In a patient with biclonal Waldenstrom macroglobulinemia only one clone expands in three-dimensional culture and includes putative cancer stem cells

Abstract

A small percentage of cases of Waldenstrom macroglobulinemia (WM) present with biclonality, defined here as the rearrangement of two distinct VDJ gene segments. Here we investigated the expansion of two clones from a patient with WM expressing molecularly detectable clonotypic gene rearrangements, one V_H3 and one V_H4. Biclonality was determined in blood and bone marrow mononuclear cells using real-time quantitative PCR (RQ-PCR). V_H4 expressing cells but not V_H3 expressing cells underwent clonal expansion in 3-D culture of reconstructed WM bone marrow. After 3-D culture, secondary culture in a colony forming unit assay, and RQ-PCR, only the V_H4 clone was shown to harbor a subpopulation with characteristics of cancer stem cells, including proliferative quiescence, self-regeneration, and the ability to generate clonotypic progeny, suggesting that the V_H4, but not the V_H3, clone is clinically significant. Enrichment of potential WM stem cells in 3-D cultures holds promise for monitoring their response to treatment and for testing new therapies.

Keywords:

• Leukemic progenitor cells
• molecular genetics
• lymphoma and Hodgkin disease

Declaration of interest: This work was funded by grants from the Canadian Institutes of Health Research and the Alberta Cancer Board Research Initiatives Program. J.K. and K.J.T. were funded by training awards from the Alberta Heritage Foundation for Medical Research. L.M.P. was the Canada Research Chair in Biomedical Nanotechnology and this work was funded in part by the Chairs program.