Neurobeachin (NBEA) is a target of recurrent interstitial deletions at 13q13 in patients with MGUS and multiple myeloma.
OBJECTIVE
Chromosome 13 deletions (del[13]), detected by metaphase cytogenetics, predict poor outcomes in multiple myeloma (MM), but the gene(s) responsible have not been conclusively identified. We sought to identify tumor-suppressor genes on chromosome 13 using a novel array comparative genomic hybridization (aCGH) strategy.


METHODS
We identified DNA copy number losses on chromosome 13 using genomic DNA isolated from CD138-enriched bone marrow cells (tumor) from 20 patients with MM, monoclonal gammopathy of undetermined significance, or amyloidosis. We used matched skin biopsy (germline) genomic DNA to control for copy number polymorphisms and a novel aCGH array dedicated to chromosome 13 to map somatic DNA gains and losses at ultra-high resolution (>385,000 probes; median probe spacing 60 bp). We analyzed microarray expression data from an additional 262 patient samples both with and without del[13].


RESULTS
Two distinct minimally deleted regions at 13q14 and 13q13 were defined that affected the RB1 and NBEA genes, respectively. RB1 is a canonical tumor suppressor previously implicated in MM. NBEA is implicated in membrane trafficking in neurons, protein kinase A binding, and has no known role in cancer. Noncoding RNAs on chromosome 13 were not affected by interstitial deletions. Both the RB1 and NBEA genes were deleted in 40% of cases (8 of 20; 5 patients with del[13] detected by traditional methods and 3 patients with interstitial deletions detected by aCGH). Forty-one additional MM patient samples were used for complete exonic sequencing of RB1, but no somatic mutations were found. Along with RB1, NBEA gene expression was significantly reduced in cases with del[13].


CONCLUSIONS
The NBEA gene at 13q13, and its expression are frequently disrupted in MM. Additional studies are warranted to evaluate the role of NBEA as a novel candidate tumor-suppressor gene.
O'Neal
Julie
J
Department of Internal Medicine, Division of Oncology, Washington University, Siteman Cancer Center, St Louis, MO, USA.
Gao
Feng
F
Hassan
Anjum
A
Monahan
Ryan
R
Barrios
Samantha
S
Kilimann
Manfred W
MW
Lee
Ian
I
Chng
Wee J
WJ
Vij
Ravi
R
Tomasson
Michael H
MH
D000368:Aged; D001483:Base Sequence / Q000235:genetics*; D001854:Bone Marrow Cells / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D002872:Chromosome Deletion; D002874:Chromosome Mapping / Q000379:methods; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000235:genetics* / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics*; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics*; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000235:genetics*
D002352:Carrier Proteins; C498595:NBEA protein, human; D009419:Nerve Tissue Proteins; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins