Melanoma Brain Metastases Research Articles

RADT-09. CLINICAL OUTCOMES OF FRACTIONATED STEREOTACTIC RADIOTHERAPY FOR INTACT AND POSTOPERATIVE RADIORESISTANT RENAL CELL CARCINOMA AND MELANOMA BRAIN METASTASES

Abstract PURPOSE Fractionated Stereotactic Radiotherapy (FSRT) may be an optimal strategy for radioresistant renal cell carcinoma (RCC) and melanoma brain metastases (BM). We reviewed our institutional experience of FSRT to intact BM and postoperative cavities for patients with melanoma and RCC. METHODS We retrospectively identified consecutive patients with melanoma and renal cell carcinoma with unresected or resected BM treated with FSRT at our institution from 1/2018 to 1/2021. Time to event outcomes were estimated using the Kaplan-Meier method with log-rank tests and multivariable Cox regression analyses. RESULTS We identified 44 patients with a total of 64 BM: 31 intact (48.4%) and 33 resected BMs (51.6%). Thirty-six (81.8%) were melanoma and eight (18.2%) were RCC. The majority of intact BM (n = 22/31; 71%) and cavities (n = 21/33; 64%) were treated to 30 Gy (24-30) in 5 fractions and 25 Gy (24-35), respectively. Median PTV volume for intact BM was 5.04 cc (1.2-19.8) and for resected BM was 16.7 cc (4.8-89.1). Median interval from planning MRI to FSRT was 10 days (3-28). Median time from surgery to FSRT was 37 days (9-90). At 18.6 months median follow-up, local and intracranial distant failures were observed in 4 and 20 patients, respectively. Our cohort had a local recurrence-free survival (LRFS) of 83% and overall survival (OS) of 57% at 12 months; no difference between primary FSRT versus surgery followed by FSRT (p = 0.93 and p = 0.52, respectively). On MVA, higher FSRT dose was associated with better local control (p = 0.01). Radiation Necrosis (RN) was observed in eight treatment areas (12.5%). Neither resection status (p = 0.99) nor PTV volume (p = 0.61) were associated with RN. CONCLUSION FSRT is associated with low rates of toxicity and clinically significant disease control for both intact and resected melanoma and RCC BM, with higher FSRT dose being correlated with improved control.

IMMU-02. IS DUAL AGENT IMMUNOTHERAPY SHIFTING THE EPIDEMIOLOGY OF MELANOMA BRAIN METASTASES? A REAL-WORLD ANALYSIS AND SINGLE-INSTITUTION VALIDATION

Abstract INTRODUCTION Dual agent immunotherapy (dIT) has been paradigm changing in melanoma brain metastasis (MBM). Recent clinical trials have supported the role of dIT for upfront management of small, asymptomatic MBM. Yet, its potential role in extending brain metastasis free survival and decreasing MBM incidence overall has been inadequately explored. Objective: To compare new brain metastasis incidence, median overall survival (OS), and brain metastasis free survival (BMFS) in melanoma patients treated with dIT versus single immunotherapy (sIT). METHODS A real-world deidentified database collating clinical information from 92 organizations (TriNetX, Inc) was queried. Melanoma patients without brain metastases prior to immunotherapy were stratified by treatment (anti-CTLA4 [sIT] and combination anti-CTLA4/ anti-PD1 [dIT]) and propensity score matched. A complementary single-institution retrospective cohort study analyzed melanoma patients treated from 2012-2019. The incidence of new asynchronous MBMs after immunotherapy initiation was compared. Median OS and BMFS were compared via log-rank tests and Cox proportional-hazards model. RESULTS TriNetX identified 8,686 melanoma patients who received immunotherapy (4,585 dIT; 4,101 sIT). MBM prevalence was 9.6%, and 15.6%, for the dIT and sIT cohorts, respectively (p < 0.0001). DIT was associated with a lower likelihood of developing MBM compared to sIT (OR [95%CI], 0.64 [0.61-0.77]). After propensity score matching on demographics and significant comorbidities, OS was not statistically different between treatment groups. On single-institution analysis, 222 melanoma patients were included (89 dIT; 45 anti-CTLA4; 88 anti-PD1). Patients were predominantly stage III at diagnosis (43%) with PD-L1 expression (51%) and BRAF (43%), and NRAS wildtype (50%) mutational status. BMFS was significantly extended in the dIT cohort compared to the anti-CTLA4 or anti-PD1 alone cohorts (406, 217, 139 days, respectively; p< 0.0001). On Cox-proportional hazards model, no covariates significantly contributed to the BMFS difference. CONCLUSION These data highlight the impact of combination anti-CTL4/ anti-PD1 immunotherapy in decreasing BM incidence in melanoma.

MODL-06. THE GUT MICROBIOTA OF BRAIN TUMOR PATIENTS CAN IMPACT IMMUNOTHERAPY EFFICACY IN A PRECLINICAL MODEL OF GLIOMA

Abstract Combination immune checkpoint inhibitors (ICI) can affect durable response in melanoma brain metastases (MBM) but have largely been ineffective for the treatment of glioblastoma (GBM), a primary brain tumor. Recent studies in animal models and humans have suggested that the microbe composition of the gut can influence the effectiveness of ICI in melanoma and other cancers. Our central hypothesis is that the gut microbiome can influence immunotherapy responsiveness for GBM patients. We obtained microbiome (stool) samples from GBM and MBM patients prior to beginning any treatment or surgical interventions. We then transplanted these microbiome samples into gnotobiotic mice to create humanized microbiome mice. We transplanted two GBM patients and two MBM patients microbiome samples to create 4 unique patient-derived humanized microbiome mouse lines (GBM1, GBM2, MBM1, and MBM2). Using 16s ribosomal RNA microbiome sequencing, we found that each patient-derived microbiome mouse line had a unique microbiome composition as measured by relative abundance and diversity of species. Mice from each line were then intracranially injected with GL261 murine glioma cells and treated with the ICI anti-PD-1 or isotype control. We found that MBM1 and GBM2 mice were resistant to anti-PD-1 and did not display prolonged survival with anti-PD-1 treatment. However, GBM1 and MBM2 mice were positive responders to anti-PD-1 and displayed significantly prolonged survival compared to isotype control. Additional microbiome sequencing analyses are ongoing that will reveal positive microbiome profiles among these patient-derived lines, and additional GBM and MBM patient-derived microbiome lines are being created and tested for immunotherapy efficacy. Ultimately, understanding how certain microbial communities can enhance the effectiveness of immunotherapy may lead to the development of new approaches that include modification or transplantation of microbe communities in GBM patients for increased therapeutic impact.

NCOG-02. MANAGEMENT OF PATIENTS WITH MELANOMA BRAIN METASTASES AND PRIOR SYSTEMIC TREATMENT EXPOSURE: A SINGLE-CENTER EXPERIENCE

Abstract Although systemic therapy (ST) for melanoma patients with untreated brain metastases (BrM) has activity, ST options for patients with melanoma BrM that develop on or after ST are limited. In this single-center retrospective study, we describe the characteristics and survival outcomes of patients aged > 18 years with metastatic melanoma and who developed BrM > 90 days after their first dose of checkpoint inhibitor (CPI) or targeted therapy (TT). Relevant clinical data and data on ST prior to and after BrM diagnosis were collected. MRIs were reviewed to assess intracranial progression-free survival (IC-PFS) as per RANO-BM criteria. The primary outcome was overall survival (OS). Cox regression model was applied to identify factors associated with OS. Between 2010 and 2019, we identified 103 patients with median age 56 (29-92) years, 69 (67%) of whom were male; 57 (55%) had BRAF V600-mutant tumors. Ninety-four (91%) had no known BrM at the time of first-line therapy. Median number of BrM was 3 (1-58), median number of prior ST was 1 (1-5), 75 (73%) had prior CPI exposure and 70 (68%) were on concurrent CPI or TT at the time of BrM diagnosis. Local treatments included SRS in 43 (42%) and WBRT in 46 (44%) patients. From BrM diagnosis, median IC-PFS and OS were 3.5 (95% CI 2.6-4.3) and 6.9 (95% CI 5.2-8.6) months, respectively. Adverse prognostic factors were: BRAF wild-type (HR 2.04, 95% CI 1.15-3.64), ECOG 2-4 (HR 3.55, 95% CI 1.93-6.53), and increasing number of prior ST (HR 1.62, 95% CI 1.23-2.13). CPI therapy that was continued, started, or restarted after BrM was associated with improved median OS compared to non-ICI therapy (9.9 vs. 3.5 months, HR 0.45, 95% CI 0.27-0.74). In conclusion, our data support development of CPI-based trials for patients who experience progression with BrM on or after modern ST.

IMMU-49. BETA-ADRENERGIC BLOCKADE LICENSES THE USE OF IMMUNOTHERAPY IN PRIMARY AND METASTATIC BRAIN TUMORS

Abstract Immunotherapy is less effective against intracranial metastases compared to extracranial metastases and ineffective against primary brain tumors such as glioblastoma. Brain tumors present a unique challenge to in the context of immunotherapy, as these patients are immunosuppressed not just locally at the tumor, but also outside the CNS. Importantly, systemic immunosuppression observed in brain tumor patients limits the capacity of the immune system to respond to immunotherapy. Through this work we present a novel axis of immunosuppression in patients with intracranial tumors and demonstrate that overactive adrenergic signaling is a major barrier to immunotherapeutic success.Our data indicate that combining beta-adrenergic blockade with immunotherapy provides a survival benefit in the setting of brain tumors, where immunotherapy alone has proven ineffective. We demonstrate that this survival benefit is driven by a remodeling of the tumor microenvironment with an increase in cDC1s and CD8+ T cells, as well as an increase in CD40-CD40L signaling, suggesting the immune system is poised to respond. Further, we demonstrate that beta-adrenergic blockade can overcome systemic immunosuppression to restore the capacity of T cells to respond to an immune stimulus. Further, using the SEER-Medicaid database, we retrospectively examined outcomes in patients with melanoma and lung adenocarcinoma brain metastasis who received checkpoint blockade therapy alone vs those concurrently receiving beta-blocker therapy. We found that patients receiving combination therapy showed increased overall survival compared to those receiving checkpoint blockade alone. We then validated these findings in preclinical models of glioma, demonstrating that combining immunotherapy and propranolol, a widely-prescribed FDA-approved beta-blocker, extended survival. Moving forward, we suggest that combination therapy with beta-blocker and immunotherapy, particularly checkpoint blockade, represents a promising translational treatment platform for patients with primary or metastatic intracranial malignancies.

Targeting Translation and the Cell Cycle Inversely Affects CTC Metabolism but Not Metastasis.

Melanoma brain metastasis (MBM) is significantly associated with poor prognosis and is diagnosed in 80% of patients at autopsy. Circulating tumor cells (CTCs) are "seeds" of metastasis and the smallest functional units of cancer. Our multilevel approach has previously identified a CTC RPL/RPS gene signature directly linked to MBM onset. We hypothesized that targeting ribogenesis prevents MBM/metastasis in CTC-derived xenografts. We treated parallel cohorts of MBM mice with FDA-approved protein translation inhibitor omacetaxine with or without CDK4/CDK6 inhibitor palbociclib, and monitored metastatic development and cell proliferation. Necropsies and IVIS imaging showed decreased MBM/extracranial metastasis in drug-treated mice, and RNA-Seq on mouse-blood-derived CTCs revealed downregulation of four RPL/RPS genes. However, mitochondrial stress tests and RT-qPCR showed that omacetaxine and palbociclib inversely affected glycolytic metabolism, demonstrating that dual targeting of cell translation/proliferation is critical to suppress plasticity in metastasis-competent CTCs. Equally relevant, we provide the first-ever functional metabolic characterization of patient-derived circulating neoplastic cells/CTCs.

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.

Heterogeneity in the Metastatic Microenvironment: JunB-Expressing Microglia Cells as Potential Drivers of Melanoma Brain Metastasis Progression.

Reciprocal signaling between melanoma brain metastatic (MBM) cells and microglia reprograms the phenotype of both interaction partners, including upregulation of the transcription factor JunB in microglia. Here, we aimed to elucidate the impact of microglial JunB upregulation on MBM progression. For molecular profiling, we employed RNA-seq and reverse-phase protein array (RPPA). To test microglial JunB functions, we generated microglia variants stably overexpressing JunB (JunBhi) or with downregulated levels of JunB (JunBlo). Melanoma-derived factors, namely leukemia inhibitory factor (LIF), controlled JunB upregulation through Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling. The expression levels of JunB in melanoma-associated microglia were heterogeneous. Flow cytometry analysis revealed the existence of basal-level JunB-expressing microglia alongside microglia highly expressing JunB. Proteomic profiling revealed a differential protein expression in JunBhi and JunBlo cells, namely the expression of microglia activation markers Iba-1 and CD150, and the immunosuppressive molecules SOCS3 and PD-L1. Functionally, JunBhi microglia displayed decreased migratory capacity and phagocytic activity. JunBlo microglia reduced melanoma proliferation and migration, while JunBhi microglia preserved the ability of melanoma cells to proliferate in three-dimensional co-cultures, that was abrogated by targeting leukemia inhibitory factor receptor (LIFR) in control microglia-melanoma spheroids. Altogether, these data highlight a melanoma-mediated heterogenous effect on microglial JunB expression, dictating the nature of their functional involvement in MBM progression. Targeting microglia highly expressing JunB may potentially be utilized for MBM theranostics.

1085O Atezolizumab, bevacizumab, and cobimetinib (TACo) in patients (pts) with PD1 refractory melanoma brain metastases (MBM)

1085O Atezolizumab, bevacizumab, and cobimetinib (TACo) in patients (pts) with PD1 refractory melanoma brain metastases (MBM)

1135P Comparison of intracranial (IC) response assessment criteria in patients (pts) with melanoma brain metastases (MBM) treated with combination nivolumab (NIVO) plus ipilimumab (IPI) in CheckMate 204

1135P Comparison of intracranial (IC) response assessment criteria in patients (pts) with melanoma brain metastases (MBM) treated with combination nivolumab (NIVO) plus ipilimumab (IPI) in CheckMate 204

1134P Safety and efficacy of low dose (LD) ipilimumab (Ipi) + pembrolizumab (pem) in checkpoint inhibitor (CPI) naïve patients (pts) with melanoma brain metastases (MBM)

1134P Safety and efficacy of low dose (LD) ipilimumab (Ipi) + pembrolizumab (pem) in checkpoint inhibitor (CPI) naïve patients (pts) with melanoma brain metastases (MBM)

1137P Treatment strategies and survival outcomes in a nationwide, population-based cohort of patients with melanoma brain metastases: The role of planned shift in systemic therapy and postoperative stereotactic radiotherapy

1137P Treatment strategies and survival outcomes in a nationwide, population-based cohort of patients with melanoma brain metastases: The role of planned shift in systemic therapy and postoperative stereotactic radiotherapy

Intracranial Control with Combined Dual Immune-Checkpoint Blockade and SRS for Melanoma and NSCLC Brain Metastases

It is unknown whether the use of dual immune-checkpoint inhibition (D-ICI) combined with stereotactic radiosurgery (SRS) affects local control of brain metastases (BMs). We sought to characterize the efficacy of SRS and D-ICI in patients with BMs in a large, single-institution cohort. Patients with melanoma and non-small cell lung cancer (NSCLC) BMs treated with SRS from January 1, 2016 to August 1, 2022 were evaluated. Patients were stratified by treatment with D-ICI versus single ICI (S-ICI). Concurrent ICI was defined as ICI given within four weeks of SRS. Local recurrence (LR), intracranial progression (IP), and overall survival (OS) were estimated using competing risk and Kaplan-Meier analyses. IP included both local and distant intracranial recurrence. One thousand seven hundred four SRS-treated BMs from 288 patients met inclusion criteria. 55% of patients were symptomatic from their BMs at presentation. Median age, KPS, number of lesions, and SRS courses were 64 (Q1Q3:56-70.5), 90 (80-90), 2 (1-4), and 1 (1-2), respectively. One hundred twenty-eight (44%) melanoma and 160 (56%) NSCLC patients were included. 82 (28.5%), 129 (44.8%), and 77 (26.7%) patients were treated with D-ICI, S-ICI, or SRS alone. Median SRS dose, fractions, and PTV were 20 (Q1Q3:20-25), 1 (1-5), and 0.3cc3 (0.1-1.2). The median follow-up was 14.3 months. One hundred twenty-seven (7.45%) BMs recurred post-SRS and the median time to LR was 4.8 months (Q1Q3:3.0-9.2). On competing risk analysis, LR was significantly reduced with D-ICI (HR: 0.452, p = 0.0024), but not with S-ICI (HR: 0.693, p = 0.0596) compared to SRS alone. The 1-year LR was 3.77% (95% CI = 2.19-6.00), 6.8% (5.19-8.70), and 8.96% (6.48-11.93) with D-ICI, S-ICI, and SRS alone. The median time to IP was 4.1 months (Q1Q3 = 2.9-9.5). On competing risk analysis, IP was significantly reduced with D-ICI (HR = 0.638, p = 0.031), but not with S-ICI (HR = 0.756, p = 0.106) compared to SRS alone. 1-year IP was 40.05% (95% CI = 29.14-50.70), 51.86% (42.78-60.19), and 58.49% (46.30-68.84) with D-ICI, S-ICI, and SRS alone. Concurrent delivery of D-ICI and SRS significantly reduced IP (HR = 0.463, p = 0.0071), whereas other combinations of timing and ICI did not reach significance. Median OS was 11.9 months after SRS. On Kaplan Meier analysis, OS was significantly improved with D-ICI (HR = 0.616, 95% CI = 0.412-0.923, p = 0.019), but not with S-ICI (HR = 0.877, 95% CI = 0.633-1.217, p = 0.433) compared to SRS alone. Hospitalizations (p = 0.021) and immune-related adverse events (irAEs) (p<0.001) were increased with D-ICI. Any grade radiation necrosis (RN) was also increased with D-ICI (p = 0.013), but neurologic adverse events were comparable across cohorts (p = 0.572). D-ICI combined with SRS was associated with improved local control, intracranial control, and overall survival compared to SRS alone, whereas S-ICI was not associated with an improvement in these outcomes. However, D-ICI was also associated with increased risks of irAEs and RN.

Clinical Outcomes Following an Initial Stereotactic Radiosurgery Course for Brain Metastases from Melanoma

Brain metastases (BM) are common in melanoma patients. The effect of gene mutations is not well characterized since first-line metastatic therapy has shifted from chemotherapy (CHT) to molecularly targeted therapies (TT) and immunotherapy (IO). We report outcomes of melanoma BM patients stratified by molecular subtype and pre-stereotactic radiosurgery (SRS) systemic therapy. We identified all patients completing an initial SRS course for BM at two institutions between 1/2015 and 12/2020. Patients who had prior WBRT and/or resection were eligible. Demographic and clinical parameters were collected, along with melanoma tumor molecular characteristics. Intracranial progression (ICP) was defined as any radiographic distant and/or in-field progression per multidisciplinary consensus. Overall survival (OS) and freedom from ICP (FFICP) were estimated via the Kaplan Meier method. From a total of 1383 SRS BM patients, we identified 118 (8.5%) with melanoma. Median follow up was 8.7 months, median age 64 years (IQR 51-72), 81% had cutaneous origin, and 55% had a KPS of 90-100. Molecular subtypes included BRAF (45%), NRAS (9.3%), and c-KIT (3.4%). Overall, 61% received IO prior to SRS, while 25% and 9.3% received TT and CHT prior to SRS respectively. 60% of patients harboring a mutation received IO as first line therapy, 10% received TT, and 30% received both TT and IO prior to SRS. BRAFmut patients more likely to have received TT prior to SRS (43% vs 9.2%, p<0.001) compared to BRAFwt patients. Median OS was 9.7 months (95% CI 7.8-13) and was not significantly different from non-melanoma patients (p = 0.6). Median FFICP was worse for melanoma patients (5.9 mos, 95% CI 3.5-8.5) than non-melanoma patients (8.96 mos, 95% CI 8.2-9.7, p = 0.009). A total of 72 ICP events occurred, with 56 (77.8%) distant ICP cases, 3 (4.2%) in-field ICP, and 13 (18%) ICP events that were radionecrosis (RN) only. RN was associated with the presence of a targetable mutation (18% vs 2%, p = 0.006) and receipt of TT pre-SRS (36% vs 9.8%, p = 0.001). BRAFmut patients had significantly worse FFICP (3.8 mos, 95% CI 3.0-6.8) compared to BRAFwt patients (8.5 mos, 95% CI 5.8-30.2, p = 0.006), although median OS was not significantly different (9.6 mos, 95% CI 6.9-16 vs 10.7 mos, 95% CI 6.7-15.5, p = 0.8). NRASmut was associated with better FFICP (29 mos, 95% CI 2.94-NA, p = 0.02). In this modern, multi-institutional cohort of SRS patients, melanoma BM patients had worse FFICP compared to non-melanoma BM patients, and BRAFmut patients had worse FFICP than BRAFwt patients. RN was associated with mutational status and receipt of TT pre-SRS. OS did not vary significantly across groups. This analysis may help inform systemic therapy decisions and future genomic studies for patients with BMs from melanoma.

Inhibition of extracellular vesicle-derived miR-146a-5p decreases progression of melanoma brain metastasis via Notch pathway dysregulation in astrocytes.

Melanoma has the highest propensity of all cancers to metastasize to the brain with a large percentage of late-stage patients developing metastases in the central nervous system (CNS). It is well known that metastasis establishment, cell survival, and progression are affected by tumour-host cell interactions where changes in the host cellular compartments likely play an important role. In this context, miRNAs transferred by tumour derived extracellular vesicles (EVs) have previously been shown to create a favourable tumour microenvironment. Here, we show that miR-146a-5p is highly expressed in human melanoma brain metastasis (MBM) EVs, both in MBM cell lines as well as in biopsies, thereby modulating the brain metastatic niche. Mechanistically, miR-146a-5p was transferred to astrocytes via EV delivery and inhibited NUMB in the Notch signalling pathway. This resulted in activation of tumour-promoting cytokines (IL-6, IL-8, MCP-1 and CXCL1). Brain metastases were significantly reduced following miR-146a-5p knockdown. Corroborating these findings, miR-146a-5p inhibition led to a reduction of IL-6, IL-8, MCP-1 and CXCL1 in astrocytes. Following molecular docking analysis, deserpidine was identified as a functional miR-146a-5p inhibitor, both in vitro and in vivo. Our results highlight the pro-metastatic function of miR-146a-5p in EVs and identifies deserpidine for targeted adjuvant treatment.

P06.01.A HAS THE USE OF DUAL AGENT IMMUNOTHERAPY BEEN ALTERING THE INCIDENCE OF MELANOMA BRAIN METASTASES? A POPULATION-LEVEL ANALYSIS AND SINGLE-INSTITUTION VALIDATION

Abstract BACKGROUND Dual agent immunotherapy (dIT) has revolutionized the treatment of advanced melanoma, with recent clinical trials demonstrating its effectiveness in managing small, asymptomatic melanoma brain metastases (MBM) in the upfront setting. However, its potential role in preventing MBM has not been thoroughly investigated. MATERIAL AND METHODS A retrospective analysis was performed on the TriNetX database, which compiles clinical data from 92 healthcare organizations. Melanoma patients without MBM at diagnosis were divided into two groups: those who received ipilimumab alone (single immunotherapy, sIT) and those who received ipilimumab and nivolumab (dIT). The study compared the frequency of new asynchronous MBM diagnosis among the cohorts and analyzed the median overall survival (OS) of MBM patients using Kaplan Meier analysis and log-rank tests. Additionally, a retrospective cohort validation study was conducted on a sample of randomly selected patients treated at a single institution between 2012-2019. Electronic medical records were reviewed for demographics, melanoma treatment history, and clinical outcomes. RESULTS TriNetX identified a total of 732,555 melanoma patients, including 717,408 who did not receive immunotherapy (no-IT), 4,585 who received dual immunotherapy (dIT), and 4,101 who received single immunotherapy (sIT). The mean ages at melanoma brain metastases (MBM) diagnosis were 66.9, 61.5, and 63.2 years for each respective group. The prevalence of MBM was 1.5%, 9.6%, and 15.6% for no-IT, dIT, and sIT groups, respectively (p &amp;lt; 0.0001). DIT was associated with a lower rate of MBM compared to sIT(OR [95%CI], 0.64 [0.61-0.77]). After propensity score matching, the median overall survival for MBM patients was not statistically different between the no-IT, dIT, and sIT groups (347, 400, 414 days, respectively). In the validation group of 90 patients (30 no-IT, 27 sIT, 34 dIT), predominantly male (61.5%), stage III (62.5%), the prevalence of MBM was 13.8%, 59%, and 38.2% for each respective group for developing MBM (OR [95%CI], 2.35 [0.84-6.60], p=0.08). The mean time between immunotherapy initiation and MBM was 305 days for dIT and 500 days for sIT for patients who developed MBM. CONCLUSION The results suggest that using a combination of ipilimumab and nivolumab immunotherapy could be effective in reducing the incidence of brain metastases in advanced melanoma patients. Further investigation is needed to explore the potential preventive role of dIT in MBM development in this patient population.

P10.03.A ANTIPSYCHOTICS TO TREAT BRAIN TUMORS: DRUG REPURPOSING TO BYPASS THE BLOOD BRAIN BARRIER

Abstract BACKGROUND Approximately half of late-stage melanoma patients develop brain metastases (BM), once metastasized to the brain, survival is generally measured in months. Current treatments, although increasingly effective, are not sufficient for this patient group, necessitating development of new therapeutic options. Drugs targeting BM specifically are a scarcity. To broaden therapeutic options, drug repurposing, i.e. novel uses of drugs already approved for other medical conditions, may prove to be a valuable asset. By design, antipsychotics effectively cross an intact blood-brain barrier. Interestingly, although carrying an increased burden of comorbidity, the schizophrenic population has a similar incidence of cancer when compared to the normal population. Hypotheses regarding the antitumor effect of antipsychotics have therefore been postulated along with several other theories that seek to explain these seemingly contradictory incidence rates. We currently present preliminary data showing that clozapine, a second-generation antipsychotic, effectively inhibits growth of human melanoma brain metastasis (MBM) cell lines in vitro. Objective: To explore the potential of antipsychotics in treating MBM. METHODS Cell cultures including H1, H2, H3 MBM cell lines, as well as normal human astrocytes (NHA) were selected for our experiments. Monolayer, 3D, and IncuCyte viability experiments were performed to determine IC50 doses. FBRO, fetal rat brain organoids were used to study clozapine’s effect on the normal brain environment. Cell migration was measured by scratch wound assays. Apoptosis was studied by flow cytometry. Colony formation assays were performed using 2D clonogenic assays. A protein array was used to find signaling proteins potentially affected by clozapine, which where verified by western blots. RESULTS A viability screening using 6 different neuroleptics showed that clozapine was most effective in inhibiting MBM cell viability, with a favorable therapeutic window to astrocytes. Doses significantly above MBM IC50 doses did not affect viability of brain organoids. MBM cells exhibited a dose-dependent inhibition of cell proliferation, migration, and clonogenic formation. Flow cytometry demonstrated that apoptosis was a major mechanism of cytotoxicity. The protein array showed that CCL3, IL8 and VEGF were downstream targets of clozapine. These results were confirmed by western blots. A partnership with the Dept. of Chemistry (UiB) has resulted in the development and testing of several novel clozapine derivates to reduce therapeutic doses and hopefully minimize potential side effects. CONCLUSION Clozapine shows proof of concept in treating BM with antipsychotics and should be explored further as an adjuvant treatment for melanoma patients at risk of developing brain metastasis.

P10.02.B THE PSYCHOTROPIC AGENT THIORIDAZINE IMPEDES MELANOMA BRAIN METASTASIS CELL ACTIVITY THROUGH INHIBITION OF AUTOPHAGY

Abstract BACKGROUND Neural tissue and melanocytes share the same germ layer in early embryonic development. It is then perhaps not by coincidence that melanoma is one of the most common cancer types to metastasize to the brain. With aggressive treatment the median survival of melanoma brain metastases (MBM) is now estimated to be approximately 13 months. Targeted therapies and immunotherapy have armed us with new systemic weapons and shown great responses, but unfortunately most of these patient relapse. Drug repurposing, using old drugs for new purposes, has had several successes for other diseases. The anti-psychotic drug thioridazine (THD), a dopamine receptor 2 antagonist, with properties to cross an intact blood brain barrier, has earlier shown promising effects on melanoma cells that escaped prior treatment and on cancer stem cells. However, the therapeutic effects on MBM have not been previously investigated. MATERIAL AND METHODS We used three BRAF V600E (H1, H2 and H10) and one L577F mutated patient derived MBM cell lines (H3) developed in our lab in our experiments. A monolayer viability assay (WST-1) was utilized to determine IC50 doses. Migrational and proliferational effects of THD was studied by IncuCyte live cell imaging. Colony forming properties and the ability of cells to grow in an anchorage independent environment after THD treatment was investigated using a 2D clonogenic assay and a 3D soft agar model. A potential therapeutic window was assessed through normal human astrocytes (NHA) and fetal rat brain organoids (FRBO). Apoptosis and necrosis were studied by Annexin V/propidium iodide (PI) double staining followed by flow cytometric analysis after 72 hours of treatment. Western blots after THD treatment was done to elucidate underlying molecular mechanisms. RESULTS Cell viability studies showed that THD exerted a dose-dependent inhibition of tumor cell viability (IC50 doses between 9-12 µM), while NHA tolerated similar drug concentrations. Tumor cell migration and proliferation were almost completely inhibited with concentrations below the IC50 doses. An inhibition of clonogenic formation and 3D growth was also observed. Bright field microscopy showed changes in MBM morphology in monolayers, but FRBOs were intact after drug treatment. Apoptosis in MBM cells was induced after treatment with THD through PARP/cleaved caspase 3/Bcl-2. Expression levels of LC3B-II and p62 were significant increase in treated cells, indicating inhibition of autophagic flux at a late stage. CONCLUSION Our data shows that THD has a strong selective cytotoxicity in MBM cells through inhibition of autophagic flux, with a minimal effect on NHA and FBRO.

P10.19.A COMBINED TREATMENT USING MAPK AND PI3K SIGNALING PATHWAYS INHIBITORS EFFECTIVELY REDUCES GROWTH OF MELANOMA BRAIN METASTASIS CELLS IN VITRO

Abstract BACKGROUND Brain metastasis is associated with poor prognosis, and median survival time from the time of diagnosis for cancer patients with brain metastases is only a few months. Brain metastases are estimated to occur in 20-40% of cancer patients. All solid tumors may spread to the brain, but the risk of developing brain metastases is higher in breast cancer, lung cancer and melanoma. Standard treatment of melanoma brain metastases (MBM) includes radiation therapy and surgery. In melanoma, the mitogen activated protein kinase (MAPK) and the phosphoinositide 3-kinase (PI3K) signaling pathways are often activated by genetic alterations. An activation mutation (BRAFV600E) in the MAPK pathway is commonly found in melanoma refractory to therapy. This mutation leads to increased proliferation and tumor cell survival. Previous studies show that BRAF-inhibitors block the increase in cell proliferation induced by the activated BRAF gene, however, many of the patients develop drug resistance within a few months. Objectives: In this project, we aimed to show that drugs targeting BRAF (vemurafenib) and PI3K pathways (buparlisib) used in combination effectively inhibit growth of treatment resistant MBM cells. MATERIAL AND METHODS Our research lab has previously developed human MBM cell lines, which have been made resistant towards vemurafenib treatment. To study the potential antitumoral effects of combined treatment we used these cells in several in vitro assays such as cell viability and proliferation, cell migration, colony forming assay, spheroid growth, apoptosis by IncuCyte and western blot to confirm effects on signaling pathways. RESULTS We found that combination treatment reduced the viability of resistant MBM cells, as well as their ability to proliferate. Further, the cells showed less ability to migrate after therapy. Altered cell morphology was also seen. Initial results show effects on colony formation and increased apoptosis after combined treatment. CONCLUSION A combination of MAPK and PI3K inhibitors effectively inhibits growth and viability of treatment resistant human MBM cells, compared to single drug treatment alone. The results support clinical use of combined therapy for melanoma patients with metastatic disease.

A heterodimer of α and β hemoglobin chains functions as an innate anticancer agent.

Metastatic (as well as tumor) microenvironments contain both cancer-promoting and cancer-restraining factors. The balance between these opposing forces determines the fate of cancer cells that disseminate to secondary organ sites. In search for microenvironmental drivers or inhibitors of metastasis, we identified, in a previous study, the beta subunit of hemoglobin (HBB) as a lung-derived antimetastatic factor. In the present study, exploring mechanisms regulating melanoma brain metastasis, we discovered that brain-derived factors restrain proliferation and induce apoptosis and necrosis of brain-metastasizing melanoma cells. Employing various purification procedures, we identified a heterodimer composed of hemoglobin alpha and beta chains that perform these antimetastatic functions. Neither the alpha nor the beta subunit alone was inhibitory. An alpha/beta chain dimer chemically purified from human hemoglobin inhibited the cell viability of primary melanomas, melanoma brain metastasis (MBM), and breast cancer cell lines. The dimer-induced DNA damage, cell cycle arrest at the SubG1 phase, apoptosis, and significant necrosis in four MBM cell lines. Proteomic analysis of dimer-treated MBM cells revealed that the dimer downregulates the expression of BRD4, GAB2, andIRS2 proteins, playing crucial roles in cancer cell sustainability and progression. Thus, we hypothesize that the hemoglobin dimer functions as a resistance factor against brain-metastasizing cancer cells.