Evidence for a novel mechanism for gene amplification in multiple myeloma: 1q12 pericentromeric heterochromatin mediates breakage-fusion-bridge cycles of a 1q12∼23 amplicon

Jeffrey R. Sawyer, Erming Tian, Edward Thomas, Mark Koller, Colin Stangeby, Gael Sammartino, Linda Goosen, Charles Swanson, Regina L. Binz, Bart Barlogie, John Shaughnessy

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Gene amplification is defined as a copy number (CN) increase in a restricted region of a chromosome arm, and is a mechanism for acquired drug resistance and oncogene activation. In multiple myeloma (MM), high CNs of genes in a 1q12∼23 amplicon have been associated with disease progression and poor prognosis. To investigate the mechanisms for gene amplification in this region in MM, we performed a comprehensive metaphase analysis combining G-banding, fluorescence in situ hybridization, and spectral karyotyping in 67 patients with gain of 1q. In six patients (9%), evidence for at least one breakage-fusion-bridge (BFB) cycle was found. In three patients (4%), extended ladders of 1q12∼23 amplicons were identified. Several key structures that are predicted intermediates in BFB cycles were observed, including: equal-spaced organization of amplicons, inverted repeat organization of amplicons along the same chromosome arm, and deletion of sequences distal to the amplified region. The 1q12 pericentromeric heterochromatin region served as both a recurrent breakpoint as well as a fusion point for sister chromatids, and ultimately bracketed both the proximal and distal boundaries of the amplicon. Our findings provide evidence for a novel BFB mechanism involving 1q12 pericentromeric breakage in the amplification of a large number of genes within a 1q12∼23 amplicon.

Original languageEnglish
Pages (from-to)484-494
Number of pages11
JournalBritish Journal of Haematology
Volume147
Issue number4
DOIs
StatePublished - Nov 2009
Externally publishedYes

Keywords

  • Breakage-fusion-bridge cycles
  • Cytogenetics
  • Gene amplification
  • Multiple myeloma
  • Pericentromeric heterochromatin

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