The effects of KIR2DL4 stimulated NK-92 cells on the apoptotic pathways of HER2 + /HER-breast cancer cells

Natural killer (NK) cells are immune cells that have attracted significant attention due to their cytotoxic properties. They are believed to be highly effective in cancer therapy. In this study, anti-KIR2DL4 (Killer cell Immunoglobulin like Receptor, 2 Ig Domains and Long cytoplasmic tail 4) was used to stimulate the NK-92 activator receptor to increase their cytotoxicity on breast cancer cell lines. Unstimulated and stimulated NK-92 cells (sNK-92) were cocultured with breast cancer (MCF-7 and SK-BR-3) and normal breast (MCF-12A) cell lines at 1:1, 1:5, and 1:10 (Target:Effector) ratios. The most effective cell cytotoxicity ratio (1:10) was used in the immunostaining and western blot assays to evaluate apoptosis pathway proteins. The sNK-92 cells showed higher cytotoxic activity on breast cancer cells than NK-92 cells. sNK-92 cells had a selective significant cytotoxicity effect on MCF-7 and SK-BR-3 cells but not MCF-12A cells. While sNK-92 cells were effective at all cell concentrations, they were most effective at a 1:10 ratio. Immunostaining and western blots showed significantly higher BAX, caspase 3, and caspase 9 protein levels in all breast cancer cell groups cocultured with sNK-92 than with NK-92 cells. NK-92 cells stimulated with KIR2DL4 showed elevated cytotoxic activity. The cytotoxic activity of sNK-92 cells on breast cancer cells is via apoptosis pathways. However, their effect on normal breast cells is limited. While the obtained data contains only basic information, additional clinical studies are needed to provide a basis for a new treatment model.

Clinical significance and immune landscape of KIR2DL4 and the senescence-based signature in cutaneous melanoma

Senescence is an effective barrier to tumor progression. Mutations that inhibit senescence and promote cell division are mandatory for the development of cancer. Therefore, it is particularly important to explore the differences between cutaneous melanoma (CM) patients with severe and mild degrees of senescence. We clustered all the patients with CM in the Cancer Genome Atlas (TCGA) database based on all the genes of the senescence pathway in the cellAge and MSigDB database. The prognosis, immunotherapy effect, tumor microenvironment score, NRAS mutation rate, expression of CD274, CTLA4, and PDCD1, and abundance of CD8+ T and NK cell infiltration in the younger group of patients (YG) were higher than those in the older group (OG). Compared with the American Joint Committee on Cancer (AJCC) stage, the risk scoring system stratified the risk of CM patients and guided immunotherapy more accurately. The nomogram model, which combined the AJCC stage and risk score, greatly improved the ability and accuracy of prognosis prediction. As KIR2DL4 is the core molecule in the risk scoring system (RSS), knocking down the KIR2DL4 of human NK cells in vitro can inhibit the cytotoxicity of NK cells and can also inhibit the secretion of tumor necrosis factor-α and interferon-γ by NK cells. In contrast, upregulation of KIR2DL4 can activate the MEK/ERK signaling pathway, which is the activation pathway of NK cells. OurRSS and nomogram model can accurately stratify the risk of CM patients and effectively predict the effect of immunotherapy and prognosis in CM patients.

Roles of HLA-G/KIR2DL4 in Breast Cancer Immune Microenvironment

Human leukocyte antigen (HLA)-G is a nonclassical MHC Class I molecule, which was initially reported as a mediator of immune tolerance when expressed in extravillous trophoblast cells at the maternal-fetal interface. HLA-G is the only known ligand of killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), an atypical family molecule that is widely expressed on the surface of NK cells. Unlike other KIR receptors, KIR2DL4 contains both an arginine–tyrosine activation motif in its transmembrane region and an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytoplasmic tail, suggesting that KIR2DL4 may function as an activating or inhibitory receptor. The immunosuppressive microenvironment exemplified by a rewired cytokine network and upregulated immune checkpoint proteins is a hallmark of advanced and therapy-refractory tumors. Accumulating evidence has shown that HLA-G is an immune checkpoint molecule with specific relevance in cancer immune escape, although the role of HLA-G/KIR2DL4 in antitumor immunity is still uncharacterized. Our previous study had shown that HLA-G was a pivotal mediator of breast cancer resistance to trastuzumab, and blockade of the HLA-G/KIR2DL4 interaction can resensitize breast cancer to trastuzumab treatment. In this review, we aim to summarize and discuss the role of HLA-G/KIR2DL4 in the immune microenvironment of breast cancer. A better understanding of HLA-G is beneficial to identifying novel biomarker(s) for breast cancer, which is important for precision diagnosis and prognostic assessment. In addition, it is also necessary to unravel the mechanisms underlying HLA-G/KIR2DL4 regulation of the immune microenvironment in breast cancer, hopefully providing a rationale for combined HLA-G and immune checkpoints targeting for the effective treatment of breast cancer.

KIR2DL4 genetic diversity in a Brazilian population sample: implications for transcription regulation and protein diversity in samples with different ancestry backgrounds

KIR2DL4 is an important immune modulator expressed in natural killer cells; HLA-G is its main ligand. We have characterized the KIR2DL4 genetic diversity by considering the promoter, all exons, and all introns in a highly admixed Brazilian population sample and by using massively parallel sequencing. We introduce a molecular method to amplify and to sequence the complete KIR2DL4 gene. To avoid the mapping bias and genotype errors commonly observed in gene families, we have developed and validated a bioinformatic pipeline designed to minimize these errors and applied it to survey the variability of 220 individuals from the State of São Paulo, southeastern Brazil. We have also compared the KIR2DL4 genetic diversity in the Brazilian cohort with the diversity previously reported by the 1000Genomes consortium. KIR2DL4 presents high linkage disequilibrium throughout the gene, with coding sequences associated with specific promoters. There are few but divergent promoter haplotypes. We have also detected many new KIR2DL4 sequences, all bearing nucleotide exchanges in introns and encoding previously described proteins. Exons 3 and 4, which encode the external domains, are the most variable. The ancestry background influences the KIR2DL4 allele frequencies and must be considered for association studies regarding KIR2DL4.

Killer Immunoglobulin-Like Receptor 2DL4 (CD158d) Regulates Human Mast Cells both Positively and Negatively: Possible Roles in Pregnancy and Cancer Metastasis

Killer immunoglobulin-like receptor (KIR) 2DL4 (CD158d) was previously thought to be a human NK cell-specific protein. Mast cells are involved in allergic reactions via their KIT-mediated and FcɛRI-mediated responses. We recently detected the expression of KIR2DL4 in human cultured mast cells established from peripheral blood of healthy volunteers (PB-mast), in the human mast cell line LAD2, and in human tissue mast cells. Agonistic antibodies against KIR2DL4 negatively regulate the KIT-mediated and FcɛRI-mediated responses of PB-mast and LAD2 cells. In addition, agonistic antibodies and human leukocyte antigen (HLA)-G, a natural ligand for KIR2DL4, induce the secretion of leukemia inhibitory factor and serine proteases from human mast cells, which have been implicated in pregnancy establishment and cancer metastasis. Therefore, KIR2DL4 stimulation with agonistic antibodies and recombinant HLA-G protein may enhance both processes, in addition to suppressing mast-cell-mediated allergic reactions.

[The Role of Soluble HLA-G in the Vertical Transmission of Toxoplasma gondii]

Soluble human leukocyte antigen G (sHLA-G) plays a key role in pregnancy through interaction with decidual natural killer (dNK) cell inhibitory receptors at the maternal-fetal interface. To demonstrate the possible role of sHLA-G during the pregnancy with Toxoplasma gondii infection, we compared the concentration of a murine functional homolog of sHLA-G, Qa-2, in T. gondii infected and non-infected pregnant C57BL/6 mice, and that of sHLA-G in BeWo culture supernatant. In addition, the levels of KIR2DL4 expressed on human dNK cells and NKG2A in pregnant mice were evaluated. We showed that T. gondii infection result in significant increase in the level of Qa-2 and NKG2A in pregnant mice. sHLA-G and KIR2DL4 in human samples were also significantly upregulated under the condition of T. gondii infection. The further treatment with sHLA-G antibody could reduce the expression level of KIR2DL4 which was upregulated by T. gondii infection. In summary, sHLA-G could upregulate the expression level of KIR2DL4 which lead to excessive immunological tolerance, and further contributed to T. gondii immunity escaping and affecting fetus via vertical transmission which may lead to adverse outcomes.

Killer cell immunoglobulin-like receptor 2DL4 is expressed in and suppresses the cell growth of Langerhans cell histiocytosis

Killer cell immunoglobulin-like receptor (KIR) 2DL4 (CD158d) is a receptor for human leukocyte antigen-G. The function of KIR2DL4 has been reported in human natural killer cell lymphoma and mastocytosis, but not in Langerhans cell histiocytosis (LCH). Herein, we examined the expression and function of KIR2DL4 in LCHs. In pathological specimens, 27 of 36 LCH cases (75.0%) were immunohistochemically positive for KIR2DL4. Its expression was independent of age, gender, location, multi- or single-system, and the status of BRAFV600E immunostaining. We also confirmed the expression of KIR2DL4 mRNA and protein in the human LCH-like cell lines ELD-1 and PRU-1. KIR2DL4 protein was distributed in the membrane and cytoplasm of ELD-1 cells, but only in the cytoplasm of PRU-1 cells. An agonistic antibody against KIR2DL4 reduced phosphorylation of extracellular signal-regulated kinases (ERKs) and suppressed the cell growth of ELD-1 cells in a Src homology region 2 domain-containing phosphatase-2 dependent manner, but it had no effect in PRU-1 cells. These results suggest that KIR2DL4-mediated ERK suppression is a possible therapeutic target for LCH cells.

The impact of HLA-G, LILRB1 and LILRB2 gene polymorphisms on susceptibility to and severity of endometriosis

Endometriosis is a disease in which endometriotic tissue occurs outside the uterus. Its pathogenesis is still unknown. The most widespread hypothesis claims that ectopic endometrium appears as a result of retrograde menstruation and its insufficient elimination by immunocytes. Some reports have shown expression of non-classical HLA-G molecules on ectopic endometrium. HLA-G is recognized by KIR2DL4, LILRB1 and LILRB2 receptors on natural killer (NK) and other cells. These receptors are polymorphic, which may affect their activity. In this study we investigated whether HLA-G, KIR2DL4, LILRB1 and LILRB2 polymorphisms may influence susceptibility to endometriosis and disease progression. We used polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (PCR-RFLP) and allelic discrimination methods with TaqMan SNP Genotyping Assays for typing of 276 patients with endometriosis and 314 healthy fertile women. The HLA-G rs1632947:GG genotype was associated with protection against the disease and its severe stages; HLA-G rs1233334:CT protected against progression; LILRB1 rs41308748:AA and LILRB2 rs383369:AG predisposed to the disease and its progression. No effect of KIR2DL4 polymorphism was observed. These results support the role of polymorphisms of HLA-G and its receptors LILRB1 and LILRB2 in susceptibility to endometriosis and its progression.

Soluble monomers, dimers and HLA-G-expressing extracellular vesicles: the three dimensions of structural complexity to use HLA-G as a clinical biomarker

The HLA-G molecule belongs to the family of nonclassical human leukocyte antigen (HLA) class I. At variance to classical HLA class I, HLA-G displays (i) a low number of nucleotide variations within the coding region, (ii) a high structural diversity, (iii) a restricted peptide repertoire, (iv) a limited tissue distribution and (v) strong immune-suppressive properties. The physiological HLA-G surface expression is restricted to the maternal-fetal interface and to immune-privileged adult tissues. Soluble forms of HLA-G (sHLA-G) are detectable in various body fluids. Cellular activation and pathological processes are associated with an aberrant or a neo-expression of HLA-G/sHLA-G. Functionally, HLA-G and its secreted forms are considered to be key players in the induction of short- and long-term tolerance. Thus, its unique expression profile and tolerance-inducing functions render HLA-G/sHLA-G an attractive biomarker to monitor the systemic health/disease status and disease activity/progression for clinical approaches in disease management and treatments. Here, we place emphasis on (i) the current status of the tolerance-inducing functions by HLA-G/sHLA-G, (ii) the current complexity to implement this molecule as a meaningful clinical biomarker regarding the three dimensions of structural diversity (monomers, dimers and HLA-G-expressing extracellular vesicles) with its functional implications, and (iii) novel and future approaches to detect and quantify sHLA-G structures and functions.

The Potential of HLA-G-Bearing Extracellular Vesicles as a Future Element in HLA-G Immune Biology

The HLA-G molecule is a member of the non-classical HLA class I family. Its surface expression is physiologically restricted to the maternal–fetal interface and to immune privileged adult tissues. Despite the restricted tissue expression, HLA-G is detectable in body fluids as secreted soluble molecules. A unique feature of HLA-G is the structural diversity as surface expressed and as secreted molecules. Secreted HLA-G can be found in various body fluids either as free soluble HLA-G or as part of extracellular vesicles (EVs), which are composed of various antigens/ligands/receptors, bioactive lipids, cytokines, growth factors, and genetic information, such as mRNA and microRNA. Functionally, HLA-G and its secreted forms are considered to play a crucial role in the network of immune-regulatory tolerance mechanisms, preferentially interacting with the cognate inhibitory receptors LILRB1 and LILRB2. The HLA-G mediated tolerance is described in processes of pregnancy, inflammation, and cancer. However, almost all functional and clinical implications of HLA-G in vivo and in vitro have been established based on simple single ligand/receptor interactions at the cell surface, whereas HLA-G-bearing EVs were in minor research focus. Indeed, cytotrophoblast cells, mesenchymal stem cells, and cancer cells were recently described to secrete HLA-G-bearing EVs, displaying immunosuppressive effects and modulating the tumor microenvironment. However, numerous functional and clinical open questions persist. Here, we (i) introduce basic aspects of EVs biology, (ii) summarize the functional knowledge, clinical implications and open questions of HLA-G-bearing EVs, and (iii) discuss HLA-G-bearing EVs as a future element in HLA-G biology.

Possible Role of HLA-G, LILRB1 and KIR2DL4 Gene Polymorphisms in Spontaneous Miscarriage

The KIR2DL4 receptor and its ligand HLA-G are considered important for fetal-maternal immune tolerance and successful pregnancy. The absence of a particular variant of KIR2DL4 might be a bad prognostic factor for pregnancy outcome. However, it could be compensated by the presence of the respective LILRB1 allele. Therefore, we investigated the KIR2DL4, LILRB1 and HLA-G polymorphisms in 277 couples with spontaneous abortion and 219 control couples by HRM, PCR-SSP and RFLP methods. We found a protective effect of women’s heterozygosity in −716 HLA-G (p = 0.0206) and LILRB1 (p = 0.0131) against spontaneous abortion. Surprisingly, we observed more 9A/10A genotypes of KIR2DL4 gene carriers in the group of male partners from the miscarriage group in comparison to the men from the control group (p = 0.0288). Furthermore, there was no association of women’s KIR2DL4 polymorphism with susceptibility to spontaneous abortion. Multivariate analysis indicated that women’s −716 HLA-G and LILRB1 and men’s KIR2DL4 9A/10A are important in terms of the protection or susceptibility to miscarriage, respectively (p = 0.00968). In conclusion, a woman’s heterozygosity in HLA-G and LILRB1 might be an advantage for a success of reproduction, but the partner’s heterozygosity in 9A/10A KIR2DL4 alleles might not.

KIR2DL4 expression rather than its single nucleotide polymorphisms correlates with pre-eclampsia

OBJECTIVE

To evaluate the single nucleotide polymorphisms and expression of KIR2DL4 (killer cell immunoglobulin-like receptors) gene in pre-eclampsia patients.

METHODS

KIR2DL4 gene polymorphisms were detected in 100 patients with pre-eclampsia and 100 healthy pregnant women, respectively, by using PCR-SS. Then, the expression of KIR2DL4 was measured in 5 cases of placentas tissues with pre-eclampsia and normal pregnancies by using qRT-PCR.

RESULTS

Compared with healthy controls, 16 loci of single nucleotide polymorphisms (SNP) were identified in pre-eclampsia patients, including 7 new polymorphisms loci. But, no significant difference was found in genotype distributions and allele frequencies in pre-eclampsia and controls (P>0.05). However, qRT-PCR results showed that KIR2DL4 mRNA in placenta tissues with pre-eclampsia was significantly lower than those with normal pregnancy, and the difference was statistically significant.

CONCLUSION

Decreased level of KIR2DL4 rather than its SNP is correlated with the susceptibility of pre-eclampsia.

Genetic polymorphisms and expression of HLA-G and its receptors, KIR2DL4 and LILRB1, in non-small cell lung cancer

Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I molecule absent from most normal tissues but detected in many malignant tumors. It is recognized by cells of the immune system using LILRB1, KIR2DL4 and LILRB2 receptors. We attempted to find out whether some polymorphisms of HLA-G, LILRB1 and KIR2DL4 genes are associated with susceptibility to nonsmall cell lung cancer (NSCLC). Four polymorphisms in HLA-G, i.e. -964A>G (rs1632947), -725C>G>T (rs1233334), -716T>G (rs2249863) in the promoter, and a 14 base pair insertion/deletion (14 bp indel) in the 3'-untranslated region (3'UTR), and five in LILRB1 - 5651G>A (rs41308748) in intron 14, 5717C>T L622L (rs1061684), 5724G>A E625K (rs16985478), 5774 C>A P641P (rs41548213) in exon 15, and 5806C>T (rs8101240) in 3'UTR - as well as 9620 9A/10A (rs11410751) polymorphism in exon 7 of KIR2DL4 were typed using different laboratory techniques. Only one single nucleotide polymorphism (SNP) in HLA-G (-964A>G) and one in LILRB1 (5724G>A) were found to influence the risk of NSCLC. In addition, 5724G>A was associated with protection from tumor cell infiltration of regional lymph nodes. Most importantly, we detected HLA-G and LILRB1 expression in tumor specimens, but no correlation with genetic polymorphisms was observed. HLA-G and LILRB1 protein expression levels in tumor tissue were significantly correlated with tumor stage.

Adaptive evolution at immune system genes and deep pregnancy implantation in primates

A major evolutionary change in the lineage ancestral to humans, chimpanzee and gorilla (HCG) has been the embedding of the embryo into maternal tissue. Thus, the first layer of cells (trophoblast) to differentiate after fertilization must adapt to invade the uterus. Such event would likely leave signatures of positive selection at genes with roles in embryo implantation. Here, 163 pregnancy implantation genes are tested for evidence of adaptive diversification in the ancestral lineage to HCG. Two immune system genes, HLA-E and KIR2DL4 showed evidence of positive selection. Some of the positive selected sites involve amino acid substitution with predicted damaging effects on protein function, thus highlighting the possibility of antagonistic pleiotropic effects. Selection at a gene coding for a receptor expressed in uterine cells (KIR) that interacts with trophoblast human leukocyte antigen (HLA) genes suggests a main role for immunological adaptations in embryo deep invasion of the maternal endometrium.

Genetic polymorphism of KIR2DL4 (CD158d), a putative NK cell receptor for HLA-G, does not influence susceptibility to asthma

Human leukocyte antigen (HLA)-G is upregulated on the bronchial epithelium of asthma patients and genetic polymorphism affecting expression of HLA-G has been reported to influence susceptibility to asthma. As the NK cell receptor KIR2DL4 has been reported to induce interferon gamma (IFNγ) secretion when ligated with HLA-G, we postulated that the 9A/10A genetic polymorphism of KIR2DL4 which influences receptor structure may influence susceptibility to asthma. KIR2DL4 genotypes were determined in two cohorts of children (n = 219 and n = 1356) in whom total serum IgE, allergen-specific IgE, atopy, bronchial reactivity and asthma symptoms had been studied between birth and 14 years. No reproducible associations with KIR2DL4 genotype were identified, leading us to conclude that the KIR2DL4 9A/10A polymorphism has no influence on susceptibility to asthma.