NK92 cells and peripheral blood NK cells respond oppositely upon dasatinib treatment

Natural killer (NK) cell is a valuable tool for immunotherapy in cancer treatment, both the cultured cell line NK92 and primary NK cells are widely studied and used in research and clinical trials. Clinical observations witnessed the improvement of patients' NK cells in terms of cell counts and cytotoxic activity upon dasatinib treatment, an approved drug for chronic myeloid leukaemia and Ph+ acute lymphocytic leukaemia. Several studies supported the clinical observations, yet others argued a detrimental effect of dasatinib on NK cells. Due to the complex conditions in different studies, the definite influence of dasatinib on NK92 and primary NK cells remains to be settled. Here, we used a well-defined in vitro system to evaluate the effects of dasatinib on NK92 cells and peripheral blood (PB)-NK cells. By co-culturing NK cells with dasatinib to test the cell counts and target cell-killing activities, we surprisingly found that the chemical influenced oppositely on these two types of NK cells. While dasatinib suppressed NK92 cell proliferation and cytotoxic activity, it improved PB-NK-killing tumour cells. RNA sequencing analysis further supported this finding, uncovering several proliferating and cytotoxic pathways responding invertedly between them. Our results highlighted an intrinsic difference between NK92 and PB-NK cells and may build clues to understand how dasatinib interacts with NK cells in vivo.

Chimeric antigen-receptor (CAR) engineered natural killer cells in a chronic myeloid leukemia (CML) blast crisis model

During the last two decades, the introduction of tyrosine kinase inhibitors (TKIs) to the therapy has changed the natural history of CML but progression into accelerated and blast phase (AP/BP) occurs in 3-5% of cases, especially in patients resistant to several lines of TKIs. In TKI-refractory patients in advanced phases, the only curative option is hematopoietic stem cell transplantation. We and others have shown the relevance of the expression of the Interleukin-2-Receptor α subunit (IL2RA/CD25) as a biomarker of CML progression, suggesting its potential use as a therapeutic target for CAR-based therapies. Here we show the development of a CAR-NK therapy model able to target efficiently a blast crisis cell line (K562). The design of the CAR was based on the scFv of the clinically approved anti-CD25 monoclonal antibody (Basiliximab). The CAR construct was integrated into NK92 cells resulting in the generation of CD25 CAR-NK92 cells. Target K562 cells were engineered by lentiviral gene transfer of CD25. In vitro functionality experiments and in vivo leukemogenicity experiments in NSG mice transplanted by K562-CD25 cells showed the efficacy and specificity of this strategy. These proof-of-concept studies could represent a first step for further development of this technology in refractory/relapsed (R/R) CML patients in BP as well as in R/R acute myeloblastic leukemias (AML).

Stem cell-assisted enzyme/prodrug therapy makes drug-resistant ovarian cancer cells vulnerable to natural killer cells through upregulation of NKG2D ligands

Cancer stem-like cells (CSCs) are believed to be responsible for cancer recurrence and metastasis. Therefore, a therapeutic approach is needed to eliminate both rapidly proliferating differentiated cancer cells and slow-growing drug-resistant CSCs. Using established ovarian cancer cells lines as well as ovarian cancer cells isolated from a patient with high-grade drug-resistant ovarian carcinoma, we demonstrate that ovarian CSCs consistently express lower levels of NKG2D ligands (MICA/B and ULBPs) on their surfaces, a mechanism by which they evade natural killer (NK) cells' surveillance. Here, we discovered that exposure of ovarian cancer (OC) cells to SN-38 followed by 5-FU not only acts synergistically to kill the OC cells, but also makes the CSCs vulnerable to NK92 cells through upregulation of NKG2D ligands. Since systemic administration of these two drugs is marred by intolerance and instability, we engineered and isolated an adipose-derived stem cell (ASC) clone, which stably expresses carboxylesterase-2 and yeast cytosine deaminase enzymes to convert irinotecan and 5-FC prodrugs into SN-38 and 5-FU cytotoxic drugs, respectively. Co-incubation of ASCs and prodrugs with drug-resistant OC cells not only led to the death of the drug-resistant OC cells but also made them significantly vulnerable to NK92 cells. This study provides proof of principle for a combined ASC-directed targeted chemotherapy with NK92-assisted immunotherapy to eradicate drug-resistant OC cells.

VEGF165b augments NK92 cytolytic activity against human K562 leukemia cells by upregulating the levels of perforin and granzyme B via the VEGR1-PLC pathway

Pro-angiogenic Vascular endothelial growth factors (VEGFs) exert immunosuppressive functions on some immune cells by interacting with VEGF receptors. Blocking the VEGF/VEGFR pathway could reverse the tumor immunosuppressive microenvironment to some degree. We recently demonstrated that the anti-angiogenic VEGF isoform VEGF165b, similar to other anti-angiogenic agents, inhibit the accumulation immunosuppressive cells such as Tregs and MDSCs. However, whether VEGF165b affects the functions of immune effector cells remain unclear. Here, NK92 cell line was utilized as an immune effector cell model. Our results verified that NK92 cells endogenously express VEGF165 and VEGFR1. Further investigation showed that NK92 treatment with VEGF165b augments its killing ability against human K562 leukemia cells by upregulating perforin and granzyme B through the VEGFR1-PLC pathway, whereas VEGF165b had no impact on the proliferation of NK92 cells in vitro. The results of this study improve our understanding of the immunomodulatory function of VEGF165b, which may help in enhancing the efficacy of NK92-based cancer immunotherapy.

A novel chimeric PD1-NKG2D-41BB receptor enhances antitumor activity of NK92 cells against human lung cancer H1299 cells by triggering pyroptosis

Chimeric antigen receptor (CAR)-modified adoptive natural killer (NK) cells represent a promising immunotherapeutic modality for cancer treatment but face many challenges in solid tumors. One major obstacle is the immune-suppressive effects induced by inhibitory receptors (IR) including PD1. To interfere with PD1 signaling to augment CAR-NK cells' activity against solid tumors, we rationally designed a novel chimeric costimulatory converting receptor (CCCR), comprising mainly the extracellular domain of PD1, transmembrane and cytoplasmic domains of NKG2D, and the cytoplasmic domain of 41BB. This NK-tailored CCCR was able to switch the negative PD1 signal to an activating signal and hence reversed the immune suppressive effects of PD1. The CCCR-modified NK92 (CCCR-NK92) cells retained typical characteristics of NK cells and exhibited enhanced antitumor activity against human lung cancer H1299 cells in vitro compared with untransduced NK92 cells. The rapid clearance of H1299 cells was caused by CCCR-NK92 cell-induced extensive pyroptosis. In a lung cancer xenograft model, CCCR-NK92 cells significantly inhibited tumor growth. Our results highlight a promising immunotherapeutic potential of using NK-tailored CCCR engineered NK92 cells to treat human lung cancer.

Target-Dependent Expression of IL12 by synNotch Receptor-Engineered NK92 Cells Increases the Antitumor Activities of CAR-T Cells

IL12 is an immune-stimulatory cytokine for key immune cells including T cells and NK cells. However, systemic administration of IL12 has serious side effects that limit its clinical application in patients. Recently, synthetic Notch (synNotch) receptors have been developed that induce transcriptional activation and deliver therapeutic payloads in response to the reorganization of specific antigens. NK92 cell is a human natural killer (NK) cell line which has been developed as tools for adjuvant immunotherapy of cancer. Here, we explored the possibility of using synNotch receptor-engineered NK92 cells to selectively secrete IL12 at the tumor site and increase the antitumor activities of chimeric antigen receptor (CAR)-modified T cells. Compared with the nuclear factor of activated T-cells (NFATs) responsive promoter, which is another regulatory element, the synNotch receptor was better at controlling the expression of cytokines. NK92 cells transduced with the GPC3-specific synNotch receptor could produce the proinflammatory cytokine IL12 (GPC3-Syn-IL12-NK92) in response to GPC3 antigen expressed in cancer cells. In vivo GPC3-Syn-IL12-NK92 cells controlling IL12 production could enhance the antitumor ability of GPC3-redirected CAR T cells and increase the infiltration of T cells without inducing toxicity. Taken together, our results demonstrated that IL12 supplementation by synNotch-engineered NK92 cells could secrete IL12 in a target-dependent manner, and promote the antitumor efficiency of CAR-T cells. Local expression of IL12 by synNotch-engineered NK92 cells might be a safe approach to enhance the clinical outcome of CAR-T cell therapy.

CD24 targeting bi-specific antibody that simultaneously stimulates NKG2D enhances the efficacy of cancer immunotherapy

PURPOSE

Bi-specific antibody (BsAb) is an emerging novel format of antibody. We aimed to develop the natural killer (NK) cell receptor NK group 2, member D (NKG2D)-mediated, immune surveillance system. In this system, the NKG2D ligand MHC class I-related chain A (MICA) was fused with BsAb, which targeted a cluster of differentiation 24 (CD24), a tumor-initiating cell marker that is over-expressed on hepatocellular carcinoma (HCC).

METHODS

The Homo MICA extracellular domains (hMICA) were fused to the end of the heavy chain of cG7 with the flexible pentapeptide (Gly-Gly-Gly-Gly-Ser; G4S), which formed the cG7-MICA that was further identified using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting (WB). The targeting specificity was characterized using the Surface Plasmon Resonance (SPR) technology and a flow cytometry assay. Furthermore, the design of BsAb cG7-MICA that targeted CD24 and NKG2D was proven to enhance antibody-dependent, cell-mediated cytotoxicity (ADCC) in vitro by the CytoTox 96 Nonradioactive Cytotoxicity assay. Degranulation and a cytokine production assay of NK cells demonstrated that NK cells were activated effectively by cG7-MICA. Further, in HCC-bearing nude mice, the anti-tumor effects of cG7-MICA combined with sorafenib were verified again.

RESULTS

We purified cG7-MICA successfully, and it has a high affinity. In vivo, cG7-MICA recruited NK cells to the tumor site and improved the anti-tumor efficacy of sorafenib. cG7-MICA also activated NK cells to release interferon γ (IFN-γ) and tumor necrosis factor α (TNF-α), and it increased the CD107a expression on the surface of the NK cells in vitro.

CONCLUSION

NK cells play a major role in the natural, innate immune system, and they have the function of identifying and killing target cells. cG7-MICA remodels the function of MICA molecules to activate NK cells, which provides a possible strategy for HCC-targeting immunotherapy.

In vitro Evidence That Combination Therapy With CD16-Bearing NK-92 Cells and FDA-Approved Alefacept Can Selectively Target the Latent HIV Reservoir in CD4+ CD2hi Memory T Cells

Elimination of the latent HIV reservoir remains the biggest hurdle to achieve HIV cure. In order to specifically eliminate HIV infected cells they must be distinguishable from uninfected cells. CD2 was recently identified as a potential marker enriched in the HIV-1 reservoir on CD4+ T cells, the largest, longest-lived and best-characterized constituent of the HIV reservoir. We previously proposed to repurpose FDA-approved alefacept, a humanized α-CD2 fusion protein, to reduce the HIV reservoir in CD2hi CD4+ memory T cells. Here, we show the first evidence that alefacept can specifically target and reduce CD2hi HIV infected cells in vitro. We explore a variety of natural killer (NK) cells as mediators of antibody-dependent cell-mediated cytotoxicity (ADCC) including primary NK cells, expanded NK cells as well as the CD16 transduced NK-92 cell line which is currently under study in clinical trials as a treatment for cancer. We demonstrate that CD16.NK-92 has a natural preference to kill CD2hi CD45RA- memory T cells, specifically CD45RA- CD27+ central memory/transitional memory (TCM/TM) subset in both healthy and HIV+ patient samples as well as to reduce HIV DNA from HIV+ samples from donors well controlled on antiretroviral therapy. Lastly, alefacept can combine with CD16.NK-92 to decrease HIV DNA in some patient samples and thus may yield value as part of a strategy toward sustained HIV remission.