Abstract 1422: A novel agonist of CD137 shows immunoprevention efficacy against various tumors by invoking an innate immune surveillance mechanism

Introduction: Immune checkpoints have been the focus of intense research due to their critical roles in regulating immune responses. The CD137 is an immune checkpoint stimulator has pleiotropic immune functions along with its canonical role in driving CD8+ T cell responses. Using a novel form of its natural ligand (SA-4-1BBL) as a single agent, we recently showed its robust cancer immunoprevention efficacy against various transplantable tumor types in mice. In this study, we report its efficacy in a spontaneous tumor model and elucidate the mechanistic basis of prevention.

Study design: Mice were treated subcutaneously with SA-4-1BBL protein twice, two weeks apart, and challenged with various tumor types 1-14 weeks later. Animals were monitored for tumor growth. The LSL-KrasG12D mice, as a model of spontaneous lung cancer, were intranasally infected with 2.5 × 107 PFUs of adenoviral-cre to induce cancer. Animals were treated with SA-4-1BBL twice, two weeks apart, pre or post-infection with adeno and euthanized at various times to collect the lung and lymphoid tissues for histopathology and flow cytometry.

Results: Pretreatment with SA-4-1BBL was effective in preventing the growth of various transplantable tumors, B16-F10 melanoma, 3LL lung cancer, A20 lymphoma, 4T1 breast cancer, in different mouse strains. Treatment with SA-4-1BBL induced a window of protection against tumors that lasted over 14 weeks. SA-4-1BBL treatment significantly reduced the lung tumor burden in LSL-KrasG12D mice that was associated with increased absolute numbers of CD137+CD4+CD44hi T cells and CD137+NKG2D+NK cells expressing IFN-γ and TNF-α. A blocking antibody to NKG2D reversed the immunopreventive efficacy of SA-4-1BBL in the 3LL and B16-F10 tumor models, providing direct evidence for the role of this receptor in cancer immunoprevention. Gamma/delta T cells did not play a role in the cancer prevention efficacy of SA-4-1BBL as mice lacking these cells showed protection.

Conclusions: These results demonstrate that SA-4-1BBL invokes an innate immune surveillance mechanism orchestrated by cross-communication between memory-like CD4+ T cells and NK cells with long-term protection against various tumor types. Funded in parts by NIH R41CA199956, T32HL134644, NCI R25CA134283, and Kentucky KSTC-184-512-16-237 awards.

Citation Format: Haval Shirwan, Lalit Batra, Qingsheng Li, Mohammad T. Malik, Pradeep Shrestha, Nejat Egilmez, Esma S. Yolcu. A novel agonist of CD137 shows immunoprevention efficacy against various tumors by invoking an innate immune surveillance mechanism [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1422.

Resistance to Anti-PD-1 Therapy is mediated via the Microbiota-Th17-Prostoglandin E2 Axis in the LSLKrasG12D Lung Cancer Model

We previously demonstrated that anti-PD-1 antibody mediated activation of type 17 T-cells undermined checkpoint inhibitor therapy in the LSLKrasG12D murine lung cancer model. In this study we confirm that the Th17 subset is the primary driver of resistance to anti-PD-1; demonstrate that the ontogeny of dysplasia-associated Th17 cells is driven by microbiota-conditioned macrophages; and identify IL-17-COX-2/Prostoglandin E2 (PGE2) axis as the mediator of CD8+ cytotoxic T-lymphocyte (CTL) de-sensitization to checkpoint inhibitor therapy. Specifically, anti-PD-1 treatment of CD4+ T-cell RORc-deficient LSLKrasG12D mice resulted in a 50% increase in CTL cytotoxicity and a 2.2-fold reduction in tumor burden confirming the critical role of Th17 cells in resistance to therapy. Lung-specific depletion of microbiota reduced Th17 cell prevalence and tumor burden by ~2 and ~1.5 fold, respectively, establishing a link between microbiota and the Th17-driven tumorigenesis. Importantly, interstitial macrophages from microbiota sufficient, but not from microbiota-deficient, mice polarized naïve CD4+ T-cells towards a Th17 phenotype, highlighting their role in bridging microbiota and lung Th17 immunity. Neutralization of IL-17 diminished COX-2/PGE2 levels, whereas inhibition of COX-2 rescued CTL activity and restored tumor suppression in anti-PD-1 antibody-treated mice, revealing the molecular basis of IL-17-driven anti-PD-1 resistance. The clinical implications of these findings are discussed.

Supported by grant from DOD grant (to N.E., OGMB190737) and in part through the NIH/NIGMS P20-GM135004 (1P20GM135005-01)

Dietary low-fiber promotes resistance to immune checkpoint inhibitor immunotherapy in the LSL-KrasG12D Lung Cancer Model

Dietary fiber interaction with the gut microbiota impact gut microbiota composition and is likely to play a large role in affecting the efficacy of immune checkpoint inhibitors (ICIs) therapy. Here we show that a diet with low-fiber promoted lung tumor development and reduced tumor-bearing animal long-term survival in both prophylactic early disease and established late disease of murine LSL-KrasG12D lung cancer model, which displays low neoantigen burden and is refractory to anti-PD-1 antibody. In this model, the administration of anti-PD-1 in the presence of IL-17 neutralization resulted in tumor suppression, indicating that limited intrinsic neoantigen alone was not the primary determinant of resistance to ICIs therapy. Interestingly, dietary low-fiber led to reduced anti-tumor effect of anti-PD-1 and anti-IL-17 partially in gut microbiota-dependent manner. Fecal microbiota transplantation from mice fed low-fiber diet also enhanced lung tumor burden. An altered immune response with significantly reduced gut lamina propria RORgt+IL-17A+ Th17 cells, lung Foxp3+Treg cells, enhanced lung Th17 cells, but no alteration of lung gdTCR+ cells were found in mice fed low-fiber diet. Furthermore, a low-fiber diet led to significant changes in metabolites including a high level of serine in the plasma of animals. Mice fed normal chow with drinking water containing serine increased lung tumorigenesis. Our study demonstrates a functional interconnection between dietary fiber and spontaneous lung tumor development.

Supported by grant from NIH/NIGMS(P20-GM135004)

Abstract 1954: Tracking of orally-administered particles within the gastrointestinal tract of murine models using multispectral optoacoustic tomography

While particle carriers have potential to revolutionize disease treatment, using these carriers requires knowledge of spatial and temporal biodistribution. The goal of this study was to track orally administered particle uptake and trafficking through the murine gastrointestinal (GI) tract using multispectral optoacoustic tomography (MSOT).

Polylactic acid (PLA) particles encapsulating AlexaFluor 680 (AF680) dye conjugated to bovine serum albumin (BSA) were orally gavaged into mice. Particle uptake and trafficking were observed using MSOT imaging with subsequent confirmation of particle uptake via fluorescent microscopy. Mice treated with PLA-AF680-BSA particles exhibited MSOT signal within the small bowel wall at 1 and 6 h, colon wall at 6, 12, and 24 h, and mesenteric lymph node 24 and 48h. Particle localization identified using MSOT correlated with fluorescence microscopy. Despite the potential of GI tract motion artifacts, MSOT allowed for teal-time tracking of particles within the GI tract in a non-invasive and real-time manner.

Future use of MSOT in conjunction with particles containing both protein-conjugated fluorophores as well as therapeutic agents could allow for non-invasive, real time tracking of particle uptake and drug delivery.

Citation Format: Neal Bhutiani, Abhilash Samykutty, Kelly McMasters, Nejat Egilmez, Lacey R. McNally. Tracking of orally-administered particles within the gastrointestinal tract of murine models using multispectral optoacoustic tomography [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1954.

Abstract 1863: Non-invasive imaging of colitis using multispectral optoacoustic tomography

Background: Currently, several non-invasive modalities, including MRI and PET, are being investigated to identify early intestinal inflammation, longitudinally monitor disease status, or detect dysplastic changes in patients with inflammatory bowel disease (IBD). Currently, multispectral optoacoustic tomography (MSOT; often in combination with ultrasound) has been used to effectively image tumor xenografts as well as several orthotopic tumor models, including pancreatic adenocarcinoma, but not to specifically assess inflammatory or dysplastic changes in the bowel in murine models. Here, we assess the applicability and utility of (MSOT) in evaluating the presence and severity of colitis.

Methods: Nine 6-7 week old C57B/6 mice underwent antibiotic depletion of gastrointestinal flora before inoculation with enterotoxic Bacteroides fragilis to induce colitis. Mice were then anesthetized, depilated, imaged from their superior thorax to inferior pelvis using MSOT. Mice were evaluated prior to bacterial inoculation, 2 days after inoculation, and 7 days after inoculation. MSOT values for oxygenated and deoxygenated hemoglobin were determined using MSOT imaging software and compared using linear regression. At each timepoint, three mice underwent colonoscopy prior to euthanasia and colon processing for histology.

Results: Mice with bacterially-induced colitis demonstrated a temporally-associated increase in mesenteric and colonic vascularity, with an increase in mean signal intensity of oxygenated hemoglobin (1.150 vs. 2.716 MSOT a.u. compared to controls; p=0.004) by MSOT two days after inoculation. These findings were significantly more prominent 7 days after inoculation, with increased mean signal intensity of oxygenated hemoglobin (1.150 vs. 2.716 vs. 3.422 MSOT a.u. for controls vs. 2 days post-ETBF vs. 7 days post-ETBF, p=0.0002) and the development of punctate vascular lesions on the colonic surface. Compared to untreated controls, mice at 2 days and 7 days post ETBF inoculation demonstrated an increased colitis score on colonoscopy (1.5 vs. 2.5 vs. 5.5), which correlated well with MSOT findings of mean oxygenated hemoglobin signal intensity (r=0.82, p=0.013). These findings were also associated with inflammatory changes observed on histologic analysis.

Conclusions: MSOT represents a non-invasive diagnostic modality that effectively identifies colitis in a murine model. With improvements in depth of tissue penetration, MSOT may hold potential as a sensitive, accurate, non-invasive imaging tool in evaluation of both disease status and early detection of malignancy in patients with IBD.

Citation Format: Neal Bhutiani, William Grizzle, Susan Galandiuk, Dennis Otali, Gerald Dryden, Nejat Egilmez, Lacey R. Mcnally. Non-invasive imaging of colitis using multispectral optoacoustic tomography [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1863. doi:10.1158/1538-7445.AM2017-1863

AMPK-dependent and independent effects of AICAR and Compound C on T-cell responses

As a master metabolic sensor, AMP-activated protein kinase (AMPK) is involved in different fundamental cellular processes. Regulation of AMPK activity either by agonists (e.g., AICAR) or by antagonists (e.g., Compound C) has been widely employed to study the physiological functions of AMPK. However, mounting evidence indicates AMPK-independent effects for these chemicals. Herein, using T cells from AMPK conditional knockout mice and their wild type littermates, we demonstrate that AICAR and Compound C can, indeed, activate or inhibit AMPK activity in T cells, respectively. Specifically, AICAR inhibits, but Compound C promotes, Ca2+-induced T cell death in an AMPK-dependent manner. In contrast, our data also demonstrate that AICAR and Compound C inhibit T cell activation and cytokine production in an AMPK-independent manner. Moreover, we find that the AMPK-independent activity of AICAR and Compound C is mediated via the mTOR signaling pathway in activated T cells. Our results not only reveal the critical role of AMPK in regulating T cell survival and function, but also demonstrate AMPK-dependent and independent roles of AICAR/Compound C in regulating T cell responses, thus suggesting a context-dependent effect of these “AMPK regulators”.

Regulatory rebound in Interleukin-12-treated tumors is driven by uncommitted peripheral Treg (TUM9P.1012)

Interleukin-12 (IL-12) promotes a rapid reversal of immune suppression in the tumor microenvironment. However the adjuvant activity of IL-12 is short-lived due to T-regulatory cell (Treg) re-infiltration. Quantitative analysis of Treg kinetics in IL-12-treated tumors and tumor-draining lymph nodes (TDLN) revealed a transient loss followed by a rapid 4-fold expansion of tumor Treg between days 3 and 10. Subset-specific analysis demonstrated that the post-treatment rebound was driven by the CD4+ CD25+ Foxp3+ Neuropilin-1(Nrp-1)low peripheral Treg (pTreg) resulting in a 5-fold increase in the pTreg to CD4+ CD25+ Foxp3+ Nrp-1high thymic Treg (tTreg) ratio by day 10. The expanding pTreg displayed hypermethylation of the CpG islands in Treg-specific demethylated region (TSDR), CTLA-4 exon 2 and GITR exon 5; were phenotypically unstable; and exhibited diminished suppressive function consistent with an uncommitted in vitro-induced Treg (iTreg)-like phenotype. In vitro culture of post-therapy Treg populations under TH1-promoting conditions resulted in the production of IFNg by pTreg but not by tTreg, confirming their transitional state. Blockade of selected molecular mechanisms that are known to promote Treg expansion identified Indoleamine 2,3 dioxygenase (IDO)-positive Dendritic cells as the primary mediator of post-IL-12 pTreg expansion. Clinical implications of these findings are discussed.

Local intravaginal microencapsulated interleukin 12 treatment enhances adaptive immunity to Neisseria gonorrhoeae and induces cross-protection against heterologous strains of gonococci (IRC8P.492)

Uncomplicated genital infection with N. gonorrhoeae does not induce specific protective immunity or immune memory. Our previous studies in a mouse genital tract infection model have demonstrated that N. gonorrhoeae selectively elicits Th17-mediated innate host defenses that it can survive and concomitantly suppresses Th1/Th2-driven adaptive immune responses that would eliminate it. Here we show that intravaginally administered IL-12 encapsulated in sustained-release polymer microspheres led to significantly faster clearance of infection. Enhanced resistance to secondary infection with the same strain of N. gonorrhoeae induced by intravaginal treatment with IL-12 microspheres during primary infection persisted for 6 months. Furthermore, treatment of mice with IL-12 microspheres during gonococcal challenge induced resistance to reinfection with unrelated strains of N. gonorrhoeae. ELISA, flow cytometry and PCR studies demonstrated that IL-12 microsphere treatment in infected mice effectively enhanced Th1 immune responses in the vaginal tract and the draining lymph nodes, without hindering Th17 responses. Although IL-12 microspheres did not change Th2 responses, the treatment significantly increased the production of gonococcus-specific circulating IgG and vaginal IgA and IgG antibodies. These results suggest that local administration of microencapsulated IL-12 may serve as a novel, effective immunomodulatory and therapeutic strategy against gonorrhea.

Diverse Caenorhabditis elegans genes that are upregulated in dauer larvae also show elevated transcript levels in long-lived, aged, or starved adults

Under adverse conditions, the nematode Caenorhabditis elegans undergoes reversible developmental arrest as dauer larvae, an alternative third larval stage adapted for dispersal and long-term survival. Following such arrest, which may exceed three times their usual life-span, worms resume development to form reproductive adults of normal subsequent longevity. Mutations of genes in the dauer-formation (daf) pathway can extend life-span two- to fourfold, even in adults that mature without diapause. To identify transcript-level changes that might contribute to extended survival, we prepared a subtractive cDNA library of messages more abundant in dauer than in non-dauer (L3) larvae. Six genes were confirmed as three- to ninefold upregulated in dauer larvae, after correction for mRNA load: genes encoding poly(A)-binding protein (PABP), heat-shock proteins hsp70 and hsp90, and three novel genes of uncertain function. The novel genes encode a partial homologue of human activating signal cointegrator 1 (ASC-1), a GTP-binding homologue of a ribosomal protein, and an SH3-domain protein. Transcript levels for all except hsp70 increased during aging in two C. elegans strains, whereas the three novel genes (and possibly PABP) were also induced to varying degrees by starvation of adults. All six genes are expressed at higher levels in young adults of long-lived daf mutant strains than in normal-longevity controls, suggesting that increased expression of these genes may play a protective function, thus favoring survival in diverse contexts.