Cross-reactive CD8+ T cell responses to tumor-associated antigens (TAAs) and homologous microbiota-derived antigens (MoAs).

BACKGROUND: We have recently shown extensive sequence and conformational homology between tumor-associated antigens (TAAs) and antigens derived from microorganisms (MoAs). The present study aimed to assess the breadth of T-cell recognition specific to MoAs and the corresponding TAAs in healthy subjects (HS) and patients with cancer (CP). METHOD: A library of > 100 peptide-MHC (pMHC) combinations was used to generate DNA-barcode labelled multimers. Homologous peptides were selected from the Cancer Antigenic Peptide Database, as well as Bacteroidetes/Firmicutes-derived peptides. They were incubated with CD8 + T cells from the peripheral blood of HLA-A*02:01 healthy individuals (n = 10) and cancer patients (n = 16). T cell recognition was identified using tetramer-staining analysis. Cytotoxicity assay was performed using as target cells TAP-deficient T2 cells loaded with MoA or the paired TuA. RESULTS: A total of 66 unique pMHC recognized by CD8+ T cells across all groups were identified. Of these, 21 epitopes from microbiota were identified as novel immunological targets. Reactivity against selected TAAs was observed for both HS and CP. pMHC tetramer staining confirmed CD8+ T cell populations cross-reacting with CTA SSX2 and paired microbiota epitopes. Moreover, PBMCs activated with the MoA where shown to release IFNγ as well as to exert cytotoxic activity against cells presenting the paired TuA. CONCLUSIONS: Several predicted microbiota-derived MoAs are recognized by T cells in HS and CP. Reactivity against TAAs was observed also in HS, primed by the homologous bacterial antigens. CD8+ T cells cross-reacting with MAGE-A1 and paired microbiota epitopes were identified in three subjects. Therefore, the microbiota can elicit an extensive repertoire of natural memory T cells to TAAs, possibly able to control tumor growth ("natural anti-cancer vaccination"). In addition, non-self MoAs can be included in preventive/therapeutic off-the-shelf cancer vaccines with more potent anti-tumor efficacy than those based on TAAs.

TCR-engaging scaffolds selectively expand antigen-specific T-cells with a favorable phenotype for adoptive cell therapy.

BACKGROUND: Adoptive cell therapy (ACT) has shown promising results for the treatment of cancer and viral infections. Successful ACT relies on ex vivo expansion of large numbers of desired T-cells with strong cytotoxic capacity and in vivo persistence, which constitutes the greatest challenge to current ACT strategies. Here, in this study, we present a novel technology for ex vivo expansion of antigen-specific T-cells; artificial antigen-presenting scaffolds (Ag-scaffolds) consisting of a dextran-polysaccharide backbone, decorated with combinations of peptide-Major Histocompatibility Complex (pMHC), cytokines and co-stimulatory molecules, enabling coordinated stimulation of antigen-specific T-cells. METHODS: The capacity of Ag-scaffolds to expand antigen-specific T-cells was explored in ex vivo cultures with peripheral blood mononuclear cells from healthy donors and patients with metastatic melanoma. The resulting T-cell products were assessed for phenotypic and functional characteristics. RESULTS: We identified an optimal Ag-scaffold for expansion of T-cells for ACT, carrying pMHC and interleukin-2 (IL-2) and IL-21, with which we efficiently expanded both virus-specific and tumor-specific CD8+ T cells from peripheral blood of healthy donors and patients, respectively. The resulting T-cell products were characterized by a high frequency of antigen-specific cells with high self-renewal capacity, low exhaustion, a multifunctional cytokine profile upon antigen-challenge and superior tumor killing capacity. This demonstrates that the coordinated stimuli provided by an optimized stoichiometry of TCR engaging (pMHC) and stimulatory (cytokine) moieties is essential to obtain desired T-cell characteristics. To generate an 'off-the-shelf' multitargeting Ag-scaffold product of relevance to patients with metastatic melanoma, we identified the 30 most frequently recognized shared HLA-A0201-restricted melanoma epitopes in a cohort of 87 patients. By combining these in an Ag-scaffold product, we were able to expand tumor-specific T-cells from 60-70% of patients with melanoma, yielding a multitargeted T-cell product with up to 25% specific and phenotypically and functionally improved T cells. CONCLUSIONS: Taken together, the Ag-scaffold represents a promising new technology for selective expansion of antigen-specific CD8+ T cells directly from blood, yielding a highly specific and functionally enhanced T-cell product for ACT.

Dynamics of Melanoma-Associated Epitope-Specific CD8+ T Cells in the Blood Correlate With Clinical Outcome Under PD-1 Blockade.

Immune checkpoint blockade (ICB) is standard-of-care for patients with metastatic melanoma. It may re-invigorate T cells recognizing tumors, and several tumor antigens have been identified as potential targets. However, little is known about the dynamics of tumor antigen-specific T cells in the circulation, which might provide valuable information on ICB responses in a minimally invasive manner. Here, we investigated individual signatures composed of up to 167 different melanoma-associated epitope (MAE)-specific CD8+ T cells in the blood of stage IV melanoma patients before and during anti-PD-1 treatment, using a peptide-loaded multimer-based high-throughput approach. Additionally, checkpoint receptor expression patterns on T cell subsets and frequencies of myeloid-derived suppressor cells and regulatory T cells were quantified by flow cytometry. Regression analysis using the MAE-specific CD8+ T cell populations was applied to identify those that correlated with overall survival (OS). The abundance of MAE-specific CD8+ T cell populations, as well as their dynamics under therapy, varied between patients. Those with a dominant increase of these T cell populations during PD-1 ICB had a longer OS and progression-free survival than those with decreasing or balanced signatures. Patients with a dominantly increased MAE-specific CD8+ T cell signature also exhibited an increase in TIM-3+ and LAG-3+ T cells. From these results, we created a model predicting improved/reduced OS by combining data on dynamics of the three most informative MAE-specific CD8+ T cell populations. Our results provide insights into the dynamics of circulating MAE-specific CD8+ T cell populations during ICB, and should contribute to a better understanding of biomarkers of response and anti-cancer mechanisms.

Novel Molecular Targets for Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is the third leading cause of death from cancer globally. Indeed, only a few treatments are available, most of which are effective only for the early stages of the disease. Therefore, there is an urgent needing for potential markers for a specifically targeted therapy. Candidate proteins were selected from datasets of The Human Protein Atlas, in order to identify specific tumor-associated proteins overexpressed in HCC samples associated with poor prognosis. Potential epitopes were predicted from such proteins, and homology with peptides derived from viral proteins was assessed. A multiparametric validation was performed, including recognition by PBMCs from HCC-patients and healthy donors, showing a T-cell cross-reactivity with paired epitopes. These results provide novel HCC-specific tumor-associated antigens (TAAs) for immunotherapeutic anti-HCC strategies potentially able to expand pre-existing virus-specific CD8+ T cells with superior anticancer efficacy.

Release of transcriptional repression via ErbB2-induced, SUMO-directed phosphorylation of myeloid zinc finger-1 serine 27 activates lysosome redistribution and invasion.

HER2/ErbB2 activation turns on transcriptional processes that induce local invasion and lead to systemic metastasis. The early transcriptional changes needed for ErbB2-induced invasion are poorly understood. Here, we link ErbB2 activation to invasion via ErbB2-induced, SUMO-directed phosphorylation of a single serine residue, S27, of the transcription factor myeloid zinc finger-1 (MZF1). Utilizing an antibody against MZF1-pS27, we show that the phosphorylation of S27 correlates significantly (p < 0.0001) with high-level expression of ErbB2 in primary invasive breast tumors. Phosphorylation of MZF1-S27 is an early response to ErbB2 activation and results in increased transcriptional activity of MZF1. It is needed for the ErbB2-induced expression of MZF1 target genes CTSB and PRKCA, and invasion of single-cells from ErbB2-expressing breast cancer spheroids. The phosphorylation of MZF1-S27 is preceded by poly-SUMOylation of K23, which can make S27 accessible to efficient phosphorylation by PAK4. Based on our results, we suggest for an activation mechanism where phosphorylation of MZF1-S27 triggers MZF1 dissociation from its transcriptional repressors such as the CCCTC-binding factor (CTCF). Our findings increase understanding of the regulation of invasive signaling in breast cancer by uncovering a detailed biological mechanism of how ErbB2 activation can rapidly lead to its invasion-promoting target gene expression and invasion.

Let-7 microRNA controls invasion-promoting lysosomal changes via the oncogenic transcription factor myeloid zinc finger-1.

Cancer cells utilize lysosomes for invasion and metastasis. Myeloid Zinc Finger1 (MZF1) is an ErbB2-responsive transcription factor that promotes invasion of breast cancer cells via upregulation of lysosomal cathepsins B and L. Here we identify let-7 microRNA, a well-known tumor suppressor in breast cancer, as a direct negative regulator of MZF1. Analysis of primary breast cancer tissues reveals a gradual upregulation of MZF1 from normal breast epithelium to invasive ductal carcinoma and a negative correlation between several let-7 family members and MZF1 mRNA, suggesting that the inverse regulatory relationship between let-7 and MZF1 may play a role in the development of invasive breast cancer. Furthermore, we show that MZF1 regulates lysosome trafficking in ErbB2-positive breast cancer cells. In line with this, MZF1 depletion or let-7 expression inhibits invasion-promoting anterograde trafficking of lysosomes and invasion of ErbB2-expressing MCF7 spheres. The results presented here link MZF1 and let-7 to lysosomal processes in ErbB2-positive breast cancer cells that in non-cancerous cells have primarily been connected to the transcription factor EB. Identifying MZF1 and let-7 as regulators of lysosome distribution in invasive breast cancer cells, uncouples cancer-associated, invasion-promoting lysosomal alterations from normal lysosomal functions and thus opens up new possibilities for the therapeutic targeting of cancer lysosomes.