Chronic lymphocytic leukemia (CLL) is an incurable B cell malignancy that represents 30% of all adult leukemia. Although the initiating events are unclear, exposure to factors such as bacterial polysaccharides, lipoproteins, and DNA has been proposed to drive proliferation in CLL, via binding to the B cell receptor (BCR). These factors also serve as ligands for Toll-like receptors (TLRs), a class of receptors critical for innate immunity and that play multiple roles in B cell differentiation and activation. However, exactly how TLR ligands are involved in CLL is unclear, as some studies observe apoptosis after treatment of CLL cells with TLR ligands and other studies observe proliferation. Understanding which ligands have which effects is particularly crucial at present, as TLR ligands are proposed as immunomodulatory agents to coach our immune system to combat CLL. As a clinical case in point, ibrutinib is used to inhibit the BCR signaling that drives proliferation of CLL; but approximately 60% of CLL patients treated with ibrutinib at the Moffitt Cancer Center dropped out of the therapy due to toxicity. In addition, CLL undergoes Richter's transformation into fast-growing diffuse large B cell lymphoma in increasing numbers of patients receiving ibrutinib therapy. Hence, halting B cell proliferation in CLL remains a challenge. Our group used our in-depth understanding of the endoplasmic reticulum (ER) signaling to consider this problem from a different angle, finding that for CLL cells to survive they require activation of the ER stress response. We also found that the IRE-1/XBP-1 pathway of the ER stress response is activated by TLR ligands, to promote proliferation of CLL cells in vitro. These results led us to hypothesize that in CLL cells, specific TLR ligands activate the IRE-1/XBP-1 pathway through TLR and BCR signaling, to promote malignant progression of CLL. We have generated a novel mouse model in which the XBP-1 gene is knocked out specifically in B cells in E-TCL1 (CLL) mice, and showed that BCR signaling is downregulated in XBP-1-deficient E-TCL1 B cells. In addition, we have developed a specific and potent inhibitor of the IRE- 1/XBP-1 pathway, B-I09, which induces apoptosis of CLL in vivo and does not exhibit overt toxicity in mice. Treatment with B-I09 also reduced BCR signaling in E-TCL1 B cells. Using these novel tools, we will determine exactly which TLR ligands promote malignant progression of CLL in vivo via activation of the IRE- 1/XBP-1 pathway and BCR signaling, and whether targeting the IRE-1/XBP-1 pathway can thwart the two- pronged effect of TLR ligands. Based on our new data, we also propose to test whether CLL cells lacking XBP- 1s may activate regulated IRE-1-dependent decay (RIDD) to counter apoptosis. These goals are summarized in the following specific aims.
Aim 1 : Establish that TLR ligand-induced activation of the ER stress response supports malignant progression of CLL in vivo, and proliferation and survival of human CLL cells.
Aim 2 : Investigate whether targeting XBP-1 decelerates TLR ligand-induced progression of CLL by suppressing BCR signaling.
Aim 3 : Investigate how RIDD contributes to the progression of CLL in XBP-1KO/E-TCL1 mice.

Public Health Relevance

Chronic lymphocytic leukemia (CLL) is still an incurable B cell cancer, and CLL cells respond to bacterial or viral products, called TLR ligands. Although some TLR ligands were shown capable of coaching our immune system to combat cancer, we showed that some TLR ligands can activate the endoplasmic reticulum (ER) stress response pathway to support the growth of CLL cells. Here we will find out which TLR ligands can activate the ER stress response in CLL and will test whether targeting the ER stress response pathways can halt TLR-induced CLL proliferation.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
2R01CA163910-07A1
Application #
9738553
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Jhappan, Chamelli
Project Start
2013-09-17
Project End
2024-03-31
Budget Start
2019-04-01
Budget End
2020-03-31
Support Year
7
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Wistar Institute
Department
Type
DUNS #
075524595
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Tang, Chih-Hang Anthony; Chang, Shiun; Paton, Adrienne W et al. (2018) Phosphorylation of IRE1 at S729 regulates RIDD in B cells and antibody production after immunization. J Cell Biol 217:1739-1755
Betts, Brian C; Locke, Frederick L; Sagatys, Elizabeth M et al. (2018) Inhibition of Human Dendritic Cell ER Stress Response Reduces T Cell Alloreactivity Yet Spares Donor Anti-tumor Immunity. Front Immunol 9:2887
Bagashev, Asen; Sotillo, Elena; Tang, Chih-Hang Anthony et al. (2018) CD19 alterations emerging after CD19-directed immunotherapy cause retention of the misfolded protein in the endoplasmic reticulum. Mol Cell Biol :
Tang, Chih-Hang; Chang, Shiun; Hashimoto, Ayumi et al. (2018) Secretory IgM Exacerbates Tumor Progression by Inducing Accumulations of MDSCs in Mice. Cancer Immunol Res 6:696-710
Schutt, Steven D; Wu, Yongxia; Tang, Chih-Hang Anthony et al. (2018) Inhibition of the IRE-1?/XBP-1 pathway prevents chronic GVHD and preserves the GVL effect in mice. Blood Adv 2:414-427
Xie, Hong; Tang, Chih-Hang Anthony; Song, Jun H et al. (2018) IRE1? RNase-dependent lipid homeostasis promotes survival in Myc-transformed cancers. J Clin Invest 128:1300-1316
De Leo, Alessandra; Chen, Horng-Shen; Hu, Chih-Chi Andrew et al. (2017) Deregulation of KSHV latency conformation by ER-stress and caspase-dependent RAD21-cleavage. PLoS Pathog 13:e1006596
Tavernier, Simon J; Osorio, Fabiola; Vandersarren, Lana et al. (2017) Regulated IRE1-dependent mRNA decay sets the threshold for dendritic cell survival. Nat Cell Biol 19:698-710
Tang, Chih-Hang Anthony; Zundell, Joseph A; Ranatunga, Sujeewa et al. (2016) Agonist-Mediated Activation of STING Induces Apoptosis in Malignant B Cells. Cancer Res 76:2137-52
Zhao, Chenguang; Brown, Rebecca S H; Tang, Chih-Hang Anthony et al. (2016) Site-specific Proteolysis Mobilizes TorsinA from the Membrane of the Endoplasmic Reticulum (ER) in Response to ER Stress and B Cell Stimulation. J Biol Chem 291:9469-81

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