Causes and effects of heterogeneous perfusion in tumors

Identifying metabolic limitations in the tumor microenvironment

Solid tumors are characterized by dysfunctional vasculature that limits perfusion and delivery of nutrients to the tumor microenvironment. Limited perfusion coupled with the high metabolic demand of growing tumors has led to the hypothesis that many tumors experience metabolic stress driven by limited availability of nutrients such as glucose, oxygen, and amino acids in the tumor. Such metabolic stress has important implications for the biology of cells in the microenvironment, affecting both disease progression and response to therapies. Recently, techniques have been developed to identify limiting nutrients and resulting metabolic stresses in solid tumors. These techniques have greatly expanded our understanding of the metabolic limitations in tumors. This review will discuss these experimental tools and the emerging picture of metabolic limitations in tumors arising from recent studies using these approaches.

Design of a Fibroblast Activation Protein-Targeted Radiopharmaceutical Therapy with High Tumor-to-Healthy-Tissue Ratios

Because of upregulated expression on cancer-associated fibroblasts, fibroblast activation protein (FAP) has emerged as an attractive biomarker for the imaging and therapy of solid tumors. Although many FAP ligands have already been developed for radiopharmaceutical therapies (RPTs), most suffer from inadequate tumor uptake, insufficient tumor residence times, or off-target accumulation in healthy tissues, suggesting a need for further improvements. Methods: A new FAP-targeted RPT with a novel ligand (FAP8-PEG3-IP-DOTA) was designed by combining the desirable features of several previous ligand-targeted RPTs. Uptake and retention of [111In]In or [177Lu]Lu-FAP8-PEG3-IP-DOTA were assessed in KB, HT29, MDA-MB-231, and 4T1 murine tumor models by radioimaging or ex vivo biodistribution analyses. Radiotherapeutic potencies and gross toxicities were also investigated by monitoring tumor growth, body weight, and tissue damage in tumor-bearing mice. Results: FAP8-PEG3-IP-DOTA exhibited high affinity (half-maximal inhibitory concentration, 1.6 nM) and good selectivity for FAP relative to its closest homologs, prolyl oligopeptidase (half-maximal inhibitory concentration, ∼14.0 nM) and dipeptidyl peptidase-IV (half-maximal inhibitory concentration, ∼860 nM). SPECT/CT scans exhibited high retention in 2 different solid tumor models and minimal uptake in healthy tissues. Quantitative biodistribution analyses revealed tumor-to-healthy-tissue ratios of more than 5 times for all major organs, and live animal studies demonstrated 65%-93% suppression of tumor growth in all 4 models tested, with minimal or no evidence of systemic toxicity. Conclusion: We conclude that [177Lu]Lu-FAP8-PEG3-IP-DOTA constitutes a promising and safe RPT candidate for FAPα-targeted radionuclide therapy of solid tumors.

Augmentation of the EPR effect by mild hyperthermia to improve nanoparticle delivery to the tumor

The clinical translation of the nanoparticle (NP)-based anticancer therapies is still unsatisfactory due to the heterogeneity of the enhanced permeability and retention (EPR) effect. Despite the promising preclinical outcome of the pharmacological EPR enhancers, their systemic toxicity can limit their clinical application. Hyperthermia (HT) presents an efficient tool to augment the EPR by improving tumor blood flow (TBF) and vascular permeability, lowering interstitial fluid pressure (IFP), and disrupting the structure of the extracellular matrix (ECM). Furthermore, the HT-triggered intravascular release approach can overcome the EPR effect. In contrast to pharmacological approaches, HT is safe and can be focused to cancer tissues. Moreover, HT conveys direct anti-cancer effects, which improve the efficacy of the anti-cancer agents encapsulated in NPs. However, the clinical application of HT is challenging due to the heterogeneous distribution of temperature within the tumor, the length of the treatment and the complexity of monitoring.

Current clinical investigations of focused ultrasound blood-brain barrier disruption: A review

The blood-brain barrier (BBB) presents a formidable challenge in delivering therapeutic agents to the central nervous system. Ultrasound-mediated BBB disruption has emerged as a promising non-invasive technique to enhance drug delivery to the brain. This manuscript reviews fundamental principles of ultrasound-based techniques and their mechanisms of action in temporarily permeabilizing the BBB. Clinical trials employing ultrasound for BBB disruption are discussed, summarizing diverse applications ranging from the treatment of neurodegenerative diseases to targeted drug delivery for brain tumors. The review also addresses safety considerations, outlining the current understanding of potential risks and mitigation strategies associated with ultrasound exposure, including real-time monitoring and assessment of treatment efficacy. Among the large number of studies, significant successes are highlighted thus providing perspective on the future direction of the field.

Radiomics Multifactorial in Silico Model for Spatial Prediction of Glioblastoma Progression and Recurrence: A Proof-of-Concept

BACKGROUND

Radiomics-based prediction of glioblastoma spatial progression and recurrence may improve personalized strategies. However, most prototypes are based on limited monofactorial Gompertzian models of tumor growth. The present study consists of a proof of concept on the accuracy of a radiomics multifactorial in silico model in predicting short-term spatial growth and recurrence of glioblastoma.

METHODS

A radiomics-based biomathematical multifactorial in silico model was developed using magnetic resonance imaging (MRI) data from a 53-year-old patient with newly diagnosed glioblastoma of the right supramarginal gyrus. Raw and optimized models were derived from the MRI at diagnosis and matched to the preoperative MRI obtained 28 days after diagnosis to test the accuracy in predicting the short-term spatial growth of the tumor. An additional optimized model was derived from the early postoperative MRI and matched to the MRI documenting tumor recurrence to test spatial accuracy in predicting the location of recurrence. The spatial prediction accuracy of the model was reported as an average Jaccard index.

RESULTS

Optimized models yielded an average Jaccard index of 0.69 and 0.26 for short-term tumor growth and long-term recurrence site, respectively.

CONCLUSIONS

The present radiomics-based multifactorial in silico model was feasible, reliable, and accurate for short-term spatial prediction of glioblastoma progression. The predictive value for the spatial location of recurrence was still low, and refinements in the description of tissue reorganization in the peritumoral and resected areas may be critical to optimize accuracy further.

Dielectric Characterization of Ex-Vivo Breast Tissues: Differentiation of Tumor Types through Permittivity Measurements

Early analysis and diagnosis of breast tumors is essential for either quickly launching a treatment or for seeing the evolution of patients who, for instance, have already undergone chemotherapy treatment. Once tissues are excised, histological analysis is the most frequent tool used to characterize benign or malignant tumors. Dielectric microwave spectroscopy makes use of an open-ended coaxial probe in the 1-8 GHz frequency range to quickly identify the type of tumor (ductal carcinoma, lobular carcinoma, mucinous carcinoma and fibroadenoma). The experiment was undertaken with data from 70 patients who had already undergone chemotherapy treatment, which helped to electrically map the histological tissues with their electric permittivity. Thus, the variations in the permittivity of different types of tumors reveal distinctive patterns: benign tumors have permittivity values lower than 35, while malignant ones range between 40 and 60. For example, at a frequency of 2 GHz, the measured permittivity was 45.6 for ductal carcinoma, 33.1 for lobular carcinoma, 59.5 for mucinous carcinoma, and 27.6 for benign tumors. This differentiation remains consistent in a frequency range of 1 to 4.5 GHz. These results highlight the effectiveness of these measurements in the classification of breast tumors, providing a valuable tool for quick and accurate diagnosis and effective treatment.

Machine Learning Combined with Radiomics Facilitating the Personal Treatment of Malignant Liver Tumors

In the realm of managing malignant liver tumors, the convergence of radiomics and machine learning has redefined the landscape of medical practice. The field of radiomics employs advanced algorithms to extract thousands of quantitative features (including intensity, texture, and structure) from medical images. Machine learning, including its subset deep learning, aids in the comprehensive analysis and integration of these features from diverse image sources. This potent synergy enables the prediction of responses of malignant liver tumors to various treatments and outcomes. In this comprehensive review, we examine the evolution of the field of radiomics and its procedural framework. Furthermore, the applications of radiomics combined with machine learning in the context of personalized treatment for malignant liver tumors are outlined in aspects of surgical therapy and non-surgical treatments such as ablation, transarterial chemoembolization, radiotherapy, and systemic therapies. Finally, we discuss the current challenges in the amalgamation of radiomics and machine learning in the study of malignant liver tumors and explore future opportunities.

Immunotherapy Enhancement by Targeting Extracellular Tumor pH in Triple-Negative Breast Cancer Mouse Model

Triple-negative breast cancer (TNBC), as one of the most aggressive forms of breast cancer, is characterized by a poor prognosis and a very low rate of disease-free and overall survival. In recent years, immunotherapeutic approaches targeting T cell checkpoint molecules, such as cytotoxic lymphocyte antigen-4 (CTLA-4), programmed death1 (PD-1) or its ligand, programmed death ligand 1 (PD-L1), have shown great potential and have been used to treat various cancers as single therapies or in combination with other modalities. However, despite this remarkable progress, patients with TNBC have shown a low response rate to this approach, commonly developing resistance to immune checkpoint blockade, leading to treatment failure. Extracellular acidosis within the tumor microenvironment (also known as the Warburg effect) is one of the factors preventing immune cells from mounting effective responses and contributing to immunotherapy treatment failure. Therefore, reducing tumor acidity is important for increasing cancer immunotherapy effectiveness and this has yet to be realized in the TNBC environment. In this study, the oral administration of sodium bicarbonate (NaHCO3) enhanced the antitumor effect of anti-PD-L1 antibody treatment, as demonstrated by generated antitumor immunity, tumor growth inhibition and enhanced survival in 4T1-Luc breast cancer model. Here, we show that NaHCO3 increased extracellular pH (pHe) in tumor tissues in vivo, an effect that was accompanied by an increase in T cell infiltration, T cell activation and IFN-γ, IL2 and IL12p40 mRNA expression in tumor tissues, as well as an increase in T cell activation in tumor-draining lymph nodes. Interestingly, these changes were further enhanced in response to combined NaHCO3 + anti-PD-L1 therapy. In addition, the acidic extracellular conditions caused a significant increase in PD-L1 expression in vitro. Taken together, these results indicate that alkalizing therapy holds potential as a new tumor microenvironment immunomodulator and we hypothesize that NaHCO3 can enhance the antitumor effects of anti-PD-L1 breast cancer therapy. The combination of these treatments may have an exceptional impact on future TNBC immunotherapeutic approaches by providing a powerful personalized medicine paradigm. Therefore, our findings have a great translational potential for improving outcomes in TNBC patients.

Drug transport modeling in solid tumors: A computational exploration of spatial heterogeneity of biophysical properties

Inadequate uptake of therapeutic agents by tumor cells is still a major barrier in clinical cancer therapy. Mathematical modeling is a powerful tool to describe and investigate the transport phenomena involved. However, current models for interstitial flow and drug delivery in solid tumors have not yet embedded the existing heterogeneity of tumor biomechanical properties. The purpose of this study is to introduce a novel and more realistic methodology for computational models of solid tumor perfusion and drug delivery accounting for these regional heterogeneities as well as lymphatic drainage effects. Several tumor geometries were studied using an advanced computational fluid dynamics (CFD) modeling approach of intratumor interstitial fluid flow and drug transport. Hereby, the following novelties were implemented: (i) the heterogeneity of tumor-specific hydraulic conductivity and capillary permeability; (ii) the effect of lymphatic drainage on interstitial fluid flow and drug penetration. Tumor size and shape both have a crucial role on the interstitial fluid flow regime as well as drug transport illustrating a direct correlation with interstitial fluid pressure (IFP) and an inverse correlation with drug penetration, except for large tumors having a diameter larger than 50 mm. The results also suggest that the interstitial fluid flow and drug penetration in small tumors depend on tumor shape. A parameter study on the necrotic core size illustrated that the core effect (i.e. fluid flow and drug penetration alteration) was only profound in small tumors. Interestingly, the impact of a necrotic core on drug penetration differs depending on the tumor shape from having no effect in ideally spherical tumors to a clear effect in elliptical tumors with a necrotic core. A realistic presence of lymphatic vessels only slightly affected tumor perfusion, having no substantial effect on drug delivery. In conclusion, our findings illustrated that our novel parametric CFD modeling strategy in combination with accurate profiling of heterogeneous tumor biophysical properties can provide a powerful tool for better insights into tumor perfusion and drug transport, enabling effective therapy planning.

Perspectives for Improving the Tumor Targeting of Nanomedicine via the EPR Effect in Clinical Tumors

Over the past few decades, the enhanced permeability and retention (EPR) effect of nanomedicine has been a crucial phenomenon in targeted cancer therapy. Specifically, understanding the EPR effect has been a significant aspect of delivering anticancer agents efficiently to targeted tumors. Although the therapeutic effect has been demonstrated in experimental models using mouse xenografts, the clinical translation of the EPR effect of nanomedicine faces several challenges due to dense extracellular matrix (ECM), high interstitial fluid pressure (IFP) levels, and other factors that arise from tumor heterogeneity and complexity. Therefore, understanding the mechanism of the EPR effect of nanomedicine in clinics is essential to overcome the hurdles of the clinical translation of nanomedicine. This paper introduces the basic mechanism of the EPR effect of nanomedicine, the recently discussed challenges of the EPR effect of nanomedicine, and various strategies of recent nanomedicine to overcome the limitations expected from the patients' tumor microenvironments.

Breaking the niche: multidimensional nanotherapeutics for tumor microenvironment modulation

Most of the current antitumor therapeutics were developed targeting the cancer cells only. Unfortunately, in the majority of tumors, this single-dimensional therapy is found to be ineffective. Advanced research has shown that cancer is a multicellular disorder. The tumor microenvironment (TME), which is made by a complex network of the bulk tumor cells and other supporting cells, plays a crucial role in tumor progression. Understanding the importance of the TME in tumor growth, different treatment modalities have been developed targeting these supporting cells. Recent clinical results suggest that simultaneously targeting multiple components of the tumor ecosystem with drug combinations can be highly effective. This type of "multidimensional" therapy has a high potential for cancer treatment. However, tumor-specific delivery of such multi-drug combinations remains a challenge. Nanomedicine could be utilized for the tumor-targeted delivery of such multidimensional therapeutics. In this review, we first give a brief overview of the major components of TME. We then highlight the latest developments in nanoparticle-based combination therapies, where one drug targets cancer cells and other drug targets tumor-supporting components in the TME for a synergistic effect. We include the latest preclinical and clinical studies and discuss innovative nanoparticle-mediated targeting strategies.

Theranostic Cancer Treatment Using Lentinan-Coated Selenium Nanoparticles and Label-Free CEST MRI

Selenium nanoparticle (SeNP)-based nanotherapeutics have become an emerging cancer therapy, while effective drug delivery remains a technical hurdle. A theranostic approach, through which imaging companions are integrated with SeNPs, will allow image-guided drug delivery and, therefore, is highly desirable. Traditional methods require the chemical conjugation of imaging agents to the surface of nanoparticles, which may impede the later clinical translation. In this study, we developed a label-free strategy in which lentinan-functionalized SeNPs (LNT-SeNPs) are detected using MRI by the hydroxyl protons carried on LNT molecules. The in vitro phantom study showed that LNT and LNT-SeNPs have a strong CEST signal at 1.0 ppm apart from the water resonance, suggesting an in vivo detectability in the µM concentration range. Demonstrated on CT26 colon tumor cells, LNT-SeNPs exert a strong anticancer effect (IC50 = 4.8 μM), prominently attributed to the ability to generate intracellular reactive oxygen species. However, when testing in a mouse model of CT26 tumors, administration of LNT-SeNPs alone was found unable to deliver sufficient drugs to the tumor, leading to poor treatment responses. To improve the drug delivery, we co-injected LNT-SeNPs and TNF-α, a previously reported drug that could effectively damage the endothelial cells in the tumor vasculature, thereby increasing drug delivery to the tumor. Our results revealed a 75% increase in the intratumoral CEST MRI signal, indicating a markedly increased delivery efficiency of LNT-SeNPs when combined with TNF-α. The combination therapy also resulted in a significantly enhanced treatment outcome, as revealed by the tumor growth study. Taken together, our study demonstrates the first label-free, SeNP-based theranostic system, in which LNT was used for both functional surface coating and CEST MRI signal generating. Such a theranostic LNT-SeNP system is advantageous because it requires chemical labeling and, therefore, has high biocompatibility and low translatable barriers.

Combining Mechanisms of Growth Arrest in Solid Tumours: A Mathematical Investigation

The processes underpinning solid tumour growth involve the interactions between various healthy and tumour tissue components and the vasculature, and can be affected in different ways by cancer treatment. In particular, the growth-limiting mechanisms at play may influence tumour responses to treatment. In this paper, we propose a simple ordinary differential equation model of solid tumour growth to investigate how tumour-specific mechanisms of growth arrest may affect tumour response to different combination cancer therapies. We consider the interactions of tumour cells with the physical space in which they proliferate and a nutrient supplied by the tumour vasculature, with the aim of representing two distinct growth arrest mechanisms. More specifically, we wish to consider growth arrest due to (1) nutrient deficiency, which corresponds to balancing cell proliferation and death rates, and (2) competition for space, which corresponds to cessation of proliferation without cell death. We perform numerical simulations of the model and a steady-state analysis to determine the possible tumour growth scenarios described by the model. We find that there are three distinct growth regimes: the nutrient- and spatially limited regimes and a bi-stable regime, in which both growth arrest mechanisms are simultaneously active. Thus, the proposed model has the features required to investigate and distinguish tumour responses to different cancer treatments.

Measurement of biological washout rates depending on tumor vascular status in 15O in-beam rat-PET

Objective. The biological washout of positron emitters should be modeled and corrected in order to achieve quantitative dose range verification in charged particle therapy based on positron emission tomography (PET). This biological washout effect is affected by physiological environmental conditions such as blood perfusion and metabolism, but the correlation to tumour pathology has not been studied yet. Approach. The aim of this study was to investigate the dependence of the biological washout rate on tumour vascular status in rat irradiation. Two types of tumour vascularity conditions, perfused and hypoxic, were modelled with nude rats. The rats were irradiated by a radioactive 15O ion beam and time activity curves were acquired by dynamic in-beam PET measurement. Tumour tissue sections were obtained to observe the histology as well. The biological washout rate was derived using a single-compartment model with two decay components (medium decay, k 2m and slow decay, k 2s ). Main results. All k 2m values in the vascular perfused tumour tissue were higher than the values of the normal tissue. All k 2m values in the hypoxic tumour tissue were much lower than the values of the vascular perfused tumour tissue and slightly lower than the values of the normal tissue. Significance. The dependency of the biological washout on the tumour vasculature conditions was experimentally shown.

Target Definition in MR-Guided Adaptive Radiotherapy for Head and Neck Cancer

In recent years, MRI-guided radiotherapy (MRgRT) has taken an increasingly important position in image-guided radiotherapy (IGRT). Magnetic resonance imaging (MRI) offers superior soft tissue contrast in anatomical imaging compared to computed tomography (CT), but also provides functional and dynamic information with selected sequences. Due to these benefits, in current clinical practice, MRI is already used for target delineation and response assessment in patients with head and neck squamous cell carcinoma (HNSCC). Because of the close proximity of target areas and radiosensitive organs at risk (OARs) during HNSCC treatment, MRgRT could provide a more accurate treatment in which OARs receive less radiation dose. With the introduction of several new radiotherapy techniques (i.e., adaptive MRgRT, proton therapy, adaptive cone beam computed tomography (CBCT) RT, (daily) adaptive radiotherapy ensures radiation dose is accurately delivered to the target areas. With the integration of a daily adaptive workflow, interfraction changes have become visible, which allows regular and fast adaptation of target areas. In proton therapy, adaptation is even more important in order to obtain high quality dosimetry, due to its susceptibility for density differences in relation to the range uncertainty of the protons. The question is which adaptations during radiotherapy treatment are oncology safe and at the same time provide better sparing of OARs. For an optimal use of all these new tools there is an urgent need for an update of the target definitions in case of adaptive treatment for HNSCC. This review will provide current state of evidence regarding adaptive target definition using MR during radiotherapy for HNSCC. Additionally, future perspectives for adaptive MR-guided radiotherapy will be discussed.

Functional implications of microvascular heterogeneity for oxygen uptake and utilization

In the vascular system, an extensive network structure provides convective and diffusive transport of oxygen to tissue. In the microcirculation, parameters describing network structure, blood flow, and oxygen transport are highly heterogeneous. This heterogeneity can strongly affect oxygen supply and organ function, including reduced oxygen uptake in the lung and decreased oxygen delivery to tissue. The causes of heterogeneity can be classified as extrinsic or intrinsic. Extrinsic heterogeneity refers to variations in oxygen demand in the systemic circulation or oxygen supply in the lungs. Intrinsic heterogeneity refers to structural heterogeneity due to stochastic growth of blood vessels and variability in flow pathways due to geometric constraints, and resulting variations in blood flow and hematocrit. Mechanisms have evolved to compensate for heterogeneity and thereby improve oxygen uptake in the lung and delivery to tissue. These mechanisms, which involve long-term structural adaptation and short-term flow regulation, depend on upstream responses conducted along vessel walls, and work to redistribute flow and maintain blood and tissue oxygenation. Mathematically, the variance of a functional quantity such as oxygen delivery that depends on two or more heterogeneous variables can be reduced if one of the underlying variables is controlled by an appropriate compensatory mechanism. Ineffective regulatory mechanisms can result in poor oxygen delivery even in the presence of adequate overall tissue perfusion. Restoration of endothelial function, and specifically conducted responses, should be considered when addressing tissue hypoxemia and organ failure in clinical settings.

ECM Depletion Is Required to Improve the Intratumoral Uptake of Iron Oxide Nanoparticles in Poorly Perfused Hepatocellular Carcinoma

Improving tumor access for drug delivery is challenging, particularly in poorly perfused tumors. The availability of functional tumor blood vessels for systemic access is vital to allow drugs or imaging agents to accumulate in the tumor parenchyma. We subjected mice engineered to develop hepatocellular carcinoma (HCC), to treatment with tumor necrosis factor alpha (TNFα) conjugated to a CSG peptide (CSGRRSSKC). CSG binds to the laminin-nidogen-1 complex of the extracellular matrix (ECM) in HCC. When produced as a recombinant fusion protein, the TNFα-CSG functions as an ECM depletion agent via an immune-mediated mechanism to improve tumor perfusion. Tumor perfusion in HCC was dramatically improved after daily intravenous (i.v.) injection of 5 µg TNFα-CSG for five consecutive days. Following treatment, we assessed the tumor accessibility to accumulate an imaging agent, superparamagnetic iron-oxide nanoparticles (IO-NP). Here, we compared the passive delivery of an i.v. dose of IO-NP in HCC following ECM depletion after TNFα-CSG treatment, to the intratumoral accumulation of a comparable dose of CSG-targeted IO-NP in HCC with intact ECM. Magnetic resonance imaging (MRI) T₂-weighted scans and T₂ relaxation times indicate that when the tumor ECM is intact, HCC was resistant to the intratumoral uptake of IO-NP, even when the particles were tagged with CSG peptide. In contrast, pre-treatment with TNFα-CSG resulted in the highest IO-NP accumulation in tumors. These findings suggest poorly perfused HCC may be resistant to molecular-targeted imaging agents including CSG-IO-NP. We demonstrate that specific ECM depletion using TNFα-CSG improves nanoparticle delivery into poorly perfused tumors such as HCC.

Assessing Tumour Haemodynamic Heterogeneity and Response to Choline Kinase Inhibition Using Clustered Dynamic Contrast Enhanced MRI Parameters in Rodent Models of Glioblastoma

To investigate the utility of DCE-MRI derived pharmacokinetic parameters in evaluating tumour haemodynamic heterogeneity and treatment response in rodent models of glioblastoma, imaging was performed on intracranial F98 and GL261 glioblastoma bearing rodents. Clustering of the DCE-MRI-based parametric maps (using Tofts, extended Tofts, shutter speed, two-compartment, and the second generation shutter speed models) was performed using a hierarchical clustering algorithm, resulting in areas with poor fit (reflecting necrosis), low, medium, and high valued pixels representing parameters Ktrans, ve, Kep, vp, τi and Fp. There was a significant increase in the number of necrotic pixels with increasing tumour volume and a significant correlation between ve and tumour volume suggesting increased extracellular volume in larger tumours. In terms of therapeutic response in F98 rat GBMs, a sustained decrease in permeability and perfusion and a reduced cell density was observed during treatment with JAS239 based on Ktrans, Fp and ve as compared to control animals. No significant differences in these parameters were found for the GL261 tumour, indicating that this model may be less sensitive to JAS239 treatment regarding changes in vascular parameters. This study demonstrates that region-based clustered pharmacokinetic parameters derived from DCE-MRI may be useful in assessing tumour haemodynamic heterogeneity with the potential for assessing therapeutic response.

Multifaceted Interplay between Hormones, Growth Factors and Hypoxia in the Tumor Microenvironment

Hormones and growth factors (GFs) are signaling molecules implicated in the regulation of a variety of cellular processes. They play important roles in both healthy and tumor cells, where they function by binding to specific receptors on target cells and activating downstream signaling cascades. The stages of tumor progression are influenced by hormones and GF signaling. Hypoxia, a hallmark of cancer progression, contributes to tumor plasticity and heterogeneity. Most solid tumors contain a hypoxic core due to rapid cellular proliferation that outgrows the blood supply. In these circumstances, hypoxia-inducible factors (HIFs) play a central role in the adaptation of tumor cells to their new environment, dramatically reshaping their transcriptional profile. HIF signaling is modulated by a variety of factors including hormones and GFs, which activate signaling pathways that enhance tumor growth and metastatic potential and impair responses to therapy. In this review, we summarize the role of hormones and GFs during cancer onset and progression with a particular focus on hypoxia and the interplay with HIF proteins. We also discuss how hypoxia influences the efficacy of cancer immunotherapy, considering that a hypoxic environment may act as a determinant of the immune-excluded phenotype and a major hindrance to the success of adoptive cell therapies.

Bacteria-Assisted Transport of Nanomaterials to Improve Drug Delivery in Cancer Therapy

Currently, the design of nanomaterials for the treatment of different pathologies is presenting a major impact on biomedical research. Thanks to this, nanoparticles represent a successful strategy for the delivery of high amounts of drugs for the treatment of cancer. Different nanosystems have been designed to combat this pathology. However, the poor penetration of these nanomaterials into the tumor tissue prevents the drug from entering the inner regions of the tumor. Some bacterial strains have self-propulsion and guiding capacity thanks to their flagella. They also have a preference to accumulate in certain tumor regions due to the presence of different chemo-attractants factors. Bioconjugation reactions allow the binding of nanoparticles in living systems, such as cells or bacteria, in a simple way. Therefore, bacteria are being used as a transport vehicle for nanoparticles, facilitating their penetration and the subsequent release of the drug inside the tumor. This review would summarize the literature on the anchoring methods of diverse nanosystems in bacteria and, interestingly, their advantages and possible applications in cancer therapy.

Photoplethysmography for demarcation of cutaneous squamous cell carcinoma

A video processing algorithm designed to identify cancer suspicious skin areas is presented here. It is based on video recordings of squamous cell carcinoma in the skin. Squamous cell carcinoma is a common malignancy, normally treated by surgical removal. The surgeon should always balance sufficient tissue removal against unnecessary mutilation, and therefore methods for distinction of cancer boundaries are wanted. Squamous cell carcinoma has angiogenesis and increased blood supply. Remote photoplethysmography is an evolving technique for analysis of signal variations in video recordings in order to extract vital signs such as pulsation. We hypothesize that the remote photoplethysmography signal inside the area of a squamous cell carcinoma is significantly different from the surrounding healthy skin. Based on high speed video recordings of 13 patients with squamous cell carcinoma, we have examined temporal signal differences in cancer areas versus healthy skin areas. A significant difference in temporal signal changes between cancer areas and healthy areas was found. Our video processing algorithm showed promising results encouraging further investigation to clarify how detailed distinctions can be made.

The safe and effective intraperitoneal chemotherapy with cathepsin B-specific doxorubicin prodrug nanoparticles in ovarian cancer with peritoneal carcinomatosis

Intraperitoneal (IP) chemotherapy has shown promising efficacy in ovarian cancer with peritoneal carcinomatosis (PC), but in vivo rapid clearance and severe toxicity of free anticancer drugs hinder the effective treatment. Herein, we propose the safe and effective IP chemotherapy with cathepsin B-specific doxorubicin prodrug nanoparticles (PNPs) in ovarian cancer with PC. The PNPs are prepared by self-assembling cathepsin B-specific cleavable peptide (FRRG) and doxorubicin (DOX) conjugates, which are further formulated with pluronic F68. The PNPs exhibit stable spherical structure and cytotoxic DOX is specifically released from PNPs via sequential enzymatic degradation by cathepsin B and intracellular proteases. The PNPs induce cytotoxicity in cathepsin B-overexpressing ovarian (SKOV-3 and HeyA8) and colon (MC38 and CT26) cancer cells, but not in cathepsin B-deficient normal cells in cultured condition. With enhanced cancer-specificity and in vivo residence time, IP injected PNPs efficiently accumulate within PC through two targeting mechanisms of direct penetration (circulation independent) and systemic blood vessel-associated accumulation (circulation dependent). As a result, IP chemotherapy with PNPs efficiently inhibit tumor progression with minimal side effects in peritoneal human ovarian tumor-bearing xenograft (POX) and patient derived xenograft (PDX) models. These results demonstrate that PNPs effectively inhibit progression of ovarian cancer with peritoneal carcinomatosis with minimal local and systemic toxicities by high cancer-specificity and favorable in vivo PK/PD profiles enhancing PC accumulation.

Enhanced Detection of Desmoplasia by Targeted Delivery of Iron Oxide Nanoparticles to the Tumour-Specific Extracellular Matrix

Diagnostic imaging of aggressive cancer with a high stroma content may benefit from the use of imaging contrast agents targeted with peptides that have high binding affinity to the extracellular matrix (ECM). In this study, we report the use of superparamagnetic iron-oxide nanoparticles (IO-NP) conjugated to a nonapeptide, CSGRRSSKC (CSG), which specifically binds to the laminin-nidogen-1 complex in tumours. We show that CSG-IO-NP accumulate in tumours, predominantly in the tumour ECM, following intravenous injection into a murine model of pancreatic neuroendocrine tumour (PNET). In contrast, a control untargeted IO-NP consistently show poor tumour uptake, and IO-NP conjugated to a pentapeptide, CREKA that bind fibrin clots in blood vessels show restricted uptake in the angiogenic vessels of the tumours. CSG-IO-NP show three-fold higher intratumoral accumulation compared to CREKA-IO-NP. Magnetic resonance imaging (MRI) T₂-weighted scans and T₂ relaxation times indicate significant uptake of CSG-IO-NP irrespective of tumour size, whereas the uptake of CREKA-IO-NP is only consistent in small tumours of less than 3 mm in diameter. Larger tumours with significantly reduced tumour blood vessels show a lack of CREKA-IO-NP uptake. Our data suggest CSG-IO-NP are particularly useful for detecting stroma in early and advanced solid tumours.

Tumour-on-chip microfluidic platform for assessment of drug pharmacokinetics and treatment response

Microphysiological in vitro systems are platforms for preclinical evaluation of drug effects and significant advances have been made in recent years. However, existing microfluidic devices are not yet able to deliver compounds to cell models in a way that reproduces the real physiological drug exposure. Here, we introduce a novel tumour-on-chip microfluidic system that mimics the pharmacokinetic profile of compounds on 3D tumour spheroids to evaluate their response to the treatments. We used this platform to test the response of SW620 colorectal cancer spheroids to irinotecan (SN38) alone and in combination with the ATM inhibitor AZD0156, using concentrations mimicking mouse plasma exposure profiles of both agents. We explored spheroid volume and viability as a measure of cancer cells response and changes in mechanistically relevant pharmacodynamic biomarkers (γH2AX, cleaved-caspase 3 and Ki67). We demonstrate here that our microfluidic tumour-on-chip platform can successfully predict the efficacy from in vivo studies and therefore represents an innovative tool to guide drug dose and schedules for optimal efficacy and pharmacodynamic assessment, while reducing the need for animal studies.

Petreus et al. describe a platform combining 3D tumour-on-chip technology and pump driven microfluidics to study drug effects at physiological exposures preclinically. They test colorectal cancer spheroids with combinations of two drugs and show that it can successfully predict efficacy in vivo, thereby providing a valuable tool for drug response and pharmacodynamic assessment and reducing the need for animal studies.

Anti-carcinogenic effects of exercise-conditioned human serum: evidence, relevance and opportunities

Regular physical activity reduces the risk of several site-specific cancers in humans and suppresses tumour growth in animal models. The mechanisms through which exercise reduces tumour growth remain incompletely understood, but an intriguing and accumulating body of evidence suggests that the incubation of cancer cells with post-exercise serum can have powerful effects on key hallmarks of cancer cell behaviour in vitro. This suggests that exercise can impact tumour biology through direct changes in circulating proteins, RNA molecules and metabolites. Here, we provide a comprehensive narrative overview of what is known about the effects of exercise-conditioned sera on in vitro cancer cell behaviour. In doing so, we consider the key limitations of the current body of literature, both from the perspective of exercise physiology and cancer biology, and we discuss the potential in vivo physiological relevance of these findings. We propose key opportunities for future research in an area that has the potential to identify key anti-oncogenic protein targets and optimise physical activity recommendations for cancer prevention, treatment and survivorship.

Biologically-Based Mathematical Modeling of Tumor Vasculature and Angiogenesis via Time-Resolved Imaging Data

Tumor-associated vasculature is responsible for the delivery of nutrients, removal of waste, and allowing growth beyond 2-3 mm3. Additionally, the vascular network, which is changing in both space and time, fundamentally influences tumor response to both systemic and radiation therapy. Thus, a robust understanding of vascular dynamics is necessary to accurately predict tumor growth, as well as establish optimal treatment protocols to achieve optimal tumor control. Such a goal requires the intimate integration of both theory and experiment. Quantitative and time-resolved imaging methods have emerged as technologies able to visualize and characterize tumor vascular properties before and during therapy at the tissue and cell scale. Parallel to, but separate from those developments, mathematical modeling techniques have been developed to enable in silico investigations into theoretical tumor and vascular dynamics. In particular, recent efforts have sought to integrate both theory and experiment to enable data-driven mathematical modeling. Such mathematical models are calibrated by data obtained from individual tumor-vascular systems to predict future vascular growth, delivery of systemic agents, and response to radiotherapy. In this review, we discuss experimental techniques for visualizing and quantifying vascular dynamics including magnetic resonance imaging, microfluidic devices, and confocal microscopy. We then focus on the integration of these experimental measures with biologically based mathematical models to generate testable predictions.

Hyperpolarized Metabolic MRI-Acquisition, Reconstruction, and Analysis Methods

Hyperpolarized metabolic MRI with 13C-labeled agents has emerged as a powerful technique for in vivo assessments of real-time metabolism that can be used across scales of cells, tissue slices, animal models, and human subjects. Hyperpolarized contrast agents have unique properties compared to conventional MRI scanning and MRI contrast agents that require specialized imaging methods. Hyperpolarized contrast agents have a limited amount of available signal, irreversible decay back to thermal equilibrium, bolus injection and perfusion kinetics, cellular uptake and metabolic conversion kinetics, and frequency shifts between metabolites. This article describes state-of-the-art methods for hyperpolarized metabolic MRI, summarizing data acquisition, reconstruction, and analysis methods in order to guide the design and execution of studies.

Long Distance From Microvessel to Cancer Cell Predicts Poor Prognosis in Non-Small Cell Lung Cancer Patients

Background

Blood supply, which is crucial for nutrition and drug delivery, was determined by microvessel density as well as the diffusion distance between vessels and cancer cells. Therefore, we evaluated the distance from microvessels to cancer cells (D_mvcc) and its role in the prognosis of non-small cell lung cancer (NSCLC) patients.

Methods

Patients with primary NSCLC were retrospectively analyzed. The tumor samples were immunochemically stained with CD31 to visualize the microvessels. The D_mvcc was defined as the mean distance from each microvessel to its nearest cancer cell in the "hot-spot" of an individual patient. The patients were stratified into short- and long-distance groups using five strategies, including dichotomy by the median value, optimal cutoff, trichotomy, quartation and per-10 µm increase. The correlation between the D_mvcc and survival was evaluated by using univariate and multivariate analyses with various D_mvcc strategies.

Results

In total, 100 patients were analyzed. The median value of D_mvcc was 13.1 μm (ranged, 1.6 to 269.7 μm; mean value, 24.4 ± 33.5 μm). The optimal cutoff value of D_mvcc for predicting survival outcome was 20 μm. D_mvcc was significantly related to overall survival (OS) with all the five categories (p = 0.001-0.000004) and progression-free survival (PFS) categorized by optimal cutoff value (p = 0.024), trichotomy (p = 0.041) and per-10 µm increase (p = 0.040) after adjusting for other factors. Patients with longer D_mvcc (≥20 μm) were observed to have poor survival outcomes (OS: HR = 13.5, 95CI: 4.42-41.18, p = 0.000005; PFS: 3.26, 95CI: 1.56-6.81, p = 0.002). A high D_mvcc per-10 µm was associated with a significantly increased risk of cancer-related death and progression by 98% (p = 0.0001) and 30% (p = 0.044), respectively.

Conclusion

The NSCLC tissues had varying distances from microvessels to cancer cells, and long distances were strongly associated with poor survival.

Quantification of Structural Heterogeneity Using Fractal Analysis of Contrast-Enhanced CT Image to Predict Survival in Gastric Cancer Patients

BACKGROUND

Malignant tumor essentially implies structural heterogeneity. Fractal analysis of medical imaging has a potential to quantify this structural heterogeneity in the tumor AIMS: The purpose of this study is to quantify this structural abnormality in the tumor applying fractal analysis to contrast-enhanced computed tomography (CE-CT) image and to evaluate its biomarker value for predicting survival of surgically treated gastric cancer patients.

METHODS

A total of 108 gastric cancer patients (77 men and 31 women; mean age: 69.1 years), who received curative surgery without any neoadjuvant therapy, were retrospectively investigated. Portal-phase CE-CT images were analyzed with use of a plug-in tool for ImageJ (NIH, Bethesda, USA), and the fractal dimension (FD) in the tumor was calculated using a differential box-counting method to quantify structural heterogeneity in the tumor. Tumor FD was compared with clinicopathologic features and disease-specific survival (DSS).

RESULTS

High FD value of the tumor significantly associated with high T stage and high pathological stage (P = 0.009, 0.007, respectively). In Kaplan-Meier analysis, patients with higher FD tumors (FD > 0.9746) showed a significantly worse DSS (P = 0.009, log rank). Multivariate analysis demonstrated that tumor FD, T stage, and N stage were independent prognostic factors for DSS. In subset analysis of lymph-node positive gastric cancers, only tumor FD was an independent prognostic factor for DSS.

CONCLUSION

CT fractal analysis can be a useful biomarker for gastric cancer patients, reflecting survival and clinicopathologic features.

Anti-carcinogenic effects of exercise-conditioned human serum: evidence, relevance and opportunities

Regular physical activity reduces the risk of several site-specific cancers in humans and suppresses tumour growth in animal models. The mechanisms through which exercise reduces tumour growth remain incompletely understood, but an intriguing and accumulating body of evidence suggests that the incubation of cancer cells with post-exercise serum can have powerful effects on key hallmarks of cancer cell behaviour in vitro. This suggests that exercise can impact tumour biology through direct changes in circulating proteins, RNA molecules and metabolites. Here, we provide a comprehensive narrative overview of what is known about the effects of exercise-conditioned sera on in vitro cancer cell behaviour. In doing so, we consider the key limitations of the current body of literature, both from the perspective of exercise physiology and cancer biology, and we discuss the potential in vivo physiological relevance of these findings. We propose key opportunities for future research in an area that has the potential to identify key anti-oncogenic protein targets and optimise physical activity recommendations for cancer prevention, treatment and survivorship.

Recent Advances in Preclinical Research Using PAMAM Dendrimers for Cancer Gene Therapy

Carriers of genetic material are divided into vectors of viral and non-viral origin. Viral carriers are already successfully used in experimental gene therapies, but despite advantages such as their high transfection efficiency and the wide knowledge of their practical potential, the remaining disadvantages, namely, their low capacity and complex manufacturing process, based on biological systems, are major limitations prior to their broad implementation in the clinical setting. The application of non-viral carriers in gene therapy is one of the available approaches. Poly(amidoamine) (PAMAM) dendrimers are repetitively branched, three-dimensional molecules, made of amide and amine subunits, possessing unique physiochemical properties. Surface and internal modifications improve their physicochemical properties, enabling the increase in cellular specificity and transfection efficiency and a reduction in cytotoxicity toward healthy cells. During the last 10 years of research on PAMAM dendrimers, three modification strategies have commonly been used: (1) surface modification with functional groups; (2) hybrid vector formation; (3) creation of supramolecular self-assemblies. This review describes and summarizes recent studies exploring the development of PAMAM dendrimers in anticancer gene therapies, evaluating the advantages and disadvantages of the modification approaches and the nanomedicine regulatory issues preventing their translation into the clinical setting, and highlighting important areas for further development and possible steps that seem promising in terms of development of PAMAM as a carrier of genetic material.

The Biological Meaning of Radiomic Features

An earlier incorrect version appeared online. This article was corrected on February 10, 2021.

Heterogeneity analysis of MRI T2 maps for measurement of early tumor response to radiotherapy

External beam radiotherapy (XRT) is a widely used cancer treatment, yet responses vary dramatically among patients. These differences are not accounted for in clinical practice, partly due to a lack of sensitive early response biomarkers. We hypothesize that quantitative magnetic resonance imaging (MRI) measures reflecting tumor heterogeneity can provide a sensitive and robust biomarker of early XRT response. MRI T2 mapping was performed every 72 hours following 10 Gy dose XRT in two models of pancreatic cancer propagated in the hind limb of mice. Interquartile range (IQR) of tumor T2 was presented as a potential biomarker of radiotherapy response compared with tumor growth kinetics, and biological validation was performed through quantitative histology analysis. Quantification of tumor T2 IQR showed sensitivity for detection of XRT-induced tumor changes 72 hours after treatment, outperforming T2-weighted and diffusion-weighted MRI, with very good robustness. Histological comparison revealed that T2 IQR provides a measure of spatial heterogeneity in tumor cell density, related to radiation-induced necrosis. Early IQR changes were found to correlate to subsequent tumor volume changes, indicating promise for treatment response prediction. Our preclinical findings indicate that spatial heterogeneity analysis of T2 MRI can provide a translatable method for early radiotherapy response assessment. We propose that the method may in future be applied for personalization of radiotherapy through adaptive treatment paradigms.

Adaptive Mechanisms of Tumor Therapy Resistance Driven by Tumor Microenvironment

Cancer is a disease which frequently has a poor prognosis. Although multiple therapeutic strategies have been developed for various cancers, including chemotherapy, radiotherapy, and immunotherapy, resistance to these treatments frequently impedes the clinical outcomes. Besides the active resistance driven by genetic and epigenetic alterations in tumor cells, the tumor microenvironment (TME) has also been reported to be a crucial regulator in tumorigenesis, progression, and resistance. Here, we propose that the adaptive mechanisms of tumor resistance are closely connected with the TME rather than depending on non-cell-autonomous changes in response to clinical treatment. Although the comprehensive understanding of adaptive mechanisms driven by the TME need further investigation to fully elucidate the mechanisms of tumor therapeutic resistance, many clinical treatments targeting the TME have been successful. In this review, we report on recent advances concerning the molecular events and important factors involved in the TME, particularly focusing on the contributions of the TME to adaptive resistance, and provide insights into potential therapeutic methods or translational medicine targeting the TME to overcome resistance to therapy in clinical treatment.

Glucose-limiting conditions induce an invasive population of MDA-MB-231 breast cancer cells with increased connexin 43 expression and membrane localization

Gap junctional intercellular communication (GJIC) is a homeostatic process mediated by membrane channels composed of a protein family known as connexins. Alterations to channel activity can modulate suppression or facilitation of cancer progression. These varying roles are influenced by the cancer cell genetic profile and the context-dependent mechanisms of a dynamic extracellular environment that encompasses fluctuations to nutrient availability. To better explore the effects of altered cellular metabolism on GJIC in breast cancer, we generated a derivative of the triple-negative breast cancer cell line MDA-MB-231 optimized for growth in low-glucose. Reduced availability of glucose is commonly encountered during tumor development and leads to metabolic reprogramming in cancer cells. MDA-MB-231 low-glucose adapted cells exhibited a larger size with improved cell–cell contact and upregulation of cadherin-11. Additionally, increased protein levels of connexin 43 and greater plasma membrane localization were observed with a corresponding improvement in GJIC activity compared to the parental cell line. Since GJIC has been shown to affect cellular invasion in multiple cancer cell types, we evaluated the invasive qualities of these cells using multiple three-dimensional Matrigel growth models. Results of these experiments demonstrated a significantly more invasive phenotype. Moreover, a decrease in invasion was noted when GJIC was inhibited. Our results indicate a potential response of triple-negative breast cancer cells to reduced glucose availability that results in changes to GJIC and invasiveness. Delineation of this relationship may help elucidate mechanisms by which altered cancer cell metabolism affects GJIC and how cancer cells respond to nutrient availability in this regard.

Endothelial YAP/TAZ Signaling in Angiogenesis and Tumor Vasculature

Solid tumors are dependent on vascularization for their growth. The hypoxic, stiff, and pro-angiogenic tumor microenvironment induces angiogenesis, giving rise to an immature, proliferative, and permeable vasculature. The tumor vessels promote tumor metastasis and complicate delivery of anti-cancer therapies. In many types of tumors, YAP/TAZ activation is correlated with increased levels of angiogenesis. In addition, endothelial YAP/TAZ activation is important for the formation of new blood and lymphatic vessels during development. Oncogenic activation of YAP/TAZ in tumor cell growth and invasion has been studied in great detail, however the role of YAP/TAZ within the tumor endothelium remains insufficiently understood, which complicates therapeutic strategies aimed at targeting YAP/TAZ in cancer. Here, we overview the upstream signals from the tumor microenvironment that control endothelial YAP/TAZ activation and explore the role of their downstream targets in driving tumor angiogenesis. We further discuss the potential for anti-cancer treatments and vascular normalization strategies to improve tumor therapies.

Engineered nanomedicines for tumor vasculature blockade therapy

Tumor vasculature blockade therapy (TVBT), including angiogenesis inhibition, vascular disruption, and vascular infarction, provides a promising treatment modality for solid tumors. However, low selectivity, drug resistance, and possible severe side effects have limited the clinical transformation of TVBT. Engineered nanoparticles offer potential solutions, including prolonged circulation time, targeted transportation, and controlled release of TVBT agents. Moreover, engineered nanomedicines provide a promising combination platform of TVBT with chemotherapy, radiotherapy, photodynamic therapy, photothermal therapy, ultrasound therapy, and gene therapy. In this article, we offer a comprehensive summary of the current progress of engineered nanomedicines for TVBT and also discuss current deficiencies and future directions for TVBT development. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Quantitative prediction of the extent of pelvic tumour ablation by magnetic resonance-guided high intensity focused ultrasound

BACKGROUND

Patient suitability for magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) therapy of pelvic tumors is currently assessed by visual estimation of the proportion of tumor that can be reached by the device's focus (coverage). Since it is important to assess whether enough energy reaches the tumor to achieve ablation, a methodology for estimating the proportion of the tumor that can be ablated (treatability) was developed. Predicted treatability was compared against clinically achieved thermal ablation.

METHODS

MR Dixon sequence images of five patients with recurrent gynecological tumors were acquired during their treatment. Acousto-thermal simulations were performed using k-Wave for three exposure points (the deepest and shallowest reachable focal points within the tumor, identified from tumor coverage analysis, and a point halfway in-between) per patient. Interpolation between the resulting simulated ablated tissue volumes was used to estimate the maximum treatable depth and hence, tumor treatability. Predicted treatability was compared both to predicted tumor coverage and to the clinically treated tumor volume. The intended and simulated volumes and positions of ablated tissues were compared.

RESULTS

Predicted treatability was less than coverage by 52% (range: 31-78%) of the tumor volume. Predicted and clinical treatability differed by 9% (range: 1-25%) of tumor volume. Ablated tissue volume and position varied with beam path length through tissue.

CONCLUSION

Tumor coverage overestimated patient suitability for MRgHIFU therapy. Employing patient-specific simulations improved treatability assessment. Patient treatability assessment using simulations is feasible.

In Vivo Albumin-Binding of a C-Functionalized Cyclam Platform for 64 Cu-PET/CT Imaging in Breast Cancer Model

An improved glucose-chelator-albumin bioconjugate (GluCAB) derivative, GluCAB-2^Mal , has been synthesized and studied for in vivo ⁶⁴ Cu-PET/CT imaging in breast cancer mice models together with its first-generation analogue GluCAB-1^Mal . The radioligand works on the principle of tumor targeting through the enhanced permeability and retention (EPR) effect with a supportive role played by glucose metabolism. [⁶⁴ Cu]Cu-GluCAB-2^Mal (99 % RCP) exhibited high serum stability with immediate binding to serum proteins. In vivo experiments for comparison between tumor targeting of [⁶⁴ Cu]Cu-GluCAB-2^Mal and previous-generation [⁶⁴ Cu]Cu-GluCAB-1^Mal encompassed microPET/CT imaging and biodistribution analysis in an allograft E0771 breast cancer mouse model. Tumor uptake of [⁶⁴ Cu]Cu-GluCAB-2^Mal was clearly evident with twice as much accumulation as compared to its predecessor and a tumor/muscle ratio of up to 5 after 24 h. Further comparison indicated a decrease in liver accumulation for [⁶⁴ Cu]Cu-Glu-CAB-2^Mal .

Manipulation of immune‒vascular crosstalk: new strategies towards cancer treatment

Tumor vasculature is characterized by aberrant structure and function, resulting in immune suppressive profiles of tumor microenvironment through limiting immune cell infiltration into tumors, endogenous immune surveillance and immune cell function. Vascular normalization as a novel therapeutic strategy tends to prune some of the immature blood vessels and fortify the structure and function of the remaining vessels, thus improving immune stimulation and the efficacy of immunotherapy. Interestingly, the presence of "immune‒vascular crosstalk" enables the formation of a positive feedback loop between vascular normalization and immune reprogramming, providing the possibility to develop new cancer therapeutic strategies. The applications of nanomedicine in vascular-targeting therapy in cancer have gained increasing attention due to its specific physical and chemical properties. Here, we reviewed the recent advances of effective routes, especially nanomedicine, for normalizing tumor vasculature. We also summarized the development of enhancing nanoparticle-based anticancer drug delivery via the employment of transcytosis and mimicking immune cell extravasation. This review explores the potential to optimize nanomedicine-based therapeutic strategies as an alternative option for cancer treatment.

Mechanistic Modeling of Intra-Tumor Spatial Distribution of Antibody-Drug Conjugates: Insights into Dosing Strategies in Oncology

Antibody drug conjugates (ADCs) provide targeted delivery of cytotoxic agents directly inside tumor cells. However, many ADCs targeting solid tumors have exhibited limited clinical efficacy, in part, due to insufficient penetration within tumors. To better understand the relationship between ADC tumor penetration and efficacy, previously applied Krogh cylinder models that explore tumor growth dynamics following ADC administration in preclinical species were expanded to a clinical framework by integrating clinical pharmacokinetics, tumor penetration, and tumor growth inhibition. The objective of this framework is to link ADC tumor penetration and distribution to clinical efficacy. The model was validated by comparing virtual patient population simulations to observed overall response rates from trastuzumab‐DM1 treated patients with metastatic breast cancer. To capture clinical outcomes, we expanded upon previous Krogh cylinder models to include the additional mechanism of heterogeneous tumor growth inhibition spatially across the tumor. This expansion mechanistically captures clinical response rates by describing heterogeneous ADC binding and tumor cell killing; high binding and tumor cell death close to capillaries vs. low binding, and high tumor cell proliferation far from capillaries. Sensitivity analyses suggest that clinical efficacy could be optimized through dose fractionation, and that clinical efficacy is primarily dependent on the ADC‐target affinity, payload potency, and tumor growth rate. This work offers a mechanistic basis to predict and optimize ADC clinical efficacy for solid tumors, allowing dosing strategy optimization to improve patient outcomes.

Short-Term Environmental Conditioning Enhances Tumorigenic Potential of Triple-Negative Breast Cancer Cells

Tumor microenvironments expose cancer cells to heterogeneous, dynamic environments by shifting availability of nutrients, growth factors, and metabolites. Cells integrate various inputs to generate cellular memory that determines trajectories of subsequent phenotypes. Here we report that short-term exposure of triple-negative breast cancer cells to growth factors or targeted inhibitors regulates subsequent tumor initiation. Using breast cancer cells with different driver mutations, we conditioned cells lines with various stimuli for 4 hours before implanting these cells as tumor xenografts and quantifying tumor progression by means of bioluminescence imaging. In the orthotopic model, conditioning a low number of cancer cells with fetal bovine serum led to enhancement of tumor-initiating potential, tumor volume, and liver metastases. Epidermal growth factor and the mTORC1 inhibitor ridaforolimus produced similar but relatively reduced effects on tumorigenic potential. These data show that a short-term stimulus increases tumorigenic phenotypes based on cellular memory. Conditioning regimens failed to alter proliferation or adhesion of cancer cells in vitro or kinase signaling through Akt and ERK measured by multiphoton microscopy in vivo, suggesting that other mechanisms enhanced tumorigenesis. Given the dynamic nature of the tumor environment and time-varying concentrations of small-molecule drugs, this work highlights how variable conditions in tumor environments shape tumor formation, metastasis, and response to therapy.

Natural Compounds Targeting Cancer Stem Cells: A Promising Resource for Chemotherapy

BACKGROUND

Cancer Stem Cells (CSCs) are the subpopulation of cancer cells which are directly involved in drug resistance, metastases to distant organ and cancer recurrence.

METHODS

A systematic literature search was conducted through various electronic databases including, Pubmed, Scopus, Google scholar using the keywords "cancer stem cells" and "natural compounds" in the present study. Articles published between 1999 and 2019 were reviewed. All the expositions concerning CSCs associated cancer pathogenesis and therapy resistance, as well as targeting these properties of CSCs by natural compounds were selected for the current study.

RESULTS

Natural compounds have always been thought as a rich source of biologically active principles, which target aberrantly activated signaling pathways and other modalities of CSCs, while tethering painful side effects commonly involved in the first-line and second-line chemo-radiotherapies. In this review, we have described the key signaling pathways activated in CSCs to maintain their survival and highlighted how natural compounds interrupt these signaling pathways to minimize therapy resistance, pathogenesis and cancer recurrence properties of CSCs, thereby providing useful strategies to treat cancer or aid in cancer therapy improvement. Like normal stem cells, CSCs rely on different signaling pathways and other properties for their maintenance. Therefore, the success of cancer treatment depends on the development of proper anti-neoplastic drugs capable of intercepting those signaling pathways as well as other properties of CSCs in order to eradicate this evasive subpopulation of cancer cells.

CONCLUSION

Compounds of natural origin might act as an outstanding source to design novel therapies against cancer stem cells.

Modification of nitric oxide donors onto a monoclonal antibody boosts accumulation in solid tumors

Although monoclonal antibodies (mAbs) have revolutionized cancer treatment, their accumulation in solid tumors is limited and requires improvement to enhance therapeutic efficacy. Here we developed a strategy to modify mAb with a donor of nitric oxide (NO) because NO functions to vasodilate as well as to enhance the permeability of vascular endothelium, which will contribute to enhancing the tumor accumulation of mAb. We selected S-nitrosothiol as a NO donor and established the procedure to modify S-nitrosothiol group on mAb under ambient conditions. The modified mAb (Ab-SNO) thus obtained released NO in a preferable speed and maintained its original properties such as binding affinity to a target antigen and efficacy to induce antibody-dependent cellular cytotoxicity. We demonstrated that Ab-SNO enhanced the tumor accumulation of co-administered proteins such as antibody and serum albumin.

Interactions Between Tumor Biology and Targeted Nanoplatforms for Imaging Applications

Although considerable efforts have been conducted to diagnose, improve, and treat cancer in the past few decades, existing therapeutic options are insufficient, as mortality and morbidity rates remain high. Perhaps the best hope for substantial improvement lies in early detection. Recent advances in nanotechnology are expected to increase the current understanding of tumor biology, and will allow nanomaterials to be used for targeting and imaging both in vitro and in vivo experimental models. Owing to their intrinsic physicochemical characteristics, nanostructures (NSs) are valuable tools that have received much attention in nanoimaging. Consequently, rationally designed NSs have been successfully employed in cancer imaging for targeting cancer-specific or cancer-associated molecules and pathways. This review categorizes imaging and targeting approaches according to cancer type, and also highlights some new safe approaches involving membrane-coated nanoparticles, tumor cell-derived extracellular vesicles, circulating tumor cells, cell-free DNAs, and cancer stem cells in the hope of developing more precise targeting and multifunctional nanotechnology-based imaging probes in the future.

A Spatial Coherence Beamformer Design for Power Doppler Imaging

Acoustic clutter is a primary source of image degradation in ultrasound imaging. In the context of flow imaging, tissue and acoustic clutter signals are often much larger in magnitude than the blood signal, which limits the sensitivity of conventional power Doppler in SNR-limited environments. This has motivated the development of coherence-based beamformers, including Coherent Flow Power Doppler (CFPD), which have demonstrated efficacy in mitigating sources of diffuse clutter. However, CFPD uses a measure of normalized coherence, which incurs a non-linear relationship between image intensity and the magnitude of the blood echo. As a result, CFPD is not a robust approach to study gradation of blood signal energy, which depicts the fractional moving blood volume. We propose the application of mutual intensity, rather than normalized coherence, to retain the clutter suppression capability inherent in coherence beamforming, while preserving the underlying signal energy. Feasibility of this approach was shown via Field II simulations, phantoms, and in vivo human liver data. In addition, we derive an adaptive statistical threshold for the suppression of residual noise signals. Overall, this beamformer design shows promise as an alternative technique to depict flow volume gradation in cluttered imaging environments.

Gibbs point field model quantifies disorder in microvasculature of U87-glioblastoma

Microvascular proliferation in glioblastoma multiforme is a biological key mechanism to facilitate tumor growth and infiltration and a main target for treatment interventions. The vascular architecture can be obtained by Single Plane Illumination Microscopy (SPIM) to evaluate vascular heterogeneity in tumorous tissue. We make use of the Gibbs point field model to quantify the order of regularity in capillary distributions found in the U87 glioblastoma model in a murine model and to compare tumorous and healthy brain tissue. A single model parameter Γ was assigned that is linked to tissue-specific vascular topology through Monte-Carlo simulations. Distributions of the model parameter Γ differ significantly between glioblastoma tissue with mean 〈Γ_G〉=2.1±0.4, as compared to healthy brain tissue with mean 〈Γ_H〉=4.9±0.4, suggesting that the average Γ-value allows for tissue differentiation. These results may be used for diagnostic magnetic resonance imaging, where it has been shown recently that Γ is linked to tissue-inherent relaxation parameters.