Unique genomic alterations in the circulating tumor DNA of patients with solid tumors brain metastases

Background

Although serum circulating tumor DNA (ctDNA) is routine, data from patients with brain metastases (BrMs) is limited. We assessed genomic alterations in ctDNA from patients with solid tumor BrMs in 3 groups: Isolated BrMs with stable extracranial disease (iCNS), concurrent brain and extracranial progression (cCNS), and extracranial progression with no active BrMs (eCNS). We also compared ctDNA alterations between patients with and without BrMs.

Methods

Patients with a Guardant360 ctDNA profile with (n = 253) and without BrMs (n = 449) from the Duke Molecular Registry between January 2014 and December 2020 were identified. Actionable alterations were defined as FDA-recognized or standard-of-care biomarkers. Disease status was determined via investigator assessment within 30 days of ctDNA collection.

Results

Among the 253 patients with BrMs: 29 (12%) had iCNS, 160 (63%) cCNS, and 64 (25%) eCNS. Breast (BC; 12.0%) and non-small cell lung cancer (NSCLC; 76.4%) were the most common tumor types. ESR1 (60% vs 25%, P < .001) and BRCA2 (17% vs 5%, P = .022) were more frequent in BC BrMs. In NSCLC BrMs, EGFR alterations were most frequent in the iCNS group (iCNS: 67%, cCNS: 40%, eCNS:37%, P = .08) and in patients with BrMs (36% vs 17%, P < .001). Sequencing from both brain tissue and ctDNA were available for 8 patients; 7 (87.5%) had identical alterations.

Conclusions

This study illustrates the feasibility of detecting alterations from ctDNA among patients with BrMs. A higher frequency of actionable mutations was observed in ctDNA in patients with BrMs. Additional studies comparing ctDNA and alterations in BrMs tissue are needed to determine if ctDNA can be considered a surrogate to support treatment decisions.

Triple Negative Breast Cancer and Brain Metastases

The treatment of metastatic breast cancer (MBC) has improved over the past decade, however prognosis continues to be mitigated by the fact that about 1 in 5 patients with MBC will develop brain metastases (BrM) during their metastatic disease course. 1 This number is even higher for patients with triple-negative breast cancer (TNBC), with studies showing as high as 40% of patients developing BrM. 2, 3 Studies have shown that TNBC portends a worse survival after a diagnosis of BrM compared with non-TNBC subtypes. 4 Given the unique location and biologic properties of BrM, treatment options have historically been limited. Challenges to the treatment of TNBC BrM include a lack of targeted therapies and difficulties in delivery of drug to the brain past the blood-brain barrier (BBB). Herein, we will review the advances in local and systemic therapies to most effectively treat patients with TNBC BrM, including therapies on the horizon currently in clinical trials.

Durable responses in patients with HER2+ breast cancer and leptomeningeal metastases treated with trastuzumab deruxtecan

Leptomeningeal metastases (LM) are a devastating complication of HER2 + metastatic breast cancer (MBC), with no effective treatments. In a case series of 8 patients with heavily pretreated HER2 + MBC and progressing LM, all 8 patients (100%) derived clinical benefit from Trastuzumab deruxtecan (TDXd), and 4 patients (50%) had an objective partial response based on formal neuroradiology MRI reads using the EORTC/RANO-LM Revised-Scorecard. T-DXd warrants further study in LM in HER2 + MBC and solid tumors where T-DXd may be active.

Brain metastasis as the first and only metastatic relapse site portends worse survival in patients with advanced HER2 + breast cancer

PURPOSE

Current systemic therapy guidelines for patients with HER2 + breast cancer brain metastases (BCBrM) diverge based on the status of extracranial disease (ECD). An in-depth understanding of the impact of ECD on outcomes in HER2 + BCBrM has never been performed. Our study explores the implications of ECD status on intracranial progression-free survival (iPFS) and overall survival (OS) after first incidence of HER2 + BCBrM and radiation.

METHODS

A retrospective analysis was performed of 151 patients diagnosed with initial HER2 + BCBrM who received radiation therapy to the central nervous system (CNS) at Duke between 2008 and 2021. The primary endpoint was iPFS defined as the time from first CNS radiation treatment to intracranial progression or death. OS was defined as the time from first CNS radiation or first metastatic disease to death. Systemic staging scans within 30 days of initial BCBrM defined ECD status as progressive, stable/responding or none (isolated brain relapse).

RESULTS

In this cohort, > 70% of patients had controlled ECD with either isolated brain relapse (27%) or stable/responding ECD (44%). OS from initial metastatic disease to death was markedly worse for patients with isolated intracranial relapse (median = 28.4 m) compared to those with progressive or stable/responding ECD (48.8 m and 71.5 m, respectively, p = 0.0028). OS from first CNS radiation to death was significantly worse for patients with progressive ECD (16.9 m) versus stable/responding (36.6 m) or isolated intracranial relapse (28.4 m, p = 0.007). iPFS did not differ statistically based on ECD status. Receipt of systemic therapy after first BCBrM significantly improved iPFS (HR 0.45, 95% CI: 0.25-0.81, p = 0.008) and OS (HR: 0.43 (95% CI: 0.23-0.81); p = 0.001).

CONCLUSION

OS in patients with HER2 + isolated BCBrM was inferior to those with concurrent progressive or stable/responding ECD. Studies investigating initiation of brain-penetrable HER2-targeted therapies earlier in the disease course of isolated HER2 + intracranial relapse patients are warranted.

Systemic Therapy Approaches for Breast Cancer Brain and Leptomeningeal Metastases

OPINION STATEMENT

Brain metastasis arising from breast cancer is associated with a poor prognosis. Various systemic chemotherapy and targeted therapies which are effective against breast cancer often fail to provide benefits against brain metastasis. This is mainly due to limited penetration of the therapies across the blood-brain barrier, and divergent evolution of brain metastasis compared to the primary tumor. Thus, brain metastasis is typically treated upfront with local therapies, such as surgery and radiation, followed by systemic therapies. Systemic therapies with CNS permeability are favored in patients with brain metastasis. This paper reviews various systemic therapy options for breast cancer brain metastasis.

Comprehensive Analysis of the Immunogenomics of Triple-Negative Breast Cancer Brain Metastases From LCCC1419

Background

Triple negative breast cancer (TNBC) is an aggressive variant of breast cancer that lacks the expression of estrogen and progesterone receptors (ER and PR) and HER2. Nearly 50% of patients with advanced TNBC will develop brain metastases (BrM), commonly with progressive extracranial disease. Immunotherapy has shown promise in the treatment of advanced TNBC; however, the immune contexture of BrM remains largely unknown. We conducted a comprehensive analysis of TNBC BrM and matched primary tumors to characterize the genomic and immune landscape of TNBC BrM to inform the development of immunotherapy strategies in this aggressive disease.

Methods

Whole-exome sequencing (WES) and RNA sequencing were conducted on formalin-fixed, paraffin-embedded samples of BrM and primary tumors of patients with clinical TNBC (n = 25, n = 9 matched pairs) from the LCCC1419 biobank at UNC—Chapel Hill. Matched blood was analyzed by DNA sequencing as a comparison for tumor WES for the identification of somatic variants. A comprehensive genomics assessment, including mutational and copy number alteration analyses, neoantigen prediction, and transcriptomic analysis of the tumor immune microenvironment were performed.

Results

Primary and BrM tissues were confirmed as TNBC (23/25 primaries, 16/17 BrM) by immunohistochemistry and of the basal intrinsic subtype (13/15 primaries and 16/19 BrM) by PAM50. Compared to primary tumors, BrM demonstrated a higher tumor mutational burden. TP53 was the most frequently mutated gene and was altered in 50% of the samples. Neoantigen prediction showed elevated cancer testis antigen- and endogenous retrovirus-derived MHC class I-binding peptides in both primary tumors and BrM and predicted that single-nucleotide variant (SNV)-derived peptides were significantly higher in BrM. BrM demonstrated a reduced immune gene signature expression, although a signature associated with fibroblast-associated wound healing was elevated in BrM. Metrics of T and B cell receptor diversity were also reduced in BrM.

Conclusions

BrM harbored higher mutational burden and SNV-derived neoantigen expression along with reduced immune gene signature expression relative to primary TNBC. Immune signatures correlated with improved survival, including T cell signatures. Further research will expand these findings to other breast cancer subtypes in the same biobank. Exploration of immunomodulatory approaches including vaccine applications and immune checkpoint inhibition to enhance anti-tumor immunity in TNBC BrM is warranted.

Systemic Therapy Type and Timing Effects on Radiation Necrosis Risk in HER2+ Breast Cancer Brain Metastases Patients Treated With Stereotactic Radiosurgery

Background

There is a concern that HER2-directed systemic therapies, when administered concurrently with stereotactic radiosurgery (SRS), may increase the risk of radiation necrosis (RN). This study explores the impact of timing and type of systemic therapies on the development of RN in patients treated with SRS for HER2+ breast cancer brain metastasis (BCBrM).

Methods

This was a single-institution, retrospective study including patients >18 years of age with HER2+ BCBrM who received SRS between 2013 and 2018 and with at least 12-month post-SRS follow-up. Presence of RN was determined via imaging at one-year post-SRS, with confirmation by biopsy in some patients. Demographics, radiotherapy parameters, and timing (“during” defined as four weeks pre- to four weeks post-SRS) and type of systemic therapy (e.g., chemotherapy, HER2-directed) were evaluated.

Results

Among 46 patients with HER2+ BCBrM who received SRS, 28 (60.9%) developed RN and 18 (39.1%) did not based on imaging criteria. Of the 11 patients who underwent biopsy, 10/10 (100%) who were diagnosed with RN on imaging were confirmed to be RN positive on biopsy and 1/1 (100%) who was not diagnosed with RN was confirmed to be RN negative on biopsy. Age (mean 53.3 vs 50.4 years, respectively), radiotherapy parameters (including total dose, fractionation, CTV and size target volume, all p>0.05), and receipt of any type of systemic therapy during SRS (60.7% vs 55.6%, p=0.97) did not differ between patients who did or did not develop RN. However, there was a trend for patients who developed RN to have received more than one agent of HER2-directed therapy independent of SRS timing compared to those who did not develop RN (75.0% vs 44.4%, p=0.08). Moreover, a significantly higher proportion of those who developed RN received more than one agent of HER2-directed therapy during SRS treatment compared to those who did not develop RN (35.7% vs 5.6%, p=0.047).

Conclusions

Patients with HER2 BCBrM who receive multiple HER2-directed therapies during SRS for BCBrM may be at higher risk of RN. Collectively, these data suggest that, in the eight-week window around SRS administration, if HER2-directed therapy is medically necessary, it is preferable that patients receive a single agent.

Systemic management of brain metastases in HER2+ breast cancer in 2022

Up to half of all patients with metastatic human epidermal growth factor receptor 2-positive (HER2+) breast cancer will eventually acquire brain metastases (BrMs), which are associated with reduced overall survival and decreased quality of life. Although the median overall survival was previously less than a year, novel systemic treatments have significantly extended life expectancy in patients with HER2+ breast cancer BrMs. The current first-line standard of care for all patients with HER2+ metastatic breast cancer, regardless of BrMs status, is dual HER2 antibody therapy with pertuzumab/trastuzumab plus a taxane. Second-line systemic therapy has recently evolved, with the option of trastuzumab deruxtecan (T-DXd) or tucatinib in combination with trastuzumab and capecitabine. T-DXd has shown dramatically superior progression-free survival in comparison with trastuzumab emtansine (T-DM1) in patients with stable BrMs in the second-line setting. Patients who have untreated or locally treated/progressive BrMs may benefit from a regimen with robust intracranial response rates, such as tucatinib in combination with trastuzumab and capecitabine. Third-line therapy and beyond includes multiple options that require careful selection, with the patient's BrMs status, comorbidities, and performance status taken into account. In this review, we focus on current management and evolving strategies for the treatment of patients with HER2+ breast cancer BrMs.

Evaluating the efficacy of a priming dose of cyclophosphamide prior to pembrolizumab to treat metastatic triple negative breast cancer

PURPOSE

Triple negative breast cancer (TNBC) is characterized by the presence of immune cells in the tumor microenvironment, however, the response to single-agent immune checkpoint inhibitor (ICI) therapy is modest. Preclinical models have demonstrated that intratumoral regulatory T cells (T_regs) dampen the antitumor response to ICI. We performed a single-arm phase II trial to evaluate the efficacy of a single low dose of cyclophosphamide (Cy) to deplete T_regs administered before initiating pembrolizumab.

PATIENTS AND METHODS

40 patients with pretreated metastatic TNBC were enrolled. The primary endpoints were progression-free survival (PFS) and change in peripheral blood T_regs after Cy. Secondary endpoints included overall response rate (ORR), duration of response, overall survival, treatment-related adverse events (AEs), and correlative evaluations.

RESULTS

Median PFS was 1.8 months, and the ORR was 21%. T_regs were not significantly decreased after Cy prior to ICI (-3.3%, p=0.19), and increased significantly after the first cycle of therapy (+21% between cycles 1 and 2, p=0.005). Immune-related AEs were similar to historical pembrolizumab monotherapy, and were associated with response to therapy (p=0.02). Patients with pretreatment tumors harboring increased expression of B cell metagene signatures and increased circulating B cell receptor repertoire diversity were associated with clinical response and immune-related toxicity (IRT).

CONCLUSIONS

Among patients with heavily pretreated TNBC, Cy prior to pembrolizumab did not significantly deplete T_regs, and in those with decreased numbers there was rapid recovery following therapy. Increased B cell gene expression in baseline samples was associated with clinical response and IRT.

A Need for More Molecular Profiling in Brain Metastases

As local disease control improves, the public health impact of brain metastases (BrM) continues to grow. Molecular features are frequently different between primary and metastatic tumors as a result of clonal evolution during neoplasm migration, selective pressures imposed by systemic treatments, and differences in the local microenvironment. However, biomarker information in BrM is not routinely obtained despite emerging evidence of its clinical value. We review evidence of discordance in clinically actionable biomarkers between primary tumors, extracranial metastases, and BrM. Although BrM biopsy/resection imposes clinical risks, these risks must be weighed against the potential benefits of assessing biomarkers in BrM. First, new treatment targets unique to a patient's BrM may be identified. Second, as BrM may occur late in a patient's disease course, resistance to initial targeted therapies and/or loss of previously identified biomarkers can occur by the time of occult BrM, rendering initial and other targeted therapies ineffective. Thus, current biomarker data can inform real-time treatment options. Third, biomarker information in BrM may provide useful prognostic information for patients. Appreciating the importance of biomarker analyses in BrM tissue, including how it may identify specific drivers of BrM, is critical for the development of more effective treatment strategies to improve outcomes for this growing patient population.

Advances in the management of breast cancer brain metastases

The development of breast cancer (BC) brain metastases (BrM) is a common complication of advanced disease, occurring in up to half of the patients with advanced disease depending on the subtype. The management of BCBrM requires complex multidisciplinary care including local therapy, surgical resection and/or radiotherapy, palliative care, and carefully selected systemic therapies. Significant progress has been made in the human epidermal growth factor receptor 2-positive (HER2+) BCBrM population due to novel brain penetrable systemic therapies. Increased inclusion of patients with BCBrM in clinical trials using brain-penetrant systemic therapies recently led to the first FDA approval of a HER2-directed therapy specifically in the BCBrM population in the last year. Advances for the treatment of HR+/HER2- and TNBC BCBrM subgroups continue to evolve. In this review, we will discuss the diagnosis and multidisciplinary care of BCBrM. We focus on recent advances in neurosurgery, radiation therapy, and systemic treatment therapies with intracranial activity. We also provide an overview of the current clinical trial landscape for patients with BCBrM.

OTHR-10. Diverse survival outcomes of HER2+ Breast Cancer Brain Metastases (BrCBM) presenting with isolated brain relapse compared to those with concurrent extracranial disease

Background

In patients with isolated HER2+ BrCBM and no extracranial disease (ECD), there are no consensus guidelines on optimal treatment approaches following CNS-directed therapy. Our goal was to determine the implications of ECD at time of first HER2+ BrCBM on intracranial progression-free survival (PFS1) and overall survival (OS).

Methods

Retrospective analysis was performed on 77 patients with HER2+ BrCBM who received 1^st CNS radiation from 2006–2020. Demographics, dates of metastatic and intracranial diagnosis, ECD status at 1st BrCBM, and outcomes were collected. The primary endpoint was PFS1 defined as time from first CNS radiation to the subsequent documentation of intracranial progression (RANO-BM). OS was defined as time from 1^st CNS radiation and 1^st metastatic disease to date of death/last known alive. ECD status was defined by RECIST1.1 from staging scans within 30 days of 1^st BrCBM.

Results

In this patient cohort, 25% (19/77) had isolated brain relapse/no ECD. Median age was 50 years. Most patients (58%) developed first BrCBM during adjuvant or early-line metastatic therapy. All patients with no ECD presented with isolated brain relapse as first metastatic presentation. Patients with concurrent ECD presented with first BrCBM at a median of 16.6m (95% CI: 10.5 to 25.3) after initial metastatic presentation. Median OS from initial metastatic presentation to death was worse for patients with isolated brain relapse (25.3m, 95% CI: 16.8 to 35.3) compared to those with concurrent ECD (49.7m, 95% CI: 43.2 to 62; p=0.01). Median OS from first CNS involvement to death was not statistically different amongst groups.

Conclusions

Patients with isolated HER2+ BrCBM as their initial metastatic event have substantially worse OS compared to patients with concurrent ECD developing CNS metastases later in their disease course. This population with isolated brain relapse deserves investigation of novel treatment algorithms, including earlier introduction of brain-penetrable HER2-targeted agents.

OTHR-14. An immunogenomic analysis of melanoma brain metastases (MBM) compared to extracranial metastases (ECM)

Background

MBM have a unique molecular profile compared to ECM.

Methods

We analyzed a previously published dataset from MD Anderson Cancer Center, including RNA-seq on surgically resected, FFPE MBM and ECM from the same patients. STAR pipeline was used to estimate mRNA abundance. DESeq2 package was used to perform differential gene expression (DGE) analyses. Pathway analysis was performed using Gene Set Enrichment Analysis (GSEA). Paired DGE and GSEA compared MBM vs. lymph node (LN) metastases (n = 16) and MBM vs. skin mets (n = 10). CIBERSORTx estimated relative abundance of immune cell types in MBM and ECM. GATK Mutect2 pipeline was used to call somatic mutations using paired normal tumor samples. Mutations were annotated using the Ensembl Variant Effect Predictor and visualized using the Maftools package in R.

RNA-seq was available on 54 human primary cutaneous melanomas (CM). Gene Ontology or KEGG Pathway analysis was performed using goana function of limma package in R.

Results

Paired GSEA found that autophagy pathways may be up-regulated in MBM vs. LN and MBM vs. skin mets. On a single-gene level, the most strongly up-regulated genes in autophagy pathways were GFAP and HBB. Fold changes in other autophagy-related genes were low and did not reach significance. Comparison between CM which recurred in brain vs. CM which did not recur identified up-regulation of autophagy pathways. CIBERSORTx identified an increased proportion of immune suppressive M2 macrophages compared to tumor suppressive M1 macrophages in MBMs and ECMs.

Conclusion

Up-regulation of autophagy pathways was observed in patient-matched MBM vs. LN and skin mets. This finding was driven by up-regulation of GFAP and HBB, which could reflect changes in the tumor microenvironment. Higher M2:M1 ratio may contribute to an immune suppressive tumor microenvironment and may be targetable. Validation of our findings in an independent Duke dataset is ongoing.

Preparation of an Orthotopic, Syngeneic Model of Lung Adenocarcinoma and the Testing of the Antitumor Efficacy of Poly(2-oxazoline) Formulation of Chemo-and Immunotherapeutic Agents

Tumor xenograft models developed by transplanting human tissues or cells into immune-deficient mice are widely used to study human cancer response to drug candidates. However, immune-deficient mice are unfit for investigating the effect of immunotherapeutic agents on the host immune response to cancer (Morgan, 2012). Here, we describe the preparation of an orthotopic, syngeneic model of lung adenocarcinoma (LUAD), a subtype of non-small cell lung cancer (NSCLC), to study the antitumor effect of chemo and immunotherapeutic agents in an immune-competent animal. The tumor model is developed by implanting 344SQ LUAD cells derived from the metastases of KrasG12D; p53R172HΔG genetically engineered mouse model into the left lung of a syngeneic host (Sv/129). The 344SQ LUAD model offers several advantages over other models: 1) The immune-competent host allows for the assessment of the biologic effects of immune-modulating agents; 2) The pathophysiological features of the human disease are preserved due to the orthotopic approach; 3) Predisposition of the tumor to metastasize facilitates the study of therapeutic effects on primary tumor as well as the metastases ( Chen et al., 2014 ). Furthermore, we also describe a treatment strategy based on Poly(2-oxazoline) micelles that has been shown to be effective in this difficult-to-treat tumor model ( Vinod et al., 2020b ).

Preparation and Characterization of Poly(2-oxazoline) Micelles for the Solubilization and Delivery of Water Insoluble Drugs

Many new drug development candidates are highly lipophilic compounds with low water solubility. This constitutes a formidable challenge for the use of such compounds for cancer therapy, where high doses and intravenous injections are needed ( Di et al., 2012 ). Here, we present a poly(2-oxazoline) polymer (POx)-based nanoformulation strategy to solubilize and deliver hydrophobic drugs. POx micelles are prepared by a simple thin-film hydration method. In this method, the drug and polymer are dissolved in a common solvent and allowed to mix, following which the solvent is evaporated using mild heating conditions to form a thin film. The micelles form spontaneously upon hydration with saline. POx nanoformulation of hydrophobic drugs is unique in that it has a high drug loading capacity, which is superior to micelles of conventional surfactants. Moreover, multiple active pharmaceutical ingredients (APIs) can be included within the same POx micelle, thereby enabling the codelivery of binary as well as ternary drug combinations ( Han et al., 2012 ; He et al., 2016 ).

Silencing of Oncogenic KRAS by Mutant-Selective Small Interfering RNA

Oncogenic mutations in the KRAS gene are well-established drivers of cancer. While the recently developed KRAS^G12C inhibitors offer a targeted KRAS therapy and have shown success in the clinic, KRAS^G12C represents only 11% of all KRAS mutations. Current therapeutic approaches for all other KRAS mutations are both indirect and nonmutant-selective, largely focusing on inhibition of downstream KRAS effectors such as MAP kinases. Inhibition of KRAS downstream signaling results in a system-wide down-modulation of the respective targets, raising concerns about systemic cell toxicity. Here, we describe a custom short interfering RNA oligonucleotide (EFTX-D1) designed to preferentially bind mRNA of the most commonly occurring KRAS missense mutations in codons 12 and 13. We determined that EFTX-D1 preferentially reduced the mutant KRAS sequence versus wild-type at the levels of both transcription and translation and reversed oncogenic KRAS-induced morphologic and growth transformation. Furthermore, EFTX-D1 significantly impaired the proliferation of several KRAS mutant cancer cell lines in 2-D as well as 3-D assays. Taken together, our data indicate a novel use of RNA interference to target oncogenic KRAS-driven cancers specifically.

A Circle RNA Regulatory Axis Promotes Lung Squamous Metastasis via CDR1-Mediated Regulation of Golgi Trafficking

Lung squamous carcinoma (LUSC) is a highly metastatic disease with a poor prognosis. Using an integrated screening approach, we found that miR-671-5p reduces LUSC metastasis by inhibiting a circular RNA (circRNA), CDR1as. Although the putative function of circRNA is through miRNA sponging, we found that miR-671-5p more potently silenced an axis of CDR1as and its antisense transcript, cerebellar degeneration related protein 1 (CDR1). Silencing of CDR1as or CDR1 significantly inhibited LUSC metastases and CDR1 was sufficient to promote migration and metastases. CDR1, which directly interacted with adaptor protein 1 (AP1) complex subunits and coatomer protein I (COPI) proteins, no longer promoted migration upon blockade of Golgi trafficking. Therapeutic inhibition of the CDR1as/CDR1 axis with miR-671-5p mimics reduced metastasis in vivo. This report demonstrates a novel role for CDR1 in promoting metastasis and Golgi trafficking. These findings reveal an miRNA/circRNA axis that regulates LUSC metastases through a previously unstudied protein, CDR1. SIGNIFICANCE: This study shows that circRNA, CDR1as, promotes lung squamous migration, metastasis, and Golgi trafficking through its complimentary transcript, CDR1.

Brain Metastasis Cell Lines Panel: A Public Resource of Organotropic Cell Lines

Spread of cancer to the brain remains an unmet clinical need in spite of the increasing number of cases among patients with lung, breast cancer, and melanoma most notably. Although research on brain metastasis was considered a minor aspect in the past due to its untreatable nature and invariable lethality, nowadays, limited but encouraging examples have questioned this statement, making it more attractive for basic and clinical researchers. Evidences of its own biological identity (i.e., specific microenvironment) and particular therapeutic requirements (i.e., presence of blood-brain barrier, blood-tumor barrier, molecular differences with the primary tumor) are thought to be critical aspects that must be functionally exploited using preclinical models. We present the coordinated effort of 19 laboratories to compile comprehensive information related to brain metastasis experimental models. Each laboratory has provided details on the cancer cell lines they have generated or characterized as being capable of forming metastatic colonies in the brain, as well as principle methodologies of brain metastasis research. The Brain Metastasis Cell Lines Panel (BrMPanel) represents the first of its class and includes information about the cell line, how tropism to the brain was established, and the behavior of each model in vivo. These and other aspects described are intended to assist investigators in choosing the most suitable cell line for research on brain metastasis. The main goal of this effort is to facilitate research on this unmet clinical need, to improve models through a collaborative environment, and to promote the exchange of information on these valuable resources.

HER2‐positive breast cancer brain metastasis: A new and exciting landscape

Background

Brain metastases (BrM) incidence is 25% to 50% in women with advanced human epidermal growth factor receptor 2 (HER2)‐positive breast cancer. Radiation and surgery are currently the main local treatment approaches for central nervous system (CNS) metastases. Systemic anti‐HER2 therapy following a diagnosis of BrM improves outcomes. Previous preclinical data has helped elucidate HER2 brain trophism, the blood‐brain/blood‐tumor barrier(s), and the brain tumor microenvironment, all of which can lead to development of novel therapeutic options.

Recent findings

Several anti‐HER2 agents are currently available and reviewed here, some of which have recently shown promising effects in BrM patients, specifically. New strategies driven by and focusing on brain metastasis‐specific genomics, immunotherapy, and preventive strategies have shown promising results and are under development.

Conclusions

The field of HER2+ breast cancer, particularly for BrM, continues to evolve as new therapeutic strategies show promising results in recent clinical trials. Increasing inclusion of patients with BrM in clinical studies, and a focus on assessing their outcomes both intracranially and extracranially, is changing the landscape for patients with HER2+ CNS metastases by demonstrating the ability of newer agents to improve outcomes.

Efficacy and pharmacodynamics of niraparib in BRCA-mutant and wild-type intracranial triple-negative breast cancer murine models

Background

Despite the poor prognosis of triple-negative breast cancer (TNBC) brain metastases, there are no approved systemic therapies. We explored the DNA-damaging poly(ADP-ribose) polymerase inhibitor (PARPi) niraparib in intracranial mouse models of breast cancer susceptibility protein (BRCA)-mutant TNBC.

Methods

Mice bearing intracranial human-derived TNBC cell lines (SUM149, MDA-MB-231Br, or MDA-MB-436) were treated with niraparib and monitored for survival; intracranial tissues were analyzed for PAR levels and niraparib concentration by mass spectrometry. RNASeq data of primary breast cancers using The Cancer Genome Atlas were analyzed for DNA damage signatures. Combined RAD51 and PARP inhibition in TNBC cell lines was assessed in vitro by colony-forming assays.

Results

Daily niraparib increased median survival and decreased tumor burden in the BRCA-mutant MDA-MB-436 model, but not in the BRCA-mutant SUM149 or BRCA-wild-type MDA-MB-231Br models despite high concentrations in intracranial tumors. RAD51 inhibitor B02 was shown to sensitize all cell lines to PARP inhibition (PARPi). In the analysis of BRCA-mutant primary human TNBCs, gene expression predictors of PARPi sensitivity and DNA repair signatures demonstrate widespread heterogeneity, which may explain the differential response to PARPi. Interestingly, these signatures are significantly correlated to RAD51 expression including PARPi sensitivity (R² = 0.602, R²= 0.758).

Conclusions

Niraparib penetrates intracranial tumor tissues in mouse models of TNBC with impressive single-agent efficacy in BRCA-mutant MDA-MB-436. Clinical evaluation of niraparib to treat TNBC brain metastases, an unmet clinical need desperate for improved therapies, is warranted. Further compromising DNA repair through RAD51 inhibition may further augment TNBC’s response to PARPi.

High-capacity poly(2-oxazoline) formulation of TLR 7/8 agonist extends survival in a chemo-insensitive, metastatic model of lung adenocarcinoma

About 40% of patients with non-small cell lung cancer (NSCLC) have stage IV cancer at the time of diagnosis. The only viable treatment options for metastatic disease are systemic chemotherapy and immunotherapy. Nonetheless, chemoresistance remains a major cause of chemotherapy failure. New immunotherapeutic modalities such as anti-PD-1 immune checkpoint blockade have shown promise; however, response to such strategies is highly variable across patients. Here, we show that our unique poly(2-oxazoline)-based nanomicellar formulation (PM) of Resiquimod, an imidazoquinoline Toll-like receptor (TLR) 7/8 agonist, had a superior tumor inhibitory effect in a metastatic model of lung adenocarcinoma, relative to anti-PD-1 therapy or platinum-based chemotherapy. Investigation of the in vivo immune status following Resiquimod PM treatment showed that Resiquimod-based stimulation of antigen-presenting cells in the tumor microenvironment resulted in the mobilization of an antitumor CD8+ immune response. Our study demonstrates the promise of poly(2-oxazoline)-formulated Resiquimod for treating metastatic NSCLC.

Histone deacetylase 11 inhibition promotes breast cancer metastasis from lymph nodes

Lymph node (LN) metastases correspond with a worse prognosis in nearly all cancers, yet the occurrence of cancer spreading from LNs remains controversial. Additionally, the mechanisms explaining how cancers survive and exit LNs are largely unknown. Here, we show that breast cancer patients frequently have LN metastases that closely resemble distant metastases. In addition, using a microsurgical model, we show how LN metastasis development and dissemination is regulated by the expression of a chromatin modifier, histone deacetylase 11 (HDAC11). Genetic and pharmacologic blockade of HDAC11 decreases LN tumor growth, yet substantially increases migration and distant metastasis formation. Collectively, we reveal a mechanism explaining how HDAC11 plasticity promotes breast cancer growth as well as dissemination from LNs and suggest caution with the use of HDAC inhibitors.

The prognosis of cancer patients with lymph node (LN) metastasis is worse than those without. Here, the authors report that while histone deacetylase 11 (HDAC11) inhibition suppresses tumor growth within the LN, it also promotes cancer cell migration out of the LN to form distant metastasis, and therefore suggest caution with HDAC inhibitors.

Combined kinase inhibitors of MEK1/2 and either PI3K or PDGFR are efficacious in intracranial triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC), lacking expression of hormone and human epidermal growth factor receptor 2 receptors, is an aggressive subtype that frequently metastasizes to the brain and has no FDA-approved systemic therapies. Previous literature demonstrates mitogen-activated protein kinase kinase (MEK) pathway activation in TNBC brain metastases. Thus, we aimed to discover rational combinatorial therapies with MEK inhibition, hypothesizing that co-inhibition using clinically available brain-penetrant inhibitors would improve survival in preclinical models of TNBC brain metastases.

Methods

Using human-derived TNBC cell lines, synthetic lethal small interfering RNA kinase screens were evaluated with brain-penetrant inhibitors against MEK1/2 (selumetinib, AZD6244) or phosphatidylinositol-3 kinase (PI3K; buparlisib, BKM120). Mice bearing intracranial TNBC tumors (SUM149, MDA-MB-231Br, MDA-MB-468, or MDA-MB-436) were treated with MEK, PI3K, or platelet derived growth factor receptor (PDGFR; pazopanib) inhibitors alone or in combination. Tumors were analyzed by western blot and multiplexed kinase inhibitor beads/mass spectrometry to assess treatment effects.

Results

Screens identified MEK+PI3K and MEK+PDGFR inhibitors as tractable, rational combinations. Dual treatment of selumetinib with buparlisib or pazopanib was synergistic in TNBC cells in vitro. Both combinations improved survival in intracranial SUM149 and MDA-MB-231Br, but not MDA-MB-468 or MDA-MB-436. Treatments decreased mitogen-activated protein kinase (MAPK) and PI3K (Akt) signaling in sensitive (SUM149 and 231Br) but not resistant models (MDA-MB-468). Exploratory analysis of kinome reprogramming in SUM149 intracranial tumors after MEK ± PI3K inhibition demonstrates extensive kinome changes with treatment, especially in MAPK pathway members.

Conclusions

Results demonstrate that rational combinations of the clinically available inhibitors selumetinib with buparlisib or pazopanib may prove to be promising therapeutic strategies for the treatment of some TNBC brain metastases. Additionally, effective combination treatments cause widespread alterations in kinase pathways, including targetable potential resistance drivers.

Combination therapy with potent PI3K and MAPK inhibitors overcomes adaptive kinome resistance to single agents in preclinical models of glioblastoma

Background

Glioblastoma (GBM) is the most common and aggressive primary brain tumor. Prognosis remains poor despite multimodal therapy. Developing alternative treatments is essential. Drugs targeting kinases within the phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) effectors of receptor tyrosine kinase (RTK) signaling represent promising candidates.

Methods

We previously developed a non-germline genetically engineered mouse model of GBM in which PI3K and MAPK are activated via Pten deletion and KrasG12D in immortalized astrocytes. Using this model, we examined the influence of drug potency on target inhibition, alternate pathway activation, efficacy, and synergism of single agent and combination therapy with inhibitors of these 2 pathways. Efficacy was then examined in GBM patient-derived xenografts (PDX) in vitro and in vivo.

Results

PI3K and mitogen-activated protein kinase kinase (MEK) inhibitor potency was directly associated with target inhibition, alternate RTK effector activation, and efficacy in mutant murine astrocytes in vitro. The kinomes of GBM PDX and tumor samples were heterogeneous, with a subset of the latter harboring MAPK hyperactivation. Dual PI3K/MEK inhibitor treatment overcame alternate effector activation, was synergistic in vitro, and was more effective than single agent therapy in subcutaneous murine allografts. However, efficacy in orthotopic allografts was minimal. This was likely due to dose-limiting toxicity and incomplete target inhibition.

Conclusion

Drug potency influences PI3K/MEK inhibitor-induced target inhibition, adaptive kinome reprogramming, efficacy, and synergy. Our findings suggest that combination therapies with highly potent, brain-penetrant kinase inhibitors will be required to improve patient outcomes.

Experimentally Dissecting the Origins of Peroxiredoxin Catalysis

AIMS

Peroxiredoxins (Prxs) are ubiquitous cysteine-based peroxidases involved in oxidant defense and signal transduction. Despite much study, the precise roles of conserved residues remain poorly defined. In this study, we carried out extensive functional and structural characterization of 10 variants of such residues in a model decameric bacterial Prx.

RESULTS

Three active site proximal mutations of Salmonella typhimurium AhpC, T43V, R119A, and E49Q, lowered catalytic efficiency with hydrogen peroxide by 4-5 orders of magnitude, but did not affect reactivity toward their reductant, AhpF. pK_a values of the peroxidatic cysteine were also shifted up by 1-1.3 pH units for these and a decamer disruption mutant, T77I. Except for the decamer-stabilizing T77V, all mutations destabilized decamers in the reduced form. In the oxidized form, three mutants-T77V, T43A, and T43S-exhibited stabilized decamers and were more efficiently reduced by AhpF than wild-type AhpC. Crystal structures of most mutants were solved and many showed alterations in stability of the fully folded active site loop.

INNOVATION

This is the first study of Prx mutants to comprehensively assess the effects of mutations on catalytic activities, the active site cysteine pK_a, and the protein structure and oligomeric status.

CONCLUSION

The Arg119 side chain must be properly situated for efficient catalysis, but for other debilitating variants, the functional defects could be explained by structural perturbations and/or associated decamer destabilization rather than direct effects. This underscores the importance of our comprehensive approach. A remarkable new finding was the preference of the reductant for decamers. Antioxid. Redox Signal. 28, 521-536.

Multidisciplinary Management of Breast Cancer Brain Metastases

This review summarizes the most up-to-date approach to the multidisciplinary management of patients with breast cancer brain metastases. A brief overview of the epidemiology and biology of breast cancer brain metastasis is provided. The perspectives of radiation oncology, neurosurgery, and medical oncology-and landmark studies from each discipline-are all discussed. We also offer practical tips to help guide the treating physician, including data on antiseizure medications. Finally, we introduce the concept of a multidisciplinary clinic that combines input from medical and radiation oncology, neurosurgery, and support services, which we developed at the University of North Carolina as a coordinated and optimal approach to the management of patients with this complex disease.

Efficacy of Carboplatin Alone and in Combination with ABT888 in Intracranial Murine Models of BRCA-Mutated and BRCA-Wild-Type Triple-Negative Breast Cancer

Patients with breast cancer brain metastases have extremely limited survival and no approved systemic therapeutics. Triple-negative breast cancer (TNBC) commonly metastasizes to the brain and predicts poor prognosis. TNBC frequently harbors BRCA mutations translating to platinum sensitivity potentially augmented by additional suppression of DNA repair mechanisms through PARP inhibition. We evaluated brain penetrance and efficacy of carboplatin ± the PARP inhibitor ABT888, and investigated gene-expression changes in murine intracranial TNBC models stratified by BRCA and molecular subtype status. Athymic mice were inoculated intracerebrally with BRCA-mutant: SUM149 (basal), MDA-MB-436 (claudin-low); or BRCA-wild-type (wt): MDA-MB-468 (basal), MDA-MB-231BR (claudin-low). TNBC cells were treated with PBS control [intraperitoneal (IP), weekly], carboplatin (50 mg/kg/wk, IP), ABT888 (25 mg/kg/d, oral gavage), or their combination. DNA damage (γ-H2AX), apoptosis (cleaved caspase-3, cC3), and gene expression were measured in intracranial tumors. Carboplatin ± ABT888 significantly improved survival in BRCA-mutant intracranial models compared with control, but did not improve survival in BRCA-wt intracranial models. Carboplatin + ABT888 revealed a modest survival advantage versus carboplatin in BRCA-mutant models. ABT888 yielded a marginal survival benefit in the MDA-MB-436, but not in the SUM149 model. BRCA-mutant SUM149 expression of γ-H2AX and cC3 proteins was elevated in all treatment groups compared with control, whereas BRCA-wt MDA-MB-468 cC3 expression did not increase with treatment. Carboplatin treatment induced common gene-expression changes in BRCA-mutant models. Carboplatin ± ABT888 penetrates the brain and improves survival in BRCA-mutant intracranial TNBC models with corresponding DNA damage and gene-expression changes. Combination therapy represents a potential promising treatment strategy for patients with TNBC brain metastases warranting further clinical investigation.

Simplified dietary acute tryptophan depletion: effects of a novel amino acid mixture on the neurochemistry of C57BL/6J mice

BACKGROUND

Diet and nutrition can impact on the biological processes underpinning neuropsychiatric disorders. Amino acid (AA) mixtures lacking a specific neurotransmitter precursor can change the levels of brain serotonin (5-HT) or dopamine (DA) in the central nervous system. The availability of these substances within the brain is determined by the blood-brain barrier (BBB) that restricts the access of peripheral AA into the brain. AA mixtures lacking tryptophan (TRP) compete with endogenous TRP for uptake into the brain across the BBB, which in turn leads to a decrease in central nervous 5-HT synthesis.

OBJECTIVE

The present study compared the effects of a simplified acute tryptophan depletion (SATD) mixture in mice on blood and brain serotonergic and dopaminergic metabolites to those of a commonly used acute tryptophan depletion mixture (ATD Moja-De) and its TRP-balanced control (BAL).

DESIGN

The SATD formula is composed of only three large neutral AAs: phenylalanine (PHE), leucine (LEU), and isoleucine (ILE). BAL, ATD Moja-De, or SATD formulas were delivered to adult male C57BL/6J mice by gavage. TRP, monoamines, and their metabolites were quantified in blood and brain regions (hippocampus, frontal cortex, amygdala, caudate putamen, and nucleus accumbens).

RESULTS

Both ATD Moja-De and SATD significantly decreased levels of serum and brain TRP, as well as brain 5-HIAA and 5-HT compared with BAL. SATD reduced HVA levels in caudate but did not alter total DA levels or DOPAC. SATD decreased TRP and serotonergic metabolites comparably to ATD Moja-De administration.

CONCLUSION

A simplified and more palatable combination of AAs can manipulate serotonergic function and might be useful to reveal underlying monoamine-related mechanisms contributing to different neuropsychiatric disorders.

Estradiol replacement enhances cocaine-stimulated locomotion in female C57BL/6 mice through estrogen receptor alpha

Psychostimulant effects are enhanced by ovarian hormones in women and female rodents. Estradiol increases behavioral responses to psychostimulants in women and female rats, although the underlying mechanism is unknown. This study utilized mice to investigate the time frame and receptor mediation of estradiol's enhancement of cocaine-induced behavior as mice enable parallel use of genetic, surgical and pharmacological methods. The spontaneous behavior of Sham and Ovariectomized (Ovx) female wildtype (WT) mice was determined during habituation to a novel environment and after cocaine administration. Ovx mice were replaced with vehicle (sesame oil) or 17β-estradiol (E2) for 2 days or 30 min prior to a cocaine challenge to investigate the time course of E2's effects. To examine receptor mediation of estradiol effects, Ovx mice replaced for 2 days with either the ERα-selective agonist PPT or the ERβ-selective agonist DPN were compared to Sham mice, and mice lacking either ERα (αERKO) or ERβ (βERKO) were compared to WT littermates. Ovx mice exhibited fewer ambulations during habituation than Sham females. Cocaine-induced increases in behavioral ratings were greater in Sham than in Ovx mice. Two days but not 30 min of E2 replacement in Ovx mice increased cocaine responses to Sham levels. PPT replacement also increased the cocaine response relative to vehicle- or DPN- treated Ovx mice. αERKO mice displayed modestly attenuated behavioral responses to novelty and cocaine compared to αWT littermates, but no behavioral differences were found between βERKO and βWT mice. These results suggest that E2 enhances cocaine-stimulated locomotion in mice predominantly through ERα.

Effects of acute tryptophan depletion on brain serotonin function and concentrations of dopamine and norepinephrine in C57BL/6J and BALB/cJ mice

Acute tryptophan depletion (ATD) is a method of lowering brain serotonin (5-HT). Administration of large neutral amino acids (LNAA) limits the transport of endogenous tryptophan (TRP) across the blood brain barrier by competition with other LNAAs and subsequently decreases serotonergic neurotransmission. A recent discussion on the specificity and efficacy of the ATD paradigm for inhibition of central nervous 5-HT has arisen. Moreover, side effects such as vomiting and nausea after intake of amino acids (AA) still limit its use. ATD Moja-De is a revised mixture of AAs which is less nauseating than conventional protocols. It has been used in preliminary clinical studies but its effects on central 5-HT mechanisms and other neurotransmitter systems have not been validated in an animal model. We tested ATD Moja-De (TRP−) in two strains of mice: C57BL/6J, and BALB/cJ, which are reported to have impaired 5-HT synthesis and a more anxious phenotype relative to other strains of mice. ATD Moja-De lowered brain TRP, significantly decreased 5-HT synthesis as indexed by 5-HTP levels after decarboxlyase inhibition, and lowered 5-HT and 5-HIAA in both strains of mice, however more so in C57BL/6J than in BALB/cJ. Dopamine and its metabolites as well as norepinephrine were not affected. A balanced (TRP+) control mixture did not raise 5-HT or 5-HIAA. The present findings suggest that ATD Moja-De effectively and specifically suppresses central serotonergic function. These results also demonstrate a strain- specific effect of ATD Moja-De on anxiety-like behavior.

Individual differences in psychostimulant responses of female rats are associated with ovarian hormones and dopamine neuroanatomy

Ovarian hormones modulate the pharmacological effects of psychostimulants and may enhance vulnerability to drug addiction. Female rats have more midbrain dopamine neurons than males and greater dopamine uptake and release rates. Cocaine stimulates motor behavior and dopamine efflux more in female than male rats, but the mediating mechanisms are unknown. This study investigated individual differences in anatomic, neurochemical, and behavioral measures in female rats to understand how ovarian hormones affect the relatedness of these endpoints. Ovarian hormone effects were assessed by comparing individual responses in ovariectomized (OVX) and sham adult female rats. Locomotion was determined before and following 10mg/kg cocaine. Electrically-stimulated dopamine efflux was assessed using fast cyclic voltammetry in vivo. Dopamine neuron number and density in substantia nigra (SN) and ventral tegmental area (VTA) were determined in the same animals using tyrosine-hydroxylase immunohistochemistry and unbiased stereology. Locomotor behavior and dopamine efflux did not differ at baseline but were greater in sham than OVX following cocaine. Cocaine increased dopamine release rates in both groups but uptake inhibition (K(m)) was greater in sham than OVX. Dopamine neuron number and density in SN and VTA were greater in shams. Sham females with the largest uterine weights exhibited the highest density of dopamine neurons in the SN, and the most cocaine-stimulated behavior and dopamine efflux. Ovariectomy eliminated these relationships. We postulate that SN density could link ovarian hormones and high-psychostimulant responses in females. Similar mechanisms may be involved in individual differences in the addiction vulnerability of women.