Metastatic Brain Tumors Research Articles

Diagnosis of brain metastasis due to lung cancer and affecting factors at “Dr. Cipto Mangunkusumo” General Hospital

Background and objectives. The incidence of brain metastases is higher than primary brain tumors, with lung cancer as a common etiology at “Dr. Cipto Mangunkusumo” General Hospital. Delay in diagnosis can cause brain herniation, resulting in disability and death. We aimed to investigate the compatibility between daily clinical practice and clinical practice guidelines for diagnosing brain metastases due to lung cancer at “Dr. Cipto Mangunkusumo” General Hospital while also examining factors that might influence the duration of the diagnosis. Materials and methods. We conducted a retrospective cohort study to determine the conformity between the duration of diagnosis of metastatic brain tumors due to lung cancer in daily clinical practice with clinical practice guidelines. Secondary data was obtained from medical records from November 2021 until June 2022. Results. Twelve subjects (30%) were diagnosed with brain metastases from lung cancer within two weeks with a median duration of 18.5 days (IQR 12-34 days). The duration of 7 days (IQR 4-11 days) was required to obtain a lung mass, 8 days (IQR 4.5-13 days) to perform a biopsy, and 6 days (IQR 3.5-7 days) to obtain t pathology results. No statistically significant relationship exists between the variables assessed and the duration of diagnosis. Conclusions. The clinical practice guidelines at “Dr. Cipto Mangunkusumo” General Hospital for diagnosing brain metastases from lung cancer within two weeks could only be carried out in 30% of subjects in this study. Collaboration between departments is needed to make the diagnosis faster.

Neuro-oncology anywhere: A decentralized approach to clinical trials in brain tumors and beyond.

TPS1647 Background: The majority of patients with primary and secondary central nervous system (CNS) malignancy develop cognitive impairment, fatigue, and mood-related symptoms. Radiotherapy has been shown to contribute to symptom burden often limiting quality of life and functional status. The development of interventions mitigating neurocognitive toxicity requires an accurate assessment of function and symptom burden. Formal neuropsychological evaluation is resource and time intensive, and often challenging to incorporate in routine clinical practice. There is a critical need to accurately assess cognition without causing undue burden to cancer patients while evaluating the efficacy of interventions that can be scaled and implemented at a population level. Methods: To adequately assess the neurocognitive function and related symptoms in patients with CNS malignancy we have designed an open-label decentralized clinical trial that will randomize patients who received intracranial radiation for primary or metastatic brain tumors in a 1:1 allocation to a therapy targeting radiation-related toxicity (metformin shipped to patient home) plus health promotion with a wearable device vs. health promotion with a wearable device alone. Participants will be stratified based on tumor type (glioblastoma vs. other glioma vs. brain metastases vs. meningioma) and age (<70 vs. 70+ years). Participants will be provided a wearable device for monitoring health status. Participants will undergo serial remote cognitive assessments with the Mayo Test Development Through Rapid Iteration, Validation and Expansion platform (Mayo Test Drive). Remote reported symptom collection via patient surveys and remote neurologic examination by telehealth will also be incorporated. Cognitive assessments and symptom surveys will be designed for completion on a smartphone, tablet, or computer device. Health data will be collected from the wearable device, including the number of steps per day and sleep quality/duration. Participants receiving metformin will utilize device apps to report medication adherence and adverse events. Study-related laboratory assessments will be completed remotely and transmitted electronically. This decentralized clinical trial will provide real-world cognitive and quality-of-life data for patients with primary and metastatic brain tumors while providing preliminary data on the effectiveness of device-based health promotion with or without metformin for treating radiation-related cognitive decline. Results gained from this study will guide future trials in neuro-oncology and other fields. This study is expected to open in March 2024.

Evaluating the glymphatic system via magnetic resonance diffusion tensor imaging along the perivascular spaces in brain tumor patients

PurposeTo investigate glymphatic system function in patients with brain tumors, including both primary and secondary tumors, using diffusion tensor imaging along perivascular spaces (DTI-ALPS).MethodsWe retrospectively analyzed the MR DTI of 24 patients with unilateral brain tumors and compared them with age and sex-matched controls. We compared the DTI-ALPS index of the ipsi- and contralateral brain hemispheres. The region of interest was placed in the periventricular vessels adjacent to the lateral ventricles. Differences between sex, age, and kind of tumor (primary or brain metastasis) were evaluated. Correlations between DTI-ALPS index and age and the tumor's apparent diffusion coefficient (ADC) were also investigated.ResultsThe DTI-ALPS index was significantly lower (p < 0.05) in the tumor-affected hemisphere (mean = 1.26 ± 0.24) than contralateral (mean = 1.43 ± 0.28). A comparison with healthy controls revealed no significant difference on the matched ipsilateral side. However, the DTI-ALPS index of the contralateral side of the patients was larger than the HC. Additionally, no statistically significant differences were found when analyzing the DTI-ALPS index vs. age, sex, and tumor entity. Additionally, we did not find a correlation between the DTI-ALPS index and patient age or tumor ADC.ConclusionThe decreased DTI-ALPS index in the tumor-affected hemisphere may be related to impaired glymphatic system function. However, cancer is often a systemic disease; thus, the DTI-ALPS index from the contralateral brain hemisphere may not generally be considered as a normal control. Nonetheless, the DTI-ALPS index does not only reflect diffusion in the perivascular spaces but it can also be influenced by factors such as axonal degeneration. Therefore, it does not directly reflect brain waste clearance and changes in the index should be interpreted carefully.

Current Progress in Magnetic Resonance-Guided Focused Ultrasound to Facilitate Drug Delivery across the Blood-Brain Barrier.

This review discusses the current progress in the clinical use of magnetic resonance-guided focused ultrasound (MRgFUS) and other ultrasound platforms to transiently permeabilize the blood-brain barrier (BBB) for drug delivery in neurological disorders and neuro-oncology. Safety trials in humans have followed on from extensive pre-clinical studies, demonstrating a reassuring safety profile and paving the way for numerous translational clinical trials in Alzheimer's disease, Parkinson's disease, and primary and metastatic brain tumors. Future directions include improving ultrasound delivery devices, exploring alternative delivery approaches such as nanodroplets, and expanding the application to other neurological conditions.

Deep learning ensembles for detecting brain metastases in longitudinal multi-modal MRI studies

Metastatic brain cancer is a condition characterized by the migration of cancer cells to the brain from extracranial sites. Notably, metastatic brain tumors surpass primary brain tumors in prevalence by a significant factor, they exhibit an aggressive growth potential and have the capacity to spread across diverse cerebral locations simultaneously. Magnetic resonance imaging (MRI) scans of individuals afflicted with metastatic brain tumors unveil a wide spectrum of characteristics. These lesions vary in size and quantity, spanning from tiny nodules to substantial masses captured within MRI. Patients may present with a limited number of lesions or an extensive burden of hundreds of them. Moreover, longitudinal studies may depict surgical resection cavities, as well as areas of necrosis or edema. Thus, the manual analysis of such MRI scans is difficult, user-dependent and cost-inefficient, and – importantly – it lacks reproducibility. We address these challenges and propose a pipeline for detecting and analyzing brain metastases in longitudinal studies, which benefits from an ensemble of various deep learning architectures originally designed for different downstream tasks (detection and segmentation). The experiments, performed over 275 multi-modal MRI scans of 87 patients acquired in 53 sites, coupled with rigorously validated manual annotations, revealed that our pipeline, built upon open-source tools to ensure its reproducibility, offers high-quality detection, and allows for precisely tracking the disease progression. To objectively quantify the generalizability of models, we introduce a new data stratification approach that accommodates the heterogeneity of the dataset and is used to elaborate training-test splits in a data-robust manner, alongside a new set of quality metrics to objectively assess algorithms. Our system provides a fully automatic and quantitative approach that may support physicians in a laborious process of disease progression tracking and evaluation of treatment efficacy.

Characteristics of Adult Brain Tumors in Neurology Emergency Unit in Prof. Dr. I.G.N.G. Ngoerah Hospital Bali 2020-2022

Characteristics of Adult Brain Tumors in Neurology Emergency Unit in Prof. Dr. I.G.N.G. Ngoerah Hospital Bali 2020-2022

So what I'm stressed? A qualitative study examining caregivers' reactions to emerging biomarkers of stress

BackgroundCaregivers of adults with cancer often report significant distress yet remain difficult to engage in supportive services. While the field of Psychosomatic Medicine has continued to identify important markers of physiologic stress, and demonstrated disruption in these markers in caregiver populations, no research has investigated whether biomarker information on caregivers’ reaction to stress could impact their willingness to address their ongoing distress. MethodsHere, we report on a qualitative study (N = 17) in which we conducted individual interviews with cancer caregivers to explore their key attitudes towards, and subjective experience of, mock stress biomarker data. A total of 17 caregivers of patients (M age = 56.1 years; SD = 12.3) with primarily metastatic brain tumors (glioblastoma) were interviewed regarding four commercially available biomarkers (telomere length; hair cortisol, activity levels and heart rate variability). Once presented with information about stress biomarkers, caregivers were asked to discuss their subjective reaction as if it was their own data as well as their motivation and willingness to seek support after receiving such information. We identified and extracted relevant themes. ResultsAnalysis utilizing the framework method revealed four emerging themes. The first theme described caregivers' ability to manage stress and willingness to engage with supportive services. Second, caregivers generally accepted the biomarker data but preferred it to be presented in a specific way. The third theme demonstrated that for some, biomarker data may actually increase their subjective distress (e.g., whether or not something could be done to improve their mental state). The last theme described how biomarkers were generally received as meaningful motivators that could increase caregivers’ willingness to engage with supportive services. ConclusionsIn addition to the more general identified theme of CG's willingness to engage with additional support, we gained insights into caregivers' reaction to the stress biomarkers presented. Findings will set the stage for the utility of stress biomarker information and whether it influences cancer caregivers' willingness to address their distress and motivation to engage in supportive services.

Targeting the HSP47-collagen axis inhibits brain metastasis by reversing M2 microglial polarization and restoring anti-tumor immunity

Brain metastases (BrMs) are the leading cause of death in patients with solid cancers. BrMs exhibit a highly immunosuppressive milieu and poor response to immunotherapies; however, the underlying mechanism remains largely unclear. Here, we show that upregulation of HSP47 in tumor cells drives metastatic colonization and outgrowth in the brain by creating an immunosuppressive microenvironment. HSP47-mediated collagen deposition in the metastatic niche promotes microglial polarization to the M2 phenotype via the α2β1 integrin/nuclear factor κB pathway, which upregulates the anti-inflammatory cytokines and represses CD8+ Tcell anti-tumor responses. Depletion of microglia reverses HSP47-induced inactivation of CD8+ Tcells and abolishes BrM. Col003, an inhibitor disrupting HSP47-collagen association restores an anti-tumor immunity and enhances the efficacy of anti-PD-L1 immunotherapy in BrM-bearing mice. Our study supports that HSP47 is a critical determinant of M2 microglial polarization and immunosuppression and that blocking the HSP47-collagen axis represents a promising therapeutic strategy against brain metastatic tumors.

Comparison of Diffusion MRI Findings of High-Graded Primary Brain Tumors and Metastatic Brain Tumors

Aim: Glioblastomas are the highest grade and most mortal primary brain tumors. Cerebral masses that occur with the metastasis of cancers of tissues other than brain are included in the differential diagnosis of glioblastomas. This study aimed to compare the diffusion-weighted imaging signal characteristics of primary and metastatic brain masses and to describe the findings that may be useful in the differential diagnosis. Material and Methods: Patients with pathologically diagnosed glioblastoma and patients with pathologically diagnosed metastases or radiologically diagnosed brain metastases were included in the study. Diffusion-weighted imaging signal properties in magnetic resonance imaging examinations obtained with a 1.5 Tesla scanner were retrospectively analyzed. The signal features and short and long diameters of the lesions were measured and compared in both patient groups. Results: A total of 54 patients, 24 glioblastomas, and 30 brain metastases were included in the study. The most common signal feature of diffusion-weighted imaging in the glioblastoma group was heterogeneous hyper- and hypointense areas observed in 20 (83.3%) patients. The most common signal feature in the metastasis group was the peripheral hyperintense ring and central hypointense signal in 16 (53.3%) patients. There was no significant relation found between the number of lesions and the primary brain tumor and metastases. Conclusion: Although only signal characteristics are used without quantitative assessment in diffusion-weighted imaging, it may be helpful in the differential diagnosis of primary and metastatic brain masses. It is important to remember that the masses in the two groups can have comparable signal properties.

Randomized self-controlled study comparing open-face vs. closed immobilization masks in fractionated cranial radiotherapy

PurposeTo compare patient discomfort and immobilisation performance of open-face and closed immobilization masks in cranial radiotherapy. Material and methodsThis was a single-center randomized self-controlled clinical trial. At CT simulation, an open-face and closed mask was made for each patient and treatment plans with identical dose prescription were generated for each mask. Patients were randomised to start treatment with an open-face or closed mask. Masks were switched halfway through the treatment course; every patient was their own control. Patients self-reported discomfort, anxiety and pain using the visual analogue scale (VAS). Inter- and intrafraction set-up variability was measured with planar kV imaging and a surface guided radiotherapy (SGRT) system for the open-face masks. Results30 patients with primary or metastatic brain tumors were randomized − 29 completed radiotherapy to a median total dose of 54 Gy (range 30–60 Gy). Mean discomfort VAS score was significantly lower with open-face masks (0.5, standard deviation 1.0) vs. closed masks (3.3, standard deviation 2.9), P < 0.0001. Anxiety and pain VAS scores were significantly lower with open-face masks (P < 0.0001). Closed masks caused more discomfort in infraorbital (P < 0.001) and maxillary (P = 0.02) areas. Two patients and 27 patients preferred closed or open-face masks, respectively. Interfraction longitudinal shifts and roll and yaw rotations were significantly smaller and lateral shifts were significantly larger with closed masks in combination with the laser system (P < 0.05) compared to open masks in combination with a SGRT system. Intrafraction variability did not differ between the masks. ConclusionsOpen-face masks are associated with decreased patient discomfort without compromising patient positioning and immobilisation accuracy.

Benzo[a]pyrene promotes an epithelial‐to‐mesenchymal transition process in MCF10A cells and mammary tumor growth and brain metastasis in female mice

AbstractBreast cancer is the most frequent neoplasia in developed countries and the leading cause of death in women worldwide. Epithelial‐to‐mesenchymal transition (EMT) is a cellular process through which epithelial cells decrease or lose their epithelial characteristics and gain mesenchymal properties. EMT mediates tumor progression, because tumor cells acquire the capacity to execute the multiple steps of invasion and metastasis. Benzo[a]pyrene (B[a]P) is an environmental organic pollutant generated during the burning of fossil fuels, wood, and other organic materials. B[a]P exposition increases the incidence of breast cancer, and induces migration and/or invasion in MDA‐MB‐231 and MCF‐7 breast cancer cells. However, the role of B[a]P in the induction of an EMT process and metastasis of mammary carcinoma cells has not been studied in detail. In this study, we demonstrate that B[a]P induces an EMT process in MCF10A mammary non‐tumorigenic epithelial cells. In addition, B[a]P promotes the formation of larger tumors in Balb/cJ mice inoculated with 4T1 cells than in untreated mice and treated with dimethyl sulfoxide (DMSO). B[a]P also increases the number of mice with metastasis to brain and the total number of brain metastatic nodules in Balb/cJ mice inoculated with 4T1 cells compared with untreated mice and treated with DMSO. In conclusion, B[a]P induces an EMT process in MCF10A cells and the growth of mammary tumors and metastasis to brain in Balb/cJ mice inoculated with 4T1 cells.

Metastases and Primary Brain Tumors Affecting the Fornix of the Brain.

Background The aim of this study is to evaluate the clinical and radiological findings of metastatic tumors and primary brain tumors affecting the fornix. Methods Between January 2015 and March 2023, we retrospectively evaluated 1087 patients of both sexes who underwent cranial magnetic resonance imaging (MRI) for a preliminary diagnosis of intracranial malignancy in the radiology department of our hospital. Two radiologists with six and 10 years of experience in MRI examination assessed the relationship between primary and metastatic tumors and the fornix. Results Involvement of the fornix was diagnosed in 29 of the 1087 patients (2.66%), of which fornix was affected by metastatic lesions in 14 patients (48.2%) and primary tumors in 15 patients (51.7%).The majority of metastatic lesions were from lung and breast cancers, with other tumor types including osteosarcoma, renal cell carcinoma, pancreatic adenocarcinoma, pleomorphic sarcoma, and diffuse large B-cell lymphoma. Among all primary tumors, glioblastoma was the most common primary brain tumor invading the fornix, with other diagnoses including diffuse astrocytoma, medulloblastoma, and anaplastic oligodendroglioma.Metastatic and primary brain tumors affecting the fornix were detected over a broad timeline, from the time of diagnosis up to 120 months after diagnosis. A retrospective evaluation of medical records revealed memory deficits in four patients. Conclusion The fornix can be affected by both metastatic and primary brain tumors. It is crucial to understand the relevant neuroanatomical relationships when evaluating lesions that affect the fornix.

376 Laser Interstitial Thermal Therapy for Deep-Seated Perivascular Brain Tumors: Evaluating the Risk of Distal Ischemia

INTRODUCTION: Laser interstitial thermal therapy (LITT) is a novel minimally invasive cytoreductive treatment option for primary and metastatic brain tumors. By relying on stereotactic guidance, the use of LITT carries a risk for direct and thermal vascular injury, especially when targeting deep-seated tumors with surrounding critical vasculature. It is thought that nearby blood vessels act as heat sinks from thermal injury, however, the risk of ablation causing an ischemic stroke is not well reported. METHODS: A retrospective review identified patients who underwent LITT between 2013 – 2021 for brain tumors located within the insula, basal ganglia, and thalamus. Demographic, clinical, and volumetric characteristics were collected. The primary outcome was radiographic evidence of distal ischemia on post-ablation imaging. RESULTS: A total of 50 patients underwent 59 ablations for perivascular brain tumors located in the insula (52%), basal ganglia (24%), and thalamus (24%). Of the tumors treated, 22 (37%) were low-grade gliomas, 32 (54%) were high-grade gliomas, and 5 (8%) were metastatic. No coagulopathies were identified in any patient. A biopsy was performed in 72% of patients. The mean volume of ablation was 12.4 cm3 (S.D. 13.9) with a median extent of ablation of 92% (IQR 30%, 100%). Two patients developed symptomatic intracerebral hemorrhage. One developed a tract hemorrhage attributed to vessel injury from fiber insertion. The other presented with delayed onset hemorrhage one week later due to uncontrolled hypertension. In all patients, there was no radiographic evidence of distal ischemia following LITT on DWI sequencing . The median length of stay was 2 days with 81% of patients being discharged home. CONCLUSIONS: We demonstrate that LITT has minimal risk for new onset distal ischemia for deep-seated perivascular brain tumors.

154 Elucidating the Immune Landscape of Radiation Necrosis Through Single Cell Analysis of Recurrent Brain Lesions in Patients After Stereotactic Radio Surgery

INTRODUCTION: Radiation necrosis (RN), a common and morbid side effect of radiosurgical treatment of brain metastasis, is becoming more prevalent as immunotherapy options and patient survival improve. Thought to be immunologically driven, the pathophysiology of RN remains poorly defined. Further, RN is often indistinguishable from regrowing metastases after stereotactic radiosurgery (SRS), requiring invasive brain biopsy for diagnosis. METHODS: We collected 20 intraoperative samples from patients undergoing craniotomy for RN and/or metastatic tumor, as well as time-matched blood and CSF. We created a tissue bank, processed samples, and using fluorescence-activated cell sorting (FACS) and 10x Genomics single cell RNA sequencing, analyzed the cellular immune profile of lesional tissue, blood, and CSF. RESULTS: RN tissue demonstrates a robust, detectable expression of immune cells, including CD8+ and CD4+ T cells, natural killer (NK) and myeloid cells. Importantly, clustering of RN-derived immune cells (including T cells, myeloid cells, and NK cells) is reflected in the blood and CSF, with similar immune profiles. We demonstrate a subpopulation of myeloid cells with a microglia signature (CD14+, LYZ-, MS4A7+), and a separate population expressing interferon-stimulated gene (ISG). Supporting these findings, pathway analysis of top blood markers reveals pathways involved in innate and inflammatory immune responses in the blood of RN patients. CONCLUSIONS: These findings demonstrate the feasibility of extracting live cells from RN tissue for scRNAseq analysis and suggest that there are unique signatures of RN that can be detected in the blood and CSF of patients. This work has the potential to open new avenues for improved diagnostic and therapeutic approaches to allow earlier detection and more effective treatment of RN in patients with metastatic brain tumors.

Where Do Surgical Resection and Radiosurgery Fall Short for Large Metastatic Brain Lesions?

INTRODUCTION: Stereotactic radiosurgery is established as the optimal treatment modality for metastatic disease of the brain, but there is ongoing debate about the optimal treatment for larger brain metastases. There have been few studies identifying and quantifying lesion characteristics where efficacy and local control of these lesions suffer. METHODS: We retrospectively identified patients who received surgical resection and/or hypofractionated Gamma Knife radiosurgery (HF-GKRS) between 2017 and 2022 for the treatment of metastatic brain tumors greater than 10cc. Clinical, treatment, and radiological data was collected. Local failure (LF) events were examined, and independent factors associated with subsequent local failure were identified. RESULTS: 105 lesions greater than 10cc (in 97 patients) were treated and the median patient follow-up was 10.1 months. The median gross tumor volume was 15.8cc (range 10.1-62.4). Prior surgical resection was performed on 49 lesions (54%). Tumor volume larger than 33.5cc (p = 0.029, 12-month LF rate 38%) and radioresistant histology (p=0.047, 12-month LF rate 54%) were associated with increased risk of LF (p=0.018) whereas surgical resection did not correlate with increased LC (p = 0.642, 12-month LF rate 19%). CONCLUSIONS: Patients with brain metastases that are greater than 4cm in diameter or are of radioresistant histology (primary origin of gastrointestinal adenocarcinoma, melanoma, or renal cell carcinoma) are especially prone to local failure despite aggressive surgical resection, stereotactic radiosurgery, and systemic chemotherapy. In these cases, the optimal management needs to be further elucidated and may involve preoperative stereotactic radiosurgery or intraoperative brachytherapy.

Border Zone Maybe Correlated with Radiation Necrosis After Radiosurgery in Metastatic Brain Tumor

BackgroundRadiation necrosis (RN) after stereotactic radiosurgery (SRS) in brain metastases has been extensively evaluated, and RN is correlated with various risk factors. However, no study comprehensively analyzed the correlation between RN and the border zones of the brain that are vulnerable to ischemia. We hypothesized that patients with tumors in the border zone are at high risk of RN. Hence, the current study aimed to assess the correlation between border zone lesions and RN, with consideration of other predetermined factors. MethodsThis retrospective study included 117 patients with 290 lesions who underwent Gamma Knife® stereotactic radiosurgery (SRS). Radiological and clinical analyses were performed to identify factors possibly correlated with RN. Notably, the lesion location was classified into two groups (border zone and non-border zone) based on the blood supply. ResultsIn total, 22 (18.8%) patients with 22 (7.5%) lesions developed RN. Univariate analysis revealed a significant correlation between RN and external border zone lesions, second course of SRS administered at the same site of the previous SRS, prescribed dose, and tumor volume. Multivariate analysis showed that border zone lesions, second course of SRS at the same site of the previous SRS, and tumor volume were significantly correlated with RN. ConclusionsPatients with tumors in the border zone are at high risk of RN. The potential risks of RN can be attributed hypothetically to hypoperfusion. Hence, the association between RN and border zone lesions seems reasonable.

Abstract 1283: Digital spatial profiling of metastatic brain tumors reveals association of the tumor microbiome with immune alterations in the tumor microenvironment

Abstract Introduction: Metastatic brain tumors are associated with significant morbidity and mortality. The microbiome has emerged as a novel hallmark of cancer, with a prominent role in tumor immunity and response to treatment. However, the role of the microbiome in brain tumors, and in particular brain metastasis, is largely unknown. We hypothesized that distinct microbial communities are associated with alterations in the tumor microenvironment in metastatic brain tumors. Methods: To evaluate the role of different microbial communities in brain metastasis, matched stool, saliva, and tumor samples were collected prospectively from patients with metastatic brain tumors who underwent surgical tumor resection at the University of Texas MD Anderson Cancer Center. Stool and saliva samples were sequenced via metagenomic shotgun sequencing and tumor samples were analyzed through 16S rRNA gene sequencing. The tumor microbiome was further characterized through confocal and electron microscopy and culture techniques. Lastly, we conducted digital spatial profiling using the NanoString GeoMx® platform to determine the spatial association of the tumor microbiome with tumor and immune transcriptome. Spatial single-cell transcriptome analysis of bacteria-positive and bacteria-negative cells within the tumor microenvironment is currently in progress using the CosMx® platform (NanoString Inc.). Results: Our computational and experimental analyses demonstrated that bacterial signals could be detected in metastatic brain tumors and exhibit an intracellular localization. Interestingly, we found that the tumor bacterial signatures in brain metastases were composed of commensal oral bacterial taxa but had limited overlap with the gut microbiome. Spatial transcriptome analysis demonstrated that tumor areas with high bacterial signal were associated with innate-immune mediated anti-bacterial responses, suggesting an active host response to intra-tumoral bacteria in metastatic brain tumors. Conclusion: Overall, this work demonstrates the presence of intracellular bacterial signal coupled with an anti-bacterial response within the tumor microenvironment of brain metastases. These findings offer a new perspective on the dynamic interaction between cancer, microbiome, and the brain microenvironment and can inform future mechanistic and translational studies to improve the outcome of brain tumor patients. Citation Format: Golnaz Morad, Ashish V. Damania, Brenda Melendez, Matthew C. Wong, Pranoti V. Sahasrabhojane, Sarah B. Johnson, Manoj Chelvanambi, Florentia Dimitriou, Jillian S. Losh, Nadim J. Ajami, Sherise D. Ferguson, Jennifer A. Wargo. Digital spatial profiling of metastatic brain tumors reveals association of the tumor microbiome with immune alterations in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1283.

Abstract 5703: Development of RVL-101, a CDK4/6-selective, small molecule inhibitor with superior CNS penetration and combinability potential for the effective treatment of primary and metastatic brain tumors

Abstract Cyclin-dependent kinases 4 and 6 (CDK4/6) are key regulators of the cell cycle that are frequently dysregulated in cancer, leading to unchecked cell growth. CDK4/6 inhibitors have emerged as a promising class of anticancer agents that selectively target this pathway. The primary mode of action of CDK4/6 inhibitors relies on the disruption of retinoblastoma (Rb) protein phosphorylation, which thereby blocks cell cycle progression from G1 to S phase and reduces proliferation of cancer cells by a cytostatic mechanism. However, despite their efficacy, approved and clinical-stage CDK4/6 inhibitors have modest penetration of unbound drug into the brain, limiting their utility in the treatment of brain metastases and primary brain tumors. Additionally, despite the potential benefits of CDK4/6 inhibitors as combination therapies with cytotoxic agents, adjunctive treatment options remain underexplored due to the poor safety profiles of existing therapies. RVL-101 is a preclinical, investigational drug with a novel pharmacophore that has a low nanomolar activity against CDK4, is CDK2,6,7,9-sparing, and maintains &amp;gt;500-fold selectivity over CDK1. To maximize the potential of RVL-101 as a preferred combination partner, this novel agent has been engineered to have exquisite kinome- and safety-panel selectivity with no measured CYP inhibition or induction liabilities. RVL-101 is differentiated from approved and clinical stage CDK4/6 inhibitors having both high partitioning into the brain (Kp) and high free-brain (Kpu,u = 0.7) levels resulting in equal levels of unbound drug in all relevant compartments at steady state. Like other CDK4/6 agents, RVL-101 is broadly efficacious in vivo in ER+/HER2- xenograft models at well-tolerated doses. However, RVL-101 has also demonstrated robust activity in HR-/HER2+ xenograft models as a single-agent and has uniquely shown improved tumor inhibition effect in combination with approved HER2 cytotoxic therapeutics tucatinib and fam-trastuzumab-deruxtecan. RVL-101 was also tested in a GBM model as a monotherapy and in conjunction with the cytotoxic agent temozolomide (TMZ). Remarkably, QD dosing of the cytostatic agent, RVL-101, after pulsatile pretreatment with TMZ led to dramatic synergistic efficacy compared to either agent alone, leading to 100% survival of all animals on the dual therapy arm for more than 3 weeks post discontinuation of dosing. RVL-101 offers the combination of substantial therapeutic benefit and consistent free-drug levels in plasma and CNS that could lead to safe and effective treatment for a broader patient population. Citation Format: John E. Campbell, Bo-Sheng Pan, Michael Bower, Peter Bertinato, Nisha Perez, Victoria Gras Andreu, Neha Rana, Sophia Tabchouri, Ankit Gupta, Jonah Kallenbach. Development of RVL-101, a CDK4/6-selective, small molecule inhibitor with superior CNS penetration and combinability potential for the effective treatment of primary and metastatic brain tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5703.

Abstract 4140: Enhanced microglial phagocytosis of metastatic brain tumor cells with Cd24a/Cd47 depletion

Abstract Despite the robust homeostasis of the brain, its high prevalence of tumor metastasis is intriguing and the underlying mechanism may contribute to the development of novel therapies. Microglia have emerged as promising therapeutic targets due to their role in brain parenchymal homeostasis. However, with evidence for both pro- and anti-tumorigenic functions, their role in brain metastasis (BrM) remains unclear. Here, we show that the microglial response to tumor cells within a single host is heterogeneous and can alter tumor fate. Single-cell RNA sequencing was performed on five surgically resected metastatic brain tumors, and the transcriptome of tumor-associated microglia was extracted by single-cell variational inference (scVI). Evidence for the coexistence of cytokine-secreting and angiogenesis-supporting subsets, as well as subsets associated with phagocytosis and antigen presentation, within each tumor sample was determined. To demonstrate the intra-tumoral functional heterogeneity of tumor-associated microglia, we established a metastatic brain tumor model that allows us to visualize the metastatic process and the dynamic microglial response in vivo by injecting mCherry-tagged allogeneic cancer cells into the internal carotid artery of CX3CR1-EGFP mice. Metastasis formation was suppressed in microglia-depleted mice, identifying a dominant microglial response that promotes tumor growth. However, continuous in vivo imaging of the BrM model revealed tumor-eradicating anti-tumor microglia coexisting with pro-tumor microglia in the same host. The transcriptome of anti-tumor microglia supported that they are enriched for phagocytosis, antigen processing and antigen presentation genes. The subset was identified in microglia extracted from human samples. We then examined the immune checkpoint of microglial phagocytosis in the tumor transcriptome and identified Cd24a and Cd47. Simultaneous deletion of both genes in cancer cells enhanced microglial phagocytosis, reduced tumor volume and improved survival, and rescue of both genes reversed these anti-tumor effects. The microglial dependency was addressed by microglial depletion experiments, and the anti-tumor effects were reproducible in nude mice lacking mature T cells. These results suggest that there are distinct immune cell subtypes that respond to lung tumor metastases in the brain and either promote tumor growth or inhibit metastasis through phagocytosis. Furthermore, anti-tumor activity in mouse models can be enhanced by genetic deletion of Cd24a and Cd47 in tumor cells, which regulate phagocytosis by microglia. Citation Format: Takahiro Tsuji, Haruka Hirose, Mariko Shindo, Rahadian Yudo Hartantyo, Yutaro Saito, Kazutaka Hosoya, Hiroshi Yoshida, Daisuke Kato, Akihiko Yoshizawa, Yoshiki Arakawa, Hiroaki Ozasa, Toyohiro Hirai, Hiroaki Wake. Enhanced microglial phagocytosis of metastatic brain tumor cells with Cd24a/Cd47 depletion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4140.

Abstract 7362: Integrated analysis of scRNAseq and spatial omics in brain metastatic lung cancer tumor tissue

Abstract Spatial omics technologies have made significant advances in recent years, improving our understanding of the spatial localization of cells and intercellular interactions. Intercellular interactions are essential for maintaining proper tissue function and homeostasis, and dysregulation of these interactions can contribute to various diseases, including cancer and autoimmune disorders. Ligand proteins, one of the signaling molecules responsible for cell-cell interactions, bind to cell surface receptors and trigger intracellular signaling pathways. The effective range of ligand signaling, i.e. the extent to which a cell spatially and directly transmits information via the ligand, has not been systematically studied, although it may determine the occurrence of cell-cell interactions. The authors have previously developed methodologies combining spatial transcriptomics and single-cell RNA sequencing to analyze intercellular interactions at the single-cell level in spatial dimensions. Additionally, we have devised a technique to model the spatial diffusion of ligands from spatial transcriptomics and estimate the spatial range of ligand action. In this study, we used these developed methods to elucidate events in the tumor microenvironment of brain metastatic lung cancer tissue. Specifically, an integrated analysis of metastatic brain tumor samples was performed using visium and single-cell data from the same patient. The results suggest the presence of a heterogeneous microglial subpopulation, including clusters enriched in cytokines and chemokines for angiogenesis and wound healing, clusters associated with immune tolerance via IL-10 signaling, clusters enriched in gene sets related to phagocytosis, antigen processing, and antigen presentation, and clusters related to clearance of pathogens and residues. The presence of homogeneous microglial subpopulations was suggested. Furthermore, these subpopulations exhibited different spatial distributions, suggesting that they interact with surrounding cancer cells through different mechanisms. Citation Format: Haruka Hirose, Takahiro Tsuji, Yasuhiro Kojima, Akihiko Yoshizawa, Yoshiki Arakawa, Hiroaki Ozasa, Hiroaki Wake, Teppei Shimamura. Integrated analysis of scRNAseq and spatial omics in brain metastatic lung cancer tumor tissue [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7362.