PHENOTYPIC AND FUNCTIONAL MODULATION OF REGULATORY T CELLS IN MELANOMA PATIENTS

Recent studies indicated that regulatory T cells (Tregs) are implicated in the suppression of the immune response against tumors. Accumulation of Tregs in peripheral blood and in tumor microenvironment has been described for patients with various types of cancer. The balance between T effector cells and Tregs, both at tumor site or at local draining lymph nodes is subverted thus limiting the immune response against cancer and restraining the effect of immunotherapy. As concern melanoma, data till now available confirm the presence of Tregs at tumor site, however no in deep analysis on phenotypic or functional characterization of these cells have been provided. This thesis is aimed at evaluating the role of CD4+ Tregs in the immune response against melanoma either by in vivo or in vitro approaches. Among molecules found in mice as expressed by Tregs, lymphocytes activation gene-3 (LAG-3) has been described to be expressed by activated Tregs and more in general as a molecule involved in the control of T cell expansion and homeostasis. In this thesis I explored the expression of LAG-3 in human CD4+ T cells and found that LAG-3 identifies a discrete subset of CD4+CD25highFoxp3+ T cells. This CD4+CD25highFoxp3+LAG-3+ population is preferentially expanded in lymphocytes of tumor-invaded lymph nodes and in lymphocytes infiltrating visceral and sub cute metastasis of melanoma patients. Ex-vivo analysis showed that CD4+CD25highFoxp3+LAG-3+ T cells are functionally active cells that release the immunosuppressive cytokines interleukin-10 (IL-10) and transforming growth factor beta (TGF-\uf0621). An in vitro suppression assay using CD4+CD25highLAG-3+ T cells sorted from in vitro expanded CD4+CD25high Tregs showed that this subset of cells is endowed with potent suppressor activity that requires cell-to-cell contact. All together, our data show that LAG-3 defines an active CD4+CD25high Tregs subset in melanoma patients whose frequency is expanded at tumor sites. My data showed that Tregs are accumulated in different immunological districts of patients with melanoma and they also stress the notion that in melanoma patients these Tregs are preferentially in an activation status. However, the real impact of these cells on tumor progression has not been totally clarified. To get insights on the relevance of Tregs in the immunological response to tumor, a phase II randomized trial of multipeptide vaccination in stage IIB-C/III melanoma patients has been designed to include the administration of low dose cyclophosphamide (CTX; 300mg/m2) and low dose interleukin-2 (IL-2; 3x106). CTX has been described as limiting the expansion of Tregs, while IL-2 was given with the aim of expanding tumor-specific responses. The modulation that these drugs exert on different T cell compartment, namely Tregs and conventional T cells was evaluated for its impact on patients\u2019 immunological response. Careful ex-vivo immunological monitoring has been performed aimed at assessing the status of vaccine-induced immune response and the levels of Tregs. Importantly, Treg frequency was defined combining physical and functional markers trying to take into account the plasticity of this population. We observed that CTX has a limited efficacy and a transient effect on Tregs modulation; frequency of Tregs identified by multiparametric fluorescence-activated cell sorting (FACS) analysis as CD4+CD25highFoxp3+ dropped in peripheral blood mononuclear cells (PBMCs) collected 4-7 days after CTX administration, with 6 out of 13 patients displaying a reduction ranging from 20 to 65 %. IL-2 showed higher immunomodulatory effects, expanding both circulating conventional activated CD4+ T cells and Tregs; interestingly, a fraction of these Tregs displayed a Th-1 like phenotype, expressing ex-vivo T-bet (Th1 specific T-box transcription factor) and interferon-\uf067\uf020\uf028INF-\uf067\uf029. Importantly, this enhanced frequency of Tregs does not significantly affect patients\u2019 immunization assessed ex-vivo by human leukocyte antigen (HLA)-A*0201/peptide multimer staining and IFN-\uf067 ELISpot assays

TLR3 expression induces apoptosis in human non‐small‐cell lung cancer

The prognostic value of Toll\u2010like receptor 3 (TLR3) is debated in cancer, differing between tumor types, methods, and cell types. We recently showed for the first time that TLR3 expression on early stage non\u2010small\u2010cell lung cancer (NSCLC) results associated with a good prognosis. Here, we provide experimental evidences explaining the molecular reason behind TLR3\u2019s favorable prognostic role. We demonstrated that TLR3 activation in vitro induces apoptosis in lung cancer cell lines and, accordingly, that TLR3 expression is associated with caspase\u20103 activation in adenocarcinoma NSCLC specimens, both evaluated by immunohistochemistry. Moreover, we showed that TLR3 expression on cancer cells contributes to activate the CD103+ lung dendritic cell subset, that is specifically associated with processing of antigens derived from apoptotic cells and their presentation to CD8+ T lymphocytes. These findings point to the relevant role of TLR3 expression on lung cancer cells and support the use of TLR3 agonists in NSCLC patients to re\u2010activate local innate immune response

Cancer acidity: An ultimate frontier of tumor immune escape and a novel target of immunomodulation

The link between cancer metabolism and immunosuppression, inflammation and immune escape has generated major interest in investigating the effects of low pH on tumor immunity. Indeed, microenvironmental acidity may differentially impact on diverse components of tumor immune surveillance, eventually contributing to immune escape and cancer progression. Although the molecular pathways underlying acidity-related immune dysfunctions are just emerging, initial evidence indicates that antitumor effectors such as T and NK cells tend to lose their function and undergo a state of mostly reversible anergy followed by apoptosis, when exposed to low pH environment. At opposite, immunosuppressive components such as myeloid cells and regulatory T cells are engaged by tumor acidity to sustain tumor growth while blocking antitumor immune responses. Local acidity could also profoundly influence bioactivity and distribution of antibodies, thus potentially interfering with the clinical efficacy of therapeutic antibodies including immune checkpoint inhibitors. Hence tumor acidity is a central regulator of cancer immunity that orchestrates both local and systemic immunosuppression and that may offer a broad panel of therapeutic targets. This review outlines the fundamental pathways of acidity-driven immune dysfunctions and sheds light on the potential strategies that could be envisaged to potentiate immune-mediated tumor control in cancer patients

A novel CXCR4 antagonist counteracts paradoxical generation of cisplatin-induced pro-metastatic niches in lung cancer

Platinum-based chemotherapy remains widely used in advanced non-small cell lung cancer (NSCLC) despite experimental evidence of its potential to induce long-term detrimental effects, including the promotion of pro-metastatic microenvironments. In this study, we investigated the interconnected pathways underlying the promotion of cisplatin-induced metastases. In tumor-free mice, cisplatin treatment resulted in an expansion in the bone marrow of CCR2+CXCR4+Ly6Chigh inflammatory monocytes (IMs) and an increase in lung levels of stromal SDF-1, the CXCR4 ligand. In experimental lung metastasis assays, cisplatin-induced IMs promoted the extravasation of tumor cells and the expansion of CD133+CXCR4+ metastasis-initiating cells (MICs). Peptide R, a novel CXCR4 inhibitor designed as an SDF-1 mimetic peptide, prevented cisplatin-induced IM expansion, the recruitment of IMs into the lungs, and the promotion of metastasis. At the primary tumor site, cisplatin treatment reduced tumor size while simultaneously inducing tumor release of SDF-1, MIC expansion, and recruitment of pro-invasive CXCR4+ macrophages. Co-recruitment of MICs and CCR2+CXCR4+ IMs to distant SDF-1-enriched sites also promoted spontaneous metastases that were prevented by CXCR4 blockade. In clinical specimens from NSCLC patients SDF-1 levels were found to be higher in platinum-treated samples and related to a worse clinical outcome. Our findings reveal that activation of the CXCR4/SDF-1 axis specifically mediates the pro-metastatic effects of cisplatin and suggest CXCR4 blockade as a possible novel combination strategy to control metastatic disease

In Situ Prior Proliferation of CD4+ CCR6+ Regulatory T Cells Facilitated by TGF-β Secreting DCs Is Crucial for Their Enrichment and Suppression in Tumor Immunity

BACKGROUND: CD4(+)CD25(+) regulatory T cells (Tregs), a heterogeneous population, were enrichment in tumor mass and played an important role in modulating anti-tumor immunity. Recently, we reported a Treg subset, CCR6(+) Tregs but not CCR6(-)Tregs, were enriched in tumor mass and closely related to poor prognosis of breast cancer patients. However, the underlying mechanism remains elusive. Here, we carefully evaluate the enrichment of CCR6(+)Tregs in tumor mass during progression of breast cancer and explore its possible mechanism. METHODOLOGY/PRINCIPAL FINDINGS: The frequency of CCR6(+)Tregs in tumor infiltrating lymphocytes (TILs ) was analyzed at early stage and at late stage of tumor in a murine breast cancer model by FACS respectively. The expansion of CCR6(+)Tregs and their CCR6(-) counterpart in tumor mass were determined by BrdU incorporation assay. The effect and its possible mechanism of tumor-resident antigen presenting cells (APCs) on the proliferation of CCR6(+)Tregs also were evaluated. The role of local expansion of CCR6(+)Tregs in their enrichment and suppression in vivo also was evaluated in adoptive cell transfer assay. We found that the prior enrichment of CCR6(+)Tregs but not CCR6(-)Tregs in tumor mass during progression of murine breast cancer, which was dependent on the dominant proliferation of CCR6(+) Tregs in situ. Further study demonstrated that tumor-resident DCs triggered the proliferation of CCR6(+)Treg cells in TGF-β dependent manner. Adoptive transfer of CCR6(+)Tregs was found to potently inhibit the function of CD8(+)T cells in vivo, which was dependent on their proliferation and subsequently enrichment in tumor mass. CONCLUSIONS/SIGNIFICANCE: Our finding suggested that CCR6(+) Tregs, a distinct subset of Tregs, exert its predominant suppressive role in tumor immunity through prior in situ expansion, which might ultimately provide helpful thoughts for the designing of Treg-based immunotherapy for tumor in the future

FoxP3+ T regulatory cells in cancer : prognostic biomarkers and therapeutic targets

T Regulatory cells (Tregs) can have both protective and pathological roles. They maintain immune homeostasis and inhibit immune responses in various diseases, including cancer. Proportions of Tregs in the peripheral blood of some cancer patients increase by five-to ten-folds, compared to those in healthy individuals. Tregs contribute to cancer development and progression by suppressing T effector cell functions, thereby compromising tumor killing and promoting tumor growth. Highly immunosuppressive Tregs express upregulated levels of the transcription factor, Forkhead box protein P3 (FoxP3). Elevated levels of FoxP3+ Tregs within the tumor microenvironment (TME) showed a positive correlation with poor prognosis in various cancer patients. Despite the success of immunotherapy, including the use of immune checkpoint inhibitors, a significant proportion of patients show low response rates as a result of primary or acquired resistance against therapy. Some of the mechanisms which underlie the development of therapy resistance are associated with Treg suppressive function. In this review, we describe Treg contribution to cancer development/progression, and the mechanisms of Treg-mediated immunosuppression. We discuss the prognostic significance of FoxP3+ Tregs in different cancers and their potential use as prognostic biomarkers. We also describe potential therapeutic strategies to target Tregs in combination with other types of immunotherapies aiming to overcome tumor resistance and improve clinical outcomes in cancer patients. Overall, understanding the prognostic significance of FoxP3+ Tregs in various cancers and their contribution to therapeutic resistance could help in the development of more effective targeted therapeutic strategies to enhance the clinical outcomes in cancer patients

Beyond Type 1 Regulatory T Cells: Co-expression of LAG3 and CD49b in IL-10-Producing T Cell Lineages

Type 1 regulatory CD4+ T (Tr1) cells express high levels of the immunosuppressive cytokine IL-10 but not the master transcription factor Foxp3, and can suppress inflammation and promote immune tolerance. In order to identify and obtain viable Tr1 cells for research and clinical applications, co-expression of CD49b and LAG3 has been proposed as a unique surface signature for both human and mouse Tr1 cells. However, recent studies have revealed that this pattern of co-expression is dependent on the stimulating conditions and the differentiation stage of the CD4+ T cells. Here, using an IL-10GFP/Foxp3RFP dual reporter transgenic murine model, we demonstrate that co-expression of CD49b and LAG3 is not restricted to the Foxp3− Tr1 cells, but is also observed in Foxp3+ T regulatory (Treg) cells and CD8+ T cells that produce IL-10. Our data indicate that IL-10-producing Tr1 cells, Treg cells and CD8+ T cells are all capable of co-expressing LAG3 and CD49b in vitro following differentiation under IL-10-inducing conditions, and in vivo following pathogenic insult or infection in the pulmonary mucosa. Our findings urge caution in the use of LAG3/CD49b co-expression as sole markers to identify Tr1 cells, since it may mark IL-10-producing T cell lineages more broadly, including the Foxp3− Tr1 cells, Foxp3+ Treg cells, and CD8+ T cells

T‐cell modulation by cyclophosphamide for tumour therapy

The power of T cells for cancer treatment has been demonstrated by the success of co‐inhibitory receptor blockade and adoptive T‐cell immunotherapies. These treatments are highly successful for certain cancers, but are often personalized, expensive and associated with harmful side effects. Other T‐cell‐modulating drugs may provide additional means of improving immune responses to tumours without these disadvantages. Conventional chemotherapeutic drugs are traditionally used to target cancers directly; however, it is clear that some also have significant immune‐modulating effects that can be harnessed to target tumours. Cyclophosphamide is one such drug; used at lower doses than in mainstream chemotherapy, it can perturb immune homeostasis, tipping the balance towards generation of anti‐tumour T‐cell responses and control of cancer growth. This review discusses its growing reputation as an immune‐modulator whose multiple effects synergize with the microbiota to tip the balance towards tumour immunity offering widespread benefits as a safe, and relatively inexpensive component of cancer immunotherapy

Validity of Anti-PSMA ScFvD2B as a Theranostic Tool: A Narrative-Focused Review

Prostate cancer (PCa) is the second leading cause of cancer among men, and its diagnosis and adequate staging are fundamental. Among the biomarkers identified in recent years for PCa management, prostate-specific-membrane-antigen (PSMA), physiologically expressed at a low level on healthy prostate and in other normal tissues and highly overexpressed in PCa, represents a reliable marker ideal for imaging and therapy. The development of anti-PSMA antibodies, such as D2B, demonstrated slow clearance of intact antibodies compared with fragments resulting in low tumor-to-blood ratios; however, the modular structural and functional nature of antibodies allowed the generation of smaller fragments, such as scFvs. In this review of the anti-PSMA antibody fragment scFvD2B, we combined further characterization of its biomolecular and tissue cross-reactivity characteristics with a comprehensive summary of what has already been performed in preclinical models to evaluate imaging and therapeutic activities. A molecular dynamics study was performed, and ScFvD2B occupied a limited conformational space, characterized by low-energy conformational basins, confirming the high stability of the protein structure. In the cross-reactivity study, the weak/absent immunoreactivity in non-tumor tissues was comparable to the PSMA expression reported in the literature. Biodistribution studies and therapeutic treatments were conducted in different animal models obtained by subcutaneous or locoregional injection of PSMA-positive-versus-negative xenografts. The maximum tumor uptake was observed for (123)I(SPECT), (124)I(PET), and optical imaging, which avoids kidney accumulation (compared with radiometals) and leads to an optimal tumor-to-kidney and tumor-to-background ratios. Regarding its possible use in therapy, experimental data suggested a strong and specific antitumor activity, in vitro and in vivo, obtained using CAR-T or NK-92/CAR cells expressing scFvD2B. Based on presented/reviewed data, we consider that scFvD2B, due to its versatility and robustness, seems to: (i) overcome some problems observed in other studied scFvs, very often relatively unstable and prone to form aggregates; (ii) have sufficient tumor-to-background ratios for targeting and imaging PSMA-expressing cancer; (iii) significantly redirect immune killing cells to PSMA-positive tumors when inserted in second-generation CAR-T or NK-92/CAR cells. These data suggest that our product can be considered the right reagent to fill the gap that still exists in PCa diagnosis and treatment