Holbrook Kohrt: In Memoriam (1977-2016).
Clinical cancer research
2016; 22 (14): 3695-3696
Ibrutinib enhances the antitumor immune response induced by intratumoral injection of a TLR9 ligand in mouse lymphoma
2015; 125 (13): 2079-2086
Therapeutic antitumor immunity by checkpoint blockade is enhanced by ibrutinib, an inhibitor of both BTK and ITK.
Proceedings of the National Academy of Sciences of the United States of America
2015; 112 (9): E966-72
We have designed a novel therapeutic approach for lymphoma that combines targeted kinase inhibition with in situ vaccination. Intratumoral injection of an unmethylated cytosine guanine dinucleotide (CpG)-enriched oligodeoxynucleotide, an agonist for the toll-like receptor 9 (TLR9), induces the activation of natural killer cells, macrophages, and antigen presenting cells that control tumor growth at the local site. Ibrutinib, an irreversible inhibitor of Bruton's tyrosine kinase, a key enzyme in the signaling pathway downstream of B-cell receptor, is an effective treatment against many types of B-cell lymphomas. The combination of intratumoral injection of CpG with systemic treatment by ibrutinib resulted in eradication of the tumors not only in the injected site, but also at distant sites. Surprisingly, this combinatorial antitumor effect required an intact T-cell immune system since it did not occur in nude, severe combined immunodeficiency, or T-cell depleted mice. Moreover, T cells from animals treated with intratumoral CpG and ibrutinib prevented the outgrowth of newly injected tumors. This result suggests that ibrutinib can induce immunogenic cell death of lymphoma cells and that concomitant stimulation of antigen-presenting cells in the tumor microenvironment by toll-like receptor ligands can lead to a powerful systemic antitumor immune response.
View details for DOI 10.1182/blood-2014-08-593137
View details for Web of Science ID 000354626300014
Radiotherapy and Toll-Like Receptor Agonists
SEMINARS IN RADIATION ONCOLOGY
2015; 25 (1): 34-39
Radiotherapy and toll-like receptor agonists.
Seminars in radiation oncology
2015; 25 (1): 34-39
Monoclonal antibodies can block cellular interactions that negatively regulate T-cell immune responses, such as CD80/CTLA-4 and PD-1/PD1-L, amplifying preexisting immunity and thereby evoking antitumor immune responses. Ibrutinib, an approved therapy for B-cell malignancies, is a covalent inhibitor of BTK, a member of the B-cell receptor (BCR) signaling pathway, which is critical to the survival of malignant B cells. Interestingly this drug also inhibits ITK, an essential enzyme in Th2 T cells and by doing so it can shift the balance between Th1 and Th2 T cells and potentially enhance antitumor immune responses. Here we report that the combination of anti-PD-L1 antibody and ibrutinib suppresses tumor growth in mouse models of lymphoma that are intrinsically insensitive to ibrutinib. The combined effect of these two agents was also documented for models of solid tumors, such as triple negative breast cancer and colon cancer. The enhanced therapeutic activity of PD-L1 blockade by ibrutinib was accompanied by enhanced antitumor T-cell immune responses. These preclinical results suggest that the combination of PD1/PD1-L blockade and ibrutinib should be tested in the clinic for the therapy not only of lymphoma but also in other hematologic malignancies and solid tumors that do not even express BTK.
View details for DOI 10.1073/pnas.1500712112
View details for PubMedID 25730880
Targeting CD137 enhances the efficacy of cetuximab.
journal of clinical investigation
2014; 124 (6): 2668-2682
The clinical successes of CTLA4 and PD-1 immune checkpoint blockade in aggressive malignancies such as metastatic melanoma and non-small cell lung carcinoma inaugurate a new era in oncology. Indeed, as opposed to tumor-targeted therapies, it is now clear that immune-targeted therapies designed to enhance the antitumor immune response are a relevant strategy to obtain long-term tumor responses. Interestingly, the study of tumor cell death biology has recently revealed that part of radiotherapy efficacy relies on its ability to trigger an immune response against tumor cells. This "immunogenic cell death" partly relies on the generation of damage-associated molecular patterns, which can stimulate immune sensors such as toll-like receptors. Tumor radiation therapy can therefore be envisioned as a strategy to perform an in situ immunization because it can initiate the release of tumor-associated antigens, deplete immune suppressors, and stimulate antigen-presenting cells via endogenous release of toll-like receptor agonists. Moreover, combinations of radiotherapy with immune checkpoint antibodies are synergistic in preclinical models. The translation of these observations in the clinic is ongoing in early phase I/II trials.
View details for DOI 10.1016/j.semradonc.2014.07.006
View details for PubMedID 25481264
Ibrutinib antagonizes rituximab-dependent NK cell-mediated cytotoxicity.
2014; 123 (12): 1957-1960
Anti-KIR antibody enhancement of anti-lymphoma activity of natural killer cells as monotherapy and in combination with anti-CD20 antibodies
2014; 123 (5): 678-686
Treatment with cetuximab, an EGFR-targeting IgG1 mAb, results in beneficial, yet limited, clinical improvement for patients with head and neck (HN) cancer as well as colorectal cancer (CRC) patients with WT KRAS tumors. Antibody-dependent cell-mediated cytotoxicity (ADCC) by NK cells contributes to the efficacy of cetuximab. The costimulatory molecule CD137 (4-1BB) is expressed following NK and memory T cell activation. We found that isolated human NK cells substantially increased expression of CD137 when exposed to cetuximab-coated, EGFR-expressing HN and CRC cell lines. Furthermore, activation of CD137 with an agonistic mAb enhanced NK cell degranulation and cytotoxicity. In multiple murine xenograft models, including EGFR-expressing cancer cells, HN cells, and KRAS-WT and KRAS-mutant CRC, combined cetuximab and anti-CD137 mAb administration was synergistic and led to complete tumor resolution and prolonged survival, which was dependent on the presence of NK cells. In patients receiving cetuximab, the level of CD137 on circulating and intratumoral NK cells was dependent on postcetuximab time and host FcyRIIIa polymorphism. Interestingly, the increase in CD137-expressing NK cells directly correlated to an increase in EGFR-specific CD8+ T cells. These results support development of a sequential antibody approach against EGFR-expressing malignancies that first targets the tumor and then the host immune system.
View details for DOI 10.1172/JCI73014
View details for PubMedID 24837434
Depleting tumor-specific Tregs at a single site eradicates disseminated tumors
JOURNAL OF CLINICAL INVESTIGATION
2013; 123 (6): 2447-2463
Natural killer (NK) cells mediate anti-lymphoma activity by spontaneous cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC) when triggered by rituximab, an anti-CD20 monoclonal antibody (mAb) used to treat patients with B cell lymphomas. The balance of inhibitory and activating signals determines the magnitude of NK cell's efficacy by spontaneous cytoxicity. Here, using a killer cell immunoglobulin-like receptor (KIR) transgenic murine model, we show that blockade of the interface of inhibitory KIRs with MHC class I antigens on lymphoma by anti-KIR antibodies prevents a tolerogenic interaction and augments NK cell spontaneous cytotoxicity. In combination with anti-CD20 mAbs, anti-KIR treatment induces enhanced NK cell-mediated, rituximab-dependent cytotoxicity against lymphoma in vitro and in vivo in KIR transgenic and syngeneic murine lymphoma models. These results support a therapeutic strategy of combination, rituximab and KIR blockade through lirilumab, illustrating the potential efficacy of combining a tumor targeting therapy with an NK cell agonist thus stimulating the post-rituximab anti-lymphoma immune response.
View details for DOI 10.1182/blood-2013-08-519199
View details for Web of Science ID 000335832500020
Selective elimination of alloreactivity in vitro and in vivo while sparing other T-cell-mediated immune responses
BONE MARROW TRANSPLANTATION
2012; 47 (6): 838-845
Activation of TLR9 by direct injection of unmethylated CpG nucleotides into a tumor can induce a therapeutic immune response; however, Tregs eventually inhibit the antitumor immune response and thereby limit the power of cancer immunotherapies. In tumor-bearing mice, we found that Tregs within the tumor preferentially express the cell surface markers CTLA-4 and OX40. We show that intratumoral coinjection of anti-CTLA-4 and anti-OX40 together with CpG depleted tumor-infiltrating Tregs. This in situ immunomodulation, which was performed with low doses of antibodies in a single tumor, generated a systemic antitumor immune response that eradicated disseminated disease in mice. Further, this treatment modality was effective against established CNS lymphoma with leptomeningeal metastases, sites that are usually considered to be tumor cell sanctuaries in the context of conventional systemic therapy. These results demonstrate that antitumor immune effectors elicited by local immunomodulation can eradicate tumor cells at distant sites. We propose that, rather than using mAbs to target cancer cells systemically, mAbs could be used to target the tumor infiltrative immune cells locally, thereby eliciting a systemic immune response.
View details for DOI 10.1172/JCI64859
View details for Web of Science ID 000320093100018
Design, synthesis, and evaluation of quinazoline T cell proliferation inhibitors
BIOORGANIC & MEDICINAL CHEMISTRY
2010; 18 (17): 6404-6413
Selective elimination of alloreactive cells was carried out in the set-up of T-cell-mediated immunotherapy in an effort to gain the benefits of hematopoietic allogeneic transplantation while reducing the risk of GVHD. Low MW chemical compounds were screened for their effect on T-cell-mediated immune responses of murine- and human-derived lymphocytes. Selected compounds were further tested in secondary MLR assays in which sensitization to alloantigens was carried out in vitro, in the presence or absence of a given compound, followed by exposure to related and unrelated alloantigens or T-cell mitogenic stimulation. At a low concentration of <1 μM, a quinazoline derivative named AO#349 [2-(3,4,5-trimethoxyphenyl)-N-p-tolylquinazolin-4-amine], was able to induce 78-90% inhibition of a selective allogeneic response while retaining >92% immune reactivity to unrelated alloantigens and mitogenic stimuli in vitro. Following allogeneic sensitization in the presence of AO#349, elimination of alloreactivity to the priming alloantigens was also proved in a murine model of GVHD: 10 out of 15 sub-lethally irradiated mice inoculated with these sensitized cells were GVHD-free for >200 days. AO#349 was efficient in induction of a selective elimination of alloreactivity and should be considered for clinical application in allogeneic cell-mediated immunotherapy.
View details for DOI 10.1038/bmt.2011.198
View details for Web of Science ID 000305276200011
View details for PubMedID 22020024
A color discriminating broad range cell staining technology for early detection of cell transformation.
Journal of carcinogenesis
2009; 8: 16-?
We report here on a class of quinazoline molecules that inhibit T cell proliferation. The most potent compound N-p-tolyl-2-(3,4,5-trimethoxyphenyl)quinazolin-4-amine (S101) and its close analogs were found to inhibit the proliferation of T cells from human peripheral blood mononuclear cells (PBMC) and Jurkat cells, with IC(50) in the sub-micromolar range. The inhibitor induced G2 cell cycle arrest but did not inhibit IL-2 secretion. The anti-proliferative effect correlated with inhibition of the tyrosine phosphorylation of SLP-76, a molecular element in the signaling pathway of the T cell receptor (TCR). The inhibitor restrained proliferation of lymphocytes with much higher potency than non-hematopoietic cells. This new class of specific T cell proliferation inhibitors may serve as lead molecules for the development of agents aimed at diseases in which T cell signaling plays a role and agents to induce tolerance to grafted tissues or organs.
View details for DOI 10.1016/j.bmc.2010.07.004
View details for Web of Science ID 000281203300022
View details for PubMedID 20674367
Background: Advanced diagnostic tools stand today at the heart of successful cancer treatment. CellDetect(R) is a new histochemical staining technology that enables color discrimination between normal cells and a wide variety of neoplastic tissues. Using this technology, normal cells are colored blue/green, while neoplastic cells color red. This tinctorial difference coincides with clear morphological visualization properties, mainly in tissue samples. Here we show that the CellDetect(R) technology can be deployed to distinguish normal cells from transformed cells and most significantly detect cells in their early pre-cancerous transformed state. Materials and Methods: In tissue culture, we studied the ability of the CellDetect(R) technology to color discriminate foci in a number of two stage transformation systems as well as in a well defined cellular model for cervical cancer development, using HPV16 transformed keratinocytes. Results: In all these cellular systems, the CellDetect(R) technology was able to sensitively show that all transformed cells, including pre-cancerous HPV 16 transformed cells, are colored red, whereas normal cells are colored blue/green. The staining technology was able to pick up: (i) early transformation events in the form of small type 1 foci (non-invasive, not piled up small, with parallel alignment of cells), and (ii) early HPV16 transformed cells, even prior to their ability to form colonies in soft agar. The study shows the utility of the CellDetect(R) technology in early detection of transformation events.
View details for DOI 10.4103/1477-3163.58372
View details for PubMedID 20023366