Reply to: “TERT promoter mutation during development of hepatoblastoma to hepatocellular carcinoma”
Authors: Roland Kappler, Ivo Leuschner, Dietrich von Schweinitz
Journal: Journal of Hepatology (2014)

TERT promoter mutation during development of hepatoblastoma to hepatocellular carcinomaJournal of HepatologyVol. 62Issue 2PreviewWe read with great interest the article by Eichenmüller et al. [1], who used whole-exome sequencing to describe the genomic landscape of hepatoblastoma (HB) cells and their progenies with hepatocellular carcinoma (HCC)-like features. They concluded that mutation of CTNNB1 and activation of the NFE2L2-KEAP1 pathway are important features in HB-development and further define loss of genomic stability and TERT promoter mutations as prominent characteristics of aggressive HB with HCC features. Although we appreciate these impressive findings, there are some important considerations that need to be stressed. Full-Text PDF Open AccessThe genomic landscape of hepatoblastoma and their progenies with HCC-like featuresJournal of HepatologyVol. 61Issue 6PreviewHepatoblastoma (HB) is the most common childhood liver cancer and occasionally presents with histological and clinical features reminiscent of hepatocellular carcinoma (HCC). Identification of molecular mechanisms that drive the neoplastic continuation towards more aggressive HCC phenotypes may help to guide the new stage of targeted therapies. Full-Text PDF With interest we read the letter by Dong et al., bringing up important points on the role of telomerase reverse-transcriptase (TERT) promoter mutations in paediatric liver tumours, which we would like to comment. First of all, we like to emphasize that hepatoblastoma (HB) and their progenies with hepatocellular carcinoma (HCC)-like features, the so-called transitional liver cell tumours (TLCTs), are full-blown malignant tumours that develop in young children, characteristically without cirrhosis or underlying liver disease. Although HCCs do also occur in older children, they most often lack the cirrhotic background found in 90% of HCC in adults [[1]Forner A. Llovet J.M. Bruix J. Hepatocellular carcinoma.Lancet. 2012; 379: 1245-1255Abstract Full Text Full Text PDF PubMed Scopus (3844) Google Scholar], at least in Western countries. One of the concerns raised by Dong et al. related to our results showing TERT promoter mutations in 2/4 TLCT cases, but not in any HB (0/43), although both tumour types displayed elevated TERT expression levels and typically harbour ß-catenin (CTNNB1) mutations [[2]Eichenmuller M. Trippel F. Kreuder M. Beck A. Schwarzmayr T. Haberle B. et al.The genomic landscape of hepatoblastoma and their progenies with HCC-like features.J Hepatol. 2014; 61: 1312-1320Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar]. Recent work clearly indicates that TERT promoter mutations qualify as the earliest genetic event in the multistep process of carcinogenesis in the adult liver, as they are already found to some extent in preneoplastic lesions and then regularly in HCC [[3]Nault J.C. Mallet M. Pilati C. Calderaro J. Bioulac-Sage P. Laurent C. et al.High frequency of telomerase reverse-transcriptase promoter somatic mutations in hepatocellular carcinoma and preneoplastic lesions.Nat Commun. 2013; 4: 2218Crossref PubMed Scopus (469) Google Scholar], both in virally associated tumours as well as in cases without any underlying liver disease or cirrhosis [[4]Killela P.J. Reitman Z.J. Jiao Y. Bettegowda C. Agrawal N. Diaz Jr., L.A. et al.TERT promoter mutations occur frequently in gliomas and a subset of tumors derived from cells with low rates of self-renewal.Proc Natl Acad Sci U S A. 2013; 110: 6021-6026Crossref PubMed Scopus (1084) Google Scholar]. In line with this, TERT promoter mutations were observed in a high percentage of stage I well-differentiated HCC [[4]Killela P.J. Reitman Z.J. Jiao Y. Bettegowda C. Agrawal N. Diaz Jr., L.A. et al.TERT promoter mutations occur frequently in gliomas and a subset of tumors derived from cells with low rates of self-renewal.Proc Natl Acad Sci U S A. 2013; 110: 6021-6026Crossref PubMed Scopus (1084) Google Scholar], but not in classical adenomas [[5]Pilati C. Letouze E. Nault J.C. Imbeaud S. Boulai A. Calderaro J. et al.Genomic profiling of hepatocellular adenomas reveals recurrent FRK-activating mutations and the mechanisms of malignant transformation.Cancer Cell. 2014; 25: 428-441Abstract Full Text Full Text PDF PubMed Scopus (206) Google Scholar]. Strikingly, TERT expression was significantly upregulated in all HCC cases, being mutated or wild type, as compared to normal liver and hepatocellular adenoma [[3]Nault J.C. Mallet M. Pilati C. Calderaro J. Bioulac-Sage P. Laurent C. et al.High frequency of telomerase reverse-transcriptase promoter somatic mutations in hepatocellular carcinoma and preneoplastic lesions.Nat Commun. 2013; 4: 2218Crossref PubMed Scopus (469) Google Scholar]. Thus, it seems that TERT upregulation needs to be re-acquired for the development of HCC in adults because of its origin from differentiated cells that do not cycle anymore, and that CTNNB1 mutations add on to this in a later phase [[6]Nault J.C. Calderaro J. Tommaso L.D. Balabaud C. Zafrani E.S. Bioulac-Sage P. et al.TERT promoter mutation is an early somatic genetic alteration in the transformation of premalignant nodules in hepatocellular carcinoma on cirrhosis.Hepatology. 2014; https://doi.org/10.1002/hep.27372Crossref Scopus (238) Google Scholar]. In contrast, the high telomerase activity of HB and TLCTs in children might result from the physiological state and high self-renewal capacity of liver precursor cells, from which they develop, and TERT promoter mutations are not necessarily needed for the malignant transformation, which is presumably driven only by Wnt activation. Nevertheless, TERT promoter mutations display a selective phenomenon of TLCTs, which might be used as a marker for the detection of high-risk patients. Concerning our conclusion that TLCTs are rather a genetically derailed progeny of HB than an early onset HCC, we are fully aware that we have analysed only four TLCT cases, which by the way is a respectable number with worldwide seven TLCT cases being published so far [[7]Prokurat A. Kluge P. Kosciesza A. Perek D. Kappeler A. Zimmermann A. Transitional liver cell tumors (TLCT) in older children and adolescents: a novel group of aggressive hepatic tumors expressing beta-catenin.Med Pediatr Oncol. 2002; 39: 510-518Crossref PubMed Scopus (102) Google Scholar]. Nevertheless, we discuss ample characteristics that TLCTs display a neoplastic continuation along an ontogenetic differentiation pathway from HB to HCC, including the CTNNB1 status, AFP serum levels, histology, chromosomal imbalances, and survival rates [[2]Eichenmuller M. Trippel F. Kreuder M. Beck A. Schwarzmayr T. Haberle B. et al.The genomic landscape of hepatoblastoma and their progenies with HCC-like features.J Hepatol. 2014; 61: 1312-1320Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar]. Moreover, we postulate that mutations in gate keeper genes, such as RAD17, MSH6, and TP53 are responsible for the development of an advanced tumour type with chromosomal instability and higher mutation rates. The identification of glypican 3 (GPC3) by microarray analysis as a gene highly overexpressed in HB and HCC [[8]Luo J.H. Ren B. Keryanov S. Tseng G.C. Rao U.N. Monga S.P. et al.Transcriptomic and genomic analysis of human hepatocellular carcinomas and hepatoblastomas.Hepatology. 2006; 44: 1012-1024Crossref PubMed Scopus (304) Google Scholar] has certainly improved the diagnosis of liver tumours. Subsequent immunohistochemical studies revealed that HB are consistently positive (100%) for GPC3, whereas HCCs were positive only in 56–84%, and dysplastic nodules were consistently negative [6Nault J.C. Calderaro J. Tommaso L.D. Balabaud C. Zafrani E.S. Bioulac-Sage P. et al.TERT promoter mutation is an early somatic genetic alteration in the transformation of premalignant nodules in hepatocellular carcinoma on cirrhosis.Hepatology. 2014; https://doi.org/10.1002/hep.27372Crossref Scopus (238) Google Scholar, 9Zynger D.L. Gupta A. Luan C. Chou P.M. Yang G.Y. Yang X.J. Expression of glypican 3 in hepatoblastoma: an immunohistochemical study of 65 cases.Hum Pathol. 2008; 39: 224-230Abstract Full Text Full Text PDF PubMed Scopus (75) Google Scholar, 10Yamauchi N. Watanabe A. Hishinuma M. Ohashi K. Midorikawa Y. Morishita Y. et al.The glypican 3 oncofetal protein is a promising diagnostic marker for hepatocellular carcinoma.Mod Pathol. 2005; 18: 1591-1598PubMed Scopus (301) Google Scholar]. Interestingly, GPC3 positivity was inversely associated with the differentiation of HCCs into poorly (100%), moderately (83%) and well-differentiated (78%) HCCs [[10]Yamauchi N. Watanabe A. Hishinuma M. Ohashi K. Midorikawa Y. Morishita Y. et al.The glypican 3 oncofetal protein is a promising diagnostic marker for hepatocellular carcinoma.Mod Pathol. 2005; 18: 1591-1598PubMed Scopus (301) Google Scholar]. However, GPC3 immunostaining was not helpful in paediatric HCC [[11]Hadzic N. Quaglia A. Portmann B. Paramalingam S. Heaton N.D. Rela M. et al.Hepatocellular carcinoma in biliary atresia: King's College Hospital experience.J Pediatr. 2011; 159: e611Abstract Full Text Full Text PDF Scopus (61) Google Scholar]. By analysing our TLCT cases by immunohistochemistry, we regularly found strong GPC3 positivity in all tumours (Fig. 1), indicating that it more likely reflects the situation of HB than paediatric or adult HCC. Considering the lack of TERT promoter mutations in HB, the strong association between TERT promoter mutations and positive GPC3 immunostaining found by Nault et al. [[6]Nault J.C. Calderaro J. Tommaso L.D. Balabaud C. Zafrani E.S. Bioulac-Sage P. et al.TERT promoter mutation is an early somatic genetic alteration in the transformation of premalignant nodules in hepatocellular carcinoma on cirrhosis.Hepatology. 2014; https://doi.org/10.1002/hep.27372Crossref Scopus (238) Google Scholar] might be statistically significant, but not necessarily biologically relevant. Altogether, we feel that it is safe to predict that TLCTs display a neoplastic continuation along an ontogenetic differentiation pathway from HB to HCC, and that both are characterized by unique features that set them aside from HCC, both in children and adults. Nevertheless, the idea of Dong et al. of investigating paediatric HCCs to clarify the role of TERT promoter mutations is highly appreciated, especially in view of proofing that paediatric HCC is another disease than HCC in adults. The authors declared that they do not have anything to disclose regarding funding or conflict of interest with respect to this manuscript.