Tecovirimat is effective against human monkeypox virus in vitro at nanomolar concentrations

The ongoing monkeypox virus (MPXV) outbreak is the largest ever recorded outside of Africa. We isolated and sequenced a virus from the first clinical MPXV case diagnosed in France (May 2022). We report that tecovirimat (ST-246), a US Food and Drug Administration approved drug, is efficacious against this isolate in vitro at nanomolar concentrations, whereas cidofovir is only effective at micromolar concentrations. Our results support the use of tecovirimat in ongoing human clinical trials.

Thrombospondin-1 Silencing Improves Lymphocyte Infiltration in Tumors and Response to Anti-PD-1 in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is notoriously aggressive with a high metastatic potential, and targeted therapies are lacking. Using transcriptomic and histologic analysis of TNBC samples, we found that a high expression of thrombospondin-1 (TSP1), a potent endogenous inhibitor of angiogenesis and an activator of latent transforming growth factor beta (TGF-β), is associated with (i) gene signatures of epithelial-mesenchymal transition and TGF-β signaling, (ii) metastasis and (iii) a reduced survival in TNBC patients. In contrast, in tumors expressing low levels of TSP1, gene signatures of interferon gamma (IFN-γ) signaling and lymphocyte activation were enriched. In TNBC biopsies, TSP1 expression inversely correlated with the CD8+ tumor-infiltrating lymphocytes (TILs) content. In the 4T1 metastatic mouse model of TNBC, TSP1 silencing did not affect primary tumor development but, strikingly, impaired metastasis in immunocompetent but not in immunodeficient nude mice. Moreover, TSP1 knockdown increased tumor vascularization and T lymphocyte infiltration and decreased TGF-β activation in immunocompetent mice. Noteworthy was the finding that TSP1 knockdown increased CD8+ TILs and their programmed cell death 1 (PD-1) expression and sensitized 4T1 tumors to anti-PD-1 therapy. TSP1 inhibition might thus represent an innovative targeted approach to impair TGF-β activation and breast cancer cell metastasis and improve lymphocyte infiltration in tumors, and immunotherapy efficacy in TNBC.

Comprehensive analysis of current approaches to inhibit regulatory T cells in cancer

CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg) have emerged as a dominant T cell population inhibiting anti-tumor effector T cells. Initial strategies used for Treg-depletion (cyclophosphamide, anti-CD25 mAb…) also targeted activated T cells, as they share many phenotypic markers. Current, ameliorated approaches to inhibit Treg aim to either block their function or their migration to lymph nodes and the tumor microenvironment. Various drugs originally developed for other therapeutic indications (anti-angiogenic molecules, tyrosine kinase inhibitors,etc) have recently been discovered to inhibit Treg. These approaches are expected to be rapidly translated to clinical applications for therapeutic use in combination with immunomodulators.

Infiltrating and peripheral immune cell analysis in advanced gastric cancer according to the Lauren classification and its prognostic significance

BACKGROUND

The correlation between immune cells and the Lauren classification subtypes and their prognostic impact in advanced gastric cancer (AGC) are unknown.

METHODS

Circulating natural killer (NK) cells, CD4⁺ and CD8⁺ T cells, regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) were quantified in peripheral blood mononuclear cells (PBMCs) from 67 patients with untreated AGC enrolled in the PRODIGE 17-ACCORD 20 trial. CD56⁺ cells (NK), CD8⁺, and FoxP3⁺ (Treg) tumor-infiltrating lymphocytes (TILs) were assessed in tumor samples.

RESULTS

Circulating NK and Treg proportions were significantly lower in patients with diffuse/mixed-type AGC (n = 27) than those with intestinal type (n = 40; median 6.3% vs 11.5%; p = 0.02 and median 3.3% vs 5.2%; p = 0.03, respectively). Proportions of circulating MDSC, CD4⁺ and CD8⁺ T cells were not associated with one pathological type. Among tumor-infiltrating cells, CD8⁺ T cells, but not NK or FoxP3⁺ cells, were significantly lower in diffuse/mixed-type AGC (median 21 vs 59 cells/field; p = 0.009). Patients with high circulating NK cell counts (> 17%) had a better overall survival than those with < 17% (HR 0.40; 95% CI [0.15-1.06]; p = 0.04). Patients with high CD8⁺ TIL counts (> 31 cells/field) had significantly longer overall survival (HR 0.44; 95% CI [0.21-0.92]; p = 0.02). The prognostic value of CD8⁺ TILs was maintained after adjustment for confounding factors, including the Lauren classification (HR = 0.42; 95% CI [0.18-0.96]; p = 0.039).

CONCLUSION

Diffuse/mixed-type AGC has lower rates of CD8⁺ TILs and circulating NK cells and Tregs than the intestinal type. This "cold tumor" phenotype may be associated with a worse outcome.

TNFα blockade overcomes resistance to anti-PD-1 in experimental melanoma

Antibodies against programmed cell death-1 (PD-1) have considerably changed the treatment for melanoma. However, many patients do not display therapeutic response or eventually relapse. Moreover, patients treated with anti-PD-1 develop immune-related adverse events that can be cured with anti-tumor necrosis factor α (TNF) antibodies. Whether anti-TNF antibodies affect the anti-cancer immune response remains unknown. Our recent work has highlighted that TNFR1-dependent TNF signalling impairs the accumulation of CD8+ tumor-infiltrating T lymphocytes (CD8+ TILs) in mouse melanoma. Herein, our results indicate that TNF or TNFR1 blockade synergizes with anti-PD-1 on anti-cancer immune responses towards solid cancers. Mechanistically, TNF blockade prevents anti-PD-1-induced TIL cell death as well as PD-L1 and TIM-3 expression. TNF expression positively correlates with expression of PD-L1 and TIM-3 in human melanoma specimens. This study provides a strong rationale to develop a combination therapy based on the use of anti-PD-1 and anti-TNF in cancer patients.

Most melanoma patients do not respond to anti-PD1 therapy. Here, the authors show that TNFα blockade synergizes with anti-PD-1 by preventing anti-PD-1-induced CD8+ T cell death and TIM-3 expression on such cells.

Immune therapy in colorectal cancer

The evidence that the immune system, when rightly stimulated, can eradicate cancer cells, combined with the latest knowledge about antitumor immunity, has led to recent progress in cancer immunotherapy. While infiltration of tumors with immune cells is described in advanced stage colorectal cancer (CRC), the first data concerning the clinical efficacy of immune-targeted therapies in CRC patients were disappointing. The evidence of tumor responses in CRC patients with microsatellite instability treated with immune checkpoint blockers has renewed the interest for research in the field of CRC immunotherapy. In this article, we briefly review the role of T lymphocytes infiltrating CRC tumors in order to introduce a brief history of CRC immunotherapy and then current trials involving immune-based strategies and particularly immune checkpoint blockers.

Induction of resident memory T cells enhances the efficacy of cancer vaccine

Tissue-resident memory T cells (Trm) represent a new subset of long-lived memory T cells that remain in tissue and do not recirculate. Although they are considered as early immune effectors in infectious diseases, their role in cancer immunosurveillance remains unknown. In a preclinical model of head and neck cancer, we show that intranasal vaccination with a mucosal vector, the B subunit of Shiga toxin, induces local Trm and inhibits tumour growth. As Trm do not recirculate, we demonstrate their crucial role in the efficacy of cancer vaccine with parabiosis experiments. Blockade of TFGβ decreases the induction of Trm after mucosal vaccine immunization, resulting in the lower efficacy of cancer vaccine. In order to extrapolate this role of Trm in humans, we show that the number of Trm correlates with a better overall survival in lung cancer in multivariate analysis. The induction of Trm may represent a new surrogate biomarker for the efficacy of cancer vaccine. This study also argues for the development of vaccine strategies designed to elicit them.

IL-15 Trans-Signaling with the Superagonist RLI Promotes Effector/Memory CD8+ T Cell Responses and Enhances Antitumor Activity of PD-1 Antagonists

Tumors with the help of the surrounding environment facilitate the immune suppression in patients, and immunotherapy can counteract this inhibition. Among immunotherapeutic strategies, the immunostimulatory cytokine IL-15 could represent a serious candidate for the reactivation of antitumor immunity. However, exogenous IL-15 may have a limited impact on patients with cancer due to its dependency on IL-15Rα frequently downregulated in cancer patients. In this work, we studied the antitumor activity of the IL-15 superagonist receptor-linker-IL-15 (RLI), designed to bypass the need of endogenous IL-15Rα. RLI consists of human IL-15 covalently linked to the human IL-15Rα sushi(+) domain. In a mouse model of colorectal carcinoma, RLI as a stand-alone treatment could limit tumor outgrowth only when initiated at an early time of tumor development. At a later time, RLI was not effective, coinciding with the strong accumulation of terminally exhausted programmed cell death-1 (PD-1)(high) T cell Ig mucin-3(+) CD8(+) T cells, suggesting that RLI was not able to reactivate terminally exhausted CD8(+) T cells. Combination with PD-1 blocking Ab showed synergistic activity with RLI, but not with IL-15. RLI could induce a greater accumulation of memory CD8(+) T cells and a stronger effector function in comparison with IL-15. Ex vivo stimulation of tumor-infiltrated lymphocytes from 16 patients with renal cell carcinoma demonstrated 56% of a strong tumor-infiltrated lymphocyte reactivation with the combination anti-PD-1/RLI compared with 43 and 6% with RLI or anti-PD-1, respectively. Altogether, this work provides evidence that the sushi-IL-15Rα/IL-15 fusion protein RLI enhances antitumor activity of anti-PD-1 treatment and is a promising approach to stimulate host immunity.

VEGF-A modulates expression of inhibitory checkpoints on CD8+ T cells in tumors

Immune escape is a prerequisite for tumor development. To avoid the immune system, tumors develop different mechanisms, including T cell exhaustion, which is characterized by expression of immune inhibitory receptors, such as PD-1, CTLA-4, Tim-3, and a progressive loss of function. The recent development of therapies targeting PD-1 and CTLA-4 have raised great interest since they induced long-lasting objective responses in patients suffering from advanced metastatic tumors. However, the regulation of PD-1 expression, and thereby of exhaustion, is unclear. VEGF-A, a proangiogenic molecule produced by the tumors, plays a key role in the development of an immunosuppressive microenvironment. We report in the present work that VEGF-A produced in the tumor microenvironment enhances expression of PD-1 and other inhibitory checkpoints involved in CD8(+) T cell exhaustion, which could be reverted by anti-angiogenic agents targeting VEGF-A-VEGFR. In view of these results, association of anti-angiogenic molecules with immunomodulators of inhibitory checkpoints may be of particular interest in VEGF-A-producing tumors.

VEGF-A modulates expression of inhibitory checkpoints on CD8+ T cells in tumors

VEGF-A production in the tumor microenvironment enhances expression of PD-1 and other inhibitory checkpoints involved with CD8⁺ T cell exhaustion, which can be reversed with anti-VEGF/VEGFR treatment.

Immune escape is a prerequisite for tumor development. To avoid the immune system, tumors develop different mechanisms, including T cell exhaustion, which is characterized by expression of immune inhibitory receptors, such as PD-1, CTLA-4, Tim-3, and a progressive loss of function. The recent development of therapies targeting PD-1 and CTLA-4 have raised great interest since they induced long-lasting objective responses in patients suffering from advanced metastatic tumors. However, the regulation of PD-1 expression, and thereby of exhaustion, is unclear. VEGF-A, a proangiogenic molecule produced by the tumors, plays a key role in the development of an immunosuppressive microenvironment. We report in the present work that VEGF-A produced in the tumor microenvironment enhances expression of PD-1 and other inhibitory checkpoints involved in CD8⁺ T cell exhaustion, which could be reverted by anti-angiogenic agents targeting VEGF-A–VEGFR. In view of these results, association of anti-angiogenic molecules with immunomodulators of inhibitory checkpoints may be of particular interest in VEGF-A-producing tumors.

Colorectal cancer and immunity: What we know and perspectives

Strong evidence supports the concept of immunosurveillance and immunoediting in colorectal cancer. In particular, the density of T CD8⁺ and CD45⁺ lymphocyte infiltration was recently shown to have a better prognostic value than the classic tumor node metastasis classification factor. Other immune subsets, as macrophages, natural killer cells or unconventionnal lymphocytes, seem to play an important role. Induction of regulatory T cells (Tregs) or immunosuppressive molecules such as PD-1 or CTLA-4 and downregulation of antigen-presenting molecules are major escape mechanisms to antitumor immune response. The development of these mechanisms is a major obstacle to the establishment of an effective immune response, but also to the use of immunotherapy. Although immunotherapy is not yet routinely used in colorectal cancer, we now know that most treatments used (chemotherapy and biotherapy) have immunomodulatory effects, such as induction of immunogenic cell death by chemotherapy, inhibition of immunosuppression by antiangiogenic agents, and antibody-dependent cytotoxicity induced by cetuximab. Finally, many immunotherapy strategies are being developed and tested in phase I to III clinical trials. The most promising strategies are boosting the immune system with cytokines, inhibition of immunoregulatory checkpoints, vaccination with vectorized antigens, and adoptive cell therapy. Comprehension of antitumor immune response and combination of the different approaches of immunotherapy may allow the use of effective immunotherapy for treatment of colorectal cancer in the near future.

Control of the immune response by pro-angiogenic factors

The progressive conversion of normal cells into cancer cells is characterized by the acquisition of eight hallmarks. Among these criteria, the capability of the cancer cell to avoid the immune destruction has been noted. Thus, tumors develop mechanisms to become invisible to the immune system, such as the induction of immunosuppressive cells, which are able to inhibit the development of an efficient immune response. Molecules produced in the tumor microenvironment are involved in the occurrence of an immunosuppressive microenvironment. Recently, it has been shown that vascular endothelial growth factor A (VEGF-A) exhibits immunosuppressive properties in addition to its pro-angiogenic activities. VEGF-A can induce the accumulation of immature dendritic cells, myeloid-derived suppressor cells, regulatory T cells, and inhibit the migration of T lymphocytes to the tumor. Other pro-angiogenic factors such as placental growth factor (PlGF) could also participate in tumor-induced immunosuppression, but only few works have been performed on this point. Here, we review the impact of pro-angiogenic factors (especially VEGF-A) on immune cells. Anti-angiogenic molecules, which target VEGF-A/VEGFR axis, have been developed in the last decades and are commonly used to treat cancer patients. These drugs have anti-angiogenic properties but can also counteract the tumor-induced immunosuppression. Based on these immunomodulatory properties, anti-angiogenic molecules could be efficiently associated with immunotherapeutic strategies in preclinical models. These combinations are currently under investigation in cancer patients.

Timing of the intestinal barrier closure in puppies

As puppies are born with very low immunoglobulin concentrations, they rely on passive immune transfer from ingested colostrum to acquire a protective immunity during the first few weeks of life. The purpose of this study was to describe the timing of gut closure in canine neonates. Twenty-two Beagle puppies received 3 ml of standardized canine colostrum at 0, 4, 8, 12, 16 or 24 h after birth using a feeding tube. Blood immunoglobulins G (IgG, M and A) were assayed 0, 4 and 48 h after colostrum ingestion. IgG absorption rate was significantly affected by the time of colostrum administration, and the IgG concentrations in puppies serum 48 h after administration were significantly higher when colostrum was ingested at 0-4 h of age than at 8-12 h or 16-24 h (1.68 ± 0.4, 0.79 ± 0.07 and 0.35 ± 0.08 g/l, respectively; p < 0.001). In the canine species, gut closure seems thus to begin as early as 4-8 h after birth and to be complete at 16-24 h. Consequently, this phenomenon appears to occur earlier in puppies than in most other species.

Mucosal imprinting of vaccine-induced CD8⁺ T cells is crucial to inhibit the growth of mucosal tumors

Although many human cancers are located in mucosal sites, most cancer vaccines are tested against subcutaneous tumors in preclinical models. We therefore wondered whether mucosa-specific homing instructions to the immune system might influence mucosal tumor outgrowth. We showed that the growth of orthotopic head and neck or lung cancers was inhibited when a cancer vaccine was delivered by the intranasal mucosal route but not the intramuscular route. This antitumor effect was dependent on CD8⁺ T cells. Indeed, only intranasal vaccination elicited mucosal-specific CD8⁺ T cells expressing the mucosal integrin CD49a. Blockade of CD49a decreased intratumoral CD8⁺ T cell infiltration and the efficacy of cancer vaccine on mucosal tumor. We then showed that after intranasal vaccination, dendritic cells from lung parenchyma, but not those from spleen, induced the expression of CD49a on cocultured specific CD8⁺ T cells. Tumor-infiltrating lymphocytes from human mucosal lung cancer also expressed CD49a, which supports the relevance and possible extrapolation of these results in humans. We thus identified a link between the route of vaccination and the induction of a mucosal homing program on induced CD8⁺ T cells that controlled their trafficking. Immunization route directly affected the efficacy of the cancer vaccine to control mucosal tumors.

Impact of antiangiogenic treatments on exhausted PD-1+ T lymphocytes in colorectal cancer

e22121

Background: Tumors develop immunosuppressive mechanisms to escape the immune system. Among these mechanisms, T lymphocytes can express inhibitory molecules such as Program Death-1 (PD-1) protein which impair their activation and their effector functions. Multi-target anti-angiogenic tyrosine kinase inhibitors (TKI) that are routinely used as first- or second-line treatment of cancer patients, have been shown to modulate immunosuppressive mechanisms especially regulatory T cells. However, the role of specific VEGF/VEGFR blockade on PD-1 expression by T lymphocytes has not been studied. Methods: PD-1 expression on T lymphocytes has been analyzed by flow cytometry in a mouse model of colorectal cancer (CT26) treated by anti-angiogenic molecules targeting the VEGF-A/VEGFR axis and in the peripheral blood of metastatic colorectal cancer patients. Results: Sunitinib that directly targets VEGFR, PDGFR, c-kit, but also anti-VEGF-A antibody (the mouse orthologue of bevacizumab) decrease PD-1 expression on T lymphocytes infiltrating the tumors. Interestingly, anti-angiogenic treatments decrease the percentage of lymphocytes expressing not only PD-1 but also Tim-3 suggesting that the most exhausted T cells are targeted by anti-angiogenic treatments. Administration of masitinib, a TKI acting on KIT, PDGFR and FAK but not on the VEGF/VEGF-R pathway, was not able to modulate PD-1 expression on T cells. Finally, anti-VEGF-A treatment (bevacizumab) associated with chemotherapy decreases the proportion of PD-1+ CD4+T cells in the peripheral blood of metastatic colorectal cancer patients. Conclusions: These results show that anti-angiogenic treatments targeting VEGFA/VEGFR decrease PD-1-expressing T lymphocytes in colorectal cancer. These results suggest that VEGF-A could be involved in PD-1 expression and maybe in the induction of T lymphocyte exhaustion in colorectal cancer. We and others have shown that anti-angiogenic molecules could modulate other immunosuppressive populations such as regulatory T cells and myeloid suppressive cells, anti-angiogenic molecules might be efficiently associated with immunotherapeutic strategies in colorectal cancer.

Abstract 2830: Mucosal imprinting of vaccine induced-CD8+T cells is crucial to inhibit mucosal tumors

Although many human cancers are located in mucosal sites, most cancer vaccines are tested against subcutaneous tumors in preclinical models. The utility of preferentially inducing an anti-tumor immune response in the mucosal anatomic site of tumors has never been addressed. We therefore wondered whether mucosa-specific homing instructions to the immune system might influence mucosal tumor outgrowth. For this purpose, we set up original orthotopic models of head and neck and lung cancers monitored by magnetic resonance imaging or luciferase based in vivo optical imaging and vaccine based on a non replicative delivery system, the B subunit of Shiga toxin (STxB) as mucosal vector which has previously been shown to target antigen to dendritic cells. We showed that the growth of orthotopic head and neck or lung cancers expressing the E7 protein from HPV16 was only inhibited, when a cancer vaccine was delivered by the intranasal (i.n) mucosal and not the intramuscular (i.m) route. This anti-tumor effect was dependent on mucosal CD8+T cells as : i) Only a vaccine composed of STxB coupled to an E7 derived polypeptide (STxB-E7), but not the free E7 polypeptide elicited mucosal CD8+T cells. This mucosal induction of anti-E7 CD8+T cells, but not the systemic (spleen) specific anti-E7 CD8+T cells correlated with mucosal tumor protection. ii) A greater mucosal tumor infiltration of CD8+T cells was detected 7 days after tumor graft in mice that had been previously intranasally immunized with STxB-E7, than in mice vaccinated by the i.m. route. iii) CD8+T cell-depleted mice vaccinated with STxB-E7 by the i.n. route died before 20 days, whereas mice survived more than 6 months without CD8 depletion. As control, both routes of vaccine administration controlled the growth of subcutaneous tumors and elicited anti-E7 specific CD8+T cells in the spleen. To explain this finding, we demonstrated that only i.n. vaccination elicited mucosal specific CD8+T cells expressing the mucosal integrin CD49a. Blockade of CD49a decreased intratumoral CD8+T cell infiltration and the efficacy of cancer vaccine on mucosal tumor. We then showed that after intranasal vaccination, only dendritic cell from lung parenchyma, but not from spleen induced the expression of CD49a on co-cultured specific CD8+T cells. Tumor-infiltrating lymphocytes from human mucosal lung cancer also expressed CD49a at higher levels than TIL from non mucosal tumors, supporting the relevance and possible extrapolation of these results in humans. We thus identified a link between the route of vaccination and the induction of a mucosal homing program on induced CD8+T cells controlling their trafficking with a direct application on the efficacy of cancer vaccine to control mucosal tumors.

Citation Format: Federico Sandoval, Mevyn Nizard, Magali Terme, Cecile Badoual, Michel-Francis Bureau, Olivier Clement, Elie Marcheteau, Alain Gey, Estelle Dransart, Françoise Quintin-Colonna, Gwenhael Autret, Tzyy-Choou Wu, Wolf H. Fridman, Ludger Johannes, Eric Tartour. Mucosal imprinting of vaccine induced-CD8+T cells is crucial to inhibit mucosal tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2830. doi:10.1158/1538-7445.AM2013-2830

Abstract 373: Impact of anti-angiogenic treatments on exhausted PD-1+ T lymphocytes in colorectal cancer

Background: The concept of cancer immunosurveillance suggests that the immune system can recognize and destroy tumor cells. However, tumors can develop immunosuppressive mechanisms to escape the immune system. Among the immunosuppressive mechanisms, T lymphocytes can express inhibitory molecules such as Program Death-1 (PD-1) protein which impair their activation. PD-1 activation by its ligands PD-L1 and PD-L2 blocks T cell proliferation, cytolytic activity, cytokine production, and decreases survival. Multi-target anti-angiogenic tyrosine kinase inhibitors (TKI) that are routinely used as first- or second-line treatment of cancer patients, have been shown to modulate immunosuppressive mechanisms especially regulatory T cells. However, the role of specific VEGF/VEGFR blockade on PD-1 expression by T lymphocytes has not been studied.

Materiel and methods: PD-1 expression on T lymphocytes has been analyzed by flow cytometry in a mouse model of colorectal cancer (CT26) treated by anti-angiogenic molecules targeting the VEGF-A/VEGFR axis and in the peripheral blood of metastatic colorectal cancer patients.

Results: Tumor-infiltrating CD4+ and CD8+ T lymphocytes express high levels of PD-1 in the CT26 tumor model. Sunitinib that directly targets VEGFR, PDGFR, c-kit, decreases PD-1 expression on CD4+ and CD8+ T lymphocytes infiltrating the tumors. In the same manner, anti-VEGF-A antibody (the mouse orthologue of bevacizumab) restrains PD-1 expression on tumor-infiltrating T lymphocytes. Interestingly, anti-angiogenic treatments decrease the percentage of lymphocytes expressing not only PD-1 but also Tim-3 suggesting that the most exhausted T cells are targeted by anti-angiogenic treatments. Administration of masitinib, a tyrosine kinase inhibitor acting on KIT, PDGFR and FAK but not on the VEGF/VEGF-R pathway, was not able to modulate PD-1 expression on T cells. Finally, anti-VEGF-A treatment (bevacizumab) associated with chemotherapy decreases the proportion of PD-1+ CD4+ T cells in the peripheral blood of metastatic colorectal cancer patients.

Conclusions: These results show that anti-angiogenic treatments targeting VEGFA/VEGFR decrease PD-1-expressing T lymphocytes in colorectal cancer. These results suggest that VEGF-A could be involved in PD-1 expression and maybe in the induction of T lymphocyte exhaustion in colorectal cancer. This point is currently under investigation. We and others have shown that anti-angiogenic molecules could modulate other immunosuppressive populations such as regulatory T cells and myeloid suppressive cells, anti-angiogenic molecules might be efficiently associated with immunotherapeutic strategies in colorectal cancer.

Citation Format: Magali Terme, Thibault Voron, Elie Marcheteau, Orianne Colussi, Simon Pernot, Eric Tartour, Julien Taieb. Impact of anti-angiogenic treatments on exhausted PD-1+ T lymphocytes in colorectal cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 373. doi:10.1158/1538-7445.AM2013-373

VEGFA-VEGFR pathway blockade inhibits tumor-induced regulatory T-cell proliferation in colorectal cancer

Multitarget antiangiogenic tyrosine kinase inhibitors (TKI) have been shown to reduce regulatory T cells (Treg) in tumor-bearing animals and patients with metastatic renal carcinomas. However, a direct role of the VEGF-A/VEGFR pathway inhibition in this phenomenon is a matter of debate and molecular mechanisms leading to Treg modulation in this setting have not been explored to date. Treg proportion, number, and proliferation were analyzed by flow cytometry in peripheral blood of patients with metastatic colorectal cancer (mCRC) treated with bevacizumab, a monoclonal antibody targeting specifically VEGF-A, and in colon cancer-bearing mice (CT26) treated with drugs targeting the VEGF/VEGFR axis. The direct impact of VEGF-A on Treg induction was assessed together with specific blockade of different isoforms of VEGFRs that may be involved. In CT26-bearing mice, anti-VEGF antibody and sunitinib treatments reduced Treg but masitinib, a TKI not targeting VEGFR, did not. Targeting VEGF-A/VEGFR axis seems sufficient to affect Treg percentages, without any changes in their function. Similarly, bevacizumab inhibited Treg accumulation in peripheral blood of patients with mCRCs. In vitro, Treg expressing VEGFR from tumor-bearing mice directly proliferated in response to VEGF-A. Anti-VEGF-A treatment decreased Treg proliferation in mice as well as in patients with mCRCs. VEGFR-2- but not VEGFR-1-specific blockade led to the same results. We identified a novel mechanism of tumor escape by which VEGF-A directly triggers Treg proliferation. This proliferation is inhibited by VEGF-A/VEGFR-2 blockade. Anti-VEGF-A therapies also have immunologic effects that may be used with a therapeutic goal in the future.

Abstract 5388: Local mucosal CD8+T cell response is required to inhibit the growth of orthotopic head and neck and lung cancers

Tumors may be located at mucosal or non-mucosal sites. However, the clinical benefit of preferentially inducing an anti-tumor immune response in the anatomic site of tumors has never been addressed. We set up orthotopic models of head and neck and lung cancers to compare the systemic and local anti-tumor immune response after administration of a cancer vaccine by mucosal and systemic routes. We also selected a non replicative delivery system, the B subunit of Shiga toxin (STxB), as a mucosal vector able to target dendritic cells. We show that intranasal immunization of mice with STxB based vaccine is the best route to elicit polyfunctional specific CD8+T cells in cervical and mediastinal lymph node than the use of non vectorized antigen or the intramuscular route. In line with these results, nasal mucosal administration of a model tumor antigen (E7 polypeptide from HPV 16) targeted to dendritic cells by STxB is more efficient to inhibit the growth of established orthotopic head and neck and lung cancers expressing the E7 antigen, than the administration of non vectorized antigen or the use of intramuscular route. A higher infiltration of CD8+T cells was detected 7 days after tumor graft, when mice were previously intranasally immunized with STxB-E7, than in mice vaccinated by the intramuscular route. Specific anti-E7 CD8+T cell tumor infiltration, was only observed after nasal immunization. Indeed, depletion of CD8+T cells inhibited the clinical efficiency of tumor vaccine demonstrating their role in tumor protection. In contrast, both routes completely controlled the growth of a subcutaneously E7 expressing tumor, which correlated with a similar induction of anti-E7 CD8+T cells in the spleen. Analysis of Integrin and chemokine receptor expression on tetramere positive cells showed that intranasal immunization induced higher levels of CD103 on T cells in bronchoalveolar lavage than intramuscular immunization with the same vaccine. This study emphasizes the need to elicit a potent anti-tumor response at the anatomic site of tumor and not just in the systemic compartment to induce tumor regression. This was achieved by i) administration of the vaccine by the intranasal route which was efficient in inducing CD8+T cells response at both locoregional and systemic sites allowing the control of both mucosal and non mucosal tumors. ii) The targeting of antigen to dendritic cells by STxB. This study is relevant to humans, as 30% of head and neck cancers express HPV16. Our results support the development of STxB-E7 vaccine administered by the i.n. route for the treatment of these HPV associated head and neck cancers. More generally, this study provides direct evidence for the compartmentalization of tumor immunity, a critical finding for the design of better cancer vaccines.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5388. doi:1538-7445.AM2012-5388

Pitfalls in anti-influenza T cell detection by Elispot using thimerosal containing pandemic H1N1 vaccine as antigen

Monitoring T cells in combination with humoral response may be of value to predict clinical protection and cross-protective immunity after influenza vaccination. Elispot technique which measures cytokine produced after antigen-specific T cell stimulation is used routinely to detect and characterize anti-viral T cells. We found that the preservative thimerosal present in most H1N1 pandemic vaccines, induced in vitro abortive activation of T cells followed by cell death leading to false-positive results with the Elispot technique. The size of the spots, usually not measured in routine analysis, appears to be a discriminative criterion to detect this bias. Multi-dose vials of vaccine containing thimerosal remain important for vaccine delivery and our results alert about false-positive results of Elispot to monitor the clinical efficacy of these vaccines. We showed that this finding extends for other T cell monitoring techniques based on cytokine production such as ELISA. Although measuring in vitro immune response using the whole vaccine used for human immunization directly reflects in vivo global host response to the vaccine, the present study strongly supports the use of individual vaccine components for immune monitoring due to the presence of contaminants, such as thimerosal, leading to a bias in interpretation of the results.