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Natural killer cells (NK) are the "professional killer" of tumors and play a crucial role in anti-tumor immunotherapy. NK cell desensitization is a key mechanism of tumor immune escape. Dysregulated NKG2D-NKG2DL signaling is a primary driver of this desensitization process. However, the factors that regulate NK cell desensitization remain largely uncharacterized. Here, we present the first report that circular RNA circARAP2 (hsa_circ_0069396) is involved in the soluble MICA (sMICA)-induced NKG2D endocytosis in the NK cell desensitization model. CircARAP2 was upregulated during NK cell desensitization and the loss of circARAP2 alleviated NKG2D endocytosis and NK cell desensitization. Using Chromatin isolation by RNA purification (ChIRP) and RNA pull-down approaches, we identified that RAB5A, a molecular marker of early endosomes, was its downstream target. Notably, transcription factor CTCF was an intermediate functional partner of circARAP2. Mechanistically, we discovered that circARAP2 interacted with CTCF and inhibited the recruitment of CTCF-Polycomb Repressive Complex 2 (PRC2) to the promoter region of RAB5A, thereby erasing histone H3K27 and H3K9 methylation suppression to enhance RAB5A transcription. These data demonstrate that inhibition of circARAP2 effectively alleviates sMICA-induced NKG2D endocytosis and NK cell desensitization, providing a novel target for therapeutic intervention in tumor immune evasion. [ABSTRACT FROM AUTHOR]

The COVID-19 global pandemic and high mortality rates necessitate the development of diagnostic and prognostic tools, as well as expanding testing capacity. Existing methods for detecting and characterizing SARS-CoV-2 infection are typically based on viral genome detection or measuring COVID-19-specific antibody levels. Despite their value, these methods are unable to predict disease outcomes in patients. Given the critical role of innate immune cells, particularly natural killer (NK) cells, in antiviral defense, this study sought to determine the prognostic value of serum secretory MHC class I polypeptide–related sequence A (sMICA) levels as an essential ligand for the NKG2D receptor, the master regulator of NK cell development and responsiveness. Serum MICA levels were measured by ELISA assay. Sera (n = 60) from SARS-CoV-2 positive patients were collected, and disease severity was determined using clinical criteria. The patient group included 30 patients with mild disease and 30 severely ill patients, as well as 30 healthy controls. Our findings revealed that serum MICA levels were significantly higher in patients than in controls, especially in cases with severe complications (P <.0001). Higher serum MICA levels may be associated with respiratory failure in COVID-19 and may serve as a marker of clinical severity in patients infected with SARS-CoV-2, particularly when clinical manifestations are insufficient to make a confident prediction. Higher MICA levels may be associated with respiratory failure in COVID-19 infection. SMICA levels change with age, particularly for patients with severe COVID-19 disease. NKG2D ligands may have prognostic and therapeutic value for COVID-19 patients. [ABSTRACT FROM AUTHOR]

Background and Aim: Major histocompatibility complex class I chain‐related A (MICA) genetic variants and their serum levels (sMICA) were associated with the development of hepatitis C virus‐related hepatocellular carcinoma (HCC) in untreated cohorts. The dynamic changes in serial sMICA levels and their association with HCC in the post‐curative status are elusive. Methods: Single nucleotide polymorphism rs2596542 of MICA and serial sMICA levels were analyzed in chronic hepatitis C patients with a sustained virologic response after antivirals. Forty‐two patients who developed HCC and 84 age‐matched, gender‐matched, and cirrhosis propensity score‐matched non‐HCC controls were compared. Serial sMICA levels were measured within 6 months before treatment initiation (pre‐sMICA), 6 months after the end of treatment (post‐sMICA), and on the last visit before the development (or not) of HCC (last‐sMICA). Results: Cox regression analysis revealed that last‐sMICA was the only predictive factor of HCC development (hazard ratio/95% confidence interval: 2.27 (per 1 log pg/mL increase)/1.672–3.082, P < 0.001). Patients without HCC development showed a significantly reduced trend of sMICA levels during follow‐up (trend P = 0.001), which was observed only in GG genotype (trend P < 0.001) but not A allele carriers (P = 0.88). In contrast, patients with HCC showed an increased trend of sMICA levels (trend P = 0.024). However, only the GG genotype "high expressors" (trend P = 0.06) but not A allele carriers (P = 0.18) showed a correlation of substantially increased trend of sMICA levels and HCC development. Conclusions: Serial sMICA levels were associated with HCC development in SVR patients. The clinical utility of this finding is restricted to MICA rs2596542 GG genotype carriers. [ABSTRACT FROM AUTHOR]

Highlights • MICA-129 val/val genotype may influence sMICA expression. • The deficiency in heterozygotes found may be due LD of MICA and HLA alleles. • There was no difference between MICA- 129 Met/Val genotypes between samples. Abstract The aim of this case- control study was to investigate the association between preterm birth (PTB), MICA- 129 A/G dimorphism and sMICA levels. Fifty pregnant women with singleton pregnancy and previous PTB, or clinic diagnostic of threatened preterm labor in the actual pregnancy, or cervical length less than 25 mm and 50 healthy pregnant women were enrolled. DNA was extracted for genotyping for MICA -129 A/G by real-time PCR and sMICA plasma level was quantified by sandwich ELISA assay. Clinical and socioeconomic characteristics, results of TaqMan® genotyping and ELISA quantification were compared between the groups using qui-square, Fisher´s exact or Mann-Whitney test. A binary logistic regression model was used to predict PTB. The correlation between MICA -129 A/G genotypes and sMICA levels was investigated. There were not statistically significant differences between MICA -129 A/G polymorphism and sMICA plasma level.There was found a correlation between MICA -129 val/val genotype and higher levels of sMICA (ρ: -0.342; p:0.001). The presence of MICA -129 val/val genotype may be influencing sMICA expression. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Rheumatoid arthritis (RA) is a clinically heterogeneous chronic inflammatory disorder characterized by synovitis leading to joint destruction. Both genetic and environmental factors are involved in the pathogenesis of RA. Significant dysregulation of NKG2D, an activating receptor of natural killer and certain autoreactive T cells as well as its ligand major histocompatibility complex class I chain–related gene A (MICA) has been implicated in perpetuating the pathology of RA. Since the genetic polymorphism in MICA gene (MICA‐129 met/val polymorphism at codon 129) is known to affect its binding affinity to NKG2D, we explored its influence on RA susceptibility and disease severity. Methods: The MICA‐129 met/val polymorphism was examined in 270 patients with RA and 232 healthy controls by TaqMan 5′‐nuclease assay. Serum soluble MICA (sMICA) was measured in a subset of 89 patients and 80 controls by enzyme‐linked immunosorbent assay. Results: We observed that the frequency of MICA‐129 val allele (73% vs. 65%, Pc = 0.006, odds ratio = 1.48, 95% CI = 1.12–1.95) was higher in patients than in controls. sMICA levels were significantly higher in patients with RA than in controls (P < 0.0001). sMICA levels were higher in patients with val/val genotype than in those with met/val or met/met genotype (P = 0.03). The MICA‐129 val/val genotype was associated with high titers of sMICA in patients with deforming RA phenotype (P = 0.02), suggesting a role in determination of severity of RA. Conclusion: MICA‐129 val/val genotype, associated with higher levels of circulating sMICA, may influence disease susceptibility and associate with increased severity of RA in south Indian Tamils. [ABSTRACT FROM AUTHOR]

Metastatic melanoma is a rapidly spreading cancer whose prognosis remains poor although important therapy advances in recent years. Ipilimumab, an anti-CTLA-4 immunotherapy used in advanced melanoma, is an effective immunotherapy alone or combined with other agents but with few predictive biomarkers of response. Here, we sought to analyze the potential of S100B, MIA, soluble MICA, anti-MICA antibodies and LDH as serum biomarkers of response and survival in a cohort of 77 advanced melanoma patients subjected to ipilimumab. Lower levels of S100B, and LDH at baseline and at weeks 3 and 6 correlated to a better response and survival. After multivariate analysis LDH maintained its independence at baseline and week 6, whereas S100B might be a useful tool for anti-CTLA-4 treatment monitoring after the first two doses of ipilimumab (W6). In addition, higher sMICA serum levels at baseline were associated with less frequency of irAEs. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the expression levels of NF-κB, MMP-9, and MICA and their relationship between each other in pituitary adenomas as a histological basis for the study of the expression and shedding mechanism of MICA and mechanism of immune escape of pituitary adenomas. Our study indicated that MICA, MMP-9 and NF-κB mRNA and protein levels were more highly expressed in pituitary adenomas than healthy tissues. The expression levels of NF-κB, MMP-9, and MICA were positively related in patients with pituitary adenomas. In conclusion, the activation of NF-κB can up-regulate the expression of MICA and induce the expression of MMP-9, which hydrolyzes MICA into sMICA to promote tumor immune escape. The interactions of NF-κB, MMP-9, and MICA play an important role in the development of pituitary adenomas, and MMP-9 could be used as a new target for inhibiting tumor cell immune escape. [ABSTRACT FROM AUTHOR]

Ataxia-telangiectasia (A-T) is a multisystem disorder caused by biallelic pathogenic variants in the gene encoding A-T mutated (ATM) kinase, a master regulator of the DNA damage response (DDR) pathway. Most A-T patients show cellular and/or humoral immunodeficiency that has been associated with cancer risk and reduced survival, but NK cells have not been thoroughly studied. Here we investigated NK cells of A-T patients with a special focus on the NKG2D receptor that triggers cytotoxicity upon engagement by its ligands (NKG2DLs) commonly induced via the DDR pathway on infected, transformed, and variously stressed cells. Using flow cytometry, we examined the phenotype and function of NK cells in 6 A-T patients as compared with healthy individuals. NKG2D expression was evaluated also by western blotting and RT-qPCR; plasma soluble NKG2DLs (sMICA, sMICB, sULBP1, ULBP2) were measured by ELISA. Results showed that A-T NK cells were skewed towards the CD56neg anergic phenotype and displayed decreased expression of NKG2D and perforin. NKG2D was reduced at the protein but not at the mRNA level and resulted in impaired NKG2D-mediated cytotoxicity in 4/6 A-T patients. Moreover, in A-T plasma we found 24-fold and 2-fold increase of sMICA and sULBP1, respectively, both inversely correlated with NKG2D expression. Overall, NK cells are disturbed in A-T patients showing reduced NKG2D expression, possibly caused by persistent engagement of its ligands, that may contribute to susceptibility to cancer and infections and represent novel targets for therapeutic interventions. • The CD56neg NK-cell subset was expanded in A-T patients. • NK cells of A-T patients showed reduced NKG2D and perforin expression. • NKG2D down-regulation in A-T NK cells occurred post-transcriptionally. • Increased sMICA and sULBP1 levels in A-T plasma were inversely correlated with NKG2D+ NK cells. • NKG2D-mediated NK cell activation was impaired in 4/6 A-T patients. [ABSTRACT FROM AUTHOR]

The polymorphic major histocompatibility complex class I chain-related molecule A (MICA) and its soluble form (sMICA) interact with activating receptor natural-killer group 2 member D (NKG2D) on natural-killer (NK) and T cells, thereby modifying immune responses to transplantation and infectious agents (e.g., cytomegalovirus). Two single-nucleotide polymorphisms (SNPs), rs2596538GA in the MICA promoter and rs1051792AG in the coding region (MICA-129Val/Met), influence MICA expression or binding to NKG2D, with MICA-129Met molecules showing higher receptor affinity. To investigate the impact of these SNPs on the occurrence of cytomegalovirus infection or acute rejection (AR) in individuals who underwent simultaneous pancreas–kidney transplantation (SPKT), 50 recipient-donor pairs were genotyped, and sMICA levels were measured during the first year post-transplantation. Recipients with a Val-mismatch (recipient Met/Met and donor Val/Met or Val/Val) showed shorter cytomegalovirus infection-free and shorter kidney AR-free survival. Additionally, Val mismatch was an independent predictor of cytomegalovirus infection and kidney AR in the first year post-transplantation. Interestingly, sMICA levels were lower in rs2596538AA and MICA129Met/Met-homozygous recipients. These results provide further evidence that genetic variants of MICA influence sMICA levels, and that Val mismatch at position 129 increases cytomegalovirus infection and kidney AR risk during the first year post-SPKT. [ABSTRACT FROM AUTHOR]

Dysfunction of natural killer (NK) cells has been implicated in the failure of antitumor immune responses in hepatocellular carcinoma (HCC) patients. However, the changes of NK profile in peripheral blood after surgery and tumor tissues of HCC patients, as well as the underlying reason and the significance are vague. Here, we observed that the frequencies of circulating NKG2D+CD56dimNK cells decreased significantly in HBV-related HCC and were negatively correlated with the levels of serum TGF-β and soluble MICA (sMICA).In vitroexperiments confirmed that the TGF-β and sMICA in tumor tissue homogenates, as well as sMICA in HCC cells culture supernatants could reduce the frequency of NKG2D+CD56dimNK cells. In addition, in HCC patients the lower frequency of circulating NKG2D+CD56dimNK cells was associated with larger tumor size and/or higher serum GGT. Noticeably, the frequency of NKG2D+CD56dimNK cells at one month after surgery usually failed to restore in early recurrent patients, and that frequency was negatively associated with early recurrence and shorter overall survival. These results suggest that declined frequency of NKG2D+CD56dimNK cells in HCC was associated with higher TGF-β and sMICA production, and low frequency of circulating NKG2D+CD56dimNK cells at one month after surgery may predict poor prognosis of HBV-related HCC patients accepting hepatectomy. [ABSTRACT FROM PUBLISHER]