POS1036 COLLAGEN TURNOVER MARKERS ARE ASSOCIATED WITH ACTIVE PSORIATIC ARTHRITIS AND DECREASE WITH GUSELKUMAB TREATMENT IN A PHASE-3 CLINICAL TRIAL

Background:

Guselkumab (GUS), an interleukin-23p19-subunit monoclonal antibody, demonstrated efficacy compared to placebo (PBO) in reducing skin and musculoskeletal signs and symptoms in patients with active psoriatic arthritis (PsA) in two phase-3 studies, DISCOVER-1 & -2, and in retarding structural damage in DISCOVER-2.1,2

Objectives:

To evaluate tissue-derived extracellular matrix (ECM) products3,4 in serum of PsA patients in the DISCOVER-2 study and their relationship with radiographic damage, clinical response, and impact of treatment.

Methods:

In DISCOVER-2, patients were treated with GUS 100 mg at Week (w) 0, 4, then every 8w (q8w); GUS 100 mg every 4w (q4w); or matching PBO. At w24, PBO patients were crossed over to GUS q4w. A total of 11 serum biomarkers of ECM collagen formation (PRO-C1, PRO-C2, PRO-C3, PRO-C4, and PRO-C6) and degradation (C1M, C2M, C3M, C4M, C6M, and COL10) were measured (by Nordic Bioscience) in a subset of 260 patients from the DISCOVER-2 program at Weeks 0, 4, 24, & 52 and in 76 healthy controls matched for age, sex, and ethnicity. PsA patients were selected randomly, though enriching for subjects with greatest radiographic changes, at Weeks 24 and 52. Significance defined by p<0.05 and |fold difference| ≥1.25.

Results:

At baseline, collagen degradation markers C1M, C3M, C4M, C6M and collagen formation markers PRO-C3 and PRO-C6 were significantly higher in the serum of PsA patients compared to matched healthy controls. Baseline C3M, C4M, and C6M were positively correlated to baseline skin and joint disease; baseline C1M, C3M, C4M, C6M, and PRO-C1 were positively correlated to baseline radiographic damage (data not shown). Levels of C1M (a maker indicating breakdown of collagen type I, the major collagen subtype in the bone) were significantly decreased after 24w treatment with GUS (Figure 1), reaching significant differences from placebo with the GUS 100 mg q4w group. For the PBO patients who crossed over to GUS at w24, there was also a reduction in this marker observed at w52 (Figure 1). In patients treated with GUS or PBO, there were no significant differences in baseline expression levels of the analytes in responders (patients achieving ACR20 at w24) compared with non-responders. However, ACR20 responders in the combined GUS group had a significantly greater reduction in C1M levels compared to non-responders (p=0.0065) at w24.

Conclusion:

This work provides evidence that collagen biomarkers in serum are dysregulated in patients with PsA compared to healthy controls, and that GUS impacts levels of these proteins. Importantly, C1M serves as a biomarker that tracks with joint response. We observed a greater reduction in C1M in ACR responders compared to non-responders, providing insight into how GUS may be working to protect from degradation of bone in PsA.

References:

[1]Deodhar A et al. Lancet 2020;395:1115-1125

[2]Mease PJ et al. Lancet 2020;395:1126-1136

[3]Gudmann NS et al. Clin Exp Rheumatol 2017;35:653-659

[4]Sardar S et al. Annals of the Rheum Dis 2019;78(Suppl 2): https://ard.bmj.com/content/78/Suppl_2/867.1

Disclosure of Interests:

Georg Schett Speakers bureau: AbbVie, BMS, Celgene, Janssen, Lilly, Novartis, Roche, UCB, Consultant of: AbbVie, BMS, Celgene, Janssen, Lilly, Novartis, Roche, UCB, Matthew J Loza Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Arumugam Palanichamy Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Oliver FitzGerald Speakers bureau: AbbVie, Amgen, BMS, Celgene, Janssen, Lilly, Novartis, Consultant of: AbbVie, Amgen, BMS, Celgene, Janssen, Lilly, Novartis, Christopher T. Ritchlin Speakers bureau: AbbVie, Amgen, Gilead, Janssen, Lilly, Novartis, Pfizer, UCB, Consultant of: AbbVie, Amgen, Gilead, Janssen, Lilly, Novartis, Pfizer, UCB, Frederic Baribaud Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC, Kristen Sweet Shareholder of: Johnson & Johnson, Employee of: Janssen Research & Development, LLC.

OP0161 ASSOCIATION OF BASELINE CYTOTOXIC GENE EXPRESSION WITH USTEKINUMAB RESPONSE IN SYSTEMIC LUPUS ERYTHEMATOSUS

Background:

Systemic Lupus Erythematous (SLE) is a clinically and biologically diverse disease, for which only one new therapy has been approved in the past 60 years. In a phase 2 trial on patients with mild-to-moderate SLE, ustekinumab (UST) improved clinical and laboratory measures of disease activity compared with placebo (PBO).1

Objectives:

We previously reported an association of IFN-γ reduction with response to UST,2suggesting an impact on the IL12/Th1 axis. To extend these findings, we performed unbiased transcriptomic analysis from baseline whole blood samples to identify genes that discriminate UST responders (UST-R) from non-responders (UST-NR) using the primary endpoint of Systemic Lupus Erythematosus Responder Index (SRI)-4 at week 24 to define response.

Methods:

UST was studied in a Ph2 PBO-controlled study of 102 patients with seropositive SLE and active disease despite standard therapy. Patients were randomized 3:2 to receive IV UST 6 mg/kg or placebo followed by subcutaneous injections of UST 90 mg or PBO every 8 weeks. Whole blood gene expression at baseline was measured via microarray using RNA samples from 100 patients, as samples from 2 patients failed quality control. An unbiased approach was used to identify gene signatures present at baseline that associate with UST response. Recombinant IL-12 or IL-23 was incubatedin vitrowith whole blood from 6 healthy donors for 24h and RNA-Seq was performed to determine the effect of these treatments on representative genes comprising the UST response signature.

Results:

A non-biased machine learning algorithm identified a 9-gene whole blood signature composed primarily of cytotoxic cell-associated transcripts (PRF1, KLRD1, GZMH, NKG7, GNLY, FGFBP2, TRGC2, TARP, TRGV2) that was enriched at baseline in UST-R vs UST-NR. By Gene Set Variation Analysis, the cytotoxic signature enrichment in UST-NR was less at baseline than both UST-R and a healthy control cohort (P=0.0087, P=0.056, respectively), whereas UST-R cytotoxic gene enrichment was similar to healthy controls (P=0.31). No significant difference in cytotoxic signature enrichment was observed at baseline between PBO responders and PBO non-responders or healthy controls (Figure). Enrichment levels of the cytotoxic gene signature remained stable over time in PBO and UST-NR groups while a trend of decreased cytotoxic signature was observed in UST-R, although never reaching levels seen in UST-NR. To begin to understand the relationship between IL-12 and IL-23, the targets of UST, and the cytotoxic signature, whole blood was stimulated with these cytokinesin vitro. Recombinant IL-12, but not IL-23, resulted in increased expression of representative members of this cytotoxic gene signature.

Conclusion:

We identified a novel cytotoxic signature in baseline blood samples that associated with UST response in SLE. The observation that IL-12 can increase this signaturein vitroand that IL-12 is a robust inducer of cytotoxic cell activity3as well as IFN-γ3suggests an important role of IL-12 blockade in the mechanism of action of UST in SLE.

References:

[1]van Vollenhoven RF. Lancet. 2018;392:1330-39

[2]Jordan. ACR 2018 Abstract # 2951

[3]G. Trinchieri. Nat Rev Immunol. 2003;3:133-46

Figure.

Disclosure of Interests:

Loqmane Seridi Employee of: Janssen Research & Development, LLC, Matteo Cesaroni Employee of: Janssen Research & Development, LLC, Matthew J Loza Employee of: Janssen Research & Development, LLC, Jessica Schreiter Employee of: Janssen Research & Development, LLC, Kristen Sweet Employee of: Janssen Research & Development, LLC, Yevgeniya Orlovsky Employee of: Janssen Research & Development, LLC, Spring House, PA, United States of America, Isabelle Baribaud Employee of: Janssen Research & Development, LLC, Ashley Orillion Employee of: Janssen Research & Development, LLC, Peter Lipsky Consultant of: Horizon Therapeutics, Ronald van Vollenhoven Grant/research support from: AbbVie, Amgen, Arthrogen, Bristol-Myers Squibb, GlaxoSmithKline (GSK), Janssen Research & Development, LLC, Lilly, Pfizer, Roche, and UCB, Consultant of: AbbVie, AstraZeneca, Biotest, Bristol-Myers Squibb, Celgene, Crescendo Bioscience, GSK, Janssen, Lilly, Medac, Merck, Novartis, Pfizer, Roche, UCB and Vertex, Speakers bureau: AbbVie, AstraZeneca, Biotest, Bristol-Myers Squibb, Celgene, Crescendo Bioscience, GlaxoSmithKline, Janssen, Lilly, Merck, Novartis, Pfizer, Roche, UCB, Vertex, Bevra H. Hahn Grant/research support from: Janssen Research & Development, LLC, George Tsokos Grant/research support from: Janssen Research & Development, LLC, Marc Chevrier Employee of: Janssen Research & Development, LLC, Shawn Rose Employee of: Janssen Research & Development, LLC, Frederic Baribaud Shareholder of: Janssen Research & Development, LLC, Employee of: Janssen Research & Development, LLC, Jarrat Jordan Employee of: Janssen Research & Development, LLC

OP0229 GUSELKUMAB INDUCES SUSTAINED REDUCTION IN ACUTE PHASE PROTEINS AND TH17 EFFECTOR CYTOKINES IN ACTIVE PSORIATIC ARTHRITIS IN TWO PHASE-3 CLINICAL TRIALS (DISCOVER-1 AND DISCOVER-2)

Background:

Guselkumab (GUS), an IL-23 inhibitor monoclonal antibody (Mab) that specifically binds to the IL-23p19 subunit, demonstrated efficacy compared to placebo (PBO) in reducing skin and musculoskeletal signs and symptoms in patients (pts) with active psoriatic arthritis (PsA) in two phase-3 studies, DISCOVER 1 & 2.1,2Previous results from a GUS PsA Phase-2 trial3and Ustekinumab (UST, anti-IL12/23p40 MAb) PsA Phase-3 trials (PSUMMIT 1 & 2)4showed associations of baseline IL-17A, IL-17F, and CRP with baseline disease characteristics, and associations of GUS-induced cytokine reductions with clinical responses.

Objectives:

To investigate plausible cytokine expression in PsA and alterations after exposure to GUS therapy.

Methods:

In DISCOVER 1 & 2, pts were treated with GUS 100 mg at Wk 0, 4, then every 8Wks (q8w); GUS 100mg q4w; or matching PBO. 21 serum biomarkers were measured in a random subset of 300 PsA pts from the DISCOVER program at Weeks (Wks) 0, 4, & 24 and in 34 healthy controls matched for age, sex, and ethnicity. Serum proteins measured were acute phase reactants CRP & SAA (Meso Scale Discovery (MSD) Platform) and inflammatory cytokines/chemokines: Th17 effector cytokines IL-17A, IL-17F, & IL-22 (Single Molecule Counting Erenna® Immunoassay Platform) and soluble ICAM-1, soluble VCAM-1, IL-6, CXCL-8, IL-10, IL-13, IL-12p70, CCL22, IFN-γ, CCL2, CCL4, TNFα, IL-1β, IL-2, IL-4 (MSD), & YKL-40 (Quantikine Immunoassay). Serum IL-17A, IL-17B, & CRP measured in the Phase-3 PSUMMIT trials of UST for PsA4were included for comparison with GUS.

Results:

At baseline, serum levels of acute phase proteins CRP, SAA, & IL-6, and Th17-effector cytokines IL-17A & IL-17F were elevated in pts with PsA compared with healthy controls (p<0.05, geometric mean ≥ 40% higher, FIG 1). There was no significant dysregulation in the other cytokines measured in PsA pts compared to healthy controls. Baseline IL-17A, IL-17F, IL-22, & CCL22 were significantly associated with baseline psoriasis disease activity (Body Surface Area & Psoriatic Area and Severity Index, Spearman Signed Rank p<0.05, r>0.25). Baseline CRP, SAA, IL-6, & YKL40 were significantly associated with baseline joint disease (Disease Activity Score 28-CRP, Spearman p<0.05, r>0.25). Baseline SAA, IL-6, IL-17A, & IL-17F were higher in pts with prior TNF inhibitor exposure than without (p<0.05, geometric mean ≥ 40% higher), although pts with PsA both with and without prior TNF inhibitor had higher levels than the healthy control set.

GUS treatment resulted in decreases in serum CRP, SAA, IL-6, IL-17A, IL-17F, & IL-22 that were significantly greater than PBO as early as Week 4 (FIG 1). These protein levels continued to decrease through Wk 24 in GUS-treated pts with both dosing regimens (p<0.05, geometric mean decrease from baseline ≥ 33%). Further, Wk 24 IL-17A & IL-17F levels for pts treated with either dose of GUS were not significantly different from healthy controls, suggesting a normalization of peripheral effector cytokines associated with the IL-23/Th17 axis following treatment with GUS. Effects on IL-17A/IL-17F were greater in GUS treated pts than UST treated pts, while CRP levels were similar in both programs (FIG 2).

Conclusion:

Comprising a strong pharmacodynamic effect, GUS treatment reduced serum protein levels of acute phase and Th17-effector cytokines (whose elevations at baseline were associated with PsA disease characteristics) and achieved comparable levels to those in healthy controls. In pts with PsA, reductions of IL-17A and IL-17F by GUS were of greater magnitude than those by UST.

References:

[1]Deodhar et al. ACR 2019, abs #807. Arth Rheumatol. 2019;71 S10: 1386

[2]Mease et al. ACR 2019, abs #L13. Arth Rheumatol. 2019;71 S10:5247

[3]Siebert et al. EULAR 2019, abs #479. Ann Rheum Dis. 2019;78 S2:293

[4]Siebert et al. Arth Rheumatol. 2019;71:1660

Acknowledgments:

None

Disclosure of Interests:

Stefan Siebert Grant/research support from: BMS, Boehringer Ingelheim, Celgene, GlaxoSmithKline, Janssen, Novartis, Pfizer, UCB, Consultant of: AbbVie, Boehringer Ingelheim, Janssen, Novartis, Pfizer, UCB, Speakers bureau: AbbVie, Celgene, Janssen, Novartis, Iain McInnes Grant/research support from: Bristol-Myers Squibb, Celgene, Eli Lilly and Company, Janssen, and UCB, Consultant of: AbbVie, Bristol-Myers Squibb, Celgene, Eli Lilly and Company, Gilead, Janssen, Novartis, Pfizer, and UCB, Matthew J Loza Employee of: Janssen Research & Development, LLC, Keying Ma Employee of: Janssen Research & Development, LLC, Karen Leander, Employee of: Janssen Research & Development, LLC, Vani Lakshminarayanan Employee of: Janssen Research & Development, LLC, Carol Franks Employee of: Janssen Research & Development, LLC, Philip Cooper Employee of: Janssen Research & Development, LLC, Kristen Sweet Employee of: Janssen Research & Development, LLC

Phase 2a, randomized, double-blind, placebo-controlled, multicentre, parallel-group study of an H4 R-antagonist (JNJ-39758979) in adults with uncontrolled asthma

BACKGROUND

The effects of H₄ R antagonists in preclinical asthma models support the study of antagonists of the H₄ R in the treatment of asthma in humans. JNJ-39758979 is a potent and highly selective oral H₄ R antagonist.

OBJECTIVE

We sought to evaluate the safety and efficacy of the H₄ R-antagonist JNJ-39758979 in adult patients with uncontrolled asthma.

METHODS

One hundred and fifteen eligible patients were randomly assigned to JNJ-39758979 300 mg or placebo once daily for 12 weeks in this phase 2a, double-blind, multicenter, placebo-controlled study. Primary efficacy was assessed via week-12 change from baseline in pre-bronchodilator forced expiratory volume in 1 second (FEV₁ ). Secondary efficacy assessments included patient-reported outcome (PRO) asthma assessments (Asthma Daily Diary data [AM and PM peak expiratory flow rate, number of puffs of albuterol/salbutamol, the presence of nocturnal awakenings and asthma symptom score]).

RESULTS

The study did not meet the primary end-point. However, nominally significant improvements in pre-bronchodilator FEV₁ were observed with JNJ-39758979 versus placebo at week 12 in pre-specified subgroups with elevated exhaled nitric oxide, sputum eosinophils or blood eosinophils at baseline. Nominally significant improvements across PRO assessments were consistently observed in the overall population, as well as in eosinophilic subgroups. Safety, such as adverse event rates, was comparable between JNJ-39758979 and placebo. No serious adverse events were reported. No clinically relevant changes in laboratory values were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

The findings suggest potential benefit of H₄ R antagonists on lung function and asthma control in eosinophilic asthma patients and warrant further evaluation of this mechanism in asthma with eosinophilic inflammation. NCT00946569.

Longitudinal stability of asthma characteristics and biomarkers from the Airways Disease Endotyping for Personalized Therapeutics (ADEPT) study

Background

Asthma is a biologically heterogeneous disease and development of novel therapeutics requires understanding of pathophysiologic phenotypes. There is uncertainty regarding the stability of clinical characteristics and biomarkers in asthma over time. This report presents the longitudinal stability over 12 months of clinical characteristics and clinically accessible biomarkers from ADEPT.

Methods

Mild, moderate, and severe asthma subjects were assessed at 5 visits over 12 months. Assessments included patient questionnaires, spirometry, bronchodilator reversibility, fractional exhaled nitric oxide (FENO), and biomarkers measured in induced sputum.

Results

Mild (n = 52), moderate (n = 55), and severe (n = 51) asthma cohorts were enrolled from North America and Western Europe. For all clinical characteristics and biomarkers, group mean data showed no significant change from visit to visit. However, individual data showed considerable variability. FEV1/FVC ratio showed excellent reproducibility while pre-bronchodilator FEV1 and FVC were only moderately reproducible. Of note bronchodilator FEV1 reversibility showed low reproducibility, with the nonreversible phenotype much more reproducible than the reversible phenotype. The 7-item asthma control questionnaire (ACQ7) demonstrated moderate reproducibility for the combined asthma cohorts, but the uncontrolled asthma phenotype (ACQ7 > 1.5) was inconstant in mild and moderate asthma but stable in severe asthma. FENO demonstrated good reproducibility, with the FENO-low phenotype (FENO < 35 ppb) more stable than the FENO-high phenotype (FENO ≥ 35 ppb). Induced sputum inflammatory phenotypes showed marked variability across the 3 sputum samples taken over 6 months.

Conclusions

The ADEPT cohort showed group stability, individual stability in some parameters e.g. low FEV1/FVC ratio, and low FENO, but marked individual variability in other clinical characteristics and biomarkers e.g. type-2 biomarkers over 12 months. This variability is possibly related to seasonal variations in climate and allergen exposure, medication changes and acute exacerbations. The implications for patient selection strategies based on clinical biomarkers may be considerable.

Asthma characteristics and biomarkers from the Airways Disease Endotyping for Personalized Therapeutics (ADEPT) longitudinal profiling study

BACKGROUND

Asthma is a heterogeneous disease and development of novel therapeutics requires an understanding of pathophysiologic phenotypes. The purpose of the ADEPT study was to correlate clinical features and biomarkers with molecular characteristics, by profiling asthma (NCT01274507). This report presents for the first time the study design, and characteristics of the recruited subjects.

METHODS

Patients with a range of asthma severity and healthy non-atopic controls were enrolled. The asthmatic subjects were followed for 12 months. Assessments included history, patient questionnaires, spirometry, airway hyper-responsiveness to methacholine, fractional exhaled nitric oxide (FENO), and biomarkers measured in induced sputum, blood, and bronchoscopy samples. All subjects underwent sputum induction and 30 subjects/cohort had bronchoscopy.

RESULTS

Mild (n = 52), moderate (n = 55), severe (n = 51) asthma cohorts and 30 healthy controls were enrolled from North America and Western Europe. Airflow obstruction, bronchodilator response and airways hyperresponsiveness increased with asthma severity, and severe asthma subjects had reduced forced vital capacity. Asthma control questionnaire-7 (ACQ7) scores worsened with asthma severity. In the asthmatics, mean values for all clinical and biomarker characteristics were stable over 12 months although individual variability was evident. FENO and blood eosinophils did not differ by asthma severity. Induced sputum eosinophils but not neutrophils were lower in mild compared to the moderate and severe asthma cohorts.

CONCLUSIONS

The ADEPT study successfully enrolled asthmatics across a spectrum of severity and non-atopic controls. Clinical characteristics were related to asthma severity and in general asthma characteristics e.g. lung function, were stable over 12 months. Use of the ADEPT data should prove useful in defining biological phenotypes to facilitate personalized therapeutic approaches.

Atopy, asthma, and experimental approaches based on the linear model of T cell maturation

The linear model of maturation of IFN-gamma-producing cells from a proliferative pool of type 2 cytokine-producing T cells represents a fundamental shift in interpreting how changes in cytokine production by T cell populations are regulated. A major tenet of this model is antigen-independent, bystander proliferation of type 2 T cells and their maturation to IFN-gamma+ cells. Both clinical observations and prevailing theories of immune system development in asthma are consistent with this highly interpretative in vitro model, which allows unambiguous characterization of the modulation of the intrinsic features of T cell proliferation and differentiation by environmental and genetic factors. Hypotheses based on the linear model of T cell maturation are readily testable and should lead to a greater understanding of not only allergen-specific responses, but also the non-specific, bystander effects associated with specific responses to allergens or pathogens. Topics to be discussed in the context of the linear model of T cell maturation in this review include: (1) allergic responses to an inciting allergen that may enhance sensitivity to subsequent yet different allergens; (2) dampening the preferential accumulation of type 2 T cells during a typical immune response against viral and bacterial pathogens; (3) allergen-independent sensitization in asthmatics: (4) the 'hygiene hypothesis' for the reported increased allergy development in industrialized countries; (5) elevated IFN-gamma levels in asthmatics, in addition to the expected high levels of type 2 cytokines; (6) testing the effects of inflammatory mediators, as well as various anti-inflammation therapies on T cell maturation; and (7) testing the influence of gene variation on T cell maturation.

Final steps of natural killer cell maturation: a model for type 1-type 2 differentiation?

Analysis of cytokine and differentiation antigen expression in human natural killer (NK) cells revealed that interleukin 13 (IL-13) and interferon gamma (IFN-gamma) are produced at sequential stages during irreversible IL-12-induced differentiation. In human NK cell clones, polyclonal CD3-CD161+CD56- cells and peripheral lymphocytes, IL-4 induced the proliferation of both IL-13+ NK and T cells, whereas IL-12 allowed a proliferation-independent accumulation of IFN-gamma+ cells. These data disproved the NK1-NK2 hypothesis and challenge the current T helper 1 (TH1)-TH2 paradigm. We propose that the cytokine environment regulates a type 2-->0-->1 developmental progression, with IL-12 needed for terminal differentiation and IL-4 delaying this process, rather than a type 1 versus type 2 decision of a type 0 cell.

Human NKT cells mediate antitumor cytotoxicity directly by recognizing target cell CD1d with bound ligand or indirectly by producing IL-2 to activate NK cells

alpha-Galactosylceramide (alphaGalCer) stimulates NKT cells and has antitumor activity in mice. Murine NKT cells may directly kill tumor cells and induce NK cell cytotoxicity, but the mechanisms are not well defined. Newly developed human CD1d/alphaGalCer tetrameric complexes were used to obtain highly purified human alphaGalCer-reactive NKT cell lines (>99%), and the mechanisms of NKT cell cytotoxicity and activation of NK cells were investigated. Human NKT cells were cytotoxic against CD1d(-) neuroblastoma cells only when they were rendered CD1d(+) by transfection and pulsed with alphaGalCer. Four other CD1d(-) tumor cell lines of diverse origin were resistant to NKT cells, whereas Jurkat and U937 leukemia cell lines, which are constitutively CD1d(+), were killed. Killing of the latter was greatly augmented in the presence of alphaGalCer. Upon human CD1d/alphaGalCer recognition, NKT cells induced potent cytotoxicity of NK cells against CD1d(-) neuroblastoma cell lines that were not killed directly by NKT cells. NK cell activation depended upon NKT cell production of IL-2, and was enhanced by secretion of IFN-gamma. These data demonstrate that cytotoxicity of human NKT cells can be CD1d and ligand dependent, and that TCR-stimulated NKT cells produce IL-2 that is required to induce NK cell cytotoxicity. Thus, NKT cells can mediate potent antitumor activity both directly by targeting CD1d and indirectly by activating NK cells.

B-Myb overexpression results in activation and increased Fas/Fas ligand-mediated cytotoxicity of T and NK cells

The human B-myb gene encodes a transcriptional regulator that plays an important role in cell cycle progression, differentiation, and survival. To assess the in vivo role of B-myb, we investigated the phenotype of mouse transgenic lines in which B-Myb expression in lymphoid tissues was driven by the LCK proximal promoter. Overexpression of B-Myb had no measurable effect on the subsets of splenic and thymic lymphocytes, but was associated with increased expression of Fas ligand in NK and T cells. B-Myb-overexpressing splenocytes expressed higher IFN-gamma levels and contained higher percentages of cytokine-producing cells than wild-type (wt) splenocytes, as detected by Western blot analysis and ELISPOT assays, respectively. Ex vivo-cultured transgenic thymocytes and splenocytes had decreased survival compared with the corresponding cells from wt mice, possibly dependent on increased expression of Fas ligand. In addition, Fas ligand-dependent cytotoxicity of transgenic T and NK cells was significantly higher than that mediated by their wt counterparts. Together, these results indicate that B-Myb overexpression results in T and NK cell activation and increased cytotoxicity. Therefore, in addition to its well-established role in proliferation and differentiation, B-myb also appears to be involved in activation of NK and T cells and in their regulation of Fas/Fas ligand-mediated cytotoxicity