Natural killer cell‐derived extracellular vesicles (NK‐EVs) have shown promising potential as biotherapeutics for cancer due to their unique attributes as cytotoxic nanovesicles against cancer cells and immune‐modulatory activity towards immune cells. However, a biomanufacturing workflow is needed to produce clinical‐grade NK‐EVs for pre‐clinical and clinical applications. This study established a novel biomanufacturing workflow using a closed‐loop hollow‐fibre bioreactor to continuously produce NK‐EVs from the clinically relevant NK92‐MI cell line under serum‐free, Xeno‐free and feeder‐free conditions following GMP‐compliant conditions. The NK92 cells grown in the bioreactor for three continuous production lots resulted in large quantities of both NK cell and NK‐EV biotherapeutics at the end of each production lot (over 10⁹ viable cells and 10¹³ EVs), while retaining their cytotoxic payload (granzyme B and perforin), pro‐inflammatory cytokine (interferon‐gamma) content and cytotoxicity against the human leukemic cell line K562 with limited off‐target toxicity against healthy human fibroblast cells. This scalable biomanufacturing workflow has the potential to facilitate the clinical translation of adoptive NK cell‐based and NK‐EV‐based immunotherapies for cancer with GMP considerations.

Triple-negative breast cancer (TNBC) is considered one of the most aggressive forms of breast cancer with poor survival rates compared to other breast cancer subtypes. TNBC is characterized by the absence of the estrogen receptor alpha, progesterone receptor, and the human epidermal growth factor receptor 2, limiting those viable treatment options available to patients with other breast cancer subtypes. Furthermore, due to the particularly high heterogeneity of TNBC, conventional treatments such as chemotherapy are not universally effective, leading to drug resistance and intolerable side effects. Thus, there is a pressing need to discover new therapies beneficial to TNBC patients. This review highlights current findings regarding the roles of three steroid hormone receptors, estrogen receptor beta, the androgen receptor, and the glucocorticoid receptor, in the progression of TNBC. In addition, we discussed several ongoing and completed clinical trials targeting these hormone receptors in TNBC patients.

Multipotent mesenchymal stromal cell (MSC) transplantation is proposed as a novel therapy for treating diabetes by promoting the regeneration of damaged islets. The clinical promise of such treatments may be hampered by a high degree of donor-related variability in MSC function and a lack of standards for comparing potency. Here, we set out to identify markers of cultured human MSCs directly associated with islet regenerative function. Stromal cultures from nine separate bone marrow donors were demonstrated to have differing capacities to reduce hyperglycemia in the NOD/SCID streptozotocin-induced diabetic model. Regenerative (R) and non-regenerative (NR) MSC cultures were directly compared using isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics. A total of 1,410 proteins were quantified resulting in the identification of 612 upregulated proteins and 275 downregulated proteins by ± 1.2-fold in R-MSC cultures. Elastin microfibril interface 1 (EMILIN-1), integrin-linked protein kinase (ILK), and hepatoma-derived growth factor (HDGF) were differentially expressed in R-MSCs, and Ingenuity Pathway Analyses revealed each candidate as known regulators of integrin signaling. Western blot validation of EMILIN-1, ILK, and HDGF not only showed significantly higher abundance levels in R-MSCs, as compared with NR-MSCs, but also correlated with passage-induced loss of islet-regenerative potential. Generalized estimating equation modeling was applied to examine the association between each marker and blood glucose reduction. Both EMILIN-1 and ILK were significantly associated with blood glucose lowering function in vivo. Our study is the first to identify EMILIN-1 and ILK as prospective markers of islet regenerative function in human MSCs.

Progenitor cell therapy is hindered in patients with diabetes mellitus (DM) due to cellular senescence. Glycogen synthase kinase-3β (GSK3β) activity is increased in DM, potentially exacerbating impaired cell-based therapies. Thus, we aimed to determine if and how GSK3β inhibitors (GSKi) can improve therapeutic efficacy of endothelial progenitor cells (EPC) from patients with DM. Patients with DM had fewer EPCs and increased rates of apoptosis. DM EPCs also exhibited higher levels of GSK3β activity resulting in increased levels of phosphorylated β-catenin. Proteomic profiling of DM EPCs treated with GSKi identified 37 nonredundant, differentially regulated proteins. Cathepsin B (cathB) was subsequently confirmed to be differentially regulated and showed 40% less baseline activity in DM EPCs, an effect reversed by GSKi treatment. Finally, in vivo efficacy of cell-based therapy was assessed in a xenotransplant femoral wire injury mouse model. Administration of DM EPCs reduced the intima-to-media ratio, an effect that was further augmented when DM EPCs were pretreated with GSKi yet absent when cathB was antagonized. In DM, increased basal GSK3β activity contributes to accelerated EPC cellular senescence, an effect reversed by small molecule antagonism of GSK3β, which enhanced cell-based therapy after vascular injury.

Extracellular vesicles (EVs) are entering the clinical arena as novel biologics for infectious diseases, potentially serving as the immunogenic components of next generation vaccines. However, relevant human assays to evaluate the immunogenicity of EVs carrying viral antigens are lacking, contributing to challenges in translating rodent studies to human clinical trials. Here, we engineered EVs to carry SARS-CoV-2 Spike to evaluate the immunogenicity of antigen-carrying EVs using human peripheral blood mononuclear cells (PBMCs). Delivery of Spike EVs to PBMCs resulted in specific immune cell activation as assessed through T cell activation marker expression. Further, Spike EVs were taken up largely by antigen-presenting cells (monocytes, dendritic cells and B cells). Taken together, this human PBMC-based system models physiologically relevant pathways of antigen delivery, uptake and presentation. In summary, the current study highlights the suitability of using human PBMCs for evaluating the immunogenicity of EVs engineered to carry antigens for infectious disease therapeutics.

Natural killer cell‐derived extracellular vesicles (NK‐EVs) are candidate biotherapeutics against various cancers. However, standardised potency assays are necessary for a reliable assessment of NK‐EVs' cytotoxicity. This study aims to thoroughly evaluate a highly sensitive resazurin phenoxazine‐based cell viability potency assay (measurement of the cellular redox metabolism) for quantifying the cytotoxicity of NK‐EVs against leukaemia K562 cells (suspension model) and breast cancer MDA‐MB‐231 cells (adherent model) in vitro. The assay was evaluated based on common analytical parameters setforth by regulatory guidelines, including specificity, selectivity,accuracy, precision, linearity, range and stability. Our results revealed that this resazurin‐based cell viability potency assay reliably and reproducibly measured a dose‐response of NK‐EVs’ cytotoxic activity against both cancer models. The assay showed precision with 5% and 20% variation for intra‐run and inter‐run variability. The assay signal showed specificity and selectivity of NK‐EVs against cancer target cells, as evidenced by the diminished viability of cancer cells following a 5‐hour treatment with NK‐EVs, without any detectable interference or background. The linearity analysis of target cancer cells revealed strong linearity for densities of 5000 K562 and 1000 MDA‐MB‐231 cells per test with a consistent range. Importantly, NK‐EVs’ dose‐response for cytotoxicity showed a strong correlation (| ρ | ∼ 0.8) with the levels of known cytotoxic factors associated with the NK‐EVs’ corona (FasL, GNLY, GzmB, PFN and IFN‐γ), thereby validating the accuracy of the assay. The assay also distinguished cytotoxicity changes in degraded NK‐EVs, indicating the ability of the assay to detect the potential loss of sample integrity. Compared to other commonly reported bioassays (i.e., flow cytometry, cell counting, lactate dehydrogenase release assay, DNA‐binding reporter assay and confluence assay), our results support this highly sensitive resazurin‐based viability potency assay as a high‐throughput and quantitative method for assessing NK‐EVs’ cytotoxicity against both suspension and adherent cancer models for evaluating NK‐EVs’ biotherapeutics.