PLGA Nanoparticles Codelivering siRNAs against Programmed Cell Death Protein-1 and Its Ligand Gene for Suppression of Colon Tumor Growth

Development of a peptide-based tumor-activated checkpoint inhibitor for cancer immunotherapy

Antibody-based checkpoint inhibitors have achieved great success in cancer immunotherapy, but their uncontrollable immune-related adverse events remain a major challenge. In this study, we developed a tumor-activated nanoparticle that is specifically active in tumors but not in normal tissues. We discovered a short anti-PD-L1 peptide that blocks the PD-1/PD-L1 interaction. The peptide was modified with a PEG chain through a novel matrix metalloproteinase-2 (MMP-2)-specific cleavage linker. The modified TR3 peptide self-assembles into a micelle-like nanoparticle (TR3-M-NP), which remains inactive and unable to block the PD-1/PD-L1 interaction in its native form. However, upon cleavage by MMP-2 in tumors, it releases the active peptide. The TR3-M-NP5k nanoparticle was specifically activated in tumors through enzyme-mediated cleavage, leading to the inhibition of tumor growth and extended survival compared to control groups. In summary, TR3-M-NP shows great potential as a tumor-responsive immunotherapy agent with reduced toxicities. STATEMENT OF SIGNIFICANCE: In this study, we developed a bioactive peptide-based checkpoint inhibitor that is active only in tumors and not in normal tissues, thereby potentially avoiding immune-related adverse effects. We discovered a short anti-PD-L1 peptide, TR3, that blocks the PD-1/PD-L1 interaction. We chemically modified the TR3 peptide to self-assemble into a micelle-like nanoparticle (TR3-M-NP), which itself cannot block the PD-1/PD-L1 interaction but releases the active TR3 peptide in tumors upon cleavage by MMP-2. In contrast, the nanoparticle is randomly degraded in normal tissues into peptides fragments that cannot block the PD-1/PD-L1 interaction. Upon intraperitoneal injection, TR3-M-NP5k was activated specifically in tumors through enzyme cleavage, leading to the inhibition of tumor growth and extended survival compared to the control groups. In summary, TR3-M-NP holds significant promise as a tumor-responsive immunotherapy agent with reduced toxicities. The bioactive platform has the potential to be used for other types of checkpoint inhibitor.

The drug release of PLGA-based nanoparticles and their application in treatment of gastrointestinal cancers

The poly (lactic-co-glycolic acid) (PLGA) based nanoparticles have been applied for drug delivery due to their simple preparation, biodegradability, and ideal biocompatibility. In this study, the factors affecting the degradation of PLGA-based nanoparticles are reviewed, encompassing the ratio of PLA to PGA, relative molecular weight, crystallinity, and preparation process of PLGA nanoparticles. The drug release behavior of PLGA-based nanoparticles, such as the degradation environment, encapsulated drug properties of polymers, and drug loading rates, are also discussed. Since gastrointestinal cancer is one of the major global threats to human health, this paper comprehensively summarizes the application of PLGA nanoparticles in gastrointestinal cancers from diagnosis, chemotherapy, radiotherapy, and novel tumor treatment methods (immunotherapy, gene therapy, and photothermal therapy). Finally, the future application of PLGA-based drug delivery systems in treating gastrointestinal cancers is discussed. The bottleneck of application status and the prospect of PLGA-nanoparticles in gastrointestinal tumor application are presented. To truly realize the great and wide application of PLGA-based nanoparticles, collaborative progress in the field of nanomaterials and life sciences is needed.

Immune-related adverse events of antibody-based biological medicines in cancer therapy

Recombinant antibodies (Abs) are an integral modality for the treatment of multiple tumour malignancies. Since the Food and Drug Administration (FDA) approval of rituximab as the first monoclonal antibody (mAb) for cancer treatment, several mAbs and antibody (Ab)-based therapies have been approved for the treatment of solid tumour malignancies and other cancers. These Abs function by either blocking oncogenic pathways or angiogenesis, modulating immune response, or by delivering a conjugated drug. The use of Ab-based therapy in cancer patients who could benefit from the treatment, however, is still limited by associated toxicity profiles which may stem from biological features and processes related to target binding, alongside biochemical and/or biophysical characteristics of the therapeutic Ab. A significant immune-related adverse event (irAE) associated with Ab-based therapies is cytokine release syndrome (CRS), characterized by the development of fever, rash and even marked, life-threatening hypotension, and acute inflammation with secondary to systemic uncontrolled increase in a range of pro-inflammatory cytokines. Here, we review irAEs associated with specific classes of approved, Ab-based novel cancer immunotherapeutics, namely immune checkpoint (IC)-targeting Abs, bispecific Abs (BsAbs) and Ab-drug-conjugates (ADCs), highlighting the significance of harmonization in preclinical assay development for safety assessment of Ab-based biotherapeutics as an approach to support and refine clinical translation.

Enhancing cancer immunotherapy: Exploring strategies to target the PD-1/PD-L1 axis and analyzing the associated patent, regulatory, and clinical trial landscape

Cancer treatment modalities and their progression is guided by the specifics of cancer, including its type and site of localization. Surgery, radiation, and chemotherapy are the most often used conventional treatments. Conversely, emerging treatment techniques include immunotherapy, hormone therapy, anti-angiogenic therapy, dendritic cell-based immunotherapy, and stem cell therapy. Immune checkpoint inhibitors' anticancer properties have drawn considerable attention in recent studies in the cancer research domain. Programmed Cell Death Protein-1 (PD-1) and its ligand (PD-L1) checkpoint pathway are key regulators of the interactions between activated T-cells and cancer cells, protecting the latter from immune destruction. When the ligand PD-L1 attaches to the receptor PD-1, T-cells are prevented from destroying cells that contain PD-L1, including cancer cells. The PD-1/PD-L1 checkpoint inhibitors block them, boosting the immune response and strengthening the body's defenses against tumors. Recent years have seen incredible progress and tremendous advancement in developing anticancer therapies using PD-1/PD-L1 targeting antibodies. While immune-related adverse effects and low response rates significantly limit these therapies, there is a need for research on methods that raise their efficacy and lower their toxicity. This review discusses various recent innovative nanomedicine strategies such as PLGA nanoparticles, carbon nanotubes and drug loaded liposomes to treat cancer targeting PD-1/PD-L1 axis. The biological implications of PD-1/PD-L1 in cancer treatment and the fundamentals of nanotechnology, focusing on the novel strategies used in nanomedicine, are widely discussed along with the corresponding guidelines, clinical trial status, and the patent landscape of such formulations.

Advancing cancer immunotherapy through siRNA-based gene silencing for immune checkpoint blockade

Cancer immunotherapy represents a revolutionary strategy, leveraging the patient's immune system to inhibit tumor growth and alleviate the immunosuppressive effects of the tumor microenvironment (TME). The recent emergence of immune checkpoint blockade (ICB) therapies, particularly following the first approval of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitors like ipilimumab, has led to significant growth in cancer immunotherapy. The extensive explorations on diverse immune checkpoint antibodies have broadened the therapeutic scope for various malignancies. However, the clinical response to these antibody-based ICB therapies remains limited, with less than 15% responsiveness and notable adverse effects in some patients. This review introduces the emerging strategies to overcome current limitations of antibody-based ICB therapies, mainly focusing on the development of small interfering ribonucleic acid (siRNA)-based ICB therapies and innovative delivery systems. We firstly highlight the diverse target immune checkpoint genes for siRNA-based ICB therapies, incorporating silencing of multiple genes to boost anti-tumor immune responses. Subsequently, we discuss improvements in siRNA delivery systems, enhanced by various nanocarriers, aimed at overcoming siRNA's clinical challenges such as vulnerability to enzymatic degradation, inadequate pharmacokinetics, and possible unintended target interactions. Additionally, the review presents various combination therapies that integrate chemotherapy, phototherapy, stimulatory checkpoints, ICB antibodies, and cancer vaccines. The important point is that when used in combination with siRNA-based ICB therapy, the synergistic effect of traditional therapies is strengthened, improving host immune surveillance and therapeutic outcomes. Conclusively, we discuss the insights into innovative and effective cancer immunotherapeutic strategies based on RNA interference (RNAi) technology utilizing siRNA and nanocarriers as a novel approach in ICB cancer immunotherapy.

Recent progress, perspectives, and issues of engineered PD-L1 regulation nano-system to better cure tumor: A review

Currently, immune checkpoint blockade (ICB) therapies that target the programmed cell death ligand-1 (PD-L1) have been used as revolutionary cancer treatments in the clinic. Apart from restoring the antitumor response of cytotoxic T cells by blocking the interaction between PD-L1 on tumor cells and programmed cell death-1 (PD-1) on T cells, PD-L1 proteins were also newly revealed to possess the capacity to accelerate DNA damage repair (DDR) and enhance tumor growth through multiple mechanisms, leading to the impaired efficacy of tumor therapies. Nevertheless, current free anti-PD-1/PD-L1 therapy still suffered from poor therapeutic outcomes in most solid tumors due to the non-selective tumor accumulation, ineludible severe cytotoxic effects, as well as the common occurrence of immune resistance. Recently, nanoparticles with efficient tumor-targeting capacity, tumor-responsive prosperity, and versatility for combination therapy were identified as new avenues for PD-L1 targeting cancer immunotherapies. In this review, we first summarized the multiple functions of PD-L1 protein in promoting tumor growth, accelerating DDR, as well as depressing immunotherapy efficacy. Following this, the effects and mechanisms of current clinically widespread tumor therapies on tumor PD-L1 expression were discussed. Then, we reviewed the recent advances in nanoparticles for anti-PD-L1 therapy via using PD-L1 antibodies, small interfering RNA (siRNA), microRNA (miRNA), clustered, regularly interspaced, short palindromic repeats (CRISPR), peptide, and small molecular drugs. At last, we discussed the challenges and perspectives to promote the clinical application of nanoparticles-based PD-L1-targeting therapy.

Current progress, strategy, and prospects of PD-1/PDL-1 immune checkpoint biosensing platforms for cancer diagnostics, therapy monitoring, and drug screening

Recent technological advancements in testing and monitoring instrumentation have greatly contributed to the progress in cancer treatment by surgical, chemotherapeutic and radiotherapeutic interventions. However, the mortality rate still remains high, calling for the development of new treatment strategies with higher efficacy. Extensive efforts driven in this direction have included broadening of early cancer screening and applying innovative theranostic nanotechnologies. They have been supported by platforms introduced to enable the detection and monitoring of cancer biomarkers, inhibitors, and other agents, able to slow down cancer progression and prevent metastasis. Despite of the well-recognized principles of the immune checkpoint blockade, the efficacy of immunotherapy achieved so far does not meet the well-founded expectations. For a successful cancer treatment, highly sensitive, robust, and inexpensive multiplex biosensors have to be designed to aid in the biomarkers monitoring and in the development of new inhibitors. In this review, we provide an overview of the efforts undertaken to aid in the development and monitoring of anticancer immunotherapy, based on the programmed cell-death immune checkpoint (PD-1/PDL-1) blockade, by designing biosensors for the detection of relevant cancer biomarkers and their inhibitors screening. This review also emphasizes alternative targets made by exosomes carrying PD-L1 overexpressed in cancer cells and passed into the excreted exosomes. Evaluated are also novel targeted drug delivery nanocarriers, providing simultaneous biosensing, thereby contributing to the emerging immune checkpoint cancer therapy. On the basis of the current trends and the emerging technologies, future perspectives of cancer diagnostics and treatment monitoring using biosensing platforms are projected.

GSH/pH dual response drug delivery system for photothermal enhanced gene-immunotherapy

Breast cancer has emerged as a leading cause of mortality among women. Photothermal therapy represents a recent therapeutic modality for eradicating localized tumors, albeit hindered by its limited penetration into tumor tissues. Recognizing the potential of photothermal therapy to induce immunogenic cell death in tumor cells, we explored a gene delivery approach utilizing small interfering RNA targeting programmed death ligand 1 (PD-L1), abbreviated as siPD-L1, to bolster the anti-tumor immune response elicited by this therapy. Nonetheless, the suboptimal release efficiency and inherent instability of RNA molecules have posed challenges to their therapeutic efficacy. In this study, we designed a glutathione (GSH)/pH-responsive micelle system, employing biocompatible and low-toxicity polyethyleneimine in conjunction with structurally robust pluronic P123, to encapsulate both indocyanine green (ICG) and siPD-L1 for precise targeting in breast cancer treatment. The resulting PSP/ICG/siPD-L1 nanocarrier demonstrated admirable biocompatibility and stability. Upon internalization into tumor cells, this nanocarrier exhibited rapid release of both ICG and siPD-L1, responding to the acidic tumor microenvironment and GSH conditions. The inclusion of siPD-L1 effectively downregulated the expression of PD-L1 on the tumor cell surface, thereby impeding tumor growth. Additionally, ICG demonstrated a photothermal effect when exposed to near-infrared light. Both in vitro and in vivo investigations substantiated the nanocarrier's efficacy against tumor cells, culminating in the complete ablation of 4T1 tumors in situ. Consequently, PSP/ICG/siPD-L1 emerges as a promising nanocarrier candidate for augmenting anti-tumor immunity through the synergistic combination of photothermal therapy and gene-based intervention.

Nano-immunotherapy: overcoming delivery challenge of immune checkpoint therapy

Immune checkpoint (ICP) molecules expressed on tumor cells can suppress immune responses against tumors. ICP therapy promotes anti-tumor immune responses by targeting inhibitory and stimulatory pathways of immune cells like T cells and dendritic cells (DC). The investigation into the combination therapies through novel immune checkpoint inhibitors (ICIs) has been limited due to immune-related adverse events (irAEs), low response rate, and lack of optimal strategy for combinatorial cancer immunotherapy (IMT). Nanoparticles (NPs) have emerged as powerful tools to promote multidisciplinary cooperation. The feasibility and efficacy of targeted delivery of ICIs using NPs overcome the primary barrier, improve therapeutic efficacy, and provide a rationale for more clinical investigations. Likewise, NPs can conjugate or encapsulate ICIs, including antibodies, RNAs, and small molecule inhibitors. Therefore, combining the drug delivery system (DDS) with ICP therapy could provide a profitable immunotherapeutic strategy for cancer treatment. This article reviews the significant NPs with controlled DDS using current data from clinical and pre-clinical trials on mono- and combination IMT to overcome ICP therapeutic limitations.

Advances in PD-1 signaling inhibition-based nano-delivery systems for tumor therapy

In recent years, cancer immunotherapy has emerged as an exciting cancer treatment. Immune checkpoint blockade brings new opportunities for more researchers and clinicians. Programmed cell death receptor-1 (PD-1) is a widely studied immune checkpoint, and PD-1 blockade therapy has shown promising results in a variety of tumors, including melanoma, non-small cell lung cancer and renal cell carcinoma, which greatly improves patient overall survival and becomes a promising tool for the eradication of metastatic or inoperable tumors. However, low responsiveness and immune-related adverse effects currently limit its clinical application. Overcoming these difficulties is a major challenge to improve PD-1 blockade therapies. Nanomaterials have unique properties that enable targeted drug delivery, combination therapy through multidrug co-delivery strategies, and controlled drug release through sensitive bonds construction. In recent years, combining nanomaterials with PD-1 blockade therapy to construct novel single-drug-based or combination therapy-based nano-delivery systems has become an effective mean to address the limitations of PD-1 blockade therapy. In this study, the application of nanomaterial carriers in individual delivery of PD-1 inhibitors, combined delivery of PD-1 inhibitors and other immunomodulators, chemotherapeutic drugs, photothermal reagents were reviewed, which provides effective references for designing new PD-1 blockade therapeutic strategies.

Novel technologies for applying immune checkpoint blockers

Cancer cells develop several ways to subdue the immune system among others via upregulation of inhibitory immune checkpoint (ICP) proteins. These ICPs paralyze immune effector cells and thereby enable unfettered tumor growth. Monoclonal antibodies (mAbs) that block ICPs can prevent immune exhaustion. Due to their outstanding effects, mAbs revolutionized the field of cancer immunotherapy. However, current ICP therapy regimens suffer from issues related to systemic administration of mAbs, including the onset of immune related adverse events, poor pharmacokinetics, limited tumor accessibility and immunogenicity. These drawbacks and new insights on spatiality prompted the exploration of novel administration routes for mAbs for instance peritumoral delivery. Moreover, novel ICP drug classes that are adept to novel delivery technologies were developed to circumvent the drawbacks of mAbs. We therefore review the state-of-the-art and novel delivery strategies of ICP drugs.

Plasmid DNA cationic non-viral vector complexes induce cytotoxicity-associated PD-L1 expression up-regulation in cancer cells in vitro

Non-viral vectors are promising nucleic acid carriers which have been utilized in gene-based cancer immunotherapy. The aim of this study is to compare the transfection efficiency and cytotoxicity of three cationic non-viral vectors namely Polyethylenimine (PEI), Lipofectamine 2000 (LPF) and stable nucleic acid lipid particles (SNALPs) of different lipid compositions, for the delivery of plasmid DNA (pDNA) expressing immunostimulatory molecules, OX40L or 4-1BBL, to cancer cells in vitro. The results indicate that PEI and LPF are efficient vectors for pDNA delivery with high transfection efficiency obtained. However, pDNA-PEI and pDNA-LPF complexes up-regulated the expression of programmed death ligand-1 (PD-L1) and induced significant cytotoxicity in both B16F10 and CT26 cell lines. The up-regulation of PD-L1 expression induced by pDNA-PEI and pDNA-LPF complexes was independent of cancer cell line, nor was it linked to the presence of GpC motifs in the pDNA. In contrast, the use of biocompatible SNALPs (MC3 and KC2 types) resulted in lower pDNA transfection efficiency, however no significant up-regulation of PD-L1 or cytotoxicity was observed. A strong correlation was found between up-regulation of PD-L1 expression and cytotoxicity. Up-regulation of PD-L1 expression could be mitigated with RNAi, maintaining expression at basal levels. Due to the improved biocompatibility and the absence of PD-L1 up-regulation, SNALPs represent a viable non-viral nucleic acid vector for delivery of pDNA encoding immunostimulatory molecules. The results of this study suggest that PD-L1 expression should be monitored when selecting commercial transfection reagents as pDNA vectors for cancer immunotherapy in vitro.

Recent Advancements in the Design of Nanodelivery Systems of siRNA for Cancer Therapy

RNA interference (RNAi) has increased the possibility of restoring RNA drug targets for cancer treatment. Small interfering RNA (siRNA) is a promising therapeutic RNAi tool that targets the defective gene by inhibiting its mRNA expression and stopping its translation. However, siRNAs have flaws like poor intracellular trafficking, RNase degradation, rapid kidney filtration, off-targeting, and toxicity, which limit their therapeutic efficiency. Nanocarriers (NCs) have been designed to overcome such flaws and increase antitumor activity. Combining siRNA and anticancer drugs can give synergistic effects in cancer cells, making them a significant gene-modification tool in cancer therapy. Our discussion of NCs-mediated siRNA delivery in this review includes their mechanism, limitations, and advantages in comparison with naked siRNA delivery. We will also discuss organic NCs (polymers and lipids) and inorganic NCs (quantum dots, carbon nanotubes, and gold) that have been reported for extensive delivery of therapeutic siRNA to tumor sites. Finally, we will conclude by discussing the studies based on organic and inorganic NCs-mediated siRNA drug delivery systems conducted in the years 2020 and 2021.

Advancing immune checkpoint blockade in colorectal cancer therapy with nanotechnology

Immune checkpoint blockade (ICB) has gained unparalleled success in the treatment of colorectal cancer (CRC). However, undesired side effects, unsatisfactory response rates, tumor metastasis, and drug resistance still hinder the further application of ICB therapy against CRC. Advancing ICB with nanotechnology can be game-changing. With the development of immuno-oncology and nanomaterials, various nanoplatforms have been fabricated to enhance the efficacy of ICB in CRC treatment. Herein, this review systematically summarizes these recent nano-strategies according to their mechanisms. Despite their diverse and complex designs, these nanoplatforms have four main mechanisms in enhancing ICB: 1) targeting immune checkpoint inhibitors (ICIs) to tumor foci, 2) increasing tumor immunogenicity, 3) remodeling tumor microenvironment, and 4) pre-sensitizing immune systems. Importantly, advantages of nanotechnology in CRC, such as innovating the mode-of-actions of ICB, modulating intestinal microbiome, and integrating the whole process of antigen presentation, are highlighted in this review. In general, this review describes the latest applications of nanotechnology for CRC immunotherapy, and may shed light on the future design of ICB platforms.

Aptamer-Functionalized Nanoparticles Mediate PD-L1 siRNA Delivery for Effective Gene Silencing in Triple-Negative Breast Cancer Cells

Small interfering RNA (siRNA) therapies require effective delivery vehicles capable of carrying the siRNA cargo into target cells. To achieve tumor-targeting, a drug delivery system would have to incorporate ligands that specifically bind to receptors expressed on cancer cells to function as portals via receptor-mediated endocytosis. Cell-targeting and internalizing aptamers are the most suitable ligands for functionalization of drug-loaded nanocarriers. Here, we designed a novel aptamer-based platform for the active delivery of siRNA targeting programmed cell death-ligand 1 (PD-L1) to triple-negative breast cancer (TNBC) cells. The generated nanovectors consist of PLGA-based polymeric nanoparticles, which were loaded with PD-L1 siRNA and conjugated on their surface with a new RNA aptamer, specific for TNBC and resistant to nucleases. In vitro results demonstrated that these aptamer-conjugated nanoparticles promote siRNA uptake specifically into TNBC MDA-MB-231 and BT-549 target cells, along with its endosomal release, without recognizing non-TNBC BT-474 breast cancer cells. Their efficiency resulted in an almost complete suppression of PD-L1 expression as early as 90 min of cell treatment. This research provides a rational strategy for optimizing siRNA delivery systems for TNBC treatments.

Clinical pharmacology of siRNA therapeutics: current status and future prospects

INTRODUCTION

Small interfering RNA (siRNA) has emerged as a powerful tool for post-transcriptional downregulation of multiple genes for various therapies. Naked siRNA molecules are surrounded by several barriers that tackle their optimum delivery to target tissues such as limited cellular uptake, short circulation time, degradation by endonucleases, glomerular filtration, and capturing by the reticuloendothelial system (RES).

AREAS COVERED

This review provides insights into studies that investigate various siRNA-based therapies, focusing on the mechanism, delivery strategies, bioavailability, pharmacokinetic, and pharmacodynamics of naked and modified siRNA molecules. The clinical pharmacology of currently approved siRNA products is also discussed.

EXPERT OPINION

Few siRNA-based products have been approved recently by the Food and Drug Administration (FDA) and other regulatory agencies after approximately twenty years following its discovery due to the associated limitations. The absorption, distribution, metabolism, and excretion of siRNA therapeutics are highly restricted by several obstacles, resulting in rapid clearance of siRNA-based therapeutic products from systemic circulation before reaching the cytosol of targeted cells. The siRNA therapeutics however are very promising in many diseases, including gene therapy and SARS-COV-2 viral infection. The design of suitable delivery vehicles and developing strategies toward better pharmacokinetic parameters may solve the challenges of siRNA therapies.

Engineered nanomedicines for augmenting the efficacy of colorectal cancer immunotherapy

Colorectal cancer (CRC) is one of the most devastating diseases worldwide. Immunotherapeutic agents for CRC treatment have shown limited efficacy due to the immunosuppressive tumor microenvironment (TME). In this context, various types of nanoparticles (NPs) have been used to reverse the immunosuppressive TME, potentiate the effect of immunotherapeutic agents and reduce their systemic side effects. Many advantages could be offered by NPs, related to drug-loading efficiency, particle size and others that can potentially aid the delivery of immunotherapeutic agents. The recent research on how nano-based immunotherapy can remodel the immunosuppressive TME of CRC and hence boost the antitumor immune response, as well as the challenges that face clinical translation of NPs and future perspectives, are summarized in this review article.

Nanotechnology-enabled immunoengineering approaches to advance therapeutic applications

Immunotherapy has reached clinical success in the last decade, with the emergence of new and effective treatments such as checkpoint blockade therapy and CAR T-cell therapy that have drastically improved patient outcomes. Still, these therapies can be improved to limit off-target effects, mitigate systemic toxicities, and increase overall efficacies. Nanoscale engineering offers strategies that enable researchers to attain these goals through the manipulation of immune cell functions, such as enhancing immunity against cancers and pathogens, controlling the site of immune response, and promoting tolerance via the delivery of small molecule drugs or biologics. By tuning the properties of the nanomaterials, such as size, shape, charge, and surface chemistry, different types of immune cells can be targeted and engineered, such as dendritic cells for immunization, or T cells for promoting adaptive immunity. Researchers have come to better understand the critical role the immune system plays in the progression of pathologies besides cancer, and developing nanoengineering approaches that seek to harness the potential of immune cell activities can lead to favorable outcomes for the treatment of injuries and diseases.

Targeting the PD-1/PD-L1 axis for cancer treatment: a review on nanotechnology

Although nanomedicines have been in the oncology field for almost three decades with the introduction of doxil, only a few nanomedicine products have reached approval. Can nanotechnology be a realistic tool to reduce the number of hospital beds? At present, several clinically approved anti-PD-1/PD-L1 antibodies or CAR T cell-based therapies are available; however, the immunotherapy field is far from mature. Will immunotherapy be the fourth pillar of cancer treatment? In this review, we summarized the current status of immunotherapy using PD-1/PD-L1-targeting nanocarriers. The knowledge on material science, therapeutic agents and formulation designs could pave the way for high-efficacy treatment outcomes.

Combinational Chemoimmunotherapy for Breast Cancer by Codelivery of Doxorubicin and PD-L1 siRNA Using a PAMAM-Incorporated Liposomal Nanoplatform

Chemoimmunotherapy can synergistically enhance the therapeutic effects and decrease the side effects by a combined method. However, the effective targeted codelivery of various chemotherapeutic agents and siRNAs remains challenging. Although nanomedicine-based chemoimmunotherapy has shown great potential in cancer treatment in recent years, further effort is needed to simplify the nanocarrier designs and maintain their effective functions. Here, we report a simple but robust multifunctional liposomal nanocarrier that contains a pH-sensitive liposome (LP) shell and a dendritic core for tumor-targeted codelivery of programmed cell death ligand 1 (PD-L1) siRNA and doxorubicin (DOX) (siPD-L1@PM/DOX/LPs). siPD-L1@PM/DOX/LPs had a suitable particle size and zeta potential, excellent stability in serum, and pH-sensitive drug release in vitro. They exhibited significant cell proliferation inhibition compared to free DOX and DOX-loaded LPs and could escape endosomes, effectively release siRNA into the cytoplasm of MCF-7 cells, and significantly reduce the PD-L1 expression on tumor cells. In vivo imaging confirmed high accumulation of siPD-L1@PM/DOX/LPs at the tumor site. More importantly, compared with siPD-L1@PM/LPs or DOX alone, siPD-L1@PM/DOX/LPs were more effective in inhibiting tumor growth and activating cytotoxic T cells in vivo. In conclusion, this nanocarrier may hold promise as a codelivery nanoplatform to improve the treatment of various solid tumors.

Aptamer grafted nanoparticle as targeted therapeutic tool for the treatment of breast cancer

Breast carcinomas repeat their number and grow exponentially making it extremely frequent malignancy among women. Approximately, 70-80% of early diagnosed or non-metastatic conditions are treatable while the metastatic cases are considered ineffective to treat with current ample amount of therapy. Target based anti-cancer treatment has been in the limelight for decades and is perceived significant consideration of scientists. Aptamers are the 'coming of age' therapeutic approach, selected using an appropriate tool from the library of sequences. Aptamers are non-immunogenic, stable, and high-affinity ligand which are poised to reach the clinical benchmark. With the heed in nanoparticle application, the delivery of aptamer to the specific site could be enhanced which also protects them from nuclease degradation. Moreover, nanoparticles due to robust structure, high drug entrapment, and modifiable release of cargo could serve as a successful candidate in the treatment of breast carcinoma. This review would showcase the method and modified method of selection of aptamers, aptamers that were able to make its way towards clinical trial and their targetability and selectivity towards breast cancers. The appropriate usage of aptamer-based biosensor in breast cancer diagnosis have also been discussed.

Modulating expression of inhibitory and stimulatory immune 'checkpoints' using nanoparticulate-assisted nucleic acid delivery

Immune checkpoints are regulatory molecules responsible for determining the magnitude and nature of the immune response. The aim of immune checkpoint targeting immunotherapy is to manipulate these interactions, engaging the immune system in treatment of cancer. Clinically, the use of monoclonal antibodies to block immunosuppressive interactions has proven itself to be a highly effective immunotherapeutic intervention. Within the literature there are numerous candidates for next generation of immune checkpoint targeting strategies. One such example is the use of nucleic acid to alter expression levels of immune checkpoint molecules, either as antisense oligo nucleotides/siRNA, to downregulate inhibitory molecules, or mRNA/DNA, to express co-stimulatory molecules. A significant component of nucleic acid delivery is its formulation within a nanoparticulate system. In this review we discuss the progress of the preclinical application of nucleic acid-based immunotherapies to target a selection of co-inhibitory/co-stimulatory molecules. Furthermore, we identify the potential and current gaps within the literature which may form the basis of future work.

Encapsulation of Large-Size Plasmids in PLGA Nanoparticles for Gene Editing: Comparison of Three Different Synthesis Methods

The development of new gene-editing technologies has fostered the need for efficient and safe vectors capable of encapsulating large nucleic acids. In this work we evaluate the synthesis of large-size plasmid-loaded PLGA nanoparticles by double emulsion (considering batch ultrasound and microfluidics-assisted methodologies) and magnetic stirring-based nanoprecipitation synthesis methods. For this purpose, we characterized the nanoparticles and compared the results between the different synthesis processes in terms of encapsulation efficiency, morphology, particle size, polydispersity, zeta potential and structural integrity of loaded pDNA. Our results demonstrate particular sensibility of large pDNA for shear and mechanical stress degradation during double emulsion, the nanoprecipitation method being the only one that preserved plasmid integrity. However, plasmid-loaded PLGA nanoparticles synthesized by nanoprecipitation did not show cell expression in vitro, possibly due to the slow release profile observed in our experimental conditions. Strong electrostatic interactions between the large plasmid and the cationic PLGA used for this synthesis may underlie this release kinetics. Overall, none of the methods evaluated satisfied all the requirements for an efficient non-viral vector when applied to large-size plasmid encapsulation. Further optimization or alternative synthesis methods are thus in current need to adapt PLGA nanoparticles as delivery vectors for gene editing therapeutic technologies.

Bacterial cytoplasmic membranes synergistically enhance the antitumor activity of autologous cancer vaccines

Cancer vaccines based on resected tumors from patients have gained great interest as an individualized cancer treatment strategy. However, eliciting a robust therapeutic effect with personalized vaccines remains a challenge because of the weak immunogenicity of autologous tumor antigens. Utilizing exogenous prokaryotic constituents that act as adjuvants to enhance immunogenicity is a promising strategy to overcome this limitation. However, nonspecific stimulation of the immune system may elicit an undesirable immunopathological state. To specifically trigger sufficient antitumor reactivity without notable adverse effects, we developed an antigen and adjuvant codelivery nanoparticle vaccine based on Escherichia coli cytoplasmic membranes (EMs) and tumor cell membranes (TMs) from resected autologous tumor tissue. Introduction of the EM into the hybrid membrane nanoparticle vaccines (HM-NPs) induced dendritic cell maturation, thus activating splenic T cells. HM-NPs showed efficacy in immunogenic CT26 colon and 4T1 breast tumor mouse models and also efficiently induced tumor regression in B16-F10 melanoma and EMT6 breast tumor mouse models. Furthermore, HM-NPs provoked a strong tumor-specific immune response, which not only extended postoperative animal survival but also conferred long-term protection (up to 3 months) against tumor rechallenge in a CT26 colon tumor mouse model. Specific depletion of different immune cell populations revealed that CD8⁺ T and NK cells were crucial to the vaccine-elicited tumor regression. Individualized autologous tumor antigen vaccines based on effective activation of the innate immune system by bacterial cytoplasmic membranes hold great potential for personalized treatment of postoperative patients with cancer.

Doxorubicin and PD-L1 siRNA co-delivery with stem cell membrane-coated polydopamine nanoparticles for the targeted chemoimmunotherapy of PCa bone metastases

Programmed cell death ligand 1 (PD-L1) blockade has achieved great success in cancer immunotherapy. PD-L1 siRNA can restore the immune anti-tumor activity of T cells by downregulating the level of PD-L1 on tumor cells, but the efficiency of PD-1/PD-L1 monotherapy is relatively low. Doxorubicin (DOX) can induce tumor cell apoptosis, and then increase the release of tumor antigen. But the expression of PD-L1 in tumor tissues treated with DOX will be enhanced adaptively. Therefore, DOX combination with PD-L1 siRNA can produce a good synergistic anti-tumor effect. In this study, stem cell membrane (SCM) camouflaged polydopamine nanoparticles carrying DOX and PD-L1 siRNA (PDA-DOX/siPD-L1@SCM) were constructed for targeting prostate cancer (PCa) bone metastases. PDA-DOX/siPD-L1@SCM NPs could effectively enhance blood retention and improve accumulation at tumor sites. In vitro and in vivo studies demonstrated that PDA-DOX/siPD-L1@SCM NPs showed excellent performance in synergistic chemoimmunotherapy for PCa bone metastases. Hence, this study provided an effective strategy for developing biomimetic multifunctional nanoparticles for PCa bone metastasis treatment.

Biocompatibility of nanomaterials and their immunological properties

Nanomaterials (NMs) have revolutionized multiple aspects of medicine by enabling novel sensing, diagnostic, and therapeutic approaches. Advancements in processing and fabrication have also allowed significant expansion in the applications of the major classes of NMs based on polymer, metal/metal oxide, carbon, liposome, or multi-scale macro-nano bulk materials. Concomitantly, concerns regarding the nanotoxicity and overall biocompatibility of NMs have been raised. These involve putative negative effects on both patients and those subjected to occupational exposure during manufacturing. In this review, we describe the current state of testing of NMs including those that are in clinical use, in clinical trials, or under development. We also discuss the cellular and molecular interactions that dictate their toxicity and biocompatibility. Specifically, we focus on the reciprocal interactions between NMs and host proteins, lipids, and sugars and how these induce responses in immune and other cell types leading to topical and/or systemic effects.

PD-L1 siRNA Theranostics With a Dextran Nanoparticle Highlights the Importance of Nanoparticle Delivery for Effective Tumor PD-L1 Downregulation

Purpose

The inhibition of immune checkpoints such as programmed cell death ligand-1 (PD-L1/CD274) with antibodies is providing novel opportunities to expose cancer cells to the immune system. Antibody based checkpoint blockade can, however, result in serious autoimmune complications because normal tissues also express immune checkpoints. As sequence-specific gene-silencing agents, the availability of siRNA has significantly expanded the specificity and range of “druggable” targets making them promising agents for precision medicine in cancer. Here, we have demonstrated the ability of a novel biodegradable dextran based theranostic nanoparticle (NP) to deliver siRNA downregulating PD-L1 in tumors. Optical imaging highlighted the importance of NP delivery and accumulation in tumors to achieve effective downregulation with siRNA NPs, and demonstrated low delivery and accumulation in several PD-L1 expressing normal tissues.

Methods

The dextran scaffold was functionalized with small molecules containing amine groups through acetal bonds. The NP was decorated with a Cy5.5 NIR probe allowing visualization of NP delivery, accumulation, and biodistribution. MDA-MB-231 triple negative human breast cancer cells were inoculated orthotopically or subcutaneously to achieve differences in vascular delivery in the tumors. Molecular characterization of PD-L1 mRNA and protein expression in cancer cells and tumors was performed with qRT-PCR and immunoblot analysis.

Results

The PD-L1 siRNA dextran NPs effectively downregulated PD-L1 in MDA-MB-231 cells. We identified a significant correlation between NP delivery and accumulation, and the extent of PD-L1 downregulation, with in vivo imaging. The size of the NP of ~ 20 nm allowed delivery through leaky tumor vasculature but not through the vasculature of high PD-L1 expressing normal tissue such as the spleen and lungs.

Conclusions

Here we have demonstrated, for the first time, the feasibility of downregulating PD-L1 in tumors using siRNA delivered with a biodegradable dextran polymer that was decorated with an imaging reporter. Our data demonstrate the importance of tumor NP delivery and accumulation in achieving effective downregulation, highlighting the importance of imaging in siRNA NP delivery. Effective delivery of these siRNA carrying NPs in the tumor but not in normal tissues may mitigate some of the side-effects of immune checkpoint inhibitors by sparing PD-L1 inhibition in these tissues.

PD-1 siRNA-Encapsulated Solid Lipid Nanoparticles Downregulate PD-1 Expression by Macrophages and Inhibit Tumor Growth : PD-1 siRNA-Encapsulated Solid Lipid Nanoparticles

The present study was designed to test the hypothesis that programmed cell death-1 (PD-1) siRNA can downregulate PD-1 expression in macrophages in culture and in tumor tissues in mice and inhibit tumor growth in a mouse model. PD-1 siRNA was encapsulated in solid lipid nanoparticles (SLNs), and the physical properties of the resultant SLNs were characterized. The ability of the PD-1 siRNA-SLNs to downregulate PD-1 expression was confirmed in J774A.1 macrophages in culture and in tumor tissues in mice. Moreover, the antitumor activity of the PD-1 siRNA-SLNs was evaluated in a mouse model. The PD-1 siRNA-SLNs were roughly spherical, and their particle size, polydispersity index, and zeta potential were 141 ± 5 nm, 0.17 ± 0.02, and 20.7 ± 4.7 mV, respectively, with an siRNA entrapment efficiency of 98.9%. The burst release of the PD-1 siRNA from the SLNs was minimal. The PD-1 siRNA-SLNs downregulated PD-1 expression on J774A.1 macrophage cell surface as well as in macrophages in B16-F10 tumors pre-established in mice. In mice with pre-established B16-F10 tumors, the PD-1 siRNA-SLNs significantly inhibited the tumor growth, as compared with siRNA-SLNs prepared with non-functional, negative control siRNA. In conclusion, the PD-1 siRNA-SLNs inhibited tumor growth, likely related to their ability to downregulate PD-1 expression by tumor-associated macrophage (TAMs).

Gated Resonance Energy Transfer (gRET) Controlled by Programmed Death Protein Ligand 1

The resonance energy transfer (RET) between an excited fluorescent probe molecule and a plasmonic nanoparticle (AuNP) has been investigated to evaluate the effect of protein molecules on the RET efficiency. We have found that the energy transfer to a functionalized AuNP can be modulated by a sub-monolayer film of programmed death-ligand 1 (PD-L1) protein. The interactions of PD-L1 with AuNP@Cit involve incorporation of the protein in AuNP shell and formation of a submonolayer adsorption film with voids enabling gated surface plasmon resonance energy transfer (SPRET). A model of the gated-RET system based on the protein size, estimated using Fisher-Polikarpov-Craievich density approximation, has been developed and can be utilized for other proteins, with minimum data requirement, as well. The value of the equilibrium constant KL determined for the Langmuir isotherm is high: KL = 1.27 × 108 M-1, enabling highly sensitive control of the gated-RET by PD-L1. Thus, with the gated-RET technique, one can determine PD-L1 within the dynamic range, extending from 1.2 to 50 nM. Moreover, we have found that the Gibbs free energy for PD-L1 binding to AuNP@Cit is -46.26 kJ/mol (-11.05 kcal/mol), indicating a strong adsorption with supramolecular interactions. The proposed gated-RET system, with the fluorescence intensity of the fluorophore probe molecule modulated by plasmonic quenching with AuNP and shielding of energy transfer by the adsorbed PD-L1 can be further developed for determination of PD-L1 in pharmaceutical formulations for immune checkpoint control in cancer therapy.

Aptamer-conjugated PLGA nanoparticles for delivery and imaging of cancer therapeutic drugs

Most problems associated with chemotherapeutic agents involve non-specific cytotoxicity, low intratumoral accumulation and drug resistance. Targeted drug delivery systems (TDDS) based on nanoparticles (NPs) are a new strategy for better therapeutic efficiency, along with reduction of side effects commonly seen with cancer drugs. Poly (lactic-co-glycolic acid) (PLGA), as one of the furthest developed synthetic polymer, has gained significant attention because of excellent properties-including biodegradability and biocompatibility, controlled release of drug, protection of drug or gene from decomposition and ability to modify surface with targeting agents for both cancer diagnosis and therapy. Aptamers are single-stranded RNA or DNA that can fold through intramolecular interactions into specific three-dimensional structures to selectively and exclusively bind with interested biomarkers. In this review, we explain the latest developments regarding the application of aptamer-decorated PLGA NPs in delivery of therapeutic agents or cancer-related genes into cancer cells. Additionally, we discuss the most recent efforts in the field of aptamer-grafted PLGA-based NPs as theranostics and stimuli-responsive agents.