Single-cell pharmacokinetic imaging reveals a therapeutic strategy to overcome drug resistance to the microtubule inhibitor eribulin

Therapeutic co-assemblies for synergistic NSCLC treatment through dual topoisomerase I and tubulin inhibitors

Camptothecin (CPT) and podophyllotoxin (PPT) function as topoisomerase (TOP) I and tubulin inhibitors, respectively, with potent anticancer effects in a variety of cancers. Despite its promise, the clinical applicability of the combination of CPT and PPT faces challenges, including potential side effect and limited therapeutic efficacy. In this study, we designed co-assembly nanomedicines with the different weight (w/w) ratios of amphiphilic Evans blue conjugated CPT prodrug (EB-ss-CPT) and PPT molecules, denoted as ECT Nano. The co-assembly of EB-ss-CPT and PPT without other excipients has nearly 100% drug loading efficiency and high drug loading content of PPT of up to 74.29 ± 0.90 wt%. Notably, the ECT Nano (1:2) equipped with the ability to inhibit TOP I activity and tubulin polymerization, which provided a highly efficient strategy to improve synergistic efficacy and decrease side toxicity in non-small cell lung cancer mouse model. This work represents a step forward to the development of practical applications for dual TOP I and tubulin inhibitors and especially hopeful to the rational design of combination nanomedicine for therapeutic purposes.

Targeted SPP1 Inhibition of Tumor-Associated Myeloid Cells Effectively Decreases Tumor Sizes

Secreted phosphosprotein 1 (SPP1)High tumor-associated macrophages (TAM) are abundant tumor myeloid cells that are immunosuppressive, pro-tumorigenic, and have a highly negative prognostic factor. Despite this, there is a lack of efficient TAM-specific therapeutics capable of reducing SPP1 expression. Here, on a phenotypic screen is reported to identify small molecule SPP1 modulators in macrophages. Several hits and incorporated them into a TAM-avid systemic nanoformulation are identified. It is shown that the lead compound (CANDI460) can down-regulate SPP1 in vitro and in vivo and lead to tumor remissions in different murine models. These findings are important as they offer a promising avenue for developing novel therapeutic strategies targeting TAM.

Supercontinuum-tailoring multicolor imaging reveals spatiotemporal dynamics of heterogeneous tumor evolution

Tumor heterogeneity and tumor evolution contribute to cancer treatment failure. To understand how selective pressures drive heterogeneous tumor evolution, it would be useful to image multiple important components and tumor subclones in vivo. We propose a supercontinuum-tailoring two-photon microscope (SCT-TPM) and realize simultaneous observation of nine fluorophores with a single light beam, breaking through the 'color barrier' of intravital two-photon fluorescence imaging. It achieves excitation multiplexing only by modulating the phase of fiber supercontinuum (SC), allowing to capture rapid events of multiple targets with maintaining precise spatial alignment. We employ SCT-TPM to visualize the spatiotemporal dynamics of heterogeneous tumor evolution under host immune surveillance, particularly the behaviors and interactions of six tumor subclones, immune cells and vascular network, and thus infer the trajectories of tumor progression and clonal competition. SCT-TPM opens up the possibility of tumor lineage tracking and mechanism exploration in living biological systems.

Immunomodulatory Effects of Halichondrin Isolated from Marine Sponges and Its Synthetic Analogs in Oncological Applications

Marine natural products comprise unique chemical structures and vast varieties of biological activities. This review aims to summarize halichondrin, a marine natural product, and its synthetic analogs along with its therapeutic properties and mechanisms. Halichondrin and its analogs, derived from marine sponges, exhibit potent antineoplastic properties, making them promising candidates for cancer therapeutics. These compounds, characterized by their complex molecular structures, have demonstrated significant efficacy in inhibiting microtubule dynamics, leading to cell cycle arrest and apoptosis in various cancer cell lines. Several types of halichondrins such as halichondrins B, C, norhalichondrin B, and homohalichondrin B have been discovered with similar anticancer and antitumor characteristics. Since naturally available halichondrins show hurdles in synthesis, recent advancements in synthetic methodologies have enabled the development of several halichondrin analogs, such as E7389 (eribulin), which have shown improved therapeutic indices. Eribulin has shown excellent immunomodulatory properties by several mechanisms such as reprogramming tumor microenvironments, facilitating the infiltration and activation of immune cells, and inhibiting microtubule dynamics. Despite promising results, challenges remain in the synthesis and clinical application of these compounds. This review explores the mechanisms underlying the immunomodulatory activity of halichondrin and its analogs in cancer therapy, along with their clinical applications and potential for future drug development.

Pharmacological Polarization of Tumor-Associated Macrophages Toward a CXCL9 Antitumor Phenotype

Tumor-associated macrophages (TAM) are a diverse population of myeloid cells that are often abundant and immunosuppressive in human cancers. CXCL9Hi TAM has recently been described to have an antitumor phenotype and is linked to immune checkpoint response. Despite the emerging understanding of the unique antitumor TAM phenotype, there is a lack of TAM-specific therapeutics to exploit this new biological understanding. Here, the discovery and characterization of multiple small-molecule enhancers of chemokine ligand 9 (CXCL9) and their targeted delivery in a TAM-avid systemic nanoformulation is reported. With this strategy, it is efficient encapsulation and release of multiple drug loads that can efficiently induce CXCL9 expression in macrophages, both in vitro and in vivo in a mouse tumor model. These observations provide a window into the molecular features that define TAM-specific states, an insight a novel therapeutic anticancer approach is used to discover.

Single-Cell Proliferation Microfluidic Device for High Throughput Investigation of Replicative Potential and Drug Resistance of Cancer Cells

Introduction

Cell proliferation represents a major hallmark of cancer biology, and manifests itself in the assessment of tumor growth, drug resistance and metastasis. Tracking cell proliferation or cell fate at the single-cell level can reveal phenotypic heterogeneity. However, characterization of cell proliferation is typically done in bulk assays which does not inform on cells that can proliferate under given environmental perturbations. Thus, there is a need for single-cell approaches that allow longitudinal tracking of the fate of a large number of individual cells to reveal diverse phenotypes.

Methods

We fabricated a new microfluidic architecture for high efficiency capture of single tumor cells, with the capacity to monitor cell divisions across multiple daughter cells. This single-cell proliferation (SCP) device enabled the quantification of the fate of more than 1000 individual cancer cells longitudinally, allowing comprehensive profiling of the phenotypic heterogeneity that would be otherwise masked in standard cell proliferation assays. We characterized the efficiency of single cell capture and demonstrated the utility of the SCP device by exposing MCF-7 breast tumor cells to different doses of the chemotherapeutic agent doxorubicin.

Results

The single cell trapping efficiency of the SCP device was found to be ~ 85%. At the low doses of doxorubicin (0.01 µM, 0.001 µM, 0.0001 µM), we observed that 50-80% of the drug-treated cells had undergone proliferation, and less than 10% of the cells do not proliferate. Additionally, we demonstrated the potential of the SCP device in circulating tumor cell applications where minimizing target cell loss is critical. We showed selective capture of breast tumor cells from a binary mixture of cells (tumor cells and white blood cells) that was isolated from blood processing. We successfully characterized the proliferation statistics of these captured cells despite their extremely low counts in the original binary suspension.

Conclusions

The SCP device has significant potential for cancer research with the ability to quantify proliferation statistics of individual tumor cells, opening new avenues of investigation ranging from evaluating drug resistance of anti-cancer compounds to monitoring the replicative potential of patient-derived cells.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00773-z.

Perfusion Window Chambers Enable Interventional Analyses of Tumor Microenvironments

Intravital microscopy (IVM) allows spatial and temporal imaging of different cell types in intact live tissue microenvironments. IVM has played a critical role in understanding cancer biology, invasion, metastases, and drug development. One considerable impediment to the field is the inability to interrogate the tumor microenvironment and its communication cascades during disease progression and therapeutic interventions. Here, a new implantable perfusion window chamber (PWC) is described that allows high-fidelity in vivo microscopy, local administration of stains and drugs, and longitudinal sampling of tumor interstitial fluid. This study shows that the new PWC design allows cyclic multiplexed imaging in vivo, imaging of drug action, and sampling of tumor-shed materials. The PWC will be broadly useful as a novel perturbable in vivo system for deciphering biology in complex microenvironments.

Multidimensional Imaging of Breast Cancer

Breast cancer is a pathological condition characterized by high morphological and molecular heterogeneity. Not only the breast cancer cells, but also their tumor micro-environment consists of a multitude of cell types and states, which continuously evolve throughout progression of the disease. To understand breast cancer evolution within this complex environment, in situ analysis of breast cancer and their co-evolving cells and structures in space and time are essential. In this review, recent technical advances in three-dimensional (3D) and intravital imaging of breast cancer are discussed. Moreover, we highlight the resulting new knowledge on breast cancer biology obtained through these innovative imaging technologies. Finally, we discuss how multidimensional imaging technologies can be integrated with molecular profiling to understand the full complexity of breast cancer and the tumor micro-environment during tumor progression and treatment response.

Intravital imaging to study cancer progression and metastasis

Navigation through the bulk tumour, entry into the blood vasculature, survival in the circulation, exit at distant sites and resumption of proliferation are all steps necessary for tumour cells to successfully metastasize. The ability of tumour cells to complete these steps is highly dependent on the timing and sequence of the interactions that these cells have with the tumour microenvironment (TME), including stromal cells, the extracellular matrix and soluble factors. The TME thus plays a major role in determining the overall metastatic phenotype of tumours. The complexity and cause-and-effect dynamics of the TME cannot currently be recapitulated in vitro or inferred from studies of fixed tissue, and are best studied in vivo, in real time and at single-cell resolution. Intravital imaging (IVI) offers these capabilities, and recent years have been a time of immense growth and innovation in the field. Here we review some of the recent advances in IVI of mammalian models of cancer and describe how IVI is being used to understand cancer progression and metastasis, and to develop novel treatments and therapies. We describe new techniques that allow access to a range of tissue and cancer types, novel fluorescent reporters and biosensors that allow fate mapping and the probing of functional and phenotypic states, and the clinical applications that have arisen from applying these techniques, reporters and biosensors to study cancer. We finish by presenting some of the challenges that remain in the field, how to address them and future perspectives.

Multinuclear MRI in Drug Discovery

The continuous development of magnetic resonance imaging broadens the range of applications to newer areas. Using MRI, we can not only visualize, but also track pharmaceutical substances and labeled cells in both in vivo and in vitro tests. ¹H is widely used in the MRI method, which is determined by its high content in the human body. The potential of the MRI method makes it an excellent tool for imaging the morphology of the examined objects, and also enables registration of changes at the level of metabolism. There are several reports in the scientific publications on the use of clinical MRI for in vitro tracking. The use of multinuclear MRI has great potential for scientific research and clinical studies. Tuning MRI scanners to the Larmor frequency of a given nucleus, allows imaging without tissue background. Heavy nuclei are components of both drugs and contrast agents and molecular complexes. The implementation of hyperpolarization techniques allows for better MRI sensitivity. The aim of this review is to present the use of multinuclear MRI for investigations in drug delivery.

Intravital microscopy for real-time monitoring of drug delivery and nanobiological processes

Intravital microscopy (IVM) expands our understanding of cellular and molecular processes, with applications ranging from fundamental biology to (patho)physiology and immunology, as well as from drug delivery to drug processing and drug efficacy testing. In this review, we highlight modalities, methods and model organisms that make up today's IVM landscape, and we present how IVM - via its high spatiotemporal resolution - enables analysis of metabolites, small molecules, nanoparticles, immune cells, and the (tumor) tissue microenvironment. We furthermore present examples of how IVM facilitates the elucidation of nanomedicine kinetics and targeting mechanisms, as well as of biological processes such as immune cell death, host-pathogen interactions, metabolic states, and disease progression. We conclude by discussing the prospects of IVM clinical translation and examining the integration of machine learning in future IVM practice.

New and Emerging Research on Solute Carrier and ATP Binding Cassette Transporters in Drug Discovery and Development: Outlook From the International Transporter Consortium

Enabled by a plethora of new technologies, research in membrane transporters has exploded in the past decade. The goal of this state-of-the-art article is to describe recent advances in research on membrane transporters that are particularly relevant to drug discovery and development. This review covers advances in basic, translational, and clinical research that has led to an increased understanding of membrane transporters at all levels. At the basic level, we describe the available crystal structures of membrane transporters in both the solute carrier (SLC) and ATP binding cassette superfamilies, which has been enabled by the development of cryogenic electron microscopy methods. Next, we describe new research on lysosomal and mitochondrial transporters as well as recently deorphaned transporters in the SLC superfamily. The translational section includes a summary of proteomic research, which has led to a quantitative understanding of transporter levels in various cell types and tissues and new methods to modulate transporter function, such as allosteric modulators and targeted protein degraders of transporters. The section ends with a review of the effect of the gut microbiome on modulation of transporter function followed by a presentation of 3D cell cultures, which may enable in vivo predictions of transporter function. In the clinical section, we describe new genomic and pharmacogenomic research, highlighting important polymorphisms in transporters that are clinically relevant to many drugs. Finally, we describe new clinical tools, which are becoming increasingly available to enable precision medicine, with the application of tissue-derived small extracellular vesicles and real-world biomarkers.

Spatial analysis of drug absorption, distribution, metabolism, and toxicology using mass spectrometry imaging

Mass spectrometry imaging (MSI) is emerging as a powerful analytical tool for detection, quantification, and simultaneous spatial molecular imaging of endogenous and exogenous molecules via in situ mass spectrometry analysis of thin tissue sections without the requirement of chemical labeling. The MSI generates chemically specific and spatially resolved ion distribution information for administered drugs and metabolites, which allows numerous applications for studies involving various stages of drug absorption, distribution, metabolism, excretion, and toxicity (ADMET). MSI-based pharmacokinetic imaging analysis provides a histological context and cellular environment regarding dynamic drug distribution and metabolism processes, and facilitates the understanding of the spatial pharmacokinetics and pharmacodynamic properties of drugs. Herein, we discuss the MSI's current technological developments that offer qualitative, quantitative, and spatial location information of small molecule drugs, antibody, and oligonucleotides macromolecule drugs, and their metabolites in preclinical and clinical tissue specimens. We highlight the macro and micro drug-distribution in the whole-body, brain, lung, liver, kidney, stomach, intestine tissue sections, organoids, and the latest applications of MSI in pharmaceutical ADMET studies.

Overcoming differential tumor penetration of BRAF inhibitors using computationally guided combination therapy

BRAF-targeted kinase inhibitors (KIs) are used to treat malignancies including BRAF-mutant non-small cell lung cancer, colorectal cancer, anaplastic thyroid cancer, and, most prominently, melanoma. However, KI selection criteria in patients remain unclear, as are pharmacokinetic/pharmacodynamic (PK/PD) mechanisms that may limit context-dependent efficacy and differentiate related drugs. To address this issue, we imaged mouse models of BRAF-mutant cancers, fluorescent KI tracers, and unlabeled drug to calibrate in silico spatial PK/PD models. Results indicated that drug lipophilicity, plasma clearance, faster target dissociation, and, in particular, high albumin binding could limit dabrafenib action in visceral metastases compared to other KIs. This correlated with retrospective clinical observations. Computational modeling identified a timed strategy for combining dabrafenib and encorafenib to better sustain BRAF inhibition, which showed enhanced efficacy in mice. This study thus offers principles of spatial drug action that may help guide drug development, KI selection, and combination.

Nanotechnology Tools Enabling Biological Discovery

Over the years, the engineering aspect of nanotechnology has been significantly exploited. Medical intervention strategies have been developed by leveraging existing molecular biology knowledge and combining it with nanotechnology tools to improve outcomes. However, little attention has been paid to harnessing the strengths of nanotechnology as a biological discovery tool. Fundamental understanding of controlling dynamic biological processes at the subcellular level is key to developing personalized therapeutic and diagnostic interventions. Single-cell analyses using intravital microscopy, expansion microscopy, and microfluidic-based platforms have been helping to better understand cell heterogeneity in healthy and diseased cells, a major challenge in oncology. Also, single-cell analysis has revealed critical signaling pathways and biological intracellular components with key biological functions. The physical manipulation enabled by nanotools can allow real-time monitoring of biological changes at a single-cell level by sampling intracellular fluid from the same cell. The formation of intercellular highways by nanotube-like structures has important clinical implications such as metastasis development. The integration of nanomaterials into optical and molecular imaging techniques has rendered valuable morphological, structural, and biological information. Nanoscale imaging unravels mechanisms of temporality by enabling the visualization of nanoscale dynamics never observed or measured between individual cells with standard biological techniques. The exceptional sensitivity of nanozymes, artificial enzymes, make them perfect components of the next-generation mobile diagnostics devices. Here, we highlight these impactful cancer-related biological discoveries enabled by nanotechnology and producing a paradigm shift in cancer research and oncology.

Single-Cell Image-Based Analysis Reveals Chromatin Changes during the Acquisition of Tamoxifen Drug Resistance

Cancer drug resistance is the leading cause of cancer related deaths. The development of drug resistance can be partially contributed to tumor heterogeneity and epigenetic plasticity. However, the detailed molecular mechanism underlying epigenetic modulated drug resistance remains elusive. In this work, we systematically analyzed epigenetic changes in tamoxifen (Tam) responsive and resistant breast cancer cell line MCF7, and adopted a data-driven approach to identify key epigenetic features distinguishing between these two cell types. Significantly, we revealed that DNA methylation and H3K9me3 marks that constitute the heterochromatin are distinctively different between Tam-resistant and -responsive cells. We then performed time-lapse imaging of 5mC and H3K9me3 features using engineered probes. After Tam treatment, we observed a slow transition of MCF7 cells from a drug-responsive to -resistant population based on DNA methylation features. A similar trend was not observed using H3K9me3 probes. Collectively, our results suggest that DNA methylation changes partake in the establishment of Tam-resistant breast cancer cell lines. Instead of global changes in the DNA methylation level, the distribution of DNA methylation features inside the nucleus can be one of the drivers that facilitates the establishment of a drug resistant phenotype in MCF7.

Current Insights and Advancements in Head and Neck Cancer: Emerging Biomarkers and Therapeutics with Cues from Single Cell and 3D Model Omics Profiling

Head and neck cancer (HNC) is among the ten leading malignancies worldwide, with India solely contributing one-third of global oral cancer cases. The current focus of all cutting-edge strategies against this global malignancy are directed towards the heterogeneous tumor microenvironment that obstructs most treatment blueprints. Subsequent to the portrayal of established information, the review details the application of single cell technology, organoids and spheroid technology in relevance to head and neck cancer and the tumor microenvironment acknowledging the resistance pattern of the heterogeneous cell population in HNC. Bioinformatic tools are used for study of differentially expressed genes and further omics data analysis. However, these tools have several challenges and limitations when analyzing single-cell gene expression data that are discussed briefly. The review further examines the omics of HNC, through comprehensive analyses of genomics, transcriptomics, proteomics, metabolomics, and epigenomics profiles. Patterns of alterations vary between patients, thus heterogeneity and molecular alterations between patients have driven the clinical significance of molecular targeted therapies. The analyses of potential molecular targets in HNC are discussed with connotation to the alteration of key pathways in HNC followed by a comprehensive study of protein kinases as novel drug targets including its ATPase and additional binding pockets, non-catalytic domains and single residues. We herein review, the therapeutic agents targeting the potential biomarkers in light of new molecular targeted therapies. In the final analysis, this review suggests that the development of improved target-specific personalized therapies can combat HNC's global plight.

TP53 Null Mutations Identify Lung Cancer Cell Lines with Highest Sensitivity to the Nontaxane Microtubule Inhibitor Eribulin

The nontaxane microtubule inhibitor eribulin is an approved therapeutic for metastatic breast cancer and liposarcoma. Eribulin was previously tested in unselected patients with lung cancer and yielded a modest objective response rate of ∼5%-12%. Because lung cancers represent diverse histologies and driving oncogenic mutations, we postulated that eribulin may exhibit properties of a precision oncology agent with a previously undefined specificity for a molecularly distinct subset of lung cancers. Herein, we screened a panel of 44 non-small cell and small-cell lung cancer cell lines for in vitro growth sensitivity to eribulin. The results revealed a greater than 15,000-fold range in eribulin sensitivity (IC50 = 0.005-89 nM) among the cell lines that was not correlated with their sensitivity to the taxane-based inhibitor paclitaxel. The quartile of cell lines exhibiting the lowest eribulin IC50 values was not enriched for specific histologies, epithelial-mesenchymal differentiation, or specific oncogene drivers but was significantly enriched for nonsense/frameshift TP53 mutations and low-TP53 mRNA but not missense TP53 mutations. By comparison, the mutation status of cyclin-dependent kinase inhibitor 2A, STK11, and KEAP1 was not associated with eribulin sensitivity. Finally, the highest eribulin IC50 quartile (>1 nM) exhibited significantly elevated mRNA expression of the drug pump, ATP binding cassette B1, defined resistance mechanism to eribulin, and paclitaxel. The findings support further investigations into basic mechanisms by which complete lack of TP53 function regulates anticancer activity of eribulin and the potential utility of TP53 null phenotypes distinct from TP53 missense mutations as a biomarker of response in patients with lung cancer. SIGNIFICANCE STATEMENT: Distinct from precision oncology agents that are matched to cancers bearing oncogenically activated versions of their targets, microtubule inhibitors, such as eribulin, are deployed in an unselected manner. The results in this study demonstrate that lung cancer cell lines exhibiting the highest sensitivity to eribulin bear TP53 null phenotypes, supporting a rationale to consider the status of this tumor suppressor in the clinical setting.

Cytologic and Molecular Diagnostics for Vitreoretinal Lymphoma: Current Approaches and Emerging Single-Cell Analyses

Vitreoretinal lymphoma (VRL) is a rare ocular malignancy that manifests as diffuse large B-cell lymphoma. Early and accurate diagnosis is essential to prevent mistreatment and to reduce the high morbidity and mortality associated with VRL. The disease can be diagnosed using various methods, including cytology, immunohistochemistry, cytokine analysis, flow cytometry, and molecular analysis of bulk vitreous aspirates. Despite these options, VRL diagnosis remains challenging, as samples are often confounded by low cellularity, the presence of debris and non-target immunoreactive cells, and poor cytological preservation. As such, VRL diagnostic accuracy is limited by both false-positive and false-negative outcomes. Missed or inappropriate diagnosis may cause delays in treatment, which can have life-threatening consequences for patients with VRL. In this review, we summarize current knowledge and the diagnostic modalities used for VRL diagnosis. We also highlight several emerging molecular techniques, including high-resolution single cell-based analyses, which may enable more comprehensive and precise VRL diagnoses.

Quantification of Cellular Drug Biodistribution Addresses Challenges in Evaluating in vitro and in vivo Encapsulated Drug Delivery

Nanoencapsulated drug delivery to solid tumors is a promising approach to overcome pharmacokinetic limitations of therapeutic drugs. However, encapsulation leads to complex drug biodistribution and delivery making analysis of delivery efficacy challenging. As proxies, nanocarrier accumulation or total tumor drug uptake in the tumor are used to evaluate delivery. Yet, these measurements fail to assess delivery of active, released drug to the target, and thus it commonly remains unknown if drug-target occupancy has been achieved. Here, we develop an approach to evaluate the delivery of encapsulated drug to the target, where residual drug target vacancy is measured using a fluorescent drug analog. In vitro measurements reveal that burst release governs drug delivery independent of nanoparticle uptake, and highlight limitations of evaluating nanoencapsulated drug delivery in these models. In vivo, however, our approach captures successful nanoencapsulated delivery, finding that tumor stromal cells drive nanoparticle accumulation and mediate drug delivery to adjacent cancer cells. These results, and generalizable approach, provide a critical advance to evaluate delivery of encapsulated drug to the drug target - the central objective of nanotherapeutics.

Visualization of the distribution of nanoparticle-formulated AZD2811 in mouse tumor model using matrix-assisted laser desorption ionization mass spectrometry imaging

Penetration of nanoparticles into viable tumor regions is essential for an effective response. Mass spectrometry imaging (MSI) is a novel method for evaluating the intratumoral pharmacokinetics (PK) of a drug in terms of spatial distribution. The application of MSI for analysis of nanomedicine PK remains in its infancy. In this study, we evaluated the applicability of MALDI-MSI for nanoparticle-formulated drug visualization in tumors and biopsies, with an aim toward future application in clinical nanomedicine research. We established an analytic method for the free drug (AZD2811) and then applied it to visualize nanoparticle-formulated AZD2811. MSI analysis demonstrated heterogeneous intratumoral drug distribution in three xenograft tumors. The intensity of MSI signals correlated well with total drug concentration in tumors, indicating that drug distribution can be monitored quantitatively. Analysis of tumor biopsies indicated that MSI is applicable for analyzing the distribution of nanoparticle-formulated drugs in tumor biopsies, suggesting clinical applicability.

Understanding the in vivo Fate of Advanced Materials by Imaging

Engineered materials are ubiquitous in biomedical applications ranging from systemic drug delivery systems to orthopedic implants, and their actions unfold across multiple time- and length-scales. The efficacy and safety of biologics, nanomaterials, and macroscopic implants are all dictated by the same general principles of pharmacology as apply to small molecule drugs, comprising how the body affects materials (pharmacokinetics, PK) and conversely how materials affect the body (pharmacodynamics, PD). Imaging technologies play an increasingly insightful role in monitoring both of these processes, often simultaneously: translational macroscopic imaging modalities such as MRI and PET/CT offer whole-body quantitation of biodistribution and structural or molecular response, while ex vivo approaches and optical imaging via in vivo (intravital) microscopy reveal behaviors at subcellular resolution. In this review, the authors survey developments in imaging the in situ behavior of systemically and locally administered materials, with a particular focus on using microscopy to understand transport, target engagement, and downstream host responses at a single-cell level. The themes of microenvironmental influence, controlled drug release, on-target molecular action, and immune response, especially as mediated by macrophages and other myeloid cells are examined. Finally, the future directions of how new imaging technologies may propel efficient clinical translation of next-generation therapeutics and medical devices are proposed.

The Use of Molecular Subtypes for Precision Therapy of Recurrent and Metastatic Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor in the digestive tract. Tyrosine kinase inhibitors (TKIs), represented by imatinib, sunitinib, and regorafenib, have become the main treatment for recurrent and metastatic GISTs. With the wide application of mutation analysis and the precision medicine, molecular characteristics have been determined that not only predict the prognosis of patients with recurrent and metastatic GISTs, but also are closely related to the efficacy of first-, second- and third-line TKIs for GISTs, as well as other TKIs. Despite the significant effects of TKIs, the emergence of primary and secondary resistance ultimately leads to treatment failure and tumor progression. Currently, due to the signal transmission of KIT/PDGFRA during onset and tumor progression, strategies to counteract drug resistance include the replacement of TKIs and the development of new drugs that are directed towards carcinogenic mutations. In addition, it is also the embodiment of precision medicine for GISTs to explore new carcinogenic mechanisms and develop new drugs relying on new biotechnology. Surgery can benefit specific patients but its major purpose is to diminish the resistant clones. However, the prognosis of recurrent and metastatic patients is still unsatisfactory. Therefore, it is worth paying attention to how to maximize the benefits for patients.

Frontiers in Intravital Multiphoton Microscopy of Cancer

Background

Cancer is a highly complex disease which involves the co-operation of tumor cells with multiple types of host cells and the extracellular matrix. Cancer studies which rely solely on static measurements of individual cell types are insufficient to dissect this complexity. In the last two decades, intravital microscopy has established itself as a powerful technique that can significantly improve our understanding of cancer by revealing the dynamic interactions governing cancer initiation, progression and treatment effects, in living animals. This review focuses on intravital multiphoton microscopy (IV-MPM) applications in mouse models of cancer.

Recent Findings

IV-MPM studies have already enabled a deeper understanding of the complex events occurring in cancer, at the molecular, cellular and tissue levels. Multiple cells types, present in different tissues, influence cancer cell behavior via activation of distinct signaling pathways. As a result, the boundaries in the field of IV-MPM are continuously being pushed to provide an integrated comprehension of cancer. We propose that optics, informatics and cancer (cell) biology are co-evolving as a new field. We have identified four emerging themes in this new field. First, new microscopy systems and image processing algorithms are enabling the simultaneous identification of multiple interactions between the tumor cells and the components of the tumor microenvironment. Second, techniques from molecular biology are being exploited to visualize subcellular structures and protein activities within individual cells of interest, and relate those to phenotypic decisions, opening the door for "in vivo cell biology". Third, combining IV-MPM with additional imaging modalities, or omics studies, holds promise for linking the cell phenotype to its genotype, metabolic state or tissue location. Finally, the clinical use of IV-MPM for analyzing efficacy of anti-cancer treatments is steadily growing, suggesting a future role of IV-MPM for personalized medicine.

Conclusion

IV-MPM has revolutionized visualization of tumor-microenvironment interactions in real time. Moving forward, incorporation of novel optics, automated image processing, and omics technologies, in the study of cancer biology, will not only advance our understanding of the underlying complexities but will also leverage the unique aspects of IV-MPM for clinical use.

Fluorescence anisotropy imaging in drug discovery

Non-invasive measurement of drug-target engagement can provide critical insights in the molecular pharmacology of small molecule drugs. Fluorescence polarization/fluorescence anisotropy measurements are commonly employed in protein/cell screening assays. However, the expansion of such measurements to the in vivo setting has proven difficult until recently. With the advent of high-resolution fluorescence anisotropy microscopy it is now possible to perform kinetic measurements of intracellular drug distribution and target engagement in commonly used mouse models. In this review we discuss the background, current advances and future perspectives in intravital fluorescence anisotropy measurements to derive pharmacokinetic and pharmacodynamic measurements in single cells and whole organs.

Single-Cell Intravital Microscopy of Trastuzumab Quantifies Heterogeneous in vivo Kinetics

Cell-to-cell heterogeneity can substantially impact drug response, especially for monoclonal antibody (mAb) therapies that may exhibit variability in both delivery (pharmacokinetics) and action (pharmacodynamics) within solid tumors. However, it has traditionally been difficult to examine the kinetics of mAb delivery at a single-cell level and in a manner that enables controlled dissection of target-dependent and -independent behaviors. To address this issue, here we developed an in vivo confocal (intravital) microscopy approach to study single-cell mAb pharmacology in a mosaic xenograft comprising a mixture of cancer cells with variable expression of the receptor HER2. As a proof-of-principle, we applied this model to trastuzumab therapy, a HER2-targeted mAb widely used for treating breast and gastric cancer patients. Trastuzumab accumulated to a higher degree in HER2-over expressing tumor cells compared to HER2-low tumor cells (~5:1 ratio at 24 h after administration) but importantly, the majority actually accumulated in tumor-associated phagocytes. For example, 24 h after IV administration over 50% of tumoral trastuzumab was found in phagocytes whereas at 48 h it was >80%. Altogether, these results reveal the dynamics of how phagocytes influence mAb behavior in vivo, and demonstrate an application of intravital microscopy for quantitative single-cell measurement of mAb distribution and retention in tumors with heterogeneous target expression. © 2019 International Society for Advancement of Cytometry.

Interplay of Efflux Transporters with Glucuronidation and Its Impact on Subcellular Aglycone and Glucuronide Disposition: A Case Study with Kaempferol

Glucuronidation is a major process of drug metabolism and elimination that generally governs drug efficacy and toxicity. Publications have demonstrated that efflux transporters control intracellular glucuronidation metabolism. However, it is still unclear whether and how efflux transporters interact with UDP-glucuronosyltransferases (UGTs) in subcellular organelles. In this study, kaempferol, a model fluorescent flavonoid, was used to investigate the interplay of glucuronidation with transport at the subcellular level. Human recombinant UGTs and microsomes were utilized to characterize the in vitro glucuronidation kinetics of kaempferol. The inhibition of UGTs and efflux transporters on the subcellular disposition of kaempferol were determined visually and quantitatively in Caco-2/TC7 cells. The knockout of transporters on the subcellular accumulation of kaempferol in liver and intestine were evaluated visually. ROS and Nrf2 were assayed to evaluate the pharmacological activities of kaempferol. The results showed that UGT1A9 is the primary enzyme responsible for kaempferol glucuronidation. Visual and quantitative data showed that the UGT1A9 inhibitor carvacrol caused a significant rise in subcellular aglycone and reduction in subcellular glucuronides of kaempferol. The inhibition and knockout of transporters, such as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-associated proteins (MRPs), exhibited a marked increase in subcellular kaempferol and decrease in its subcellular glucuronides. Correspondingly, inhibition of UGT1A9 and transporters led to increased kaempferol and, consequently, a significantly enhanced ROS scavenging efficiency and nuclear translocation of Nrf2. In conclusion, the interplay of efflux transporters (P-gp, BCRP, and MRPs) and UGTs govern the subcellular exposure and corresponding pharmacological activity of kaempferol.

Heterogeneity in tumor chromatin-doxorubicin binding revealed by in vivo fluorescence lifetime imaging confocal endomicroscopy

We present an approach to quantify drug-target engagement using in vivo fluorescence endomicroscopy, validated with in vitro measurements. Doxorubicin binding to chromatin changes the fluorescence lifetime of histone-GFP fusions that we measure in vivo at single-cell resolution using a confocal laparo/endomicroscope. We measure both intra- and inter-tumor heterogeneity in doxorubicin chromatin engagement in a model of peritoneal metastasis of ovarian cancer, revealing striking variation in the efficacy of doxorubicin-chromatin binding depending on intra-peritoneal or intravenous delivery. Further, we observe significant variations in doxorubicin-chromatin binding between different metastases in the same mouse and between different regions of the same metastasis. The quantitative nature of fluorescence lifetime imaging enables direct comparison of drug-target engagement for different drug delivery routes and between in vitro and in vivo experiments. This uncovers different rates of cell killing for the same level of doxorubicin binding in vitro and in vivo.

Molecular mobility and activity in an intravital imaging setting - implications for cancer progression and targeting

Molecular mobility, localisation and spatiotemporal activity are at the core of cell biological processes and deregulation of these dynamic events can underpin disease development and progression. Recent advances in intravital imaging techniques in mice are providing new avenues to study real-time molecular behaviour in intact tissues within a live organism and to gain exciting insights into the intricate regulation of live cell biology at the microscale level. The monitoring of fluorescently labelled proteins and agents can be combined with autofluorescent properties of the microenvironment to provide a comprehensive snapshot of in vivo cell biology. In this Review, we summarise recent intravital microscopy approaches in mice, in processes ranging from normal development and homeostasis to disease progression and treatment in cancer, where we emphasise the utility of intravital imaging to observe dynamic and transient events in vivo We also highlight the recent integration of advanced subcellular imaging techniques into the intravital imaging pipeline, which can provide in-depth biological information beyond the single-cell level. We conclude with an outlook of ongoing developments in intravital microscopy towards imaging in humans, as well as provide an overview of the challenges the intravital imaging community currently faces and outline potential ways for overcoming these hurdles.

Targeting Ligand Specificity Linked to Tumor Tissue Topological Heterogeneity via Single-Cell Micro-Pharmacological Modeling

Targeted therapy has held promise to be a successful anticancer treatment due to its specificity towards tumor cells that express the target receptors. However, not all targeting drugs used in the clinic are equally effective in tumor eradication. To examine which biochemical and biophysical properties of targeted agents are pivotal for their effective distribution inside the tumor and their efficient cellular uptake, we combine mathematical micro-pharmacological modeling with in vivo imaging of targeted human xenograft tumors in SCID mice. The mathematical model calibrated to experimental data was used to explore properties of the targeting ligand (diffusion and affinity) and ligand release schemes (rates and concentrations) with a goal to identify the properties of cells and ligands that enable high receptor saturation. By accounting for heterogeneities typical of in vivo tumors, our model was able to identify cell- and tissue-level barriers to efficient drug uptake. This work provides a base for utilizing experimentally measurable properties of a ligand-targeted agent and patient-specific attributes of the tumor tissue to support the development of novel targeted imaging agents and for improvement in their delivery to individual tumor cells.

ABCB1 and ABCC11 confer resistance to eribulin in breast cancer cell lines

This study aimed to elucidate the mechanisms underlying the resistance of breast cancer to eribulin. Seven eribulin-resistant breast cancer cell lines (MCF7/E, BT474/E, ZR75-1/E, SKBR3/E, MDA-MB-231/E, Hs578T/E, and MDA-MB-157/E) were established. mRNA and protein expression of ATP-binding cassette subfamily B member 1 (ABCB1) and subfamily C member 11 (ABCC11) increased in all eribulin-resistant cell lines compared to the parental cell lines. When ABCB1 or ABCC11 expression was inhibited by small interfering RNA in MCF7/E, BT474/E, and MDA-MB-231/E cells, eribulin sensitivity was partially restored. Moreover, eribulin resistance was attenuated additively by inhibiting ABCB1 and ABCC11 in MCF7/E cells. Additionally, overexpression of exogenous ABCB1 or ABCC11 in HEK293T cells conferred resistance to eribulin. MCF7/E and MDA-MB-231/E cells showed cross-resistance to paclitaxel, doxorubicin, and fluorouracil. Inhibition of ABCB1 partially restored paclitaxel and doxorubicin sensitivity. Partial restoration of fluorouracil sensitivity was induced by inhibiting ABCC11 in MCF7/E and MDA-MB-231/E cells. Both ABCB1 and ABCC11 are involved in the development of eribulin resistance in breast cancer cells in vitro regardless of the breast cancer subtype. Thus, ABCB1 and ABCC11 expression may be used as a biomarker for predicting the response to eribulin in patients with breast cancer. Concomitant inhibition of ABCB1 and ABCC11 might help enhance the antitumor effects of eribulin.

Micropharmacology: An In Silico Approach for Assessing Drug Efficacy Within a Tumor Tissue

Systemic chemotherapy is one of the main anticancer treatments used for most kinds of clinically diagnosed tumors. However, the efficacy of these drugs can be hampered by the physical attributes of the tumor tissue, such as tortuous vasculature, dense and fibrous extracellular matrix, irregular cellular architecture, tumor metabolic gradients, and non-uniform expression of the cell membrane receptors. This can impede the transport of therapeutic agents to tumor cells in sufficient quantities. In addition, tumor microenvironments undergo dynamic spatio-temporal changes during tumor progression and treatment, which can also obstruct drug efficacy. To examine ways to improve drug delivery on a cell-to-tissue scale (single-cell pharmacology), we developed the microscale pharmacokinetics/pharmacodynamics (microPKPD) modeling framework. Our model is modular and can be adjusted to include only the mathematical equations that are crucial for a biological problem under consideration. This modularity makes the model applicable to a broad range of pharmacological cases. As an illustration, we present two specific applications of the microPKPD methodology that help to identify optimal drug properties. The hypoxia-activated drugs example uses continuous drug concentrations, diffusive-advective transport through the tumor interstitium, and passive transmembrane drug uptake. The targeted therapy example represents drug molecules as discrete particles that move by diffusion and actively bind to cell receptors. The proposed modeling approach takes into account the explicit tumor tissue morphology, its metabolic landscape and/or specific receptor distribution. All these tumor attributes can be assessed from patients' diagnostic biopsies; thus, the proposed methodology can be developed into a tool suitable for personalized medicine, such as neoadjuvant chemotherapy.

Imaging approaches to optimize molecular therapies

Imaging, including its use for innovative tissue sampling, is slowly being recognized as playing a pivotal role in drug development, clinical trial design, and more effective delivery and monitoring of molecular therapies. The challenge is that, while a considerable number of new imaging technologies and new targeted tracers have been developed for cancer imaging in recent years, the technologies are neither evenly distributed nor evenly implemented. Furthermore, many imaging innovations are not validated and are not ready for widespread use in drug development or in clinical trial designs. Inconsistent and often erroneous use of terminology related to quantitative imaging biomarkers has also played a role in slowing their development and implementation. We examine opportunities for, and challenges of, the use of imaging biomarkers to facilitate development of molecular therapies and to accelerate progress in clinical trial design. In the future, in vivo molecular imaging, image-guided tissue sampling for mutational analyses ("high-content biopsies"), and noninvasive in vitro tests ("liquid biopsies") will likely be used in various combinations to provide the best possible monitoring and individualized treatment plans for cancer patients.

Engineering and physical sciences in oncology: challenges and opportunities

The principles of engineering and physics have been applied to oncology for nearly 50 years. Engineers and physical scientists have made contributions to all aspects of cancer biology, from quantitative understanding of tumour growth and progression to improved detection and treatment of cancer. Many early efforts focused on experimental and computational modelling of drug distribution, cell cycle kinetics and tumour growth dynamics. In the past decade, we have witnessed exponential growth at the interface of engineering, physics and oncology that has been fuelled by advances in fields including materials science, microfabrication, nanomedicine, microfluidics, imaging, and catalysed by new programmes at the National Institutes of Health (NIH), including the National Institute of Biomedical Imaging and Bioengineering (NIBIB), Physical Sciences in Oncology, and the National Cancer Institute (NCI) Alliance for Nanotechnology. Here, we review the advances made at the interface of engineering and physical sciences and oncology in four important areas: the physical microenvironment of the tumour and technological advances in drug delivery; cellular and molecular imaging; and microfluidics and microfabrication. We discussthe research advances, opportunities and challenges for integrating engineering and physical sciences with oncology to develop new methods to study, detect and treat cancer, and we also describe the future outlook for these emerging areas.

Nano-palladium is a cellular catalyst for in vivo chemistry

Palladium catalysts have been widely adopted for organic synthesis and diverse industrial applications given their efficacy and safety, yet their biological in vivo use has been limited to date. Here we show that nanoencapsulated palladium is an effective means to target and treat disease through in vivo catalysis. Palladium nanoparticles (Pd-NPs) were created by screening different Pd compounds and then encapsulating bis[tri(2-furyl)phosphine]palladium(II) dichloride in a biocompatible poly(lactic-co-glycolic acid)-b-polyethyleneglycol platform. Using mouse models of cancer, the NPs efficiently accumulated in tumours, where the Pd-NP activated different model prodrugs. Longitudinal studies confirmed that prodrug activation by Pd-NP inhibits tumour growth, extends survival in tumour-bearing mice and mitigates toxicity compared to standard doxorubicin formulations. Thus, here we demonstrate safe and efficacious in vivo catalytic activity of a Pd compound in mammals.

Palladium (Pd) is a well-known catalyst in organic chemistry but its use in nanomedicine is limited. Here, the authors design a Pd nanoparticle that triggers the activation of an antitumour prodrug in vivo, which shows efficacy and improves toxicity compared to traditional solvent- and nanoparticle-drug formulations.

Measurement of drug-target engagement in live cells by two-photon fluorescence anisotropy imaging

The ability to directly image and quantify drug-target engagement and drug distribution with subcellular resolution in live cells and whole organisms is a prerequisite to establishing accurate models of the kinetics and dynamics of drug action. Such methods would thus have far-reaching applications in drug development and molecular pharmacology. We recently presented one such technique based on fluorescence anisotropy, a spectroscopic method based on polarization light analysis and capable of measuring the binding interaction between molecules. Our technique allows the direct characterization of target engagement of fluorescently labeled drugs, using fluorophores with a fluorescence lifetime larger than the rotational correlation of the bound complex. Here we describe an optimized protocol for simultaneous dual-channel two-photon fluorescence anisotropy microscopy acquisition to perform drug-target measurements. We also provide the necessary software to implement stream processing to visualize images and to calculate quantitative parameters. The assembly and characterization part of the protocol can be implemented in 1 d. Sample preparation, characterization and imaging of drug binding can be completed in 2 d. Although currently adapted to an Olympus FV1000MPE microscope, the protocol can be extended to other commercial or custom-built microscopes.

Imaging of anticancer drug action in single cells

Imaging is widely used in anticancer drug development, typically for whole-body tracking of labelled drugs to different organs or to assess drug efficacy through volumetric measurements. However, increasing attention has been drawn to pharmacology at the single-cell level. Diverse cell types, including cancer-associated immune cells, physicochemical features of the tumour microenvironment and heterogeneous cell behaviour all affect drug delivery, response and resistance. This Review summarizes developments in the imaging of in vivo anticancer drug action, with a focus on microscopy approaches at the single-cell level and translational lessons for the clinic.

Application of single-cell technology in cancer research

In this review, we have outlined the application of single-cell technology in cancer research. Single-cell technology has made encouraging progress in recent years and now provides the means to detect rare cancer cells such as circulating tumor cells and cancer stem cells. We reveal how this technology has advanced the analysis of intratumor heterogeneity and tumor epigenetics, and guided individualized treatment strategies. The future prospects now are to bring single-cell technology into the clinical arena. We believe that the clinical application of single-cell technology will be beneficial in cancer diagnostics and treatment, and ultimately improve survival in cancer patients.

Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior

Therapeutic nanoparticles (NPs) can deliver cytotoxic chemotherapeutics and other drugs more safely and efficiently to patients; furthermore, selective delivery to target tissues can theoretically be accomplished actively through coating NPs with molecular ligands, and passively through exploiting physiological "enhanced permeability and retention" features. However, clinical trial results have been mixed in showing improved efficacy with drug nanoencapsulation, largely due to heterogeneous NP accumulation at target sites across patients. Thus, a clear need exists to better understand why many NP strategies fail in vivo and not result in significantly improved tumor uptake or therapeutic response. Multicolor in vivo confocal fluorescence imaging (intravital microscopy; IVM) enables integrated pharmacokinetic and pharmacodynamic (PK/PD) measurement at the single-cell level, and has helped answer key questions regarding the biological mechanisms of in vivo NP behavior. This review summarizes progress to date and also describes useful technical strategies for successful IVM experimentation.

Design and Development of Fluorescent Vemurafenib Analogs for In Vivo Imaging

Herein we describe fluorescent derivatives of vemurafenib to probe therapeutic BRAF inhibition in live cells and in vivo. The compounds were evaluated and compared by determining target binding, inhibition of mutant BRAF melanoma cell lines and live cell imaging. We show that vemurafenib-BODIPY is a superior imaging drug to visualize the targets of vemurafenib in live cells and in vivo in non-resistant and resistant melanoma tumors.

Heterogeneity of macrophage infiltration and therapeutic response in lung carcinoma revealed by 3D organ imaging

Involvement of the immune system in tumour progression is at the forefront of cancer research. Analysis of the tumour immune microenvironment has yielded a wealth of information on tumour biology, and alterations in some immune subtypes, such as tumour-associated macrophages (TAM), can be strong prognostic indicators. Here, we use optical tissue clearing and a TAM-targeting injectable fluorescent nanoparticle (NP) to examine three-dimensional TAM composition, tumour-to-tumour heterogeneity, response to colony-stimulating factor 1 receptor (CSF-1R) blockade and nanoparticle-based drug delivery in murine pulmonary carcinoma. The method allows for rapid tumour volume assessment and spatial information on TAM infiltration at the cellular level in entire lungs. This method reveals that TAM density was heterogeneous across tumours in the same animal, overall TAM density is different among separate pulmonary tumour models, nanotherapeutic drug delivery correlated with TAM heterogeneity, and successful response to CSF-1R blockade is characterized by enhanced TAM penetration throughout and within tumours.

Tumour-associated macrophages (TAM) can be used as prognostic indicators in cancer. Here, the authors establish a platform for high-throughput 3D microscopy in murine lung carcinoma that allows to visualize TAMs infiltration throughout the entire lung, response to CSF-1R blockade and nanoparticle drug delivery.

Two-Photon Intravital Microscopy Animal Preparation Protocol to Study Cellular Dynamics in Pathogenesis

Two-photon intravital microscopy (2P-IVM) is an advanced imaging platform that allows the visualization of dynamic processes at subcellular resolution in vivo. Dynamic processes like cell migration, cell proliferation, cell-cell interactions, and cell signaling have an interactive character and occur in complex environments. Hence, it is of pivotal importance to study these processes in living animals, using for example 2P-IVM. 2P-IVM can be performed on a variety of tissues, from the skin of the animal to internal organs, and a variety of methods can be utilized to perform 2P-IVM on these tissues. Here, we discuss the protocols and considerations for four of those 2P-IVM methods, namely tissue explant imaging, skin imaging, surgical exposure imaging, and multi-day window imaging. We carefully compare and explain in depth how to set up each method. Lastly, in the notes section we mention some alternative solutions for the 2P-IVM methods described. In conclusion, this protocol can be used as a guide towards deciding which 2P-IVM method to use and to enable the setup of this method.

Cancer nanomedicine: progress, challenges and opportunities

The intrinsic limits of conventional cancer therapies prompted the development and application of various nanotechnologies for more effective and safer cancer treatment, herein referred to as cancer nanomedicine. Considerable technological success has been achieved in this field, but the main obstacles to nanomedicine becoming a new paradigm in cancer therapy stem from the complexities and heterogeneity of tumour biology, an incomplete understanding of nano-bio interactions and the challenges regarding chemistry, manufacturing and controls required for clinical translation and commercialization. This Review highlights the progress, challenges and opportunities in cancer nanomedicine and discusses novel engineering approaches that capitalize on our growing understanding of tumour biology and nano-bio interactions to develop more effective nanotherapeutics for cancer patients.

Cancer nanomedicine: progress, challenges and opportunities

The intrinsic limits of conventional cancer therapies prompted the development and application of various nanotechnologies for more effective and safer cancer treatment, herein referred to as cancer nanomedicine. Considerable technological success has been achieved in this field, but the main obstacles to nanomedicine becoming a new paradigm in cancer therapy stem from the complexities and heterogeneity of tumour biology, an incomplete understanding of nano-bio interactions and the challenges regarding chemistry, manufacturing and controls required for clinical translation and commercialization. This Review highlights the progress, challenges and opportunities in cancer nanomedicine and discusses novel engineering approaches that capitalize on our growing understanding of tumour biology and nano-bio interactions to develop more effective nanotherapeutics for cancer patients.

Quantitating drug-target engagement in single cells in vitro and in vivo

Quantitation of drug target engagement in single cells has proven to be difficult, often leaving unanswered questions in the drug development process. We found that intracellular target engagement of unlabeled new therapeutics can be quantitated using polarized microscopy combined with competitive binding of matched fluorescent companion imaging probes. We quantitated the dynamics of target engagement of covalent BTK inhibitors, as well as reversible PARP inhibitors, in populations of single cells using a single companion imaging probe for each target. We then determined average in vivo tumor concentrations and found marked population heterogeneity following systemic delivery, revealing single cells with low target occupancy at high average target engagement in vivo.

MENA Confers Resistance to Paclitaxel in Triple-Negative Breast Cancer

Taxane therapy remains the standard of care for triple-negative breast cancer. However, high frequencies of recurrence and progression in treated patients indicate that metastatic breast cancer cells can acquire resistance to this drug. The actin regulatory protein MENA and particularly its invasive isoform, MENA^INV, are established drivers of metastasis. MENA^INV expression is significantly correlated with metastasis and poor outcome in human patients with breast cancer. We investigated whether MENA isoforms might play a role in driving resistance to chemotherapeutics. We find that both MENA and MENA^INV confer resistance to the taxane paclitaxel, but not to the widely used DNA-damaging agents doxorubicin or cisplatin. Furthermore, paclitaxel treatment does not attenuate growth of MENA^INV-driven metastatic lesions. Mechanistically, MENA isoform expression alters the ratio of dynamic and stable microtubule populations in paclitaxel-treated cells. MENA expression also increases MAPK signaling in response to paclitaxel treatment. Decreasing ERK phosphorylation by co-treatment with MEK inhibitor restored paclitaxel sensitivity by driving microtubule stabilization in MENA isoform-expressing cells. Our results reveal a novel mechanism of taxane resistance in highly metastatic breast cancer cells and identify a combination therapy to overcome such resistance. Mol Cancer Ther; 16(1); 143-55. ©2016 AACR.

Residualization Rates of Near-Infrared Dyes for the Rational Design of Molecular Imaging Agents

PURPOSE

Near-infrared (NIR) fluorescence imaging is widely used for tracking antibodies and biomolecules in vivo. Clinical and preclinical applications include intraoperative imaging, tracking therapeutics, and fluorescent labeling as a surrogate for subsequent radiolabeling. Despite their extensive use, one of the fundamental properties of NIR dyes, the residualization rate within cells following internalization, has not been systematically studied. This rate is required for the rational design of probes and proper interpretation of in vivo results.

PROCEDURES

In this brief report, we measure the cellular residualization rate of eight commonly used dyes encompassing three core structures (cyanine, boron-dipyrromethene (BODIPY), and oxazine/thiazine/carbopyronin).

RESULTS

We identify residualizing (half-life >24 h) and non-residualizing (half-life <24 h) dyes in both the far-red (~650-680 nm) and near-infrared (~740-800 nm) regions.

CONCLUSIONS

This data will allow researchers to independently and rationally select the wavelength and residualizing nature of dyes for molecular imaging agent design.

Intravital imaging reveals new ancillary mechanisms co-opted by cancer cells to drive tumor progression

Intravital imaging is providing new insights into the dynamics of tumor progression in native tissues and has started to reveal the layers of complexity found in cancer. Recent advances in intravital imaging have allowed us to look deeper into cancer behavior and to dissect the interactions between tumor cells and the ancillary host niche that promote cancer development. In this review, we provide an insight into the latest advances in cancer biology achieved by intravital imaging, focusing on recently discovered mechanisms by which tumor cells manipulate normal tissue to facilitate disease progression.