Tumor Oxygenation by Myo-Inositol Trispyrophosphate Enhances Radiation Response

PURPOSE Tumor hypoxia is a major limiting factor for successful radiation therapy outcomes, with hypoxic cells being up to 3-fold more radiation resistant than normoxic cells; tumor hypoxia creates a tumor microenvironment that is hostile to immune response. Thus, pharmaceutical-induced tumor oxygenation before radiation therapy represents an interesting method to enhance the efficacy of radiation therapy. Myo-inositol trispyrophosphate (ITPP) triggers a decrease in the affinity of oxygen to hemoglobin, which leads to an increased release of oxygen upon tissue demand, including in hypoxic tumors. METHODS AND MATERIALS The combined treatment modality of high-dose bolus ITPP with a single high-dose fraction of ionizing radiation (IR) was investigated for its mechanics and efficacy in multiple preclinical animal tumor models in immunocompromised and immunocompetent mice. The dynamics of tumor oxygenation were determined by serial hypoxia-oriented bioimaging. Initial and residual DNA damage and the integrity of the tumor vasculature were quantified on the immunohistochemical level in response to the different treatment combinations. RESULTS ITPP application did not affect tumor growth as a single treatment modality, but it rapidly induced tumor oxygenation, as demonstrated by in vivo imaging, and significantly reduced tumor growth when combined with IR. An immunohistochemical analysis of γH2AX foci demonstrated increased initial and residual IR-induced DNA damage as the primary mechanism for radiosensitization within initially hypoxic but ITPP-oxygenated tumor regions. Scheduling experiments revealed that ITPP increases the efficacy of ionizing radiation only when applied before radiation therapy. Irradiation alone damaged the tumor vasculature and increased tumor hypoxia, which were both prevented by combined treatment with ITPP. Interestingly, the combined treatment modality also promoted increased immune cell infiltration. CONCLUSIONS ITPP-mediated tumor oxygenation and vascular protection triggers immediate and delayed processes to enhance the efficacy of ionizing radiation for successful radiation therapy

Exogenous melatonin protects small‐for‐size liver grafts by promoting monocyte infiltration and releases interleukin‐6

Defective regeneration of small‐for‐size (SFS) liver remnants and partial grafts remains a key limiting factor in the application of liver surgery and transplantation. Exogenous melatonin (MLT) has protective effects on hepatic ischemia‐reperfusion injury (IRI), but its influence on graft regeneration is unknown. The aim of the study is to investigate the role of MLT in IRI and graft regeneration in settings of partial liver transplantation. We established three mouse models to study hepatic IRI and regeneration associated with partial liver transplantation: (I) IR+PH group: 60 minutes liver ischemia (IR) plus 2/3 hepatectomy (PH); (II) IR+exPH group: 60 minutes liver IR plus extended hepatectomy (exPH) associated with the SFS syndrome; (III) SFS‐LT group: Arterialized 30% SFS liver transplant. Each group was divided into MLT or vehicle‐treated subgroups. Hepatic injury, inflammatory signatures, liver regeneration, and animal survival rates were assessed. MLT reduced liver injury, enhanced liver regeneration, and promoted interleukin (IL) 6, IL10, and tumor necrosis factor‐α release by infiltrating, inflammatory Ly6C+ F4/80+ monocytes in the IR+PH group. MLT‐induced IL6 significantly improved hepatic microcirculation and survival in the IR+exPH model. In the SFS‐LT group, MLT promoted graft regeneration and increased recipient survival along with increased IL6/GP130‐STAT3 signaling. In IL6−/− mice, MLT failed to promote liver recovery, which could be restored through recombinant IL6. In the IR+exPH and SFS‐LT groups, inhibition of the IL6 co‐receptor GP130 through SC144 abolished the beneficial effects of MLT. MLT ameliorates SFS liver graft IRI and restores regeneration through monocyte‐released IL6 and downstream IL6/GP130‐STAT3 signaling

The CD26/DPP4-inhibitor vildagliptin suppresses lung cancer growth via macrophage-mediated NK cell activity

CD26/dipeptidyl peptidase 4 (DPP4) is a transmembrane protein which is expressed by various malignant cells. We found that the expression of CD26/DPP4 was significantly higher in lung adenocarcinoma samples in our own patient cohort compared to normal lung tissue. We therefore hypothesize that the inhibition of CD26/DPP4 can potentially suppress lung cancer growth. The CD26/DPP4 inhibitor vildagliptin was employed on Lewis Lung Carcinoma (LLC) cell line and a human lung adenocarcinoma (H460) cell line. Two weeks after subcutaneous injection of tumor cells into C57BL/6 and CD1/nude mice, the size of LLC and H460 tumors was significantly reduced by vildagliptin. Immunohistochemically, the number of macrophages (F4/80+) and NK cells (NKp46+) was significantly increased in vildagliptin-treated tumor samples. Mechanistically, we found in vitro that lung cancer cell lines expressed increased levels of surfactant protein upon vildagliptin treatment thereby promoting the pro-inflammatory activity of macrophages. By the depletion of macrophages with clodronate and by using NK cell deficient (IL-15-/-) mice, tumors reversed to the size of controls, suggesting that indeed macrophages and NK cells were responsible for the observed tumor-suppressing effect upon vildagliptin treatment. FACS analysis showed tumor-infiltrating NK cells to express tumor necrosis-related apoptosis-inducing ligand (TRAIL) which induced the intra-cellular stress marker γH2AX. Accordingly, we found upregulated γH2AX in vildagliptin-treated tumors and TRAIL-treated cell lines. Moreover, the effect of vildagliptin-mediated enhanced NK cell cytotoxicity could be reversed by antagonizing the TRAIL receptor. Our data provide evidence that the CD26/DPP4-inhibitor vildagliptin reduces lung cancer growth. We could demonstrate that this effect is exerted by surfactant-activated macrophages and NK cells that act against the tumor via TRAIL-mediated cytotoxicity

The CD26/DPP4-inhibitor vildagliptin suppresses lung cancer growth via macrophage-mediated NK cell activity

CD26/dipeptidyl peptidase 4 (DPP4) is a transmembrane protein which is expressed by various malignant cells. We found that the expression of CD26/DPP4 was significantly higher in lung adenocarcinoma samples in our own patient cohort compared to normal lung tissue. We therefore hypothesize that the inhibition of CD26/DPP4 can potentially suppress lung cancer growth. The CD26/DPP4 inhibitor vildagliptin was employed on Lewis Lung Carcinoma (LLC) cell line and a human lung adenocarcinoma (H460) cell line. Two weeks after subcutaneous injection of tumor cells into C57BL/6 and CD1/nude mice, the size of LLC and H460 tumors was significantly reduced by vildagliptin. Immunohistochemically, the number of macrophages (F4/80+) and NK cells (NKp46+) was significantly increased in vildagliptin-treated tumor samples. Mechanistically, we found in vitro that lung cancer cell lines expressed increased levels of surfactant protein upon vildagliptin treatment thereby promoting the pro-inflammatory activity of macrophages. By the depletion of macrophages with clodronate and by using NK cell deficient (IL-15-/-) mice, tumors reversed to the size of controls, suggesting that indeed macrophages and NK cells were responsible for the observed tumor-suppressing effect upon vildagliptin treatment. FACS analysis showed tumor-infiltrating NK cells to express tumor necrosis-related apoptosis-inducing ligand (TRAIL) which induced the intra-cellular stress marker γH2AX. Accordingly, we found upregulated γH2AX in vildagliptin-treated tumors and TRAIL-treated cell lines. Moreover, the effect of vildagliptin-mediated enhanced NK cell cytotoxicity could be reversed by antagonizing the TRAIL receptor. Our data provide evidence that the CD26/DPP4-inhibitor vildagliptin reduces lung cancer growth. We could demonstrate that this effect is exerted by surfactant-activated macrophages and NK cells that act against the tumor via TRAIL-mediated cytotoxicity

Serotonin uptake is required for Rac1 activation in Kras-induced acinar-to-ductal metaplasia in the pancreas

Pancreatic ductal adenocarcinoma (PDAC), the primary cause of pancreatic cancer mortality, is poorly responsive to currently available interventions. Identifying new targets that drive PDAC formation and progression is critical to develop alternative therapeutic strategies to treat this lethal malignancy. Using genetic and pharmacologic approaches, we investigated in vivo and in vitro whether uptake of the monoamine serotonin is required for PDAC development. We demonstrated that pancreatic acinar cells have the ability to readily take up serotonin in a transport-mediated manner. Serotonin uptake promoted the activation of the small GTPase Ras-Related C3 Botulinum Toxin Substrate 1 (Rac1), which is required for trans-differentiation of acinar cells into acinar-to-ductal metaplasia (ADM), a key determinant in PDAC development. Consistent with the central role played by Rac1 in ADM formation, inhibition of the serotonin transporter Sert (Slc6a4) with fluoxetine reduced ADM formation both in vitro and in vivo in a cell autonomous manner. In addition, fluoxetine treatment profoundly compromised the stromal reaction and affected proliferation and lipid metabolism of malignant PDAC cells. We propose that Sert is a promising therapeutic target to counteract the early event of acinar-to-ductal metaplasia with the potential to stall initiation and progression of pancreatic carcinogenesis. This article is protected by copyright. All rights reserved