Levels Of Brachyury Research Articles

Impact of CDK Inhibitors on TBXT Expression in Chordoma Cell Lines Including the First Stable Cell Line of a High-Grade Chordoma.

Chordomas are very rare malignant neoplasms of the bone occurring almost exclusively along the spine. As the tumours are thought to arise from notochordal remnants, the vast majority of chordomas express the TBXT gene, resulting in detectable nuclear amounts of its gene product brachyury. This T-Box transcription factor is commonly recognised as being essential in chordoma cells, and limiting TBXT expression is thought to be the key factor in controlling this tumour. Although the tumour is rare, distinct molecular differences and vulnerabilities have been described with regard to its location and the progression status of the disease, rendering it mandatory for novel cell lines to reflect all relevant chordoma subtypes. Here, we describe a novel chordoma cell line arising from the pleural effusion of a disseminated, poorly differentiated chordoma. This cell line, U-CH22, represents a highly aggressive terminal chordoma and, therefore, fills a relevant gap within the panel of available cell culture models for this orphan disease. CDK7 and CDK9 inhibition was lately identified as being effective in reducing viability in four chordoma cell lines, most likely due to a reduction in brachyury levels. In this study, we determined the capability of the CDK7 inhibitor THZ1 and the CDK1/2/5/9 inhibitor dinaciclib to reduce TBXT expression at mRNA and protein levels in a broad range of nine cell lines that are models of primary, recurrent, and metastasised chordoma of the clivus and the sacrum.

Unraveling molecular advancements in chordoma tumorigenesis and treatment response: a review of scientific discoveries and clinical implications.

Chordomas are tumors thought to originate from notochordal remnants that occur in midline structures from the cloves of the skull base to the sacrum. In adults, the most common location is the sacrum, followed by the clivus and then mobile spine, while in children a clival origin is most common. Most chordomas are slow growing. Clinical presentation of chordomas tend to occur late, with local invasion and large size often complicating surgical intervention. Radiation therapy with protons has been proven to be an effective adjuvant therapy. Unfortunately, few adjuvant systemic treatments have demonstrated significant effectiveness, and chordomas tend to recur despite intensive multimodal care. However, insight into the molecular underpinnings of chordomas may guide novel therapeutic approaches including selection for immune and molecular therapies, individualized prognostication of outcomes, and real-time noninvasive assessment of disease burden and evolution. At the genomic level, elevated levels of brachyury stemming from duplications and mutations resulting in altered transcriptional regulation may introduce druggable targets for new surgical adjuncts. Transcriptome and epigenome profiling have revealed promoter- and enhancer-dependent mechanisms of protein regulation, which may influence therapeutic response and long-term disease history. Continued scientific and clinical advancements may offer further opportunities for treatment of chordomas. Single-cell transcriptome profiling has further provided insight into the heterogeneous molecular pathways contributing to chordoma propagation. New technologies such as spatial transcriptomics and emerging biochemical analytes such as cell-free DNA have further augmented the surgeon-clinician's armamentarium by facilitating detailed characterization of intra- and intertumoral biology while also demonstrating promise for point-of-care tumor quantitation and assessment. Recent and ongoing clinical trials highlight accelerating interest to translate laboratory breakthroughs in chordoma biology and immunology into clinical care. In this review, the authors dissect the landmark studies exploring the molecular pathogenesis of chordoma. Incorporating this into an outline of ongoing clinical trials and discussion of emerging technologies, the authors aimed to summarize recent advancements in understanding chordoma pathogenesis and how neurosurgical care of chordomas may be augmented by improvements in adjunctive treatments.

Development of a Small Molecule Downmodulator for the Transcription Factor Brachyury

AbstractBrachyury is an oncogenic transcription factor whose overexpression drives chordoma growth. The downmodulation of brachyury in chordoma cells has demonstrated therapeutic potential, however, as a transcription factor it is classically deemed “undruggable”. Given that direct pharmacological intervention against brachyury has proven difficult, attempts at intervention have instead targeted upstream kinases. Recently, afatinib, an FDA‐approved kinase inhibitor, has been shown to modulate brachyury levels in multiple chordoma cell lines. Herein, we use afatinib as a lead to undertake a structure‐based drug design approach, aided by mass‐spectrometry and X‐ray crystallography, to develop DHC‐156, a small molecule that more selectively binds brachyury and downmodulates it as potently as afatinib. We eliminated kinase‐inhibition from this novel scaffold while demonstrating that DHC‐156 induces the post‐translational downmodulation of brachyury that results in an irreversible impairment of chordoma tumor cell growth. In doing so, we demonstrate the feasibility of direct brachyury modulation, which may further be developed into more potent tool compounds and therapies.

Development of a Small Molecule Downmodulator for the Transcription Factor Brachyury.

Brachyury is an oncogenic transcription factor whose overexpression drives chordoma growth. The downmodulation of brachyury in chordoma cells has demonstrated therapeutic potential, however, as a transcription factor it is classically deemed "undruggable". Given that direct pharmacological intervention against brachyury has proven difficult, attempts at intervention have instead targeted upstream kinases. Recently, afatinib, an FDA-approved kinase inhibitor, has been shown to modulate brachyury levels in multiple chordoma cell lines. Herein, we use afatinib as a lead to undertake a structure-based drug design approach, aided by mass-spectrometry and X-ray crystallography, to develop DHC-156, a small molecule that more selectively binds brachyury and downmodulates it as potently as afatinib. We eliminated kinase-inhibition from this novel scaffold while demonstrating that DHC-156 induces the post-translational downmodulation of brachyury that results in an irreversible impairment of chordoma tumor cell growth. In doing so, we demonstrate the feasibility of direct brachyury modulation, which may further be developed into more potent tool compounds and therapies.

Ultrasensitive Detection of Attomolar Protein Concentrations by Dropcast Single Molecule Assays.

Measurements of very low levels of biomolecules, including proteins and nucleic acids, remain a critical challenge in many clinical diagnostic applications due to insufficient sensitivity. While digital measurement methods such as Single Molecule Arrays (Simoa), or digital ELISA, have made significant advances in sensitivity, there are still many potential disease biomarkers that exist in accessible biofluids at levels below the detection limits of these techniques. To overcome this barrier, we have developed a simple strategy for single molecule counting, dropcast single molecule assays (dSimoa), that enables more target molecules to be counted through increased sampling efficiency and with a simpler workflow. In this approach, beads are simply dropcast onto a microscope slide and dried into a monolayer film for digital signal readout. The dSimoa platform achieves attomolar limits of detection, with an up to 25-fold improvement in sensitivity over Simoa, the current state of the art for ultrasensitive protein detection. Furthermore, due to its simple readout process and improved cost-effectiveness compared to existing digital bioassays, dSimoa increases amenability to integration into point-of-care platforms. As an illustration of the potential utility of dSimoa, we demonstrate its ability to measure previously undetectable levels of Brachyury, a tissue biomarker for chordoma, in plasma samples. With its significantly enhanced sensitivity and simplicity, dSimoa can pave the way toward the discovery of new biomarkers for early disease diagnosis and improved health outcomes.

All-trans retinoic acid (ATRA) reduces proliferative capacity and Brachyury levels in the chordoma cell line UCH-1

AbstractChordoma is a rare bone cancer for which there are no approved drugs. Surgery is the principle treatment but complete resection can be challenging due to the location of the tumours in the spine and therefore finding an effective drug treatment is a pressing unmet clinical need. A major recent study identified the transcription factor Brachyury as the primary vulnerability and drug target in chordoma. Previously, all-trans retinoic acid (ATRA) has been shown to negatively influence expression of the Brachyury gene, TBXT. Here we extend this finding and demonstrate that ATRA lowers Brachyury protein levels in chordoma cells and reduces proliferation of the chordoma cell line U-CH1 as well as causing loss of distinctive chordoma cell morphology. ATRA is available as a generic drug and is the first line treatment for acute promyelocytic leukaemia (APL). This study implies ATRA could have therapeutic value if repurposed for chordoma.

TGF-β-mediated upregulation of brachyury contributes to constitutively up-regulated type I collagen expression in skin fibroblasts: possible role in systemic sclerosis.

Previous reports have shown that epithelial-to-mesenchymal transition (EMT) indicates the importance of transforming growth factor-β (TGF-β) signalling in the pathogenesis of systemic sclerosis (SSc). However, the underlying molecular mechanisms of EMT are not fully understood. Brachyury, an evolutionarily conserved transcription factor, was recently identified as an important factor that promotes EMT in human carcinoma cell lines. However, there is no evidence indicating that brachyury is involved in EMT in SSc. The expression of brachyury and collagen was investigated in cultures of dermal fibroblasts and skin sections derived from SSc patients and healthy controls. Brachyury and collagen expression were determined by immunohistochemistry and immunoblotting, respectively, and mRNA for both was analysed using real-time PCR. Brachyury was overexpressed in SSc dermal fibroblasts both in vivo and in vitro, and this overexpression was inhibited by TGF-β1 inhibitor. Brachyury siRNA reduced mRNA and protein expression levels of type I collagen in normal and SSc dermal fibroblasts, but did not decrease the levels of major disease-related cytokines. Furthermore, brachyury levels were significantly increased in skin samples of SSc patients relative to healthy controls. The up-regulation of brachyury in response to activated endogenous TGF-β signalling may play a role in constitutive up-regulation of collagen in SSc fibroblasts. Further studies assessing the regulatory mechanism of tissue fibrosis induced by brachyury in SSc skin may lead to a better understanding of the pathogenesis, new diagnostic methods, and new therapeutic approaches using siRNAs.

Brachyury oncogene is a prognostic factor in high-risk testicular germ cell tumors.

The T-box transcription factor Brachyury has been considered a cancer-specific marker and a novel oncotarget in solid tumors. Brachyury overexpression has been described in various cancers, being associated with epithelial-mesenchymal transition, metastasis, and poor prognosis. However, its clinical association with testicular germ cell tumor is unknown. We analyzed the expression of Brachyury by immunohistochemistry in a series of well-characterized testicular germ cell tumor samples and at transcript level by in silico analysis. Additionally, we aimed to investigate the clinical significance of Brachyury in testicular germ cell tumor. Brachyury cytoplasm immunostaining was present in 89.6% (86/96) of cases with nuclear staining observed in 24% (23/96) of testicular germ cell tumor. Bioinformatics microarray expression analysis of two independent cohorts of testicular germ cell tumors showed similar results with increased levels of Brachyury in testicular germ cell tumors and metastasis compared with normal testis. Clinically, Brachyury nuclear staining was statistically associated with lower event-free survival (p=0.04) and overall survival (p=0.01) in intermediate/high-risk testicular germ cell tumors. Univariate analysis showed that Brachyury nuclear subcellular localization was a predictor of poor prognosis (p=0.02), while a tendency was observed by multivariate analysis (HR: 3.56, p=0.06). In conclusion, these results indicate that Brachyury plays an oncogenic role in testicular germ cell tumors and its subcellular localization in the nucleus may constitute a novel biomarker of poor prognosis and a putative oncotarget for intermediate/high-risk testicular germ cell tumor patients.

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.

Abstract CN07-03: Brachyury and the interleukin-8 axis in tumor progression

Abstract Carcinomas exhibit remarkable plasticity and may undergo profound phenotypic changes during progression towards metastasis. These changes, collectively termed “carcinoma mesenchymalization,” involve the acquisition of mesenchymal features; invasiveness and propensity to disseminate; acquisition of stemness features, including a relatively quiescent state; and conversion into a refractory, therapy-resistant state. In search of drivers of the mesenchymalization phenomenon that could be targeted via immunotherapy, our laboratory previously identified the embryonic T-box transcription factor brachyury as a tumor-associated antigen that is highly expressed in various human carcinomas, including lung and triple-negative breast cancer and in the rare tumor type chordoma, among others. High brachyury levels at the primary tumor site have now been shown to associate with poor survival in patients with various cancer types. Two vector-based cancer vaccine platforms developed against brachyury, a yeast-brachyury and a poxvirus-based MVA-brachyury-TRICOM vaccine, have now completed phase I clinical evaluation, both demonstrating safety and the ability to significantly expand brachyury-specific CD4+ and CD8+ T cells in vaccinated patients. Based on evidence of clinical activity in patients with chordoma, the yeast-brachyury vaccine is currently being evaluated in a randomized, double-blind phase II study of radiation +/- vaccine in this rare tumor type. An emerging concept in the field of tumor immunology is that mesenchymalization may also confer resistance to antitumor immune responses. Our laboratory has shown that human carcinoma cells undergoing mesenchymalization exhibit decreased susceptibility to lysis mediated by immune effector cells, including antigen-specific CD8+ T cells, innate natural killer (NK) cells, and lymphokine-activated killer (LAK) cells. Based on these observations, we are currently investigating potential strategies aimed at blocking tumor microenvironment-derived signals that control phenotypic plasticity, with the ultimate goal of combining these approaches with immunotherapy. The chemokine interleukin-8 (IL-8) is overexpressed in multiple cancer types, where it promotes the acquisition of mesenchymal features, stemness, resistance to therapies, and the recruitment of immune-suppressive cells to the tumor site. We have now shown that blockade of the IL-8/IL-8R axis is effective at reverting the phenotype of the tumor cells towards a more epithelial one, decreasing stemness features, and significantly enhancing tumor sensitivity to chemotherapy, small-molecule targeted therapies, and immune-mediated lysis with NK and antigen-specific T cells in vitro. These results formed the rationale for using anti-IL8 approaches in combination with cytotoxic or immune-based therapies for the treatment of advanced cancer. Citation Format: Claudia Palena, James L. Gulley, Jeffrey Schlom. Brachyury and the interleukin-8 axis in tumor progression [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr CN07-03.

Brachyury, a driver of epithelial mesenchymal transition, as an independent prognostic factor in high-grade testicular germ cell tumors.

e16039 Background: The T-box transcription factor Brachyury has been considered a cancer-specific marker and a novel oncotarget in solid tumors. Brachyury overexpression has been described in various cancers, being associated with epithelial-mesenchymal transition, metastasis and poor prognosis. However, its clinical association with testicular germ cell tumor (TGCT) is unknown. Methods: We analyzed the expression of Brachyury both at protein and transcript levels in a series of 96 TGCT samples and by in silico analysis, respectively. Additionally, we investigated the clinical significance of Brachyury in TGCT. Results: Brachyury protein showed to be over-represented in 89.6% (86/96) of TGCT cases with nuclear staining in 24% (23/96) of them. Microarray expression analysis in two independent cohorts of TGCTs showed similar results with increased levels of Brachyury in TGCTs and metastasis compared with normal testis. Clinically, Brachyury nuclear staining was statistically associated with event-free survival (p = 0.04) and overall survival (p = 0.01) in intermediate/high-risk TGCTs. Multivariate analysis showed that Brachyury nuclear subcellular localization was an independent predictor of poor prognosis (HR: 3.56, p = 0.06). Conclusions: These results indicate that Brachyury plays an oncogenic role in TGCTs and its subcellular localization in the nucleus is a potential novel biomarker of poor prognosis and an oncotarget for intermediate/high-risk TGCTs treatment.

MTORC1 and mTORC2 play different roles in regulating cardiomyocyte differentiation from embryonic stem cells.

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase and functions through two distinct complexes, mTOR complex 1 (mTORC1) and complex 2 (mTORC2), with their key components Raptor and Rictor, to play crucial roles in cellular survival and growth. However, the roles of mTORC1 and mTORC2 in regulating cardiomyocyte differentiation from mouse embryonic stem (mES) cells are not clear. In this study, we performed Raptor or Rictor knockdown experiments to investigate the roles of mTORC1 and mTORC2 in cardiomyocyte differentiation. Ablation of Raptor markedly increased the number of cardiomyocytes derived from mES cells with well-organized myofilaments. Expression levels of brachyury (mesoderm protein), Nkx2.5 (cardiac progenitor cell protein), and α-Actinin (cardiomyocyte marker) were increased in Raptor knockdown cells. In contrast, loss of Rictor prevented cardiomyocyte differentiation. The dual ablation of Raptor and Rictor also decreased the number of cardiomyocytes. The two complexes exerted a regulatory mechanism in such a manner that knockdown of Raptor/mTORC1 resulted in a decreased phosphorylation of Rictor (Thr1135), which subsequently activated Rictor/mTORC2 in the differentiation of mES cells into cardiomyocytes. In conclusion, mTORC1 and mTORC2 played different roles in cardiomyocyte differentiation from mES cells in vitro. The activation of Rictor/mTORC2 was critical for facilitating cardiomyocyte differentiation from mES cells. Thus, this complex may be a promising target for regulating myocardial differentiation from embryonic stem cells or induced pluripotent stem cells.

Involvement of Rictor/mTORC2 in cardiomyocyte differentiation of mouse embryonic stem cells in vitro.

Rictor is a key regulatory/structural subunit of the mammalian target of rapamycin complex 2 (mTORC2) and is required for phosphorylation of Akt at serine 473. It plays an important role in cell survival, actin cytoskeleton organization and other processes in embryogenesis. However, the role of Rictor/mTORC2 in the embryonic cardiac differentiation has been uncovered. In the present study, we examined a possible link between Rictor expression and cardiomyocyte differentiation of the mouse embryonic stem (mES) cells. Knockdown of Rictor by shRNA significantly reduced the phosphorylation of Akt at serine 473 followed by a decrease in cardiomyocyte differentiation detected by beating embryoid bodies. The protein levels of brachyury (mesoderm protein), Nkx2.5 (cardiac progenitor cell protein) and α-Actinin (cardiomyocyte biomarker) decreased in Rictor knockdown group during cardiogenesis. Furthermore, knockdown of Rictor specifically inhibited the ventricular-like cells differentiation of mES cells with reduced level of ventricular-specific protein, MLC-2v. Meanwhile, patch-clamp analysis revealed that shRNA-Rictor significantly increased the number of cardiomyocytes with abnormal electrophysiology. In addition, the expressions and distribution patterns of cell-cell junction proteins (Cx43/Desmoplakin/N-cadherin) were also affected in shRNA-Rictor cardiomyocytes. Taken together, the results demonstrated that Rictor/mTORC2 might play an important role in the cardiomyocyte differentiation of mES cells. Knockdown of Rictor resulted in inhibiting ventricular-like myocytes differentiation and induced arrhythmias symptom, which was accompanied by interfering the expression and distribution patterns of cell-cell junction proteins. Rictor/mTORC2 might become a new target for regulating cardiomyocyte differentiation and a useful reference for application of the induced pluripotent stem cells.

Clinical Features and Prognostic Factors of Children and Adolescents with Clival Chordomas

Chordomas in children and adolescents are rare, and minimal published information is available. Our aim was to research clinical features and prognostic factors associated with clival chordomas in younger patients. The study included 25 patients (10 males and 15 females). Average follow-up time was 42.95 months (range, 2-108 months). Kaplan-Meier analysis was used to determine overall survival (OS) and progression-free survival. Pearson correlation was used to perform correlation analysis. Immunohistochemistry was used to detect Ki-67, cytokeratin 8 (CK8), platelet-derived growth factor receptor-β, and brachyury expression levels. Average age (± SD) of patients was 14.44 (3.44) years. Total resection was achieved in 5 cases, and nontotal resection was achieved in 20 cases. Average OS of patients with Karnofsky performance scale score ≥90 and patients in the total resection group was significantly longer compared with OS of patients with Karnofsky performance scale score <90 (P= 0.041) and patients in the nontotal resection group (P= 0.0497). Patients with lower Ki-67 expression levels had longer OS (P= 0.0207). Progression-free survival of patients with lower CK8 expression levels was significantly longer compared with patients with higher CK8 levels (P= 0.008). Expression levels of platelet-derived growth factor receptor-β were significantly correlated with expression levels of brachyury (P= 0.016). In children and adolescents with clival chordomas, higher preoperative Karnofsky performance scale score, total resection, and lower levels of Ki-67 and CK8 expression are favorable prognostic factors. Platelet-derived growth factor receptor-β may play a role in tumorigenesis and epithelial-mesenchymal transition of clival chordomas.

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.

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

Abstract 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.

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

Abstract 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.

Abstract 5016: Short-term blockade of EGF signaling improves immune-mediated cytotoxicity of NSCLC cells

Abstract One of the manifestations of tumor plasticity is the acquisition of mesenchymal-like features by epithelial tumor cells via the phenomenon of epithelial-mesenchymal transition (EMT). This phenotypic conversion of tumor cells is known to be associated with tumor resistance to multiple cancer therapies, including chemotherapy, radiation and some small molecule-targeted therapies. Recent work from our group demonstrated that tumor cells undergoing the EMT may also become resistant to immune-mediated cytotoxicity involving antigen-specific and innate effector cells. As signaling through the epidermal growth factor receptor (EGFR) is a major inducer of EMT in epithelial cells, in the present study we sought to investigate the effect of short-term EGFR inhibition with erlotinib on tumor phenotype, and provide rationale for combination with immune-mediated therapies. Our data shows that pretreatment with the EGFR TKI erlotinib for less than 72 hours modulates tumor plasticity and immune-mediated cytotoxicity in NSCLCs harboring a sensitizing EGFR mutation. A significant modulation in expression of multiple EMT markers can be observed, including significant changes in the levels of expression of the transcription factor brachyury, a driver of human tumor EMT and a target for immunotherapeutic interventions. In addition, significant modulation of immune-relevant molecules on the surface of tumor cells can be observed, including changes in the levels of TRAIL-receptors, co-stimulatory and checkpoint molecules. The observed phenotypic changes in response to short-term erlotinib treatment correlate with an enhancement of immune-mediated tumor cell lysis, without any observed adverse affect on effector cell populations. Taking into account that brachyury-based cancer vaccines are currently being evaluated in clinical trials, modulation of brachyury levels and the observed enhancement of immune-mediated lysis in erlotinib-treated tumors may provide the rationale for future combinations of erlotinib and brachyury-based vaccines for the treatment of lung carcinomas. Citation Format: Charli Dominguez. Short-term blockade of EGF signaling improves immune-mediated cytotoxicity of NSCLC cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5016. doi:10.1158/1538-7445.AM2015-5016

Genetic basis for developmental toxicity due to statin intake using embryonic stem cell differentiation model.

The in utero environment is a key factor controlling the fate of the growing embryo. The deleterious effects of statins during the fetal development are still not very well understood. Data from animal studies and retrospective studies performed in pregnant women give conflicting reports. In this study, using in vitro differentiation model of embryonic stem cells, which mimic the differentiation process of the embryo, we have systematically exposed the cells to lipophilic statins, simvastatin, and atorvastatin at various doses and at critical times during differentiation. The analysis of key genes controlling the differentiation into ecto-, meso- and endodermal lineages was assessed by quantitative polymerase chain reaction. Our results show that genes of the mesodermal lineage were most sensitive to statins, leading to changes in the transcript levels of brachyury, Flk-1, Nkx2.5, and α/β-myosin heavy chain. In addition, changes to endodermal marker α-fetoprotein, along with ectodermal Nes and Neurofilament 200 kDa, imply that during early differentiation exposure to these drugs leads to altered signaling, which could translate to the congenital abnormalities seen in the heart and limbs.

Brachyury regulates proliferation of cancer cells via a p27Kip1-dependent pathway.

The T-box transcription factor Brachyury is expressed in a number of tumour types and has been demonstrated to have cancer inducing properties. To date, it has been linked to cancer associated induction of epithelial to mesenchymal transition, tumour metastasis and expression of markers for cancer stem-like cells. Taken together, these findings indicate that Brachyury plays an important role in the progression of cancer, although the mechanism through which it functions is poorly understood. Here we show that Brachyury regulates the potential of Brachyury-positive colorectal cancer cells to proliferate and reduced levels of Brachyury result in inhibition of proliferation, with features consistent with the cells entering a quiescent-like state. This inhibition of proliferation is dependent upon p27Kip1 demonstrating that Brachyury acts to modulate cellular proliferative fate in colorectal cancer cells in a p27Kip1-dependent manner. Analysis of patient derived colorectal tumours reveals a heterogeneous localisation of Brachyury (in the nucleolus, nucleus and cytoplasm) indicating the potential complexity of the regulatory role of Brachyury in solid colorectal tumours.