Blockade of tumor-derived colony-stimulating factor 1 (CSF1) promotes an immune-permissive tumor microenvironment

The macrophage colony-stimulating factor 1 (CSF1) is a chemokine essential for the survival, proliferation, and differentiation of mononuclear phagocytes from hemopoietic stem cells. In addition to its essential physiological role in normal tissues, the CSF1/CSF1 receptor axis is known to be overexpressed in many tumor types and associated with poor prognosis. High levels of CSF1 within the tumor microenvironment have been shown to recruit and reeducate macrophages to produce factors that promote tumor invasiveness and accelerate metastasis. In this study, we demonstrate, for the first time, that treating established syngeneic murine colon and breast carcinoma tumors with a CSF1R-blocking antibody also promotes the expansion of neoepitope-specific T cells. To assess the role of tumor-derived CSF1 in these model systems, we generated and characterized CSF1 CRISPR-Cas9 knockouts. Eliminating tumor-derived CSF1 results in decreased tumor growth and enhanced immunity against tumor-associated neoepitopes, potentially promoting an immune permissive tumor microenvironment in tumor-bearing mice. The combination of neoepitope vaccine with anti-PDL1 in the MC38 CSF1-/- tumor model significantly decreased tumor growth in vivo. Moreover, anti-CSF1R therapy combined with the adeno-TWIST1 vaccine resulted in tumor control, decreased metastasis, and a synergistic increase in CD8 T cell infiltration in 4T1 mammary tumors. Analysis of the tumor microenvironment demonstrated greater CD8 T cell infiltration and a reduction in tumor-associated macrophages following CSF1R inhibition in both tumor models. Our findings thus add to the therapeutic potential of CSF1 targeting agents by employing combinations with vaccines to modulate anti-neoepitope responses in the tumor microenvironment.

Fulvestrant increases the susceptibility of enzalutamide-resistant prostate cancer cells to NK-mediated lysis

BACKGROUND

Enzalutamide, a next-generation antiandrogen agent, is approved for the treatment of metastatic castration-resistant prostate cancer (CRPC). While enzalutamide has been shown to improve time to progression and extend overall survival in men with CRPC, the majority of patients ultimately develop resistance to treatment. Immunotherapy approaches have shown limited clinical benefit in this patient population; understanding resistance mechanisms could help develop novel and more effective treatments for CRPC. One of the mechanisms involved in tumor resistance to various therapeutics is tumor phenotypic plasticity, whereby carcinoma cells acquire mesenchymal features with or without the loss of classical epithelial characteristics. This work investigated a potential link between enzalutamide resistance, tumor phenotypic plasticity, and resistance to immune-mediated lysis in prostate cancer.

METHODS

Models of prostate cancer resistant to enzalutamide were established by long-term exposure of human prostate cancer cell lines to the drug in culture. Tumor cells were evaluated for phenotypic features in vitro and in vivo, as well as for sensitivity to immune effector cell-mediated cytotoxicity.

RESULTS

Resistance to enzalutamide was associated with gain of mesenchymal tumor features, upregulation of estrogen receptor expression, and significantly reduced tumor susceptibility to natural killer (NK)-mediated lysis, an effect that was associated with decreased tumor/NK cell conjugate formation with enzalutamide-resistant cells. Fulvestrant, a selective estrogen receptor degrader, restored the formation of target/NK cell conjugates and increased susceptibility to NK cell lysis in vitro. In vivo, fulvestrant demonstrated antitumor activity against enzalutamide-resistant cells, an effect that was associated with activation of NK cells.

CONCLUSION

NK cells are emerging as a promising therapeutic approach in prostate cancer. Modifying tumor plasticity via blockade of estrogen receptor with fulvestrant may offer an opportunity for immune intervention via NK cell-based approaches in enzalutamide-resistant CRPC.

Exploiting docetaxel-induced tumor cell necrosis with tumor targeted delivery of IL-12

There is strong evidence that chemotherapy can induce tumor necrosis which can be exploited for the targeted delivery of immuno-oncology agents into the tumor microenvironment (TME). We hypothesized that docetaxel, a chemotherapeutic agent that induces necrosis, in combination with the bifunctional molecule NHS-IL-12 (M9241), which delivers recombinant IL-12 through specific targeting of necrotic regions in the tumor, would provide a significant antitumor benefit in the poorly inflamed murine tumor model, EMT6 (breast), and in the moderately immune-infiltrated tumor model, MC38 (colorectal). Docetaxel, as monotherapy or in combination with NHS-IL-12, promoted tumor necrosis, leading to the improved accumulation and retention of NHS-IL-12 in the TME. Significant antitumor activity and prolonged survival were observed in cohorts receiving docetaxel and NHS-IL-12 combination therapy in both the MC38 and EMT6 murine models. The therapeutic effects were associated with increased tumor infiltrating lymphocytes and were dependent on CD8+ T cells. Transcriptomics of the TME of mice receiving the combination therapy revealed the upregulation of genes involving crosstalk between innate and adaptive immunity factors, as well as the downregulation of signatures of myeloid cells. In addition, docetaxel and NHS-IL-12 combination therapy effectively controlled tumor growth of PD-L1 wild-type and PD-L1 knockout MC38 in vivo, implying this combination could be applied in immune checkpoint refractory tumors, and/or tumors regardless of PD-L1 status. The data presented herein provide the rationale for the design of clinical studies employing this combination or similar combinations of agents.

Abstract 5085: Blockade of tumor derived CSF1 promotes an immune-permissive tumor microenvironment

The macrophage colony stimulating factor 1 (CSF1) is a chemokine essential for the survival, proliferation, and differentiation of especially mononuclear phagocytes, such as macrophages and monocytes. However, within the tumor microenvironment (TME), CSF1 regulates the production, survival, and recruitment of tumor associated macrophages (TAMs), further promoting a protumorigenic and immunosuppressive M2-like phenotype. Overexpression of CSF1 in breast, prostate, and ovarian cancers has been shown to promote tumorgenicity, invasiveness, and accelerate tumor metastasis. In this study, we demonstrate for the first time, that treating established murine MC38 colon and 4T1 breast carcinoma tumors with a CSF1R blocking antibody promotes the expansion of neoepitope-specific T cells. To assess the role of tumor derived CSF1 in these model systems, we generated and characterized CSF1 CRISPR-Cas9 knockouts. In both models, elimination of tumor-derived CSF1 results in a decreased tumor growth in both syngeneic and immune-compromised mice as compared to the parental cell lines. Inhibition of CSF1/CSF1R signaling axis generated enhanced immunity against 4T1 and MC38 tumor neoepitopes, potentially promoting an immune permissive TME in tumor bearing mice. Combination of a neoepitope targeting cancer vaccine with anti-PDL1 in the MC38 CSF1-/- tumor model significantly decreased tumor growth in vivo. Furthermore, combining CSF1R blockade with adeno-TWIST1 vaccine decreased tumor volume, lung metastasis, and synergistically increased in CD8 T cell infiltration in 4T1 mammary tumors. Analysis of the tumor microenvironment demonstrated increased infiltration in CD8 T cells accompanied by a reduction in tumor associated macrophages following CSF1R inhibition in both tumor models. Our findings confirm the therapeutic potential of combining CSF1 targeting agents with vaccine agents to further modulate anti-tumor immune responses in the tumor microenvironment.

Citation Format: Maria Del Mar Maldonado, Duane H. Hamilton, Jeffrey Schlom. Blockade of tumor derived CSF1 promotes an immune-permissive tumor microenvironment. [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 5085.

An Interleukin-15 Superagonist Enables Antitumor Efficacy of Natural Killer Cells Against All Molecular Variants of SCLC

INTRODUCTION

SCLC is a highly aggressive tumor with a 5-year survival rate of less than 6%. A heterogeneous disease, SCLC is classified into four subtypes that include tumors with neuroendocrine and non-neuroendocrine features. Immune checkpoint blockade has been recently added for the frontline treatment of SCLC; however, this therapy has only led to modest clinical improvements. The lack of clinical benefit in a cancer type known to have a high tumor mutational burden has been attributed to poor T-cell infiltration and low expression of MHC-class I in most SCLC tumors. In an attempt to devise a more effective immunotherapeutic regimen, this study investigated an alternate approach on the basis of the use of the clinical-stage interleukin-15 superagonist, N-803.

METHODS

Preclinical models of SCLC spanning all molecular subtypes were used to evaluate the susceptibility of SCLC to natural killer (NK)-mediated lysis in vitro, including NK cells activated by N-803. Antitumor activity of N-803 was evaluated in vivo with a xenograft model of SCLC.

RESULTS

In vitro and in vivo data revealed differences in susceptibility of SCLC subtypes to lysis by NK cells and that NK cells activated by N-803 effectively lyse SCLC tumor cells across all variant subtypes, regardless of their expression of MHC-class I.

CONCLUSIONS

These findings highlight the potential of a novel immune-based intervention using a cytokine-based therapeutic option for the treatment of SCLC. We hypothesize that N-803 may provide benefit to most patients with SCLC, including those with immunologically cold tumors lacking MHC expression.

Identification and validation of expressed HLA-binding breast cancer neoepitopes for potential use in individualized cancer therapy

Background

Therapeutic regimens designed to augment the immunological response of a patient with breast cancer (BC) to tumor tissue are critically informed by tumor mutational burden and the antigenicity of expressed neoepitopes. Herein we describe a neoepitope and cognate neoepitope-reactive T-cell identification and validation program that supports the development of next-generation immunotherapies.

Methods

Using GPS Cancer, NantOmics research, and The Cancer Genome Atlas databases, we developed a novel bioinformatic-based approach which assesses mutational load, neoepitope expression, human leukocyte antigen (HLA)-binding prediction, and in vitro confirmation of T-cell recognition to preferentially identify targetable neoepitopes. This program was validated by application to a BC cell line and confirmed using tumor biopsies from two patients with BC enrolled in the Tumor-Infiltrating Lymphocytes and Genomics (TILGen) study.

Results

The antigenicity and HLA-A2 restriction of the BC cell line predicted neoepitopes were determined by reactivity of T cells from HLA-A2-expressing healthy donors. For the TILGen subjects, tumor-infiltrating lymphocytes (TILs) recognized the predicted neoepitopes both as peptides and on retroviral expression in HLA-matched Epstein-Barr virus–lymphoblastoid cell line and BC cell line MCF-7 cells; PCR clonotyping revealed the presence of T cells in the periphery with T-cell receptors for the predicted neoepitopes. These high-avidity immune responses were polyclonal, mutation-specific and restricted to either HLA class I or II. Interestingly, we observed the persistence and expansion of polyclonal T-cell responses following neoadjuvant chemotherapy.

Conclusions

We demonstrate our neoepitope prediction program allows for the successful identification of neoepitopes targeted by TILs in patients with BC, providing a means to identify tumor-specific immunogenic targets for individualized treatment, including vaccines or adoptively transferred cellular therapies.

Vaccine Increases the Diversity and Activation of Intratumoral T Cells in the Context of Combination Immunotherapy

Resistance to immune checkpoint blockade therapy has spurred the development of novel combinations of drugs tailored to specific cancer types, including non-inflamed tumors with low T-cell infiltration. Cancer vaccines can potentially be utilized as part of these combination immunotherapies to enhance antitumor efficacy through the expansion of tumor-reactive T cells. Utilizing murine models of colon and mammary carcinoma, here we investigated the effect of adding a recombinant adenovirus-based vaccine targeting tumor-associated antigens with an IL-15 super agonist adjuvant to a multimodal regimen consisting of a bifunctional anti-PD-L1/TGF-βRII agent along with a CXCR1/2 inhibitor. We demonstrate that the addition of vaccine induced a greater tumor infiltration with T cells highly positive for markers of proliferation and cytotoxicity. In addition to this enhancement of cytotoxic T cells, combination therapy showed a restructured tumor microenvironment with reduced T_regs and CD11b⁺Ly6G⁺ myeloid cells. Tumor-infiltrating immune cells exhibited an upregulation of gene signatures characteristic of a Th1 response and presented with a more diverse T-cell receptor (TCR) repertoire. These results provide the rationale for the addition of vaccine-to-immune checkpoint blockade-based therapies being tested in the clinic.

An immunotherapeutic intervention against tumor progression: Targeting a driver of the epithelial-to-mesenchymal transition

Targeting the epithelial-to-mesenchymal transition (EMT) is emerging as a novel intervention against tumor progression and metastatic dissemination, as well as the resistance to chemo- and radiotherapy displayed by multiple carcinomas. We have recently developed an immunotherapeutic approach to target a major driver of EMT, the T-box transcription factor T (also known as brachyury). This therapeutic paradigm is currently being tested in patients with advanced carcinomas in the context of a Phase I clinical trial.

Combination therapies utilizing neoepitope-targeted vaccines

Clinical successes have been achieved with checkpoint blockade therapy, which facilitates the function of T cells recognizing tumor-specific mutations known as neoepitopes. It is a reasonable hypothesis that therapeutic cancer vaccines targeting neoepitopes uniquely expressed by a patient’s tumor would prove to be an effective therapeutic strategy. With the advent of high-throughput next generation sequencing, it is now possible to rapidly identify these tumor-specific mutations and produce therapeutic vaccines targeting these patient-specific neoepitopes. However, initial reports suggest that when used as a monotherapy, neoepitope-targeted vaccines are not always sufficient to induce clinical responses in some patients. Therefore, research has now turned to investigating neoepitope vaccines in combination with other cancer therapies, both immune and non-immune, to improve their clinical efficacies.

Abstract PR20: A novel combination immunotherapy with a vaccine targeting tumor neoepitopes that mediates immune cascade in murine tumor models

Clinical successes utilizing checkpoint inhibitors demonstrate the potential of immune-based therapies for the treatment of cancer. Research suggests that these successes are a result of T cells recognizing nonsynonymous mutations uniquely expressed by a patient’s tumor. The advent of comparative tumor-normal DNA sequencing and tumor RNA sequencing for accurate prediction of presented somatic mutations has made it possible to rapidly identify these neoepitopes, allowing for the development of personalized cancer vaccines. However, such vaccines are often ineffective due to the immunosuppressive nature of the tumor microenvironment, and their clinical efficacies would be improved when used in an orchestrated combination approach with additional immune-oncology agents. In the present study, we investigated the combination of three immune-oncology agents, each targeting a unique mechanism of immune therapy, with a vaccine targeting tumor neoepitopes. We combined a neoepitope vaccine, delivered as a peptide or via a novel E2b-deleted adenovirus vehicle, with N-IL15 (previously called ALT-803), an IL-15 superagonist, to enhance the development of antigen-specific immunity; NHS-IL12, a tumor-targeting IL-12 molecule, to promote the maintenance and expansion of T cells within the tumor microenvironment; and PD-L1 blockade to decrease immune cell exhaustion within the tumor microenvironment. This combination therapy resulted in the regression of established tumors, which associated with the generation of robust immunity against neoepitopes contained in the vaccine. It also showed evidence of inducing a neoepitope cascade by causing development of T-cell responses to neoepitopes expressed by the tumor but not contained within the vaccine. This report is the first demonstration of an E2b-deleted adenovirus neoantigen vaccine generating robust immunity. Together, this study demonstrates the importance of a multifaceted, orchestrated treatment regimen to promote the generation of effective antitumor immunity.

This abstract is also being presented as Poster A18.

Citation Format: Karin L. Lee, Claudia Palena, John Lee, Kayvan Niazi, Andrew Nguyen, Frank Jones, Shahrooz Rabizadeh, Patrick Soon-Shiong, Jeffrey Schlom, Duane H. Hamilton. A novel combination immunotherapy with a vaccine targeting tumor neoepitopes that mediates immune cascade in murine tumor models [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr PR20.

Abstract B29: The importance of epitope spreading in the generation of effective antitumor immunity in mice treated with combination immunotherapy

Recent clinical successes of PD-1/L1 and CTLA-4 blockade have demonstrated the potential of immunotherapies for the treatment of cancer. Research suggests the clinical efficacy of these checkpoint blockade therapies requires the presence of tumor-reactive T cells prior to therapy. It is thought that these tumor-reactive T cells primarily recognize nonsynonymous mutations (neoepitopes) uniquely expressed by a patient’s tumor. Unfortunately, at present the majority of patients fail to respond to checkpoint blockade, and it is hypothesized that one can improve their efficacy by combining them with vaccines targeting neoepitopes. Using the MC38 murine colon cancer model, we previously showed that an effective antitumor immunity could be generated when combining either a peptide or recombinant adenoviral-based vaccine targeting neoepitopes with three rationally selected immune-oncology agents. We utilized an IL-15 superagonist (N-803) to promote the generation and expansion of T cells and a tumor-targeted IL12 (NHS-IL12) and PD-L1 blockade to facilitate T-cell expansion and function within the tumor microenvironment. This multifaceted treatment regimen was effective at inducing tumor clearance in the majority of animals treated. In the present study, we examine the immune response in animals that fail to respond to our treatment regimen. By analyzing the spread of immunity to neoepitopes expressed by the MC38 tumor, but not contained within the vaccine, we were able to correlate treatment failures to less diversity in the antitumor immune response. To examine this observation more closely, tumor-bearing mice were treated with different combinations of neoepitope vaccine, N-803, PD-L1 blockade, and NHS-IL12, to ascertain which components of the combination therapy facilitated epitope spreading. We also examined which cell populations were able to cooperate with tumor-reactive CD8+ T cells to promote and/or inhibit epitope spread. Our observations demonstrate the importance of a diverse antitumor immune response and offers insights on how one might increase the diversity of the antitumor immune response following treatment with immune-oncology agents. These studies were performed in collaboration with NantOmics, NantBio and ImmunityBio, and EMD Serono as a part of Collaborative Research and Development Agreements (CRADA) with the NCI.

Citation Format: Karin L. Lee, Claudia Palena, Jeffrey Schlom, Duane H. Hamilton. The importance of epitope spreading in the generation of effective antitumor immunity in mice treated with combination immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B29.

Abstract B43: Simultaneous inhibition of CXCR1/CXCR2, TGF-β, and PD-L1 overcomes immune resistance driven by tumor plasticity

The occurrence of phenotypic plasticity in carcinomas, which results in the acquisition of mesenchymal features by epithelial cancer cells, associates with a poor prognosis and has been described as a mechanism of primary resistance and failure to treatment with checkpoint blockade immunotherapy targeting the PD-1/PD-L1 pathway. IL-8 and TGF-β are two of the factors that mediate phenotypic plasticity in epithelial tumors to promote an immune-suppressive microenvironment. Here we report on an immunotherapy approach aimed at overcoming escape mechanisms mediated by IL-8 and TGF-β accumulation in the tumor microenvironment via the use of two clinical-stage agents: SX-682, a dual CXCR1/2 small-molecule inhibitor, with the bifunctional anti-PD-L1/TGFβRII agent, bintrafusp alfa (M7824) that simultaneously blocks PD-L1 while trapping soluble TGF-β. We demonstrate that the concurrent inhibitions of CXCR1/CXCR2, TGF-β, and PD-L1 signaling synergize to reduce mesenchymal tumor features in murine models of breast and lung cancer, and to markedly increase expression of tumor epithelial E-cadherin while reducing infiltration with suppressive granulocytic myeloid-derived suppressor cells (G-MDSC), significantly enhancing CD4+ and CD8+ T-cell infiltration and activation in tumors, and leading to improved antitumor activity. This combination approach was effective in tumor models with varying immune cell infiltrates, degrees of plasticity, and responses to immunotherapy. The results of these studies provide the rationale for the future evaluation of this multimodal therapy in the clinic.

Citation Format: Lucas A. Horn, Jeffrey Riskin, Heidi A. Hempel, Hanne Lind, Kristen Fousek, Duane H. Hamilton, Kristen K. McCampbell, Jeffrey Schlom, Claudia Palena. Simultaneous inhibition of CXCR1/CXCR2, TGF-β, and PD-L1 overcomes immune resistance driven by tumor plasticity [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr B43.

Simultaneous inhibition of CXCR1/2, TGF-β, and PD-L1 remodels the tumor and its microenvironment to drive antitumor immunity

BACKGROUND

Despite the success of immune checkpoint blockade therapy in the treatment of certain cancer types, only a small percentage of patients with solid malignancies achieve a durable response. Consequently, there is a need to develop novel approaches that could overcome mechanisms of tumor resistance to checkpoint inhibition. Emerging evidence has implicated the phenomenon of cancer plasticity or acquisition of mesenchymal features by epithelial tumor cells, as an immune resistance mechanism.

METHODS

Two soluble factors that mediate tumor cell plasticity in the context of epithelial-mesenchymal transition are interleukin 8 (IL-8) and transforming growth factor beta (TGF-β). In an attempt to overcome escape mechanisms mediated by these cytokines, here we investigated the use of a small molecule inhibitor of the IL-8 receptors CXCR1/2, and a bifunctional agent that simultaneously blocks programmed death ligand 1 (PD-L1) and traps soluble TGF-β.

RESULTS

We demonstrate that simultaneous inhibition of CXCR1/2, TGF-β, and PD-L1 signaling synergizes to reduce mesenchymal tumor features in murine models of breast and lung cancer, and to markedly increase expression of tumor epithelial E-cadherin while reducing infiltration with suppressive granulocytic myeloid-derived suppressor cells, significantly enhancing T-cell infiltration and activation in tumors, and leading to improved antitumor activity.

CONCLUSIONS

This study highlights the potential benefit of combined blockade of CXCR1/2 and TGF-β signaling for modulation of tumor plasticity and potential enhancement of tumor responses to PD-L1 blockade. The data provide rationale for the evaluation of this novel approach in the clinic.

Cooperative Immune-Mediated Mechanisms of the HDAC Inhibitor Entinostat, an IL15 Superagonist, and a Cancer Vaccine Effectively Synergize as a Novel Cancer Therapy

PURPOSE

Immunotherapy has demonstrated clinical efficacy in subsets of patients with solid carcinomas. Multimodal therapies using agents that can affect different arms of the immune system and/or tumor microenvironment (TME) might increase clinical responses.

EXPERIMENTAL DESIGN

We demonstrate that entinostat, a class I histone deacetylase inhibitor, enhances the antitumor efficacy of the IL15 superagonist N-803 plus vaccine in 4T1 triple-negative breast and MC38-CEA colon murine carcinoma models. A comprehensive immune and gene-expression analysis was performed in the periphery and/or TME of MC38-CEA tumor-bearing mice.

RESULTS

Although N-803 plus vaccine induced peripheral CD8⁺ T-cell activation and cytokine production, there was no reduction in tumor burden and poor tumor infiltration of CD8⁺ T cells with minimal levels of granzyme B. For the first time, we demonstrate that the addition of entinostat to N-803 plus vaccine promoted significant tumor control, correlating with increased expression of genes associated with tumor inflammation, enhanced infiltration of activated CD8⁺ T cells with maximal granzyme B, T-cell responses to multiple tumor-associated antigens, increased serum IFNγ, reduction of regulatory T cells in the TME, and decreased expression of the checkpoint V-domain Ig suppressor of T-cell activation (VISTA) on multiple immune subsets.

CONCLUSIONS

Collectively, these data demonstrate that the synergistic combination of entinostat, N-803, and vaccine elicits potent antitumor activity by generating a more inflamed TME. These findings thus form the rationale for the use of this combination of agents for patients harboring poorly or noninflamed solid carcinomas.

Efficient Tumor Clearance and Diversified Immunity through Neoepitope Vaccines and Combinatorial Immunotherapy

Progressive tumor growth is associated with deficits in the immunity generated against tumor antigens. Vaccines targeting tumor neoepitopes have the potential to address qualitative defects; however, additional mechanisms of immune failure may underlie tumor progression. In such cases, patients would benefit from additional immune-oncology agents targeting potential mechanisms of immune failure. This study explores the identification of neoepitopes in the MC38 colon carcinoma model by comparison of tumor to normal DNA and tumor RNA sequencing technology, as well as neoepitope delivery by both peptide- and adenovirus-based vaccination strategies. To improve antitumor efficacies, we combined the vaccine with a group of rationally selected immune-oncology agents. We utilized an IL15 superagonist to enhance the development of antigen-specific immunity initiated by the neoepitope vaccine, PD-L1 blockade to reduce tumor immunosuppression, and a tumor-targeted IL12 molecule to facilitate T-cell function within the tumor microenvironment. Analysis of tumor-infiltrating leukocytes demonstrated this multifaceted treatment regimen was required to promote the influx of CD8⁺ T cells and enhance the expression of transcripts relating to T-cell activation/effector function. Tumor-targeted IL12 resulted in a marked increase in clonality of T-cell repertoire infiltrating the tumor, which when sculpted with the addition of either a peptide or adenoviral neoepitope vaccine promoted efficient tumor clearance. In addition, the neoepitope vaccine induced the spread of immunity to neoepitopes expressed by the tumor but not contained within the vaccine. These results demonstrate the importance of combining neoepitope-targeting vaccines with a multifaceted treatment regimen to generate effective antitumor immunity.

Abstract B82: Identification of tumor neoantigens for combination therapy in murine tumor models

The adoption of anti-CTLA-4 and anti-PD-1/PD-L1 blockade has dramatically changed the treatment approaches in multiple cancer types, and has demonstrated the power of the immune system to control the outgrowth of neoplastic lesions. Accumulating evidence suggests these successes are mediated by T cells targeting nonsynonymous mutations unique to the patient’s tumor. When used in combination with checkpoint inhibition, or other standard of care treatment modalities, vaccines targeting tumor neoantigens have the potential to greatly enhance patient survival. Recent advances in DNA/RNA sequencing and bioinformatic analysis have made it possible to rapidly identify nonsynonymous mutations being expressed in patient tumors. As the number of nonsynonymous mutations detected in patient samples can range from less than 10 to several thousand, it is necessary to develop strategies to identify and rank neoantigens with a greater probability of being immunogenic and mediating regression of established tumors.

In the present study, we harvested tumors from mice bearing syngeneic tumors, and performed DNA/RNA sequencing to identify nonsynonymous mutations to use as tumor specific neoantigens. These potential neoantigens were ranked based upon their proposed in-silico MHC binding affinity, and the relative abundance of each transcript as determined by RNA-seq. Top ranking 9-mer neoantigens peptides were synthesized and evaluated. We assessed neoantigens for their ability to bind MHC in vitro, and expand antigen-specific T cells in vivo.

To further augment the immunogenicity of our neoantigen 9-mer peptides, we used them in combination with an IL-15 super-agonist (ALT-803) and an anti-PD-L1 antibody. When used in combination with these immune-modulators, we observed a dramatic increase in the magnitude of the immune response generated against our neoantigens, which associated with increased tumor therapy. This study provides the rational for the combination of neoantigen vaccines with immune modulators to slow tumor growth and extend survival.

Citation Format: Karin L. Lee, Andrew T. Nguyen, Steven C. Benz, Shahrooz Rabizadeh, James W. Hodge, Claudia Palena, Jeffrey Schlom, Duane H. Hamilton. Identification of tumor neoantigens for combination therapy in murine tumor models [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B82.

Brachyury-YAP Regulatory Axis Drives Stemness and Growth in Cancer

Molecular factors that define stem cell identity have recently emerged as oncogenic drivers. For instance, brachyury, a key developmental transcriptional factor, is also implicated in carcinogenesis, most notably of chordoma, through mechanisms that remain elusive. Here, we show that brachyury is a crucial regulator of stemness in chordoma and in more common aggressive cancers. Furthermore, this effect of brachyury is mediated by control of synthesis and stability of Yes-associated protein (YAP), a key regulator of tissue growth and homeostasis, providing an unexpected mechanism of control of YAP expression. We further demonstrate that the brachyury-YAP regulatory pathway is associated with tumor aggressiveness. These results elucidate a mechanism of controlling both tumor stemness and aggressiveness through regulatory coupling of two developmental factors.

Loss of the Cyclin-Dependent Kinase Inhibitor 1 in the Context of Brachyury-Mediated Phenotypic Plasticity Drives Tumor Resistance to Immune Attack

The acquisition of mesenchymal features by carcinoma cells is now recognized as a driver of metastasis and tumor resistance to a range of anticancer therapeutics, including chemotherapy, radiation, and certain small-molecule targeted therapies. With the recent successful implementation of immunotherapies for the treatment of various types of cancer, there is growing interest in understanding whether an immunological approach could be effective at eradicating carcinoma cells bearing mesenchymal features. Recent studies, however, demonstrated that carcinoma cells that have acquired mesenchymal features may also exhibit decreased susceptibility to lysis mediated by immune effector cells, including antigen-specific CD8⁺ T cells, innate natural killer (NK), and lymphokine-activated killer (LAK) cells. Here, we investigated the mechanism involved in the immune resistance of carcinoma cells that express very high levels of the transcription factor brachyury, a molecule previously shown to drive the acquisition of mesenchymal features by carcinoma cells. Our results demonstrate that very high levels of brachyury expression drive the loss of the cyclin-dependent kinase inhibitor 1 (p21CIP1, p21), an event that results in decreased tumor susceptibility to immune-mediated lysis. We show here that reconstitution of p21 expression markedly increases the lysis of brachyury-high tumor cells mediated by antigen-specific CD8⁺ T cells, NK, and LAK cells, TNF-related apoptosis-inducing ligand, and chemotherapy. Several reports have now demonstrated a role for p21 loss in cancer as an inducer of the epithelial–mesenchymal transition. The results from the present study situate p21 as a central player in many of the aspects of the phenomenon of brachyury-mediated mesenchymalization of carcinomas, including resistance to chemotherapy and immune-mediated cytotoxicity. We also demonstrate here that the defects in tumor cell death described in association with very high levels of brachyury could be alleviated via the use of a WEE1 inhibitor. Several vaccine platforms targeting brachyury have been developed and are undergoing clinical evaluation. These studies provide further rationale for the use of WEE1 inhibition in combination with brachyury-based immunotherapeutic approaches.

Phase I Study of a Poxviral TRICOM-Based Vaccine Directed Against the Transcription Factor Brachyury

Purpose: The transcription factor brachyury has been shown in preclinical studies to be a driver of the epithelial-to-mesenchymal transition (EMT) and resistance to therapy of human tumor cells. This study describes the characterization of a Modified Vaccinia Ankara (MVA) vector-based vaccine expressing the transgenes for brachyury and three human costimulatory molecules (B7.1, ICAM-1, and LFA-3, designated TRICOM) and a phase I study with this vaccine.Experimental Design: Human dendritic cells (DC) were infected with MVA-brachyury-TRICOM to define their ability to activate brachyury-specific T cells. A dose-escalation phase I study (NCT02179515) was conducted in advanced cancer patients (n = 38) to define safety and to identify brachyury-specific T-cell responses.Results: MVA-brachyury-TRICOM-infected human DCs activated CD8⁺ and CD4⁺ T cells specific against the self-antigen brachyury in vitro No dose-limiting toxicities were observed due to vaccine in cancer patients at any of the three dose levels. One transient grade 3 adverse event (AE) possibly related to vaccine (diarrhea) resolved without intervention and did not recur with subsequent vaccine. All other AEs related to vaccine were transient and ≤grade 2. Brachyury-specific T-cell responses were observed at all dose levels and in most patients.Conclusions: The MVA-brachyury-TRICOM vaccine directed against a transcription factor known to mediate EMT can be administered safely in patients with advanced cancer and can activate brachyury-specific T cells in vitro and in patients. Further studies of this vaccine in combination therapies are warranted and planned. Clin Cancer Res; 23(22); 6833-45. ©2017 AACR.

Abstract B64: A high-throughput screen identifies fulvestrant as an enhancer of immune-mediated cytotoxicity of mesenchymal-like lung cancer cells

The phenomenon of epithelial-mesenchymal transition (EMT) is a phenotypic switch that allows epithelial tumor cells to acquire features of mesenchymal cells, including the ability to migrate and invade and, therefore, to disseminate from the primary site. In addition to promoting tumor dissemination, various reports have demonstrated that tumor EMT also associates with the acquisition of resistance to the cytotoxic effects of chemotherapy, radiation, and some targeted therapies. In the present report we have utilized a quantitative high-throughput screening of a pharmaceutical collection of more than 2000 compounds to identify FDA-approved drugs capable of augmenting the sensitivity of mensenchymal-like lung cancer cells to immune-mediated lysis. Using this approach we have identified the estrogen receptor antagonist fulvestrant as capable of rendering mesenchymal-like lung cancer cells more susceptible to the cytotoxic effects of natural killer or antigen-specific T cells and chemotherapy. Fulvestrant-treatment of human lung carcinoma cell lines, both in vivo and in vitro, was associated with a reduction of mesenchymal features. In silico analysis of publicly available gene expression datasets revealed a novel association between the expression of mesenchymal-associated features and the expression of estrogen receptor alpha in lung adenocarcinoma patients. Although the potential role of estrogen signaling in lung cancer remains controversial, this study supports a positive association between active estrogen signaling and the promotion of a mesenchymal phenotype in lung cancer. The findings from this study form the rationale for future combinations of fulvestrant and immune-mediated therapies in the treatment of advanced lung cancer.

Citation Format: Duane H. Hamilton, Lesley Mathews-Griner, Jonathan M. Keller, Xin Hu, Noel Southall, Juan Marugan, Justin M. David, Ferrer Ferrer, Jeffrey Schlom, Claudia Palena. A high-throughput screen identifies fulvestrant as an enhancer of immune-mediated cytotoxicity of mesenchymal-like lung cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr B64.

Development of Cancer Vaccines Targeting Brachyury, a Transcription Factor Associated with Tumor Epithelial-Mesenchymal Transition

Epithelial-mesenchymal transition (EMT) is recognized as a relevant process during the progression of carcinomas towards metastatic disease. Epithelial cancer cells undergoing an EMT program may acquire mesenchymal features, motility, invasiveness, and resistance to a variety of anticancer therapeutics. Preventing or reverting the EMT process in carcinomas has the potential to minimize tumor dissemination and the emergence of therapeutic resistance. One of the strategies currently under investigation to target tumor cells undergoing EMT is the generation of a sustained immune response directed against an essential molecular driver of the process. This review focuses on the current development of immune-mediated anticancer interventions aimed at targeting a transcription factor, brachyury, associated with human tumor EMT. Also presented here is a summary of recent studies demonstrating a role for EMT in tumor resistance to immune effector cytotoxicity, and the study of novel strategies aimed at reverting the EMT to be used in combination with immune-mediated anticancer interventions.

Brachyury, a vaccine target, is overexpressed in triple-negative breast cancer

Patients diagnosed with triple-negative breast cancer (TNBC) have a high rate of tumor metastasis and a poor prognosis. The treatment option for these patients is currently chemotherapy, which results in very low response rates. Strategies that exploit the immune system for the treatment of cancer have now shown the ability to improve survival in several tumor types. Identifying potential targets for immune therapeutic interventions is an important step in developing novel treatments for TNBC. In this study, in silico analysis of publicly available datasets and immunohistochemical analysis of primary and metastatic tumor biopsies from TNBC patients were conducted to evaluate the expression of the transcription factor brachyury, which is a driver of tumor metastasis and resistance and a target for cancer vaccine approaches. Analysis of breast cancer datasets demonstrated a predominant expression of brachyury mRNA in TNBC and in basal vs luminal or HER2 molecular breast cancer subtypes. At the protein level, variable levels of brachyury expression were detected both in primary and metastatic TNBC lesions. A strong association was observed between nuclear brachyury protein expression and the stage of disease, with nuclear brachyury being more predominant in metastatic vs primary tumors. Survival analysis also demonstrated an association between high levels of brachyury in the primary tumor and poor prognosis. Two brachyury-targeting cancer vaccines are currently undergoing clinical evaluation; the data presented here provide rationale for using brachyury-targeting immunotherapy approaches for the treatment of TNBC.

The IL-8/IL-8R Axis: A Double Agent in Tumor Immune Resistance

Interleukin-8 (IL-8, CXCL8) is a pro-inflammatory chemokine produced by various cell types to recruit leukocytes to sites of infection or tissue injury. Acquisition of IL-8 and/or its receptors CXCR1 and CXCR2 are known to be a relatively common occurrence during tumor progression. Emerging research now indicates that paracrine signaling by tumor-derived IL-8 promotes the trafficking of neutrophils and myeloid-derived suppressor cells (MDSCs) into the tumor microenvironment, which have the ability to dampen anti-tumor immune responses. Furthermore, recent studies have also shown that IL-8 produced by the tumor mass can induce tumor cells to undergo the transdifferentiation process epithelial-to-mesenchymal transition (EMT) in which tumor cells shed their epithelial characteristics and acquire mesenchymal characteristics. EMT can increase metastatic dissemination, stemness, and intrinsic resistance, including to killing by cytotoxic immune cells. This review highlights the dual potential roles that the inflammatory cytokine IL-8 plays in promoting tumor resistance by enhancing the immunosuppressive microenvironment and activating EMT, and then discusses the potential for targeting the IL-8/IL-8 receptor axis to combat these various resistance mechanisms.

Targeting Estrogen Receptor Signaling with Fulvestrant Enhances Immune and Chemotherapy-Mediated Cytotoxicity of Human Lung Cancer

PURPOSE

The conversion of tumor cells from an epithelial to a mesenchymal-like phenotype, via a process designated as the epithelial-mesenchymal transition (EMT), is known to mediate tumor resistance to a variety of cell death inducers, including cytotoxic effector immune cells. The goal of this study was to identify and potentially repurpose FDA-approved compounds capable of reducing mesenchymal features of human lung carcinoma cells, which could be used in combination with immunotherapies or chemotherapeutic strategies to improve clinical responses.

EXPERIMENTAL DESIGN

In the current report, we have utilized a quantitative high-throughput screening (qHTS) of a pharmaceutical collection of more than 2,000 compounds to identify clinically approved drugs capable of augmenting the sensitivity of mesenchymal-like, lung cancer cells to immune- and chemotherapy-mediated lysis, both in vitro and in vivo RESULTS: The estrogen receptor antagonist fulvestrant was shown to reduce mesenchymal features of lung carcinoma cells, resulting in tumor sensitization to the cytotoxic effect of antigen-specific T cells, natural killer (NK) effector cells, and chemotherapy both in vivo and in vitro CONCLUSIONS: To our knowledge, this is the first report defining a potential role for estrogenic signaling in promoting tumor resistance to immune-mediated cytotoxicity and chemotherapy in lung cancer. Our data demonstrate a robust association between the acquisition of mesenchymal attributes, therapeutic resistance of lung carcinoma cells, and the expression of estrogen receptor 1 (ESR1), supporting further investigations on the role of estrogen signaling in lung cancer progression via the induction of EMT. Clin Cancer Res; 22(24); 6204-16. ©2016 AACR.

Aberrant expression of the embryonic transcription factor brachyury in human tumors detected with a novel rabbit monoclonal antibody

The embryonic transcription factor brachyury is overexpressed in a variety of human tumors, including lung, breast, colon and prostate carcinomas, chordomas and hemangioblastomas. In human carcinoma cells, overexpression of brachyury associates with the occurrence of the phenomenon of epithelial-mesenchymal transition (EMT), acquisition of metastatic propensity and resistance to a variety of anti-cancer therapeutics. Brachyury is preferentially expressed in human tumors vs. normal adult tissues, and high levels of this molecule associate with poor prognosis in patients with lung, colon and prostate carcinomas, and in breast cancer patients treated with adjuvant tamoxifen. Brachyury is immunogenic in humans and vaccines against this novel oncotarget are currently undergoing clinical investigation. While our group and others have employed various anti-brachyury antibodies to interrogate the above findings, we report here on the development and thorough characterization of a novel rabbit monoclonal antibody (MAb 54-1) that reacts with distinct high affinity and specificity with human brachyury. MAb 54-1 was successfully used in ELISA, western blot, immunofluorescence and immunohistochemistry assays to evaluate expression of brachyury in various human tumor cell lines and tissues. We propose the use of this antibody to assist in research studies of EMT and in prognostic studies for a range of human tumors.

MUC1 upregulation promotes immune resistance in tumor cells undergoing brachyury-mediated epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a molecular and cellular program in which epithelial cells lose their well-differentiated phenotype and adopt mesenchymal characteristics. This process, which occurs naturally during embryogenesis, has also been shown to be associated with cancer progression and with tumor recurrence following conventional therapies. Brachyury is a transcription factor that mediates EMT during development, and is aberrantly expressed in various human cancers where it promotes tumor cell EMT, metastatic dissemination, and resistance to conventional therapies. We have recently shown that very high expression of brachyury can protect tumor cells against immune cell-mediated cytotoxicity. In seeking to elucidate mechanisms of immunotherapy resistance, we have discovered a novel positive association between brachyury and mucin-1 (MUC1). MUC1 is overexpressed in the majority of carcinomas, and it has been shown to mediate oncogenic signaling and confer resistance to genotoxic agents. We found that MUC1 is concomitantly upregulated in tumor cell lines that highly express brachyury due to an enhancement of MUC1 mRNA stability. Analysis of patient lung tumor tissues also identified a positive association between these two proteins in the majority of samples. Inhibition of MUC1 by siRNA-based gene silencing markedly enhanced the susceptibility of brachyury-expressing cancer cells to killing by tumor necrosis-related apoptosis-inducing ligand (TRAIL) and to perforin/granzyme-dependent lysis by immune cytotoxic cells. These studies confirm a protective role for MUC1 in brachyury-expressing cancer cells, and suggest that inhibition of MUC1 can restore the susceptibility of mesenchymal-like cancer cells to immune attack.

Abstract CN04-01: Targeting the epithelial-mesenchymal transition via brachyury-based cancer vaccines

Carcinoma cells undergo profound phenotypic changes during progression towards metastasis. One such phenotypic modulation is the epithelial-mesenchymal transition (EMT), an embryonically relevant process that can be reactivated in tumor cells, resulting in the acquisition of metastatic propensity, stem-like cell properties and resistance to a variety of anti-cancer therapies, including chemotherapy, radiation and some small molecule targeted therapies. Targeting of EMT is now emerging as a novel intervention against tumor progression. Brachyury, a transcription factor of the T-box family, is a driver of the phenomenon of EMT in human carcinomas. High levels of brachyury have been demonstrated in several human tumors, including chordoma, hemangioblastoma, and a range of human carcinomas such as lung, breast, colon and prostate, while brachyury is absent in the majority of adult normal tissues. In preclinical studies, brachyury has been shown to induce expression of molecules associated with the mesenchymal phenotype in carcinoma cells, to promote cell motility and invasiveness in vitro, and to favor metastatic dissemination in xenograft models. In addition to its role in tumor EMT, several studies have now also shown that the expression of brachyury is a predictor of poor prognosis in lung, breast, hepatocellular and prostate cancer, and it has been recently suggested to play a predominant role in triple negative vs. non-triple negative breast tumors. We propose the use of cancer vaccines that target brachyury as a strategy to directly eradicate tumor cells undergoing the phenomenon of EMT. Brachyury fulfills two major requirements to be used as a target for vaccine approaches: (a) is a highly tumor restricted molecule, and (b) is highly immunogenic, as demonstrated by the ability to expand brachyury-specific cytotoxic T lymphocytes from the blood of cancer patients which, in turn, can lyse tumor cells that express the brachyury protein. Based on these observations, our laboratory has collaboratively developed two brachyury-based cancer vaccines that are currently undergoing clinical evaluation. A recombinant yeast-brachyury vaccine expressing the full-length brachyury protein has demonstrated anti-tumor activity in murine models in the absence of toxicity. A Phase I clinical trial of this vaccine has now been completed in patients with advanced carcinomas or chordoma, demonstrating ability to induce multifunctional, brachyury-specific CD8+ and CD4+ T-cell responses in patients post- vs. pre-vaccination, with some evidence of disease control in absence of toxicity. In addition, a recombinant poxviral vaccine encoding brachyury and three T-cell costimulatory molecules, designated MVA-brachyury-TRICOM, is currently undergoing Phase I clinical testing in patients with advanced tumors. To our knowledge, yeast-brachyury and MVA-brachyury-TRICOM are the first vaccines targeting a driver of the phenomenon of EMT that have successfully entered clinical development. Phase II studies with these vaccines are now ongoing and planned. Multiple preclinical studies are being conducted to optimize the combinatorial use of these vaccines with other anti-cancer agents, including checkpoint inhibitors and other agents. We hypothesize that eradication of brachyury-expressing cancer cells will result in clinical benefit by reducing the number of tumor cells with stem-like characteristics, including invasive/metastatic potential and resistance to conventional therapies.

References: J Clin Invest 120(2):533-44; Clin Cancer Res 18(14):3868-79; Oncotarget 4(10):1777-90; J Natl Cancer Inst 106(5); Cancer Immunol Res. PMID: 26130065; Cancer Res 74(9):2510-9

Citation Format: Claudia Palena, Duane H. Hamilton, Justin M. David, Charli Dominguez, Christopher R. Heery, James L. Gulley, Jeffrey Schlom. Targeting the epithelial-mesenchymal transition via brachyury-based cancer vaccines. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr CN04-01.

Abstract A42: MK-1775, a WEE1 inhibitor alleviates resistance to immune attack of tumor cells undergoing an epithelial-mesenchymal transition

The phenomenon of epithelial-mesenchymal transition (EMT) is a phenotypic switch that allows epithelial tumor cells to acquire features of mesenchymal cells, including the ability to migrate and invade and, therefore, to disseminate from the primary site. In addition to promoting tumor dissemination, various reports have demonstrated that acquisition of features of EMT associates with tumor resistance to the cytotoxic effects of chemotherapy, radiation, and some targeted therapies. It is not well understood, however, the contribution of EMT to the escape of tumors from host immune-surveillance and immune-mediated rejection. Our laboratory has characterized the T-box transcription factor brachyury as a tumor-associated antigen and a regulator of EMT in human carcinomas. By generating isogenic cancer cell lines with various levels of brachyury expression, we demonstrated that high levels of brachyury significantly reduce the susceptibility of cancer cells to lysis by both antigen-specific T cells and natural killer cells, and render tumor cells less responsive to a cancer vaccine in syngeneic murine tumor models. This resistance was due to inefficient caspase-dependent apoptosis, manifested as inefficient nuclear lamin degradation in the presence of activated effector caspases. We correlated this phenomenon to loss of cell cycle kinase CDK1, which mediates lamin phosphorylation. In support of a causal connection, pre-treatment of tumor cells with MK-1775, a specific inhibitor of WEE1, which is known to be a negative regulator kinase of CDK1 activity, could counter the defective apoptosis of tumor cells expressing high levels of brachyury. Thus, our findings suggest reconstituting CDK1 activity to threshold levels might be sufficient to elevate immune-mediated lysis of mesenchymal-like cancer cells, and improve the efficacy of anti-tumor vaccines.

Citation Format: Duane H. Hamilton, Romaine I. Fernando, Kwong-Yok Tsang, Claudia Palena. MK-1775, a WEE1 inhibitor alleviates resistance to immune attack of tumor cells undergoing an epithelial-mesenchymal transition. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A42.

Immune Targeting of Tumor Epithelial-Mesenchymal Transition via Brachyury-Based Vaccines

As a manifestation of their inherent plasticity, carcinoma cells undergo profound phenotypic changes during progression toward metastasis. One such phenotypic modulation is the epithelial-mesenchymal transition (EMT), an embryonically relevant process that can be reinstated by tumor cells, resulting in the acquisition of metastatic propensity, stem-like cell properties, and resistance to a variety of anticancer therapies, including chemotherapy, radiation, and some small-molecule targeted therapies. Targeting of the EMT is emerging as a novel intervention against tumor progression. This review focuses on the potential use of cancer vaccine strategies targeting tumor cells that exhibit mesenchymal-like features, with an emphasis on the current status of development of vaccine platforms directed against the T-box transcription factor brachyury, a novel cancer target involved in tumor EMT, stemness, and resistance to therapies. Also presented is a summary of potential mechanisms of resistance to immune-mediated attack driven by EMT and the development of novel combinatorial strategies based on the use of agents that alleviate tumor EMT for an optimized targeting of plastic tumor cells that are responsible for tumor recurrence and the establishment of therapeutic refractoriness.

Overexpression of the EMT driver brachyury in breast carcinomas: association with poor prognosis

BACKGROUND

The epithelial-mesenchymal transition (EMT) has been implicated as an important process in tumor cell invasion, metastasis, and drug resistance. The transcription factor brachyury has recently been described as a driver of EMT of human carcinoma cells.

METHODS

Brachyury mRNA and protein expression was analyzed in human breast carcinomas and benign tissues. The role of brachyury in breast tumor prognosis and drug resistance and the ability of brachyury-specific T cells to lyse human breast carcinoma cells were also evaluated. Kaplan-Meier analyses were used to evaluate the association between brachyury expression and survival. All statistical tests were two-sided.

RESULTS

The level of brachyury expression in breast cancer cells was positively associated with their ability to invade the extracellular matrix, efficiently form mammospheres in vitro, and resist the cytotoxic effect of docetaxel. A comparison of survival among breast cancer patients treated with tamoxifen in the adjuvant setting who had tumors with high vs low brachyury mRNA expression demonstrated that high expression of brachyury is associated as an independent variable with higher risk of recurrence (hazard ratio [HR] = 7.5; 95% confidence interval [CI] = 2.4 to 23.5; P = 5.14×10(-4)) and distant metastasis (HR = 15.2; 95% CI = 3.5 to 66.3; P = 3.01×10(-4)). We also demonstrated that brachyury-specific T cells can lyse human breast carcinoma cells.

CONCLUSIONS

The studies reported here provide the rationale for the use of a vaccine targeting brachyury for the therapy of human breast cancer, either as a monotherapy or in combination therapies.

WEE1 inhibition alleviates resistance to immune attack of tumor cells undergoing epithelial-mesenchymal transition

Aberrant expression of the T-box transcription factor brachyury in human carcinomas drives the phenomenon of epithelial-mesenchymal transition (EMT), a phenotypic modulation that facilitates tumor dissemination and resistance to conventional therapies, including chemotherapy and radiotherapy. By generating isogenic cancer cell lines with various levels of brachyury expression, we demonstrate that high levels of brachyury also significantly reduce the susceptibility of cancer cells to lysis by both antigen-specific T cells and natural killer cells. Our results indicated that resistance of brachyury-high tumor cells to immune-mediated attack was due to inefficient caspase-dependent apoptosis, manifested as inefficient nuclear lamin degradation in the presence of activated effector caspases. We correlated this phenomenon with loss of cell-cycle-dependent kinase 1 (CDK1), which mediates lamin phosphorylation. In support of a causal connection, pretreatment of tumor cells with a specific inhibitor of WEE1, a negative regulator kinase of CDK1, could counter the defective apoptosis of tumor cells expressing high levels of brachyury. Thus, our findings suggested that reconstituting CDK1 activity to threshold levels may be sufficient to restore immunosurveillance of mesenchymal-like cancer cells that have escaped previous immune detection or eradication.

Vaccine-mediated immunotherapy directed against a transcription factor driving the metastatic process

Numerous reports have now demonstrated that the epithelial-to-mesenchymal transition (EMT) process is involved in solid tumor progression, metastasis, and drug resistance. Several transcription factors have been implicated as drivers of EMT and metastatic progression, including Twist. Overexpression of Twist has been shown to be associated with poor prognosis and drug resistance for many carcinomas and other tumor types. The role of Twist in experimental cancer metastases has been principally studied in the 4T1 mammary tumor model, where silencing of Twist in vitro has been shown to greatly reduce in vivo metastatic spread. Transcription factors such as Twist are generally believed to be "undruggable" because of their nuclear location and lack of a specific groove for tight binding of a small molecule inhibitor. An alternative approach to drug therapy targeting transcription factors driving the metastatic process is T-cell-mediated immunotherapy. A therapeutic vaccine platform that has been previously characterized consists of heat-killed recombinant Saccharomyces cerevisiae (yeast) capable of expressing tumor-associated antigen protein. We report here the construction and characterization of a recombinant yeast expressing the entire Twist protein, which is capable of inducing both CD8(+) and CD4(+) Twist-specific T-cell responses in vivo. Vaccination of mice reduced the size of primary transplanted 4T1 tumors and had an even greater antitumor effect on lung metastases of the same mice, which was dependent on Twist-specific CD8(+) T cells. These studies provide the rationale for vaccine-induced T-cell-mediated therapy of transcription factors involved in driving the metastatic process.

An autocrine loop between TGF-β1 and the transcription factor brachyury controls the transition of human carcinoma cells into a mesenchymal phenotype

The epithelial-mesenchymal transition (EMT) is a process associated with the metastasis of solid tumors as well as with the acquisition of resistance to standard anticancer modalities. A major initiator of EMT in carcinoma cells is TGF-β, which has been shown to induce the expression of several transcription factors ultimately responsible for initiating and maintaining the EMT program. We have previously identified Brachyury, a T-box transcription factor, as an inducer of mesenchymal features in human carcinoma cells. In this study, a potential link between Brachyury and TGF-β signaling has been investigated. The results show for the first time that Brachyury expression is enhanced during TGF-β1-induced EMT in various human cancer cell lines, and that a positive feedback loop is established between Brachyury and TGF-β1 in mesenchymal-like tumor cells. In this context, Brachyury overexpression is shown to promote upregulation of TGF-β1 at the mRNA and protein levels, an effect mediated by activation of the TGF-β1 promoter in the presence of high levels of Brachyury. Furthermore, inhibition of TGF-β1 signaling by a small-molecule inhibitor of TGF-β receptor type I decreases Brachyury expression, induces a mesenchymal-to-epithelial transition, and renders cancer cells more susceptible to chemotherapy. This study thus has implications for the future development of clinical trials using TGF-β inhibitors in combination with other anticancer agents.

Abstract 278: High levels of expression of the transcription factor Brachyury induce resistance of human carcinoma cells to immune-mediated attack

The phenomenon of epithelial-mesenchymal transition (EMT) is recognized as a relevant process during the progression of carcinomas. EMT is a phenotypic switch that allows epithelial tumor cells to acquire features of mesenchymal cells, including the ability to migrate and invade and, therefore, to disseminate from the primary site. In addition to promoting tumor dissemination, various reports have demonstrated that acquisition of features of EMT associates with tumor resistance to the cytotoxic effects of chemotherapy, radiation, and some targeted therapies. Presently, no studies have been conducted to thoroughly investigate whether this phenotypic switch may also contribute to the escape of tumors from host immune-surveillance and immune-mediated rejection. Our laboratory has characterized the T-box transcription factor Brachyury as a tumor-associated antigen and a regulator of EMT in human carcinomas. Currently, a Brachyury-based, recombinant yeast cancer vaccine is ongoing Phase I clinical testing for the treatment of patients with advanced carcinomas. Work in our laboratory has demonstrated that high levels of Brachyury expression in human carcinoma cell lines is associated with increased resistance to both chemo- and radiation therapies. In the present study, human epithelial carcinoma cell lines undergoing EMT via Brachyury over-expression and their epithelial tumor cell counterparts were comparatively utilized to evaluate whether EMT imparts resistance to immune-mediated attack. Our results demonstrate a bell-shaped relationship between the levels of Brachyury expression and the susceptibility of human carcinoma cell lines to lysis by immune cells. While tumor cells with low/intermediate levels of Brachyury expression are vulnerable to cell lysis, those with high levels of Brachyury expression are very resistant to lysis by immune cells. Our results demonstrate that a high level of Brachyury expression in human tumor cells reduces their susceptibility to antigen-specific CD8+ cytotoxic T cells and innate, natural killer (NK) and lymphokine-activated killer (LAK) cells. While the mechanisms involved in this phenomenon are currently under investigation in our laboratory, preliminary studies suggest that antigen processing and/or presentation is not responsible for the defective immune-mediated cytotoxicity of EMT-tumors. Altogether our results indicate that targeting the process of EMT may be a successful strategy not only to interfere with tumor dissemination but also to increase the effectiveness of immunotherapeutic interventions against metastatic tumors.

Citation Format: Duane H. Hamilton, Bruce Huang, Romaine I. Fernando, Kwong-Yok Tsang, Claudia M. Palena. High levels of expression of the transcription factor Brachyury induce resistance of human carcinoma cells to immune-mediated attack. [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 278. doi:10.1158/1538-7445.AM2013-278

Abstract 1489: The T-box transcription factor Brachyury blocks cell cycle progression and mediates tumor resistance to chemotherapy and radiation

The T-box transcription factor Brachyury, a molecule frequently detected in human cancers but seldom found in normal adult tissue, has recently been proposed as a significant determinant of the epithelial-mesenchymal transition (EMT) in human carcinomas. In the current investigation, we present data demonstrating that in three different human lung carcinoma models, expression of Brachyury is associated with a mesenchymal phenotype. Additionally, elevated Brachyury expression is shown to strongly correlate with increased in vitro resistance to cytotoxic therapies, such as chemotherapy and radiation. Further investigation showed that chemotherapy treatment in vitro selected tumor cells that were high in Brachyury, and that the degree of resistance to therapy was comparable to the level of Brachyury expression. We also demonstrate that in vitro and in vivo, human lung carcinoma cells with greater levels of Brachyury divide at slower rates than those with lower levels of Brachyury, a phenomenon associated with marked downregulation of cyclin D1, phosphorylated Rb (pRb), and CDKN1A (p21). ChIP and luciferase resporter assays revealed that Brachyury represses p21 expression in carcinoma cells by directly binding to a half T-box consensus site located within the promoter region of the p21 gene, indicating a potential mechanism for the observed therapy resistance associated with Brachyury expression. Finally, we observed that in vivo treatment of tumor xenografts with chemotherapy resulted in the selective growth of resistant tumors that were high in Brachyury. Altogether, these results suggest that in addition to being a driver of EMT, Brachyury expression may attenuate cell cycle progression, and enable tumor cells to become less susceptible to chemotherapy and radiation in human carcinomas.

Citation Format: Bruce K. Huang, Joseph Cohen, Romaine I. Fernando, Duane H. Hamilton, Mary T. Litzinger, James W. Hodge, Claudia M. Palena. The T-box transcription factor Brachyury blocks cell cycle progression and mediates tumor resistance to chemotherapy and radiation. [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 1489. doi:10.1158/1538-7445.AM2013-1489

Influence of IL-8 on the epithelial-mesenchymal transition and the tumor microenvironment

The phenomenon of epithelial-mesenchymal transition (EMT) has gained attention in the field of cancer biology for its potential contribution to the progression of carcinomas. Tumor EMT is a phenotypic switch that promotes the acquisition of a fibroblastoid-like morphology by epithelial tumor cells, resulting in enhanced tumor cell motility and invasiveness, increased metastatic propensity and resistance to chemotherapy, radiation and certain small-molecule-targeted therapies. Tumor cells undergoing EMT are also known to increase the secretion of specific factors, including cytokines, chemokines and growth factors, which could play an important role in tumor progression. This review summarizes the current knowledge on the secretory properties of epithelial tumor cells that have undergone an EMT, with an emphasis on the potential role of the IL-8-IL-8 receptor axis on the induction and/or maintenance of tumor EMT and its ability to remodel the tumor microenvironment.

Cancer vaccines targeting the epithelial-mesenchymal transition: tissue distribution of brachyury and other drivers of the mesenchymal-like phenotype of carcinomas

The epithelial-mesenchymal transition (EMT) is thought to be a critical step along the metastasis of carcinomas. In addition to gaining motility and invasiveness, tumor cells that undergo EMT also acquire increased resistance to many traditional cancer treatment modalities, including chemotherapy and radiation. As such, EMT has become an attractive, potentially targetable process for therapeutic interventions against tumor metastasis. The process of EMT is driven by a group of transcription factors designated as EMT transcription factors, such as Snail, Slug, Twist, and the recently identified T-box family member, Brachyury. In an attempt to determine which of these drivers of EMT is more amenable to targeted therapies and, in particular, T-cell-mediated immunotherapeutic approaches, we have examined their relative expression levels in a range of human and murine normal tissues, cancer cell lines, and human tumor biopsies. Our results demonstrated that Brachyury is a molecule with a highly restricted human tumor expression pattern. We also demonstrated that Brachyury is immunogenic and that Brachyury-specific CD8(+) T cells expanded in vitro are able to lyse Brachyury-positive tumor cells. We thus propose Brachyury as an attractive target for vaccination strategies designed to specifically target tumor cells undergoing EMT.

Abstract A64: Brachyury-mediated epithelial-mesenchymal transition of human carcinoma cells is associated with an increased resistance to immune-mediated attack

The epithelial-mesenchymal transition (EMT) has recently been recognized as a relevant process during the progression of carcinomas. Epithelial tumor cells undergoing EMT have been shown to acquire a mesenchymal-like phenotype, cell motility, and invasiveness, in vivo metastatic propensity and stem cell-like properties, including the ability to resist cell death initiated by traditional cancer treatment modalities such as chemotherapy and radiation. The development of therapeutic interventions aimed at interfering with EMT is therefore emerging as a rational approach for the prevention of cancer metastasis and alleviation of therapeutic resistance. Promising results recently obtained in preclinical and clinical studies with cancer vaccines may lead to their use for the treatment of various types of cancer; the concept of utilizing a vaccine to specifically target essential regulators of EMT is yet to be exploited in the field of tumor immunology. Recently, we have demonstrated that Brachyury, a T-box transcription factor essential for embryonic development, plays a central role in the induction of EMT in human carcinoma cells. In contrast to other drivers of EMT, Brachyury is highly expressed in various types of human tumors, while its expression in most normal adult tissues is undetectable. Moreover, Brachyury-specific T cells capable of lysing human tumor cell lines in an antigen-specific, HLA-restricted manner can be expanded from the peripheral blood of cancer patients, making Brachyury an attractive target for a vaccination strategy designed to specifically target cells undergoing an EMT. In light of the documented resistance of mesenchymal-like tumor cells to chemotherapy and radiation, we have thoroughly investigated the susceptibility of tumor cells undergoing EMT to immune-mediated attack. Utilizing several epithelial human tumor cell lines stably transfected to express various levels of Brachyury, we have observed that tumor cells with low to moderate amounts of Brachyury can be efficiently lysed by various immune-mediated mechanisms, while very high levels of Brachyury expression correlate with increased resistance to lysis mediated by natural killer (NK) cells, lymphokine-activated killer (LAK) cells, and antigen-specific CD8+ T cells. It has been suggested that EMT is a reversible process, whereby cells can undergo a mesenchymal-epithelial transition (MET). By stably inhibiting the expression of Brachyury in various mesenchymal-like human tumor cell lines, we have also demonstrated that induction of MET restores susceptibility of tumor cells to immune-mediated attack. Currently, the mechanisms responsible for the acquisition of increased resistance to immune-mediated killing by cells undergoing an EMT are being investigated. The results from these studies will be fundamental in designing strategies aimed at rendering metastatic carcinoma cells more susceptible not only to chemotherapy and radiation, but also to immunotherapeutic interventions against the tumor.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A64.

Abstract C53: Overexpression of Brachyury in human carcinoma cells drives the acquisition of resistance to anticancer therapeutics

The epithelial-mesenchymal transition (EMT) has been recognized as a process crucial to the progression of carcinomas, mediating the conversion of stationary epithelial tumor cells into mesenchymal-like, invasive tumor cells. Recent reports have also demonstrated a potential association between tumor EMT and the acquisition of resistance to cell death in carcinoma cells. We recently identified the T-box transcription factor Brachyury, a molecule prevalently expressed in human tumors but seldom found in normal adult tissues, as a novel driver of EMT in human carcinomas. Brachyury was demonstrated to induce the expression of molecules associated with the mesenchymal phenotype, tumor cell motility and invasiveness in vitro, as well as metastatic propensity in xenograft models. In the current study, we investigated whether deregulated expression of Brachyury in human lung tumor cells is also associated with acquisition of resistance to the conventional anti-cancer modalities, chemotherapy and radiation. Our results demonstrated that over-expression of Brachyury in epithelial lung tumor cells significantly improved their survival in response to treatment with various doses of Taxotere, Cisplatin, Vinorelbine, and combinations of Cisplatin plus Vinorelbine, as well as to various doses of gamma-radiation. Similarly, inhibition of Brachyury expression by using Brachyury-specific shRNA constructs in mesenchymal-like, human lung tumor cells resulted in enhanced susceptibility to the same cytotoxic agents. Analysis of clonal lines derived from single-cell isolates of human lung tumor cells expressing various amounts of Brachyury revealed an inverse relationship between Brachyury levels and tumor growth, and a positive correlation of Brachyury with the ability to resist treatment by Taxotere, Cisplatin, Vinorelbine, and Cisplatin plus Vinorelbine combinations. Detailed gene expression analysis demonstrated a positive association between Brachyury expression and markers of tumor stemness, such as the MDR1/ABCB1 transporter, and the self-renewal transcription factors Sox-2, Oct4, and Nanog. These results thus raise the possibility that in addition to being a mediator of EMT, Brachyury may also be a marker for human tumor cells bearing stem-like characteristics and resistance to conventional therapeutics. One approach that may overcome the therapeutic resistance of tumors undergoing Brachyury-mediated EMT is that of immune-mediated targeting – we have previously characterized the immunogenicity of the Brachyury protein and generated Brachyury-specific human T-cell lines that have the ability to lyse Brachyury-positive tumor cells. We hypothesize that the eradication of Brachyury-expressing tumor cells via Brachyury-based immunotherapeutic approaches could be efficient at eliminating tumor cells with metastatic propensity as well as at alleviating tumor resistance in response to conventional therapies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr C53.

IL-8 signaling plays a critical role in the epithelial-mesenchymal transition of human carcinoma cells

The switch of tumor cells from an epithelial to a mesenchymal-like phenotype [designated as epithelial-to-mesenchymal transition (EMT)] is known to induce tumor cell motility and invasiveness, therefore promoting metastasis of solid carcinomas. Although multiple studies have focused on elucidating the signaling events that initiate this phenotypic switch, there has been so far no characterization of the pattern of soluble mediators released by tumor cells undergoing EMT, and the potential impact that this phenotypic switch could have on the remodeling of the tumor microenvironment. Here we show that induction of EMT in human carcinoma cells via overexpression of the transcription factor Brachyury is associated with enhanced secretion of multiple cytokines, chemokines, and angiogenic factors and, in particular, with the induction of the IL-8/IL-8R axis. Our results also indicate the essential role of interleukin 8 (IL-8) signaling for the acquisition and/or maintenance of the mesenchymal and invasive features of Brachyury-overexpressing tumor cells and show that IL-8 secreted by tumor cells undergoing EMT could potentiate tumor progression by inducing adjacent epithelial tumor cells into EMT. Altogether, our results emphasize the potential role of EMT in the modulation of the tumor microenvironment via secretion of multiple soluble mediators and suggest that IL-8 signaling blockade may provide a means of targeting mesenchymal-like, invasive tumor cells.

Strategies to target molecules that control the acquisition of a mesenchymal-like phenotype by carcinoma cells

The switch of carcinoma cells from an epithelial to a mesenchymal-like phenotype, via a process designated 'epithelial-to-mesenchymal transition (EMT),' has been recognized as a relevant step in the metastasis of solid tumors. Additionally, this phenotypic switch of carcinoma cells has been associated with the acquisition of tumor resistance mechanisms that reduce the antitumor effects of radiation, chemotherapy and some small-molecule-targeted therapies. As multiple signaling pathways and transcriptional regulators that play a role in this phenotypic switch are being identified, novel strategies can be designed to specifically target tumor cells with this metastatic and resistant phenotype. In particular, this review focuses on the potential use of cancer vaccine strategies to target tumor cells that exhibit a mesenchymal-like phenotype, with an emphasis on the characterization of a novel tumor antigen, Brachyury, which we have identified as a critical regulator of EMT in human cancer cells.

The T-box transcription factor Brachyury promotes epithelial-mesenchymal transition in human tumor cells

Metastatic disease is responsible for the majority of human cancer deaths. Understanding the molecular mechanisms of metastasis is a major step in designing effective cancer therapeutics. Here we show that the T-box transcription factor Brachyury induces in tumor cells epithelial-mesenchymal transition (EMT), an important step in the progression of primary tumors toward metastasis. Overexpression of Brachyury in human carcinoma cells induced changes characteristic of EMT, including upregulation of mesenchymal markers, downregulation of epithelial markers, and an increase in cell migration and invasion. Brachyury overexpression also repressed E-cadherin transcription, an effect partially mediated by Slug. Conversely, inhibition of Brachyury resulted in downregulation of mesenchymal markers and loss of cell migration and invasion and diminished the ability of human tumor cells to form lung metastases in a xenograft model. Furthermore, we found Brachyury to be overexpressed in various human tumor tissues and tumor cell lines compared with normal tissues. We also determined that the percentage of human lung tumor tissues positive for Brachyury expression increased with the stage of the tumor, indicating a potential association between Brachyury and tumor progression. The selective expression of Brachyury in tumor cells and its role in EMT and cancer progression suggest that Brachyury may be an attractive target for antitumor therapies.

Different immune correlates associated with tumor progression and regression: implications for prevention and treatment of cancer

Observations show that humans and animals respond immunologically to most cancers. Why does the immune system then fail to control cancer? We argue from the literature that there is a commonality in the regulation of responses against most murine tumors, and that a major mechanism of escape may be deviation of an effective Th1, cytotoxic T lymphocyte response to a less effective response with a Th2 component. We examined this hypothesis with two well-studied murine tumors. We found, following primary tumor implantation, that resistance correlates with Th1 responses and IgG2a antibody production and progression with mixed Th1/Th2 responses and production of IgG1 and IgG2a antibodies. Resistance is associated with a modulation of the anti-tumor response towards the Th1 pole in both systems. We conclude that the immune responses against these two tumors are in accord with our hypothesis, and argue that this is likely to be true of many human and murine tumors. The correlation of IgG isotype of anti-tumor antibody with the Th1/Th2 nature of the anti-tumor response readily allows one to longitudinally monitor the changing nature of the anti-tumor response. We suggest that such monitoring can guide immunotherapy to maximize the effectiveness of the host's immune response against cancer.

Analysis of cytokine-producing Th cells from hen egg lysozyme-immunized mice reveals large numbers specific for "cryptic" peptides and different repertoires among different Th populations

We employed an optimized ex vivo enzyme-linked immunospot assay for enumerating and defining the peptide specificity of all the hen egg lysozyme (HEL)-specific Th cells producing IL-2, IFN-gamma, or IL-4, in different lymphoid organs of HEL-immunized BALB/c and CBA mice. Previous studies, employing T cell proliferation assays, demonstrated that lymph node cells from BALB/c mice immunized with HEL emulsified in complete Freund's adjuvant (CFA) are specific for HEL(105-120). In contrast, we found that the spleens of BALB/c mice immunized with HEL/CFA, or with heat-aggregated HEL on aluminum hydroxide adjuvant, contain IL-4-producing T cells specific for other HEL peptides, previously characterized as "cryptic", with consistent responses to HEL(11-25). The Th repertoire expressed in different lymphoid organs of the same immunized mouse can be different, as can the repertoire of Th cells producing different cytokines and present in one lymphoid organ. In addition, we found that the repertoire of Th cells generated depends upon the adjuvant employed. Lastly, the summation of responses elicited by a panel of non-overlapping HEL peptides is equal to that elicited by HEL. This high-resolution study thus illustrates that the Th repertoire generated upon HEL immunization depends upon diverse parameters, and that the natural processing of HEL gives rise to more diverse peptides then previously evident from studies employing T cell proliferation assays.

Epidemic intelligence service of the Centers for Disease Control and Prevention: 50 years of training and service in applied epidemiology

The Epidemic Intelligence Service (EIS) was established in 1951 at the Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, as a combined training and service program in the practice of applied epidemiology. Since then, nearly 2,500 professionals have served in this 2-year program of the US Public Health Service. The experience of an EIS Officer has been modified because of the increased need for more sophisticated analytical methods and the use of microcomputers, as well as CDC's expanded mission into chronic diseases, environmental health, occupational health, and injury control. Officers who have entered the EIS in the past 20 years are more likely than their predecessors to stay in public health either at the federal level or in state and local health departments. The EIS Program continues to be a critical source for health professionals trained to respond to the demand for epidemiologic services both domestically and internationally.

Influence of diabetes mellitus on patient and graft survival in recipients of kidney transplantation

AIMS

To investigate the outcomes in patients who have pre-existing diabetes and those who develop post-transplant diabetes mellitus (PTDM).

METHODS

We retrospectively reviewed the charts of 939 patients who received a first functioning renal transplant in the cyclosporine (CyA) era between 1984 and 1999.

RESULTS

Sixty-six (7%) patients had renal failure due to insulin-dependent diabetes mellitus (IDDM) and 7 (0.8%) patients due to non-insulin-dependent diabetes mellitus (NIDDM). Ten (1.1%) patients had coexistent diabetes and 48 (5.1%) recipients developed PTDM. The mean graft survival for the patients with PTDM was 9.7 yr versus 11.3 yr for the non-diabetic patients, while mean graft survival was 10.1 yr for patients with IDDM and 2.9 yr with NIDDM and 8.3 yr for those with coexistent diabetes (p=ns). However, there was a statistically significant difference in patient survival between patients who developed PTDM and in those who did not develop this complication. The mean survivals of patients with IDDM, NIDDM, coexistent diabetics and PTDM were 8.4, 3.7, 8.6 and 10.3 yr, respectively. The mean survival of the patients without pre-existing diabetes or PTDM was 12.8 yr (p<0.001). The survival of patients older than 55 yr with PTDM was no different to the control group. However, in those younger than 55 yr, PTDM was associated with a higher risk of death (relative risk of 2.54, p<0.001). Fifty percent of patients with IDDM developed acute rejection episodes, whereas rejection rate was 57.1% in NIDDM group, 50.0% in the PTDM group, 20.0% in the coexistent diabetes group and 44.3% in the control group (p=ns).

CONCLUSION

Patient survival, but not graft survival, was adversely affected by both pre-existing diabetes and by PTDM, particularly in those with an age less than 55 yr.