NF-κB and AKT signaling prevent DNA damage in transformed pre-B cells by suppressing RAG1/2 expression and activity

Abstract

In developing lymphocytes, expression and activity of the recombination activation gene protein 1 (RAG1) and RAG2 endonuclease complex is tightly regulated to ensure ordered recombination of the immunoglobulin genes and to avoid genomic instability. Aberrant RAG activity has been implicated in the generation of secondary genetic events in human B-cell acute lymphoblastic leukemias (B-ALLs), illustrating the oncogenic potential of the RAG complex. Several layers of regulation prevent collateral genomic DNA damage by restricting RAG activity to the G 1 phase of the cell cycle. In this study, we show a novel pathway that suppresses RAG expression in cycling-transformed mouse pre-B cells and human pre-B B-ALL cells that involves the negative regulation of FOXO1 by nuclear factor kB (NF-kB). Inhibition of NF-kB in cycling pre-B cells resulted in upregulation of RAG expression and recombination activity, which provoked RAG-dependent DNA damage. In agreement, we observe a negative correlation between NF-kB activity and the expression of RAG1, RAG2, and TdT in B-ALL patients. Our data suggest that targeting NF-kB in B-ALL increases the risk of RAG-dependent genomic instability. (Blood. 2015;126(11):1324-1335

Chimeric Antigen Receptor T Cells and Hematopoietic Cell Transplantation: How Not to Put the CART Before the Horse

“…Several hundred patients have been treated with CART19 13–18, 41 to date and over a dozen with other CARTs (CARTs directing against BCMA 52 , CD20 50 , CD22 51 , CD30 53 , CD33 54 and CD123 55 ). We have learned that outcomes after CART19 are variable depending on the disease, the patient, and the CAR composition and manufacturing.…”

“…46, 47 Subsequent clinical experience of CART cell therapy reported to date has been with CD19 directed CARTs in B cell malignancies (CLL, acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma (NHL)). 13–17, 42, 48, 49 Other B cell antigens have been targeted by CART cells, including CD20 50 and CD22 51 . Promising early data of BCMA directed CART cells in multiple myeloma were reported at the 2015 annual meeting of the American Society of Hematology.…”

“…A handful of these patients were treated with CD22 CART cells with variable responses. 51 Current efforts are underway to prevent CD19 negative relapse in preclinical models, by targeting multiple antigens. 87, 88 …”

Immature Lymphocytes Inhibit Rag1 and Rag2 Transcription and V(D)J Recombination in Response to DNA Double-Strand Breaks

“…Several studies have investigated the role of NF-κB proteins in regulating Rag1/Rag2 expression in immature B cells, reaching apparently contradictory conclusions. In immortalized and transformed cell lines, the expression of a dominant negative IκBα protein that sequesters canonical NF-κB proteins in the cytoplasm either has no effect or increases sporadic Rag1/Rag2 expression depending on the lines analyzed (68, 69). The inhibition of canonical NF-κB activity in primary pre-B cells by expression of the same dominant negative IκBα protein or by Mb1Cre -mediated deletion of Nemo has no effect on Rag1 and Rag2 mRNA levels, even after IL7 withdrawal (33).…”

Immunotherapy of hepatocellular carcinoma using chimeric antigen receptors and bispecific antibodies

“…More commonly, they activate effector cells and bring them to engage cancer cells to execute their cytotoxic functions [77]. CAR technology has been tested against the target CD19 (in human cancers such as ALL, CLL), GD2 (neuroblastoma), CD22 (ALL), mesothelin (mesothelioma), and HER2 (sarcoma) [4, 8, 38, 45, 76, 90], and IL13R (glioblastoma) [13] with overwhelming success in CD19(+) leukemia, but only select solid tumors. Several factors might be responsible for the inferior efficacy of CART cells in solid versus hematological malignancies including target antigen heterogeneity, poor trafficking and penetration of therapeutic cells, and the hostile tumor microenvironment (hypoxia, acidosis, nutrient depletion, tumor-derived immunosuppressive molecules, various immunosuppressive cells including tumor-associated macrophages, regulatory T cells, and myeloid-derived suppressor cells) [85].…”