Deletion and mutation of IL10RA gene on chromosome 11q23 to avert CpG-B oligodeoxynucleotides-induced apoptosis of human chronic lymphocytic leukemia B cells.

Abstract

3023 Background: Targeting TLR9 expressed on human CLL cells with CpG-B oligodeoxynucleotides leads to IL-10-induced tyrosine phosphorylation of STATs and apoptosis of B-CLL cells. However, B-CLL cells from a small subset of patients were resistant to CpG-B ODN treatment. Here, we investigated the molecular mechanism by which B-CLL cells are sensitive or resistant to CpG-B ODN treatment. Methods: Purified CD19+CD23+CD5+primary B-CLL cells were cultured for 5 days with/without CpG-B ODN (CpG 2006, CpG 685) or rh-IL-10. B-CLL cell apoptosis were determined by viable cell counts, Annexin V/PI and TMRE staining, Western blot and intracellular staining of the activation/cleavage of caspases, PARP, Bax translocation and cytochrome c release, IL-10R1 expression and IL-10 binding by flow cytometry, IL10RA gene deletion by FISH, IL10R1 S138G mutation by Bi-PASA, The tyrosine or serine phosphorylation of STATs by Western blot. Results: Fifteen CpG-sensitive and 11 CpG-resistant primary CLL samples were comparatively studied. B-CLL cells from 15/15 CpG-sensitive samples were induced into apoptosis by either CpG-B ODNs or IL-10 in a treatment time and dose-dependent manner. Both CpG-B ODNs and IL-10 significantly increased pTyr701-STAT1/pTyr705-STAT3 expression and induced apoptosis via the mitochondrial apoptotic pathway in 15 primary B-CLL cells. No IL-10RA gene deletions were detected, 13/15 patients were IL10R1 S138G AA wildtypes and 2/15 patients were AG heterozygotes. In contrast, CpG-B ODNs or IL-10 failed to induce apoptosis in 11/11 CpG-resistant B-CLL cells. Interesting, 2/11 CLL samples had IL10RA genes deletion and 7/11 had IL10R1 S138G GG homozygote mutation. IL10RA gene deletion significantly decreased the IL10R1 expression; both IL10RA gene deletion and mutation significantly decreased the IL-10 binding, abolished or reduced CpG-B ODNs or IL10-induced pTyr701-STAT1/pTyr705-STAT3 expression in B-CLL cells. Conclusion: Deletion and mutation of IL10RA gene on chromosome 11q23 averts CpG-B ODN-induced apoptosis of human B-CLL cells, which may serve as biomarker to predict sensitivity or resistance of CLL to CpG-B ODN treatment.