Suppression Of Antitumor Responses Research Articles

Clinicopathological and prognostic value of TIL and PD L1 in triple negative breast carcinomas

Triple negative breast cancer (TNBC), a highly aggressive subtype of breast cancer, accounts for 15 % of all diagnosed breast cancers. This group, which has the worst clinical outcome, high recurrence rate and poor prognosis, does not benefit from specific treatment. Therefore, there is a need to develop more effective biomarker and therapeutic strategies especially for this group. A positive level of immunity has been found to be associated with patient survival in various organ cancers. More specifically, tumor infiltrating lymphocytes (TIL) have been documented to have strong prognostic value. The programmed cell death 1 (PD 1) protein on the surface of T lymphocytes is activated by the Programmed cell death ligand 1 (PD-L1) protein on the cancer cell surface. PD- L1 is thought to form a pathway that results in suppression of antitumor responses when activated. Patients with breast cancer (BC) who underwent resection without neoadjuvant chemotherapy between 2010 and 2020 were included in this study. Of the 302 BCs examined, 21 constitute the group with TNBC. In our study, the mean age of the Triple positive breast cancer (TPBC) and TNBC groups was similar (55.67 ± 12.61 vs. 53.23 ± 8.21, p = 0.384). There was no significant correlation between TPBC and TNBC and tumor size, lymph node, histological grade, and PD-L1 positivity in the center of the tumor (all p-value >.05). It was observed that tumor stage was higher in patients with TNBC than in patients with TPBC (19 % vs. 1.1 %, p = .002). The Ki 67 proliferation index was found to be higher in patients with TNBC than in patients with TPBC (90.5 % vs. 41.8 %, p .001). Although not statistically significant, clinically, CD 3 and CD 8 immune scores with high tumor margin were higher in patients with TNBC than in patients with TPBC (90.4 % vs, 9.6 % and 85.7 % vs. 14.3 %, respectively). Positive expression of PD-L1 at the tumor margin was significantly higher in patients with TNBC than patients with TPBC (20.3 % vs, 52.4 %, p = .002). By Kaplan-Meier analysis, the survival distribution of CD 3 and CD 8 immunoscore, tumor central and margin PD-L1 values were compared. Mean follow-up was 136.18 months (range, 1 – 144 months); and the 10-year Overall Survival (OS) estimate for the population was 90.9 % (95 % CI, 85.5 – 96.7). In this study, this difference was not statistically significant according to the log-rank test. In this study, we aimed to evaluate the relationship between CD 3, CD 8 T lymphocyte immune score and PD-L1 expression at the tumor center and margin in TNBC, the prognostic value and clinicopathological significance of this relationship.

A Multimodal Single Cell Atlas of Human Tonsils Reveals New Insights into T and B Cell Differentiation

Palatine tonsils are secondary lymphoid organs under constant exposure to antigens via the upper respiratory tract which makes them a compelling organ for adaptive immunity development. They represent an important niche for lymphocyte maturation, where they differentiate into a wide variety of functional states, tailoring immune responses to different insults. However, although some efforts have been made to characterise the lymphocyte maturation process in human tonsils at single cell resolution, these studies lacked cell numbers and multimodal, i.e multiomics, information to comprehensively capture the cellular heterogeneity of the process. Here we generated a comprehensive human tonsil atlas of >357,000 cells profiled across five different data modalities, such as transcriptome, epigenome, proteome, adaptive immune repertoire and spatial location. We identified 121 cell subtypes and states across lineages and characterised the maturation process of both B and T lymphocytes. The high number of profiled cells allowed the detection of rare cell subtypes, such as precursor B and T cells, the latter representing <0.01% of detected cells, supporting an ongoing maturation of lymphoid cells outside the bone marrow and thymus, respectively. Beyond these rare precursor lymphocytes, the tonsil is the niche for multiple steps of mature T and B cell differentiation. With regard to mature T cells, we described 37 different T cell (TC) subpopulations being CD4 TC the more representative population with 58,783 cells, which illustrated the maturation process of this lineage. We identified an early bifurcation following antigen recognition by naïve CD4 TC, resulting in two distinct precursor populations of T follicular helper (fh) and non-Tfh cells. Tfh precursor cells continued their differentiation trajectory towards terminally differentiated populations, with functions in the production of mature B cells (BC) and in the enhancement of antibody secretion. On the other branch of the CD4 TC differentiation trajectory, our data revealed three transcriptional Treg subtypes, with functions in the suppression of antitumor responses, COVID-19 and the control of BC antibody production, respectively. The multimodal study design further enabled the interrogation of regulatory circuits driving TC specialization, describing a potential BCL6 superenhancer specifically active in follicular TC. Intriguingly, the same region has been previously linked to BCL6 gene activation in Germinal Center (GC) BC, indicating its function as follicle-specific rather than cell type-specific cis-regulatory element. Mature B cells corresponded to the greatest population of the dataset, with >70% cells assigned to the BC lineage allowing the fine-grained description of the BC maturation process. We identified 8 distinct naïve BC (NBC) subpopulations and comprehensively characterized the activation pathway upon first antigen recognition, further expanding previous findings focused on MYC. Additionally, by the combination of gene expression and chromatin accessibility profiles we disentangled the transcription factor (TF) hierarchy associated with the Light zone (LZ) to Dark Zone (DZ) reentry. We identified the activity NF-kB family genes as one of the first determinants of the TF hierarchy that drives this specialization, which seems to be shared in LZ cells reentering the DZ as well as activated NBCs that enter the DZ for the first time. However, this regulation was not observed in LZ GCBCs that further differentiate into plasma cells (PCs). This final maturation step towards an antibody secreting phenotype was also characterized, identifying the first stages of PC precursor cells derived from either memory or LZ-GCBC and their transcriptional dynamics was also spatially mapped in the tonsillar tissue. Charting the regulatory landscape in PCs we validated the presence of described PC TFs, but we also discovered SIX5 as a novel potential TF associated with the maturation, but not the commitment, of PCs. Moreover, we identified a higher activity of the regulatory network of SIX5 in multiple myeloma. This study presents a multimodal single cell view of the TC and BC maturation process taking place in the tonsil. We not only present our analysis as a resource but we discover a yet unappreciated cellular heterogeneity as well as novel gene regulatory mechanisms driving naive towards highly specialized lymphoid cells.

TUMOR MICROENVIRONMENT IN ADENOID CYSTIC CARCINOMAS OF SALIVARY GLANDS: A COMPREHENSIVE REVIEW

Objectives Adenoid cystic carcinoma (AdCC) is the second most common salivary gland tumor, accounting for approximately 10% of cases. The aim was to review the tumor microenvironment (TME) components of AdCC and how it regulates tumor progression and the use of candidate targets for AdCC therapy. Study Design A language database search was performed retrieving studies that evaluated the TME of AdCC by different methodologies. Results The findings support the fact that the tumor microenvironment of AdCC, as in other cancers, is composed of a heterogeneous network of interactions involving immune cells (T and B lymphocytes and NK) and their immune checkpoints (especially PD1, PD-L1, and CTLA-4), extracellular matrix production and its inhibitors (MMP-2, MMP-9 e TIMP-1), production of cytokines, chemokines, and growth factors (IL-6, IL-8 CCX4, and FGF-2) and cancer-associated fibroblasts. Taken together, they may promote cell growth and development by inhibition of antitumor responses, induction of angiogenesis, and metastasis. Conclusions TME of AdCC shows complex interactions that leads to a protumoral microenvironment and a poor prognosis. Also, immune cells are potential targets for immune therapy in these tumors. Adenoid cystic carcinoma (AdCC) is the second most common salivary gland tumor, accounting for approximately 10% of cases. The aim was to review the tumor microenvironment (TME) components of AdCC and how it regulates tumor progression and the use of candidate targets for AdCC therapy. A language database search was performed retrieving studies that evaluated the TME of AdCC by different methodologies. The findings support the fact that the tumor microenvironment of AdCC, as in other cancers, is composed of a heterogeneous network of interactions involving immune cells (T and B lymphocytes and NK) and their immune checkpoints (especially PD1, PD-L1, and CTLA-4), extracellular matrix production and its inhibitors (MMP-2, MMP-9 e TIMP-1), production of cytokines, chemokines, and growth factors (IL-6, IL-8 CCX4, and FGF-2) and cancer-associated fibroblasts. Taken together, they may promote cell growth and development by inhibition of antitumor responses, induction of angiogenesis, and metastasis. TME of AdCC shows complex interactions that leads to a protumoral microenvironment and a poor prognosis. Also, immune cells are potential targets for immune therapy in these tumors.

129P Regulatory dendritic cells correlate with an altered T cell distribution and regulatory T cell phenotype in metastatic lymph nodes of NSCLC patients

Dendritic cells (DCs) are considered to be the most important professional population of antigen-presenting cells and play a crucial role in the activation of the immune system. However, the proper function of DCs is altered by the tumor microenvironment (TME). Despite the progress in anticancer immunotherapy, there are still many unresolved issues. Among them, the immunomodulatory properties of DCs in lung cancer are of interest. The aim of the study was to analyze the PD-1+ PD-L1+ CD80- DCs subset, described as regulatory dendritic cells (DCregs), and to investigate correlations between the presence of DCregs and changes in T cell frequencies and immunomodulatory molecules in metastatic and non-metastatic lymph nodes (LNs) aspirates of NSCLC patients. LNs aspirates were obtained during the diagnostic EBUS TBNA procedure of 30 NSCLC patients. DCregs and T cell characteristics were determined by multiparameter flow cytometry. We noticed a higher percentage of DCregs in the metastatic than in the non-metastatic LNs (22.5% vs. 3.1%). DCs cells show increased expression of PD-1 and PD-L1. Additionally, metastatic LNs contained a lower percentage of CD4 T cells, whereas the percentage of CD8 T cells and Tregs was increased as compared to non-metastatic LNs. Surprisingly, the percentage of DCregs positively correlated with the percentage of PD-1+ T cells, Tregs and CD45RO+ Tregs. Our results confirm the utility of flow cytometric analysis of EBUS/TBNA samples to assess the interaction between immune cells in TME. DCregs strongly associates with an altered T cell distribution and immunosuppressive phenotype in metastatic LNs of NSCLC patients. It can be assumed that DCregs are involved in the suppression of anti-tumor response, which could be of importance for the response upon immunotherapy.

Immunosuppressive properties of human PD-1 + , PDL-1 + and CD80 + dendritic cells from lymph nodes aspirates of lung cancer patients.

Dendritic cells (DCs) play a pivotal role in the homeostasis of the immune system. The tumor microenvironment impairs the proper function of DCs. The immunomodulatory properties of DCs in lung cancer are of interest. In the present study, we analysed DCs subsets and immune cells with the expression of immunomodulatory molecules: PD-1 and PD-L1 and co-stimulatory molecule CD80 in metastatic, non-metastatic lymph nodes (LNs) and peripheral blood (PB). LNs aspirates were obtained during the EBUS/TBNA procedure of 29 patients with primary lung cancer. The cells were analyzed by flow cytometry. We reported a higher percentage of DCs in the metastatic than in the non-metastatic LNs and the PB (0.709% vs. 0.166% vs. 0.043%, p < 0.0001). The proportions of PD-1 + , PD-L1 + and CD80 + DCs were higher in the metastatic LNs than in the non-metastatic ones. A higher proportion of regulatory DCs (DCregs) was found in the metastatic ones than in the non-metastatic LNs (22.5% vs. 3.1%, p = 0.0189). We report that DCs cells show increased expression of PD-1, PD-L1 and CD80 molecules that can interact with T lymphocytes. It can be assumed that mature DCs infiltrating metastatic LNs can develop into DCregs, which are involved in the suppression of anti-tumor response.

Toll-like receptor-4 deficiency inhibits ultraviolet radiation-induced tumor development by modulation of immune and inflammatory responses.

Ultraviolet (UV) B irradiation of the skin induces acute inflammation, as characterized by erythema, edema, and immunosuppression, and is subsequently linked to the progression of skin cancer. Toll-like receptor 4 (TLR4), a component of innate immunity, has been shown to play an important role in cancer. To elucidate the role of TLR4 in UVB-induced tumor development, TLR4-proficient (C3H/HeN) and TLR4-deficient (C3H/HeJ) mice were exposed to multiple doses of UVB radiation (200 mJ/cm2 ) for 40 weeks. Photocarcinogenesis was retarded in terms of tumor incidence, and tumor latency, in mice deficient in TLR4 compared with TLR4-proficient mice, whereas significantly greater numbers of tumors occurred in TLR4-proficient mice. There was significant upregulation of inflammatory markers like COX-2, PGE2 , S100A8, and S100A9 in the skin of TLR4-proficient mice than the skin of TLR4-deficient mice. Furthermore, we found that TLR4-proficient mice had a significantly higher number of Gr1+CD11b+ myeloid cells CD4+CD25+ regulatory T-cells than TLR4-deficient mice. Furthermore, the levels of interferon (IFN)-γ cytokine was increased and the levels of interleukin (IL)-4, IL-10, and IL-17 cytokines were decreased in serum, skin, and tumor lysates of TLR4-deficient mice in comparison with samples from TLR4-proficient mice. Together, our data indicate that TLR4-mediated inflammation may cause suppression of antitumor responses and trigger the development of UVB-induced skin cancers. Thus, strategies to inhibit TLR4-mediated immune suppression may allow us to develop preventive and therapeutic approaches for the management of UVB-induced cutaneous tumors.

Abstract 3333: EMT-6 tumor conditioned Breg cells inhibit NK cell proliferation and cytotoxic activity

Abstract Purpose: Breg (B regulatory) cells have been implicated in suppression of anti-tumor response in murine and human solid tumors. Prior studies in our laboratory demonstrated that murine EMT-6 breast carcinoma is rejected in B cell deficient mice (BCDM), but not in wild type (WT) mice, due to an enhanced immune response. Tumor infiltrating B cells (TIL-B), and normal splenic B cells co-cultured with EMT-6 (EMT6-B), express LAP/TGF-β, PD-L1, and suppress CD8+ and NK cell proliferation in vitro. Increased CD8+ and NK cell infiltration into the tumor bed is seen in BCDM. BCDM tumor rejection is abrogated by NK depletion. We studied EMT6-B effects on NK cell phenotype, proliferation and cytokine expression in vitro and in vivo. Experimental design: Normal splenic B cells were co-cultured with mitomycin C treated EMT-6, and Breg phenotype, and effects on NK cell phenotype and proliferation and cytokine function were studied in vitro and in vivo. Results: EMT6-B but not WT splenic B cells inhibited CFSE labeled CD49b+ NK cell proliferation in response to IL-15 in dose dependent fashion. EMT-6-B suppressed expression of CD226 and NKG2D activating receptors on NK cells, and increased expression of PD-1 and PD-L1 respectively. EMT6-B suppressed the induction of IFNγ+/CD49b+ NK cells following PMA/ION stimulation as assayed by intracellular flow cytometry (10%±1.2 to 2%±0.5) and also suppressed IL-2 induced induction of IFNγ+/CD49b+ NK cells (70%±5 to 20%±7.8). EMT-6 and CT26 colon carcinoma conditioned B cells, but not C166 endothelial cell conditioned B cells suppressed NK degranulation (IFNγ+/CD107a+ NK cells). EMT6-B inhibited YAC-1 cell induced NK cell degranulation, and killing of YAC-1 targets, more effectively than naïve B cells (40%±6.2 to 18%±5.1) (P=0.05). NK suppression was inhibited by anti-PD-L1, and anti-TGF-β antibody. EMT6-B expressed increased FasL compared to splenic B cells, and induced NK apoptosis as measured by 7AAD/Annexin-V staining. Blocking antibody to FasL decreased NK apoptosis, and restored NK cell proliferation. Infiltrating NK cells in the EMT6 tumor bed demonstrated increased PD-1 compared to splenic and TDLN NK cells, and higher levels of IFN-γ, CD107a, and Granzyme B in BCDM vs. WT mice. EMT6 expressed high levels of CD155 NK inhibitory ligand compared to C166 endothelial cells. The EMT-6 tumor bed contained higher levels of CD19+CD155+ B cells (22% / tumor bed vs 6% / TDLN, vs 9%/ spleen). BCDM expressed higher levels of CD226+/Ki67+ NK cells in spleen compared to WT splenic NK cells. Antibodies to Fas-L, TGF-beta, and PD-L1 partially restored anti-tumor response in WT mice and decreased tumor growth. Conclusions: EMT-6 TIL-B or normal B cells conditioned by EMT-6 coculture acquire an NK suppressive phenotype which inhibits NK cell activation, proliferation, degranulation and cytotoxic function. Targeting of Breg-NK interactions may improve anti-tumor immune response. Citation Format: Yu Zhang, Muhammad Husnain, Zhifen Luo, Mahmood Al Bayati, Joseph D. Rosenblatt. EMT-6 tumor conditioned Breg cells inhibit NK cell proliferation and cytotoxic activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3333.

CDK1 in Breast Cancer: Implications for Theranostic Potential.

Breast cancer has been identified as one of the main cancer-related deaths among women during some last decades. Recent advances in the introduction of novel potent anti-cancer therapeutics in association with early detection methods led to a decrease in the mortality rate of breast cancer. However, the scenario of breast cancer is yet going on and further improvements in the current anti-cancer therapeutic approaches are needed. Several factors are present in the tumor microenvironment which help to cancer progression and suppression of anti-tumor responses. Targeting these cancer-promoting factors in the tumor microenvironment has been suggested as a potent immunotherapeutic approach for cancer therapy. Among the various tumorsupporting factors, Cyclin-Dependent Kinases (CDKs) are proposed as a novel promising target for cancer therapy. These factors in association with cyclins play a key role in cell cycle progression. Dysregulation of CDKs which leads to increased cell proliferation has been identified in various cancers, such as breast cancer. Accordingly, the development and use of CDK-inhibitors have been associated with encouraging results in the treatment of breast cancer. However, it is unknown that the inhibition of which CDK is the most effective strategy for breast cancer therapy. Since the selective blockage of CDK1 alone or in combination with other therapeutics has been associated with potent anti-cancer outcomes, it is suggested that CDK1 may be considered as the best CDK target for breast cancer therapy. In this review, we will discuss the role of CDK1 in breast cancer progression and treatment.

The Core Fucose on an IgG Antibody is an Endogenous Ligand of Dectin-1.

The core fucose, a major modification of N-glycans, is implicated in immune regulation, such as the attenuation of the antibody-dependent cell-mediated cytotoxicity of antibody drugs and the inhibition of anti-tumor responses via the promotion of PD-1 expression on T cells. Although the core fucose regulates many biological processes, no core fucose recognition molecule has been identified in mammals. Herein, we report that Dectin-1, a known anti-β-glucan lectin, recognizes the core fucose on IgG antibodies. A combination of biophysical experiments further suggested that Dectin-1 recognizes aromatic amino acids adjacent to the N-terminal asparagine at the glycosylation site as well as the core fucose. Thus, Dectin-1 appears to be the first lectin-like molecule involved in the heterovalent and specific recognition of characteristic N-glycans on antibodies.

A Sampling of Highlights from the Literature

Tumor cells select for weak MHCII binding (by Wykis via Wikimedia Commons)Antitumor responses to neoantigens has largely focused on CD8+ T cells. However, CD4+ T-cell responses also contribute, and how this impacts the tumor mutational landscape has not been well documented. Marty and colleagues show that mutations with weak MHCII binding are strongly selected during tumor progression. Using TCGA datasets representing more than 5,000 tumor samples, a score linking MHCII genotype to presentation of specific mutations was generated and shown to reflect the mutated epitopes that are presented to immune cells. The analysis reveals not only that peptides binding poorly to MHCII are selected, but also that the ability to bind to MHCII has more influence on the selective pressure put on tumors than MHCI binding. These results highlight how CD4+ T cells may be playing a key role in shaping antitumor immunity.Marty R, …, Carter H. Cell 2018 Sep 20. doi: 10.1016/j.cell.2018.08.048.ALCAM-specific homing allows T cells to better infiltrate (by RRZEicons via Wikimedia Commons)T-cell infiltration into brain tumors remains a challenge. Samaha and colleagues demonstrate that tumor endothelium, as a mechanism of immune evasion, downregulates specific adhesion molecules commonly upregulated by inflammation and needed by immune cells for extravasation. However, the endothelium also upregulates the adhesion molecule, ALCAM, and this was used to develop a high-avidity ALCAM-specific homing system that allows circulating T cells to better adhere to cancer tissues, resulting in improved cytotoxic T-cell infiltration and potent antitumor responses.Samaha H, …, Ahmed N. Nature 2018 Sep 5;561:331–7.Autophagy in macrophages (green indicates LC3; by Kam23lesh via Wikimedia Commons)The role of autophagy proteins in tumors and the tumor microenvironment have not yet been fully elucidated. Cunha and colleagues show myeloid cell LC3-associated phagocytosis (LAP), which functions in engulfment of dying cells, contributes to immune suppression in the tumor microenvironment. Targeting LAP, which recruits components of the autophagy machinery, specifically in myeloid cells inhibits tumor progression. Tumor-associated macrophages deficient for LAP lose suppressive functions and gain a pro-inflammatory M1 phenotype, promoting T-cell antitumor activity. These data highlight that autophagy proteins can play a role in the suppression of antitumor responses in the tumor microenvironment.Cunha LD,…, Green DR. Cell 2018 Sep 20. doi: 10.1016/j.cell.2018.08.061.Disseminated cancer cells can enter into dormancy or proliferate causing recurrence (by AliMicJones via Wikimedia).Recurrence of many cancers occurs from activation of dormant tumor cells. The mechanisms behind awakening disseminated cancer from dormancy to cause metastasis are not fully known. Albrengues and colleagues show that chronic inflammatory conditions produce neutrophil extracellular traps (NETs) that result in remodeling laminin and integrin signaling that awakens dormant single disseminated cancer cells and metastases in both breast and prostate cancer models. By inhibiting NET formation, or by degrading the DNA scaffold in NETs, dormant cancer cells do not reactivate and metastasis is prevented. This highlights how targeting NETs could aid in the prevention of cancer recurrence in patients.Albrengues J, …, Egeblad M. Science 2018 Sep 28;361:eaao4227.Triple negative breast carcinoma (by Sarahkayb via Wikimedia Commons)Interactions occurring in the tumor microenvironment are complex. Using a multiplexed ion beam imaging system that detects 36 proteins with roles in cell phenotype, function, and regulation, Keren and colleagues analyzed the composition of the tumor microenvironment (TME) in triple-negative breast cancer samples. Coupling the imaging to machine learning allowed determination of the cellular composition, cell localization and spatial relationships to other cell types, and functionality across 41 patients. Immune composition could be classified as compartmentalized or mixed, with compartmentalization at the tumor border having a better prognoses. This analysis not only revealed a structured TME but also allows for characterizing the complex and dynamic interactions taking place in the TME, providing a deeper understanding of how tumor composition can affect prognosis.Keren L, …, Angelo M. Cell 2018 Sep 6;174:1373–87.e19.Gene expression affects what protein is expressed, as well as its function (by OldakQuill via Wikimedia Commons)CD19-negative acute lymphoblastic leukemia (ALL) relapse can occur with CAR T-cell therapy. Orlando and colleagues demonstrate that CAR-resistant tumor cells usually possess CD19 mutations that lead to a truncated protein leading to CD19 loss on the surface of ALL cells, rather than epitope loss as previously reported. This finding suggests concurrently targeting additional molecules such as CD22 should improve CD19 CAR T cell treatment.Orlando EJ, …, Winckler W. Nat Med 2018 Oct 1. DOI: 10.1038/s41591-018-0146-z.

STAT3-enhancing germline mutations contribute to tumor-extrinsic immune evasion.

Immune evasion and the suppression of antitumor responses during cancer progression are considered hallmarks of cancer and are typically attributed to tumor-derived factors. Although the molecular basis for the crosstalk between tumor and immune cells is an area of active investigation, whether host-specific germline variants can dictate immunosuppressive mechanisms has remained a challenge to address. A commonly occurring germline mutation (c.1162G>A/rs351855 G/A) in the FGFR4 (CD334) gene enhances signal transducer and activator of transcription 3 (STAT3) signaling and is associated with poor prognosis and accelerated progression of multiple cancer types. Here, using rs351855 SNP-knockin transgenic mice and Fgfr4-knockout mice, we reveal the genotype-specific gain of immunological function of suppressing the CD8/CD4+FOXP3+CD25+ regulatory T cell ratio in vivo. Furthermore, using knockin transgenic mouse models for lung and breast cancers, we establish the host-specific, tumor-extrinsic functions of STAT3-enhancing germline variants in impeding the tumor infiltration of CD8 T cells. Thus, STAT3-enhancing germline receptor variants contribute to immune evasion through their pleiotropic functions in immune cells.

Influence of lymphocytes T and myeloid-derived suppressor cells on inhibition of antitumor response

For many years research on tumour development focused exclusively on the functions of cancer cells. Less attention was paid to tumour-associated cells, which form the tumour microenvironment. Nowadays we know that inflammatory infiltration cells associated with tumour proliferation may have a pro-tumour or an anti-tumour effect. Current studies are focused on interaction (cross-talk) between cells in the tumour microenvironment. Myeloid suppressor cells (MDSCs) and lymphocytes T are special groups of cells associated with tumour. Interaction between cancer cells, MDSCs and lymphocytes T leads to the development of an immunosuppression network that prevents effective combat against cancer cells and creates conditions favourable for tumour progression, migration and metastasis. The understanding of the crosstalk between cancer cells and immune cells has become the main task of scientists and oncologists.

The Research of Treg Cells: Progress and Challenge

T regulatory cells (Tregs) play an important role in the induction and maintenance of immunological tolerance to self and alloantigens. Recent findings in experimental transplant models have demonstrated that Treg could control and delay allograft rejection. Induction of immune tolerance decreases the risk of acute and chronic graft rejection after solid organ transplantation and can improve transplanted organ survival. Tregs are being tested in trials as a potential therapy in cell and solid organ transplantation. However, as we know, regulatory T cells (Tregs) are crucial for peripheral tolerance and are intimately involved in cancer. The influence of Tregs on cancer progression has been demonstrated in a large number of preclinical models and confirmed in several types of malignancies. Neoplastic processes trigger an increase of Treg numbers in draining lymph nodes, spleen, blood, and tumors, leading to the suppression of anti-tumor responses. In this review, we summarize some of the critical aspects of the immunoregulatory function of Treg cells in cancer and transplantation and discuss their potential research progress and challenge.

IL-17A produced by γδ T cells promotes tumor growth in hepatocellular carcinoma.

Interleukin (IL)-17A is expressed in the tumor microenvironment where it appears to contribute to tumor development, but its precise role in tumor immunity remains controversial. Here, we report mouse genetic evidence that IL-17A is critical for tumor growth. IL-17A-deficient mice exhibited reduced tumor growth, whereas systemic administration of recombinant mouse IL-17A promoted the growth of hepatocellular carcinoma. The tumor-promoting effect of IL-17A was mediated through suppression of antitumor responses, especially CD8(+) T-cell responses. Furthermore, we found that IL-17A was produced mainly by Vγ4 γδ T cells, insofar as depleting Vγ4 γδ T cells reduced tumor growth, whereas adoptive transfer of Vγ4 γδ T cells promoted tumor growth. Mechanistic investigations showed that IL-17A induced CXCL5 production by tumor cells to enhance the infiltration of myeloid-derived suppressor cells (MDSC) to tumor sites in a CXCL5/CXCR2-dependent manner. IL-17A also promoted the suppressive activity of MDSC to reinforce suppression of tumoral immunity. Moreover, we found that MDSC could induce IL-17A-producing γδ T cells via production of IL-1β and IL-23. Conversely, IL-17A could also enhance production of IL-1β and IL-23 in MDSC as a positive feedback. Together, our results revealed a novel mechanism involving cross-talk among γδ T cells, MDSCs, and tumor cells through IL-17A production. These findings offer new insights into how IL-17A influences tumor immunity, with potential implications for the development of tumor immunotherapy.

Immune responses regulation following antitumor dendritic cell-based prophylactic, concurrent, and therapeutic vaccination

There is ample evidence in favor of various immunosuppressive mechanisms that weaken antitumor immune responses and affect currently used immunotherapies. Induction of regulatory T cells (Treg) and secretion of indoleamine 2,3-dioxygenase (IDO) by tumor tissue are considered as two main mechanisms of tumor immune escape. However, little is known about the contribution of these mechanisms on the modulation of dendritic cell vaccine-mediated antitumor response. To address this concern, we assessed Treg's infiltration and the expression of Foxp3 and IDO genes in tumor microenvironment following dendritic cell-based antitumor immunotherapy of mice in different protocols of prophylactic, concurrent, and therapeutic vaccination. According to cytotoxicity assay, the vaccinated mice exposed efficient induction of splenic CTLs in all groups. However, only the mice immunized in prophylactic regimen significantly retarded the growth of tumor cells. Interestingly, the Treg content of tumor samples and transcriptional level of both Foxp3 and IDO genes were reduced in this group, while animals that received the vaccine in concurrent and therapeutic protocols showed increase in tumor-infiltrating Tregs and mRNA levels of Foxp3 and IDO. Accordingly, higher expression of these genes resulted in more inhibition of antitumor response. Our findings indicate that tumor progression may enhance the immunoregulatory response and hence emphasize to the effectiveness of vaccination in early stages of tumor growth for avoiding induction of such regulatory responses.

Abstract C107: The antitumor activity of SCV-07 is attributable, in part, to an inhibitory effect on STAT3 driven responses

Abstract Introduction: In recent years, agents that boost the immune system to break through tumor-induced immunosuppression have gained importance. The dipeptide, SCV-07 (gamma-D-glutamyl-tryptophan) has been shown to be efficacious in reducing progression of renal and lung carcinoma as well as melanoma in mouse models. SCV-07 also induces the elaboration of Th1 cytokines. Because the dipeptide has an effect on a diverse range of tumors, it is possible that SCV-07 has a global, antigen-independent effect on the immune system. Because STAT3 is known to be upregulated in tumor microenvironments, and the effect of STAT3 driven gene expression is global immune suppression of anti-tumor responses, we conducted the following studies to determine whether SCV-07 modulates STAT3-induced responses as part of its mechanism in stimulation of an anti-tumor immune response. Experimental design: In vitro studies were conducted using B16F0 melanoma cells, transiently transfected with a STAT3 responsive element driving luciferase expression. Cells were incubated with varying concentrations of SCV-07, and luciferase expression was measured after 24 hours of incubation. In in vivo studies Balb/c mice were injected with B16 melanoma cells and the mice were either left untreated or were treated with SCV-07 at 5 mg/kg. Tumors were harvested on day 11 and were analyzed by flow cytometry for the presence of P-STAT3-positive cells. Results: SCV-07 inhibited expression of STAT3 driven luciferase expression to the extent of ∼70 – 80%, depending on concentration of SCV-07. Further studies showed that SCV-07 additionally inhibited the translocation of STAT3 into the nucleus of HeLa cells. SCV-07 increased survival and inhibited the progression of melanoma growth in the B16 mouse model, and this inhibition was accompanied by reduced phosphorylated STAT3 staining at the tumor site as well as an influx of natural killer cells. Conclusions: These results provide support that SCV-07 acts in an antigen independent manner to reduce STAT3 driven gene expression and potentiate anti-tumor immune responses. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C107.

Cyclophosphamide-Induced Type-1 Diabetes in the NOD Mouse Is Associated with a Reduction of CD4+CD25+Foxp3+ Regulatory T Cells

Regulatory T cells (Tregs) have been implicated as key players in immune tolerance as well as suppression of antitumor responses. The chemotherapeutic alkylating agent cyclophosphamide (CY) is widely used in the treatment of tumors and some autoimmune conditions. Although previous data has demonstrated that Tregs may be preferentially affected by CY, its relevance in promoting autoimmune conditions has not been addressed. The nonobese diabetic mouse spontaneously develops type-1 diabetes (T1D). We demonstrate in this study that CY targets CD4+CD25+Foxp3+ Tregs in vivo. CD4+CD25+ T cells isolated from CY-treated mice display reduced suppressive activity in vitro and increased expression of apoptotic markers. Although Treg numbers rapidly recovered to pretreatment levels in the peripheral lymphoid tissues, Tregs failed to recover proportionally within pancreatic infiltrates. T1D progression was effectively prevented by adoptive transfer of a small number of islet Ag-specific CD4+CD25+ Tregs to CY-treated recipients. Prevention of T1D was associated with reduced T cell activation and higher Treg proportions in the pancreas. We conclude that acceleration of T1D by CY is associated with a reduction in CD4+CD25+Foxp3+ Tregs and can be prevented by transfer of CD4+CD25+ Tregs.