Natural killer (NK) cells are components of the innate immune system which play a pivotal role in cancer cell surveillance. Despite promising results in clinical trials, the use of NK‐based therapies is limited due to unsatisfactory efficiencies and safety issues. In recent years, exosomes have emerged as a powerful, natural therapeutic tool. Since exosomes are known to carry cargos that reflect the cellular makeup of their cell of origin, we were prompted to test whether NK‐derived exosomes (NKexo) maintain the anti‐leukemia capacity of NK‐cells. We found NK92MI‐cells to secrete large amounts of 100–200 nm cap‐shaped particles expressing exosomal and NK biomarkers (CD63, CD81, CD56). We demonstrated that NKexo exert a potent, selective, anti‐leukemia effect on all leukemia cell‐lines tested. Furthermore, NKexo eliminated leukemia cells isolated from patients with acute and chronic leukemia and inhibited hematopoietic colony growth. While leukemia cells were targeted and severely affected by NKexo, healthy B‐cells remained unaffected, indicating a selective effect. This selectivity was further confirmed by demonstrating that NKexo were specifically taken up by leukemic cells but not by healthy B‐cells. Our in vivo data support our in vitro and ex vivo findings and demonstrate improved human‐CD45+ leukemia blast counts and overall survival in NKexo treated humanized acute myeloid leukemia (HL‐60) xenograft mice thus supporting the assumption that NKexo possess an anti‐leukemia effect. Pending further analyses, our findings provide the pre‐clinical evidence needed to test the NKexo approach in future pre‐clinical and clinical studies to ultimately develop an acellular “off‐the‐shelf” product to treat leukemia.

Background: Immunosuppression is strongly associated with an increased risk of developing cutaneous squamous cell carcinoma (cSCC). Studies on solid organ transplant recipients (SOTR) and chronic lymphocytic leukemia (CLL) patients have already demonstrated higher rates of aggressive cSCC tumors in these populations compared to immunocompetent controls. Studies on other immunosuppressed patient groups are scarce. This study was aimed at assessing the effects of different immunomodulating conditions on patients diagnosed with cSCC. We sought to compare the clinical features, treatments, and survival rates among the different study groups, as well as outcomes to those of immunocompetent controls with cSCC. Methods: A retrospective analysis of 465 cSCC patients, both immunosuppressed (IS) and immunocompetent controls. Etiologies for immunosuppression included SOTR, CLL, chronic kidney disease (CKD), psoriasis, rheumatoid arthritis (RA) and systemic lupus erythematous (SLE). Results: Compared to the control group, IS patients demonstrated several significant differences. These include higher rates of positive resection margins, higher recurrence rates, and multiple SCC tumors. Patients in the IS group, who were also given immunomodulating agents, demonstrated even lower survival rates. Cox regression analysis demonstrated statistically significant decreased overall survival (OS) rates for IS patients compared to the controls (OR = 1.9, p = 0.031). SOTR patients tend to have multiple cSCC tumors (35%), with the highest number of primary tumors compared to controls (2.54 tumors per patient on average, p < 0.001), but also compared to all other IS groups. The average SCC lesion size in the SOTR group was the smallest, measuring at 13.5 mm, compared to the control group and all other IS groups. Decreased survival rates were seen on Cox regression analysis compared to controls (HR = 2.4, p = 0.001), but also to all other IS groups. CLL patients also had the highest rates of positive margins compared to controls (36% vs. 9%, p < 0.01) and to all other IS groups. They were also most likely to get adjuvant or definitive oncological treatments, either radiotherapy or chemotherapy, compared to controls (36% vs. 15%, p = 0.02) and to other IS groups. Patients in the CKD group demonstrated the highest rates for multiple cSCC (OR = 4.7, p = 0.001) and the worst rates of survival on Cox regression analysis (HR = 3.2, p = 0.001). Both rheumatoid arthritis and psoriasis patients demonstrated the shortest disease-free survival rates (2.9y ± 1.1, 2.3y ± 0.7, respectively), compared to controls (4.1y ± 2.8) and to all other IS groups. Conclusions: Among cSCC patients, immunosuppression due to SOTR, CLL, CKD, RA, and psoriasis is associated with worse outcomes compared to controls and other IS groups. These patients should be regarded as high-risk for developing aggressive cSCC tumors. This study is the first to assess and compare cSCC outcomes among multiple IS patient groups.

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