymerase chain reaction (RT-PCR), nested PC R, and in situ hybridization (ISH). Six hepatocellular carcinoma (HCC) case s and one colonic cancer were used as positive controls. Telomeric repeat a mplification protocol (TRAP) assay disclosed distinct telomerase activity i n all positive controls and weak telomerase activity in non-neoplastic live rs in 4 of 13 CVH cases and 5 of 16 PBC cases. By RT- and nested PCR, both hTERC and hTEP1 mRNA were detectable in all non-neoplastic liver tissues; I SH revealed hTERC and hTEP1 mRNA in the periportal and periseptal hepatocyt es and inflammatory mononuclear cells in those cases examined. ISH revealed hTERT mRNA only in a few infiltrating mononuclear cells in 3 of 13 CVH and 2 of 16 PBC livers and these five cases were also positive by TRAP assay. In four of these five cases, hTERT mRNA was also detectable by nested PCR, suggesting that hTERT mRNA in the non-neoplastic liver is expressed by infi ltrating mononuclear cells. Biliary epithelial cells were totally negative for these human telomerase subunits, Three subunits were constantly detecte d in all positive controls by ISH as well as by RT- and nested PCR, The fin ding that hTERC and hTEP1 mRNA, but not hTERT mRNA, were detectable in the non-neoplastic hepatocytes suggests that telomerase is present but not acti vated and that additional factor(s) are necessary for the expression of hTE RT mRNA in the hepatocytes, along with immortalization and neoplastic trans formation. Copyright (C) 2000 John Wiley & Sons, Ltd.