TIGIT/CD155 axis mediates resistance to immunotherapy in patients with melanoma with the inflamed tumor microenvironment

Background Patients with cancer benefit from treatment with immune checkpoint inhibitors (ICIs), and those with an inflamed tumor microenvironment (TME) and/or high tumor mutation burden (TMB), particularly, tend to respond to ICIs; however, some patients fail, whereas others acquire resistance after initial response despite the inflamed TME and/or high TMB. We assessed the detailed biological mechanisms of resistance to ICIs such as programmed death 1 and/or cytotoxic T-lymphocyte-associated protein 4 blockade therapies using clinical samples. Methods We established four pairs of autologous tumor cell lines and tumor-infiltrating lymphocytes (TILs) from patients with melanoma treated with ICIs. These tumor cell lines and TILs were subjected to comprehensive analyses and in vitro functional assays. We assessed tumor volume and TILs in vivo mouse models to validate identified mechanism. Furthermore, we analyzed additional clinical samples from another large melanoma cohort. Results Two patients were super-responders, and the others acquired resistance: the first patient had a non-inflamed TME and acquired resistance due to the loss of the beta-2 microglobulin gene, and the other acquired resistance despite having inflamed TME and extremely high TMB which are reportedly predictive biomarkers. Tumor cell line and paired TIL analyses showed high CD155, TIGIT ligand, and TIGIT expression in the tumor cell line and tumor-infiltrating T cells, respectively. TIGIT blockade or CD155-deletion activated T cells in a functional assay using an autologous cell line and paired TILs from this patient. CD155 expression increased in surviving tumor cells after coculturing with TILs from a responder, which suppressed TIGIT+ T-cell activation. Consistently, TIGIT blockade or CD155-deletion could aid in overcoming resistance to ICIs in vivo mouse models. In clinical samples, CD155 was related to resistance to ICIs in patients with melanoma with an inflamed TME, including both primary and acquired resistance. Conclusions The TIGIT/CD155 axis mediates resistance to ICIs in patients with melanoma with an inflamed TME, promoting the development of TIGIT blockade therapies in such patients with cancer

Overexpression of TFAM or Twinkle Increases mtDNA Copy Number and Facilitates Cardioprotection Associated with Limited Mitochondrial Oxidative Stress

Background Mitochondrial DNA (mtDNA) copy number decreases in animal and human heart failure (HF), yet its role in cardiomyocytes remains to be elucidated. Thus, we investigated the cardioprotective function of increased mtDNA copy number resulting from the overexpression of human transcription factor A of mitochondria (TFAM) or Twinkle helicase in volume overload (VO)-induced HF. Methods and Results Two strains of transgenic (TG) mice, one overexpressing TFAM and the other overexpressing Twinkle helicase, exhibit an approximately 2-fold equivalent increase in mtDNA copy number in heart. These TG mice display similar attenuations in eccentric hypertrophy and improved cardiac function compared to wild-type (WT) mice without any deterioration of mitochondrial enzymatic activities in response to VO, which was accompanied by a reduction in matrix-metalloproteinase (MMP) activity and reactive oxygen species after 8 weeks of VO. Moreover, acute VO-induced MMP-2 and MMP-9 upregulation was also suppressed at 24 h in both TG mice. In isolated rat cardiomyocytes, mitochondrial reactive oxygen species (mitoROS) upregulated MMP-2 and MMP-9 expression, and human TFAM (hTFAM) overexpression suppressed mitoROS and their upregulation. Additionally, mitoROS were equally suppressed in H9c2 rat cardiomyoblasts that overexpress hTFAM or rat Twinkle, both of which exhibit increased mtDNA copy number. Furthermore, mitoROS and mitochondrial protein oxidation from both TG mice were suppressed compared to WT mice. Conclusions The overexpression of TFAM or Twinkle results in increased mtDNA copy number and facilitates cardioprotection associated with limited mitochondrial oxidative stress. Our findings suggest that increasing mtDNA copy number could be a useful therapeutic strategy to target mitoROS in HF.Peer reviewe

C-ON Bond Homolysis of Alkoxyamines, Part 11: Activation of the Nitroxyl Fragment

International audienceA few years ago, Bagryanskaya and colleagues (J. Org. Chem. 2011) showed that protonation of the nitroxyl fragment deactivated the alkoxyamine C-ON bond. Conversely, our group showed that protonation (Chem. Commun. 2011), as well as other chemical reactions such as oxidation or amine quaternization (Org. Lett. 2012), of the pyridyl moiety carried by the alkyl fragment was suitable to activate the homolysis of the C-ON bond. To pursue our goal of applying alkoxyamines as theranostic agents (Org. Biomol. Chem. 2014 and Mol. Pharmaceutics 2014) by activation of the C-ON bond homolysis, we turned our interest to the chemical activation of the nitroxyl fragment by oxidation/reduction of selected functions. Conversion of a hydroxyl group located close to the nitroxyl moiety successively into aldehyde, then acid, and eventually into ester, led to a successive decrease in k(d)

Dual-initiator alkoxyamines with an N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide moiety for preparation of block co-polymers

International audienceDual initiators for controlled radical/ionic polymerization reactions attract much attention in terms of preparation of new materials. We studied the potential of dual-initiator alkoxyamines 3 [based both on para-substituted aromatic ring for external triggering or initiation of orthogonal polymerization and on N-tert-butyl-N-(1-diethylphosphono-2,2-dimethylpropyl) nitroxide (SG1)] for nitroxide-mediated polymerization (NMP) with various monomers such as styrene, styrene sulphonate, 2-vinyl pyridine or methylmethacrylate. Alkoxyamines 3 were found to be as efficient in the NMP process as N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)hydroxylamine (1). Furthermore, in sharp contrast to 1, alkoxyamines 3 were easier to functionalize

C-ON bond homolysis in alkoxyamines. Part 12: the effect of the para-substituent in the 1-phenylethyl fragment

International audienceThe application of alkoxyamines as initiators/controllers in nitroxide mediated polymerization and as agents for theranostics requires the development of switchable (from stable one to labile one) alkoxyamines. One way to achieve this is to tune the polarity of various groups carried by either the alkyl fragment or the nitroxyl fragment. Thus, the effect of protonation/deprotonation of the para-functionalized aryl moiety carried by the alkyl fragment in diethyl(2,2-dimethyl-1-((1,1-dimethylethyl)(1-para-subsituted-phenylethoxy) amino) propyl) phosphonate is investigated. An increase in k(d) is observed with increasing localized electrical effect, i.e., in the presence of electron withdrawing groups at the para position of the phenyl ring. A striking effect of the intimate ion pair on kd is also observed