Therapeutic depletion of CCR8+ tumor-infiltrating regulatory T cells elicits antitumor immunity and synergizes with anti-PD-1 therapy.

BACKGROUND: Modulation and depletion strategies of regulatory T cells (Tregs) constitute valid approaches in antitumor immunotherapy but suffer from severe adverse effects due to their lack of selectivity for the tumor-infiltrating (ti-)Treg population, indicating the need for a ti-Treg specific biomarker. METHODS: We employed single-cell RNA-sequencing in a mouse model of non-small cell lung carcinoma (NSCLC) to obtain a comprehensive overview of the tumor-infiltrating T-cell compartment, with a focus on ti-Treg subpopulations. These findings were validated by flow cytometric analysis of both mouse (LLC-OVA, MC38 and B16-OVA) and human (NSCLC and melanoma) tumor samples. We generated two CCR8-specific nanobodies (Nbs) that recognize distinct epitopes on the CCR8 extracellular domain. These Nbs were formulated as tetravalent Nb-Fc fusion proteins for optimal CCR8 binding and blocking, containing either an antibody-dependent cell-mediated cytotoxicity (ADCC)-deficient or an ADCC-prone Fc region. The therapeutic use of these Nb-Fc fusion proteins was evaluated, either as monotherapy or as combination therapy with anti-programmed cell death protein-1 (anti-PD-1), in both the LLC-OVA and MC38 mouse models. RESULTS: We were able to discern two ti-Treg populations, one of which is characterized by the unique expression of Ccr8 in conjunction with Treg activation markers. Ccr8 is also expressed by dysfunctional CD4+ and CD8+ T cells, but the CCR8 protein was only prominent on the highly activated and strongly T-cell suppressive ti-Treg subpopulation of mouse and human tumors, with no major CCR8-positivity found on peripheral Tregs. CCR8 expression resulted from TCR-mediated Treg triggering in an NF-κB-dependent fashion, but was not essential for the recruitment, activation nor suppressive capacity of these cells. While treatment of tumor-bearing mice with a blocking ADCC-deficient Nb-Fc did not influence tumor growth, ADCC-prone Nb-Fc elicited antitumor immunity and reduced tumor growth in synergy with anti-PD-1 therapy. Importantly, ADCC-prone Nb-Fc specifically depleted ti-Tregs in a natural killer (NK) cell-dependent fashion without affecting peripheral Tregs. CONCLUSIONS: Collectively, our findings highlight the efficacy and safety of targeting CCR8 for the depletion of tumor-promoting ti-Tregs in combination with anti-PD-1 therapy

Enhancement of Polymeric Immunoglobulin Receptor Transcytosis by Biparatopic VHH

The polymeric immunoglobulin receptor (pIgR) ensures the transport of dimeric immunoglobulin A (dIgA) and pentameric immunoglobulin M (pIgM) across epithelia to the mucosal layer of for example the intestines and the lungs via transcytosis. Per day the human pIgR mediates the excretion of 2 to 5 grams of dIgA into the mucosa of luminal organs. This system could prove useful for therapies aiming at excretion of compounds into the mucosa. Here we investigated the use of the variable domain of camelid derived heavy chain only antibodies, also known as VHHs or Nanobodies®, targeting the human pIgR, as a transport system across epithelial cells. We show that VHHs directed against the human pIgR are able to bind the receptor with high affinity (∼1 nM) and that they compete with the natural ligand, dIgA. In a transcytosis assay both native and phage-bound VHH were only able to get across polarized MDCK cells that express the human pIgR gene in a basolateral to apical fashion. Indicating that the VHHs are able to translocate across epithelia and to take along large particles of cargo. Furthermore, by making multivalent VHHs we were able to enhance the transport of the compounds both in a MDCK-hpIgR and Caco-2 cell system, probably by inducing receptor clustering. These results show that VHHs can be used as a carrier system to exploit the human pIgR transcytotic system and that multivalent compounds are able to significantly enhance the transport across epithelial monolayers

Involvement of Sp1 in basal and retinoic acid induced transcription of the human tissue-type plasminogen activator gene

AbstractTranscription of the human tissue-type plasminogen activator (t-PA) gene is regulated by a multi-hormonal responsive enhancer at −7 kb. Transient co-transfections of Drosophila SL2 and human HT1080 fibrosarcoma cells with t-PA reporter constructs showed that Sp1 and Sp3 activate the t-PA promoter. Moreover Sp1 (but not Sp3) binding to the promoter is involved in induction by retinoic acid (RA), a response mediated through the enhancer. The role of Sp1 is specific, since mutation of the CRE element in the promoter did not affect response to RA. In contrast, the glucocorticoid induction mediated by the enhancer is independent of these Sp1 and CRE elements

Peroxisome-proliferator-activated receptor gamma induces a clearance mechanism for the amyloid-beta peptide.

We investigated whether peroxisome proliferator-activated receptor gamma (PPARgamma) could be involved in the modulation of the amyloid cascade causing Alzheimer's disease. Inducing expression or activating PPARgamma using synthetic agonists of the thiazolinedione family results in a dramatic decrease in the levels of the amyloid-beta (Abeta) peptide in the conditioned medium of neuronal and non-neuronal cells. PPARgamma does not affect expression or activity of any of the secretases involved in the generation of the Abeta peptide but induces a fast, cell-bound clearing mechanism responsible for the removal of the Abeta peptide from the medium. Although PPARgamma expression is generally low in the CNS, induction of PPARgamma expression during inflammation could be beneficial for inducing Abeta clearance. We confirm that the Abeta clearance mechanism can indeed be induced by PPARgamma activation in primary murine-mixed glia and cortical neuronal cultures. Our results suggest that PPARgamma-controlled mechanisms should be explored further as potential drug targets for Alzheimer's disease treatment.info:eu-repo/semantics/publishe

1,25-Dihydroxyvitamin D3 induction of the tissue-type plasminogen activator gene is mediated through its multihormone-responsive enhancer

AbstractTissue-type plasminogen activator (t-PA) is a positive modulator of the plasminogen-plasmin system, which is involved in bone remodeling. In the present study, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] was found to stimulate t-PA gene expression in ROS17/2.8 osteosarcoma cells. Transient transfection analysis and in vitro DNA binding studies identified two vitamin D-responsive elements (VDRE) in the human t-PA enhancer. The first VDRE (bp −7175 to −7146) comprised an inverted palindrome separated by 9 bp (IP9) overlapping a palindrome separated by 3 bp. The second VDRE (bp −7315 to −7302) is an IP2 element overlapping the previously identified retinoic acid-responsive element. 1,25(OH)2D3 treatment of primary osteoblasts derived from t-PAlacZ transgenic mice containing 9 kb of 5′ sequence of the human t-PA gene increased the number of lacZ-positive cells, fitting with the probability model of enhancer function

Abstract 1732: Investigation of the best therapeutic approach to target CCR8 expressed on tumor regulatory T cells to boost anti-tumor immune responses

Abstract The goal of this study was to investigate the therapeutic potential of targeting regulatory T cells (Treg) through CC motif chemokine receptor 8 (CCR8) and to determine the optimal mode of action for CCR8 targeting molecules to elicit anti-tumor immune response. Infiltration of high levels of Treg cells in tumors is associated with a poor survival prognosis suggesting that the latter cells restrain effector T cell and overall immune activity in the tumor microenvironment. Modulation and inhibition of Treg cells in the tumor is expected to lead to a reinvigorated immune response against the tumor cells. Since Treg cells are also essential for controlling autoimmunity, modulating regulatory T cell activity is preferably restricted to the tumor microenvironment. CCR8 has been identified as a chemokine receptor expressed specifically on tumor-infiltrating, but not on peripheral Treg cells. Surrogate molecules targeting mouse CCR8 having distinct modes of action were generated and were tested in different syngeneic tumor mouse models. In the CT26 and MC38 models, anti-CCR8 monotherapy showed a reduction in tumor growth, prolonged survival and tumor stasis in the majority of the mice. Tumor regression was observed in 20-40% of the mice. Combining anti-CCR8 with anti-PD-1 treatment resulted in both models in complete tumor regression in the majority of the mice. Immunophenotyping analysis showed that anti-CCR8 treatment resulted in strongly decreased Treg cell levels in the tumor. In addition, anti-CCR8 monotherapy and anti-PD1 combination therapy lead to an increase of intratumoral CD8 T cell levels resulting in a favorable CD8/Treg cell ratio. Molecules lacking Fc mediated effector function and only blocking the CCL1-CCR8 signaling showed limited or no efficacy in these tumor models, suggesting that the observed anti-tumor effect is due to ADCC/ADCP - mediated Treg cell depletion and not to blocking of CCR8. Moreover, re-challenge of the complete responders (in both MC38 and CT26) resulted in full tumor rejection in the majority of the mice, indicative of a strong immunological memory. Next to the surrogate molecules, a large set of molecules binding to human CCR8 were identified. Based on human CCR8 binding, CCL1 blocking and in vitro ADCC cell based assay data a final panel of molecules binding to a diverse set of epitopes on human CCR8 have been selected. Final leads are available and are progressing into preclinical development. Our results demonstrate that targeting CCR8 represents a very attractive and promising method to unleash anti-tumor immune responses in patients. Citation Format: Heleen Roose, Elizabeth Allen, Helena Van Damme, Bruno Dombrecht, Rosa Martín-Pérez, Damya Laoui, Jo A. Van Ginderachter, Pascal Merchiers. Investigation of the best therapeutic approach to target CCR8 expressed on tumor regulatory T cells to boost anti-tumor immune responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1732.</jats:p

Pathological Hallmarks, Clinical Parallels, and Value for Drug Testing in Alzheimer's Disease of the APP[V717I] London Transgenic Mouse Model

The APP[V717I] London (APP-Ld) mouse model recapitulates important pathological and clinical hallmarks of Alzheimer's disease (AD) and is therefore a valuable paradigm for evaluating therapeutic candidates. Historically, both the parenchymal and vascular amyloid deposits, and more recently, truncated and pyroglutamate-modified Abeta3(pE)-42 species, are perceived as important hallmarks of AD-pathology. Late stage symptoms are preceded by robust deficits in orientation and memory that correlate in time with Abeta oligomerization and GSK3-mediated phosphorylation of endogenous murine Tau, all markers that have gained considerable interest during the last decade. Clinical parallels with AD patients and the value of the APP-Ld transgenic mouse model for preclinical in vivo testing of candidate drugs are discussed

Therapeutic depletion of CCR8+ tumor-infiltrating regulatory T cells elicits antitumor immunity and synergizes with anti-PD-1 therapy.

BACKGROUND: Modulation and depletion strategies of regulatory T cells (Tregs) constitute valid approaches in antitumor immunotherapy but suffer from severe adverse effects due to their lack of selectivity for the tumor-infiltrating (ti-)Treg population, indicating the need for a ti-Treg specific biomarker. METHODS: We employed single-cell RNA-sequencing in a mouse model of non-small cell lung carcinoma (NSCLC) to obtain a comprehensive overview of the tumor-infiltrating T-cell compartment, with a focus on ti-Treg subpopulations. These findings were validated by flow cytometric analysis of both mouse (LLC-OVA, MC38 and B16-OVA) and human (NSCLC and melanoma) tumor samples. We generated two CCR8-specific nanobodies (Nbs) that recognize distinct epitopes on the CCR8 extracellular domain. These Nbs were formulated as tetravalent Nb-Fc fusion proteins for optimal CCR8 binding and blocking, containing either an antibody-dependent cell-mediated cytotoxicity (ADCC)-deficient or an ADCC-prone Fc region. The therapeutic use of these Nb-Fc fusion proteins was evaluated, either as monotherapy or as combination therapy with anti-programmed cell death protein-1 (anti-PD-1), in both the LLC-OVA and MC38 mouse models. RESULTS: We were able to discern two ti-Treg populations, one of which is characterized by the unique expression of Ccr8 in conjunction with Treg activation markers. Ccr8 is also expressed by dysfunctional CD4+ and CD8+ T cells, but the CCR8 protein was only prominent on the highly activated and strongly T-cell suppressive ti-Treg subpopulation of mouse and human tumors, with no major CCR8-positivity found on peripheral Tregs. CCR8 expression resulted from TCR-mediated Treg triggering in an NF-κB-dependent fashion, but was not essential for the recruitment, activation nor suppressive capacity of these cells. While treatment of tumor-bearing mice with a blocking ADCC-deficient Nb-Fc did not influence tumor growth, ADCC-prone Nb-Fc elicited antitumor immunity and reduced tumor growth in synergy with anti-PD-1 therapy. Importantly, ADCC-prone Nb-Fc specifically depleted ti-Tregs in a natural killer (NK) cell-dependent fashion without affecting peripheral Tregs. CONCLUSIONS: Collectively, our findings highlight the efficacy and safety of targeting CCR8 for the depletion of tumor-promoting ti-Tregs in combination with anti-PD-1 therapy