Open AccessToll-like receptor agonists induce apoptosis in mouse B-cell lymphoma cells by altering NF-κB activation
Author(s) -
Nandini Arunkumar,
Chaohong Liu,
Haiying Hang,
Wenxia Song
Publication year - 2013
Publication title -
cellular and molecular immunology/cellular and molecular immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.5
H-Index - 81
eISSN - 2042-0226
pISSN - 1672-7681
DOI - 10.1038/cmi.2013.14
Subject(s) - tlr9 , cpg oligodeoxynucleotide , apoptosis , b cell , biology , innate immune system , cancer research , toll like receptor 9 , cpg site , microbiology and biotechnology , nf κb , b cell lymphoma , immune system , signal transduction , lymphoma , antibody , immunology , gene expression , dna methylation , gene , biochemistry
Toll-like receptor 9 (TLR9) recognizes microbial DNA containing unmethylated cytosyl guanosyl (CpG) sequences, induces innate immune responses, and facilitates antigen-specific adaptive immunity. Recent studies report that in addition to stimulating innate immunity, TLR9 ligands induce apoptosis of TLR9 expressing cancer cells. To understand the mechanism of TLR9-induced apoptosis, we compared the effects of CpG containing oligodeoxynucleotides (CpG ODN) on a mouse B-cell lymphoma line, CH27, with those on mouse splenic B cells. CpG ODN inhibited constitutive proliferation and induced apoptosis in the CH27 B-cell lymphoma line. In contrast, CpG ODN-treated primary B cells were stimulated to proliferate and were rescued from spontaneous apoptosis. The induction of apoptosis required the ODNs to contain the CpG motif and the expression of TLR9 in lymphoma B cells. A decrease in Bcl-xl expression and an increase in Fas and Fas ligand expression accompanied lymphoma B-cell apoptosis. Treatment with the Fas ligand-neutralizing antibody inhibited CpG ODN-induced apoptosis. CpG ODN triggered a transient NF-κB activation in the B-cell lymphoma cell line, which constitutively expresses a high level of c-Myc, while CpG ODN induced sustained increases in NF-κB activation and c-Myc expression in primary B cells. Furthermore, an NF-κB inhibitor inhibited the proliferation of the CH27 B-cell lymphoma line. Our data suggest that the differential responses of lymphoma and primary B cells to CpG ODN are the result of differences in NF-κB activation. The impaired NF-κB activation in the CpG ODN-treated B-cell lymphoma cell line alters the balance between NF-κB and c-Myc, which induces Fas/Fas ligand-dependent apoptosis.