Redirecting Transport of Nanoparticle Albumin-Bound Paclitaxel to Macrophages Enhances Therapeutic Efficacy against Liver Metastases

The role of macrophages in liver metastasis: mechanisms and therapeutic prospects

Metastasis is a hallmark of advanced cancer, and the liver is a common site for secondary metastasis of many tumor cells, including colorectal, pancreatic, gastric, and prostate cancers. Macrophages in the tumor microenvironment (TME) promote tumor cell metastasis through various mechanisms, including angiogenesis and immunosuppression, and play a unique role in the development of liver metastasis. Macrophages are affected by a variety of factors. Under conditions of hypoxia and increased acidity in the TME, more factors are now found to promote the polarization of macrophages to the M2 type, including exosomes and amino acids. M2-type macrophages promote tumor cell angiogenesis through a variety of mechanisms, including the secretion of factors such as VEGF, IL-1β, and TGF-β1. M2-type macrophages are subjected to multiple regulatory mechanisms. They also interact with various cells within the tumor microenvironment to co-regulate certain conditions, including the creation of an immunosuppressive microenvironment. This interaction promotes tumor cell metastasis, drug resistance, and immune escape. Based on the advent of single-cell sequencing technology, further insights into macrophage subpopulations in the tumor microenvironment may help in exploring new therapeutic targets in the future. In this paper, we will focus on how macrophages affect the TME, how tumor cells and macrophages as well as other immune cells interact with each other, and further investigate the mechanisms involved in liver metastasis of tumor cells and their potential as therapeutic targets.

Macrophage Checkpoint Nanoimmunotherapy Has the Potential to Reduce Malignant Progression in Bioengineered In Vitro Models of Ovarian Cancer

Most ovarian carcinoma (OvCa) patients present with advanced disease at the time of diagnosis. Malignant, metastatic OvCa is invasive and has poor prognosis, exposing the need for improved therapeutic targeting. High CD47 (OvCa) and SIRPα (macrophage) expression has been linked to decreased survival, making this interaction a significant target for therapeutic discovery. Even so, previous attempts have fallen short, limited by CD47 antibody specificity and efficacy. Macrophages are an important component of the OvCa tumor microenvironment and are manipulated to aid in cancer progression via CD47-SIRPα signaling. Thus, we have leveraged lipid-based nanoparticles (LNPs) to design a therapy uniquely situated to home to phagocytic macrophages expressing the SIRPα protein in metastatic OvCa. CD47-SIRPα presence was evaluated in patient histological sections using immunohistochemistry. 3D tumor spheroids generated on a hanging drop array with OVCAR3 high-grade serous OvCa and THP-1-derived macrophages created a representative model of cellular interactions involved in metastatic OvCa. Microfluidic techniques were employed to generate LNPs encapsulating SIRPα siRNA (siSIRPα) to affect the CD47-SIRPα signaling between the OvCa and macrophages. siSIRPα LNPs were characterized for optimal size, charge, and encapsulation efficiency. Uptake of the siSIRPα LNPs by macrophages was assessed by Incucyte. Following 48 h of 25 nM siSIRPα treatment, OvCa/macrophage heterospheroids were evaluated for SIRPα knockdown, platinum chemoresistance, and invasiveness. OvCa patient tumors and in vitro heterospheroids expressed CD47 and SIRPα. Macrophages in OvCa spheroids increased carboplatin resistance and invasion, indicating a more malignant phenotype. We observed successful LNP uptake by macrophages causing significant reduction in SIRPα gene and protein expressions and subsequent reversal of pro-tumoral alternative activation. Disrupting CD47-SIRPα interactions resulted in sensitizing OvCa/macrophage heterospheroids to platinum chemotherapy and reversal of cellular invasion outside of heterospheroids. Ultimately, our results strongly indicate the potential of using LNP-based nanoimmunotherapy to reduce malignant progression of ovarian cancer.

Drug resistance and tumor immune microenvironment: An overview of current understandings (Review)

The use of antitumor drugs represents a reliable strategy for cancer therapy. Unfortunately, drug resistance has become increasingly common and contributes to tumor metastasis and local recurrence. The tumor immune microenvironment (TME) consists of immune cells, cytokines and immunomodulators, and collectively they influence the response to treatment. Epigenetic changes including DNA methylation and histone modification, as well as increased drug exportation have been reported to contribute to the development of drug resistance in cancers. In the past few years, the majority of studies on tumors have only focused on the development and progression of a tumor from a mechanistic standpoint; few studies have examined whether the changes in the TME can also affect tumor growth and drug resistance. Recently, emerging evidence have raised more concerns regarding the role of TME in the development of drug resistance. In the present review, it was discussed how the suppressive TME adapts to drug resistance characterized by the cooperation of immune cells, cytokines, immunomodulators, stromal cells and extracellular matrix. Furthermore, it was reviewed how these immunological or metabolic changes alter immuno‑surveillance and thus facilitate tumor drug resistance. In addition, potential targets present in the TME for developing novel therapeutic strategies to improve individualized therapy for cancer treatment were revealed.

Characterization of the Breast Cancer Liver Metastasis Microenvironment via Machine Learning Analysis of the Primary Tumor Microenvironment

Breast cancer liver metastases (BCLM) are hypovascular lesions that resist intravenously administered therapies and have grim prognosis. Immunotherapeutic strategies targeting BCLM critically depend on the tumor microenvironment (TME), including tumor-associated macrophages. However, a priori characterization of the BCLM TME to optimize therapy is challenging because BCLM tissue is rarely collected. In contrast to primary breast tumors for which tissue is usually obtained and histologic analysis performed, biopsies or resections of BCLM are generally discouraged due to potential complications. This study tested the novel hypothesis that BCLM TME characteristics could be inferred from the primary tumor tissue. Matched primary and metastatic human breast cancer samples were analyzed by imaging mass cytometry, identifying 20 shared marker clusters denoting macrophages (CD68, CD163, and CD206), monocytes (CD14), immune response (CD56, CD4, and CD8a), programmed cell death protein 1, PD-L1, tumor tissue (Ki-67 and phosphorylated ERK), cell adhesion (E-cadherin), hypoxia (hypoxia-inducible factor-1α), vascularity (CD31), and extracellular matrix (alpha smooth muscle actin, collagen, and matrix metalloproteinase 9). A machine learning workflow was implemented and trained on primary tumor clusters to classify each metastatic cluster density as being either above or below median values. The proposed approach achieved robust classification of BCLM marker data from matched primary tumor samples (AUROC ≥ 0.75, 95% confidence interval ≥ 0.7, on the validation subsets). Top clusters for prediction included CD68+, E-cad+, CD8a+PD1+, CD206+, and CD163+MMP9+. We conclude that the proposed workflow using primary breast tumor marker data offers the potential to predict BCLM TME characteristics, with the longer term goal to inform personalized immunotherapeutic strategies targeting BCLM.

SIGNIFICANCE

BCLM tissue characterization to optimize immunotherapy is difficult because biopsies or resections are rarely performed. This study shows that a machine learning approach offers the potential to infer BCLM characteristics from the primary tumor tissue.

Mechanisms and Barriers in Nanomedicine: Progress in the Field and Future Directions

In recent years, steady progress has been made in synthesizing and characterizing engineered nanoparticles, resulting in several approved drugs and multiple promising candidates in clinical trials. Regulatory agencies such as the Food and Drug Administration and the European Medicines Agency released important guidance documents facilitating nanoparticle-based drug product development, particularly in the context of liposomes and lipid-based carriers. Even with the progress achieved, it is clear that many barriers must still be overcome to accelerate translation into the clinic. At the recent conference workshop "Mechanisms and Barriers in Nanomedicine" in May 2023 in Colorado, U.S.A., leading experts discussed the formulation, physiological, immunological, regulatory, clinical, and educational barriers. This position paper invites open, unrestricted, nonproprietary discussion among senior faculty, young investigators, and students to trigger ideas and concepts to move the field forward.

Harnessing Microbial Effectors for Macrophage-Mediated Drug Delivery

Macrophage-based drug delivery systems are promising, but their development is still in its infancy, with many limitations remaining to be addressed. Our aim was to design a system harnessing microbial effectors to facilitate controlled drug cargo expulsion from macrophages to enable the use of more toxic drugs without adding to the risk of off-target detrimental effects. The pore forming and actin polymerizing Listeria monocytogenes effectors listeriolysin-O (LLO) and actin assembly-inducing protein (ActA) were synthesized using a novel green fluorescent protein (GFP)-linked heterologous expression system. These effectors were coated onto polystyrene beads to generate "synthetic cargo" before loading into primary M1 macrophages. Bead uptake and release from macrophages were evaluated by using high-throughput quantitative imaging flow cytometry and confocal microscopy. In vitro results confirmed appropriate activity of synthesized effectors. Coating of these effector proteins onto polystyrene beads (simulated drug cargo) resulted in changes in cellular morphology, bead content, and intracellular bead localization, which may support an interpretation of the induced release of these beads from the cells. This forms the basis for further investigation to fully elucidate any potential release mechanisms. Bacterial effectors ActA and LLO successfully effectuated actin polarization and protrusions from cell membranes similar to those seen in cells infected with Listeria spp., illustrating the potential of using these effectors and production methods for the development of an endogenous drug delivery system capable of low-risk, targeted release of high potency drugs.

IL4 receptor targeting enables nab-paclitaxel to enhance reprogramming of M2-type macrophages into M1-like phenotype via ROS-HMGB1-TLR4 axis and inhibition of tumor growth and metastasis

Rationale: Nab-paclitaxel (Abx) is widely employed in malignant tumor therapy. In tumor cells and pro-tumoral M2-type macrophages, the IL4 receptor (IL4R) is upregulated. This study aimed to elucidate the selective delivery of Abx to M2-type macrophages by targeting IL4R and reprogramming them into an anti-tumoral M1-type. Methods: Abx was conjugated with the IL4R-binding IL4RPep-1 peptide using click chemistry (IL4R-Abx). Cellular internalization, macrophage reprogramming and signal pathways, and tumor growth and metastasis by IL4R-Abx were examined. Results: IL4R-Abx was internalized into M2 macrophages more efficiently compared to the unmodified Abx and control peptide-conjugated Abx (Ctrl-Abx), which was primarily inhibited using an anti-IL4R antibody and a receptor-mediated endocytosis inhibitor compared with a macropinocytosis inhibitor. IL4R-Abx reprogrammed the M2-type macrophages into M1-like phenotype and increased reactive oxygen species (ROS) levels and extracellular release of high mobility group box 1 (HMGB1) in M2 macrophages at higher levels than Abx and Ctrl-Abx. The conditioned medium of IL4R-Abx-treated M2 macrophages skewed M2 macrophages into the M1-like phenotype, in which an anti-HMGB1 antibody and a toll-like receptor 4 (TLR4) inhibitor induced a blockade. IL4R-Abx accumulated at tumors, heightened immune-stimulatory cells while reducing immune-suppressing cells, and hampered tumor growth and metastasis in mice more efficiently than Abx and Ctrl-Abx. Conclusions: These results indicate that IL4R-targeting allows enhancement of M2-macrophage shaping into M1-like phenotype by Abx through the ROS-HMGB1-TLR4 axis, improvement of antitumor immunity, and thereby inhibition of tumor growth and metastasis, presenting a new approach to cancer immunotherapy.

Development of Human Serum Albumin Fluorescent Probes in Detection, Imaging, and Disease Therapy

Human serum albumin (HSA) acts as a repository and transporter of substances in the blood. An abnormal concentration may indicate the occurrence of liver- and kidney-related diseases, which has attracted people to investigate the precise quantification of HSA in body fluids. Fluorescent probes can combine with HSA covalently or noncovalently to quantify HSA in urine and plasma. Moreover, probes combined with HSA can improve its photophysical properties; probe-HSA has been applied in real-time monitoring and photothermal and photodynamic therapy in vivo. This Review will introduce fluorescent probes for quantitative HSA according to the three reaction mechanisms of spatial structure, enzymatic reaction, and self-assembly and systematically introduce the application of probes combined with HSA in disease imaging and phototherapy. It will help develop multifunctional applications for HSA probes and provide assistance in the early diagnosis and treatment of diseases.

Design strategies for enhancing antitumor efficacy through tumor microenvironment exploitation using albumin-based nanosystems: A review

The tumor microenvironment (TME) is a complex and dynamic system that plays a crucial role in regulating cancer progression, treatment response, and the emergence of acquired resistance mechanisms. The TME is usually featured by severe hypoxia, low pH values, high hydrogen peroxide (H2O2) concentrations, and overproduction of glutathione (GSH). The current development of intelligent nanosystems that respond to TME has shown great potential to enhance the efficacy of cancer treatment. As one of the functional macromolecules explored in this field, albumin-based nanocarriers, known for their inherent biocompatibility, serves as a cornerstone for constructing diverse therapeutic platforms. In this paper, we present a comprehensive overview of the latest advancements in the design strategies of albumin nanosystems, aiming to enhance cancer therapy by harnessing various features of solid tumors, including tumor hypoxia, acidic pH, the condensed extracellular matrix (ECM) network, excessive GSH, high glucose levels, and tumor immune microenvironment. Furthermore, we highlight representative designs of albumin-based nanoplatforms by exploiting the TME that enhance a broad range of cancer therapies, such as chemotherapy, phototherapy, radiotherapy, immunotherapy, and other tumor therapies. Finally, we discuss the existing challenges and future prospects in direction of albumin-based nanosystems for the practical applications in advancing enhanced cancer treatments.

Palmitic acid-modified human serum albumin paclitaxel nanoparticles targeting tumor and macrophages against breast cancer

Breast cancer is the most common malignant tumor in women, and the liver is the main target organ for breast cancer metastasis. Once metastasis occurs, the prognosis is very poor. The uptake of PSA NPs made by our synthesized Palmitic acid-modified human serum albumin (PSA) in macrophages is about 15 times higher than that of HSA NPs. As a first-line chemotherapeutic drug, paclitaxel not only does not kill macrophages, but it can also polarize macrophages into classically activated macrophages (M1). We combined these two characteristics into PTX-PSA NPs, which achieved dual targeting of macrophages and tumor cells, improved the tumor microenvironment, and achieved a more effective anti-breast cancer drug effect than PTX-HSA NPs. On this basis, we also used the pathological characteristics of low vascular perfusion of breast cancer liver metastasis, and used the characteristics of macrophages that can release paclitaxel after internalizing paclitaxel, and use macrophages as the delivery system of breast cancer liver metastasis. Therefore,PTX-PSA NPs is better than PTX-HSA NPs to achieve anti-breast cancer liver metastasis.

Anti-Inflammatory Activation of Phellodendri Chinensis Cortex is Mediated by Berberine Erythrocytes Self-Assembly Targeted Delivery System

Background

Berberine (BBR) is the primary active component of Phellodendri Chinensis Cortex (PCC), which has been traditionally used to treat inflammatory diseases. However, the discrepancy between its low bioavailability and significant therapeutic effect remains obscure. The purpose of this study was to explore the previously unsolved enigma of the low bioavailability of BBR and its appreciable anti-inflammatory effect to reveal the action mechanism of BBR and PCC.

Methods

The quantitative analysis of BBR and its metabolite oxyberberine (OBB) in blood and tissues was performed using high-performance liquid chromatography to investigate the conversion and distribution of BBR/OBB mediated by erythrocytes. Routine blood tests and immunohistochemical staining were used to explore the potential relationship between the amounts of monocyte/macrophage and the drug concentration in erythrocytes and tissues (liver, heart, spleen, lung, kidney, intestine, muscle, brain and pancreas). To comparatively explore the anti-inflammatory effects of BBR and OBB, the acetic acid-induced vascular permeability mice model and lipopolysaccharide-induced RAW 264.7 macrophages were employed.

Results

Nearly 92% of BBR existed in the erythrocytes in rats. The partition coefficient of BBR between plasma and erythrocytes (Kp/b) decreased with time. OBB was found to be the oxidative metabolite of BBR in erythrocytes. Proportion of BBR/OBB in erythrocytes changed from 9.38% to 16.30% and from 13.50% to 46.24%, respectively. There was a significant relationship between the BBR/OBB concentration in blood and monocyte depletion after a single administration of BBR. BBR/OBB was transported via erythrocytes to various tissues (liver, kidney, spleen, lung, and heart, etc), with the liver achieving the highest concentration. OBB exhibited similar anti-inflammatory effect in vitro and in vivo as BBR with much smaller dosage.

Conclusion

BBR was prodominantly found in erythrocytes, which was critically participated in the biodistribution, pharmacokinetics, metabolism and target delivery of BBR and its metabolite. The anti-inflammatory activity of BBR and PCC was intimately associated with the metabolism into the active congener OBB and the targeted delivery to monocytes/macrophages mediated by the erythrocytes.

Tailoring biomaterials and applications targeting tumor-associated macrophages in cancers

Tumor-associated macrophages (TAMs) play a critical role in supporting tumor growth and metastasis, taming host immunosurveillance, and augmenting therapeutic resistance. As the current treatment paradigms for cancers are generally insufficient to exterminate cancer cells, anti-cancer therapeutic strategies targeting TAMs have been developed. Since TAMs are highly heterogeneous and the pro-tumoral functions are mediated by phenotypes with canonical surface markers, TAM-associated materials exert anti-tumor functions by either inhibiting polarization to the pro-tumoral phenotype or decreasing the abundance of TAMs. Furthermore, TAMs in association with the immunosuppressive tumor microenvironment (TME) and tumor immunity have been extensively exploited in mounting evidence, and could act as carriers or accessory cells of anti-tumor biomaterials. Recently, a variety of TAM-based materials with the capacity to target and eliminate cancer cells have been increasingly developed for basic research and clinical practice. As various TAM-based biomaterials, including antibodies, nanoparticles, RNAs, etc., have been shown to have potential anti-tumor effects reversing the TME, in this review, we systematically summarize the current studies to fully interpret the specific properties and various effects of TAM-related biomaterials, highlighting the potential clinical applications of targeting the crosstalk among TAMs, tumor cells, and immune cells in anti-cancer therapy.

Targeted non AR mediated smart delivery of abiraterone to the prostate cancer

Prostate cancer is the second-deadliest tumor in men all over the world. Different types of drugs with various delivery systems and pathways were developed, but no one showed prominent results against cancer. Meanwhile, nanoparticles have shown good results against cancer. Therefore, in the given study, citrate mediated synthesized gold nanoparticles (CtGNPs) with immobilized survivin antibodies (SvGNPs) were bioconjugated to the substantially potent drug abiraterone (AbSvGNPs) to develop as a combinatorial therapeutic against prostate cancer. The AbSvGNPs are made up of CtGNPs, survivin antibodies, and abiraterone. The selected drug abiraterone (Abira) possesses exceptionally good activity against prostate cancer, but cancer cells develop resistance against this drug and it also poses several severe side effects. Meanwhile, survivin antibodies were used to deliver AbSvGNPs specifically into cancer cells by considering survivin, an anti-apoptotic overexpressed protein in cancer cells, as a marker. The survivin antibodies have also been used to inhibit cancer cells as an immunotherapeutic agent. Similarly, CtGNPs were discovered to inhibit cancer cell proliferation via several transduction pathways. The given bioconjugated nanoparticles (AbSvGNPs) were found to be substantially effective against prostate cancer with an IC50 of 11.8 and 7.3 μM against DU145 and PC-3 cells, respectively. However, it was found safe against NRK and showed less than 25% cytotoxicity up to 20μM concentration. The as-synthesized nanoparticles CtGNPs, SvGNPs, and AbSvGNPs were characterized by several physical techniques to confirm their synthesis, whereas the immobilization of survivin antibodies and bioconjugation of Abira was confirmed by UV-visible spectroscopy, DLS, TEM, FTIR, and zeta-potential. The anticancer potential of AbSvGNPs was determined by MTT, DAPI, ROS, MITO, TUNEL ASSAY, and caspase-3 activity against DU145 and PC3 cells.

The NLRP3 Activation in Infiltrating Macrophages Contributes to Corneal Fibrosis by Inducing TGF-β1 Expression in the Corneal Epithelium

Purpose

To explore the effect and mechanism of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes on corneal fibrosis.

Methods

The wild-type, NLRP3 knockout (KO), and myeloid cell-specific NLRP3 KO (NLRP3 Lyz-KO) C57 mice were used to establish a corneal scarring model. NLRP3 inhibitor, IL-1β neutralizing antibody, and an IL-1R antagonist were used to investigate the role of NLRP3 and IL-1β in corneal fibrosis. The expression of the NLRP3 signaling pathway related proteins, alpha-smooth muscle actin, TGF-β was determined by quantitative real-time polymerase chain reaction, Western blotting, and immunofluorescence staining. Flow cytometry was used to detect the infiltration of macrophages during corneal fibrosis.

Results

The components of the NLRP3 inflammasomes were elevated and activated during corneal scarring. Additionally, genetic or chemical-mediated blocking of NLRP3 as well as IL-1β significantly alleviated corneal fibrosis. Moreover, neutrophil (CD45⁺Ly6G⁺) and macrophage (CD45⁺ F4/80⁺) accumulation increased in the cornea during the progression of corneal fibrosis. Intriguingly, the increased concentrations of NLRP3 and IL-1β were prominently colocalized with the infiltrating F4/80⁺ macrophages. Expectedly, NLRP3 Lyz-KO mice exhibited a marked decrease in their corneal fibrosis symptoms. Mechanistically, the activation of IL-1β or macrophage NLRP3 stimulated the expression of TGF-β1 in the corneal epithelial cells, whereas an NLRP3 deficiency decreased its expression in the corneal epithelium.

Conclusions

These observations revealed that the NLRP3 inflammasome activation in infiltrating macrophages contributes to corneal fibrosis by regulating corneal epithelial TGF-β1 expression. Targeting the NLRP3 inflammasome might be a promising strategy for the treatment of corneal scarring.

Nanostructured particles assembled from natural building blocks for advanced therapies

Advanced treatments based on immune system manipulation, gene transcription and regulation, specific organ and cell targeting, and/or photon energy conversion have emerged as promising therapeutic strategies against a range of challenging diseases. Naturally derived macromolecules (e.g., proteins, lipids, polysaccharides, and polyphenols) have increasingly found use as fundamental building blocks for nanostructured particles as their advantageous properties, including biocompatibility, biodegradability, inherent bioactivity, and diverse chemical properties make them suitable for advanced therapeutic applications. This review provides a timely and comprehensive summary of the use of a broad range of natural building blocks in the rapidly developing field of advanced therapeutics with insights specific to nanostructured particles. We focus on an up-to-date overview of the assembly of nanostructured particles using natural building blocks and summarize their key scientific and preclinical milestones for advanced therapies, including adoptive cell therapy, immunotherapy, gene therapy, active targeted drug delivery, photoacoustic therapy and imaging, photothermal therapy, and combinational therapy. A cross-comparison of the advantages and disadvantages of different natural building blocks are highlighted to elucidate the key design principles for such bio-derived nanoparticles toward improving their performance and adoption. Current challenges and future research directions are also discussed, which will accelerate our understanding of designing, engineering, and applying nanostructured particles for advanced therapies.

Nanoparticle based medicines: approaches for evading and manipulating the mononuclear phagocyte system and potential for clinical translation

For decades, nanomedicines have been reported as a potential means to overcome the limitations of conventional drug delivery systems by reducing side effects, toxicity and the non-ideal pharmacokinetic behaviour typically exhibited by small molecule drugs. However, upon administration many nanoparticles prompt induction of host inflammatory responses due to recognition and uptake by macrophages, eliminating up to 95% of the administered dose. While significant advances in nanoparticle engineering and consequent therapeutic efficacy have been made, it is becoming clear that nanoparticle recognition by the mononuclear phagocyte system (MPS) poses an impassable junction in the current framework of nanoparticle development. Hence, this has negative consequences on the clinical translation of nanotechnology with respect to therapeutic efficacy, systemic toxicity and economic benefit. In order to improve the translation of nanomedicines from bench-to-bedside, there is a requirement to either modify nanomedicines in terms of how they interact with intrinsic processes in the body, or modulate the body to be more accommodating for nanomedicine treatments. Here we provide an overview of the current standard for design elements of nanoparticles, as well as factors to consider when producing nanomedicines that have minimal MPS-nanoparticle interactions; we explore this landscape across the cellular to tissue and organ levels. Further, rather than designing materials to suit the body, a growing research niche involves modulating biological responses to administered nanomaterials. We here discuss how developing strategic methods of MPS 'pre-conditioning' with small molecule or biological drugs, as well as implementing strategic dosing regimens, such as 'decoy' nanoparticles, is essential to increasing nanoparticle therapeutic efficacy. By adopting such a perspective, we hope to highlight the increasing trends in research dedicated to improving nanomedicine translation, and subsequently making a positive clinical impact.

Paclitaxel: Application in Modern Oncology and Nanomedicine-Based Cancer Therapy

Paclitaxel is a broad-spectrum anticancer compound, which was derived mainly from a medicinal plant, in particular, from the bark of the yew tree Taxus brevifolia Nutt. It is a representative of a class of diterpene taxanes, which are nowadays used as the most common chemotherapeutic agent against many forms of cancer. It possesses scientifically proven anticancer activity against, e.g., ovarian, lung, and breast cancers. The application of this compound is difficult because of limited solubility, recrystalization upon dilution, and cosolvent-induced toxicity. In these cases, nanotechnology and nanoparticles provide certain advantages such as increased drug half-life, lowered toxicity, and specific and selective delivery over free drugs. Nanodrugs possess the capability to buildup in the tissue which might be linked to enhanced permeability and retention as well as enhanced antitumour influence possessing minimal toxicity in normal tissues. This article presents information about paclitaxel, its chemical structure, formulations, mechanism of action, and toxicity. Attention is drawn on nanotechnology, the usefulness of nanoparticles containing paclitaxel, its opportunities, and also future perspective. This review article is aimed at summarizing the current state of continuous pharmaceutical development and employment of nanotechnology in the enhancement of the pharmacokinetic and pharmacodynamic features of paclitaxel as a chemotherapeutic agent.

Nab-paclitaxel promotes the cancer-immunity cycle as a potential immunomodulator

Paclitaxel is a widely used anti-tumor chemotherapeutic drug. Solvent-based paclitaxel causes bone marrow suppression, allergic reactions, neurotoxicity and systemic toxicity, which are associated with non-specific cytotoxicity and side effects of fat-soluble solvents. Studies have explored various new nano-drug strategies of paclitaxel, including nanoparticle albumin-bound paclitaxel (nab-paclitaxel) to improve the water solubility and safety of paclitaxel. Nab-paclitaxel is a targeted solvent-free formulation that inhibits microtubule depolymerization to anticancer. It is easily taken up by tumor and immune cells owing to the nano-scaled size and superior biocompatibility. The internalized nab-paclitaxel exhibits significant immunostimulatory activities to promote cancer-immunity cycle. The aim of this study was to explore the synergistic effect of nab-paclitaxel in tumor antigen presentation, T cell activation, reversing the immunosuppressive pattern of tumor microenvironment (TME), and the synergistic effect with cytotoxic lymphocytes (CTLs) in clearance of tumor cells. The effects of nab-paclitaxel on modulation of cancer-immunity cycle, provides potential avenues for combined therapeutic rationale to improve efficacy of immunotherapy.

Seed- and Soil-Dependent Differences in Murine Breast Tumor Microenvironments Dictate Anti-PD-L1 IgG Delivery and Therapeutic Efficacy

We sought to determine if Stephen Paget’s “seed and soil” hypothesis of organ-preference patterns of cancer metastasis can explain the development of heterogeneity in a tumor microenvironment (TME) as well as immunotherapeutic delivery and efficacy. We established single-cell-derived clones (clones 1 and 16) from parental 4T1 murine breast cancer cells to create orthotopic primary and liver metastasis models to deconvolute polyclonal complexity cancer cells and the difference in TME-derived heterogeneities. Tumor-bearing mice were treated with anti-PD-L1 IgG or a control antibody, and immunofluorescent imaging and quantification were then performed to evaluate the therapeutic efficacy on tumor growth, the delivery of therapy to tumors, the development of blood vessels, the expression of PD-L1, the accumulation of immune cells, and the amount of coagulation inside tumors. The quantification showed an inverse correlation between the amount of delivered therapy and therapeutic efficacy in parental-cell-derived tumors. In contrast, tumors originating from clone 16 cells accumulated a significantly greater amount of therapy and responded better than clone-1-derived tumors. This difference was greater when tumors grew in the liver than the primary site. A similar trend was found in PD-L1 expression and immune cell accumulation. However, the change in the number of blood vessels was not significant. In addition, the amount of coagulation was more abundant in clone-1-derived tumors when compared to others. Thus, our findings reconfirmed the seed- and soil-dependent differences in PD-L1 expression, therapeutic delivery, immune cell accumulation, and tumor coagulation, which can constitute a heterogeneous delivery and response of immunotherapy in polyclonal tumors growing in different organs.

Calcium phosphate engineered photosynthetic microalgae to combat hypoxic-tumor by in-situ modulating hypoxia and cascade radio-phototherapy

Rationale: Hypoxia is one of the crucial restrictions in cancer radiotherapy (RT), which leads to the hypoxia-associated radioresistance of tumor cells and may result in the sharp decline in therapeutic efficacy. Methods: Herein, living photosynthetic microalgae (Chlorella vulgaris, C. vulgaris), were used as oxygenators, for in situ oxygen generation to relieve tumor hypoxia. We engineered the surface of C. vulgaris (CV) cells with calcium phosphate (CaP) shell by biomineralization, to form a biomimetic system (CV@CaP) for efficient tumor delivery and in-situ active photosynthetic oxygenation reaction in tumor. Results: After intravenous injection into tumor-bearing mice, CV@CaP could remarkably alleviate tumor hypoxia by continuous oxygen generation, thereby achieving enhanced radiotherapeutic effect. Furthermore, a cascade phototherapy could be fulfilled by the chlorophyll released from photosynthetic microalgae combined thermal effects under 650 nm laser irradiation. The feasibility of CV@CaP-mediated combinational treatment was finally validated in an orthotropic breast cancer mouse model, revealing its prominent anti-tumor and anti-metastasis efficacy in hypoxic-tumor management. More importantly, the engineered photosynthetic microalgae exhibited excellent fluorescence and photoacoustic imaging properties, allowing the self-monitoring of tumor therapy and tumor microenvironment. Conclusions: Our studies of this photosynthetic microsystem open up a new dimension for solving the radioresistance issue of hypoxic tumors.

Cell relay-delivery improves targeting and therapeutic efficacy in tumors

Cell-mediated drug delivery system (CDDS) has shown great potential for cancer therapy. However, a single cell-mediated drug delivery mechanism has not generally been successful, particularly for systemic administration. To augment the antitumor therapy efficacy, herein, we propose a strategy of cell relay-delivery for the use of artificially damaging/aging erythrocytes to hitchhike on circulating monocytes/macrophages for intratumoral accumulation of anticancer drugs. This biomimetic relay-delivery strategy was derived from the manner in which circulating monocytes/macrophages in body specifically engulf damaged/senescent erythrocytes and actively transmigrate into the tumor bulk. The strategy elegantly combines the natural functions of both cells, which therefore provides a new perspective to challenge current obstacles in drug delivery. According to the strategy, we developed biotinylated erythrocyte-poly (lactic-co-glycolic acid) (PLGA) nanoparticle hybrid DDSs (bE-NPs) using avidin-biotin coupling. In such a system, biotinylated erythrocytes can mimic the natural property of damaged/senescent erythrocytes, while PLGA NPs are capable of encapsulating anticancer drugs and promoting sustained drug release. Anticancer drugs can effectively target tumor sites by two steps. First, by using biotinylated erythrocytes as the carrier, the drug-loaded PLGA NPs could be specifically phagocytized by monocytes/macrophages. Second, by taking advantage of the tumor-tropic property of monocytes/macrophages, the drug-loaded PLGA NPs could be efficiently transported into the tumor bulk. After encapsulating vincristine (VIN) as the model drug, bE-NPs exhibited the most favorable antitumor effects in vitro and in vivo by the cell relay-delivery effect. These results demonstrate that the cell relay-delivery provides a potential method for improving tumor treatment efficacy.

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The strategy of cell relay-delivery combines the functions of monocytes/macrophages and damaged/senescent erythrocytes.

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According to the strategy of cell relay-delivery, the bE-NPs can effectively target tumor sites by two steps.

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The bE-NPs demonstrated the synergistic power of different size-scale technologies.

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.

Tumor-associated macrophages: Role in the pathological process of tumorigenesis and prospective therapeutic use (Review)

The aim of the present study was to evaluate the current body of knowledge regarding tumor-associated macrophages (TAMs) and their potential use in antitumor therapy, based on their role in the pathological process of tumorigenesis. For this purpose, a critical analysis of published data and summarization of the findings available from original studies, focusing on the role of TAMs in the pathological process, and their potential therapeutic application was performed. Promising key avenues of research were identified in this field. The following issues seem the most promising and thus worth further investigation: i) The process of M1/M2 macrophage polarization, macrophage characteristics at intermediate polarization steps and their role in the tumor process; ii) determining the conditions necessary for transitions between the M1 and M2 macrophage phenotypes and the role of signals from the microenvironment in this process; iii) cause-and-effect associations between the quantity and quality of macrophages, and the prognosis and outcome of the pathological process; iv) modulation of macrophages and stimulation of their phagocytic activity with drugs; v) targeted vector-based systems for drug delivery to macrophages; and vi) targeted drug delivery systems with macrophages as carriers, thus potentially combining chemotherapy and immunotherapy.

Modeling of Nanotherapy Response as a Function of the Tumor Microenvironment: Focus on Liver Metastasis

The tumor microenvironment (TME) presents a challenging barrier for effective nanotherapy-mediated drug delivery to solid tumors. In particular for tumors less vascularized than the surrounding normal tissue, as in liver metastases, the structure of the organ itself conjures with cancer-specific behavior to impair drug transport and uptake by cancer cells. Cells and elements in the TME of hypovascularized tumors play a key role in the process of delivery and retention of anti-cancer therapeutics by nanocarriers. This brief review describes the drug transport challenges and how they are being addressed with advanced in vitro 3D tissue models as well as with in silico mathematical modeling. This modeling complements network-oriented techniques, which seek to interpret intra-cellular relevant pathways and signal transduction within cells and with their surrounding microenvironment. With a concerted effort integrating experimental observations with computational analyses spanning from the molecular- to the tissue-scale, the goal of effective nanotherapy customized to patient tumor-specific conditions may be finally realized.

Nonlinear response to cancer nanotherapy due to macrophage interactions revealed by mathematical modeling and evaluated in a murine model via CRISPR-modulated macrophage polarization

Tumor-associated macrophages (TAMs) have been shown to both aid and hinder tumor growth, with patient outcomes potentially hinging on the proportion of M1, pro-inflammatory/growth-inhibiting, to M2, growth-supporting, phenotypes. Strategies to stimulate tumor regression by promoting polarization to M1 are a novel approach that harnesses the immune system to enhance therapeutic outcomes, including chemotherapy. We recently found that nanotherapy with mesoporous particles loaded with albumin-bound paclitaxel (MSV-nab-PTX) promotes macrophage polarization towards M1 in breast cancer liver metastases (BCLM). However, it remains unclear to what extent tumor regression can be maximized based on modulation of the macrophage phenotype, especially for poorly perfused tumors such as BCLM. Here, for the first time, a CRISPR system is employed to permanently modulate macrophage polarization in a controlled in vitro setting. This enables the design of 3D co-culture experiments mimicking the BCLM hypovascularized environment with various ratios of polarized macrophages. We implement a mathematical framework to evaluate nanoparticle-mediated chemotherapy in conjunction with TAM polarization. The response is predicted to be not linearly dependent on the M1:M2 ratio. To investigate this phenomenon, the response is simulated via the model for a variety of M1:M2 ratios. The modeling indicates that polarization to an all-M1 population may be less effective than a combination of both M1 and M2. Experimental results with the CRISPR system confirm this model-driven hypothesis. Altogether, this study indicates that response to nanoparticle-mediated chemotherapy targeting poorly perfused tumors may benefit from a fine-tuned M1:M2 ratio that maintains both phenotypes in the tumor microenvironment during treatment.

Critical considerations for targeting colorectal liver metastases with nanotechnology

Colorectal cancer remains a significant cause of morbidity and mortality worldwide. Half of all patients develop liver metastases, presenting unique challenges for their treatment. The shortcomings of conventional chemotherapy has encouraged the use of nanomedicines; the application of nanotechnology in the diagnosis and treatment of disease. In spite of technological improvements in nanotechnology, the complexity of biological systems hinders the prospect of nanomedicines being applied in cancer therapy at the present time. This review highlights current biological barriers and discusses aspects of tumor biology together with the physicochemical features of the nanocarrier, that need to be considered in order to develop effective nanotherapeutics for colorectal cancer patients with liver metastases. It becomes clear that incorporating an interdisciplinary approach when developing nanomedicines should assure appropriate disease-driven design and that this will form a critical step in improving their clinical translation. This article is characterized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Bone-Seeking Albumin-Nanomedicine for In Vivo Imaging and Therapeutic Monitoring

Malignant osteolysis associated with irreversible primary bone tumors and bone metastases remains a clinically urgent problem. Exploiting the imaging and therapy function of flexible nanomedicine can provide an alternative for therapeutic navigation and monitoring of malignant osteolysis. Here, we report the development of albumin-based gadolinium oxide nanoparticles loaded with doxorubicin and conjugated with bone-seeking alendronate for targeted delivery and therapeutic monitoring. Compared with nontargeted nanomedicine, bone-seeking accumulation and retention can be proven by MRI in a rat model of focal malignant osteolysis. Meanwhile, we observed a whole-body distribution in the consecutive SPECT imaging after radiolabeling with ¹²⁵I, SPECT imaging also indicated the enhanced bone tumor accumulation and prolonged retention. Resulting from the high drug loading and ¹³¹I labeling efficiency, the targeted nanomedicine exhibited significant chemotherapy and inter-radiotherapy capacity. Ultimately, the tumor burden of rats was obviously decreased except for the nontargeted group and the empty carrier group. In vivo CT imaging and pathological analysis revealed that the combined therapy was an efficient measure for antiosteolysis. Our findings suggest that albumin-based nanomedicine can provide a platform for bone-seeking diagnosis and therapeutic monitoring.

Systematic comparison of methods for determining the in vivo biodistribution of porous nanostructured injectable inorganic particles

With a wide variety of biodistribution measurement techniques reported in the literature, it is important to perform side-by-side comparisons of results obtained with different methods on the same particle platform, to determine differences across methods, highlight advantages and disadvantages, and inform methods selection according to specific applications. Inorganic nanostructured particles (INPs) have gained a central role in the development of injectable delivery vectors thanks to their controllable design, biocompatibility, and favorable degradation kinetic. Thus, accurate determination of in vivo biodistribution of INPs is a key aspect of developing and optimizing this class of delivery vectors. In this study, a systematic comparison of spectroscopy (inductively coupled plasma optical emission spectroscopy), fluorescence (in vivo imaging system, confocal microscopy, and plate reader), and radiolabeling (gamma counter)-based techniques is performed to assess the accuracy and sensitivity of biodistribution measurements in mice. Each method is evaluated on porous silicon particles, an established and versatile injectable delivery platform. Biodistribution is evaluated in all major organs and compared in terms of absolute results (%ID/g and %ID/organ when possible) and sensitivity (σ_%). Finally, we discuss how these results can be extended to inform method selection for other platforms and specific applications, with an outlook to potential benefit for pre-clinical and clinical studies. Overall, this study presents a new practical guide for selection of in vivo biodistribution methods that yield quantitative results. STATEMENT OF SIGNIFICANCE: The significance of this work lies in the use of a single platform to test performances of different biodistribution methods in vivo, with a strict quantitative metric. These results, united with the qualitative comparison of advantages and disadvantages of each technique, are aimed at supporting the rational choice of each different method according to the specific application, to improve the quantitative description of biodistribution results that will be published by others in the future.

Intracellular nanoparticle delivery by oncogenic KRAS-mediated macropinocytosis

Background

The RAS family of oncogenes (KRAS, HRAS, NRAS) are the most frequent mutations in cancers and regulate key signaling pathways that drive tumor progression. As a result, drug delivery targeting RAS-driven tumors has been a long-standing challenge in cancer therapy. Mutant RAS activates cancer cells to actively take up nutrients, including glucose, lipids, and albumin, via macropinocytosis to fulfill their energetic requirements to survive and proliferate.

Purpose

We exploit macropinocytosis pathway to deliver nanoparticles (NPs) in cancer cells harboring activating KRAS mutations.

Methods

NPs were synthesized by the desolvation method. The physicochemical properties and stability of NPs were characterized by dynamic light scattering and transmission electron microscopy. Uptake of fluorescently labelled NPs in wild-type and mutant KRAS cells were quantitively determined by flow cytometry and qualitatively by fluorescent microscopy. NP uptake by KRAS-driven macropinocytosis was confirmed by pharmacological inhibition and genetic knockdown.

Results

We have synthesized stable albumin NPs that demonstrate significantly greater uptake in cancer cells with activating mutations of KRA S than monomeric albumin (ie, dissociated form of clinically used nab-paclitaxel). From pharmacological inhibition and semi-quantitative fluorescent microscopy studies, these NPs exhibit significantly increased uptake in mutant KRAS cancer cells than wild-type KRAS cells by macropinocytosis.

Conclusions

The uptake of albumin nanoparticles is driven by KRAS. This NP-based strategy targeting RAS-driven macropinocytosis is a facile approach toward improved delivery into KRAS-driven cancers.

Tumor Site-Dependent Transport Properties Determine Nanotherapeutics Delivery and Its Efficacy

Insufficient delivery of systemically administered anticancer drugs to tumors can compromise therapeutic efficacy and develop drug delivery-based therapeutic resistance. Nanotherapeutics such as PEGylated liposomal doxorubicin (PLD) are designed to preferentially accumulate in tumors utilizing enhanced permeation and retention effect. However, their antitumor effects and resulting clinical outcomes are modest and heterogeneous among tumors. Here, we aimed to investigate whether the amount and efficacy of PLD delivered to tumors are tumor site dependent. We established orthotopic primary tumor or liver metastases models of murine breast cancer using 4 T1 cells. PLD showed significant therapeutic effects against tumors that grew in primary mammary sites but not in the liver. We found that differences in therapeutic efficacy were not because of the intrinsic biological resistance of cancer cells but rather were associated with tumor site-dependent differences in transport properties, such as the amount of PLD delivery, blood vessel function, relative vascular permeability, and mechanical pressure in tumors. Thus, transport properties in tumor is site dependent and can be used as phenotypic surrogate markers for tumor drug delivery and therapeutic efficacy.

Harnessing Macrophages for Controlled-Release Drug Delivery: Lessons From Microbes

With the effectiveness of therapeutic agents ever decreasing and the increased incidence of multi-drug resistant pathogens, there is a clear need for administration of more potent, potentially more toxic, drugs. Alternatively, biopharmaceuticals may hold potential but require specialized protection from premature in vivo degradation. Thus, a paralleled need for specialized drug delivery systems has arisen. Although cell-mediated drug delivery is not a completely novel concept, the few applications described to date are not yet ready for in vivo application, for various reasons such as drug-induced carrier cell death, limited control over the site and timing of drug release and/or drug degradation by the host immune system. Here, we present our hypothesis for a new drug delivery system, which aims to negate these limitations. We propose transport of nanoparticle-encapsulated drugs inside autologous macrophages polarized to M1 phenotype for high mobility and treated to induce transient phagosome maturation arrest. In addition, we propose a significant shift of existing paradigms in the study of host-microbe interactions, in order to study microbial host immune evasion and dissemination patterns for their therapeutic utilization in the context of drug delivery. We describe a system in which microbial strategies may be adopted to facilitate absolute control over drug delivery, and without sacrificing the host carrier cells. We provide a comprehensive summary of the lessons we can learn from microbes in the context of drug delivery and discuss their feasibility for in vivo therapeutic application. We then describe our proposed "synthetic microbe drug delivery system" in detail. In our opinion, this multidisciplinary approach may hold the solution to effective, controlled drug delivery.

Targeted delivery of paclitaxel by functionalized selenium nanoparticles for anticancer therapy through ROS-mediated signaling pathways

As a therapeutic anticancer agent, the clinical use of paclitaxel (PTX) is limited by its poor water solubility and serious adverse side effects. The targeted-specific intracellular delivery of an anticancer drug as a new therapeutic modality is promising for cancer treatment. The anticancer activity of selenium nanoparticles (SeNPs) with low toxicity and excellent activity has attracted increasing attention for use in biomedical intervention in recent years. In this study, β-cyclodextrin (β-CD)-folate (FA)-modified selenium nanoparticles (SeNPs) loaded with paclitaxel (PTX) (Se@β-CD-FA@PTX) were successfully fabricated through a layer-by-layer method. The nanosystem is able to enter cancer cells through FA receptor-mediated endocytosis to achieve targeted-specific intracellular delivery. Se@β-CD-FA@PTX was found to increase the selectivity between normal and cancer cells. The viability in MCF-7 cells was remarkably lower than in MCF 10A cells, which may promote the specific targeted delivery of Se@β-CD-FA@PTX into MCF-7 cells. Moreover, Se@β-CD-FA@PTX was found to enhance the cytotoxic effect on MCF-7 cells via the induction of apoptosis activation of ROS-mediated p53 and AKT signaling pathways. The results demonstrate that Se@β-CD-FA@PTX nanoparticles provide a strategy for the design of cancer-targeted nanosystems for use in cancer therapy.

Progression-dependent transport heterogeneity of breast cancer liver metastases as a factor in therapeutic resistance

Metastatic disease is a major cause of mortality in cancer patients. While many drug delivery strategies for anticancer therapeutics have been developed in preclinical studies of primary tumors, the drug delivery properties of metastatic tumors have not been sufficiently investigated. Therapeutic efficacy hinges on efficient drug permeation into the tumor microenvironment, which is known to be heterogeneous thus potentially making drug permeation heterogeneous, also. In this study, we have identified that 4 T1 liver metastases, treated with pegylated liposomal doxorubicin, have unfavorable and heterogeneous transport of doxorubicin. Our drug extravasation results differ greatly from analogous studies with 4 T1 tumors growing in the primary site. A probabilistic tumor population model was developed to estimate drug permeation efficiency and drug kinetics of liver metastases by integrating the transport and structural properties of tumors and delivered drugs. The results demonstrate significant heterogeneity in metastases with regard to transport properties of doxorubicin within the same animal model, and even within the same organ. These results also suggest that the degree of heterogeneity depends on the stage of tumor progression and that differences in transport properties can define transport-based tumor phenotypes. These findings may have valuable clinical implications by illustrating that therapeutic agents can permeate and eliminate metastases of "less resistant" transport phenotypes, while sparing tumors with more "resistant" transport properties. We anticipate that these results could challenge the current paradigm of drug delivery into metastases, highlight potential caveats for therapies that may alter tumor perfusion, and deepen our understanding of the emergence of drug transport-based therapeutic resistance.

Targeting myeloid regulators by paclitaxel-loaded enzymatically degradable nanocups

Tumor microenvironment is characterized by immunosuppressive mechanisms associated with the accumulation of immune regulatory cells - myeloid-derived suppressor cells (MDSC). Therapeutic depletion of MDSC has been associated with inhibition of tumor growth and therefore represents an attractive approach to cancer immunotherapy. MDSC in cancer are characterized by enhanced enzymatic capacity to generate reactive oxygen and nitrogen species (RONS) which have been shown to effectively degrade carbonaceous materials. We prepared enzymatically openable nitrogen-doped carbon nanotube cups (NCNC) corked with gold nanoparticles and loaded with paclitaxel as a therapeutic cargo. Loading and release of paclitaxel was confirmed through electron microscopy, Raman spectroscopy and LC-MS analysis. Under the assumption that RONS generated by MDSCs can be utilized as a dual targeting and oxidative degradation mechanism for NCNC, here we report that systemic administration of paclitaxel loaded NCNC delivers paclitaxel to circulating and lymphoid tissue MDSC resulting in the inhibition of growth of tumors (B16 melanoma cells inoculated into C57BL/6 mice) in vivo. Tumor growth inhibition was associated with decreased MDSC accumulation quantified by flow cytometry that correlated with bio-distribution of gold-corked NCNC resolved by ICP-MS detection of residual gold in mouse tissue. Thus, we developed a novel immunotherapeutic approach based on unique nanodelivery vehicles, which can be loaded with therapeutic agents that are released specifically in MDSC via NCNC selective enzymatic "opening" affecting change in the tumor microenvironment.

Chloroquine and nanoparticle drug delivery: A promising combination

Clinically approved cancer therapies include small molecules, antibodies, and nanoparticles. There has been major progress in the treatment of several cancer types over recent decades. However, many challenges remain for optimal use of conventional and nanoparticle-based therapies in oncology including poor drug delivery, rapid clearance, and drug resistance. The antimalarial agent chloroquine has been found to mitigate some of these challenges by modulating cancer cells and the tissue microenvironment. Particularly, chloroquine was recently found to reduce immunological clearance of nanoparticles by resident macrophages in the liver, leading to increased tumor accumulation of nanodrugs. Additionally, chloroquine has been shown to improve drug delivery and efficacy through normalization of tumor vasculature and suppression of several oncogenic and stress-tolerance pathways, such as autophagy, that protect cancer cells from cytotoxic agents. This review will discuss the use of chloroquine as combination therapy to improve cancer treatment.

Tailoring Porous Silicon for Biomedical Applications: From Drug Delivery to Cancer Immunotherapy

In the past two decades, porous silicon (PSi) has attracted increasing attention for its potential biomedical applications. With its controllable geometry, tunable nanoporous structure, large pore volume/high specific surface area, and versatile surface chemistry, PSi shows significant advantages over conventional drug carriers. Here, an overview of recent progress in the use of PSi in drug delivery and cancer immunotherapy is presented. First, an overview of the fabrication of PSi with various geometric structures is provided, with particular focus on how the unique geometry of PSi facilitates its biomedical applications, especially for drug delivery. Second, surface chemistry and modification of PSi are discussed in relation to the strengthening of its performance in drug delivery and bioimaging. Emerging technologies for engineering PSi-based composites are then summarized. Emerging PSi advances in the context of cancer immunotherapy are also highlighted. Overall, very promising research results encourage further exploration of PSi for biomedical applications, particularly in drug delivery and cancer immunotherapy, and future translation of PSi into clinical applications.

CD44-Targeted Facile Enzymatic Activatable Chitosan Nanoparticles for Efficient Antitumor Therapy and Reversal of Multidrug Resistance

Nanoparticles are attractive platforms for the delivery of various anticancer therapeutics. Nevertheless, their applications are still limited by the relatively low drug loading capacity and the occurrence of multidrug resistance (MDR) against chemotherapeutics. In this study, we report that the integration of d-α-tocopherol succinate (VES) residue with both chitosan and paclitaxel (PTX) led to significant improvement of drug loading capacity and drug loading efficiency through the enhancement of drug/carrier interaction. After the incorporation of hyaluronic acid containing PEG side chains (HA-PEG), higher serum stability and more efficient cellular uptake were obtained. Due to HA coating, VES residues and the enzymatic responsive drug release property, such facile nanoparticles actively targeted cancer cells that overexpress CD44 receptor and efficiently reversed the MDR of treated cells, but caused no significant toxicity to mouse fibroblast (NIH-3T3). More importantly, with HA-PEG coating, longer blood circulation and more effective tumor accumulation were achieved for prodrug nanoparticles. Finally, superior anticancer activity and excellent safety profile was demonstrated by HA-PEG coated enzymatically activatable prodrug nanoparticles compared to commercially available Taxol formulation.

Albumin/vaccine nanocomplexes that assemble in vivo for combination cancer immunotherapy

Subunit vaccines have been investigated in over 1000 clinical trials of cancer immunotherapy, but have shown limited efficacy. Nanovaccines may improve efficacy but have rarely been clinically translated. By conjugating molecular vaccines with Evans blue (EB) into albumin-binding vaccines (AlbiVax), here we develop clinically promising albumin/AlbiVax nanocomplexes that self-assemble in vivo from AlbiVax and endogenous albumin for efficient vaccine delivery and potent cancer immunotherapy. PET pharmacoimaging, super-resolution microscopies, and flow cytometry reveal almost 100-fold more efficient co-delivery of CpG and antigens (Ags) to lymph nodes (LNs) by albumin/AlbiVax than benchmark incomplete Freund's adjuvant (IFA). Albumin/AlbiVax elicits ~10 times more frequent peripheral antigen-specific CD8⁺ cytotoxic T lymphocytes with immune memory than IFA-emulsifying vaccines. Albumin/AlbiVax specifically inhibits progression of established primary or metastatic EG7.OVA, B16F10, and MC38 tumors; combination with anti-PD-1 and/or Abraxane further potentiates immunotherapy and eradicates most MC38 tumors. Albumin/AlbiVax nanocomplexes are thus a robust platform for combination cancer immunotherapy.

Bridging Bio-Nano Science and Cancer Nanomedicine

The interface of bio-nano science and cancer medicine is an area experiencing much progress but also beset with controversy. Core concepts of the field-e.g., the enhanced permeability and retention (EPR) effect, tumor targeting and accumulation, and even the purpose of "nano" in cancer medicine-are hotly debated. In parallel, considerable advances in neighboring fields are occurring rapidly, including the recent progress of "immuno-oncology" and the fundamental impact it is having on our understanding and the clinical treatment of the group of diseases collectively known as cancer. Herein, we (i) revisit how cancer is commonly treated in the clinic and how this relates to nanomedicine; (ii) examine the ongoing debate on the relevance of the EPR effect and tumor targeting; (iii) highlight ways to improve the next-generation of nanomedicines; and (iv) discuss the emerging concept of working with (and not against) biology. While discussing these controversies, challenges, emerging concepts, and opportunities, we explore new directions for the field of cancer nanomedicine.

A chloroquine-induced macrophage-preconditioning strategy for improved nanodelivery

Site-specific localization is critical for improving the therapeutic efficacy and safety of drugs. Nanoparticles have emerged as promising tools for localized drug delivery. However, over 90% of systemically injected nanocarriers typically accumulate in the liver and spleen due to resident macrophages that form the mononuclear phagocyte system. In this study, the clinically approved antimalarial agent chloroquine was shown to reduce nanoparticle uptake in macrophages by suppressing endocytosis. Pretreatment of mice with a clinically relevant dose of chloroquine substantially decreased the accumulation of liposomes and silicon particles in the mononuclear phagocyte system and improved tumoritropic and organotropic delivery. The novel use of chloroquine as a macrophage-preconditioning agent presents a straightforward approach for addressing a major barrier in nanomedicine. Moreover, this priming strategy has broad applicability for improving the biodistribution and performance of particulate delivery systems. Ultimately, this study defines a paradigm for the combined use of macrophage-modulating agents with nanotherapeutics for improved site-specific delivery.

Bioreducible Hydrophobin-Stabilized Supraparticles for Selective Intracellular Release

One of the main hurdles in nanomedicine is the low stability of drug-nanocarrier complexes as well as the drug delivery efficiency in the region-of-interest. Here, we describe the use of the film-forming protein hydrophobin HFBII to organize dodecanethiol-protected gold nanoparticles (NPs) into well-defined supraparticles (SPs). The obtained SPs are exceptionally stable in vivo and efficiently encapsulate hydrophobic drug molecules. The HFBII film prevents massive release of the encapsulated drug, which, instead, is activated by selective SP disassembly triggered intracellularly by glutathione reduction of the protein film. As a consequence, the therapeutic efficiency of an encapsulated anticancer drug is highly enhanced (2 orders of magnitude decrease in IC₅₀). Biodistribution and pharmacokinetics studies demonstrate the high stability of the loaded SPs in the bloodstream and the selective release of the payloads once taken up in the tissues. Overall, our results provide a rationale for the development of bioreducible and multifunctional nanomedicines.

Complex effects of tumor microenvironment on the tumor disposition of carrier-mediated agents

Major advances in carrier-mediated agents, including nanoparticle, conjugates and antibody-drug conjugates, have created revolutionary drug delivery systems in cancer over the past two decades. While these agents provide several advantages, such as greater duration of exposure and solubility, compared with their small-molecule counterparts, there is substantial variability in delivery of these agents to tissues and especially tumors. This review provides an overview of tumor microenvironment factors that affect the pharmacokinetics and pharmacodynamics of carrier-mediated agents observed in preclinical models and patients.

Gemcitabine enhances the transport of nanovector-albumin-bound paclitaxel in gemcitabine-resistant pancreatic ductal adenocarcinoma

The mechanism for improved therapeutic efficacy of the combination therapy with nanoparticle albumin-bound paclitaxel (nAb-PTX) and gemcitabine (gem) for pancreatic ductal adenocarcinoma (PDAC) has been ascribed to enhanced gem transport by nAb-PTX. Here, we used an orthotopic mouse model of gem-resistant human PDAC in which increasing gem transport would not improve the efficacy, thus revealing the importance of nAb-PTX transport. We aimed to evaluate therapeutic outcomes and transport of nAb-PTX to PDAC as a result of (1) encapsulating nAb-PTX in multistage nanovectors (MSV); (2) effect of gem on caveolin-1 expression. Treatment with MSV/nAb-PTX + gem was highly efficient in prolonging animal survival in comparison to other therapeutic regimens. MSV/nAb-PTX + gem also caused a substantial increase in tumor PTX accumulation, significantly reduced tumor growth and tumor cell proliferation, and increased apoptosis. Moreover, gem enhanced caveolin-1 expression in vitro and in vivo, thereby improving transport of nAb-PTX to PDAC. This data was confirmed by analysis of PDACs from patients who received gem-based neo-adjuvant chemotherapy. In conclusion, we found that nAb-PTX treatment of gem-resistant PDAC can be enhanced by (1) gem through up-regulation of caveolin-1 and (2) MSV through increasing accumulation of nAb-PTX in the tumor.

Albumin and Hyaluronic Acid-Coated Superparamagnetic Iron Oxide Nanoparticles Loaded with Paclitaxel for Biomedical Applications

Super paramagnetic iron oxide nanoparticles (SPION) were augmented by both hyaluronic acid (HA) and bovine serum albumin (BSA), each covalently conjugated to dopamine (DA) enabling their anchoring to the SPION. HA and BSA were found to simultaneously serve as stabilizing polymers of Fe₃O₄·DA-BSA/HA in water. Fe₃O₄·DA-BSA/HA efficiently entrapped and released the hydrophobic cytotoxic drug paclitaxel (PTX). The relative amount of HA and BSA modulates not only the total solubility but also the paramagnetic relaxation properties of the preparation. The entrapping of PTX did not influence the paramagnetic relaxation properties of Fe₃O₄·DA-BSA. Thus, by tuning the surface structure and loading, we can tune the theranostic properties of the system.

Macrophage Polarization Contributes to the Anti-Tumoral Efficacy of Mesoporous Nanovectors Loaded with Albumin-Bound Paclitaxel

Therapies targeted to the immune system, such as immunotherapy, are currently shaping a new, rapidly developing branch of promising cancer treatments, offering the potential to change the prognosis of previously non-responding patients. Macrophages comprise the most abundant population of immune cells in the tumor microenvironment (TME) and can undergo differentiation into functional phenotypes depending on the local tissue environment. Based on these functional phenotypes, tumor-associated macrophages (TAMs) can either aid tumor progression (M2 phenotype) or inhibit it (M1 phenotype). Presence of M2 macrophages and a high ratio of M2/M1 macrophages in the TME are clinically associated with poor prognosis in many types of cancers. Herein, we evaluate the effect of macrophage phenotype on the transport and anti-cancer efficacy of albumin-bound paclitaxel (nAb-PTX) loaded into porous silicon multistage nanovectors (MSV). Studies in a coculture of breast cancer cells (3D-spheroid) with macrophages and in vivo models were conducted to evaluate the therapeutic efficacy of MSV-nAb-PTX as a function of macrophage phenotype. Association with MSV increased drug accumulation within the macrophages and the tumor spheroids, shifting the inflammation state of the TME toward the pro-inflammatory, anti-tumorigenic milieu. Additionally, the treatment increased macrophage motility toward cancer cells, promoting the active transport of therapeutic nanovectors into the tumor lesion. Consequently, apoptosis of cancer cells was increased and proliferation decreased in the MSV-nAb-PTX-treated group as compared to controls. The results also confirmed that the tested system shifts the macrophage differentiation toward an M1 phenotype, possessing an anti-proliferative effect toward the breast cancer cells. These factors were further incorporated into a mathematical model to help analyze the synergistic effect of the macrophage polarization state on the efficacy of MSV-nAb-PTX in alleviating hypovascularized tumor lesions. In conclusion, the ability of MSV-nAb-PTX to polarize TAM to the M1 phenotype, causing (1) enhanced penetration of the drug-carrying macrophages to the center of the tumor lesion and (2) increased toxicity to tumor cells may explain the increased anti-cancer efficacy of the system in comparison to nAb-PTX and other controls.

Tumor progression effects on drug vector access to tumor-associated capillary bed

Over the last decade, the benefits of drug vectors to treat cancer have been well recognized. However, drug delivery and vector distribution differences in tumor-associated capillary bed at different stages of disease progression are not well understood. To obtain further insights into drug vector distribution changes in vasculature during tumor progression, we combined intra-vital imaging of metastatic tumors in mice, microfluidics-based artificial tumor capillary models, and Computational Fluid Dynamics (CFD) modeling. Microfluidic and CFD circulation models were designed to mimic tumor progression by escalating flow complexity and chaoticity. We examined flow of 0.5 and 2μm spherical particles, and tested the effects of hematocrit on particle local accessibility to flow area of capillary beds by co-circulating red blood cells (RBC). Results showed that tumor progression modulated drug vector distribution in tumor-associated capillaries. Both particles shared 80-90% common flow area, while 0.5 and 2μm particles had 2-9% and 1-2% specific flow area, respectively. Interestingly, the effects of hematocrit on specific circulation area was opposite for 0.5 and 2μm particles. Dysfunctional capillaries with no flow, a result of tumor progression, limited access to all particles, while diffusion was shown to be the only prevailing transport mechanism. In view of drug vector distribution in tumors, independent of formulation and other pharmacokinetic aspects, our results suggest that the evolution of tumor vasculature during progression may influence drug delivery efficiency. Therefore, optimized drug vectors will need to consider primary vs metastatic tumor setting, or early vs late stage metastatic disease, when undergoing vector design.

Progress in tumor-associated macrophage (TAM)-targeted therapeutics

As an essential innate immune population for maintaining body homeostasis and warding off foreign pathogens, macrophages display high plasticity and perform diverse supportive functions specialized to different tissue compartments. Consequently, aberrance in macrophage functions contributes substantially to progression of several diseases including cancer, fibrosis, and diabetes. In the context of cancer, tumor-associated macrophages (TAMs) in tumor microenvironment (TME) typically promote cancer cell proliferation, immunosuppression, and angiogenesis in support of tumor growth and metastasis. Oftentimes, the abundance of TAMs in tumor is correlated with poor disease prognosis. Hence, significant attention has been drawn towards development of cancer immunotherapies targeting these TAMs; either depleting them from tumor, blocking their pro-tumoral functions, or restoring their immunostimulatory/tumoricidal properties. This review aims to introduce readers to various aspects in development and evaluation of TAM-targeted therapeutics in pre-clinical and clinical stages.