Recruitment Of Immunosuppressive Myeloid Cells Research Articles

Abstract 655: Necroptosis promotes tumor growth through IL1-alpha release and recruitment of immunosuppressive myeloid cells

Abstract Programmed cell death (PCD) was originally limited to apoptosis, but now includes pyroptosis, ferroptosis, necroptosis, and paraptosis. Necroptosis has attracted particular interest as an approach for immunotherapy as activation of the RIPK1/RIPK3 necrosome phosphorylates MLKL to form membrane pores, leading to loss of integrity and enhanced ability to induce an antigen-specific immune response in models of vaccination. Here we sought to determine if necroptosis within tumor cells was an important regulatory of anti-tumor immunity. Deficiency in Ripk3 or Mlkl did not impact tumor incidence or growth in genetic models of mammary carcinoma or lung adenocarcinoma. Similarly, the growth of syngeneic cell lines was not altered by loss of Ripk3 or Mlkl in vitro or in vivo. We next examined the induction of apoptosis or necroptosis in syngeneic tumor models using genetic constructs with doxycycline-controlled expression. In line with published data, subcutaneous vaccination demonstrated that RIPK3-induced necroptosis promoted an antigen-specific CD8+ T cell response greater than that observed with caspase 8-induced apoptosis. Surprisingly however, when necroptosis was induced within established PyMT-B6 orthotopic mammary tumors, we observed significantly reduced survival, which correlated with higher neutrophil and macrophage recruitment, along with lower CD8+ T cell infiltration and IFN-γ expression. In vitro, necroptosis induced with either RIPK3 or MLKL greatly enhanced expression of Cxcl1 and Cxcl2, a property that could be recapitulated by transferring dead cell supernatant to live cells, suggesting the presence of an alarmin or damage-associated molecular pattern (DAMP). We therefore knocked out MyD88, which serves as a critical adapter protein to a number of surface receptors, including the TLR family, the IL1 receptor, and RAGE. The loss of MyD88 completely eliminated the ability of tumor cells to express Cxcl1 in response to supernatant from necrotic cells. Expression was not driven by release of HMGB1 or signaling through RAGE or TLRs. Instead, we found that blocking the interleukin (IL)1 receptor or IL1α, but not IL1β, prevented Cxcl1 expression. IL1α is a constitutively expressed by some tumors, suggesting a potential role for IL1α in regulating immune responses to therapies that induce necrotic-like forms of cell death. In support of this, Il1a expression was strongly predictive of progression free survival in triple-negative breast cancer. These findings suggest that IL1α has an unexplored role in regulating the tumor microenvironment. By understanding how IL1α regulates the immune response during cytotoxic therapy, our findings may explain why certain therapies are immunogenic (or not) in different cancers. Citation Format: Kay Hänggi, Aysenur Keske, Alycia Gardner, Jie Li, Olabisi Osunmakinde, Daiana Celias, Amer Beg, Brian Ruffell. Necroptosis promotes tumor growth through IL1-alpha release and recruitment of immunosuppressive myeloid cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 655.

Abstract A15: Integrated biomarker trials to evaluate myeloid and lymphoid composition of HNSCC and solid tumors treated with pepinemab and combinations with checkpoint inhibitors

Abstract Recruitment of immunosuppressive myeloid cells into the tumor microenvironment (TME) is a critical limitation to the efficacy of immune checkpoint inhibitors (ICIs) in patients with head and neck squamous cell carcinoma (HNSCC). In preclinical models, antibody blockade of Semaphorin 4D (SEMA4D, CD100) reduced function and recruitment of immunosuppressive myeloid cells within the TME. Importantly, combinations of anti-SEMA4D with ICIs enhanced T-cell activity and tumor regression. Pepinemab, an IgG4 humanized monoclonal antibody targeting SEMA4D, is currently being evaluated in window of opportunity, integrated biomarker trials to characterize immunomodulatory effects of treatment. SEMA4D exerts multifaceted effects within the tumor microenvironment by creating a barrier at the tumor-stroma margin, restricting immune cell infiltration and promoting immunosuppressive activity of myeloid-derived cells. In preclinical in vitro and in vivo studies, blocking antibody to SEMA4D directly enhanced M1/M2 ratio and reduced both expression of chemokines that recruit MDSC and the ability of MDSC to suppress T-cell activity. SEMA4D antibody treatment simultaneously restored the ability of dendritic cells and cytotoxic T cells to infiltrate the TME and increased ratio of Teffector to Tregulatory cells. This coordinated shift from immunosuppression to tumoricidal activity complemented effects of other immunotherapies in syngeneic tumor models. At present, three biomarker-driven window of opportunity trials are recruiting patients with four resectable indications to investigate novel combinations of pepinemab with ICIs: 1) HNSCC (NCT03690986, n=36), 2) pancreatic ductal adenocarcinoma and colorectal cancer with resectable liver metastases (NCT03373188, n=32), and 3) metastatic melanoma (NCT03769155, n=36). Presurgical treatment cohorts include combinations of pepinemab with nivolumab and /or ipilimumab, single agents, or no treatment. Three to seven weeks later, surgically resected tumors are collected under the guidance of a pathologist for comparison of tumor infiltrates across treatment groups and with a predose tissue biopsy. Blood is collected for PK, PD, and additional correlative biomarker assessments. Correlative multiplex flow cytometric and immunohistochemistry panels have been established to phenotype cells in the TME and periphery; preliminary biomarker analysis will be presented. Additional objectives include evaluation of pathologic response and extension of the previously reported safety profile of pepinemab to additional ICI combination therapies. Twelve subjects, including two HNSCC patients, have been enrolled in these studies as of 01 Feb 2019. These trials will provide the first integrated clinical assessment of the use of anti-SEMA4D antibody to reprogram the TME. Citation Format: Elizabeth E. Evans, Gregory B. Lesinski, Terrence L. Fisher, Crystal Mallow, Brian Olson, Paul E. Clavijo, John E. Leonard, Desa Rae Pastore, Ernest S. Smith, Maurice Zauderer, Clint T. Allen, Michael Lowe, Ragini Kudchadkar, Christina Wu, Conor Steuer, Nabil F. Saba. Integrated biomarker trials to evaluate myeloid and lymphoid composition of HNSCC and solid tumors treated with pepinemab and combinations with checkpoint inhibitors [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr A15.

Interim subgroup analysis for response by PD-L1 status of CLASSICAL-Lung, a phase Ib/II study of pepinemab (VX15/2503) in combination with avelumab in advanced NSCLC.

3011 Background: Antibody blockade of semaphorin 4D (SEMA4D, CD100) promotes tumoral dendritic cell and CD8+ T cell infiltration and reduces function and recruitment of immunosuppressive myeloid cells. Importantly, these mechanisms to overcome immune exclusion and suppression have been shown to complement immune checkpoint therapies in preclinical models. Pepinemab is an IgG4 humanized monoclonal antibody targeting semaphorin 4D. The CLASSICAL-Lung clinical trial tests the combination of pepinemab with avelumab to couple T cell activation via checkpoint inhibition with beneficial modifications of the immune microenvironment via pepinemab. Methods: This phase 1b/2, single arm, first-in-human study is designed to evaluate the safety, tolerability and efficacy of pepinemab with avelumab in 62 patients (pts) with advanced (stage IIIB/IV) non-small cell lung cancer (NSCLC), including immunotherapy-naïve (ION) pts and pts whose tumors progressed following immunotherapy (IOF). Results: Among 21 evaluable ION pts, 5 experienced partial response (PR), 3 pts had clinical benefit ≥ 1 year, and the disease control rate (DCR) is 81%. Pts enrolled in this study were observed to have lower PD-L1 expression relative to prior single agent studies (likely due to approval of pembrolizumab for first line therapy). We, therefore, performed subgroup analysis for response by PD-L1 status. The objective tumor response (ORR) in the PD-L1 negative and low population ( < 80% TPS by Dako 73-10 assay) appears to be approximately 2-2.5 fold greater with combination therapy than with historical single agent immune checkpoint controls. Notably, 97% of pts who experienced PR or SD were reported to have tumors with negative or low PD-L1 expression. Among 29 evaluable IOF pts, the combination resulted in 59% DCR, including 2 PR and 7 patients with durable clinical benefit of ≥ 23 weeks. Biomarker analysis of pre- and on-treatment biopsies confirmed increased CD8+ T cell density correlating with response. Surprisingly, analysis of myeloid-derived suppressor cells (MDSCs) revealed a relative paucity of these cells in pretreatment NSCLC biopsies as compared to other cancer indications such as HNSCC. Conclusions: This trial is nearing completion with only 5 of 62 subjects remaining on study. Preliminary data suggest the combination is well tolerated and shows signs of increased antitumor activity, particularly in PD-L1 negative or low tumors. Updated clinical response data and immunophenotypic analyses will be presented. Clinical trial information: NCT03268057 .

Abstract CT016: Integrated biomarker trials of VX15/2503 (pepinemab) in combination with checkpoint inhibitors in window of opportunity studies in solid tumors

Abstract Interrogation of the tumor microenvironment (TME) is crucial to provide insight into biological activity, resistance mechanisms and implementation of rational combination immunotherapies. Semaphorin 4D (SEMA4D, CD100) has broad immunomodulatory effects in the TME. In preclinical models, antibody blockade of SEMA4D promoted immune infiltration and reduced function and recruitment of immunosuppressive myeloid cells within the TME. Importantly, preclinical combinations of anti-SEMA4D with immune checkpoint inhibitors (ICIs) enhanced T cell activity and tumor regression. VX15/2503 (pepinemab), an IgG4 humanized monoclonal antibody targeting SEMA4D, is currently being evaluated in window of opportunity, integrated biomarker trials to characterize immunomodulatory effects in pancreatic (PDAC), colorectal (CRC), and head and neck squamous cell (HNSCC) carcinomas, and melanoma. At present, three biomarker trials are recruiting patients with four resectable indications to investigate novel combinations of pepinemab with ICIs; 1) PDAC and CRC with resectable liver mets (NCT03373188, n=32), 2) HNSCC (NCT03690986, n=36), and 3) metastatic melanoma (NCT03769155, n=36). Prior to surgery, patients enroll in treatment cohorts including combinations of pepinemab with nivolumab and /or with ipilimumab, single agents, or no treatment. Three to seven weeks later, patients will undergo surgery and a substantial surgical section will be collected under the guidance of a pathologist for comparison across treatment groups and with a pre-dose tissue biopsy. Blood will be collected for PK, PD, and additional correlative biomarker assessments. The primary objective is to evaluate the treatment-induced effects on the immune profile in the TME and in peripheral blood. Additional objectives include, extending the previously reported safety profile of single agent pepinemab to ICI combination therapies, as well as exploring pathologic and radiographic responses in the melanoma study. Correlative multiplex flow cytometric flow panels have been established to phenotype cells in the TME and periphery. A multiplex IHC assay utilizing a sequential probe and strip procedure has also been qualified that allows co-localization, spatial orientation, and quantitation of multiple immune markers. Analysis of immune subsets include but are not limited to activated T cells, neutrophils, Treg cells, DCs, monocytes, macrophages, and importantly myeloid-derived suppressor cells (MDSCs). Target engagement and expression of SEMA4D and its cognate receptors will also be evaluated. Seven subjects have been enrolled in these studies as of 7 Jan 2019. These trials will provide the first integrated clinical assessment of anti-SEMA4D antibody activity to reprogram the TME. Citation Format: Gregory B. Lesinski, Terrence L. Fisher, Elizabeth E. Evans, John E. Leonard, Desa Rae Pastore, Crystal Mallow, Ernest Smith, Maurice Zauderer, Conor Steuer, Nabil F. Saba, Michael Lowe, Ragini R. Kudchadkar, Brian Olson, Christina Wu. Integrated biomarker trials of VX15/2503 (pepinemab) in combination with checkpoint inhibitors in window of opportunity studies in solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT016.

Abstract CT086: Interim results from CLASSICAL-Lung, a Phase Ib/II study of VX15/2503 (pepinemab) in combination with avelumab in advanced NSCLC

Abstract Background: Blockade of the PD/PD-L1 pathway is an effective immunotherapy for NSCLC, however rational combination therapies are needed to overcome resistance mechanisms. VX15/2503 (pepinemab) is an IgG4 humanized monoclonal antibody targeting semaphorin 4D (SEMA4D, CD100). In vivo preclinical models demonstrated antibody blockade of SEMA4D promoted immune infiltration and reduced function and recruitment of immunosuppressive myeloid cells within the tumor. Importantly, preclinical combinations of anti-SEMA4D with various immunotherapies enhanced T cell activity and tumor regression. Avelumab is a fully human IgG1 antibody specific for PD-L1 and has been approved for both Merkel cell and urothelial carcinomas. The CLASSICAL-Lung clinical trial tests the combination of pepinemab with avelumab to couple immune activation via checkpoint inhibition with beneficial modifications of the immune microenvironment via pepinemab. Here, we present interim results of the dose escalation portion of the CLASSICAL-Lung study. Methods: This Phase Ib/II, open label, single arm, first-in-human combination study is designed to evaluate the safety, tolerability and efficacy of pepinemab in combination with avelumab in 62 subjects with advanced (IIIB/IV) NSCLC. The trial is split into dose escalation (n=12) and dose expansion (n=50) phases. The dose escalation portion includes patients who are immunotherapy naïve and have either progressed or declined standard first or second-line systemic anticancer therapy. The expansion phase includes a similar patient cohort as well as a second cohort of patients whose tumors progressed during or following immunotherapy. Patients in the dose escalation cohorts received ascending doses of pepinemab (5, 10, 20 mg/kg, Q2W) in combination with avelumab (10mg/kg, Q2W). The primary objective of dose escalation is safety, tolerability, and identification of the RP2D for dose expansion. Secondary objectives include evaluation of efficacy, immunogenicity, and PK/PD, and an exploratory objective is to identify candidate biomarkers of activity. Results / Conclusions: Dose escalation was successfully completed. The combination was found to be well tolerated at all dose levels tested and the RP2D was selected as 10mg/kg pepinemab Q2W (with 10mg/kg avelumab Q2W) for the dose expansion phase. No concerning safety signals have been identified to date. The most frequent related AEs were grades 1 or 2 fatigue, pyrexia, or chills; no grade 3 AE occurred in more than one subject. One DLT, a grade 3 pulmonary embolism occurred in the 10mg/kg pepinemab cohort, resolved and did not recur in that same subject or additional subjects in any cohort. The disease control rate to date in all dose escalation patients treated for at least two months is 90%. More detailed data from the dose escalation cohorts will be presented, as well as an enrollment update for the dose expansion phase. Clinical trial information: NCT03268057 Citation Format: Michael Shafique, Terrence L. Fisher, Elizabeth E. Evans, John E. Leonard, Desa Rae Pastore, Crystal Mallow, Ernest Smith, Maurice Zauderer, Andreas Schröeder, Kevin Chin, Thaddeus Beck, Megan Baumgart, Rachel E. Sanborn, Jonathan W. Goldman. Interim results from CLASSICAL-Lung, a Phase Ib/II study of VX15/2503 (pepinemab) in combination with avelumab in advanced NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT086.

Preliminary results from CLASSICAL-Lung, a phase 1b/2 study of pepinemab (VX15/2503) in combination with avelumab in advanced NSCLC.

2601 Background: Rational combination therapies are needed to overcome resistance mechanisms in NSCLC. Pepinemab is an IgG4 humanized monoclonal antibody targeting semaphorin 4D (SEMA4D, CD100). In vivo preclinical models demonstrated antibody blockade of SEMA4D promoted immune infiltration and reduced function and recruitment of immunosuppressive myeloid cells within the tumor. Importantly, preclinical combinations of anti-SEMA4D with various immunotherapies enhanced T cell activity and tumor regression. The CLASSICAL-Lung clinical trial tests the combination of pepinemab with avelumab to couple immune activation via checkpoint inhibition with beneficial modifications of the immune microenvironment via pepinemab. Methods: This ongoing phase 1b/2, open label, single arm, first-in-human combination study is designed to evaluate the safety, tolerability and efficacy of pepinemab in combination with avelumab in 62 patients (pts) with advanced (stage IIIB/IV) NSCLC (NCT03268057). The trial is split into dose escalation (n = 12) and dose expansion (n = 50) phases and includes 2 cohorts; 1) pts who are immunotherapy naïve, and 2) pts whose tumors progressed during or following immunotherapy (IO failure). Pts in the dose escalation cohorts received ascending doses of pepinemab i.v. (5, 10, 20 mg/kg, Q2W) in combination with avelumab i.v. (10mg/kg, Q2W). Results: Dose escalation is complete and the RP2D was selected as 10mg/kg pepinemab, Q2W. No pts experienced a TRAE leading to study discontinuation or death. The most frequent related AEs were grades 1 or 2 fatigue, pyrexia, or chills; no grade 3 AEs occurred in more than one subject. One DLT, a grade 3 pulmonary embolism occurred in the 10mg/kg pepinemab cohort, and resolved without reoccurrence. The disease control rate for pts treated > 2 months is 90% (19/21), and, at this early stage, a PR with a 49% reduction in target lesion was observed in at least 1 of 8 pts in the IO failure cohort. Updated data from the dose expansion phase will be presented. Conclusions: Preliminary data suggest the combination is well tolerated and shows initial signals of antitumor activity. Dose escalation is complete and the expansion phase is ongoing. Clinical trial information: NCT03268057.

Pilot integrated biomarker study of VX15/2503 in combination with ipilimumab and/or nivolumab in patients with resectable metastatic melanoma.

TPS9603 Background: Interrogation of the tumor microenvironment (TME) is crucial to provide insight into biological activity, resistance mechanisms and implementation of rational combination immunotherapies. Semaphorin 4D (SEMA4D, CD100) has broad immunomodulatory effects in the TME. In preclinical models, blockade of SEMA4D promoted immune infiltration and reduced recruitment of immunosuppressive myeloid cells. Preclinical combinations of anti-SEMA4D with immune checkpoint inhibitors (ICIs) enhanced T cell activity and tumor regression. VX15/2503 (pepinemab), an IgG4 humanized monoclonal antibody targeting SEMA4D, is being evaluated in an integrated biomarker trial to characterize immunomodulatory effects in melanoma (NCT03769155). Methods: Patients with biopsy-proven stage IIIB, C, and D melanoma are eligible. Prior to curative-intent surgery, patients receive pepinemab alone or in combination with nivolumab and/or ipilimumab every three weeks for two doses. A control cohort proceed directly to surgery. Resection specimens will be collected for comparison across treatment groups and with a pre-treatment biopsy. Blood will be collected for PK, PD, and correlative biomarker assessments. The primary objective is to evaluate effects on the immune profile in TME and peripheral blood. Additional objectives include safety of pepinemab (alone and in combination with ICI), and pathologic and radiographic responses. Multiplex flow cytometry panels were created to phenotype cells in the TME and periphery. A multiplex IHC assay utilizing a sequential probe and strip procedure has been qualified that allows co-localization, orientation, and quantification of multiple immune markers. Analysis of immune subsets include cytotoxic T cells, neutrophils, Tregs, DCs, monocytes, macrophages, and myeloid-derived suppressor cells. Target engagement and expression of SEMA4D and its receptors will be evaluated. As of 01 Feb 2019, 8 of 36 patients have been enrolled. This trial will provide the first biomarker-driven clinical assessment of anti-SEMA4D antibody activity to reprogram the TME. Clinical trial information: NCT03769155.

CAR T-Cells Targeting the Integrin αvβ6 and Co-Expressing the Chemokine Receptor CXCR2 Demonstrate Enhanced Homing and Efficacy against Several Solid Malignancies.

Despite the unprecedented clinical success of chimeric antigen receptors (CAR) T-cells against haematological malignancy, solid tumors impose a far greater challenge to success. Largely, this stems from an inadequate capacity of CAR T-cells that can traffic and maintain function within a hostile microenvironment. To enhance tumor-directed T-cell trafficking, we have engineered CAR T-cells to acquire heightened responsiveness to interleukin (IL)-8. Circulating IL-8 levels correlate with disease burden and prognosis in multiple solid tumors in which it exerts diverse pathological functions including angiogenesis, support of cancer stem cell survival, and recruitment of immunosuppressive myeloid cells. To harness tumor-derived IL-8 for therapeutic benefit, we have co-expressed either of its cognate receptors (CXCR1 or CXCR2) in CAR T-cells that target the tumor-associated αvβ6 integrin. We demonstrate here that CXCR2-expressing CAR T-cells migrate more efficiently towards IL-8 and towards tumor conditioned media that contains this cytokine. As a result, these CAR T-cells elicit superior anti-tumor activity against established αvβ6-expressing ovarian or pancreatic tumor xenografts, with a more favorable toxicity profile. These data support the further engineering of CAR T-cells to acquire responsiveness to cancer-derived chemokines in order to improve their therapeutic activity against solid tumors.

Blocking colony stimulating factor 1 receptor (CSF-1R) and tropomyosin receptor kinase A (TrkA) improves the antitumor efficacy of immune checkpoint blockade

Abstract Established tumors can escape immune responses by secreting the cytokine colony stimulating factor 1 (CSF-1), stimulating the proliferation and recruitment of immunosuppressive myeloid cells to the tumor microenvironment by binding to colony stimulating factor-1 receptor (CSF-1R). Additionally, the neurotrophin nerve growth factor (NGF) is a ligand for tropomyosin receptor kinase A (TrkA), which is over-expressed on multiple tumor types. Signaling through TrkA via the Akt and MAPK pathways regulates survival, proliferation and invasion of tumor cells. This invasion can occur around nerves, and perineural invasion (PNI) has emerged as a critical pathological feature of multiple malignancies, resulting in poor prognosis. PLX7486 is a novel orally bioavailable small molecule Trk and CSF-1R dual-inhibitor that is now being studied in Phase I clinical trials. We hypothesized that PLX7486 would synergize with immune checkpoint blockade to result in a greater antitumor effect, by targeting Trk signaling directly on cancer cells and by inhibiting the recruitment of immunosuppressive myeloid cells through CSF-1R, thus enabling an improved antitumor T cell response. We confirmed the expression of TrkA receptor on multiple murine cancer cell lines in vitro and exposed them to PLX7486, showing a direct cytotoxic effect with an IC50 of 5–8μM on most of the cell lines and an inhibition of AKT pathway signaling in MC38 cells. PLX7486 also had a direct cytotoxic effect on bone marrow-derived macrophages and the murine macrophage cell line RAW264.7 with an IC50 <1μM, while it had no effect on activated T cells in vitro. Combining PLX7486 and anti-CTLA-4 or anti-PD-1 in vivo in MC38 and B16F10 tumor models resulted in increased antitumor effects.

Enhanced Cancer Radiotherapy through Immunosuppressive Stromal Cell Destruction in Tumors

Radiotherapy kills cancer cells by causing DNA damage, and stimulates a systemic antitumor immune response by releasing tumor antigen and endogenous adjuvant within the tumor microenvironment. However, radiotherapy also induces the recruitment of immunosuppressive myeloid cells, which can interfere with the antitumor immune responses elicited by apoptotic tumor cells. We hypothesized that local delivery of vaccine following radiotherapy will lead to the priming of antigen-specific CTL immune responses and render immunosuppressive myeloid cells susceptible to killing by the activated CTLs. Using several antigenic systems, we tested whether intratumoral injection of antigenic peptide/protein in irradiated tumors would be able to prime CTLs as well as load myeloid cells with antigen, rendering them susceptible to antigen-specific CTL killing. We show that by combining radiotherapy and targeted antigenic peptide delivery to the tumor, the adjuvant effect generated by radiotherapy itself was sufficient to elicit the priming and expansion of antigen-specific CTLs, through the type I IFN-dependent pathway, leading to synergistic therapeutic antitumor effects compared with either treatment alone. In addition, using two different types of transgenic mice, we demonstrated that CTL-mediated killing of stromal cells in tumors by our approach is important for tumor control. Finally, we confirmed the efficacy of this approach in our preclinical model using two clinically tested therapeutic human papilloma virus (HPV) vaccines. These data serve as an important foundation for the future clinical translation of radiotherapy combined with a clinically tested therapeutic HPV vaccine for the control of HPV-associated cancers.

Pathological Mobilization and Activities of Dendritic Cells in Tumor-Bearing Hosts: Challenges and Opportunities for Immunotherapy of Cancer

A common characteristic of solid tumors is the pathological recruitment of immunosuppressive myeloid cells, which in certain tumors includes dendritic cells (DCs). DCs are of particular interest in the field of cancer immunotherapy because they induce potent and highly specific anti-tumor immune responses, particularly in the early phase of tumorigenesis. However, as tumors progress, these cells can be transformed into regulatory cells that contribute to an immunosuppressive microenvironment favoring tumor growth. Therefore, controlling DC phenotype has the potential to elicit effective anti-tumor responses while simultaneously weakening the tumor’s ability to protect itself from immune attack. This review focuses on the dual nature of DCs in the tumor microenvironment, the regulation of DC phenotype, and the prospect of modifying DCs in situ as a novel immunotherapeutic approach.

Immunosuppression in inflammatory melanoma: can it be resisted by adoptively transferred T cells?

Discovery of tumor antigen (TA) recognized by autologous T cells (TCs) in patients with melanoma has led to clinical protocols using either vaccination or adoptive transfer of TA-specific TCs. However, efficacy of these treatments has been hampered by inhibitory effects exerted on tumor-infiltrating TCs by tumor-intrinsic mediators or by recruitment of immunosuppressive cells. A mouse model of autochthonous melanoma recapitulates some aspects of inflammatory melanoma development in patients. These include a systemic Th2-/Th17-oriented chronic inflammation, recruitment of immunosuppressive myeloid cells and acquisition by tumor-infiltrating TCs of an 'exhausted' phenotype characterized by expression of multiple inhibitory receptors including programmed death-1, also expressed on patients' melanoma-infiltrating TCs. Rather than using extracellular blocking reagents to inhibitory surface molecules on TCs, we sought to dampen negative signaling exerted on them. Adoptively transferred TCs presenting increased cytokine receptor signaling due to expression of an active Stat5 transcription factor were efficient at inducing melanoma regression in the preclinical melanoma model. These transferred TCs thrived and retained expression of effector molecules in the melanoma microenvironment, defining a protocol endowing TCs with the ability to resist melanoma-induced immunosuppression.

Diabetes acceleration by cyclophosphamide in the non-obese diabetic mouse is associated with differentiation of immunosuppressive monocytes into immunostimulatory cells

Cyclophosphamide (CTX) was previously shown to induce the recruitment of immunosuppressive myeloid cells in mouse. In the non-obese diabetic (NOD) mouse, which develops spontaneously type I diabetes, CTX is widely known to accelerate the autoimmune process. Our data demonstrated that CTX actually did mobilize an immunosuppressive myeloid CD11b + Ly-6G − population in the NOD mouse spleen in addition to a well-identified neutrophil CD11b + Ly-6G + population. CD11b + Ly-6G − cells, in contrast with CD11b + Ly-6G + cells, were able to inhibit in vitro mitogen-induced syngeneic T cell proliferation. CD11b + Ly-6G − cells represented a heterogeneous population mainly made of CD31 hi cells and Ly-6C + monocytes. Only these last ones supported the immunosuppressive in vitro activity and resembled circulating inflammatory monocytes according to flow cytometry, cytology and RT-PCR data. Although CD11b + Ly-6G − Ly-6C + cells exhibited immunosuppressive function in vitro, they were not able to control the autoimmune response following CTX injection. Our data show that these CTX-induced immunosuppressive myeloid cells actually behaved as very plastic cells in vitro. Likewise, in the model of prediabetic NOD/SCID mice, CD11b + Ly-6G − Ly-6C + were able to differentiate into CD11c+ cells after i.v. injection. Herein, we described a new mechanism by which CTX might induce diabetes acceleration in the NOD mouse. In summary, recruited immunosuppressive cells might participate in the immunopotentiating effect of CTX on the autoimmune response by their further differentiation into immunostimulatory cells.