Contributions
Abstract: PB2345
Type: Publication Only
Background
Though complete clinical remissions could be induced in Follicular lymphoma (FL) early and late relapses are relatively often. Key events in tumorogenesis in FL while predecessors of tumor cells migrate from bone marrow to the germinal center of the lymph node follicle include V(D)J-recombination, overexpression of the BCL-2 gene and somatic hypermutation. However, the origin of residual cells that may contribute to the development of relapses in FL still not known.
Aims
To compare FL clonal tumor cells in disease onset and relapse by means of sequencing and mutational analysis of clonally rearranged genes of immunoglobulins heavy chains (IGHV).
Methods
Four FL patients diagnosed and treated at the National Research Center for Hematology, who subsequently relapsed were included in the study. Clinical and laboratory data are summarized in Table 1. B-cell clonality testing and IGHV sequencing was performed according to BIOMED-2 protocol. Fragment analysis and Sanger sequencing was performed on ABI PRISM 3100 genetic analyzer, followed by comparison with the germinal sequence databases www.imgt.org and www.ncbi.nlm.nih.gov/igblast.
Results
B-cell clonality testing and IGHV sequencing at diagnosis and in relapse were done for all 4 patients. Clonal peaks of identical length at diagnosis and in relapse were identified in all 4 cases. Somatic mutations were identified in all cases (90-95% homology with germinal sequence). In three cases additional somatic mutations (from 2 to 3) were identified in relapse while preserving those found in the debut of disease (Table 1). In 3 cases of acquisition of new somatic mutations, patients had late relapses (from 13 months to 21), whereas in one patient with early relapse the nucleotide sequence of the tumor clone remained the same. The data obtained indicate that the tumor cells in relapse originate from the mature clonal cells found in disease onset, and not from the earlier progenitor cell during parallel development.
Conclusion
The data obtained strongly indicate that the late relapse substrate is a mature tumor cell of the debut, which repeatedly passes the differentiation stage in the germinal center of the follicle, acquiring new somatic mutations. The possibility of tumor cells migration between the lymph node and the bone marrow had been shown for FL. One can speculate that the cells of the primary tumor clone may survive chemotherapy in the bone marrow niches and in recurrence return to the lymph node under the influence of an unknown stimulus, while entering a new cycle of somatic hypermutation. In contrast to the late, the development of early relapses may be due to incomplete eradication of FL cells in the sites of primary tumor lesion, as indicated by the stability of the nucleotide sequence. Further studies with extended samples of FL patients are required to obtain data of more statistical power.
Session topic: 19. Non-Hodgkin lymphoma Biology & Translational Research
Keyword(s): Follicular lymphoma, Immunoglobulin gene, Mutation status, Relapse
Abstract: PB2345
Type: Publication Only
Background
Though complete clinical remissions could be induced in Follicular lymphoma (FL) early and late relapses are relatively often. Key events in tumorogenesis in FL while predecessors of tumor cells migrate from bone marrow to the germinal center of the lymph node follicle include V(D)J-recombination, overexpression of the BCL-2 gene and somatic hypermutation. However, the origin of residual cells that may contribute to the development of relapses in FL still not known.
Aims
To compare FL clonal tumor cells in disease onset and relapse by means of sequencing and mutational analysis of clonally rearranged genes of immunoglobulins heavy chains (IGHV).
Methods
Four FL patients diagnosed and treated at the National Research Center for Hematology, who subsequently relapsed were included in the study. Clinical and laboratory data are summarized in Table 1. B-cell clonality testing and IGHV sequencing was performed according to BIOMED-2 protocol. Fragment analysis and Sanger sequencing was performed on ABI PRISM 3100 genetic analyzer, followed by comparison with the germinal sequence databases www.imgt.org and www.ncbi.nlm.nih.gov/igblast.
Results
B-cell clonality testing and IGHV sequencing at diagnosis and in relapse were done for all 4 patients. Clonal peaks of identical length at diagnosis and in relapse were identified in all 4 cases. Somatic mutations were identified in all cases (90-95% homology with germinal sequence). In three cases additional somatic mutations (from 2 to 3) were identified in relapse while preserving those found in the debut of disease (Table 1). In 3 cases of acquisition of new somatic mutations, patients had late relapses (from 13 months to 21), whereas in one patient with early relapse the nucleotide sequence of the tumor clone remained the same. The data obtained indicate that the tumor cells in relapse originate from the mature clonal cells found in disease onset, and not from the earlier progenitor cell during parallel development.
Conclusion
The data obtained strongly indicate that the late relapse substrate is a mature tumor cell of the debut, which repeatedly passes the differentiation stage in the germinal center of the follicle, acquiring new somatic mutations. The possibility of tumor cells migration between the lymph node and the bone marrow had been shown for FL. One can speculate that the cells of the primary tumor clone may survive chemotherapy in the bone marrow niches and in recurrence return to the lymph node under the influence of an unknown stimulus, while entering a new cycle of somatic hypermutation. In contrast to the late, the development of early relapses may be due to incomplete eradication of FL cells in the sites of primary tumor lesion, as indicated by the stability of the nucleotide sequence. Further studies with extended samples of FL patients are required to obtain data of more statistical power.
Session topic: 19. Non-Hodgkin lymphoma Biology & Translational Research
Keyword(s): Follicular lymphoma, Immunoglobulin gene, Mutation status, Relapse