Cancer immunotherapy modulates immune cells to induce antitumor immune responses. Tumors employ immune checkpoints to evade immune cell attacks. Immune checkpoint inhibitors such as anti-PD-L1 antibody (aPD-L1), which is being used clinically for cancer treatments, can block immune checkpoints so that the immune system can attack tumors. However, immune checkpoint inhibitor therapy may be hampered by polarization of macrophages within the tumor microenvironment (TME) into M2 tumor-associated macrophages (TAMs), which suppress antitumor immune responses and promote tumor growth by releasing anti-inflammatory cytokines and angiogenic factors. In this study, we used exosome-mimetic nanovesicles derived from M1 macrophages (M1NVs) to repolarize M2 TAMs to M1 macrophages that release pro-inflammatory cytokines and induce antitumor immune responses and investigated whether the macrophage repolarization can potentiate the anticancer efficacy of aPD-L1. M1NV treatment induced successful polarization of M2 macrophages to M1 macrophages in vitro and in vivo. Intravenous injection of M1NVs into tumor-bearing mice suppressed tumor growth. Importantly, injection of a combination of M1NVs and aPD-L1 further reduced the tumor size, compared to the injection of either M1NVs or aPD-L1 alone. Thus, our study indicates that M1NV injection can repolarize M2 TAMs to M1 macrophages and potentiate antitumor efficacy of the checkpoint inhibitor therapy.

Human mesenchymal stem cell (hMSC)-derived exosomes have been spotlighted as a promising therapeutic agent for cell-free regenerative medicine. However, poor organ-targeting ability and insufficient therapeutic efficacy of systemically injected hMSC-exosomes were identified as critical limitations for their further applications. Therefore, in this study we fabricated iron oxide nanoparticle (IONP)-incorporated exosome-mimetic nanovesicles (NV-IONP) from IONP-treated hMSCs and evaluated their therapeutic efficacy in a clinically relevant model for spinal cord injury. Compared to exosome-mimetic nanovesicles (NV) prepared from untreated hMSCs, NV-IONP not only contained IONPs which act as a magnet-guided navigation tool but also carried greater amounts of therapeutic growth factors that can be delivered to the target cells. The increased amounts of therapeutic growth factors inside NV-IONP were attributed to IONPs that are slowly ionized to iron ions which activate the JNK and c-Jun signaling cascades in hMSCs. In vivo systemic injection of NV-IONP with magnetic guidance significantly increased the amount of NV-IONP accumulating in the injured spinal cord. Accumulated NV-IONP enhanced blood vessel formation, attenuated inflammation and apoptosis in the injured spinal cord, and consequently improved spinal cord function. Taken together, these findings highlight the development of therapeutic efficacy-potentiated extracellular nanovesicles and demonstrate their feasibility for repairing injured spinal cord.

Because of poor engraftment and safety concerns regarding mesenchymal stem cell (MSC) therapy, MSC-derived exosomes have emerged as an alternative cell-free therapy for myocardial infarction (MI). However, the diffusion of exosomes out of the infarcted heart following injection and the low productivity limit the potential of clinical applications. Here, we developed exosome-mimetic extracellular nanovesicles (NVs) derived from iron oxide nanoparticles (IONPs)–incorporated MSCs (IONP-MSCs). The retention of injected IONP-MSC–derived NVs (IONP-NVs) within the infarcted heart was markedly augmented by magnetic guidance. Furthermore, IONPs significantly increased the levels of therapeutic molecules in IONP-MSCs and IONP-NVs, which can reduce the concern of low exosome productivity. The injection of IONP-NVs into the infarcted heart and magnetic guidance induced an early shift from the inflammation phase to the reparative phase, reduced apoptosis and fibrosis, and enhanced angiogenesis and cardiac function recovery. This approach can enhance the therapeutic potency of an MSC-derived NV therapy.

immune surveillance, cytotoxic immune cells such as T lymphocytes (CTLs) play crucial roles. CTLs can migrate to inflamed tumor sites via interactions with tumor vasculatures through adhesion proteins (e.g., lymphocyte functionassociated antigen 1; LFA-1). [4] Upon T cell receptor (TCR)-mediated recognition of tumor antigens presented on major histocompatibility complex molecules, CTLs can eliminate malignant cells by secreting cytotoxic molecules (e.g., granzyme) and providing the Fas ligand (FasL) signal. [5-8] Infusion of ex vivo expanded tumorreactive CTLs or TCR-engineered T cells (e.g., chimeric antigen receptor cells) has shown impressive clinical outcomes. [9,10] The selection of the appropriate target tumor antigens and proper ex vivo expansion of the T cells are essential for the success of adoptive T cell transfer therapy. [11] However, there are several obstacles in adoptive T cell transfer therapy, including expensive and labor-intensive procedures for ex vivo expansion of T cells, loss of target tumor antigens due to cancer immunoediting, antigens heterogeneity among individual patients, and the immunosuppressive nature of Cancer immunotherapies, including adoptive T cell transfer and immune checkpoint blockades, have recently shown considerable success in cancer treatment. Nevertheless, transferred T cells often become exhausted because of the immunosuppressive tumor microenvironment. Immune checkpoint blockades, in contrast, can reinvigorate the exhausted T cells; however, the therapeutic efficacy is modest in 70-80% of patients. To address some of the challenges faced by the current cancer treatments, here T-cell-membrane-coated nanoparticles (TCMNPs) are developed for cancer immunotherapy. Similar to cytotoxic T cells, TCMNPs can be targeted at tumors via T-cell-membraneoriginated proteins and kill cancer cells by releasing anticancer molecules and inducing Fas-ligand-mediated apoptosis. Unlike cytotoxic T cells, TCMNPs are resistant to immunosuppressive molecules (e.g., transforming growth factor-β1 (TGF-β1)) and programmed death-ligand 1 (PD-L1) of cancer cells by scavenging TGF-β1 and PD-L1. Indeed, TCMNPs exhibit higher therapeutic efficacy than an immune checkpoint blockade in melanoma treatment. Furthermore, the anti-tumoral actions of TCMNPs are also demonstrated in the treatment of lung cancer in an antigen-nonspecific manner. Taken together, TCMNPs have a potential to improve the current cancer immunotherapy.

Chimeric antigen receptor‐T (CAR‐T) cell immunotherapy has shown impressive clinical outcomes for hematologic malignancies. However, its broader applications are challenged due to its complex ex vivo cell‐manufacturing procedures and low therapeutic efficacy against solid tumors. The limited therapeutic effects are partially due to limited CAR‐T cell infiltration to solid tumors and inactivation of CAR‐T cells by the immunosuppressive tumor microenvironment. Here, a facile approach is presented to in vivo program macrophages, which can intrinsically penetrate solid tumors, into CAR‐M1 macrophages displaying enhanced cancer‐directed phagocytosis and anti‐tumor activity. In vivo injected nanocomplexes of macrophage‐targeting nanocarriers and CAR‐interferon‐γ‐encoding plasmid DNA induce CAR‐M1 macrophages that are capable of CAR‐mediated cancer phagocytosis, anti‐tumor immunomodulation, and inhibition of solid tumor growth. Together, this study describes an off‐the‐shelf CAR‐macrophage therapy that is effective for solid tumors and avoids the complex and costly processes of ex vivo CAR‐cell manufacturing.