Research Papers:

3’Igh enhancers hs3b/hs4 are dispensable for Myc deregulation in mouse plasmacytomas with T(12;15) translocations

Alexander L. Kovalchuk _, Tomomi Sakai, Chen-Feng Qi, Wendy Du Bois, Wesley A. Dunnick, Michel Cogné and Herbert C. Morse III

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Oncotarget. 2018; 9:34528-34542. https://doi.org/10.18632/oncotarget.26160

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Alexander L. Kovalchuk1, Tomomi Sakai1, Chen-Feng Qi1, Wendy Du Bois2, Wesley A. Dunnick3, Michel Cogné4 and Herbert C. Morse III1

1Virology and Cellular Immunology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, USA

2Animal Model and Genotyping Core Facility, Laboratory of Cancer Biology and Genetics, NCI, National Institute of Health, Bethesda, MD, USA

3Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA

4Laboratory of Immunology, CNRS UMR 7276, Université de Limoges, Limoges, France

Correspondence to:

Alexander L. Kovalchuk, email: kovalcha@niaid.nih.gov

Keywords: immunoglobulin; Myc; translocation; PCT

Received: July 27, 2018     Accepted: September 06, 2018     Published: October 02, 2018


Myc-deregulating T(12;15) chromosomal translocations are the hallmark cytogenetic abnormalities of murine plasmacytomas (PCTs). In most PCTs, the immunoglobulin heavy chain (Igh) locus is broken between the enhancer and the 3’ regulatory region (3’RR), making the latter the major candidate for orchestrating Myc deregulation. To elucidate the role of the Igh3’RR in tumorigenesis, we induced PCTs in Bcl-xL-transgenic mice deficient for the major Igh3’RR enhancer elements, hs3b and hs4 (hs3b-4-/-). Contrary to previous observations using a mouse lymphoma model, which showed no tumors with peripheral B-cell phenotype in hs3b-4-/- mice, these animals developed T(12;15)-positive PCTs, although with a lower incidence than hs3b-4+/+ (wild-type, WT) controls. In heterozygous hs3b-4+/- mice there was no allelic bias in targeting Igh for T(12;15). Molecular analyses of Igh/Myc junctions revealed dominance of region breakpoints versus the prevalence of Sγ or Sα in WT controls. Myc expression and Ig secretion in hs3b-4-/- PCTs did not differ from WT controls. We also evaluated the effect of a complete Igh3’RR deletion on Myc expression in the context of an established Igh/Myc translocation in ARS/Igh11-transgenic PCT cell lines. Cre-mediated deletion of the Igh3’RR resulted in gradual reduction of Myc expression, loss of proliferative activity and increased cell death, confirming the necessity of the Igh3’RR for Myc deregulation by T(12;15).

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