Somatically Acquired LINE-1 Insertions in Normal Esophagus Undergo Clonal Expansion in Esophageal Squamous Cell Carcinoma

Tara T. Doucet-O'Hare, Reema Sharma, Nemanja Rodić, Robert A. Anders, Kathleen H. Burns, Haig H. Kazazian

Research output: Contribution to journalArticlepeer-review

Abstract

Squamous cell carcinoma of the esophagus (SCC) is the most common form of esophageal cancer in the world and is typically diagnosed at an advanced stage when successful treatment is challenging. Understanding the mutational profile of this cancer may identify new treatment strategies. Because somatic retrotransposition has been shown in tumors of the gastrointestinal system, we focused on LINE-1 (L1) mobilization as a source of genetic instability in this cancer. We hypothesized that retrotransposition is ongoing in SCC patients. The expression of L1 encoded proteins is necessary for retrotransposition to occur; therefore, we evaluated the expression of L1 open reading frame 1 protein (ORF1p). Using immunohistochemistry, we detected ORF1p expression in all four SCC cases evaluated. Using L1-seq, we identified and validated 74 somatic insertions in eight tumors of the nine evaluated. Of these, 12 insertions appeared to be somatic, not genetically inherited, and sub-clonal (i.e., present in less than one copy per genome equivalent) in the adjacent normal esophagus (NE), while clonal in the tumor. Our results indicate that L1 retrotransposition is active in SCC of the esophagus and that insertion events are present in histologically NE that expands clonally in the subsequent tumor.

Original languageEnglish (US)
Pages (from-to)942-954
Number of pages13
JournalHuman mutation
Volume37
Issue number9
DOIs
StatePublished - Sep 1 2016

Keywords

  • L1
  • LINE-1
  • esophagus
  • retrotransposition
  • squamous cell carcinoma
  • sub-clonal

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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