Quantitative protein expression of blood-brain barrier transporters in the vasculature of brain metastases of patients with lung and breast cancer

The impact of ATP-binding cassette transporters in the diseased brain: Context matters

ATP-binding cassette (ABC) transporters facilitate the movement of diverse molecules across cellular membranes, including those within the CNS. While most extensively studied in microvascular endothelial cells forming the blood-brain barrier (BBB), other CNS cell types also express these transporters. Importantly, disruptions in the CNS microenvironment during disease can alter transporter expression and function. Through this comprehensive review, we explore the modulation of ABC transporters in various brain pathologies and the context-dependent consequences of these changes. For instance, downregulation of ABCB1 may exacerbate amyloid beta plaque deposition in Alzheimer's disease and facilitate neurotoxic compound entry in Parkinson's disease. Upregulation may worsen neuroinflammation by aiding chemokine-mediated CD8 T cell influx into multiple sclerosis lesions. Overall, ABC transporters at the BBB hinder drug entry, presenting challenges for effective pharmacotherapy. Understanding the context-dependent changes in ABC transporter expression and function is crucial for elucidating the etiology and developing treatments for brain diseases.

Proteomics-based Model for Predicting the Risk of Brain Metastasis in Patients with Resected Lung Adenocarcinoma carrying the EGFR Mutation

Introduction: Epidermal growth factor receptor (EGFR) mutation is common in Chinese patients with lung adenocarcinoma (LUAD). Brain metastases (BMs) is high and associated with poor prognosis. Identification of EGFR-mutant patients at high risk of developing BMs is important to reduce or delay the incidence of BMs. Currently, there is no literature on the prediction and modeling of EGFR brain metastasis at the proteinomics level. Methods: We conducted a retrospective study of BMs in postoperative recurrent LUAD with EGFR mutation in the First Affiliated Hospital of Guangzhou Medical University. Tissue proteomic analysis was applied in the primary tumors of resected LUAD in this study using liquid chromatography-mass spectrometry (LC-MS/MS). To identify potential markers for predicting LUAD BM, comparative analyses were performed on different groups to evaluate proteins associated with high risk of BMs. Results: A combination of three potential marker proteins was found to discriminate well between distal metastasis (DM) and local recurrence (LR) of postoperative LUAD with EGFR mutation. Gene Ontology (GO) analysis of significantly altered proteins between BM and non-BM (NBM) indicated that lipid metabolism and cell cycle-related pathways were involved in BMs of LUAD. And the enriched pathways correlated with BMs were found to be quite different in the comparison groups of postoperative adjuvant therapy, tyrosine kinase inhibitor (TKI), and chemotherapy groups. Finally, we developed a random forest algorithm model with eight proteins (RRS1, CPT1A, DNM1, SRCAP, MLYCD, PCID2, IMPAD1 and FILIP1), which showed excellent predictive value (AUC: 0.9401) of BM in patients with LUAD harboring EGFR mutation. Conclusions: A predictive model based on protein markers was developed to accurately predict postoperative BM in operable LUAD harboring EGFR mutation.

Immunotherapy and brain metastasis in lung cancer: connecting bench side science to the clinic

Brain metastases (BMs) are the most common form of intracranial malignant neoplasms in adults, with a profound impact on quality of life and traditionally associated with a dismal prognosis. Lung cancer accounts for approximately 40%-50% of BM across different tumors. The process leading to BMs is complex and includes local invasion, intravasation, tumor cells circulation into the bloodstream, disruption of the blood-brain barrier, extravasation of tumor cells into the brain parenchyma, and interaction with cells of the brain microenvironment, among others. Once the tumor cells have seeded in the brain parenchyma, they encounter different glial cells of the brain, as well as immune cells. The interaction between these cells and tumor cells is complex and is associated with both antitumoral and protumoral effects. To overcome the lethal prognosis associated with BMs, different treatment strategies have been developed, such as immunotherapy with immune checkpoint inhibitors, particularly inhibitors of the PD-1/PD-L1 axis, which have demonstrated to be an effective treatment in both non-small cell lung cancer and small cell lung cancer. These antibodies have shown to be effective in the treatment of BM, alone or in combination with chemotherapy or radiotherapy. However, many unsolved questions remain to be answered, such as the sequencing of immunotherapy and radiotherapy, the optimal management in symptomatic BMs, the role of the addition of anti-CTLA-4 antibodies, and so forth. The complexity in the management of BMs in the era of immunotherapy requires a multidisciplinary approach to adequately treat this devastating event. The aim of this review is to summarize evidence regarding epidemiology of BM, its pathophysiology, current approach to treatment strategies, as well as future perspectives.

Betulinic acid in the treatment of breast cancer: Application and mechanism progress

Betulinic acid (BA) is a pentacyclic triterpene compound, which can be obtained by separation, chemical synthesis and biotransformation. BA has excellent biological activities, especially its role in the treatment of breast cancer deserves attention. Its mechanisms mainly include inducing mitochondrial oxidative stress, regulating specific protein (Sp) transcription factors, inhibiting breast cancer metastasis, inhibiting glucose metabolism and NF-κB pathway. In addition, BA can also increase the sensitivity of breast cancer cells to other chemotherapy drugs such as paclitaxel and reduce its toxic side effects. This article reviews the application and possible mechanism of BA in the treatment of breast cancer.

Recent advances in the in vitro and in vivo methods to assess impact of P-glycoprotein and breast cancer resistance protein transporters in central nervous system drug disposition

One challenge in central nervous system (CNS) drug discovery has been ensuring the blood-brain barrier (BBB) penetration of compounds at an efficacious concentration that provides suitable safety margins for clinical investigation. Research providing for the accurate prediction of brain penetration of compounds during preclinical discovery is important to a CNS program. In the BBB, P-glycoprotein (P-gp) (ABCB1) and breast cancer resistance protein (BCRP) (ABCG2) transporters have been demonstrated to play a major role in the active efflux of endogenous compounds and xenobiotics out of the brain microvessel cells and back to the systemic circulation. In the past 10 years, there has been significant technological improvement in the sensitivity of quantitative proteomics methods, in vivo imaging, in vitro methods of organoid and microphysiological systems, as well as in silico quantitative physiological based pharmacokinetic and systems pharmacology models. Scientists continually leverage these advancements to interrogate the distribution of compounds in the CNS which may also show signals of substrate specificity of P-gp and/or BCRP. These methods have shown promise toward predicting and quantifying the unbound concentration(s) within the brain relevant for efficacy or safety. In this review, the authors have summarized the in vivo, in vitro, and proteomics advancements toward understanding the contribution of P-gp and/or BCRP in restricting the entry of compounds to the CNS of either healthy or special populations. Special emphasis has been provided on recent investigations on the application of a proteomics-informed approach to predict steady-state drug concentrations in the brain. Moreover, future perspectives regarding the role of these transporters in newer modalities are discussed.

Mechanistic Modeling of Central Nervous System Pharmacokinetics and Target Engagement of HER2 Tyrosine Kinase Inhibitors to Inform Treatment of Breast Cancer Brain Metastases

PURPOSE

This study evaluated the central nervous system (CNS) pharmacokinetics and target engagement of lapatinib, neratinib, and tucatinib in patients with cancer, using a physiologically based pharmacokinetic (PBPK) modeling approach.

EXPERIMENTAL DESIGN

Drug-specific parameters for in vitro metabolism, binding to plasma proteins and brain tissues, transcellular passive permeability, and interactions with efflux transporters were determined. Whole-body PBPK models integrated with a 4-compartment permeability-limited brain model was developed and verified for predicting plasma and CNS pharmacokinetics. Target engagement ratio (TER), defined as the ratio of the average steady-state unbound drug brain concentration (Css,ave,br) to in vitro IC50 for HER2 inhibition, was used as a predictor of intracranial efficacy.

RESULTS

PBPK models predicted that following 1 cycle of standard dosing, tucatinib and lapatinib achieved similar Css,ave,br (14.5 vs. 16.8 nmol/L), while neratinib Css,ave,br (0.68 nmol/L) was 20-fold lower. Tucatinib and neratinib were equally potent for HER2 inhibition (IC50, 6.9 vs. 5.6 nmol/L), while lapatinib was less potent (IC50, 109 nmol/L). The model-predicted population mean TER in the human normal brain was 2.1 for tucatinib, but < 0.20 for lapatinib and neratinib.

CONCLUSIONS

The PBPK modeling suggests that tucatinib induces sufficient HER2 inhibition (TER > 2.0) in not only brain metastases with a disrupted blood-brain barrier (BBB), but also micrometastases where the BBB largely remains intact. These findings, in line with available clinical pharmacokinetics and efficacy data, support the therapeutic value of tucatinib for treatment of brain metastases and warrant further clinical investigation for the prevention of brain metastases in patients with HER2-positive breast cancer.

Glioblastoma, from disease understanding towards optimal cell-based in vitro models

Background

Glioblastoma (GBM) patients are notoriously difficult to treat and ultimately all succumb to disease. This unfortunate scenario motivates research into better characterizing and understanding this disease, and into developing novel research tools by which potential novel therapeutics and treatment options initially can be evaluated pre-clinically. Here, we provide a concise overview of glioblastoma epidemiology, disease classification, the challenges faced in the treatment of glioblastoma and current novel treatment strategies. From this, we lead into a description and assessment of advanced cell-based models that aim to narrow the gap between pre-clinical and clinical studies. Such invitro models are required to deliver reliable and meaningful data for the development and pre-validation of novel therapeutics and treatments.

Conclusions

The toolbox for GBM cell-based models has expanded substantially, with the possibility of 3D printing tumour tissues and thereby replicating invivo tissue architectures now looming on the horizon. A comparison of experimental cell-based model systems and techniques highlights advantages and drawbacks of the various tools available, based on which cell-based models and experimental approaches best suited to address a diversity of research questions in the glioblastoma research field can be selected.

Advances in Hydrogel-Based Microfluidic Blood–Brain-Barrier Models in Oncology Research

The intrinsic architecture and complexity of the brain restricts the capacity of therapeutic molecules to reach their potential targets, thereby limiting therapeutic possibilities concerning neurological ailments and brain malignancy. As conventional models fail to recapitulate the complexity of the brain, progress in the field of microfluidics has facilitated the development of advanced in vitro platforms that could imitate the in vivo microenvironments and pathological features of the blood–brain barrier (BBB). It is highly desirous that developed in vitro BBB-on-chip models serve as a platform to investigate cancer metastasis of the brain along with the possibility of efficiently screening chemotherapeutic agents against brain malignancies. In order to improve the proficiency of BBB-on-chip models, hydrogels have been widely explored due to their unique physical and chemical properties, which mimic the three-dimensional (3D) micro architecture of tissues. Hydrogel-based BBB-on-chip models serves as a stage which is conducive for cell growth and allows the exchange of gases and nutrients and the removal of metabolic wastes between cells and the cell/extra cellular matrix (ECM) interface. Here, we present recent advancements in BBB-on-chip models targeting brain malignancies and examine the utility of hydrogel-based BBB models that could further strengthen the future application of microfluidic devices in oncology research.

The Extension of the LeiCNS-PK3.0 Model in Combination with the "Handshake" Approach to Understand Brain Tumor Pathophysiology

Micrometastatic brain tumor cells, which cause recurrence of malignant brain tumors, are often protected by the intact blood–brain barrier (BBB). Therefore, it is essential to deliver effective drugs across not only the disrupted blood-tumor barrier (BTB) but also the intact BBB to effectively treat malignant brain tumors. Our aim is to predict pharmacokinetic (PK) profiles in brain tumor regions with the disrupted BTB and the intact BBB to support the successful drug development for malignant brain tumors. LeiCNS-PK3.0, a comprehensive central nervous system (CNS) physiologically based pharmacokinetic (PBPK) model, was extended to incorporate brain tumor compartments. Most pathophysiological parameters of brain tumors were obtained from literature and two missing parameters of the BTB, paracellular pore size and expression level of active transporters, were estimated by fitting existing data, like a “handshake”. Simultaneous predictions were made for PK profiles in extracellular fluids (ECF) of brain tumors and normal-appearing brain and validated on existing data for six small molecule anticancer drugs. The LeiCNS-tumor model predicted ECF PK profiles in brain tumor as well as normal-appearing brain in rat brain tumor models and high-grade glioma patients within twofold error for most data points, in combination with estimated paracellular pore size of the BTB and active efflux clearance at the BTB. Our model demonstrated a potential to predict PK profiles of small molecule drugs in brain tumors, for which quantitative information on pathophysiological alterations is available, and contribute to the efficient and successful drug development for malignant brain tumors.

The blood-tumour barrier in cancer biology and therapy

The protective blood-brain barrier has a major role in ensuring normal brain function by severely limiting and tightly controlling the ingress of substances into the brain from the circulation. In primary brain tumours, such as glioblastomas, as well as in brain metastases from cancers in other organs, including lung and breast cancers and melanoma, the blood-brain barrier is modified and is referred to as the blood-tumour barrier (BTB). Alterations in the BTB affect its permeability, and this structure participates in reciprocal regulatory pathways with tumour cells. Importantly, the BTB typically retains a heterogeneous capacity to restrict the penetration of many therapeutic agents into intracranial tumours, and overcoming this challenge is a key to improving the effectiveness of treatment and patient quality of life. Herein, current knowledge of BTB structure and function is reviewed from a cell and cancer biology standpoint, with a focus on findings derived from in vivo models and human tumour specimens. Additionally, how this knowledge can be translated into clinical advances for patients with cancer is discussed.