Stimulation of B-Cell Mature Malignancies with the CpG-Oligonucleotide DSP30 and Interleukin-2 for Improved Detection of Chromosome Abnormalities.

Abstract 1955

Poster Board I-978

The detection of chromosome abnormalities in mature B-cell neoplasms by conventional cytogenetics remains difficult, mainly due to the low proliferative rate of mature lymphoid cells. The current FISH panel for chronic lymphocytic leukemia (CLL) is designed to detect some of the more common abnormalities of prognostic significance in CLL [i.e., del(6q), del(11q), +12, del(13q), del(17p)]. This CLL FISH panel has improved the detection rate of these markers by making it possible to obtain cytogenetic information from interphase cells; however, as it is limited to only these 5 markers, it cannot detect all abnormalities associated with CLL. More importantly, the impact of other chromosome abnormalities on prognosis and disease progression, with and without the presence of these 5 prognostic markers, is not known. CpG-oligodeoxynucleotides (ODNs) such as DSP30 activate cells of the immune system in a sequence-dependent manner and promote proliferation of CLL cells in vitro [Decker et al. Blood 2000;95:999-1006]. They also upregulate costimulatory molecules and potential target antigens during immunotherapy. The use of DSP30 in combination with interleukin 2 (IL2) has proven effective in increasing the detection of chromosome abnormalities in CLL [Dicker et al. Blood 2006;108:3152-60] and other mature B-cell lymphoid malignancies by conventional cytogenetics [Struski et al. Leukemia 2009;23:617-9], when compared to the well-established B-cell mitogens. In our extensive clinical experience of incorporating DSP30/IL2 into our culture media, this cocktail has significantly increased the detection of chromosome abnormalities in CLL by conventional cytogenetics, from 55% to greater than 80%. We thus decided to investigate if various other lymphoid malignancies would respond to the mitogen activity of DSP30/IL2 as well as or better than CLL. Specifically, we evaluated 812 cases of mature B-cell lymphoid malignancies that were abnormal by flow cytometry, morphology, or cytogenetic analysis. All samples (bone marrow or blood) were cultured for approximately 72 hours using the DSP30/IL2 mitogen cocktail. Of these 812 cases, 746 (91%) provided sufficient mitotic index and quality for a complete cytogenetic analysis and interpretation. Of the CLL cases (n=509), 79 were initially interpreted as normal by conventional cytogenetic analysis, but were later interpreted as abnormal by FISH for deletion 13q only. In view of the known cryptic nature of this deletion in CLL, these cases were not included in the study, leaving a total of 430 CLL cases, and thus bringing the total number of cytogenetically successful study cases to 667. In addition to the 430 CLL cases, there were 14 variant CLLs; 36 diffuse large B-cell lymphomas (DLBCLs); 35 follicular lymphomas; 34 non-Hodgkin lymphomas (not further specified); 29 marginal zone B-cell lymphomas of splenic type (sMZBCL); 27 mantle cell lymphomas (MCLs), of which 8 were blastoid; 16 MZBCL of MALT type; 13 hairy cell leukemias (HCLs); 12 lymphoproliferative disorders (not further specified); 10 lymphoplasmacytic lymphomas (LPLs); 6 Burkitt lymphomas; 3 Hodgkin lymphomas; and 2 B-cell prolymphocytic leukemias (PLLs). Of particular interest is the fact that we detected clonal abnormalities in 100% of HCLs, blastoid MCLs, variant CLLs, and B-cell PLL, as well as in 97% of sMZBCLs, 89% of DLBCLs, and 80% of LPLs This is of great importance since HCLs and LPLs are rarely abnormal by conventional cytogenetics using the more traditional combinations of mitogens making it difficult to identify markers of prognostic significance. In conclusion, our findings demonstrate that the DSP30/IL2 cocktail induces proliferation of various B-cell mature lymphoid disorders and that its mitogenic action is not limited to CLL. We are continuing to develop our understanding of the considerable response of specific lymphoid malignancies to the DSP30/IL2 cocktail by correlating additional clinical data, and hope that the end result will open new avenues in regards to prognostic outcome and therapeutic approaches.