Extracellular-Vesicle-Based Drug Delivery Systems for Enhanced Antitumor Therapies through Modulating the Cancer-Immunity Cycle

Although immunotherapy harnessing activity of the immune system against tumors has made great progress, the treatment efficacy remains limited in most cancers. Current anticancer immunotherapy is primarily based on T-cell-mediated cellular immunity, which highly relies on efficiency of triggering the cancer-immunity cycle, namely, tumor antigen release, antigen presentation by antigen presenting cells, T cell activation, recruitment and infiltration of T cells into tumors, and recognition and killing of tumor cells by T cells. Unfortunately, these immunotherapies are restricted by inefficient drug delivery and acting on only a single step of the cancer-immunity cycle. Due to high biocompatibility, low immunogenicity, intrinsic cell targeting, and easy chemical and genetic manipulation, extracellular vesicle (EV)-based drug delivery systems are widely used to amplify anticancer immune responses by serving as an integrated platform for multiple drugs or therapeutic strategies to synergistically activate several steps of cancer-immunity cycle. This review summarizes various mechanisms related to affecting cancer-immunity cycle disorders. Meanwhile, preparation and application of EV-based drug delivery systems in modulating cancer-immunity cycle are introduced, especially in the improvement of T cell recruitment and infiltration into tumors. Finally, opportunities and challenges of EV-based drug delivery systems in translational clinical applications are briefly discussed.

The potential applications of microparticles in the diagnosis, treatment, and prognosis of lung cancer

Microparticles (MPs) are 100–1000 nm heterogeneous submicron membranous vesicles derived from various cell types that express surface proteins and antigenic profiles suggestive of their cellular origin. MPs contain a diverse array of bioactive chemicals and surface receptors, including lipids, nucleic acids, and proteins, which are essential for cell-to-cell communication. The tumour microenvironment (TME) is enriched with MPs that can directly affect tumour progression through their interactions with receptors. Liquid biopsy, a minimally invasive test, is a promising alternative to tissue biopsy for the early screening of lung cancer (LC). The diverse biomolecular information from MPs provides a number of potential biomarkers for LC risk assessment, early detection, diagnosis, prognosis, and surveillance. Remodelling the TME, which profoundly influences immunotherapy and clinical outcomes, is an emerging strategy to improve immunotherapy. Tumour-derived MPs can reverse drug resistance and are ideal candidates for the creation of innovative and effective cancer vaccines. This review described the biogenesis and components of MPs and further summarised their main isolation and quantification methods. More importantly, the review presented the clinical application of MPs as predictive biomarkers in cancer diagnosis and prognosis, their role as therapeutic drug carriers, particularly in anti-tumour drug resistance, and their utility as cancer vaccines. Finally, we discussed current challenges that could impede the clinical use of MPs and determined that further studies on the functional roles of MPs in LC are required.

Extracellular vesicles for improved tumor accumulation and penetration

Extracellular vesicles (EVs), including microparticles and exosomes, have emerged as potential tools for tumor targeting delivery during the past years. Recently, mass of strategies are applied to assist EVs to accumulate and penetrate into deep tumor sites. In this review, EVs from different cells with unique innate characters and engineered approaches (e.g. chemical engineering, genetical engineering and biomimetic engineering) as drug delivery systems to enhance tumor accumulation and penetration are summarized. Meanwhile, efficient biological function modulation (e.g. extracellular matrix degradation, mechanical property regulation and transcytosis) is introduced to facilitate tumor accumulation and penetration of EVs. Finally, the prospects and challenges on further clinical applications of EVs are discussed.

PAI/MRI Visualization of Tumor Derived Cellular Microvesicles with Endogenous Biopolymer Nanoparticles Modification

Background

Tumor derived cellular microvesicles (TDMVs), as excellent drug delivery vehicles in vivo, play an important role in the treatment of cancers. However, it is difficult to obtain intuitional biodistribution behavior and internalization mechanisms of TDMVs in vivo. Thus, it is very urgent and important to establish a stable and reliable visualization technology to track the biological behavior and function of TDMVs. As an endogenous biopolymer, melanin possesses natural biocompatibility and biodegradability, and various biological imaging could be realized by modifying it. Therefore, melanin-based nanoparticles are excellent candidates for in vivo visualization of TDMVs.

Methods

In this work, the biodistribution and metabolic behavior of TDMVs were visualized by dual-modality imaging with PAI and MRI after incubation with gadolinium ion-chelated melanin nanoparticles.

Results

In this study, MRI and PAI dual-modality imaging of the in vivo distribution behavior of TDMVs was achieved with the help of MNP-Gd. The good targeting ability of TDMVs at the homologous tumor site was observed, and their distribution and metabolism behavior in the whole body were studied at the meantime. The results indicated that TDMVs preferentially accumulated in syngeneic tumor sites and liver regions after intravenous injection and were eventually metabolized by the kidneys over time.

Conclusion

This work proposed a novel dual-modal imaging strategy for the visualization of TDMVs, which is of great significance for further understanding the biological mechanisms of extracellular vesicles.

Adenosine triphosphate/pH dual-responsive controlled drug release system with high cancer/normal cell selectivity and low side toxicity

Most drug-delivery systems (DDS) suffer from poor selectivity to cancer/normal cells or the complicated synthetic process. Herein, we employed a novel facile method to develop an oligodeoxy nucleotides based DDS composed with adenosine-5′- triphosphate (ATP) aptamer and a pH responsive cytosine (C) DNA fragment for specific daunomycine (DNM) delivery. The DDS has ATP/pH dual-responsive drug release, can selectively internalize into tumor cell lines and thus has ultrahigh cancer/normal cell selectivity over the individual drug. The non-chemical synthesis, controllable dual-responsive intracellular drug release, and high cancer/normal cell selectivity endowed the DDS high biocompatibility and significant tumor suppression.

Rational Design of Nanotherapeutics Based on the Five Features Principle for Potent Elimination of Cancer Stem Cells

Cancer stem cells (CSCs), also known as tumor initiating cells or tumor repopulating cells, which comprise only a small fraction of tumor, have received tremendous attention during the past two decades, as they are considered as the ringleader for initiation and progression of tumors, therapy resistance, metastasis, and recurrence in the clinic. Hence, eradicating CSCs is critical for successful cancer treatment. To that end, various CSC-targeting therapeutic agents have been pursued. However, these CSC-specific drugs are ineffective toward bulk cancer cells. Furthermore, these anti-CSC drugs not only eradicate CSCs but also affect conventional stem cells in normal organs or tissues. By virtue of the enhanced permeability and retention (EPR) effect, nanomaterial drug delivery systems (NDDSs) passively accumulate in tumor tissues, thereby alleviating severe side effects toward normal viscera. NDDSs can be further functionalized with CSC-specific binding molecules to promote targeted drug delivery toward CSCs. Moreover, NDDSs have unique advantages in encapsulating CSC-specific drugs and cytotoxic agents, realizing synchronized killing of CSCs and bulk cancer cells both temporally and spatially. For these reasons, leveraging nanotherapeutic strategies to target CSCs has gained tremendous attention recently.Some ten years ago, we summarized five basic features of efficient nanotherapeutics (the five features principle), which consist of long circulation, tumor accumulation, deep penetration, cellular internalization, and drug release. Based on this design rationale, we constructed several NDDSs, including nanogels with adaptive hydrophobicity, CSC-derived microparticles with tailored softness, and tumor exosome sheathed porous silicon biomimetic nanoparticles, for targeted drug delivery to tumor. To our astonishment, these NDDSs that possess the five basic features achieve decent drug delivery efficiency toward not only bulk tumor cells but more importantly CSCs. Consequently, such nanotherapeutics as-designed based on the five features principle are potent in eradicating CSCs, even with only cytotoxic drugs, for instance, doxorubicin. Furthermore, commercialized nanomedicines, such as Doxil and Abraxane, can be endowed with these five basic features by hyperbaric oxygen therapy and therefore achieve outstanding drug delivery efficiency, potent CSC elimination, and efficient cancer therapy. These studies suggest that intractable CSCs can be tackled with a material-based approach, highlight the critical role of the five features principle in designing effective nanotherapeutics, and pinpoint the significance of drug delivery efficiency in eliminating CSCs and bulk cancer cells.

Injectable and Biodegradable Chitosan Hydrogel-Based Drug Depot Contributes to Synergistic Treatment of Tumors

Combined therapy provides a more effective method in the treatment of tumors and becomes a research hotspot. To improve treatment outcomes and reduce serious side effects, hydrogel-based local delivery was developed herein to form a drug depot in suit to eliminate tumors. Indocyanine green and imiquimod were coencapsulated in the novel temperature-sensitive chitosan hydrogel. After intratumoral injection of the hydrogel, indocyanine green that accumulated in the tumor area could induce thermal ablation of primary tumors under laser irradiation. In the presence of imiquimod, the immune effects increased the probability of complete ablation of primary tumors and inhibition of metastases. Combined with cyclophosphamide, the enhanced immunological responses would further inhibit tumors and prolong the survival time. In a word, this work offered an excellent local delivery platform that enabled a remarkable combined antitumor strategy and achieved synergistic therapeutic effects.

Roles of Microvesicles in Tumor Progression and Clinical Applications

Microvesicles are extracellular vesicles with diameter ranging from 100 to 1000 nm that are secreted by tumor cells or other cells in the tumor microenvironment. A growing number of studies demonstrate that tumor-derived microvesicles are involved in tumor initiation and progression, as well as drug resistance. In addition, tumor-derived microvesicles carry a variety of immunogenic molecules and inhibit tumor response to immunotherapy; therefore, they can be exploited for use in tumor vaccines. Moreover, because of their high stability, tumor-derived microvesicles extracted from body fluids can be used as biomarkers for cancer diagnosis or assessment of prognosis. Tumor-derived microvesicles can also be deployed to reverse drug resistance of tumor regenerative cells, or to deliver chemotherapeutic drugs and oncolytic adenovirus for the treatment of cancer patients. This review summarizes the general characteristics of tumor-derived microvesicles, focusing on their biological characteristics, their involvement in tumor progression, and their clinical applications.

Engineering nanomedicine for glutathione depletion-augmented cancer therapy

Glutathione (GSH), the main redox buffer, has long been recognized as a pivotal modulator of tumor initiation, progression and metastasis. It is also implicated in the resistance of platinum-based chemotherapy and radiation therapy. Therefore, depleting intracellular GSH was considered a potent solution to combating cancer. However, reducing GSH within cancer cells alone always failed to yield desirable therapeutic effects. In this regard, the convergence of GSH-scavenging agents with therapeutic drugs has thus been pursued in clinical practice. Unfortunately, the therapeutic outcomes are still unsatisfactory due to untargeted drug delivery. Advanced nanomedicine of synergistic GSH depletion and cancer treatment has attracted tremendous interest because they promise to deliver superior therapeutic benefits while alleviating life-threatening side effects. In the past five years, the authors and others have demonstrated that numerous nanomedicines, by simultaneously delivering GSH-depleting agents and therapeutic components, boost not only traditional chemotherapy and radiotherapy but also multifarious emerging treatment modalities, including photodynamic therapy, sonodynamic therapy, chemodynamic therapy, ferroptosis, and immunotherapy, to name a few, and achieved decent treatment outcomes in a large number of rodent tumor models. In this review, we summarize the most recent progress in engineering nanomedicine for GSH depletion-enhanced cancer therapies. Biosynthesis of GSH and various types of GSH-consuming strategies will be briefly introduced. The challenges and perspectives of leveraging nanomedicine for GSH consumption-augmented cancer therapies will be discussed at the end.