Research progress on immunotherapy based on NK cells for hepatocellular carcinoma / 细胞与分子免疫学杂志

Hepatocellular carcinoma (HCC) is well characterized as a heterogeneous disease. Its late-stage diagnosis and chemotherapy resistance make it one of the refractory tumors in China. Natural killer (NK) cells play a significant role in immune surveillance. However, NK cells become dysfunctional in the progression of HCC, leading to tumor immune escape. This article reviews the recent progress on different strategies of NK cell-based immunotherapy in treating HCC, including direct adoptive NK cell transfer, gene engineering in NK cell, NK cell receptor targeting, immunosuppressive microenvironment modification, and tumor toxicity enhancement by cytokines or traditional Chinese medicine. These NK cell-based strategies have shown promising therapeutic potential.

CD226, TIGIT and CD96 regulate NK cell function and participate in anti-tumor immunity / 细胞与分子免疫学杂志

CD226 is an activated receptor on the surface of natural killer (NK) cells. It competes with TIGIT and CD96 to bind to ligands such as CD155 on the surface of tumor cells and mediates the killing function of NK cells. Although TIGIT and CD96 have other binding ligands in the tumor microenvironment, they compete to bind CD115 ligands with higher affinity and inhibit the activity of NK cells, which allows tumor cells to evade killing. Therefore, studying the expression patterns of these three NK cell surface receptors in different tumors and monitoring their binding ability with ligands will help us to explore new tumor treatment strategies. This article reviews the role and mechanism of CD226, TIGIT, CD96 and other NK cell receptor molecules in regulating NK cell function in anti-tumor immune response.

Molecular checkpoints controlling natural killer cell activation and their modulation for cancer immunotherapy

Natural killer (NK) cells have gained considerable attention as promising therapeutic tools for cancer therapy due to their innate selectivity against cancer cells over normal healthy cells. With an array of receptors evolved to sense cellular alterations, NK cells provide early protection against cancer cells by producing cytokines and chemokines and exerting direct cytolytic activity. These effector functions are governed by signals transmitted through multiple receptor–ligand interactions but are not achieved by engaging a single activating receptor on resting NK cells. Rather, they require the co-engagement of different activating receptors that use distinct signaling modules, due to a cell-intrinsic inhibition mechanism. The redundancy of synergizing receptors and the inhibition of NK cell function by a single class of inhibitory receptor suggest the presence of common checkpoints to control NK cell activation through different receptors. These molecular checkpoints would be therapeutically targeted to harness the power of NK cells against diverse cancer cells that express heterogeneous ligands for NK cell receptors. Recent advances in understanding the activation of NK cells have revealed promising candidates in this category. Targeting such molecular checkpoints will facilitate NK cell activation by lowering activation thresholds, thereby providing therapeutic strategies that optimize NK cell reactivity against cancer.

NK cell surface receptors and their research progress - review / 中国实验血液学杂志

Natural killer (NK) cells are important immune cells in human body, which occupy an important place in adoptive immunotherapy for patients with malignancies due to their capacity of killing tumor cells without MHC limitation, as well as separating graft versus leukemia (GVL) and graft versus host disease (GVHD). Recent studies showed that different kinds of NK cell-surface receptors have been found, which transmit inhibiting signals or activating signals, the balance between them determines the functional status of NK cells. Researchers have focused on the study of NK cell-surface receptors recently in order to improve application of NK cells for adoptive immunotherapy. This review summaries the current advancement about NK cell-surface receptors and their clinical significance.

Reconstitution of NK cells and their receptors in patients with acute leukemia following unrelated cord blood stem cell transplantation / 中国实验血液学杂志

This study was to investigate the reconstitution of NK cells and their receptors after unrelated cord blood stem cell transplantation (UCBT) and its clinical importance. 11 cases of acute leukemia underwent UCBT were enrolled in this study. The reconstitution of NK cells and their surface receptors as well as the the recovery of T and B cells within 90 days after clinical engraftment following UCBT were measured and analysed by flow cytometry. The results indicated that the recovery of NK cells appears to be relatively early. CD3(-)56(+) NK cell count was (35.12 +/- 18.66)% of peripheral blood (PB) lymphocytes on the day of clinical engraftment and higher than that in normal. The peak of the NK cells reached to (37.8 +/- 17.52)% of lymphocyte at 30 days after clinical engraftment. NK count was (30.4 +/- 19.14)% at 60 days after clinical engraftment when the absolute NK cell count reached to the peak (up to 544 cells/microl) in PB. The activated receptor NKG2D was reconstituted fast and high expressed [(79.58 +/- 8.71)%] at the time of clinical engraftment with a tendency of gradual elevation, which reached to peak value (82.55 +/- 9.10)% at day 60. Another activated receptor NKp46 also reconstituted fast, and maintained at a high level even at 90 days after clinical engraftment. The expression of NKG2A was lower than that of the activated receptor of NK cells, which tendency lasted for at least 90 days after clinical engraftment. The reconstitution of T cells in PB after UCBT was relatively slow with lower expression rate. It is concluded that the reconstitution of NK cells in patients with acute leukemia is earlier following UCBT. The earlier recovery of activated receptor of NK cells, especially NKG2D, suggests that the activation of NK cells may play a role in graft versus leukemia (GVL) effect in the early period after UCBT.

Immunoediting of natural killer cells by human nasopharyngeal carcinoma cell line: altered expression of KIRs and NKG2D receptors leads to reduction of natural killer cell-mediated cytolysis / 南方医科大学学报

<p><b>OBJECTIVE</b>To analyze the changes of inhibitory killer cell immunoglobulin-like receptors (KIRs), NKG2D receptor and the cytotoxicity of natural killer (NK) cells induced by persistent exposure to CNE2 cells.</p><p><b>METHODS</b>The HLA-class I genotypes of CNE2 cells and KIR genotypes were determined by PCR with sequence-specific primers (PCR-SSP). The expressions of KIR2DL1, KIR2DL3, KIR3DL1, and NKG2D by the NK cells (freshly isolated NK cells, NK cells cocultured with 100 U/ml IL2 or with 100 U/ml IL2 and CNE2 cells as the control, IL2 and CNE2 groups, respectively) were analyzed by flow cytometry. Cytotoxicity of NK cells against CNE2 cells were detected by LDH releasing assay.</p><p><b>RESULTS</b>The HLA genotypes of CNE2 cells were A2, 24, B18, 35, Cw4, 7. NK cells isolated from 3 healthy donors expressed KIR2DL1, KIR2DL3, and KIR3DL1. After 4, 24 and 48 h of culture, NK cells in CNE2 group displayed higher KIR2DL1, KIR2DL3 but lower NKG2D expression than those in the control and IL2 groups (P<0.01), whereas the latter two groups showed no significant difference in KIR2DL1, KIR2DL3, and NKG2D expressions (P>0.05), and no difference in KIR3DL1 expression was found between the 3 groups (P>0.05). After 24 h of culture, the cytotoxicity against CNE2 cells mediated by the NK cells in IL2 and CNE2 groups were (26.96-/+1.47) % and (2.74-/+1.64) % at E:T ratios of 10:1, and (35.74-/+3.59)% and (4.57-/+2.41) % at E:T ratio of 20:1, respectively. NK cells in CNE2 group displayed lower cytotoxicity than those in IL2 group (P<0.01).</p><p><b>CONCLUSIONS</b>Persistent exposure to tumor cells expressing NKG2D ligands can lead to downregulated expression of NKG2D receptor, increased expression of KIRs and reduction of NK-mediated cytolysis. These results elucidate the molecular mechanism of reduced cytotoxicity mediated by the edited NK cells and indicate that blocking HLA-class I-bound KIRs or enhancing the expression of NKG2D may promote NK cell-mediated cytolysis.</p>

Effects of NKG2D and its ligands RAE-1 and H60 on graft-versus-tumor response / 中国实验血液学杂志

The study was purposed to explore the effects of NKG2D receptor and its ligands RAE-1 and H60 on graft-versus-tumor (GVT) response induced by MHC haploidentical bone marrow/spleen cell transplantation. Female (BALB/c x C57BL/6) F1 mice (CB6F1, H-2K(b/d)) inoculated with H22 cells to develop a solid tumor model were the recipients, and bone marrow mixed with spleen cells of the healthy male C57BL/6 (H-2K(b)) mice were the donor cells. GVT response was observed after transplantation that from donor cells T and NK cells were purged with anti-CD3 and anti-NK monoclonal antibody, and the NKG2D receptor was blocked with anti-NKG2D monoclonal antibody, the expression levels of RAE-1 and H60 mRNA in tumor tissue were measured by means of semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) at different time points after transplantation. The results showed that the GVT response of transplantation was reduced after in vitro depletion of T and NK cells or blocking NKG2D receptor in donor cells of the graft, the expression levels of RAE-1 and H60 mRNA in tumor tissue increased after transplantation of haploidential bone marrow mixed with spleen cells. It is concluded that NKG2D and its ligands RAE-1 and H60 may play important roles in GVT response.

Expression profile of nasal NK/T cell lymphoma by cDNA microarray / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To investigate the changes of gene expression profile in nasal NK/T cell lymphoma.</p><p><b>METHODS</b>Total RNA was extracted from the fresh nasal NK/T cell lymphoma tissue and normal lymph node. Fluorescent labeled cDNA was obtained through synthesizing process by reverse transcription. After hybridization in the two identical microarrays consisting of 4096 genes, overexpressed or underexpressed tumor related genes were analyzed.</p><p><b>RESULTS</b>In both experimental group and control group, there were six samples. A total of 365 (8.9%) genes was found to be differentially expressed by a factor of twofold or greater in both of two identical cDNA microarrays, which included oncogenes, tumor supressor genes, cell cycle regulators, apoptotic and antiapoptotic factors, DNA transcription factors, DNA repair and recombination factors, signal transduction genes, protein translation genes, as well as a large number of metabolic genes. Thirty-seven of these genes were found to be differentially expressed by a factor of fourfold or greater. The biochemical functions of these differentially expressed genes were diverse.</p><p><b>CONCLUSION</b>This study demonstrates that many different kinds of genes are possibly involved in the initiation and progression of nasal NK/T lymphoma. cDNA microarray technique is useful in screening cancer gene expression for nasal NK/T lymphoma.</p>

Selective Expansion of Natural Killer Cells from Peripheral Blood Mononuclear Cells by K562 Cell Line and IL-2

BACKGROUND: Several attempts have been made to expand human NK cells from peripheral blood mononuclear cells (PBMCs). This study examined the selective expansion of NK cells using interleukin 2 (IL-2) plus the K562 cell line, the expression of the NK cell receptors, and the cytotoxic activity. METHODS: The PBMCs from seven healthy volunteers were cultured in a medium containing the IL-2 plus the K562 cell line for 14 days. The expression of the activating and inhibitory receptors on the resting NK cells and the 72 hr-expanded NK cells were analyzed. A flow cytometric cytotoxic assay was used to determined the killing activity of the non-expanded NK cells and the 7 day-expanded NK cells against the K562 target cells. RESULTS: The NK cells from PBMCs expanded 4.5-fold after 7 days, and contained 56.5% CD3-CD56+ cells. The IL-2 or IL-2 plus K562 increased the expression levels of CD158b (MFI, mean florescence intensity), CD158e1/e2 (MFI), and NKp44 (MFI), while it decreased the expression levels of NKp30 (%), CD16 (MFI), and 2B4 (MFI). The non-expanded NK cells lysed 9.0% and 27.6% of the K562 target cells in the 1 : 1 and 5 : 1 effector and target ratio, respectively, and the 7-day expanded NK cells lysed 36.9% and 57.2% of the K562 target cells, respectively. CONCLUSION: The selective expansion of CD3-CD56+ NK cells occurred only during 7 days of culture. IL-2 or IL-2 plus the K562 cells altered the expression of various activating and inhibitory receptors of NK cells, and the cytotoxicity of the expanded NK cells was higher than in the non-expanded cells.

Effect of acetylcholine on the cytotoxicity of natural killer cells / 中国应用生理学杂志

<p><b>AIM</b>To investigate the effect of acetylcholine (ACh) on the cytotoxicity of natural killer (NK) cells and to explore the receptor mechanisms involved in the effect.</p><p><b>METHODS</b>The effector cells (i. e. NK cells) from the spleens of rats were collected and cultured with the target cells (Yac-1 cells). The various concentrations of ACh, cholinergic receptor agonists or antagonists were added to the cultures, respectively according to distinct experimental purposes. Lactate dehydrogenase (LDH) release assay was used to evaluate NK cell cytotoxicity.</p><p><b>RESULTS</b>NK-cell-mediated lysis of Yac-1 lymphoma cells was reduced by 10(-10) - 10(-6) mol/L ACh. The inhibitory effect of ACh on NK cell cytotoxicity was mimicked by pilocarpine, an agonist of muscarinic receptor, and by nicotine, an agonist of nicotinic receptor, at all applied concentrations (10(-10) - 10(-6) mol/L). Muscarinic receptor antagonist atropine blocked the inhibitory effect of ACh on the cytotoxicity of NK cells. Nevertheless, tubocurarine, an antagonist of nicotinic receptor, had no blocking effect on the suppression of NK cell cytotoxicity by ACh.</p><p><b>CONCLUSION</b>ACh results in an inhibition of the cytotoxicity of NK cells, and this inhibition is realized mainly through M and N1 cholinergic receptor.</p>

The negative regulatory effect of IFN-gamma on cognitive function of human natural killer cells / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To investigate the regulatory effect of IFN-gamma on recognition of target cells by human natural killer (NK) cells.</p><p><b>METHODS</b>The cytotoxic activity of human NK cell lines (NK92, NKL) was detected by MTT method. Expression of NK cell receptors (NKG2D, NKG2A/B, KIR2DL1 and KIR2DS1) and MICA on target cells (the ligand of NKG2D) was measured by RT-PCR.</p><p><b>RESULTS</b>Both NK92 and NKL cells exerted higher cytotoxicity to tumor cells with MICA expression, while tumors without MICA expression could resist NK cell lysis. IFN-gamma (> 1000 U/ml) inhibited NK lysis of tumor cells with MICA expression through down-regulating the expression of NKG2D, but up-regulating the expression of NKG2A/B and KIR2DL1.</p><p><b>CONCLUSION</b>IFN-gamma has a negative effect on activation and cytotoxicity of human NK cells by altering the balance between the expression of activating and inhibitory receptors on NK cells in favor of inhibition. This may serve to limit NK cell over-activation in vivo.</p>

NK cell receptors and related ligands / 中国医学科学院学报

NK cell has antigen-non-specific receptors on its surface. Based on the molecular structure, NK cell receptors can be divided into two types, including Ig superfamily and C-type lectin superfamily. Based on function, NK cell receptors can be divided into activation receptors (NKAR) and inhibition receptors (NKIR). NKAR includes CD16 mediating antibody dependent cytotoxicity, NKR-P1 mediating natural cytotoxicity, KAR conjugated with DAP12 and co-stimulatory receptor. They transduce signal through the ITAM motif in their cytoplasmic region. NKIR mainly include KIR and CD94/NKG2. Their ligands are MHC-I molecules. They are closely related to the recognition of auto cells by NK cells. Inhibition of NKAR activation and cytotoxic effect of NK cells by NKIR are carried out through the ITIM motif and require co-aggregation of NKAR and NKIR.

CD94/NKG2A--a kind of inhibitory receptor belonging to C-type lectin superfamily / 中国医学科学院学报

CD94/NKG2A is a kind of inhibitory receptor belonging to C-type lectin superfamily. It specifically expresses on the surface of some lymphocytes such as NK cells and T cells, and mediates inhibitory signal. In this mini-review, the structure of CD94/NKG2A molecule is described and its biological significance is discussed.