Human Telomerase Reverse Transcriptase (h-TERT) as Regulator of Telomerase Activity in Indian Hepatocellular Carcinoma

Abstract

Purpose: Telomerase is a ribonuleoprotein that acts as reverse transcriptase. The protein adds the hexanucleotide repeats (TTAGGG)n on the ends of telomeres and is essential for cellular immortality. It is a multimeric enzyme and composed of three subunits: (1) h-TERC, (2) h-TEP1, and (3) h-TERT. h-TERT is essential for in vivo activity of telomerase and has been identified as the catalytic subunit of human telomerase. Objective: To investigate whether telomerase activity is related to h-TERT mRNA expression in hepatocellular carcinoma (HCC) and non-HCC tissues. Methods: Patients of hepatocellular carcinoma (HCC) coming to the Liver Clinic of our Institute were included in the study. Clinical history and examination was done in all patients. Diagnosis of HCC was made by USG/CECT/MRI/AFP and confirmed by imaging guided FNAC. FNAC samples of 17 HCC patients (Group 1) and liver biopsy samples of 15 chronic hepatitis patients (Group 2) without HCC were taken. Total RNA extracted by using acid guanidinium thiocyanate phenol-chloroform extraction method. cDNA generated and h-TERT was amplified using cDNA as template. Telomerase activity was measured using a telomeric repeat amplification protocol (TRAP assay). Results: There were 14 (82.3%) males and 3 (17.7%) females (mean age 57.63 ± 9.68 yrs; 32–72 yrs) in group I, 13 patients (76.47%) were positive for HBsAg, 1 (5.88%) for anti-HCV and 3 patients (17.65%) negative for both HBsAg and anti-HCV. In group 2, 11 (73.33%) were males and 4 (26.67%) females (mean age 41.2 ± 9.57 yrs; 27–58 yrs), 8 patients (53.33%) were positive for anti-HCV and 7 (46.67%) for HBsAg. h-TERT mRNA was expressed in 15 (88.24%) of 17 HCC samples (12 HBsAg +ve and 3 −ve for both the viral markers). These 15 (88.24%) h-TERT positive patients were also positive for telomerase, showing high level of positive correlation between the two. Telomerase and h-TERT mRNA were not present in any of the chronic hepatitis tissue samples. Conclusions: Telomerase is strongly expressed in HCC but not in chronic hepatitis liver biopsy samples. Also, the h-TERT mRNA was detected in all tissues that were telomerase positive and it was undetected in all tissues that were telomerase negative. Thus, h-TERT may be used as an important target for cancer drug development.