Bone Marrow Microenvironment-Sustained Lymphoma Persistence in Follicular Lymphoma with Multidirectional Cell Migration between Lymph Node and Bone Marrow
M Wartenberg, C Meyer zum Bueschenfelde, G Ott, A Rosenwald, F Fend, M Kremer. Technical University, Munich, Germany; Robert-Bosch Krankenhaus, Stuttgart, Germany; University of Wuerzburg, Wuerzburg, Germany; University of Tuebingen, Tuebingen, Germany
Background: In follicular lymphoma (FL), the initial t(14;18) translocation is believed to occur in the bone marrow (BM), whereas evolution to definite lymphoma is assumed to proceed within the germinal centers of involved lymph nodes (LN). However, details of tumor cell dissemination to or from the BM remain largely unknown. Goals:We performed simultaneous mutational analysis of the IgH rearrangement of LN and BM clones. By generating genealogical trees, we delineated the dissemination and migration of FL cells between LN and BM, and revealed the clonal evolution of BM involvement. Furtheron, we analyzed ongoing somatic hypermutation (SH) for the presumed influence of BM microenvironment on clonal tumor cell evolution.
Design: Fresh frozen and formalin-fixed sequential biopsies of three FL with simultaneous infiltration of LN and BM were studied, by amplification of the IgH gene with family specific primers (VHL1-6) against FR1, and FR2. Microdissection was used when necessary in BM trephines. Amplification products were cloned, transfected and sequenced. Hierarchical genealogical trees were generated by comparative analysis with the germline sequence (NCBI Blast) and by interclonal comparison. Ongoing mutations were analyzed using the modified multinomial Chang and Casali formula.
Results: The IgH families of the IgH rearrangements were identical in all LN and BM clones of each case, showing the common clonal origin of tumor clones. The cases showed tumor cell clusters for LN and BM clones created by SH. The clones of each tissue shared different numbers of mutations (ranging from 0-16), with early migration from the LN to the BM, and vice versa. All IgH sequences from LN and about 90% of the BM showed ongoing somatic hypermutation with evidence for antigen selection.
Conclusions: BM involvement in FL is characterized by infiltration of early descendants of LN clones. An exchange of BM derivates back to the LN was observed. BM may display a niche for tumor cells during therapy. All LN and most BM infiltrates showed ongoing somatic hypermutation, indicating that the BM provides a mutagenic microenvironment, similar to the germinal centers in LN.
Monday, March 9, 2009 8:45 AM
Platform Session: Section D, Monday Morning