Thursday, October 20, 2022

Toward Customized Natural Killer Cells

An important role of Natural Killer (NK) cells is to eliminate other cells that extinguish or diminish expression of self-MHC class I molecules or Human Leukocyte Antigen (HLA), which commonly occurs as a result of viral infection or cellular transformation. This capacity arises because NK cells express stimulatory and inhibitory receptors that engage ligands on normal cells. The majority of inhibitory receptors belong to the Killer-cell immunoglobulin-like receptors (KIR) and CD94/NKG2A  families and are specific for MHC I molecules. When an NK cell encounters a normal cell, engagement of the inhibitory receptors conveys signals that counteract stimulatory signaling. Lysis occurs when inhibition is lost because the target cell lacks one or more self-MHC molecules or when target cells express high levels of stimulatory ligands that counter inhibition.

Mitochondrial DNA (MtDNA) embedded in the genomes of 66,000 humans was associated with adverse consequences including cancer. Overall tumor specific nuclear embedded MtDNA was more common on Chromosome (Chr)19, less common on Chr6 and tended to involve non-coding, repetitive elements or satellite repeats. 

The dimorphic relationship between genes on Chr6, encoding HLA and  Chr19, encoding KIRs  may elucidate how, why and when NK cells determine self restraint or attack cells infected by pathogens and disease. Chr19 has also been linked to blood pressure mechanics, immunity and checkpoints associated with P53. Cancer mutation burden is shaped by G4 DNA, cell cycle replication stress, DNA repair pathway and mitochondrial dysfunction. G4 DNA overrepresentation generally occurs in tumors with mutations in tumor suppressor gene's such as TP53. 

Whether KIR-HLA relationships are associated with p53 status of NK cells and of its target is unknown. However, it has been reported that cellular metabolism regulates a cells sensitivity to NK cells depending on its P53 status and that P53 pathway is coupled to NK cell maturation leaving open the possibility that a relationship exists

KIR and HLA genes are polymorphic and display significant variations, The independent segregation of these unlinked gene families produces extraordinary diversity in the number and type of KIR-HLA pairs inherited in individuals. Variation affects the KIR repertoire of NK cell clones, NK cell maturation, the capability to deliver signals, and consequently the NK cell response to human diseases.

One study suggests that functional interactions between KIR and HLA modify risks of basal cell carcinoma (BCC) and squamous cell carcinomas (SCC) and that KIR B haplotypes provide selective pressure for altered P53 in BCC tumors.

MtDNA and other insertions into nuclear DNA may have altered Chr19-Chr6 linkage relationships and KIR-HLA validity, affecting the integrity of NK missing-self surveillance. Therefore, P53 dependent metabolism and P53 coupled NK cell education may point to a required synchronicity, obtained through NK education, licensing KIR-HLA and other receptor-ligand combinations for a global NK symbiosis.

The altered landscape of cancer is often characterized by a heterogeneous mix of immunosuppressive metabolites, glucose and amino acid deprivation, hypoxia and acidity, which, in concert, prevent effective anti-tumor immunity, here NK therapies herald great potential.

NK cell co-culture with patient cells selected using precise P53 rankings for a distinct P53-coupled-NK cell education may realize a mature NK subset with P53-paired characteristics. Trojan therapy using autologous or combined allogeneic NK cells may promote licensing, through a broad synchronization including at least KIR-HLA. This ex-vivo approach may resist re-education in vivo and activate against P53-decoupled-KIR-HLA affected cells. The objective is an NK subset that, in vivo will initiate and progress a limited innate immune response and disrupt near-neighbor targets that will contribute to a broader immune response.  

Monday, October 3, 2022

Angiogenic Growth Factor Flood

A previous series, about p53 culminated with "Blastocyst Development - A Perfected Cancer Model" that focused on the parallels in angiogenesis, triggered by blastocyst implantation and progression of tumors beyond ~1mm. Now, a recent study has found that conventional Natural Killer cells (cNK) control vascular remodeling in the uterus during pregnancy by acidifying the extracellular matrix (ECM) with a2V-ATPase that activates MMP-9 that degrades the ECM. Ablation of a2V-ATPase decreases Bax and p53 expression in testis and leads to implantation failure in the female mouse. The degrading ECM releases bound pro-angiogenic growth factors that contribute to Uterine artery (UtA) remodeling characterized by the loss of vascular smooth muscle cells (VSMCs) and dilation of the vessels. Without cNK, the UtA never lose VSMCs and UtA resistance remains high often leading to implantation failure.

Its logical that a timely flood of angiogenic growth factors, previously stored in the ECM would provide instant availability, but whether this explains the maternal-embryonic immune paradox remains to be determined? In the immune paradox maternal NK cells invade and maternal blood vessels are remodeled just before the arrival of trophoblasts, the external cells of the blastocyst, that carry male antigens during formation of the fetal placenta. A sudden flood of angiogenic factors preceding invading trophoblasts could provide the perfect environment required for maternal arterial/vascular remodeling.

Lymphocytes in the uterine lining (decidua) are dominated by a unique decidual natural killer (dNK) cell population. The dNK cell surface phenotype CD56bright CD16− CD3− and macrophages CD14+ CD206+(dMac) support a model whereby dNK cells, capable of killing extra-villous cytotrophoblasts (CTB), are prevented from doing so by neighboring macrophages thus protecting the fetal cells from NK cell attack. Existing research has centered on the function of the abundant and diverse sets of dNK, but now that cNK cells have been identified to play a more significant role, our understanding of the remodeling are likely to change.

In CTB exogenous p53 is able to down-regulate MMP-9 promoter activity, but endogenous p53 is not able to regulate MMP-9 expression in first trimester CTB cells. Inactivation of p53 through mutation is the most common trait in cancer. By loosing its onco-suppressive activity, p53 becomes oncogenic in almost all malignant tumors (Soussi and Lozano, 2005). Although p53 is not mutated in the human placenta, it has become functionally incompetent. Understanding why and how p53 is functionally incompetent in CTB might well be the key to understanding trophoblast invasion.

Downregulation of EMMPRIN (BSG,CD147) by p53 leads to a decrease in the activity of MMP-9 and an inhibition of tumor cell invasion. Upregulation of EMMPRIN seen in many cancers can be attributed to, at least in part, to the dysfunction of p53 and thus provides new evidence for the roles of p53 in tumor development and progression. Epithelial derived MMP-9 exhibits a novel defensive role of tumor suppressor in colitis associated cancer by activating MMP9-Notch1-ARF-p53 axis. MMP-9 mediates Notch1 signaling via p53 to regulate apoptosis, cell cycle arrest, and inflammation. 

The inter-activity of p53, cNK and MMP-9 are complexed, but this novel research may lead to the mechanisms by which arterial remodeling occurs after release of angiogenic factors from ECM. If that shares characteristics of NK invasion into developing tumor micro environment's a new therapeutic approach may arise.