Thursday, April 22, 2021

IFN-γ Concentration, p53 and Immune Sensitivity


Dimorphic complexity between Human Leukocyte Antigen (HLA) and Killer Immune Receptor (KIR) haplotypes
introduce significant challenges for personalized Natural Killer (NK) and immune cell therapy. In vitro models support a p53 requirement for upregulation of NK ligands and there is a strong association between the KIR B haplotype and p53 alteration in Basal Cell Carcinoma's (BCC) with a higher likelihood that KIR B carriers harbor abnormal p53. Data suggests that KIR encoded by B genes provides selective pressure for altered p53 in, at least BCC's. 

Breast cancer (BC) patients exhibit reduced NK-cytotoxicity in peripheral blood. To test whether certain KIR-HLA combinations impair NK-cytotoxicity that predispose to BC risk, KIR and HLA polymorphisms were analyzed in 162 women with BC and 278 controls. KIR-B genotypes increased significantly in BC. Certain activating KIR (aKIR) HLA ligand combinations were significantly increased in advanced-BC patients whose combinations also shared specific inhibitory KIR (iKIR) counterparts. Contrarily, iKIR-HLA pairs without their aKIR-HLA counterparts were significantly higher in controls. The data suggests NK cells expressing iKIR to cognate HLA-ligands in the absence of specific aKIR counterpart are instrumental in antitumor response. 

The TP53 family consists of three sets of transcription factor genes, TP53, TP63 and TP73, each expresses multiple RNA variants and protein isoforms. TP53 is mutated in 25-30% of BC's, but the effect of isoforms in BC is unknown. Predicted changes in expression of a subset of RNAs involved in IFN-γ signaling were confirmed in vitro. Data showed that different members of the TP53 family can drive transcription of genes involved in IFN-γ signaling in different BC subgroups. Moreover, tumors with low IFN-γ signaling were associated with significantly poorer patient outcome.

NK receptor NKG2D interacts with several virus or stress inducible ligands, including ULBP1 (NKG2DL1) and -2 expressed on target cells. Induction of wild-type p53, but not mutant p53, strongly upregulated mRNA and surface expression of ULBP1 and -2, but not other ligands. An intronic p53-responsive element was discovered in these genes. Coculture of wild-type, p53-induced human tumor cells with primary human NK cells enhanced NKG2D dependent degranulation and IFN-γ production by NK cells.  

In the Tumor Micro Environment (TME) IFN-γ is produced at various concentrations in response to numerous immune stimulants and highlights the need for more personalized, disease centric approach. Engagement of IFN-γ Receptor on distinct tumor stromal cells, induction of interferon stimulated genes, immune status of the TME, and IFN-γ concentration are recognized as critical determinants for IFN-γ-mediated outcomes. Notably, an appropriate antitumor concentration of IFN-γ has yet to be determined. Interestingly IFN-γ produced by NK cells is said to be an essential mediator of Angiotensin II inflammation and vascular dysfunction.

Pharmacological activation of p53 exerts a potent antileukemia effect on antitumor immunity, including NK cell-mediated cytotoxicity against acute myeloid leukemia (AML). Interestingly, orally administered DS-5272 (a potent inhibitor of MDM2 - promotor of p53 degradation) induced upregulation of CD107a and IFN-γ in NK cells but not in CD8+ T cells. Furthermore, coculture of NK cells with leukemia cells resulted in massive apoptosis. 

Findings strongly suggest an interaction between B7 (NK receptor) molecules contribute to a particular design of the inflammatory microenvironment including B7-H6 and PD-L1, for which therapy was enhanced by expanded NK autologous or donor cells. RNA transfections, into HeLa cells of p53 or BRCA1 intron1 Key Sequences (based on Codondex iScore's most significant mRNA-intron1 variations) caused several genes to be upregulated, +1500% above control including B7-H6 (NCR3LG1) ligand for NCR3 (Nkp30) NK cell receptor which, when engaged triggers IFN-γ release. NCR3 and soluble isoforms of Leukocyte Specific Transcript 1 may play a role in inflammatory and infectious diseases. 

Blockade of B7-H3 prolonged the survival of SKOV3 ovarian cancer cell, an in ovarian tumor-bearing mice, miR-29c improved the anti-tumor efficacy of NK-cell by directly targeting B7-H3. miR-29c downregulates B7-H3 and inhibits NK-cell exhaustion. Low levels of mir-29c have been associated with mutated p53 in BC patients. miR-29 miRNAs activate p53 by targeting p85α and CDC42 and upregulate p53 levels that induce apoptosis in a p53-dependent manner. miR-29 controls innate and adaptive immune responses to intracellular bacterial infection by targeting IFN-γ

Besides (intron predominant) human ALU repeats, reverse complementary sequences between introns bracketing circRNAs are highly enriched in RNA editing or hyper-editing events. Knockdown of double stranded RNA-editing enzyme - ADAR1 significantly and specifically upregulated circRNA expression. In its absence (interferon stimulating) oligoadenylate synthetase (OAS) can be activated by self-dsRNA (in contrast to viral dsRNA), resulting in RNase L activity and cell death. Conversely, OASL1 expression enhanced RIG-I-mediated IFN induction. In cells absent of p53, immunogenic, endogenous mitochondrial dsRNA are produced and processed by the OAS/RNase L system presenting a novel mechanism in diseases with aberrant immune responses. IFN-γ restores the impaired function of RNase L and induces mitochondria-mediated apoptosis in lung cancer. The p53—OAS axis, in mitochondrial RNA processing may prevent self-nucleic acid such as dsRNA from aberrantly activating innate immune responses.

A plethora of evidence supports bottom up approach to personalized therapy. A p53 intron1-mRNA regulatory loop, as a potential mechanism in IFN responses to infection and disease may be diagnostic. Pre-clinical research, presently underway will establish whether p53 is diagnostic for specific selections of a biopsy to educate NK cells and trigger effective immune response.

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