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Endogenous retrotransposition activates oncogenic pathways in hepatocellular carcinoma.

ABSTRACT: LINE-1 (L1) retrotransposons are mobile genetic elements comprising ~17% of the human genome. New L1 insertions can profoundly alter gene function and cause disease, though their significance in cancer remains unclear. Here, we applied enhanced retrotransposon capture sequencing (RC-seq) to 19 hepatocellular carcinoma (HCC) genomes and elucidated two archetypal L1-mediated mechanisms enabling tumorigenesis. In the first example, 4/19 (21.1%) donors presented germline retrotransposition events in the tumor suppressor mutated in colorectal cancers (MCC). MCC expression was ablated in each case, enabling oncogenic β-catenin/Wnt signaling. In the second example, suppression of tumorigenicity 18 (ST18) was activated by a tumor-specific L1 insertion. Experimental assays confirmed that the L1 interrupted a negative feedback loop by blocking ST18 repression of its enhancer. ST18 was also frequently amplified in HCC nodules from Mdr2(-/-) mice, supporting its assignment as a candidate liver oncogene. These proof-of-principle results substantiate L1-mediated retrotransposition as an important etiological factor in HCC.

SUBMITTER: Shukla R

PROVIDER: S-EPMC3898742 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Endogenous retrotransposition activates oncogenic pathways in hepatocellular carcinoma.

Shukla Ruchi R Upton Kyle R KR Muñoz-Lopez Martin M Gerhardt Daniel J DJ Fisher Malcolm E ME Nguyen Thu T Brennan Paul M PM Baillie J Kenneth JK Collino Agnese A Ghisletti Serena S Sinha Shruti S Iannelli Fabio F Radaelli Enrico E Dos Santos Alexandre A Rapoud Delphine D Guettier Catherine C Samuel Didier D Natoli Gioacchino G Carninci Piero P Ciccarelli Francesca D FD Garcia-Perez Jose Luis JL Faivre Jamila J Faulkner Geoffrey J GJ

Cell 20130301 1

LINE-1 (L1) retrotransposons are mobile genetic elements comprising ~17% of the human genome. New L1 insertions can profoundly alter gene function and cause disease, though their significance in cancer remains unclear. Here, we applied enhanced retrotransposon capture sequencing (RC-seq) to 19 hepatocellular carcinoma (HCC) genomes and elucidated two archetypal L1-mediated mechanisms enabling tumorigenesis. In the first example, 4/19 (21.1%) donors presented germline retrotransposition events in ...[more]

PMID: 23540693

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Project description:Epidemiological studies showed that obesity and its related non-alcoholic fatty liver disease (NAFLD) promote hepatocellular carcinoma (HCC) development. We aimed to uncover the genetic alterations of NAFLD-HCC using whole-exome sequencing. We compared HCC development in genetically obese mice and dietary obese mice with wild-type lean mice fed a normal chow after treatment with diethylnitrosamine. HCC tumor and adjacent normal samples from obese and lean mice were then subjected to whole-exome sequencing. Functional and mechanistic importance of the identified mutations in Carboxyl ester lipase (Cel) gene and Harvey rat sarcoma virus oncogene 1 (Hras) was further elucidated. We demonstrated significantly higher incidences of HCC in both genetic and dietary obese mice with NAFLD development as compared with lean mice without NAFLD. The mutational signatures of NAFLD-HCC and lean HCC were distinct, with <3% overlapped. Eight metabolic or oncogenic pathways were found to be significantly enriched by mutated genes in NAFLD-HCC, but only two of these pathways were dysregulated by mutations in lean HCC. In particular, Cel was mutated significantly more frequently in NAFLD-HCC than in lean HCC. The multiple-site mutations in Cel are loss-of-function mutations, with effects similar to Cel knock-down. Mutant Cel caused accumulation of cholesteryl ester in liver cells, which led to induction of endoplasmic reticulum stress and consequently activated the IRE1α/c-Jun N-terminal kinase (JNK)/c-Jun/activating protein-1 (AP-1) signaling cascade to promote liver cell growth. In addition, single-site mutations in Hras at codon 61 were found in NAFLD-HCC but none in lean HCC. The gain-of-function mutations in Hras (Q61R and Q61K) significantly promoted liver cell growth through activating the mitogen-activated protein kinase (MAPK) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/3-phosphoinositide-dependent protein kinase-1 (PDK1)/Akt pathways. In conclusion, we have identified mutation signature and pathways in NAFLD-associated HCC. Mutations in Cel and Hras have important roles in NAFLD-associated hepatocellular carcinogenesis.

Project description:Background Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide. Although immunotherapy provides hope for advanced HCC patients, the outcomes are not satisfactory and vary by individual case. In this study, we sought to establish novel molecular subtypes and a stable model based on tumor-related pathways for guiding the immunotherapy in HCC patients. Methods A total of 15 pathways including immune pathways, stromal pathways, oncogenic pathways, and DNA damage repair pathways were used to construct molecular subtypes through consensus clustering. Immune characteristics, gene mutations, and genomic alterations including copy number variations and homologous recombination deficiency (HRD) were analyzed in different clusters. The Tumor Immune Dysfunction and Exclusion (TIDE) framework was used to predict the response to immunotherapy. Univariate Cox regression and least absolute shrinkage and selection operator (LASSO) regression were employed to screen prognostic genes for constructing a risk model. Results Three clusters/subtypes were constructed including Immune-E, Immune-D and Stromal-E. Immune-D had the worst prognosis and high enrichment of HRD pathways. Immune-E had higher immune infiltration, higher expression of major histocompatibility complex (MHC)-related genes, and higher expression of PD1, PDL1, CTLA4, and LAG3. TP53 alterations frequently occurred in Immune-D. Immune-E had a relatively high response to immunotherapy and was sensitive to chemotherapeutic drugs. Moreover, we constructed an IMScore model that was effective to classify HCC patients into different risk groups, and the IMScore had a better performance than the TIDE score. Conclusions This study revealed the complex interaction among the tumor microenvironment (TME), genomic alterations, and tumor-related pathways by exploring the molecular difference of 3 subtypes. The IMScore model has potential to provide guidance for immunotherapy in HCC patients.

Dataset Information

Endogenous retrotransposition activates oncogenic pathways in hepatocellular carcinoma.

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Endogenous retrotransposition activates oncogenic pathways in hepatocellular carcinoma.

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