Targeting tumor stroma and exploiting mature tumor vasculature to improve anti-cancer drug delivery

Cell-mediated barriers in cancer immunosurveillance

The immune cells within the tumor microenvironment (TME) exert multifaceted functions ranging from tumor-antagonizing or tumor-promoting activities. During the initial phases of tumor development, the tumor-antagonizing immune cells in the TME combat cancer cells in an immune surveillance process. However, with time, cancer cells can evade detection and impede the immune cells' effectiveness through diverse mechanisms, such as decreasing immunogenic antigen presentation on their surfaces and/or secreting anti-immune factors that cause tolerance in TME. Moreover, some immune cells cause immunosuppressive situations and inhibit antitumoral immune responses. Physical and cellular-mediated barriers in the TME, such as cancer-associated fibroblasts, tumor endothelium, the altered lipid composition of tumor cells, and exosomes secreted from cancer cells, also mediate immunosuppression and prevent extravasation of immune cells. Due to successful clinical outcomes of cancer treatment strategies the potential barriers must be identified and addressed. We need to figure out how to optimize cancer immunotherapy strategies, and how to combine therapeutic approaches for maximum clinical benefit. This review provides a detailed overview of various cells and molecules in the TME, their association with escaping from immune surveillance, therapeutic targets, and future perspectives for improving cancer immunotherapy.

A review of chitosan in gene therapy: Developments and challenges

Gene therapy, as a revolutionary treatment, has been gaining more and more attention. The key to gene therapy is the selection of suitable vectors for protection of exogenous nucleic acid molecules and enabling their specific release in target cells. While viral vectors have been widely used in researches, non-viral vectors are receiving more attention due to its advantages. Chitosan (CS) has been widely used as non-viral organic gene carrier because of its good biocompatibility and its ability to load large amounts of nucleic acids. This paper summarizes and evaluates the potential of chitosan and its derivatives as gene delivery vector materials, along with factors influencing transfection efficiency, performance evaluation, ways to optimize infectious efficiency, and the current main research development directions. Additionally, it provides an outlook on its future prospects.

Systemic Alterations in Type-2 Conventional Dendritic Cells Lead to Impaired Tumor Immunity in Pancreatic Cancer

Intratumoral T-cell dysfunction is a hallmark of pancreatic tumors, and efforts to improve dendritic cell (DC)-mediated T-cell activation may be critical in treating these immune therapy unresponsive tumors. Recent evidence indicates that mechanisms that induce dysfunction of type 1 conventional DCs (cDC1) in pancreatic adenocarcinomas (PDAC) are drivers of the lack of responsiveness to checkpoint immunotherapy. However, the impact of PDAC on systemic type 2 cDC2 development and function has not been well studied. Herein, we report the analysis of 3 cohorts, totaling 106 samples, of human blood and bone marrow (BM) from patients with PDAC for changes in cDCs. We found that circulating cDC2s and their progenitors were significantly decreased in the blood of patients with PDAC, and repressed numbers of cDC2s were associated with poor prognosis. Serum cytokine analyses identified IL6 as significantly elevated in patients with PDAC and negatively correlated with cDC numbers. In vitro, IL6 impaired the differentiation of cDC1s and cDC2s from BM progenitors. Single-cell RNA sequencing analysis of human cDC progenitors in the BM and blood of patients with PDAC showed an upregulation of the IL6/STAT3 pathway and a corresponding impairment of antigen processing and presentation. These results suggested that cDC2s were systemically suppressed by inflammatory cytokines, which was linked to impaired antitumor immunity.

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.

Low-intensity focused ultrasound targeted microbubble destruction reduces tumor blood supply and sensitizes anti-PD-L1 immunotherapy

Immune checkpoint blockade (ICB) typified by anti-PD-1/PD-L1 antibodies as a revolutionary treatment for solid malignancies has been limited to a subset of patients due to poor immunogenicity and inadequate T cell infiltration. Unfortunately, no effective strategies combined with ICB therapy are available to overcome low therapeutic efficiency and severe side effects. Ultrasound-targeted microbubble destruction (UTMD) is an effective and safe technique holding the promise to decrease tumor blood perfusion and activate anti-tumor immune response based on the cavitation effect. Herein, we demonstrated a novel combinatorial therapeutic modality combining low-intensity focused ultrasound-targeted microbubble destruction (LIFU-TMD) with PD-L1 blockade. LIFU-TMD caused the rupture of abnormal blood vessels to deplete tumor blood perfusion and induced the tumor microenvironment (TME) transformation to sensitize anti-PD-L1 immunotherapy, which markedly inhibited 4T1 breast cancer's growth in mice. We discovered immunogenic cell death (ICD) in a portion of cells induced by the cavitation effect from LIFU-TMD, characterized by the increased expression of calreticulin (CRT) on the tumor cell surface. Additionally, flow cytometry revealed substantially higher levels of dendritic cells (DCs) and CD8⁺ T cells in draining lymph nodes and tumor tissue, as induced by pro-inflammatory molecules like IL-12 and TNF-α. These suggest that LIFU-TMD as a simple, effective, and safe treatment option provides a clinically translatable strategy for enhancing ICB therapy.

Prediction the clinical EPR effect of nanoparticles in patient-derived xenograft models

Many preclinically tested nanoparticles in existing animal models fail to be directly translated into clinical applications because of their poor resemblance to human cancer. Herein, the enhanced permeation and retention (EPR) effect of glycol chitosan nanoparticles (CNPs) in different tumor microenvironments (TMEs) was compared using different pancreatic tumor models, including pancreatic cancer cell line (BxPC3), patient-derived cancer cell (PDC), and patient-derived xenograft (PDX) models. CNPs were intravenously injected into different tumor models, and their accumulation efficiency was evaluated using non-invasive near-infrared fluorescence (NIRF) imaging. In particular, differences in angiogenic vessel density, collagen matrix, and hyaluronic acid content in tumor tissues of the BxPC3, PDC, and PDX models greatly affected the tumor-targeting efficiency of CNPs. In addition, different PDX models were established using different tumor tissues of patients to predict the clinical EPR effect of CNPs in inter-patient TMEs, wherein the gene expression levels of PECAM1, COL4A1, and HAS1 in human tumor tissues were observed to be closely related to the EPR effect of CNPs in PDX models. The results suggested that the PDX models could mimic inter-patient TMEs with different blood vessel structures and extracellular matrix (ECM) content that critically affect the tumor-targeting ability of CNPs in different pancreatic PDX models. This study provides a better understanding of the heterogeneity and complexity of inter-patient TMEs that can predict the response of various nanoparticles in individual tumors for personalized cancer therapy.

Strategies for active tumor targeting-an update

A complete cure for cancer is still the holy grail for scientists. The existing treatment of cancer is primarily focused on surgery, radiation and conventional chemotherapy. However, chemotherapeutic agents also affect healthy tissues or organs due to a lack of specificity. While passive targeting is studied for anticancer drugs focused on the enhanced permeability and retention effect, it failed to achieve drug accumulation at the tumor site and desired therapeutic efficacy. This review presents an outline of the current significant targets for active tumor drug delivery systems and provides insight into the direction of active tumor-targeting strategies. For this purpose, a systematic understanding of the physiological factors, tumor microenvironment and its components, overexpressed receptor and associated proteins are covered here. We focused on angiogenesis mediated targeting, receptor-mediated targeting and peptide targeting. This active targeting along with integration with nano delivery systems helps in achieving specific action, thus reducing the associated adverse effects to healthy tissues. Although the tumor-targeting methods and possibilities explored so far seem revolutionary in cancer treatment, in-depth clinical studies data is required for its commercial translation.

Deregulated glutamate to pro-collagen conversion is associated with adverse outcome in lung cancer and may be targeted by renin-angiotensin-aldosterone system (RAS) inhibition

BACKGROUND

The tumor-microenvironment (TME) represents an attractive therapeutic target in NSCLC and plays an important role for efficacy of cancer therapeutics. We hypothesized that upregulation of collagen synthesis might be associated with adverse outcome in NSCLC. Literature evidence suggests that renin-angiotensin system inhibitors (RASi) decrease collagen deposition. Therefore, we aimed to explore the prognostic role of RASi intake and their influence on the TME in NSCLC.

METHODS

Four publicly available datasets were used to evaluate the impact of key enzymes involved in collagen biosynthesis. To investigate the influence of RASi intake on the TME and prognosis we evaluated a cohort of metastatic NSCLC patients and performed histopathological characterization of the TME. A three-dimensional microtissue in vitro model was developed to define the impact of RASi on collagen synthesis.

RESULTS

Expression of three genes of the collagen synthesis pathway, ALDH18A1, PLOD2 and P4HA1, was upregulated in NSCLC compared to normal lung tissue and linked to shortened overall survival in all investigated cohorts. Together, these genes formed a 'Collagen Signature' which represents an independent unfavourable prognostic factor in two NSCLC cohorts and was linked to alterations of the extracellular matrix deposition and cell cycle pathways. In the cohort of metastatic NSCLC, RASi intake was linked to improved overall response rate and survival. Exploratory in vitro experiments revealed that RASi led to a dose dependent reduction of collagen deposition and degradation of three-dimensional lung cancer cell spheroids.

CONCLUSION

We demonstrate that collagen synthesis is a key upregulated process in the NSCLC TME and its transcriptional readout, the three gene Collagen Signature is independently associated with poor outcome. Pharmacological targeting of this pathways e.g. by RASi bears potential of improving outcome in NSCLC.

Effect of a 2-HP-β-Cyclodextrin Formulation on the Biological Transport and Delivery of Chemotherapeutic PLGA Nanoparticles

Background

The aim of this work was to develop a novel and feasible modification strategy by utilizing the supramolecular effect of 2-hydroxypropyl-beta-cyclodextrin (2-HP-β-CD) for enhancing the biological transport efficiency of paclitaxel (PTX)-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles.

Methods

PTX-loaded 2-HP-β-CD-modified PLGA nanoparticles (2-HP-β-CD/PLGA NPs) were prepared using the modified emulsion method. Nano-characteristics, drug release behavior, in vitro cytotoxicity, cellular uptake profiles and in vivo bio-behavior of the nanoparticles were then characterized.

Results

Compared with the plain PLGA NPs, 2-HP-β-CD/PLGA NPs exhibited smaller particle sizes (151.03±1.36 nm), increased entrapment efficiency (~49.12% increase) and sustained drug release. When added to A549 human lung cancer cells, compared with PLGA NPs, 2-HP-β-CD/PLGA NPs exhibited higher cytotoxicity in MTT assays and improved cellular uptake efficiency. Pharmacokinetic analysis showed that the AUC value of 2-HP-β-CD/PLGA NPs was 2.4-fold higher than commercial Taxol^® and 1.7-fold higher than plain PLGA NPs. In biodistribution assays, 2-HP-β-CD/PLGA NPs exhibited excellent stability in the circulation.

Conclusion

The results of this study suggest that the formulation that contains 2-HP-β-CD can prolong PTX release, enhance drug transport efficiency and serve as a potential tumor targeting system for PTX.

Surface-modified polymeric nanoparticles for drug delivery to cancer cells

INTRODUCTION

The utilization of polymeric nanoparticles, as drug payloads, has been extensively prevailed in cancer therapy. However, the precise distribution of these nanocarriers is restrained by various physiological and cellular obstacles. Nanoparticles must avoid nonspecific interactions with healthy cells and in vivo compartments to circumvent these barriers. Since in vivo interactions of nanoparticles are mainly dependent on surface properties of nanoparticles, efficient control on surface constituents is necessary for the determination of nanoparticles' fate in the body.

AREAS COVERED

In this review, the surface-modified polymeric nanoparticles and their utilization in cancer treatment were elaborated. First, the interaction of nanoparticles with numerous in vivo barriers was highlighted. Second, different strategies to overcome these obstacles were described. Third, some inspiring examples of surface-modified nanoparticles were presented. Later, fabrication and characterization methods of surface-modified nanoparticles were discussed. Finally, the applications of these nanoparticles in different routes of treatments were explored.

EXPERT OPINION

Surface modification of anticancer drug-loaded polymeric nanoparticles can enhance the efficacy, selective targeting, and biodistribution of the anticancer drug at the tumor site.

Antifibrotic therapy to normalize the tumor microenvironment

Most tumors develop abnormal fibrotic regions consisting of fibroblasts, immune cells, and a dense extracellular matrix (ECM) immersed in a viscous interstitial fluid, and an abundant fibrotic tumor microenvironment (TME) is associated with poor outcome of treatment. It has been hypothesized that the treatment of cancer may be improved by interventions aiming to normalize this TME. The approaches used in attempts to normalize the fibrotic TME can be categorized into three strategies of targeted antifibrotic therapy: targeting of components of the ECM, targeting of the producers of the ECM components-the activated cancer-associated fibroblasts (CAFs), and targeting of the signaling pathways activating CAFs. To target the ECM, enzymes against components of the ECM have been used, including collagenase, relaxin, hyaluronidase, and lyxyl oxidase. Targeting of CAFs have been investigated by using agents aiming to eliminate or reprogram CAFs. CAFs are activated primarily by transforming growth factor-β (TGF-β), hedgehog, or focal adhesion kinase signaling, and several agents have been used to target these signaling pathways, including angiotensin II receptor I blockers (e.g., losartan) to inhibit the TGF-β pathway. Taken together, these studies have revealed that antifibrotic therapy is a two-edged sword: while some studies suggest enhanced response to treatment after antifibrotic therapy, others suggest that antifibrotic therapy may lead to increased tumor growth, metastasis, and impaired outcome of treatment. There are several possible explanations of these conflicting observations. Most importantly, tumors contain different subpopulations of CAFs, and while some subpopulations may promote tumor growth and metastasis, others may inhibit malignant progression. Furthermore, the outcome of antifibrotic therapy may depend on stage of disease, duration of treatment, treatment-induced activation of alternative profibrotic signaling pathways, and treatment-induced recruitment of tumor-supporting immune cells. Nevertheless, losartan-induced suppression of TGF-β signaling appears to be a particularly promising strategy. Losartan is a widely prescribed antihypertensive drug and highly advantageous therapeutic effects have been observed after losartan treatment of pancreatic cancer. However, improved understanding of the mechanisms governing the development of fibrosis in tumors is needed before safe antifibrotic treatments can be established.

Nanoparticles' interactions with vasculature in diseases

The ever-growing use of inorganic nanoparticles (NPs) in biomedicine provides an exciting approach to develop novel imaging and drug delivery systems, owing to the ease with which these NPs can be functionalized to cater to various applications. In cancer therapeutics, nanomedicine generally relies on the enhanced permeability and retention (EPR) effect observed in tumour vasculature to deliver anti-cancer drugs across the endothelium. However, such a phenomenon is dependent on the tumour microenvironment and is not consistently observed in all tumour types, thereby limiting drug transport to the tumour site. On the other hand, there is a rise in utilizing inorganic NPs to intentionally induce endothelial leakiness, creating a window of opportunity to control drug delivery across the endothelium. While this active targeting approach creates a similar phenomenon compared to the EPR effect arising from tumour tissues, its drug delivery applications extend beyond cancer therapeutics and into other vascular-related diseases. In this review, we summarize the current findings of the EPR effect and assess its limitations in the context of anti-cancer drug delivery systems. While the EPR effect offers a possible route for drug passage, we further explore alternative uses of NPs to create controllable endothelial leakiness within short exposures, a phenomenon we coined as nanomaterial-induced endothelial leakiness (NanoEL). Furthermore, we discuss the main mechanistic features of the NanoEL effect that make it unique from conventionally established endothelial leakiness in homeostatic and pathologic conditions, as well as examine its potential applicability in vascular-related diseases, particularly cancer. Therefore, this new paradigm changes the way inorganic NPs are currently being used for biomedical applications.

Codelivery Nanosystem Targeting the Deep Microenvironment of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is considered as one of the most aggressive malignancies due to its unique microenvironment of which the cardinal histopathological feature is the remarkable desmoplasia of the stroma, taking up about 80% of the tumor mass. The desmoplastic stroma negatively affects drug diffusion and the infiltration of T cells, leading to an immunosuppressive microenvironment. However, this unique microenvironment can limit the physical spread of pancreatic cancer via a neighbor suppression effect. Here, a tumor central stroma targeting and microenvironment responsive strategy was applied to generate a nanoparticle coloading paclitaxel and phosphorylated gemcitabine. The designed nanoparticle disrupted the central stroma while preserving the external stroma, thereby promoting the antitumor effectiveness of chemotherapeutics. Additionally, the resulting nanoparticle can modulate the tumor immunosuppressive microenvironment by augmenting the number of cytotoxic T cells and restraining the percentage of T regulatory cells. The relatively intact external stroma can effectively maintain the neighbor suppression effect and prevent tumor metastasis. Combining stroma targeting with the delivery of stimuli-responsive polymeric nanoparticles embodies an effective tumor-tailored drug delivery system.

AF1q inhibited T cell attachment to breast cancer cell by attenuating Intracellular Adhesion Molecule-1 expression

Aim:

To investigate whether AF1q, overexpressed in metastatic cells compared with the primary tumor cells, plays a pivotal role in breast cancer metastasis.

Methods:

To investigate whether AF1q has a responsibility in the acquisition of a metastatic phenotype, we performed RNA-sequencing (RNA-Seq) to identify the gene signature and applied the Metacore direct interactions network building algorithm with the top 40 amplicons of RNA-Seq.

Results:

Most genes were directly linked with intercellular adhesion molecule-1 (ICAM-1). Likewise, we identified that ICAM-1 expression is attenuated in metastatic cells compared to primary tumor cells. Moreover, overexpression of AF1q attenuated ICAM-1 expression, whereas suppression of AF1q elicited the opposite effect. AF1q had an effect on ICAM-1 promoter region and regulated its transcription. Decreased ICAM-1 expression affected the attachment of T cells to a breast cancer cell monolayer. We confirmed the finding by performing the analysis on Burkitt’s lymphoma.

Conclusion:

Attenuation of ICAM-1 by AF1q on tumor cells disadvantages host anti-tumor defenses through the trafficking of lymphocytes, which affects tumor progression and metastasis.

Mechanisms regulating T-cell infiltration and activity in solid tumors

T-lymphocytes play a critical role in cancer immunity as evidenced by their presence in resected tumor samples derived from long-surviving patients, and impressive clinical responses to various immunotherapies that reinvigorate them. Indeed, tumors can upregulate a wide array of defense mechanisms, both direct and indirect, to suppress the ability of Tcells to reach the tumor bed and mount curative responses upon infiltration. In addition, patient and tumor genetics, previous antigenic experience, and the microbiome, are all important factors in shaping the T-cell repertoire and sensitivity to immunotherapy. Here, we review the mechanisms that regulate T-cell homing, infiltration, and activity within the solid tumor bed. Finally, we summarize different immunotherapies and combinatorial treatment strategies that enable the immune system to overcome barriers for enhanced tumor control and improved patient outcome.

Systematic review on the efficacy and safety of immune checkpoint inhibition in renal cell carcinoma

To perform a systematic review of the relevant literature about clinical trials on efficacy and safety of immune checkpoint inhibition, whether it is used alone, in combination or with other targeted therapies in patients with advanced and metastatic renal cell carcinoma (RCC), two team members reviewed the abstracts and selected pertinent articles from the relevant databases. A narrative review of randomized controlled trials was performed and seven randomized controlled trials were identified in this systematic review. In treatment of RCC, nivolumab has superior efficacy and safety compared with second-line everolimus. Combination strategies, especially those combined with anti-VEGF agents presents better efficacy but worse outcomes in term of safety than monotherapy and conventional treatment and might guide treatment choice for patients with RCC.

Inhibition of ROCK1 kinase modulates both tumor cells and stromal fibroblasts in pancreatic cancer

ROCK, or Rho-associated coiled coil-containing protein kinase, is a member of the AGC kinase family and has been shown to play a role in cell migration, ECM synthesis, stress-fiber assembly, and cell contraction. Increased ROCK expression has been reported in multiple pathological conditions, including cancer. Here, we report increased expression of ROCK 1 in pancreatic tumor epithelial cells as well as in cancer associated fibroblasts (CAF). In our analysis, 62% of tumor samples exhibited ≥2+ in staining intensity by IHC analysis, versus 40% of adjacent normal tissue samples (P<0.0001). Thus, we hypothesized that ROCKs may play a significant role in pancreatic cancer progression, and may serve as a suitable target for treatment. We report a low frequency (4/34) amplification of the ROCK1 gene locus at chromosome 18q11.1 in pancreatic ductal adenocarcinoma (PDAC) patient tissue samples by aCGH analysis. Inhibition of ROCK kinase activity by a small molecule inhibitor (fasudil) resulted in moderate (IC50s of 6-71 μM) inhibition of PDAC cell proliferation, migration, and activation of co-cultured stellate cells. In the KPC mouse model for pancreatic cancer, fasudil decreased tumor collagen deposition. This translated to an enhanced overall survival of the mice and an increase in gemcitabine uptake. Though fasudil may target both the tumor epithelial cells and the CAFs, our findings are consistent with the hypothesis that inhibition of tumor stroma enhances drug penetration and efficacy in PDAC. Overall, our data suggests that ROCK1 may serve as a potential therapeutic target to enhance current treatment regimens for pancreatic cancer.

Potential Development of Tumor-Targeted Oral Anti-Cancer Prodrugs: Amino Acid and Dipeptide Monoester Prodrugs of Gemcitabine

One of the main obstacles for cancer therapies is to deliver medicines effectively to target sites. Since stroma cells are developed around tumors, chemotherapeutic agents have to go through stroma cells in order to reach tumors. As a method to improve drug delivery to the tumor site, a prodrug approach for gemcitabine was adopted. Amino acid and dipeptide monoester prodrugs of gemcitabine were synthesized and their chemical stability in buffers, resistance to thymidine phosphorylase and cytidine deaminase, antiproliferative activity, and uptake/permeability in HFF cells as a surrogate to stroma cells were determined and compared to their parent drug, gemcitabine. The activation of all gemcitabine prodrugs was faster in pancreatic cell homogenates than their hydrolysis in buffer, suggesting enzymatic action. All prodrugs exhibited great stability in HFF cell homogenate, enhanced resistance to glycosidic bond metabolism by thymidine phosphorylase, and deamination by cytidine deaminase compared to their parent drug. All gemcitabine prodrugs exhibited higher uptake in HFF cells and better permeability across HFF monolayers than gemcitabine, suggesting a better delivery to tumor sites. Cell antiproliferative assays in Panc-1 and Capan-2 pancreatic ductal cell lines indicated that the gemcitabine prodrugs were more potent than their parent drug gemcitabine. The transport and enzymatic profiles of gemcitabine prodrugs suggest their potential for delayed enzymatic bioconversion and enhanced resistance to metabolic enzymes, as well as for enhanced drug delivery to tumor sites, and cytotoxic activity in cancer cells. These attributes would facilitate the prolonged systemic circulation and improved therapeutic efficacy of gemcitabine prodrugs.

Lipid-Based Drug Delivery Systems in Cancer Therapy: What Is Available and What Is Yet to Come

Cancer is a leading cause of death in many countries around the world. However, the efficacy of current standard treatments for a variety of cancers is suboptimal. First, most cancer treatments lack specificity, meaning that these treatments affect both cancer cells and their normal counterparts. Second, many anticancer agents are highly toxic, and thus, limit their use in treatment. Third, a number of cytotoxic chemotherapeutics are highly hydrophobic, which limits their utility in cancer therapy. Finally, many chemotherapeutic agents exhibit short half-lives that curtail their efficacy. As a result of these deficiencies, many current treatments lead to side effects, noncompliance, and patient inconvenience due to difficulties in administration. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems known commonly as nanoparticles. Among these delivery systems, lipid-based nanoparticles, particularly liposomes, have shown to be quite effective at exhibiting the ability to: 1) improve the selectivity of cancer chemotherapeutic agents; 2) lower the cytotoxicity of anticancer drugs to normal tissues, and thus, reduce their toxic side effects; 3) increase the solubility of hydrophobic drugs; and 4) offer a prolonged and controlled release of agents. This review will discuss the current state of lipid-based nanoparticle research, including the development of liposomes for cancer therapy, different strategies for tumor targeting, liposomal formulation of various anticancer drugs that are commercially available, recent progress in liposome technology for the treatment of cancer, and the next generation of lipid-based nanoparticles.

Tumor resistance to vascular disrupting agents: mechanisms, imaging, and solutions

The emergence of vascular disrupting agents (VDAs) is a significant advance in the treatment of solid tumors. VDAs induce rapid and selective shutdown of tumor blood flow resulting in massive necrosis. However, a viable marginal tumor rim always remains after VDA treatment and is a major cause of recurrence. In this review, we discuss the mechanisms involved in the resistance of solid tumors to VDAs. Hypoxia, tumor-associated macrophages, and bone marrow-derived circulating endothelial progenitor cells all may contribute to resistance. Resistance can be monitored using magnetic resonance imaging markers. The various solutions proposed to manage tumor resistance to VDAs emphasize combining these agents with other approaches including antiangiogenic agents, chemotherapy, radiotherapy, radioimmunotherapy, and sequential dual-targeting internal radiotherapy.

Polyethylene sebacate doxorubicin nanoparticles: role of carbohydrate anchoring on in vitro and in vivo anticancer efficacy

We report carbohydrate-anchored polyethylene sebacate (PES)-Gantrez® AN 119 Doxorubicin hydrochloride (Dox) nanoparticles (NPs) for enhanced anticancer efficacy. The carbohydrates Arabinogalactan (AGn), an adjuvant in anticancer chemotherapy and pullulan (Pul) reported to promote collagen synthesis, were selected as ligands. PES Dox NPs of an average size around 200 nm, greater than 20% w/w Dox loading and negative zeta potential were anchored with Pul, AGn, and Pul-AGn combination by simple incubation. Increase in particle size and zeta potential confirmed carbohydrate anchoring. FTIR confirmed ionic complexation of Dox and Gantrez® AN 119. DSC and XRD demonstrated amorphization of Dox. Higher Dox release in pH 5.5 as compared with pH 7.4 is beneficial for reduced systemic toxicity and enhanced drug release in tumors. Good in vitro serum stability and low hemolysis revealed suitability for intravenous administration. All NPs revealed circulation longevity in normal rats. Pul NPs revealed superior anticancer efficacy in vitro and an 11-fold enhancement in uptake in MCF-7 breast cancer cells. The greater efficacy in vivo is attributed to possible pullulan-mediated integrin receptor uptake and interaction with tumor collagen. Histopathology confirmed safety and suggested promise of Pul NPs in improved anticancer efficacy.

Overview of Methods for Overcoming Hindrance to Drug Delivery to Tumors, with Special Attention to Tumor Interstitial Fluid

Every drug used to treat cancer (chemotherapeutics, immunological, monoclonal antibodies, nanoparticles, radionuclides) must reach the targeted cells through the tumor environment at adequate concentrations, in order to exert their cell-killing effects. For any of these agents to reach the goal cells, they must overcome a number of impediments created by the tumor microenvironment (TME), beginning with tumor interstitial fluid pressure (TIFP), and a multifactorial increase in composition of the extracellular matrix (ECM). A primary modifier of TME is hypoxia, which increases the production of growth factors, such as vascular endothelial growth factor and platelet-derived growth factor. These growth factors released by both tumor cells and bone marrow recruited myeloid cells form abnormal vasculature characterized by vessels that are tortuous and more permeable. Increased leakiness combined with increased inflammatory byproducts accumulates fluid within the tumor mass (tumor interstitial fluid), ultimately creating an increased pressure (TIFP). Fibroblasts are also up-regulated by the TME, and deposit fibers that further augment the density of the ECM, thus, further worsening the TIFP. Increased TIFP with the ECM are the major obstacles to adequate drug delivery. By decreasing TIFP and ECM density, we can expect an associated rise in drug concentration within the tumor itself. In this overview, we will describe all the methods (drugs, nutraceuticals, and physical methods of treatment) able to lower TIFP and to modify ECM used for increasing drug concentration within the tumor tissue.

Targeting the tumor vasculature to enhance T cell activity

T cells play a critical role in tumor immune surveillance as evidenced by extensive mouse-tumor model studies as well as encouraging patient responses to adoptive T cell therapies and dendritic cell vaccines. It is well established that the interplay of tumor cells with their local cellular environment can trigger events that are immunoinhibitory to T cells. More recently it is emerging that the tumor vasculature itself constitutes an important barrier to T cells. Endothelial cells lining the vessels can suppress T cell activity, target them for destruction, and block them from gaining entry into the tumor in the first place through the deregulation of adhesion molecules. Here we review approaches to break this tumor endothelial barrier and enhance T cell activity.

Redefining the role(s) of endothelial αvβ3-integrin in angiogenesis

For nearly two decades now, the RGD (Arg-Gly-Asp)-binding αvβ3-integrin has been a focus of anti-angiogenic drug design. These inhibitors are well-tolerated, but have shown only limited success in patients. Over the years, studies in β3-integrin-knockout mice have shed some light on possible explanations for disappointing clinical outcomes. However, studying angiogenesis in β3-integrin-knockout mice is a blunt tool to investigate β3-integrin's role in pathological angiogenesis. Since establishing our laboratory at University of East Anglia (UEA), we have adopted more refined models of genetically manipulating the expression of the β3-integrin subunit. The present review will highlight some of our findings from these models and describe how data from them have forced us to rethink how targeting αvβ3-integrin expression affects tumour angiogenesis and cancer progression. Revisiting the fundamental biology behind how this integrin regulates tumour growth and angiogenesis, we believe, is the key not only to understanding how angiogenesis is normally co-ordinated, but also in success with drugs directed against it.

Intratumor heterogeneity and its impact on drug distribution and sensitivity

We provide an overview of the available information on the distribution of chemotherapeutics in human tumors, highlighting the progress made to assess the heterogeneity of drug concentrations in relation to the complex neoplastic tissue using novel analytical methods, e.g., mass spectrometry imaging. The increase in interstitial fluid pressure due to abnormal vascularization and stiffness of tumor stroma explains the variable and heterogeneous drug concentrations. Therapeutic strategies to enhance tumor drug distribution, thus possibly increasing efficacy, are discussed.

In vitro models of tumor vessels and matrix: engineering approaches to investigate transport limitations and drug delivery in cancer

Tumor-stroma interactions have emerged as critical determinants of drug efficacy. However, the underlying biological and physicochemical mechanisms by which the microenvironment regulates therapeutic response remain unclear, due in part to a lack of physiologically relevant in vitro platforms to accurately interrogate tissue-level phenomena. Tissue-engineered tumor models are beginning to address this shortcoming. By allowing selective incorporation of microenvironmental complexity, these platforms afford unique access to tumor-associated signaling and transport dynamics. This review will focus on engineering approaches to study drug delivery as a function of tumor-associated changes of the vasculature and extracellular matrix (ECM). First, we review current biological understanding of these components and discuss their impact on transport processes. Then, we evaluate existing microfluidic, tissue engineering, and materials science strategies to recapitulate vascular and ECM characteristics of tumors, and finish by outlining challenges and future directions of the field that may ultimately improve anti-cancer therapies.

Pancreatic-carcinoma-cell-derived pro-angiogenic factors can induce endothelial-cell differentiation of a subset of circulating CD34+ progenitors

Background

CD34⁺ progenitor cells comprise both hematopoietic and endothelial progenitor cells. Recent studies suggest that circulating endothelial progenitor cells are recruited into the angiogenic vascular system of several cancers, including pancreatic carcinoma, and that they correlate with clinical progress. However, whether endothelial progenitor cell mobilization occurs in response to cytokine release by tumor cells is still unclear.

Methods

The chemotactic- and/or differentiating-activities of the poorly-differentiated pancreatic carcinoma cell line PT45, and of the immortal H6c7 cell line, a line of near-normal pancreatic duct epithelial cells, on endothelial progenitor cells were investigated in vitro using circulating CD34⁺ as model.

Results

The study showed that Vascular Endothelial Growth Factor produced by PT45 cells and, at lesser extent, by H6c7 cells, predominantly chemoattract peripheral blood CD34⁺ expressing the type 2 relative receptor. Addition of PT45-conditioned medium to CD34⁺ cells, cultured under conditions supporting myeloid cell development, diverted the differentiation of a subset of these progenitor cells into cells expressing endothelial cell markers, such as CD146, CD105, VE-cadherin and von Willebrand Factor-related antigen. Moreover, these endothelial-like cells formed capillary networks in vitro, chiefly through the release of Angiopoietin-1 by PT45 cells.

Conclusions

The results demonstrate that pancreatic-carcinoma cells potentially attract circulating endothelial progenitor cells to the tumor site, by releasing high levels of pro-angiogenic factors such as Vascular Endothelial Growth Factor and Angiopoietin-1, and may direct the differentiation of these cell subsets of the CD34⁺ cell population into endothelial cells; the latter cells may become a component of the newly-formed vessels, contributing to angiogenesis-mediated tumor growth and metastasis.

CKD-516 displays vascular disrupting properties and enhances anti-tumor activity in combination with chemotherapy in a murine tumor model

PURPOSE

CKD-516 is a benzophenone analog in which the B ring is modified by replacement with a carbonyl group. The study assessed CKD-516 as a vascular disrupting agent or anti-cancer drug.

METHODS

To assess the effect of S516 on vascularization, we analyzed the effect on human umbilical vein endothelial cells (HUVECs). To determine the inhibition of cell proliferation of S516, we used H460 lung carcinoma cells. The alteration of microtubules was analyzed using immunoblot, RT-PCR and confocal imaging. To evaluate the anti-tumor effects of gemcitabine and/or CKD-516, H460 xenograft mice were treated with CKD-516 (2.5 mg/kg) and/or gemcitabine (40 mg/kg), and tumor growth was compared with vehicle-treated control. For histologic analysis, liver, spleen and tumor tissues from H460 xenograft mice were obtained 12 and 24 h after CKD-516 injection.

RESULTS

Cytoskeletal changes of HUVECs treated with 10 nM S516 were assessed by immunoblot and confocal imaging. S516 disrupted tubulin assembly and resulted in microtubule dysfunction, which induced cell cycle arrest (G2/M). S516 markedly enhanced the depolymerization of microtubules, perhaps due to the vascular disrupting properties of S516. Interestingly, S516 decreased the amount of total tubulin protein in HUVECs. Especially, S516 decreased mRNA expression α-tubulin (HUVECs only) and β-tubulin (HUVECs and H460 cells) at an early time point (4 h). Immunocytochemical analysis showed that S516 changed the cellular microtubule network and inhibited the formation of polymerized microtubules. Extensive central necrosis of tumors was evident by 12 h after treatment with CKD-516 (2.5 mg/kg, i.p.). In H460 xenografts, CKD-516 combined with gemcitabine significantly delayed tumor growth up to 57 % and 36 % as compared to control and gemcitabine alone, respectively.

CONCLUSION

CKD-516 is a novel agent with vascular disrupting properties and enhances anti-tumor activity in combination with chemotherapy.

Tumour hypoxia determines the potential of combining mTOR and autophagy inhibitors to treat mammary tumours

BACKGROUND

Hypoxia can activate autophagy, a self-digest adaptive process that maintains cell turnover. Mammalian target of rapamycin (mTOR) inhibitors are used to treat cancer but also stimulate autophagy.

METHODS

Human mammary cancer cells and derived xenografts were used to examine whether hypoxia could exacerbate autophagy-mediated resistance to the mTOR inhibitor rapamycin.

RESULTS

Rapamycin exerted potent antitumour effects in MCF-7 and MDA-MB-231 mammary tumours through a marked inhibition of angiogenesis, but the autophagy inhibitor chloroquine (CQ) failed to further sensitise tumours to mTOR inhibition. Rapamycin treatment actually led to tumour reoxygenation, thereby preventing the development of autophagy. Chloroquine alone, however, blocked the growth of MCF-7 tumours and in vitro blunted the hypoxia-induced component of autophagy in these cells. Finally, when initiating CQ treatment in large, hypoxic tumours, a robust antitumour effect could be observed, which also further increased the antiproliferative effects of rapamycin.

CONCLUSION

The mTOR inhibitor rapamycin significantly contributes to tumour growth inhibition and normalisation of the tumour vasculature through potent antiangiogenic effects. The resulting reduction in hypoxia accounts for a lack of sensitisation by the autophagy inhibitor CQ, except if the tumours are already at an advanced stage, and thus largely hypoxic at the initiation of the combination of rapamycin and CQ treatment.

Biphasic magnetic nanoparticles-nanovesicle hybrids for chemotherapy and self-controlled hyperthermia

AIM

The aim was to develop magnetic nanovesicles for chemotherapy and self-controlled hyperthermia that prevent overheating of tissues.

MATERIALS & METHODS

Magnetic nanovesicles containing paclitaxel and a dextran-coated biphasic suspension of La0.75Sr0.25MnO3 and Fe3O4 nanoparticles (magnetic nanoparticles) were developed.

RESULTS

Encapsulation efficiencies of magnetic nanoparticles and paclitaxel were 67 ± 5 and 83 ± 3%, respectively. Sequential release performed at 37°C for 1 h followed by 44°C for another 1 h (as expected for intratumoral injection), showed a cumulative release of 6.6% (109.6 µg), which was above the IC50 of the drug. In an alternating current magnetic field, the temperature remained controlled at 44°C and a synergistic cytotoxicity of paclitaxel and hyperthermia was observed in MCF-7 cells.

CONCLUSION

Magnetic nanovesicles containing biphasic suspensions La0.75Sr0.25MnO3 and Fe3O4 nanoparticles encapsulating paclitaxel have potential for combined self-controlled hyperthermia and chemotherapy.

A new method combining sequential immunoaffinity depletion and differential in gel electrophoresis to identify autoantibodies as cancer biomarkers

Easily measurable biomarkers are urgently required to detect early stages of cancer progression. Autoantibodies (aAbs), as a component of the humoral immune response against tumor cells, have such potential of diagnostic markers since they are circulating and stable proteins, produced rapidly and easily amenable to in vitro dosage. The identification of aAbs is based on the characterization of tumor-associated antigens (TAA) against which they are directed. Here, we propose a new method for an unbiased identification of TAA and thereby of aAbs as cancer biomarkers. This method that we called sequential immunoaffinity depletion-differential in gel electrophoresis (SID-DIGE) is based on the immunodepletion of tumor cell lysates with IgG from control and tumor-bearing mice and direct matching of the flow throughs of these immunoaffinity separations on the same 2D format. This strategy reduces the complexity of the samples to be analyzed and maximizes the interest of assessing hundreds of proteins simultaneously. SID-DIGE has also the potential, contrary to existing serological proteome analysis (SERPA) techniques, to detect immunogenic proteins with conformational epitopes, including those resulting from post-translational modifications. Using a model of human colorectal tumors in mice for the proof of principle, we showed that SID-DIGE outperforms the conventional SERPA technique, with the identification of 7 common TAA (validating our approach) and 18 additional aAbs proving the potential of this new method. In particular, the identification of aAbs directed against key enzymes supporting glycolysis gives credential to the role of hypoxia as a major determinant of the tumor proteome and thus as a source of immunogenicity. Overall, the developed methodology allowed efficient screening of sera for the identification of aAbs as potential biomarkers.

KML001 displays vascular disrupting properties and irinotecan combined antitumor activities in a murine tumor model

KML001 is sodium metaarsenite, and has shown cytotoxic activity in human tumor cell lines. The anti-cancer mechanism of KML001 involves cancer cell destruction due to DNA damage at the telomeres of cancer cell chromosomes. In this study, we assessed the vascular disrupting properties of KML001 and investigated whether KML001 as VDA is able to increase anti-tumor activity in irinotecan combined treatment. We used a murine model of the CT26 colon carcinoma cell line. CT26 isograft mice treated intraperitoneally with 10 mg/kg KML001 displayed extensive central necrosis of tumor by 24 h. The vascular disrupting effects of KML001 were assessed by dynamic contrast enhanced magnetic resonance imaging. Gadopentetic acid-diethylene triaminepentaacetic acid contrast enhancement was markedly decreased in KML001-treated mice one day after treatment, whereas persistently high signal enhancement was observed in mice injected with saline. Rate constant K(ep) value representing capillary permeability was significantly decreased (p<0.05) in mice treated with KML001. Cytoskeletal changes of human umbilical vein endothelial cells (HUVECs) treated with 10 uM KML001 were assessed by immune blotting and confocal imaging. KML001 degraded tubulin protein in HUVECs, which may be related to vascular disrupting properties of KML001. Finally, in the mouse CT26 isograft model, KML001 combined with irinotecan significantly delayed tumor growth as compared to control and irinotecan alone. These results suggest that KML001 is a novel vascular disrupting agent, which exhibits significant vascular shut-down activity and enhances anti-tumor activity in combination with chemotherapy. These data further suggest an avenue for effective combination therapy in treating solid tumors.

RGD-based strategies to target alpha(v) beta(3) integrin in cancer therapy and diagnosis

The integrin α(v)β(3) plays an important role in angiogenesis. It is expressed on tumoral endothelial cells as well as on some tumor cells. RGD peptides are well-known to bind preferentially to the α(v)β(3) integrin. In this context, targeting tumor cells or tumor vasculature by RGD-based strategies is a promising approach for delivering anticancer drugs or contrast agents for cancer therapy and diagnosis. RGD-based strategies include antagonist drugs (peptidic or peptidomimetic) of the RGD sequence, RGD-conjugates, and the grafting of the RGD peptide or peptidomimetic, as targeting ligand, at the surface of nanocarriers. Although all strategies are overviewed, this review aims to particularly highlight the position of RGD-based nanoparticles in cancer therapy and imaging. This review is divided into three parts: the first one describes the context of angiogenesis, the role of the integrin α(v)β(3), and the binding of the RGD peptide to this integrin; the second one focuses on RGD-based strategies in cancer therapy; while the third one focuses on RGD-based strategies in cancer diagnosis.

microRNA-29a suppresses cell proliferation by targeting SPARC in hepatocellular carcinoma

In the present study, we constructed a lentivirus vector encoding the miR-29a precursor and established two stably infected cell lines, PLC-29a and 97L-29a. The overexpression of miR-29a was confirmed by TaqMan RT-PCR and significantly suppressed the growth of the hepatocellular carcinoma cell lines MHCC-97L and PLC. Dual-luciferase reporter assays indicated that the SPARC mRNA 3'UTR was directly targeted by miR-29a since the mutated 3'UTR was not affected. Silencing SPARC expression by RNAi knockdown resulted in a similar effect as miR-29a overexpression on hepatocellular carcinoma (HCC) cell growth regulation. Anti-miR-29a oligonucleotides (AMOs) upregulated the levels of SPARC in the HCC cells. The phosphorylation of AKT/mTOR downstream of SPARC was inhibited in miR-29a-overexpressing HCC cells. We further examined and compared the expression levels of miR-29a in HCC tissues and the corresponding nearby non-cancerous liver tissues of 110 patients with HCC by qRT-PCR, and significantly lower expression of miR-29a was observed in the tissues affected by HCC. Our findings demonstrate that the expression of miR-29a is important in the regulation of the SPARC-AKT pathway and HCC growth.

Stromal interactions as regulators of tumor growth and therapeutic response: A potential target for photodynamic therapy?

It has become increasingly widely recognized that the stroma plays several vital roles in tumor growth and development and that tumor-stroma interactions can in many cases account poor therapeutic response. Inspired by an emerging body of literature, we consider the potential role of photodynamic therapy (PDT) for targeting interactions with stromal fibroblasts and mechano-sensitive signaling with the extracellular matrix as a means to drive tumors toward a more therapeutically responsive state and synergize with other treatments. This concept is particularly relevant for cancer of the pancreas, which is characterized by tumors with a profoundly dense, rigid fibrous stroma. Here we introduce new in vitro systems to model interactions between pancreatic tumors and their mechanical microenvironment and restore signaling with stromal fibroblasts. Using one such model as a test bed it is shown here that PDT treatment is able to destroy fibroblasts in an in vitro 3D pancreatic tumor-fibroblast co-culture. These results and the literature suggest the further development of PDT as a potential modality for stromal depletion.

Enzymatic targeting of the stroma ablates physical barriers to treatment of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinomas (PDAs) are characterized by a robust fibroinflammatory response. We show here that this desmoplastic reaction generates inordinately high interstitial fluid pressures (IFPs), exceeding those previously measured or theorized for solid tumors, and induces vascular collapse, while presenting substantial barriers to perfusion, diffusion, and convection of small molecule therapeutics. We identify hyaluronan, or hyaluronic acid (HA), as the primary matrix determinant of these barriers and show that systemic administration of an enzymatic agent can ablate stromal HA from autochthonous murine PDA, normalize IFP, and re-expand the microvasculature. In combination with the standard chemotherapeutic, gemcitabine, the treatment permanently remodels the tumor microenvironment and consistently achieves objective tumor responses, resulting in a near doubling of overall survival.

Lactate shuttles at a glance: from physiological paradigms to anti-cancer treatments

Hypoxia and oncogene expression both stimulate glycolytic metabolism in tumors, thereby leading to lactate production. However, lactate is more than merely a by-product of glycolysis: it can be used as a metabolic fuel by oxidative cancer cells. This phenomenon resembles processes that have been described for skeletal muscle and brain that involve what are known as cell-cell and intracellular lactate shuttles. Two control points regulate lactate shuttles: the lactate dehydrogenase (LDH)-dependent conversion of lactate into pyruvate (and back), and the transport of lactate into and out of cells through specific monocarboxylate transporters (MCTs). In tumors, MCT4 is largely involved in hypoxia-driven lactate release, whereas the uptake of lactate into both tumor cells and tumor endothelial cells occurs via MCT1. Translating knowledge of lactate shuttles to the cancer field offers new perspectives to therapeutically target the hypoxic tumor microenvironment and to tackle tumor angiogenesis.

Collagenase-1 injection improved tumor distribution and gene expression of cationic lipoplex

Elevated interstitial fluid pressure (IFP) in a tumor is a barrier to tumor accumulation of systemic delivery of nanocarriers. In this study, we investigated whether intravenous injection of type I collagenase (collagenase-1) reduced IFP in tumors and increased the accumulation and gene expression of cationic liposome/plasmid DNA complex (lipoplex) in tumors after intravenous injection into mice bearing mouse lung carcinoma LLC tumors. Collagenase-1 reduced the amount of type I collagen in the tumor, and significantly decreased IFP by 65% at 1h after injection. Therefore, collagenase-1 induced 1.5-fold higher accumulation and 2-fold higher gene expression of lipoplex in tumors after intravenous injection. These findings indicated that intravenous injection of collagenase-1 improved the accumulation of lipoplex by decreasing IFP in tumors. These results support the potential use of collagen digestion as a strategy to improve systemic gene delivery into tumors.