PI3Kγ stimulates a high molecular weight form of myosin light chain kinase to promote myeloid cell adhesion and tumor inflammation

AbstractMyeloid cells play key roles in cancer immune suppression and tumor progression. In response to tumor derived factors, circulating monocytes and granulocytes extravasate into the tumor parenchyma where they stimulate angiogenesis, immune suppression and tumor progression. Chemokines, cytokines and interleukins stimulate PI3Kγ-mediated Rap1 activation, leading to conformational changes in integrin α4β1 that promote myeloid cell extravasation and tumor inflammation Here we show that PI3Kγ activates a high molecular weight form of myosin light chain kinase, MLCK210, that promotes myosin-dependent Rap1 GTP loading, leading to integrin α4β1 activation. Genetic or pharmacological inhibition of MLCK210 suppresses integrin α4β1 activation, as well as tumor inflammation and progression. These results demonstrate a critical role for myeloid cell MLCK210 in tumor inflammation and serve as basis for the development of alternative approaches to develop immune oncology therapeutics.</jats:p

PI3Kγ is a molecular switch that controls immune suppression

Macrophages play critical, but opposite, roles in acute and chronic inflammation and cancer1,2,3,4,5. In response to pathogens or injury, inflammatory macrophages express cytokines that stimulate cytotoxic T cells, whereas macrophages in neoplastic and parasitic diseases express anti-inflammatory cytokines that induce immune suppression and may promote resistance to T cell checkpoint inhibitors1,2,3,4,5,6,7. Here we show that macrophage PI 3-kinase γ controls a critical switch between immune stimulation and suppression during inflammation and cancer. PI3Kγ signalling through Akt and mTor inhibits NFκB activation while stimulating C/EBPβ activation, thereby inducing a transcriptional program that promotes immune suppression during inflammation and tumour growth. By contrast, selective inactivation of macrophage PI3Kγ stimulates and prolongs NFκB activation and inhibits C/EBPβ activation, thus promoting an immunostimulatory transcriptional program that restores CD8+ T cell activation and cytotoxicity. PI3Kγ synergizes with checkpoint inhibitor therapy to promote tumour regression and increased survival in mouse models of cancer. In addition, PI3Kγ-directed, anti-inflammatory gene expression can predict survival probability in cancer patients. Our work thus demonstrates that therapeutic targeting of intracellular signalling pathways that regulate the switch between macrophage polarization states can control immune suppression in cancer and other disorders

Integrin CD11b activation drives anti-tumor innate immunity

Myeloid cells are recruited to damaged tissues where they can resolve infections and tumor growth or stimulate wound healing and tumor progression. Recruitment of these cells is regulated by integrins, a family of adhesion receptors that includes integrin CD11b. Here we report that, unexpectedly, integrin CD11b does not regulate myeloid cell recruitment to tumors but instead controls myeloid cell polarization and tumor growth. CD11b activation promotes pro-inflammatory macrophage polarization by stimulating expression of microRNA Let7a. In contrast, inhibition of CD11b prevents Let7a expression and induces cMyc expression, leading to immune suppressive macrophage polarization, vascular maturation, and accelerated tumor growth. Pharmacological activation of CD11b with a small molecule agonist, Leukadherin 1 (LA1), promotes pro-inflammatory macrophage polarization and suppresses tumor growth in animal models of murine and human cancer. These studies identify CD11b as negative regulator of immune suppression and a target for cancer immune therapy

Nanotechnology in peripheral nerve repair and reconstruction

The recent progress in biomaterials science and development of tubular conduits (TCs) still fails in solving the current challenges in the treatment of peripheral nerve injuries (PNIs), in particular when disease-related and long-gap defects need to be addressed. Nanotechnology-based therapies that seemed unreachable in the past are now being considered for the repair and reconstruction of PNIs, having the power to deliver bioactive molecules in a controlled manner, to tune cellular behavior, and ultimately guide tissue regeneration in an effective manner. It also offers opportunities in the imaging field, with a degree of precision never achieved before, which is useful for diagnosis, surgery and in the patientâ s follow-up. Nanotechnology approaches applied in PNI regeneration and theranostics, emphasizing the ones that are moving from the lab bench to the clinics, are herein overviewed.The authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for the financial support provided to Joaquim M. Oliveira (IF/01285/2015) and Joana Silva-Correia (IF/00115/2015) under the program “Investigador FCT”.info:eu-repo/semantics/publishedVersio

PI3Kgamma activates integrin alpha4 and promotes immune suppressive myeloid cell polarization during tumor progression

Immunosuppressive myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs) accumulate in tumors where they inhibit T cell-mediated antitumor immune responses and promote tumor progression. Myeloid cell PI3Kγ plays a role in regulating tumor immune suppression by promoting integrin α4-dependent MDSC recruitment to tumors and by stimulating the immunosuppressive polarization of MDSCs and TAMs. Here, we show that integrin α4 promotes immunosuppressive polarization of MDSCs and TAMs downstream of PI3Kγ, thereby inhibiting antitumor immunity. Genetic or pharmacological suppression of either PI3Kγ or integrin α4 blocked MDSC recruitment to tumors and also inhibited immune suppressive myeloid cell polarization, thereby reducing expression of IL10 and increasing expression of IL12 and IFNγ within tumors. Inhibition of PI3Kγ or integrin α4 within tumors stimulated dendritic cell and CD8+ T-cell recruitment and maturation, as well as tumor cell cytotoxicity in vivo, thereby inhibiting tumor growth. As blockade of PI3Kγ or integrin α4 prevents accumulation of MDSC and reduces myeloid cell expression of immunosuppressive factors that stimulate tumor immune escape, these results highlight PI3Kγ and integrin α4 as targets for the design of cancer therapeutics. Cancer Immunol Res; 5(11); 957-68. ©2017 AACR