Telomere biology and telomerase mutations in cirrhotic patients with hepatocellular carcinoma

Abstract

Telomeres are repetitive DNA sequences at linear chromosome termini, protecting chromosomes against end-to-end fusion and damage, providing chromosomal stability. Telomeres shorten with mitotic cellular division, but are maintained in cells with high proliferative capacity by telomerase. Loss-of-function mutations in telomere-maintenance genes are genetic risk factors for cirrhosis development in humans and murine models. Telomerase deficiency provokes accelerated telomere shortening and dysfunction, facilitating genomic instability and oncogenesis. Here we examined whether telomerase mutations and telomere shortening were associated with hepatocellular carcinoma (HCC) secondary to cirrhosis. Telomere length of peripheral blood leukocytes was measured by Southern blot and qPCR in 120 patients with HCC associated with cirrhosis and 261 healthy subjects. HCC patients were screened for telomerase gene variants (in TERT and TERC) by Sanger sequencing. Age-adjusted telomere length was comparable between HCC patients and healthy subjects by both Southern blot and qPCR. Four non-synonymous TERT heterozygous variants were identified in four unrelated patients, resulting in a significantly higher mutation carrier frequency (3.3%) in patients as compared to controls (p = 0.02). Three of the four variants (T726M, A1062T, and V1090M) were previously observed in patients with other telomere diseases (severe aplastic anemia, acute myeloid leukemia, and cirrhosis). A novel TERT variant, A243V, was identified in a 65-year-old male with advanced HCC and cirrhosis secondary to chronic hepatitis C virus (HCV) and alcohol ingestion, but direct assay measurements in vitro did not detect modulation of telomerase enzymatic activity or processivity. In summary, constitutional variants resulting in amino acid changes in the telomerase reverse transcriptase were found in a small proportion of patients with cirrhosis-associated HCC.

Telomere Biology and Human Phenotype

“…In meta-analyses, telomere length was shown to be shortened in bladder, oesophageal, gastric, head and neck, ovarian and renal cancers [160]. Short telomeres and telomerase mutations are also associated with hepatocarcinoma [162,163]. However, no association with telomere length was observed in endometrial, prostate and skin cancer.…”

Telomeric zinc-finger associated protein (TZAP): a new player in telomere diseases?

“…Furthermore, we found that germline mutations in telomerase reverse transcriptase (TERT) are enriched in NAFLD-HCC patients (20,21). Interestingly, an enrichment in TERT mutations has also been found in patients with HCC due to other liver diseases (22). However, telomere length was shortened irrespective of the presence of telomerase mutations (20).…”

<p>Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment</p>

“…Complete HCC genome sequencing found many host spots activating mutations in the promoter regions of the TERT gene in about 85% of human tumors, including HCC. 127,128 The modifications are present at nucleotides 124 (mostly G>A and rarely G>T) or 146 (G>A) before the ATG start site in the TERT promoter region. 127 These mutations favor the binding of transcription factors to the promoter, causing TERT overexpression and activation.…”

“…127,128 The modifications are present at nucleotides 124 (mostly G>A and rarely G>T) or 146 (G>A) before the ATG start site in the TERT promoter region. 127 These mutations favor the binding of transcription factors to the promoter, causing TERT overexpression and activation. The long telomeres and increased TERT activity are found to be associated with aggressive HCC with poor prognosis.…”