Brain Metastasis Formation Research Articles

PD-1 blockade does not improve efficacy of EpCAM-directed CAR T-cell in lung cancer brain metastasis

BackgroundLung cancer brain metastasis has a devastating prognosis, necessitating innovative treatment strategies. While chimeric antigen receptor (CAR) T-cell show promise in hematologic malignancies, their efficacy in solid tumors, including brain metastasis, is limited by the immunosuppressive tumor environment. The PD-L1/PD-1 pathway inhibits CAR T-cell activity in the tumor microenvironment, presenting a potential target to enhance therapeutic efficacy. This study aims to evaluate the impact of anti-PD-1 antibodies on CAR T-cell in treating lung cancer brain metastasis.MethodsWe utilized a murine immunocompetent, syngeneic orthotopic cerebral metastasis model for repetitive intracerebral two-photon laser scanning microscopy, enabling in vivo characterization of red fluorescent tumor cells and CAR T-cell at a single-cell level over time. Red fluorescent EpCAM-transduced Lewis lung carcinoma cells (EpCAM/tdtLL/2 cells) were implanted intracranially. Following the formation of brain metastasis, EpCAM-directed CAR T-cell were injected into adjacent brain tissue, and animals received either anti-PD-1 or an isotype control.ResultsCompared to controls receiving T-cell lacking a CAR, mice receiving EpCAM-directed CAR T-cell showed higher intratumoral CAR T-cell densities in the beginning after intraparenchymal injection. This finding was accompanied with reduced tumor growth and translated into a survival benefit. Additional anti-PD-1 treatment, however, did not affect intratumoral CAR T-cell persistence nor tumor growth and thereby did not provide an additional therapeutic effect.ConclusionCAR T-cell therapy for brain malignancies appears promising. However, additional anti-PD-1 treatment did not enhance intratumoral CAR T-cell persistence or effector function, highlighting the need for novel strategies to improve CAR T-cell therapy in solid tumors.

ENPP1 induces blood-brain barrier dysfunction and promotes brain metastasis formation in HER2-positive breast cancer.

Brain metastasis (BrM) is a devastating end-stage neurological complication that occurs in up to 50% of HER2+ breast cancer patients. Understanding how disseminating tumor cells manage to cross the blood-brain barrier (BBB) is essential for developing effective preventive strategies. We identified the ecto-nucleotidase ENPP1 as specifically enriched in the secretome of HER2+ brain metastatic cells, prompting us to explore its impact on BBB dysfunction and BrM formation. We used in vitro BBB and in vivo premetastatic mouse models to evaluate the effect of tumor-secreted ENPP1 on brain vascular permeability. BBB integrity was analyzed by real-time fluorescence imaging of 20kDa Cy7.5-dextran extravasation and immunofluorescence staining of adherens and tight junction proteins. Pro-metastatic effects of ENPP1 were evaluated in an experimental brain metastatic model. Systemically secreted ENPP1 from primary breast tumors impaired the integrity of BBB with loss of tight and adherens junction proteins early before the onset of BrM. Mechanistically, ENPP1 induced endothelial cell dysfunction by impairing insulin signaling and its downstream AKT/GSK3β/β-catenin pathway. Genetic ablation of ENPP1 from HER2+ brain metastatic cells prevented endothelial cell dysfunction and reduced metastatic burden while prolonging the overall and metastasis-free survival of mice. Furthermore, plasmatic ENPP1 levels correlate with brain metastatic burden and inversely with overall survival. We demonstrated that metastatic breast cancer cells exploit the ENPP1 signaling for cell transmigration across the BBB and brain colonization. Our data implicate ENPP1 as a potential biomarker for poor prognosis and early detection of BrM in HER2+ breast cancer.

T lymphocyte-derived IFN-γ facilitates breast cancer cells to pass the blood-brain barrier: An in vitro study corroborating translational data

The appearance of brain metastasis is the most serious complication of breast cancer with mostly fatal outcomes. To reach the brain, tumor cells need to pass the blood-brain barrier (BBB). The molecular mechanisms underlying penetration of the BBB are largely unknown. Previously we found that tumor-infiltrating T lymphocytes enhance the development of brain metastasis of estrogen receptor-negative (ER-) breast cancer. In the current study, we investigate the contribution of T lymphocytes and the IFN-γ pathway in enabling breast cancer cells to pass the in vitro BBB. CD8+ cells display the strongest stimulatory effect on breast cancer cell passage. We show that inhibition of the IFN-γ receptor in MDA-MB-231 breast cancer cells, or neutralization of soluble IFN-γ, impairs the in vitro trespassing of breast cancer cells. Importantly, we validated our findings using gene expression data of breast cancer patients. The CXCL-9,-10,-11/CXCR3 axis, dependent on IFN-γ signaling activity, was overexpressed in primary breast cancer samples of patients who developed brain metastasis. The data support a role for T-lymphocytes and the IFN-γ pathway in the formation of brain metastasis of ER-breast cancer, and offer targets to design future therapies for preventing breast cancer cells to cross the BBB.

Disturbance in cerebral blood microcirculation and hypoxic-ischemic microenvironment are associated with the development of brain metastasis.

Brain metastases (BM) constitute an increasing challenge in oncology due to their impact on neurological function, limited treatment options, and poor prognosis. BM occur through extravasation of circulating tumor cells across the blood-brain barrier. However, the extravasation processes are still poorly understood. We here propose a brain colonization process which mimics infarction-like microenvironmental reactions, that is dependent on Angiopoietin (Ang-2) and vascular endothelial growth factor (VEGF). In this study, intracardiac BM models were used, and cerebral blood microcirculation was monitored by 2-photon microscopy through a cranial window. BM formation was observed using cranial magnetic resonance, bioluminescent imaging, and post-mortem autopsy. Ang-2/VEGF targeting strategies and Ang-2 gain-of-function (GOF) mice were employed to interfere with BM formation. In addition, vascular and stromal factors as well as clinical outcome were analyzed in BM patients. Blood vessel occlusions by cancer cells were detected, accompanied by significant disturbances of cerebral blood microcirculation, and focal stroke-like histological signs. Cerebral endothelial cells showed an elevated Ang-2 expression both in mouse and human BM. Ang-2 GOF resulted in an increased BM burden. Combined anti-Ang-2/anti-VEGF therapy led to a decrease in brain metastasis size and number. Ang-2 expression in tumor vessels of established human brain metastases negatively correlated with survival. Our observations revealed a relationship between disturbance of cerebral blood microcirculation and brain metastasis formation. This suggests that vessel occlusion by tumor cells facilitates brain metastatic extravasation and seeding, while combined inhibition of microenvironmental effects of Ang-2 and VEGF prevent the outgrowth of macrometastases.

Abstract 1500: Breast cancer-derived extracellular vesicles modulate the endocytic metabolism and morphodynamics of the endothelial cells of the blood-brain barrier

Abstract Breast cancer, particularly the triple-negative subtype, is the primary cause of brain metastasis in women, affecting 10-20% of breast cancer patients. Breast cancer patients who develop brain metastasis have few treatment options and a dismal prognosis with a median survival time of 6-16 months. We demonstrated, for the first time, that EVs derived from brain-seeking breast cancer cells (BrEVs) breach the intact blood-brain barrier (BBB) via transcytosis and cause a significantly increased incidence of breast-to-brain metastasis. Within this context, we are now studying the interactions between BrEVs and the endothelial cells (ECs) of the BBB. BrEVs were isolated by ultracentrifugation, characterized following the latest guidelines published by the International Society of Extracellular Vesicles (MISEV 2018) and tested in vitro using primary human brain ECs and in vivo using our mouse model of breast-to-brain metastasis. ECs were treated with BrEVs and analyzed using antibody-based assays, impedance measurements, genetic engineering and fixed and live cell imaging. The imaging results were analyzed using novel machine learning approaches to detect and describe, for the first time, EV-mediated morphodynamic changes at the brain EC barrier level. In vivo, we administered BrEVs intravenously to our models of breast-to-brain metastasis, followed by the analysis of mouse brains and their cerebral microvessels to examine microscopic structure and protein expression. Our studies show that (1) BrEVs target BBB ECs both in vitro and in vivo, causing significant variations of multiple proteins involved in the intracytoplasmic vesicles' long-recycling loop, (2) BrEVs are responsible for specific EC barrier function and morphodynamic changes and (3) BrEVs mediate, at least in part, their effect(s) through the delivery of specific micro RNAs. Taken together, our studies demonstrate that BrEVs have a significant impact on brain EC endocytic metabolism and morphodynamics, promoting transcytosis and sustaining breast-to-brain metastasis. Our findings increase our understanding of the early events that facilitate brain metastasis and have the potential to identify key regulators of brain metastasis formation. These results also inform and contribute to the development of EV-based therapeutic and diagnostic strategies for brain metastasis. (This work was supported by NIH R21 CA253051-01, the Breast Cancer Research Foundation, NIH T32 5T32HL007917-22 and the Nile Albright Research Foundation.) Citation Format: Sara Busatto, Golnaz Morad, Marsha A Moses. Breast cancer-derived extracellular vesicles modulate the endocytic metabolism and morphodynamics of the endothelial cells of the blood-brain barrier [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 1500.

Hypoxia-induced activation of NDR2 underlies brain metastases from Non-Small Cell Lung Cancer

The molecular mechanisms induced by hypoxia are misunderstood in non-small cell lung cancer (NSCLC), and above all the hypoxia and RASSF1A/Hippo signaling relationship. We confirmed that human NSCLC (n = 45) as their brain metastases (BM) counterpart are hypoxic since positive with CAIX-antibody (target gene of Hypoxia-inducible factor (HIF)). A severe and prolonged hypoxia (0.2% O2, 48 h) activated YAP (but not TAZ) in Human Bronchial Epithelial Cells (HBEC) lines by downregulating RASSF1A/kinases Hippo (except for NDR2) regardless their promoter methylation status. Subsequently, the NDR2-overactived HBEC cells exacerbated a HIF-1A, YAP and C-Jun-dependent-amoeboid migration, and mainly, support BM formation. Indeed, NDR2 is more expressed in human tumor of metastatic NSCLC than in human localized NSCLC while NDR2 silencing in HBEC lines (by shRNA) prevented the xenograft formation and growth in a lung cancer-derived BM model in mice. Collectively, our results indicated that NDR2 kinase is over-active in NSCLC by hypoxia and supports BM formation. NDR2 expression is thus a useful biomarker to predict the metastases risk in patients with NSCLC, easily measurable routinely by immunohistochemistry on tumor specimens.

SNP array genomic analysis of matched pairs of brain and liver metastases in primary colorectal cancer

PurposeBrain metastasis formation is a rare and late event in colorectal cancer (CRC) patients and associated with poor survival. In contrast to other metastatic sites, the knowledge on chromosomal aberrations in brain metastases is very limited.MethodsTherefore, we carried out single nucleotide polymorphism (SNP) array analyses on matched primary CRC and brain metastases of four patients as well as on liver metastases of three patients.ResultsBrain metastases showed more chromosomal aberrations than primary tumors or liver metastases. Commonly occurring aberrations were gain of 8q11.1-q24.3 (primary CRC), gain of 13q12.13-q12.3 (liver metastases), and gain of 20q11.1-q13.33 (brain metastases). Furthermore, we found one copy-neutral loss of heterozygosity (cn-LOH) region on chromosome 3 in primary CRC, three cn-LOH regions in liver metastases and 23 cn-LOH regions in brain metastases, comprising 26 previously undescribed sites.ConclusionThe more frequent occurrence of cn-LOHs and subsequently affected genes in brain metastases shed light on the pathophysiology of brain metastasis formation. Further pairwise genetic analyses between primary tumors and their metastases will help to define the role of affected genes in cn-LOH regions.

Use of comprehensive genomic profiling for biomarker discovery for the management of non-small cell lung cancer brain metastases.

Clinical biomarkers for brain metastases remain elusive. Increased availability of genomic profiling has brought discovery of these biomarkers to the forefront of research interests. In this single institution retrospective series, 130 patients presenting with brain metastasis secondary to Non-Small Cell Lung Cancer (NSCLC) underwent comprehensive genomic profiling conducted using next generation circulating tumor deoxyribonucleic acid (DNA) (Guardant Health, Redwood City, CA). A total of 77 genetic mutation identified and correlated with nine clinical outcomes using appropriate statistical tests (general linear models, Mantel-Haenzel Chi Square test, and Cox proportional hazard regression models). For each outcome, a genetic signature composite score was created by summing the total genes wherein genes predictive of a clinically unfavorable outcome assigned a positive score, and genes with favorable clinical outcome assigned negative score. Seventy-two genes appeared in at least one gene signature including: 14 genes had only unfavorable associations, 36 genes had only favorable associations, and 22 genes had mixed effects. Statistically significant associated signatures were found for the clinical endpoints of brain metastasis velocity, time to distant brain failure, lowest radiosurgery dose, extent of extracranial metastatic disease, concurrent diagnosis of brain metastasis and NSCLC, number of brain metastases at diagnosis as well as distant brain failure. Some genes were solely associated with multiple favorable or unfavorable outcomes. Genetic signatures were derived that showed strong associations with different clinical outcomes in NSCLC brain metastases patients. While these data remain to be validated, they may have prognostic and/or therapeutic impact in the future. Using Liquid biopsy in NSCLC brain metastases patients, the genetic signatures identified in this series are associated with multiple clinical outcomes particularly these ones that lead to early or more numerous metastases. These findings can be reverse-translated in laboratory studies to determine if they are part of the genetic pathway leading to brain metastasis formation.

Compromised Blood-Brain Barrier Junctions Enhance Melanoma Cell Intercalation and Extravasation.

Melanoma frequently metastasises to the brain, and a detailed understanding of the molecular and cellular mechanisms underlying melanoma cell extravasation across the blood-brain barrier (BBB) is important for preventing brain metastasis formation. Making use of primary mouse brain microvascular endothelial cells (pMBMECs) as an in vitro BBB model, we imaged the interaction of melanoma cells into pMBMEC monolayers. We observed exclusive junctional intercalation of melanoma cells and confirmed that melanoma-induced pMBMEC barrier disruption can be rescued by protease inhibition. Interleukin (IL)-1β stimulated pMBMECs or PECAM-1-knockout (-ko) pMBMECs were employed to model compromised BBB barrier properties in vitro and to determine increased melanoma cell intercalation compared to pMBMECs with intact junctions. The newly generated brain-homing melanoma cell line YUMM1.1-BrM4 was used to reveal increased in vivo extravasation of melanoma cells across the BBB of barrier-compromised PECAM-1-deficient mice compared to controls. Taken together, our data indicate that preserving BBB integrity is an important measure to limit the formation of melanoma-brain metastasis.

MEF2C and miR-194-5p: New Players in Triple Negative Breast Cancer Tumorigenesis.

Among breast cancer (BC) subtypes, the most aggressive is triple negative BC (TNBC), which is prone to metastasis. We previously found that microRNA (miR)-194-5p is downregulated at the early stages of TNBC brain metastasis development. Additionally, the transcription factor myocyte enhancer factor 2 (MEF2)C, a bioinformatically predicted miR-194-5p target, was increasingly expressed throughout TNBC brain metastasis formation and disease severity. However, the contributions of these two players to malignant cells' features remain undetermined. This study aimed at disclosing the role of miR-194-5p and MEF2C in TNBC tumorigenesis. The transfection of 4T1 cells with a silencer for MEF2C or with a pre-miRNA for miR-194-5p was employed to study TNBC cells' phenotypic alterations regarding epithelial and mesenchymal markers, as well as migratory capability alterations. MEF2C-silenced cells presented a decline in both vimentin and cytokeratin expression, whereas the overexpression of miR-194-5p promoted an increase in cytokeratin and a reduction in vimentin, reflecting the acquisition of an epithelial phenotype. Both treatments reduced TNBC cells' migration. These results suggest that MEF2C may determine TNBC cells' invasive properties by partially determining the occurrence of epithelial-mesenchymal transition, while the overexpression of miR-194-5p promotes a decline in TNBC cells' aggressive behavior and reinforces this miRNA's role as a tumor suppressor in TNBC.

P10.12.B MOLECULAR MECHANISMS INVOLVED IN THE DEVELOPMENT OF BRAIN METASTASIS FROM THE MATCHED PAIRED LUNG ADENOCARCINOMA AND BREAST CANCER

Abstract BACKGROUND Up to 50% of patients with common cancers will develop brain metastases and incidences of this devastating complication are still rising. In our recent work, we found that the immune response in the brain is significantly stronger when the metastasis develops from lung adenocarcinoma (LUAD) compared to breast cancer (BC). Importantly, we discovered the higher expression of the drug target, VISTA, only in the brain metastasis of the LUAD. The aim of the current study was to investigate the molecular mechanisms driving the formation of brain metastasis from the two different lineages of cancer. In addition, we aimed to examine the expression level of the drugable molecules between primary tumors and their brain metastasis. MATERIAL AND METHODS Primary tumor and their matched brain metastasis samples of 11 LUAD and 11 breast cancer (total = 44 samples) were included in this study. RNA was extracted from the FFPE samples and the targeted gene expression profiles were measured using the PanCancer IO360™ Panel that includes 770 cancer-related genes (NanoString technology). Data were analysed using the nSolver software. RESULTS A first comparison was made between the primary tumors with their brain metastases for LUAD and BC separately. The second comparison was made between the common genes of both lineages. Pathway analysis indicated that there is higher metabolic stress in breast cancer-brain metastasis compared to that in the lung. In addition, we identified 12 common up-regulated genes in brain metastasis, despite the origin of the primary tumor. Importantly, by comparing the primary tumors of BC and LUAD with their brain metastasis, we found that VISTA is predominantly highly expressed in the primary tumors of LUAD and their matched brain metastasis. CONCLUSION Although the general mechanisms of metastasis have been described, our study demonstrates that different cancer lineages utilize various genes/pathways to metastasize to the brain. Moreover, primary LUAD and their brain metastasis express high levels of VISTA highlighting the possibilities for targeted therapy.

BSBM-22 CHARACTERIZATION OF CIRCULATORY SHEAR STRESS-INDUCED MOLECULAR CHANGES IN LUNG ADENOCARCINOMA CELLS AND IMPLICATIONS IN BRAIN METASTASIS

Abstract INTRODUCTION Lung cancer is the most common tumor to metastasize to the brain, as 40% of patients develop brain metastasis (BM). Once diagnosed, survival is only 6.5-10 months. A potential target to prevent BM is circulating tumor cells (CTCs). The mechanisms that mediate a CTCs adaptation to the harsh environment of circulation and BM have not been elucidated. We have demonstrated that primary lung cancer cells (LCCs) subjected to circulation have increased migration across brain endothelial cell monolayers, increased side population, and decrease survival in rodents when injected intracardially vs plated controls. METHODS We engineered a microfluidic device capable of subjecting tumor cells to prolonged circulatory shear stress (CSS) that allows the isolation/modeling of CTC-like cells. Primary LCCs (A549, H1563) were subjected to circulation, suspension, or plated (2D) for 72h as controls. At this time point, LCCs were collected, and total mRNA was extracted. Samples were submitted for RNA sequencing. Weighted gene co-expression network analysis (WCGNA) and Ingenuity Pathway Analysis were performed. (FC >2 and p-value <0.05). RESULTS Transcriptomic analysis indicates that cells subjected to CSS activate specific gene networks involved in cell survival, migration, invasion, adhesion of tumor cells, and cytoskeletal reorganization (z-score: >2, p-value: 0.05). Canonical pathways in CTCs included ILK-signaling and Xenobiotic Metabolism. LCCs exposed to CSS had increased expression of multidrug resistance pumps ABCC2, ABCF2 (P:<0.001), and side population on flow cytometry (P: <0.05). The top differentially expressed genes in CTC-like cells (MMP1, ANGPTL4, and CEMIP) were involved in the invasion, angiogenesis, and pre-metastatic niche (PMN) formation of BM. CONCLUSION LCCs that survive CSS have increased expression of genes associated with migration, invasion, and chemoresistance compared to 2D controls. Targeting genes in CTCs that mediate survival and preparation of the PMN may be useful in preventing BM.

Circulating hsa_circ_0072309, acting via the miR-100/ACKR3 pathway, maybe a potential biomarker for the diagnosis, prognosis, and treatment of brain metastasis from non-small-cell lung cancer.

One of the main causes of lung cancer-related death is brain metastasis (BM). Finding early indicators of BM derived from lung cancer is crucial. Therefore, this study was designed to determine if serum hsa_circ_0072309 may be employed as a potential biomarker for BM induced by non-small-cell lung cancer (NSCLC) and to understand its possible underlying mechanism. Primary lung cancer and healthy neighboring tissues were obtained from all patients, while BM tissues were taken from BM+ patients. Serum specimens were collected from all patients and healthy volunteers. Hsa_circ_001653, miR-100, and ACKR3 RNA expressions were analyzed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and atypical chemokine receptor 3 (ACKR3) protein expression by western blotting (WB), immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA). In order to examine the effect of serum hsa_circ_0072309 and its relevant mechanism on BM development, an NSCLC-associated BM model in mice was established. According to the results, miR-100 expression was down-regulated in primary lung cancer tissues compared to healthy lung tissues in all NSCLC patients, and circ_0072309 and ACKR3 expression were up-regulated. In BM tissues compared with primary lung tumors of BM+ patients, in serum samples from all patients compared to healthy volunteers, and in lung tumors of BM+ patients compared to those from BM- patients. Patients' serum exhibits the same level of hsa_circ_0072309/miR-100/ACKR3 expression as in BM samples. Advanced tumor-node-metastasis (TNM) stage, higher BM, shorter post-operative overall survival (OS), and progression-free survival (PFS) are all substantially associated with increased serum circ_0072309 levels in BM+ patients. In animal models, serum owning hsa_circ_0072309 from BM+ patients facilitates BM formation by regulating the miR-100/ACKR3 pathway. The current preliminary research reveals serum hsa_circ_0072309 as a possible biomarker and target for early diagnosis, prognosis, and therapy of NSCLC-derived BM and suggests a substantial role for the hsa_circ_0072309/miR-100/ACKR3 axis in the formation of BM from NSCLC.

Wolf in sheep’s clothing: Effect of primary lung tumor cells equipped with elevated neuron-like properties on brain metastases formation.

e14009 Background: It is clinically significant to decipher the mechanisms underlying lung cancer-associated brain metastases. However, comparative studies on primary tumors between patients with and without brain metastases failed to unveil such mechanisms. Moreover, the clinical observation that the incidence of brain metastases after resection of the primary tumor was as high in lymph node-negative (non-LNM) patients as in those with lymph node metastases (LNM) challenges our established knowledge that lymph node staging correlates with distant metastases. Here, we hypothesized that tumor cells in non-LNM patients might acquire a unique mechanism to develop brain metastases. Methods: We ran whole-transcriptome sequencing and methylation sequencing on paired primary tumor and brain metastases samples from 15 NSCLC patients. We compared the differentially expressed genes (DEGs) between patients with LNM and non-LNM patients. Results: Pathway enrichment analysis showed that GO and KEGG pathways associated with neuronal transmission and synaptic signaling were upregulated in primary tumors of the non-LNM group vs. that of the LNM group. In contrast, brain metastases revealed an inversed trend of differential expression for these pathways between non-LNM and LNM groups. Exploratory validation at methylation level revealed that high expression of the neuronal transmission-associated gene GABRG3 correlated with hypomethylation of this gene (R=-0.39, p=0. 042), responsive to increased expression of GABRG3 in brain metastases. Brain metastases expressed higher neuronal transmission-related signatures than paired primary tumors. Intriguingly, this upregulation of tumor-neuron interactions was more pronounced in patients with lymph node metastases, suggesting that i) lymph node metastases might aid primary tumor to develop brain metastases by promoting the adaptation of tumor cells to the brain microenvironment, while ii) non-LNM patients already acquired neuron-like traits at primary sites, heralding the potential of brain metastases. Conclusions: The hypothetical mechanism of lymph node-negative lung cancer developing brain metastases might be that these tumor cells acquired properties of brain cells as early as in primary sites, masking themselves as ‘sheep’ to communicate with the host’s brain cells, and eventually unmasked as ‘wolf’: brain metastases. Further functional studies are warranted to validate this hypothesis.

Abstract 1361: Astrocytes activate neuronal programming in melanoma brain metastases

Abstract Melanoma Brain Metastases (MBM) pose a major challenge for treating metastatic melanoma. Up to 70% of advanced melanoma patients develop MBM, resulting in significant morbidity and mortality. Melanocytes, the originating cell type of melanomas, are derived from neural crest cells in development. Melanoma’s proclivity to metastasize to the brain has been anecdotally connected to its neural crest origins. Recently, transcriptomic analyses have demonstrated that MBM express a neuronal-like phenotype, upregulating neural crest factors such as NCAM (Neural cell adhesion molecule), L1CAM (L1 cell adhesion molecule protein), while expressing melanocytic markers like MITF (melanocyte induction transcription factor). The activation of neuronal development programming may be a key mediator in brain-metastatic growth, and thus necessitates a better understanding of how melanoma cells adapt to the brain. Astrocytes have emerged as the major host cell type that cancer cells encounter and interact with during brain metastasis formation. Typically, astrocytes regulate brain homeostasis and support neuronal function. Their response to injury, termed reactive astrocytosis, is a process defined by increased secretion of growth factors and inflammatory cytokine production. Post-mortem analyses of MBM patients reveal perilesional reactive astrocytosis. Here we demonstrate that astrocyte reactivity promotes MBM growth, using in vitro and in vivo model systems. We identify that astrocytes secrete factors that increase tumor growth and expression of neural development factors. Moreover, pharmacological inhibition of neural development pathways, like Wnt signaling, attenuate the effects of astrocyte secreted factors. We developed a brain adapted melanoma line, D4M3a BrJ, and demonstrate the time course of astrocyte reactivity in vivo in its relationship with tumor growth. Our findings provide evidence that astrocyte reactivity promotes MBM growth and activation of neural development programming, unveiling a new therapeutic avenue for targeting the brain metastatic niche. Citation Format: Julia K. Farnan, Maria R. Cavallo, Edward J. Hartsough, Joshua G. Jackson. Astrocytes activate neuronal programming in melanoma brain metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1361.

Abstract 4483: Distinct spatial distribution patterns of ALK-inhibitor naïve versus ALK-inhibitor treated ALK-positive NSCLC brain metastases

Abstract Background: Non-small cell lung cancer (NSCLC) with anaplastic lymphoma kinase rearrangement (ALK+) has a high affinity to form brain metastases (BrM). The cumulative incidence of BrMs in ALK+ lung cancer is over 50%, despite highly effective ALK tyrosine kinase inhibitors (TKIs) with CNS activity. Pharmacokinetic (PK) data from other CNS-active lung cancer TKIs (e.g., osimertinib) have revealed major brain white vs. gray matter drug concentration differences, raising the possibility of a PK-driven effect on BrM formation and response. This study aims to compare the size and distribution of ALK+ NSCLC BrMs at diagnosis in a TKI-naïve and TKI-exposed cohort. Methods: We retrospectively reviewed brain MRIs from the date of BrM diagnosis for patients with ALK+ NSCLC at Johns Hopkins. Demographic and clinical information were collected by chart review. Each tumor was marked in a standard space brain model in the corresponding anatomic location represented by a sphere of corresponding diameter using 3D Slicer 4.11. FreeSurfer white-gray matter atlases were used to assess BrM distribution. The data for patients who were on TKI vs TKI-naïve at the time of BrM diagnosis were then analyzed separately. T-tests were used to compare the metastatic burden (sum of BrM diameters), mean BrM diameter per patient, number of BM per patient, per individual mean of white matter exclusive (defined as no overlap with gray matter) and deep white matter (≥5mm away from gray matter) BrMs between patient groups. Results: 429 BrMs were identified in 39 patients, with 25 patients being TKI-naïve at the time of BrM diagnosis while 14 patients were on TKI therapy. TKI-exposed patients had significantly smaller BrM diameters than those in the TKI-naïve group (6.1±3.8 vs 10.2±5.5mm, p=0.02). While metastatic burden was very similar between the groups, the mean number of BrM per patient was numerically higher in the TKI-exposed group (10.6±11.9 vs 6.2±9.5; p=0.22). Notably, patients in the TKI-exposed group also had higher numbers of white matter exclusive (3.5±4.4 vs 1.4±2.0, p=0.05) and deep white matter metastases (3.2±4.3 vs 1.3±2.0, p=0.06) than those who were TKI-naïve. Conclusion: Our data highlight the differences in BrM characteristics among ALK+ NSCLC exposed to ALK TKI. TKI therapy was associated with similar BrM burden but smaller individual lesions that were more likely to be exclusive to the white matter where drug concentrations might be significantly lower. These findings suggest that suboptimal drug CNS distribution in the white matter may underly brain progression of ALK+ NSCLC despite TKI therapy. Spatial analyses evaluating ALK TKIs of varying CNS penetrance and later disease time points in more granular anatomic regions are ongoing. Citation Format: Tia Cheunkarndee, Paola Ganem, Kristen A. Marrone, Joseph C. Murray, Josephine L. Feliciano, Christine L. Hann, Susan C. Scott, David Ettinger, Valsamo Anagnostou, Patrick M. Forde, Julie R. Brahmer, Benjamin P. Levy, Vincent Lam, David O. Kamson. Distinct spatial distribution patterns of ALK-inhibitor naïve versus ALK-inhibitor treated ALK-positive NSCLC brain metastases. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4483.

Targeting lung cancer brain metastases: a narrative review of emerging insights for anaplastic lymphoma kinase (ALK)-positive disease.

Lung cancer is commonly associated with brain metastasis formation, and certain subtypes, such as anaplastic lymphoma kinase (ALK) rearranged disease, have an especially high propensity for early and frequent central nervous system (CNS) involvement for which treatment can be challenging. Historical management has centered on surgery and radiation therapy (RT), which persist as mainstays of treatment for large, symptomatic lesions and widespread CNS disease. To date, sustained disease control remains elusive, and the role for effective systemic adjunctive therapies is clear. Here we discuss the epidemiology, genomics, pathophysiology, identification, and management of lung cancer brain metastases with a particular emphasis on systemic treatment of ALK-positive disease according to the best available evidence. Review of PubMed and Google Scholar databases as well as ClinicalTrials.gov provided background and seminal trials for the local and systemic management of ALK rearranged lung cancer brain metastases. The development of effective, CNS-penetrant systemic agents-including alectinib, brigatinib, ceritinib, and lorlatinib-has dramatically changed the management and prevention of ALK rearranged brain metastases. Most notably, there is a burgeoning role for upfront systemic therapy for both symptomatic and incidentally discovered lesions. Novel targeted therapies offer patients a pathway to delay, obviate, or supplement traditional local therapies while minimizing neurologic sequelae of treatment and may reduce the risk of brain metastasis formation. However, the selection of patients to whom local and targeted treatments is offered is not trivial, and the risks and benefits of both must be weighed carefully. More work is needed to establish treatment regimens that yield durable intra- and extracranial disease control.

Abstract B038: Remodeling the extracellular matrix environment and establishing distinct immune cell profiles enables the formation of brain metastasis in non-small cell lung cancer adenocarcinoma

Abstract Dissemination of tumor cells from the primary site of the lung to distant sites in non-small cell lung cancer (NSCLC) is poorly understood. With distinct mutation signatures in patients, altering pathways is critical to preventing tumor cell dissemination to distant sites. Towards this, we characterized 21 "trios" patient-matched brain metastases (BrM), primary tumors (LT), and normal samples (LN), revealing a pattern of extracellular matrix remodeling which suppressed immune cell infiltration. Our objectives were to (i) determine if clinically sampled primary lung tumors encode gene expression patterns distinct from normal tissue, suggestive of increased tumor invasiveness including brain metastasis, and (ii) determine the biologic underpinning of immune-suppressive information carryover from primary lung tumor to brain metastasis. Transformation of the normal lung cells to primary tumor cells suggested a breakdown in ECM axes primarily governed by upregulation of collagen (COL1A1, COL1A2, COL3A1, COL10A1), fibronectin (FN1), and matrix metalloproteinases (MMP7, MMP9, MMP11, MMP12, MMP13, MMP14) genes. Collectively, the primary tumor cells used MMPs to break down the main components of lung ECM and reorganized collagen and fibronectin in the tumor microenvironment to facilitate migration and invasion. Migration and subsequent cell adhesion in the brain microenvironment revealed upregulation of neural cell adhesion molecule (NCAM1) and phosphoprotein 1 (SPP1). These changes in ECM profiles between LT and BrM signify primary tumor cells' adaptation in the brain microenvironment. Further computational deconvolution revealed reduced HLA class II gene expression (HLA-DMA, HLA-DOB, HLA-DPA1, HLA-DPB1, HLA-DQA2, HLA-DQB2, HLA-DRA) correlated with lower CIBERSORTx enrichment scores of immune cell populations in BrM. Overall, using the matched sequencing information, we will present the underlying signaling gradients that dictate dissemination of primary lung tumor cells to the brain environment in the background of altered ECM environment using cellular models harboring EGFR, KRAS, and ALK driver mutations. Citation Format: Albert R. Wang, Jared Brown, Andrew Baschnagel, Darya Buehler, Christina Kendziorski, Gopal Iyer. Remodeling the extracellular matrix environment and establishing distinct immune cell profiles enables the formation of brain metastasis in non-small cell lung cancer adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr B038.

DDDR-03. DEVELOPMENT OF NOVEL ANTI-BRAIN METASTASIS INHIBITORS

Abstract The current standard of care for (surgery and radiation) for brain metastases (BM) is inadequate as BM have a 90% mortality rate within one year of diagnosis, posing a large unmet clinical need. The Singh lab has generated a large in-house biobank of patient-derived BM cell lines that are established from BM patient tumor samples. We use these BM cell lines to generate murine orthotopic xenograft models of BM and interrogate the biological processes that lead to BM. These models have successfully recapitulated all the stages of their respective BM cascades and additionally captured a “premetastatic” population of BM cells that have just seeded the brains of mice before forming mature, clinically detectable tumors. Pre-metastatic cell populations are impossible to detect in human patients but represent a therapeutic window wherein metastasizing cells can be targeted and eradicated before establishing clinically detectable and difficult to treat brain tumors. RNA sequencing of pre-metastatic BM cells revealed a unique deregulated transcriptomic profile that is specific to pre-metastatic cells despite the tumor of origin. Connectivity Map analysis was applied to the gene expression signatures of pre-metastatic BM cells to identity a compound (Drug A) which selectively inhibits BM cell proliferation but is not blood-brain barrier (BBB) penetrant and has not been previously considered in the context of brain metastasis. We synthesized a BBB-penetrant analogue of Drug A and found, using our patient-derived xenograft (PDX) models, that it increased survival benefit relative to both placebo and Drug A. Beginning with this promising scaffold, we will conduct structure-activity hypothesis-driven medicinal chemistry campaigns to optimize this scaffold for brain permeation while maintaining selective anti-BM activity. Development of novel small molecules that target premetastatic BM cells could slow or prevent the formation of BM and dramatically improve the prognosis of at-risk cancer patients.

BSCI-13 DEVELOPMENT OF NOVEL ANTI-BRAIN METASTASIS INHIBITORS

Abstract The current standard of care (surgery and radiation) for brain metastases (BM) is inadequate as BM have a 90% mortality rate within one year of diagnosis, posing a large unmet clinical need. The Singh lab has generated a large in-house biobank of patient-derived BM cell lines that are established from BM patient tumor samples. We use these BM cell lines to generate murine orthotopic xenograft models of BM and interrogate the biological processes that lead to BM. These models have successfully recapitulated all the stages of their respective BM cascades and additionally captured a “pre-metastatic” population of BM cells that have just seeded the brains of mice before forming mature, clinically detectable tumors. Pre-metastatic cell populations are impossible to detect in human patients but represent a therapeutic window wherein metastasizing cells can be targeted and eradicated before establishing clinically detectable and difficult to treat brain tumors. RNA sequencing of pre-metastatic BM cells revealed a unique deregulated transcriptomic profile that is specific to pre-metastatic cells despite the tumor of origin. Connectivity Map analysis was applied to the gene expression signatures of pre-metastatic BM cells to identity a compound (Drug A) which selectively inhibits BM cell proliferation but is not blood-brain barrier (BBB) penetrant and has not been previously considered in the context of brain metastasis. We synthesized a BBB-penetrant analogue of Drug A and found, using our patient-derived xenograft (PDX) models, that it increased survival benefit relative to both placebo and Drug A. Beginning with this promising scaffold, we will conduct structure-activity hypothesis-driven medicinal chemistry campaigns to optimize this scaffold for brain permeation while maintaining selective anti-BM activity. Development of novel small molecules that target pre-metastatic BM cells could slow or prevent the formation of BM and dramatically improve the prognosis of at-risk cancer patients.