Understanding the crosstalk between natural killer (NK) cells and the tumor microenvironment (TME) has enhanced the potential of exploiting the interplay between activation and inhibition of NK cells ...for immunotherapy. This interaction is crucial for understanding how tumor cells escape NK cell immune surveillance. NK cell dysfunction is regulated by two molecular mechanisms, downregulated activating receptor ligand expression on the tumor cells, and upregulated inhibitory signals delivered to NK cells. Recent studies demonstrated the role of mechanotransduction in modulating NK cell responses in the TME. The immunological synapse represents a functional interface between the NK cell and its target, regulated by Actin Retrograde Flow (ARF), which drives the adhesion molecules and receptors toward the central zone of the immunological synapse (IS). Here, we further characterize the role of ARF in controlling the immune response of NK cells, using CRISPR/cas9-mediated Wiskott–Aldrich Syndrome protein (WASp) gene silencing of NK cells. We demonstrate that WASp regulates ARF velocity, affecting the conformation and function of the key NK inhibitory regulator, SH2-domain containing protein tyrosine phosphatase-1 (SHP-1), and consequently, the NK cell response. Our results demonstrate the potential of modulating the biophysical and intracellular regulation of NK activation as a promising approach for improving immunotherapy.
In this issue of Cancer Discovery, Sans and colleagues identify the transcription factor NKX6-2 as a principal element in maintaining the low-grade gastric cell phenotype of intraductal papillary ...mucinous neoplasms (IPMN) in the pancreas. Their discoveries in patient cohorts and dissection in animal models provide a novel molecular understanding underpinning IPMN differentiation, with implications for risk stratification and therapeutic intervention in pancreatic cancer. See related article by Sans et al., p. 1844 (7).
Abstract
Natural killer (NK) cells are a potent weapon of the immune system against viral infections and tumor growth. The actomyosin network generates forces through the activity of actin filaments ...and myosin motors. This machinery is responsible for the conversion of mechanical forces into biochemical signals in a process termed mechanotransduction. However, the mechanism by which mechanotransduction controls the immune response, and specifically lymphocyte activity, is poorly understood. Here, we demonstrate that actomyosin retrograde flow (ARF) controls NK cell response through a novel interaction between beta-actin with the SH2-domain containing protein tyrosine phosphatase-1 (SHP-1), converting its conformation state, thereby regulating NK cell cytotoxicity. Actin dynamics govern SHP-1 conformational structure dictating its catalytic activity. Indeed, blocking actin dynamics results in reduced SHP-1 activity, by confining SHP-1 to its inactivated “closed” conformation. This reduced enzymatic activity of SHP-1 leads to increased phosphorylation of SHP-1 substrates, an elevation of intracellular calcium flux, and NK cell cytotoxicity. Using multidisciplinary approaches including functional and advanced molecular imaging, we followed the signaling events in individual NK cells from the moment of target cell encounter until the final outcome – target cell killing or NK cell inhibition. Our data suggest that SHP-1 plays a major role as a sensor of ARF-generated forces in the process of mechanotransduction, and reveal a novel mechanism by which regulation of SHP-1 by ARF dictates NK cell killing decisions. Our data identify ARF as a master regulator of the lymphocyte response.
Natural killer (NK) cells discriminate between healthy cells and virally infected or transformed self-cells by tuning activating and inhibitory signals received through cell surface receptors. ...Inhibitory receptors inhibit NK cell function by recruiting and activating the tyrosine phosphatase Src homology 2 (SH2) domain-containing protein tyrosine phosphatase-1 (SHP-1) to the plasma membrane. However, to date, the guanine nucleotide exchange factor VAV1 is the only direct SHP-1 substrate identified in NK cells. We reveal that the adaptor protein linker for activation of T cells (LAT) as well as phospholipase C-γ1 (PLC-γ1) and PLC-γ2 are SHP-1 substrates. Dephosphorylation of Tyr(132) in LAT by SHP-1 in NK cells abrogated the recruitment of PLC-γ1 and PLC-γ2 to the immunological synapse between the NK cell and a cancer cell target, which reduced NK cell degranulation and target cell killing. Furthermore, the ubiquitylation of LAT by the E3 ubiquitin ligases c-Cbl and Cbl-b, which was induced by LAT phosphorylation, led to the degradation of LAT in response to the engagement of inhibitory receptors on NK cells, which abrogated NK cell cytotoxicity. Knockdown of the Cbl proteins blocked LAT ubiquitylation, which promoted NK cell function. Expression of a ubiquitylation-resistant mutant LAT blocked inhibitory receptor signaling, enabling cells to become activated. Together, these data identify previously uncharacterized SHP-1 substrates and inhibitory mechanisms that determine the response of NK cells.
Minimally invasive detection of cell death could prove an invaluable resource in many physiologic and pathologic situations. Cell-free circulating DNA (cfDNA) released from dying cells is emerging as ...a diagnostic tool for monitoring cancer dynamics and graft failure. However, existing methods rely on differences in DNA sequences in source tissues, so that cell death cannot be identified in tissues with a normal genome. We developed amethod of detecting tissue-specific cell death in humans based on tissue-specific methylation patterns in cfDNA. We interrogated tissue-specific methylome databases to identify cell type-specific DNA methylation signatures and developed a method to detect these signatures in mixed DNA samples. We isolated cfDNA from plasma or serum of donors, treated the cfDNA with bisulfite, PCR-amplified the cfDNA, and sequenced it to quantify cfDNA carrying the methylation markers of the cell type of interest. Pancreatic β-cell DNA was identified in the circulation of patients with recently diagnosed type-1 diabetes and islet-graft recipients; oligodendrocyte DNA was identified in patients with relapsing multiple sclerosis; neuronal/glial DNA was identified in patients after traumatic brain injury or cardiac arrest; and exocrine pancreas DNA was identified in patients with pancreatic cancer or pancreatitis. This proof-of-concept study demonstrates that the tissue origins of cfDNA and thus the rate of death of specific cell types can be determined in humans. The approach can be adapted to identify cfDNA derived from any cell type in the body, offering a minimally invasive window for diagnosing and monitoring a broad spectrum of human pathologies as well as providing a better understanding of normal tissue dynamics.
In this work, we review papers that employ game theoretic tools to study the operation and design of modern electric grids. We consider four topics in this context: energy trading, energy balancing, ...grid planning, and system reliability, and we demonstrate the advantages of using game-theoretic approaches for analyzing complex interactions among independent players. The results and conclusions provide insights regarding many aspects of design and operation, such as efficient methodologies for expansion planning, cyber-security, and frequency stability, or fair-benefit allocation among players. A central conclusion is that modeling the system from the perspective of one entity with unlimited information and control span is often impractical, so correct modeling of the selfish behavior of independent players may be critical for the development of future power systems. Another conclusion is that correct usage of incentives by appropriate regulation or sophisticated pricing mechanisms may improve the social welfare, and, in several cases, the results obtained are as good as those obtained by central planning. Using an extensive content analysis, we point to several trends in the current research and attempt to identify the research directions that are currently at the focus of the community.
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