MYTX-011: A pH-Dependent Anti-c-MET Antibody-Drug Conjugate Designed for Enhanced Payload Delivery to c-MET-Expressing Tumor Cells.

Advances in linker payload technology and target selection have been at the forefront of recent improvements in antibody-drug conjugate (ADC) design, leading to several approvals over the last decade. In contrast, the potential of novel ADC technologies to enhance payload delivery to tumors is relatively underexplored. We demonstrate that incorporation of pH-dependent binding in the antibody component of a c-mesenchymal-epithelial transition (MET)-targeting ADC (MYTX-011) can overcome the requirement for high c-MET expression on tumors, an innovation that has the potential to benefit a broader population of patients with lower c-MET levels. MYTX-011 drove fourfold higher net internalization than a non-pH-engineered parent ADC in non-small cell lung cancer (NSCLC) cells and showed increased cytotoxicity against a panel of cell lines from various solid tumors. A single dose of MYTX-011 showed at least threefold higher efficacy than a benchmark ADC in mouse xenograft models of NSCLC ranging from low to high c-MET expression. Moreover, MYTX-011 showed improved pharmacokinetics over parent and benchmark ADCs. In a repeat dose toxicology study, MYTX-011 exhibited a toxicity profile similar to other monomethyl auristatin E-based ADCs. These results highlight the potential of MYTX-011 for treating a broader range of patients with NSCLC with c-MET expression than other c-MET-targeting ADCs. A first-in-human study is ongoing to determine the safety, tolerability, and preliminary efficacy of MYTX-011 in patients with NSCLC (NCT05652868).

MYTX-011: a pH-dependent anti-cMET antibody-drug conjugate designed for enhanced payload delivery to cMET expressing tumor cells.

Advances in linker payload technology and target selection have been at the forefront of recent improvements in antibody-drug conjugate (ADC) design, leading to several approvals over the last decade. In contrast, the potential of novel ADC technologies to enhance payload delivery to tumors is relatively underexplored. We demonstrate that incorporation of pH-dependent binding in the antibody component of a cMET targeting ADC (MYTX-011) can overcome the requirement for high cMET expression on tumors, an innovation that has the potential to benefit a broader population of patients with lower cMET levels. MYTX-011 drove four-fold higher net internalization than a non-pH engineered parent ADC in non-small cell lung cancer (NSCLC) cells and showed increased cytotoxicity against a panel of cell lines from various solid tumors. A single dose of MYTX-011 showed at least three-fold higher efficacy than a benchmark ADC in mouse xenograft models of NSCLC ranging from low to high cMET expression. Moreover, MYTX-011 showed improved pharmacokinetics over parent and benchmark ADCs. In a repeat dose toxicology study, MYTX-011 exhibited a toxicity profile similar to other MMAE-based ADCs. These results highlight the potential of MYTX-011 for treating a broader range of NSCLC patients with cMET expression than other cMET targeting ADCs. A first in human study is ongoing to determine the safety, tolerability, and preliminary efficacy of MYTX-011 in patients with NSCLC (NCT05652868).

S100A8/A9 predicts response to PIM kinase and PD-1/PD-L1 inhibition in triple-negative breast cancer mouse models.

BACKGROUND: Understanding why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well remains a challenge. This study aims to understand the potential underlying mechanisms distinguishing early-stage TNBC tumors that respond to clinical intervention from non-responders, as well as to identify clinically viable therapeutic strategies, specifically for TNBC patients who may not benefit from existing therapies. METHODS: We conducted retrospective bioinformatics analysis of historical gene expression datasets to identify a group of genes whose expression levels in early-stage tumors predict poor clinical outcomes in TNBC. In vitro small-molecule screening, genetic manipulation, and drug treatment in syngeneic mouse models of TNBC were utilized to investigate potential therapeutic strategies and elucidate mechanisms of drug action. RESULTS: Our bioinformatics analysis reveals a robust association between increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors and subsequent disease progression in TNBC. A targeted small-molecule screen identifies PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Notably, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC. CONCLUSIONS: Our data propose S100A8/A9 as a potential predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC. This work encourages the development of S100A8/A9-based liquid biopsy tests for treatment guidance.

Breast cancer is a complex disease, and not all patients respond well to existing treatments. In this study, we sought to understand why some patients with a specific type of breast cancer called triple-negative breast cancer respond poorly to current therapies. We also aimed to identify new treatments for these patients. We analyzed genetic data from breast cancer patients and identified a factor called S100A8/A9, which is linked to poor outcomes in early-stage cancer. We tested drugs that can reduce the levels of this factor in tumors and found promising results, especially when combined with another treatment called immunotherapy. Our findings suggest that S100A8/A9 could help predict how patients will respond to treatments, potentially leading to better therapies in the future.

S100A8/A9 predicts triple-negative breast cancer response to PIM kinase and PD-1/PD-L1 inhibition.

It remains elusive why some triple-negative breast cancer (TNBC) patients respond poorly to existing therapies while others respond well. Our retrospective analysis of historical gene expression datasets reveals that increased expression of immunosuppressive cytokine S100A8/A9 in early-stage tumors is robustly associated with subsequent disease progression in TNBC. Although it has recently gained recognition as a potential anticancer target, S100A8/A9 has not been integrated into clinical study designs evaluating molecularly targeted therapies. Our small molecule screen has identified PIM kinase inhibitors as capable of decreasing S100A8/A9 expression in multiple cell types, including TNBC and immunosuppressive myeloid cells. Furthermore, combining PIM inhibition and immune checkpoint blockade induces significant antitumor responses, especially in otherwise resistant S100A8/A9-high PD-1/PD-L1-positive tumors. Importantly, serum S100A8/A9 levels mirror those of tumor S100A8/A9 in a syngeneic mouse model of TNBC. Thus, our data suggest that S100A8/A9 could be a predictive and pharmacodynamic biomarker in clinical trials evaluating combination therapy targeting PIM and immune checkpoints in TNBC and encourage the development of S100A8/A9-based liquid biopsy tests.

Metixene is an incomplete autophagy inducer in preclinical models of metastatic cancer and brain metastases.

A paucity of chemotherapeutic options for metastatic brain cancer limits patient survival and portends poor clinical outcomes. Using a CNS small-molecule inhibitor library of 320 agents known to be blood-brain barrier permeable and approved by the FDA, we interrogated breast cancer brain metastasis vulnerabilities to identify an effective agent. Metixene, an antiparkinsonian drug, was identified as a top therapeutic agent that was capable of decreasing cellular viability and inducing cell death across different metastatic breast cancer subtypes. This agent significantly reduced mammary tumor size in orthotopic xenograft assays and improved survival in an intracardiac model of multiorgan site metastases. Metixene further extended survival in mice bearing intracranial xenografts and in an intracarotid mouse model of multiple brain metastases. Functional analysis revealed that metixene induced incomplete autophagy through N-Myc downstream regulated 1 (NDRG1) phosphorylation, thereby leading to caspase-mediated apoptosis in both primary and brain-metastatic cells, regardless of cancer subtype or origin. CRISPR/Cas9 KO of NDRG1 led to autophagy completion and reversal of the metixene apoptotic effect. Metixene is a promising therapeutic agent against metastatic brain cancer, with minimal reported side effects in humans, which merits consideration for clinical translation.

Targeting BET Proteins Decreases Hyaluronidase-1 in Pancreatic Cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is characterized by the presence of dense stroma that is enriched in hyaluronan (HA), with increased HA levels associated with more aggressive disease. Increased levels of the HA-degrading enzymes hyaluronidases (HYALs) are also associated with tumor progression. In this study, we evaluate the regulation of HYALs in PDAC. METHODS: Using siRNA and small molecule inhibitors, we evaluated the regulation of HYALs using quantitative real-time PCR (qRT-PCR), Western blot analysis, and ELISA. The binding of BRD2 protein on the HYAL1 promoter was evaluated by chromatin immunoprecipitation (ChIP) assay. Proliferation was evaluated by WST-1 assay. Mice with xenograft tumors were treated with BET inhibitors. The expression of HYALs in tumors was analyzed by immunohistochemistry and by qRT-PCR. RESULTS: We show that HYAL1, HYAL2, and HYAL3 are expressed in PDAC tumors and in PDAC and pancreatic stellate cell lines. We demonstrate that inhibitors targeting bromodomain and extra-terminal domain (BET) proteins, which are readers of histone acetylation marks, primarily decrease HYAL1 expression. We show that the BET family protein BRD2 regulates HYAL1 expression by binding to its promoter region and that HYAL1 downregulation decreases proliferation and enhances apoptosis of PDAC and stellate cell lines. Notably, BET inhibitors decrease the levels of HYAL1 expression in vivo without affecting the levels of HYAL2 or HYAL3. CONCLUSIONS: Our results demonstrate the pro-tumorigenic role of HYAL1 and identify the role of BRD2 in the regulation of HYAL1 in PDAC. Overall, these data enhance our understanding of the role and regulation of HYAL1 and provide the rationale for targeting HYAL1 in PDAC.

Checkpoint kinase 1/2 inhibition potentiates anti-tumoral immune response and sensitizes gliomas to immune checkpoint blockade.

Whereas the contribution of tumor microenvironment to the profound immune suppression of glioblastoma (GBM) is clear, tumor-cell intrinsic mechanisms that regulate resistance to CD8 T cell mediated killing are less understood. Kinases are potentially druggable targets that drive tumor progression and might influence immune response. Here, we perform an in vivo CRISPR screen to identify glioma intrinsic kinases that contribute to evasion of tumor cells from CD8 T cell recognition. The screen reveals checkpoint kinase 2 (Chek2) to be the most important kinase contributing to escape from CD8 T-cell recognition. Genetic depletion or pharmacological inhibition of Chek2 with blood-brain-barrier permeable drugs that are currently being evaluated in clinical trials, in combination with PD-1 or PD-L1 blockade, lead to survival benefit in multiple preclinical glioma models. Mechanistically, loss of Chek2 enhances antigen presentation, STING pathway activation and PD-L1 expression in mouse gliomas. Analysis of human GBMs demonstrates that Chek2 expression is inversely associated with antigen presentation and T-cell activation. Collectively, these results support Chek2 as a promising target for enhancement of response to immune checkpoint blockade therapy in GBM.

Low-level whole-brain radiation enhances theranostic potential of single-domain antibody fragments for human epidermal growth factor receptor type 2 (HER2)-positive brain metastases.

Background: Single-domain antibody fragments (aka VHH, ~ 13 kDa) are promising delivery systems for brain tumor theranostics; however, achieving efficient delivery of VHH to intracranial lesions remains challenging due to the tumor-brain barrier. Here, we evaluate low-dose whole-brain irradiation as a strategy to increase the delivery of an anti- human epidermal growth factor receptor type 2 (HER2) VHH to breast cancer-derived intracranial tumors in mice. Methods: Mice with intracranial HER2-positive BT474BrM3 tumors received 10-Gy fractionated cranial irradiation and were evaluated by noninvasive imaging. Anti-HER2 VHH 5F7 was labeled with 18F, administered intravenously to irradiated mice and controls, and PET/CT imaging was conducted periodically after irradiation. Tumor uptake of 18F-labeled 5F7 in irradiated and control mice was compared by PET/CT image analysis and correlated with tumor volumes. In addition, longitudinal dynamic contrast-enhanced MRI (DCE-MRI) was conducted to visualize and quantify the potential effects of radiation on tumor perfusion and permeability. Results: Increased 18F-labeled 5F7 intracranial tumor uptake was observed with PET in mice receiving cranial irradiation, with maximum tumor accumulation seen approximately 12 days post initial radiation treatment. No radiation-induced changes in HER2 expression were detected by Western blot, flow cytometry, or on tissue sections. DCE-MRI imaging demonstrated transiently increased tumor perfusion and permeability after irradiation, consistent with the higher tumor uptake of 18F-labeled anti-HER2 5F7 in irradiated mice. Conclusion: Low-level brain irradiation induces dynamic changes in tumor vasculature that increase the intracranial tumor delivery of an anti-HER2 VHH, which could facilitate the use of radiolabeled VHH to detect, monitor, and treat HER2-expressing brain metastases.

Translocon-associated Protein Subunit SSR3 Determines and Predicts Susceptibility to Paclitaxel in Breast Cancer and Glioblastoma.

PURPOSE: Paclitaxel (PTX) is one of the most potent and commonly used chemotherapies for breast and pancreatic cancer. Several ongoing clinical trials are investigating means of enhancing delivery of PTX across the blood-brain barrier for glioblastomas. Despite the widespread use of PTX for breast cancer, and the initiative to repurpose this drug for gliomas, there are no predictive biomarkers to inform which patients will likely benefit from this therapy. EXPERIMENTAL DESIGN: To identify predictive biomarkers for susceptibility to PTX, we performed a genome-wide CRISPR knockout (KO) screen using human glioma cells. The genes whose KO was most enriched in the CRISPR screen underwent further selection based on their correlation with survival in the breast cancer patient cohorts treated with PTX and not in patients treated with other chemotherapies, a finding that was validated on a second independent patient cohort using progression-free survival. RESULTS: Combination of CRISPR screen results with outcomes from patients with taxane-treated breast cancer led to the discovery of endoplasmic reticulum (ER) protein SSR3 as a putative predictive biomarker for PTX. SSR3 protein levels showed positive correlation with susceptibility to PTX in breast cancer cells, glioma cells, and in multiple intracranial glioma xenografts models. KO of SSR3 turned the cells resistant to PTX while its overexpression sensitized the cells to PTX. Mechanistically, SSR3 confers susceptibility to PTX through regulation of phosphorylation of ER stress sensor IRE1α. CONCLUSIONS: Our hypothesis generating study showed SSR3 as a putative biomarker for susceptibility to PTX, warranting its prospective clinical validation.

Repurposing autophagy regulators in brain tumors.

Malignant brain tumors, such as glioblastoma multiforme (GBM) and brain metastases, continue to be an unmet medical challenge. Despite advances in cancer diagnostics and therapeutics, tumor cell colonization in the central nervous system renders most treatment options ineffective. This is primarily due to the selective permeability of the blood-brain barrier (BBB), which hinders the crossing of targeting agents into the brain. As such, repositioning medications that demonstrate anticancer effects and possess the ability to cross the BBB can be a promising option. Antidepressants, which are BBB-permeable, have been reported to exhibit cytotoxicity against tumor cells. Autophagy, specifically, has been identified as one of the common key mediators of antidepressant's antitumor effects. In this work, we provide a comprehensive overview of US Food and Drug Administration (FDA)-approved antidepressants with reported cytotoxic activities in different tumor models, where autophagy dysregulation was demonstrated to play the main part. As such, imipramine, maprotiline, fluoxetine and escitalopram were shown to induce autophagy, whereas nortriptyline, clomipramine and paroxetine were identified as autophagy inhibitors. Sertraline and desipramine, depending on the neoplastic context, were demonstrated to either induce or inhibit autophagy. Collectively, these medications were associated with favorable therapeutic outcomes in a variety of cancer cell models, including brain tumors.

Combination of tucatinib and neural stem cells secreting anti-HER2 antibody prolongs survival of mice with metastatic brain cancer.

Brain metastases are a leading cause of death in patients with breast cancer. The lack of clinical trials and the presence of the blood-brain barrier limit therapeutic options. Furthermore, overexpression of the human epidermal growth factor receptor 2 (HER2) increases the incidence of breast cancer brain metastases (BCBM). HER2-targeting agents, such as the monoclonal antibodies trastuzumab and pertuzumab, improved outcomes in patients with breast cancer and extracranial metastases. However, continued BCBM progression in breast cancer patients highlighted the need for novel and effective targeted therapies against intracranial metastases. In this study, we engineered the highly migratory and brain tumor tropic human neural stem cells (NSCs) LM008 to continuously secrete high amounts of functional, stable, full-length antibodies against HER2 (anti-HER2Ab) without compromising the stemness of LM008 cells. The secreted anti-HER2Ab impaired tumor cell proliferation in vitro in HER2+ BCBM cells by inhibiting the PI3K-Akt signaling pathway and resulted in a significant benefit when injected in intracranial xenograft models. In addition, dual HER2 blockade using anti-HER2Ab LM008 NSCs and the tyrosine kinase inhibitor tucatinib significantly improved the survival of mice in a clinically relevant model of multiple HER2+ BCBM. These findings provide compelling evidence for the use of HER2Ab-secreting LM008 NSCs in combination with tucatinib as a promising therapeutic regimen for patients with HER2+ BCBM.

Synergistic PIM kinase and proteasome inhibition as a therapeutic strategy for MYC-overexpressing triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the breast cancer subtype with the poorest clinical outcome. The PIM family of kinases has emerged as a factor that is both overexpressed in TNBC and associated with poor outcomes. Preclinical data suggest that TNBC with an elevated MYC expression is sensitive to PIM inhibition. However, clinical observations indicate that the efficacy of PIM inhibitors as single agents may be limited, suggesting the need for combination therapies. Our screening effort identifies PIM and the 20S proteasome inhibition as the most synergistic combination. PIM inhibitors, when combined with proteasome inhibitors, induce significant antitumor effects, including abnormal accumulation of poly-ubiquitinated proteins, increased proteotoxic stress, and the inability of NRF1 to counter loss in proteasome activity. Thus, the identified combination could represent a rational combination therapy against MYC-overexpressing TNBC that is readily translatable to clinical investigations.

FKBP1A upregulation correlates with poor prognosis and increased metastatic potential of HNSCC.

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common malignancy globally. The etiology of HNSCC is multifactorial, including cellular stress induced by a tobacco smoking, tobacco chewing excess alcohol consumption, and human papillomavirus infection. The induction of stress includes autophagy as one of the response pathways in maintaining homeostatic equilibrium. We evaluated the expression of autophagy-related genes in HNSCC tissues from RNA sequencing datasets and identified 19 genes correlated with poor prognosis and 18 genes correlated with improved prognosis of HNSCC patients. Further analysis of independent gene expression datasets revealed that ATG12, HSP90AB1, and FKBP1A are overexpressed in HNSCC and correlate with poor prognosis, whereas the overexpression of ANXA1, FOS, and ULK3 correlates with improved prognosis. Using independent datasets, we also found that ATG12, HSP90AB1, and FKBP1A expression increased with an increase in the T-stage of HNSCC. Among all the datasets analyzed, FKBP1A was overexpressed in HNSCC and was strongly associated with lymph node metastasis in multiple in silico datasets. In conclusion, our analysis indicates dynamic alterations in autophagy genes during HNSCC and warrants further investigation, specifically on FKBP1A and its role in tumor progression and metastasis.

The Network of Cytokines in Brain Metastases.

Brain metastases are the most common of all intracranial tumors and a major cause of death in patients with cancer. Cytokines, including chemokines, interferons, interleukins, lymphokines, and tumor necrosis factors are key regulators in the formation of brain metastases. They regulate the infiltration of different cellular subsets into the tumor microenvironment and affect the therapeutic outcomes in patients. Elucidating the cancer cell-cytokine interactions in the setting of brain metastases is crucial for the development of more accurate diagnostics and efficacious therapies. In this review, we focus on cytokines that are found in the tumor microenvironment of brain metastases and elaborate on their trends of expression, regulation, and roles in cellular recruitment and tumorigenesis. We also explore how cytokines can alter the anti-tumor response in the context of brain metastases and discuss ways through which cytokine networks can be manipulated for diagnosis and treatment.

BET inhibition increases ßIII-tubulin expression and sensitizes metastatic breast cancer in the brain to vinorelbine.

Metastases from primary breast cancer result in poor survival. ßIII-tubulin (TUBB3) has been established as a therapeutic target for breast cancer metastases specifically to the brain. In this study, we conducted a systematic analysis to determine the regulation of TUBB3 expression in breast cancer metastases to the brain and strategically target these metastases using vinorelbine (VRB), a drug approved by the U.S. Food and Drug Administration (FDA). We found that human epidermal growth factor receptor 2 (HER2) signaling regulates TUBB3 expression in both trastuzumab-sensitive and trastuzumab-resistant neoplastic cells. We further discovered that bromodomain and extra-terminal domain (BET) inhibition increases TUBB3 expression, rendering neoplastic cells more susceptible to apoptosis by VRB. Orthotopic xenograft assays using two different breast cancer cell models revealed a reduction in tumor volume with BET inhibition and VRB treatment. In addition, in vivo studies using a model of multiple brain metastasis (BM) showed improved survival with the combination of radiation + BET inhibitor (iBET-762) + VRB (75% long-term survivors, P < 0.05). Using in silico analysis and BET inhibition, we found that the transcription factor myeloid zinc finger-1 (MZF-1) protein binds to the TUBB3 promoter. BET inhibition decreases MZF-1 expression and subsequently increases TUBB3 expression. Overexpression of MZF-1 decreases TUBB3 expression and reduces BM in vivo, whereas its knockdown increases TUBB3 expression in breast cancer cells. In summary, this study demonstrates a regulatory mechanism of TUBB3 and provides support for an application of BET inhibition to sensitize breast cancer metastases to VRB-mediated therapy.

Genes that Mediate Metastasis across the Blood-Brain Barrier.

Brain metastasis is an important cause of mortality in patients with cancer and represents the majority of all intracranial tumors. A key step during the metastatic journey of the cancer cell to the brain is the invasion through the blood-brain barrier (BBB). Nevertheless, the molecular mechanisms that govern this process remain unknown. The BBB has been blamed for limiting the access of therapeutic drugs to the brain, which provides a safe haven for cancer cells in the brain and confers poor prognosis for the patient. Here, we explore the genes that control the transmigration of metastatic cancer cells across the BBB, offering new targets for the development of gene and cell therapies against brain metastases.

Landscape of combination therapy trials in breast cancer brain metastasis.

Combination therapy has become a cornerstone in cancer treatment to potentiate therapeutic effectiveness and overcome drug resistance and metastasis. In this work, we explore combination trials in breast cancer brain metastasis (BCBM), highlighting deficiencies in trial design and underlining promising combination strategies. On October 31, 2019, we examined ClinicalTrials.gov for interventional and therapeutic clinical trials involving combination therapy for BCBM, without limiting for date or location. Information on trial characteristics was collected. Combination therapies used in trials were analyzed and explored in line with evidence from the medical literature. Sixty-five combination therapy trials were selected (n = 65), constituting less than 0.7% of all breast cancer trials. Most trials (62%) combined ≥2 chemotherapeutic agents. Chemotherapy with radiation was main-stay in 23% of trials. Trastuzumab was mostly used in combination (31%), followed by lapatinib (20%) and capecitabine (15%). Common strategies involved combining tyrosine kinase inhibitors with thymidylate synthase inhibitors (6 trials), dual HER-dimerization inhibitors (3 trials), microtubule inhibitors and tyrosine kinase inhibitors (3 trials), and HER-dimerization inhibitors and tyrosine kinase inhibitors (3 trials). The combination of tucatinib and capecitabine yielded the highest objective response rate (83%) in early phase trials. The triple combination of trastuzumab, tucatinib and capecitabine lowered the risk of disease progression or death by 52% in patients with HER2-positive BCBM. Combining therapeutic agents based on biological mechanisms is necessary to increase the effectiveness of available anti-cancer regimens. Significant survival benefit has yet to be achieved in future combination therapy trials. Enhancing drug delivery through blood-brain barrier permeable agents may potentiate the overall therapeutic outcomes.

GCN2 is essential for CD8+ T cell survival and function in murine models of malignant glioma.

Amino acid deprivation is a strategy that malignancies utilize to blunt anti-tumor T-cell immune responses. It has been proposed that amino acid insufficiency in T-cells is detected by GCN2 kinase, which through phosphorylation of EIF2α, shuts down global protein synthesis leading to T-cell arrest. The role of this amino acid stress sensor in the context of malignant brain tumors has not yet been studied, and may elucidate important insights into the mechanisms of T-cell survival in this harsh environment. Using animal models of glioblastoma and animals with deficiency in GCN2, we explored the importance of this pathway in T-cell function within brain tumors. Our results show that GCN2 deficiency limited CD8+ T-cell activation and expression of cytotoxic markers in two separate murine models of glioblastoma in vivo. Importantly, adoptive transfer of antigen-specific T-cells from GCN2 KO mice did not control tumor burden as well as wild-type CD8+ T-cells. Our in vitro and in vivo data demonstrated that reduction in amino acid availability caused GCN2 deficient CD8+ T-cells to become rapidly necrotic. Mechanistically, reduced CD8+ T-cell activation and necrosis was due to a disruption in TCR signaling, as we observed reductions in PKCθ and phoshpo-PKCθ on CD8+ T-cells from GCN2 KO mice in the absence of tryptophan. Validating these observations, treatment of wild-type CD8+ T-cells with a downstream inhibitor of GCN2 activation also triggered necrosis of CD8+ T-cells in the absence of tryptophan. In conclusion, our data demonstrate the vital importance of intact GCN2 signaling on CD8+ T-cell function and survival in glioblastoma.

Therapeutic targeting of tumor-associated myeloid cells synergizes with radiation therapy for glioblastoma.

Tumor-associated myeloid cells (TAMCs) are key drivers of immunosuppression in the tumor microenvironment, which profoundly impedes the clinical response to immune-dependent and conventional therapeutic modalities. As a hallmark of glioblastoma (GBM), TAMCs are massively recruited to reach up to 50% of the brain tumor mass. Therefore, they have recently been recognized as an appealing therapeutic target to blunt immunosuppression in GBM with the hope of maximizing the clinical outcome of antitumor therapies. Here we report a nano-immunotherapy approach capable of actively targeting TAMCs in vivo. As we found that programmed death-ligand 1 (PD-L1) is highly expressed on glioma-associated TAMCs, we rationally designed a lipid nanoparticle (LNP) formulation surface-functionalized with an anti-PD-L1 therapeutic antibody (αPD-L1). We demonstrated that this system (αPD-L1-LNP) enabled effective and specific delivery of therapeutic payload to TAMCs. Specifically, encapsulation of dinaciclib, a cyclin-dependent kinase inhibitor, into PD-L1-targeted LNPs led to a robust depletion of TAMCs and an attenuation of their immunosuppressive functions. Importantly, the delivery efficiency of PD-L1-targeted LNPs was robustly enhanced in the context of radiation therapy (RT) owing to the RT-induced up-regulation of PD-L1 on glioma-infiltrating TAMCs. Accordingly, RT combined with our nano-immunotherapy led to dramatically extended survival of mice in 2 syngeneic glioma models, GL261 and CT2A. The high targeting efficiency of αPD-L1-LNP to human TAMCs from GBM patients further validated the clinical relevance. Thus, this study establishes a therapeutic approach with immense potential to improve the clinical response in the treatment of GBM and warrants a rapid translation into clinical practice.

Current state of clinical trials in breast cancer brain metastases.

BACKGROUND: Breast cancer brain metastases (BCBM) are the final frontier in neuro-oncology for which more efficacious therapies are required. In this work, we explore clinical trials in BCBM, and determine the shortcomings in the development of new BCBM therapies to shed light on potential areas for enhancement. METHODS: On July 9, 2018, we searched ClinicalTrials.gov for all interventional and therapeutic clinical trials involving BCBM, without limiting for date or location. Information on trial characteristics, including phase, status, start and end dates, study design, primary endpoints, selection criteria, sample size, experimental interventions, results, and publications were collected and analyzed. RESULTS: Fifty-three trials fulfilled the selection criteria. Median trial duration across phases ranged between 3 and 6 years. More than half of the trials were conducted in the United States. Although 94% of the trials were in early phases (I-II), 20% of patients were in phase III trials. Two phase III trials were anteceded by phase II trials that were non-randomized; one reported positive results. Approximately one-third of the trials were completed, whereas 23% of trials were terminated early; mostly due to inadequate enrollment. Only 13% of all trials and 22% of completed trials had published results directly linked to their primary outcomes. CONCLUSIONS: The low number of trials and accrual numbers, the lack of diversity, and the scarcity of published results represent the main troubles in clinical BCBM research. Optimization of BCBM trials is necessary to achieve effective therapies.