Novel phosphatidylserine-binding molecule enhances antitumor T-cell responses by targeting immunosuppressive exosomes in human tumor microenvironments.

BACKGROUND: The human tumor microenvironment (TME) is a complex and dynamic milieu of diverse acellular and cellular components, creating an immunosuppressive environment, which contributes to tumor progression. We have previously shown that phosphatidylserine (PS) expressed on the surface of exosomes isolated from human TMEs is causally linked to T-cell immunosuppression, representing a potential immunotherapeutic target. In this study, we investigated the effect of ExoBlock, a novel PS-binding molecule, on T-cell responses in the TME. METHODS: We designed and synthesized a new compound, (ZnDPA)6-DP-15K, a multivalent PS binder named ExoBlock. The PS-binding avidity of ExoBlock was tested using an in vitro competition assay. The ability of this molecule to reverse exosome-mediated immunosuppression in vitro was tested using human T-cell activation assays. The in vivo therapeutic efficacy of ExoBlock was then tested in two different human tumor xenograft models, the melanoma-based xenomimetic (X-)mouse model, and the ovarian tumor-based omental tumor xenograft (OTX) model. RESULTS: ExoBlock was able to bind PS with high avidity and was found to consistently and significantly block the immunosuppressive activity of human ovarian tumor and melanoma-associated exosomes in vitro. ExoBlock was also able to significantly enhance T cell-mediated tumor suppression in vivo in both the X-mouse and the OTX model. In the X-mouse model, ExoBlock suppressed tumor recurrence in a T cell-dependent manner. In the OTX model, ExoBlock treatment resulted in an increase in the number as well as function of CD4 and CD8 T cells in the TME, which was associated with a reduction in tumor burden and metastasis, as well as in the number of circulating PS+ exosomes in tumor-bearing mice. CONCLUSION: Our results establish that targeting exosomal PS in TMEs with ExoBlock represents a promising strategy to enhance antitumor T-cell responses.

Toll-like receptor 5 agonist protects mice from dermatitis and oral mucositis caused by local radiation: implications for head-and-neck cancer radiotherapy.

PURPOSE: Development of mucositis is a frequent side effect of radiotherapy of patients with head-and-neck cancer. We have recently reported that bacterial flagellin, an agonist of Toll-like receptor 5 (TLR5), can protect rodents and primates from acute radiation syndrome caused by total body irradiation. Here we analyzed the radioprotective efficacy of TLR5 agonist under conditions of local, single dose or fractionated radiation treatment. METHODS AND MATERIALS: Mice received either single-dose (10, 15, 20, or 25 Gy) or fractioned irradiation (cumulative dose up to 30 Gy) of the head-and-neck area with or without subcutaneous injection of pharmacologically optimized flagellin, CBLB502, 30 min before irradiation. RESULTS: CBLB502 significantly reduced the severity of dermatitis and mucositis, accelerated tissue recovery, and reduced the extent of radiation induced weight loss in mice after a single dose of 15 or 20 Gy but not 25 Gy of radiation. CBLB502 was also protective from cumulative doses of 25 and 30 Gy delivered in two (10 + 15 Gy) or three (3 × 10 Gy) fractions, respectively. While providing protection to normal epithelia, CBLB502 did not affect the radiosensitivity of syngeneic squamous carcinoma SCCVII grown orthotopically in mice. Use of CBLB502 also elicited a radiation independent growth inhibitory effect upon TLR5-expressing tumors demonstrated in the mouse xenograft model of human lung adenocarcinoma A549. CONCLUSION: CBLB502 combines properties of supportive care (radiotherapy adjuvant) and anticancer agent, both mediated via activation of TLR5 signaling in the normal tissues or the tumor, respectively.

Structure-activity relationships and organ specificity in the induction of GST and NQO1 by alkyl-aryl isothiocyanates.

PURPOSE: To compare the ability of alkyl-aryl isothiocyanates (ITCs) to increase the activities of the Phase 2 detoxification enzymes NAD[P]H:quinone acceptor oxidoreductase 1 (NQO1) and glutathione S-transferases (GST) in rat tissues in vivo and in cells in vitro. MATERIALS AND METHODS: Twelve alkyl-aryl ITCs and the fully-reduced derivative of benzyl ITC (cyclohexylmethyl ITC) were administered to rats each day for 5 days. The animals were then killed and organs harvested. The ITCs were also evaluated in a bladder cell line in culture. The activities of NQO1 and GST in the organs and cells were measured. RESULTS: In vivo, the organ most susceptible to the inductive activity of the ITCs was the urinary bladder, with alpha-methylbenzyl ITC and cyclohexylmethyl ITC being the most effective. Inductive activity in the bladder in vivo did not, however, correlate with that in bladder cells in vitro. CONCLUSIONS: Induction of Phase 2 enzymes increases resistance to chemical carcinogenesis. ITCs could therefore be valuable chemopreventative agents, and the specificity of these substances toward the urinary bladder suggest that they could be particularly useful for protecting against bladder cancer. In this regard, alpha-methylbenzyl ITC and cyclohexylmethyl ITC could be especially valuable.

Methamphetamine modulates DC-SIGN expression by mature dendritic cells.

We report that methamphetamine (meth) may act as cofactor in human immunodeficiency virus (HIV)-1 pathogenesis by increasing dendritic cell (DC)-specific intercellular adhesion molecule-3 (ICAM-3) grabbing non-integrin (DC-SIGN) expression on DCs. Mature DCs (MDCs), obtained from normal subjects, cultured with meth show an up-regulation of DC-SIGN gene and protein expression as analyzed by real-time quantitative polymerase chain reaction and fluorescence-activated cell-sorting analyses, respectively. Furthermore, these meth-induced effects were reversed by a dopamine D1 receptor antagonist (SCH 23390) and small interfering RNA specific to the D1 receptor (D1R) demonstrating that meth-induced effects are mediated through these receptors. Furthermore, meth in synergy with the HIV-1 peptide gp120 up-regulates DC-SIGN gene expression by MDCs. These data are the first evidence that meth up-regulates the expression of DC-SIGN on MDCs. A better understanding of the role of DC-SIGN in HIV-1 infection may help to design novel therapeutic strategies against the progression of HIV-1 disease in the drug-using population.