Clinical Validation of a CXCR4 Mutation Screening Assay for Waldenstrom Macroglobulinemia.
Waldenstrom macroglobulinemia (WM) is a B-cell lymphoma characterized by the accumulation of lymphocytes and plasmacytic cells in the bone marrow and by excess production of immunoglobulin M in serum. WM has been closely linked with the MYD88(L265P) mutation. Whole genome sequencing has identified somatic mutations in the CXCR4 gene in ∼29% of WM cases with MYD88(L265P). CXCR4 mutations may interfere with treatment response to ibrutinib. The goal of this study was to design and validate a clinical assay to detect CXCR4 mutations.



Thirty-three low-grade B-cell lymphomas with plasmacytic differentiation (23 MYD88(L265P) and 10 MYD88(WT)) involving various samples types (fresh and formalin-fixed tissues) formed the study group. We designed and validated Sanger sequencing and pyrosequencing assays to detect mutations in CXCR4 in a Clinical Laboratory Improvement Amendments-approved clinical laboratory.



We identified 8 cases with CXCR4 mutations, including 5 single nucleotide substitutions (3 resulting in p.S338* and 1 in p.R334*), and 3 insertion/deletions. Seven of 8 CXCR4 mutated cases were also MYD88(L265P) mutant. Among the single nucleotide substitutions, we identified a novel missense variant (p.L326P) and a previously reported variant (G335S) of uncertain clinical significance.



We successfully validated a set of clinical assays to detect mutations in CXCR4 mutations in a clinical laboratory.
Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX.
Leomar Y
LY
Ballester
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX.
Sanam
S
Loghavi
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX.
Rashmi
R
Kanagal-Shamanna
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX.
Bedia A
BA
Barkoh
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX.
Pei
P
Lin
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX.
L Jeffrey
LJ
Medeiros
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX.
Rajyalakshmi
R
Luthra
Department of Hematopathology, The University of Texas, MD Anderson Cancer Center, Houston, TX. Electronic address: kppatel@mdanderson.org.
Keyur P
KP
Patel
D000483:Alleles; D019943:Amino Acid Substitution; D015415:Biomarkers; D004252:DNA Mutational Analysis; D005838:Genotype; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D016130:Immunophenotyping; D009154:Mutation; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics; D060787:Neoplasm Grading; D019718:Receptors, CXCR4 / Q000235:genetics*; D015203:Reproducibility of Results; D008258:Waldenstrom Macroglobulinemia / Q000175:diagnosis* / Q000235:genetics*
D015415:Biomarkers; C527276:CXCR4 protein, human; D007075:Immunoglobulin M; D053594:Myeloid Differentiation Factor 88; D019718:Receptors, CXCR4
Ibrutinib; Lymphoplasmacytic lymphoma; MGUS; MYD88; WHIM syndrome