Stattic sensitizes osteosarcoma cells to epidermal growth factor receptor inhibitors via blocking the interleukin 6-induced STAT3 pathway

Osteosarcoma (OS), the most common malignant bone tumor with high metastatic potential, frequently affects children and adolescents. Epidermal growth factor receptor (EGFR)-targeted tyrosine kinase inhibitors exhibit encouraging anti-tumor activity for patients with solid tumors, whereas their effects on OS remain controversial. In the present study, we aimed to elucidate the anti-tumor activity of gefitinib for OS, as well as to explore the underlying mechanisms. Gefitinib inhibits cell viability, tumor growth, cell migration, and invasion and promotes cell apoptosis and G1 cycle arrest in OS at a relatively high concentration via suppressing the PI3K/Akt and ERK pathways. However, gefitinib treatment results in the feedback activation of signal transducer and activator of transcription 3 (STAT3) induced by interleukin 6 (IL-6) secretion. Combined treatment with gefitinib and stattic, an inhibitor for STAT3 phosphorylation, engenders more evident inhibitory effects on cell proliferation, migration, and invasion and promotive effects on cell apoptosis and G1 phase arrest in OS, compared with the single exposure to gefitinib or stattic. Western blot analysis demonstrates that stattic treatment in gefitinib-treated OS abrogates the IL-6-induced STAT3 activation and subsequently further restrains the activities of EGFR, Akt, and ERK pathways in tumor cells. This study confirms that the EGFR inhibitor of gefitinib has moderate anti-tumor effects on OS through IL-6 secretion-mediated STAT3 activation. Additional administration of stattic in EGFR-targeted therapies may contribute to improve the efficacy for OS.

Luteolin Attenuates Diabetic Nephropathy through Suppressing Inflammatory Response and Oxidative Stress by Inhibiting STAT3 Pathway

BACKGROUND

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD). DN has many pathological changes, but tubular injury is considered to be a crucial pathological feature and plays a key role in the progression of DN. Accumulating studies have confirmed that Luteolin (3,4,5,7-tetrahydroxyflavone, Lut) possesses anti-inflammatory and antioxidant activities, which may play a role in kidney protection in DN.

OBJECTIVES

This paper described the effects of Lut on appropriated tubular injury in the kidneys of db/db mice and searched the possible mechanisms underlying the kidney protection effect in DN.

METHODS

Twelve-week-old male C57BL/6 J db/db and C57BL/6 J db/m mice were used for the animal experiments. They were organized into the following five groups for the animal experiments: a db/m group (control, n=6); a db/db group(n=8) ; a db/db group receiving Lut (10 mg/kg/day, n=8)treatment by oral gavage; a db/db group receiving stattic (a selective STAT3 inhibitor,50 mg/Kg/day, n=8) treatment by oral gavage and a db/db group receiving both stattic and Lut treatment by oral gavage.

RESULTS

In this study, we found that Lut might ameliorate glomerular sclerosis and interstitial fibrosis in DN mouse models through inhibiting the inflammatory response and oxidative stress. And it might play its biological function mainly through repressing the STAT3 activation.

CONCLUSIONS

Lut attenuates DN mainly via suppression of inflammatory response and oxidative response. STAT3 pathway is the potential target, which ultimately reduces renal fibrosis and delays the progress of DN.

Signal transducer and activator of transcription 3 inhibition alleviates resistance to BRAF inhibition in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is a rare type of thyroid cancer (TC) with no effective therapeutic strategy. Although surgery, chemotherapy and radiation are all available for ATC treatment, the median survival for ATC patients is less than 6 months. In this study, we aimed to study on resistant mechanisms to B-Raf proto-oncogene serine/threonine kinase (BRAF) inhibitor and identify effective combinational therapy for ATC patients. TC cells were treated with Vemurafenib and cell apoptosis and viability were analyzed by flow cytometry and MTT assay. Monolayer and sphere cells were isolated from ATC cells to detect the mRNA level of stem cell markers and differentiation markers by RT-PCR. Phosphor-STAT3 level in sphere and monolayer cells was tested by Western blotting. The xenotransplantation animal model has established to analyze the anti-tumor effect of Vemurafenib and Stattic combinational therapy. Undifferentiated TC cells were resistant to Vemurafenib treatment. Sphere cells isolated from ATC showed no significant change in cell viability and apoptosis upon Vemurafenib treatment, and expressed a high level of stem cell marker and phosphor-STAT3. STAT3 inhibition enhanced the tumorigenic capacity and increased Vemurafenib sensitivity in ATC cell lines. Stattic significantly enhanced anti-tumor effect of Vemurafenib in mouse model. Our findings demonstrate that the combinational therapy of Vemurafenib and Stattic is an effective therapeutic treatment for ATC patients.

Inhibition of STAT3 prevents bone metastatic progression of prostate cancer in vivo

BACKGROUND

Prostate cancer (PC) metastasizes to the skeleton forming predominantly sclerotic lesions, and there is currently no cure for bone metastatic disease. The transcription factor signal transducer and activator of transcription 3 (STAT3) is implicated as a metastatic driver, but its potential as therapeutic target in bone metastasis has not been investigated. In this study, we evaluated for the first time a STAT3 inhibitor, Napabucasin, as a therapeutic option for bone metastatic PC.

METHODS

Effects of STAT3 inhibitors, Stattic and Napabucasin, on metastatic potential in PC cells were studied in vitro by assessment of migration capacity, self-renewal potential, and tumorsphere formation. For evaluation of the role of STAT3 in initial skeletal establishment of PC cells as well as in progressed castration-resistant PC (CRPC) in bone, human VCaP prostate cancer cells were inoculated in the tibia of mice which subsequently were treated with the STAT3 inhibitor Napabucasin. Bone specimens were analyzed using computed tomography (CT), immunohistochemistry, and quantitative polymerase chain reaction.

RESULTS

The small molecule STAT3 inhibitors Stattic and Napabucasin both effectively impaired metastatic potential of PC cells in vitro. Furthermore, treatment with Napabucasin prevented metastatic establishment in tibial bones in vivo and thereby also the tumor-induced sclerotic bone response seen in vehicle-treated VCaP xenografts. In addition, treatment with Napabucasin of established bone CRPC significantly decreased both tumor burden and tumor-induced trabecular bone volume compared with effects seen in vehicle-treated animals. Anti-mitotic effects were confirmed by decreased Ki67 staining in Napabucasin-treated xenografts compared with vehicle-treated xenografts. Alterations of gene expression in the femoral bone marrow (BM) niche toward the maintenance of hematopoietic stem cells and the myeloid lineage were demonstrated by quantitative real-time polymerase chain reaction and were further reflected by a substantial increase in the number of erythrocytes in BM of Napabucasin-treated mice. Furthermore, a unique pattern of STAT3 phosphorylation in osteoblasts/stromal cells surrounding the areas of tumor cells was demonstrated immunohistochemically in bone xenograft models using several different PC cell lines.

CONCLUSION

Inhibition of STAT3 activity disrupts the bone metastatic niche and targets both the skeletal establishment of PC and advanced bone metastatic CRPC in mice, suggesting STAT3 as a candidate for molecular targeted therapies of skeletal metastatic disease.

Assessment of anti-inflammatory-like, antioxidant activities and molecular docking of three alkynyl-substituted 3-ylidene-dihydrobenzo[d]isothiazole 1,1-dioxide derivatives

The presence of enyne and benzoisothiazole functions in the molecular architecture of compounds 1, 2 and 3 were expected to provide biochemical activities. In the present work, we first examined the molecular surface contact of three alkynyl-substituted 3-ylidenedihydrobenzo[d] isothiazole 1,1-dioxides. The analysis of the Hirshfeld surfaces reveals that only compound 3 exhibited a well-defined red spots, indicating intermolecular interactions identified as S-O⋯H, C-H⋯O and C-O⋯H contacts. Comparative fingerprint histograms of the three compounds show that close pair interactions are dominated by C-H⋯H-C contact. By UV-visible analysis, compound 1 showed the most intense absorbances at 407 and 441 nm, respectively. The radical scavenging activity explored in the DPPH test, shows that only 1 exhibited low anti-radical activity. Furthermore, cellular antioxidant capacity of benzoisothiazoles 1-3 was investigated with PMA-activated HL-60 cells using chemiluminescence and fluorescence techniques in the presence of L-012 and Amplex Red probe, respectively. Results highlight that compound 1 exhibited moderate anti-ROS capacity while compounds 2 and 3 enhanced ROS production. The cytotoxicity test performed on HL-60 cells, using the MTS assay, confirmed the lack of toxicity of the tested benzoisothiazole 1 compared to 2 and 3 which show low cytotoxicity (≤30%). Anti-catalytic activity was evaluated by following the inhibitory potential of the benzoisothiazoles on MPO activity and depicted benzoisothiazoles-MPO interactions by docking. Both SIEFED and docking studies demonstrated an anti-catalytic activity of the tested benzoisothiazoles towards MPO with the best activity for compound 2.

Hiltonol Cocktail Kills Lung Cancer Cells by Activating Cancer-Suppressors, PKR/OAS, and Restraining the Tumor Microenvironment

NSCLC (non-small cell lung cancer) is a leading cause of cancer-related deaths worldwide. Clinical trials showed that Hiltonol, a stable dsRNA representing an advanced form of polyI:C (polyinosinic-polycytidilic acid), is an adjuvant cancer-immunomodulator. However, its mechanisms of action and effect on lung cancer have not been explored pre-clinically. Here, we examined, for the first time, how a novel Hiltonol cocktail kills NSCLC cells. By retrospective analysis of NSCLC patient tissues obtained from the tumor biobank; pre-clinical studies with Hiltonol alone or Hiltonol⁺⁺⁺ cocktail [Hiltonol+anti-IL6+AG490 (JAK2 inhibitor)+Stattic (STAT3 inhibitor)]; cytokine analysis; gene knockdown and gain/loss-of-function studies, we uncovered the mechanisms of action of Hiltonol⁺⁺⁺. We demonstrated that Hiltonol⁺⁺⁺ kills the cancer cells and suppresses the metastatic potential of NSCLC through: (i) upregulation of pro-apoptotic Caspase-9 and Caspase-3, (ii) induction of cytosolic cytochrome c, (iii) modulation of pro-inflammatory cytokines (GRO, MCP-1, IL-8, and IL-6) and anticancer IL-24 in NSCLC subtypes, and (iv) upregulation of tumor suppressors, PKR (protein kinase R) and OAS (2′5′ oligoadenylate synthetase). In silico analysis showed that Lys296 of PKR and Lys66 of OAS interact with Hiltonol. These Lys residues are purportedly involved in the catalytic/signaling activity of the tumor suppressors. Furthermore, knockdown of PKR/OAS abrogated the anticancer action of Hiltonol, provoking survival of cancer cells. Ex vivo analysis of NSCLC patient tissues corroborated that loss of PKR and OAS is associated with cancer advancement. Altogether, our findings unraveled the significance of studying tumor biobank tissues, which suggests PKR and OAS as precision oncological suppressor candidates to be targeted by this novel Hiltonol⁺⁺⁺ cocktail which represents a prospective drug for development into a potent and tailored therapy for NSCLC subtypes.

Targeting mTOR by CZ415 Suppresses Cell Proliferation and Promotes Apoptosis via Lipin-1 in Cervical Cancer In Vitro and In Vivo

CZ415, a novel inhibitor of mammalian target of rapamycin (mTOR) kinase, has demonstrated anti-tumor activity in several types of cancer. However, its biological function and underlying mechanism of action in cervical cancer (CC) have not been fully studied. Two CC cell lines (Hela and Siha) were treated with increasing concentrations of CZ415. Cell viability was tested with the CCK-8 assay, cell proliferation was determined by Edu staining and the colony formation assay, and apoptosis was determined by flow cytometry and Hoechst 33342 staining. Protein expression was evaluated by western blotting. A nude mouse xenograft model was used to confirm the anti-tumor activity of CZ415 in vivo. Hematoxylin and eosin (H&E) and immunohistochemistry (IHC) staining were performed on samples of tumor tissue. Results showed that CZ415 inhibited CC cell survival in a dose- and time-dependent manner, and 100 nanomolar and 48 h were the optimal conditions. In vitro and in vivo experiments showed that treatment with CZ415 significantly inhibited spheroid formation, cell proliferation, and tumor growth. Further studies showed that the anti-cancer effects of CZ415 were due to an induction of apoptosis, which was accompanied by an upregulation of Bax and downregulation of Bcl-2 through Lipin-1. CZ415 also reduced the levels of mTOR/STAT3 expression. However, these phenotypic changes were reversed by overexpression of Lipin-1. Our results suggest that the novel mTOR inhibitor CZ415 mediates tumor malignancy via Lipin-1 and might be useful for treating CC.

The STAT3 inhibitor Stattic acts independently of STAT3 to decrease histone acetylation and modulate gene expression

Signal transducer and activator of transcription 3 (STAT3) is an important transcription factor involved in many physiological functions including embryonic development and immune responses and is often activated under pathological conditions such as cancer. Strategies to inactivate STAT3 are being pursued as potential anticancer therapies and have led to the identification of Stattic (6-nitrobenzo[b]thiophene-1,1-dioxide) as a "specific" STAT3 inhibitor that is often used to interrogate STAT3-mediated gene expression in vitro and in vivo. Here, we show that Stattic exerts many STAT3-independent effects on cancer cells, calling for reassessment of results previously ascribed to STAT3 functions. Studies of the STAT3-deficient prostate cancer cell line PC-3 (PC3) along with STAT3-proficient breast cancer cell lines (MDA-MB-231, SUM149) revealed that Stattic attenuated histone acetylation and neutralized effects of the histone deacetylase (HDAC) inhibitor romidepsin. In PC3 cells, Stattic alone inhibited gene expression of CCL20 and CCL2, but activated expression of TNFA, CEBPD, SOX2, and MYC. In addition, we found that Stattic promoted autophagy and caused cell death. These data point to profound epigenetic effects of Stattic that are independent of its function as a STAT3 inhibitor. Our results demonstrate that Stattic directly or indirectly reduces histone acetylation and suggest reevaluation of Stattic and related compounds as polypharmacological agents through multipronged cytotoxic effects on cancer cells.

Dual PLK1 and STAT3 inhibition promotes glioblastoma cells apoptosis through MYC

Glioblastoma (GBM) is the deadliest primary brain tumor that is highly resistant to current treatments. Polo-like kinase 1 (PLK1) and signal transducer and activator of transcription 3 (STAT3) are highly expressed in gliomas, especially GBM. Previous studies have shown reciprocal activation between PLK1 and STAT3 and that they regulate the same pools of MYC downstream. We have demonstrated that PLK1 and STAT3 levels are elevated in gliomas compared with those in normal brain tissues, and high expression of both PLK1 and STAT3 is associated with poor prognosis in TCGA. Moreover, there was direct or indirect reciprocal regulation between PLK1 and STAT3. Furthermore, we found that PLK1 and STAT3 can regulate the same pools of MYC downstream. Compared to monotherapy, combined treatment of glioma cells with PLK1 and STAT3 inhibitors, BI2536 and Stattic, respectively, showed lower expression of MYC, synergistic induction of cell invasion and apoptosis in vitro, and tumor inhibition in xenografts. PLK1 and STAT3 were able to directly regulate the expression of MYC and induce apoptosis of glioma cells through the regulation of MYC. These findings may help develop a therapeutic strategy for dual inhibition of PLK1 and STAT3 against the tumorigenesis of glioma.

Leptin Downregulates Angulin-1 in Active Crohn's Disease via STAT3

Crohn’s disease (CD) has an altered intestinal barrier function, yet the underlying mechanisms remain to be disclosed. The tricellular tight junction protein tricellulin is involved in the maintenance of the paracellular macromolecule barrier and features an unchanged expression level in CD but a shifted localization. As angulins are known to regulate the localization of tricellulin, we hypothesized the involvement of angulins in CD. Using human biopsies, we found angulin-1 was downregulated in active CD compared with both controls and CD in remission. In T84 and Caco-2 monolayers, leptin, a cytokine secreted by fat tissue and affected in CD, decreased angulin-1 expression. This effect was completely blocked by STAT3 inhibitors, Stattic and WP1066, but only partially by JAK2 inhibitor AG490. The effect of leptin was also seen at a functional level as we observed in Caco-2 cells an increased permeability for FITC-dextran 4 kDa indicating an impaired barrier against macromolecule uptake. In conclusion, we were able to show that in active CD angulin-1 expression is downregulated, which leads to increased macromolecule permeability and is inducible by leptin via STAT3. This suggests that angulin-1 and leptin secretion are potential targets for intervention in CD to restore the impaired intestinal barrier.

N-Acetyl cysteine prevents activities of STAT3 inhibitors, Stattic and BP-1-102 independently of its antioxidant properties

BACKGROUND

Inhibitors for signal transducer and activator of transcription 3 (STAT3), Stattic, BP-1-102, and LLL12 significantly induce apoptosis in transformed Ba/F3 cells expressing an oncogenic fusion protein, nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) that induces the activation of STAT3. We found that the antioxidant reagent, N-acetyl cysteine (NAC) prevented the abilities of Stattic and BP-1-102, but not LLL12 to induce apoptosis in transformed cells expressing NPM-ALK, providing a novel problem in use of STAT3 inhibitors. We herein investigated the mechanisms how NAC prevented the effects of Sttatic and BP-1-102.

METHODS

Ba/F3 cells expressing NPM-ALK and SUDHL-1 cells were treated with antioxidants such as NAC, Trolox or edaravone in combination with STAT3 inhibitors. Phosphorylation of STAT3, cell proliferation rate, cell viability, cell cycle, internucleosomal DNA fragmentation and the intracellular accumulation of reactive oxygen species (ROS) was investigated. The binding of STAT3 inhibitors and NAC was analyzed by LC-MS.

RESULTS

NAC but not Trolox and edaravone diminished the abilities of Stattic and BP-1-102 to induce apoptosis in cells expressing NPM-ALK. The ROS levels in cells expressing NPM-ALK were not markedly affected by the treatments with Stattic and BP-1-102 in combination with NAC, suggesting that NAC inhibited the activity of Stattic and BP-1-102 independent of its antioxidant activity. LC-MS analysis revealed that NAC directly bound to Stattic and BP-1-102. Furthermore, these NAC adducts exhibited no cytotoxicity, and failed to affect the activity of STAT3.

CONCLUSIONS

NAC antagonizes the activities of Stattic and BP-1-102, which inhibit STAT3 activation by interacting with cysteine residues in STAT3.

CRISPR-Cas9 mediated CD133 knockout inhibits colon cancer invasion through reduced epithelial-mesenchymal transition

We previously reported that CD133, as a putative cancer stem cell marker, plays an important role in cell proliferation and invasion in colon cancer. To understand the role of CD133 expression in colon cancer, we evaluated the inhibitory effect of CD133 in colon cancer cells. In this study, we generated CD133^knockout colon cancer cells (LoVo) using the CRISPR-Cas9 gene editing system. CD133⁺ colon cancer cells (LoVo) were infected with the lentiviral vector carrying CD133 gRNA and purified cell by culturing single cell colonies. CD133^knockout cells was validated by western blot and flow cytometry analysis. In functional study, we observed a significant reduction in cell proliferation and colony formation in CRISPR-Cas9 mediated CD133 ^knockout cells in compare with control (P < 0.001). We also found the anticancer effect of stattic was dependent on CD133 expression in colon cancer cells. Although CD133^knockout cells could not completely block the tumorigenic property, they showed remarkable inhibitory effects on the ability of cell migration and invasion (P < 0.001). In addition, we examined the epithelial mesenchymal transition (EMT)-related protein expression by western blot. The result clearly showed a loss of vimentin expression in CD133^knockout cells. Therefore, CRISPR-Cas9 mediated CD133^knockout can be an effective treatment modality for CD133⁺ colon cancer through reducing the characteristics of cancer stem cells.

[STAT3 inhibitor Stattic induced IL-8 production and cell apotosis in THP-1 cells by activating ERK pathway]

Objective To observe the effect of selectively inhibiting STAT3 on the production of IL-8 and cell apoptosis of THP-1 cells by Stattic, and explore the underlying mechanism. Methods THP-1 cells were treated with different concentrations of Stattic ( 0, 1, 5, 10, 15, 20 μmol/L) for 0, 1, 3, 6, 12, 24 hours. Reverse transcription PCR or real-time PCR was performed to detect the mRNA expression of IL-8, IL-6, IL-1β and tumor necrosis factor-α (TNF-α); ELISA was used to detect the protein expression of IL-8; flow cytometry was applied to evaluate the apoptosis of THP-1 cells; and Western blot analysis was performed to detect the phosphorylation of STAT3 and extracellular signal-regulated kinase (ERK). Reverse transcription PCR was used to test the effect of U0126 at different concentrations (0, 1, 5, 10 μmol/L) on the mRNA expression of IL-8 induced by Stattic in THP-1 cells. Results Stattic significantly up-regulated the mRNA and protein expression of IL-8 in THP-1 cells in a concentration range of 10~20 μmol/L, and induced cell apoptosis only at high concentration (15, 20 μmol/L). Treated with Stattic for 0, 1, 3, 6, 12, 24 hours, IL-8 mRNA was significantly up-regulated, and after 6 hours, the expression of IL-8 protein and apoptosis of THP-1 cells were up-regulated in a time-dependent manner. STAT3 phosphorylation was inhibited in a time- and dose-dependent manner by Stattic. ERK phosphorylation was induced by different concentrations of Stattic in a time-dependent manner. In addition, U0126, a selective inhibitor of ERK pathway, inhibited Stattic-induced IL-8 expression in a concentration-dependent manner. Conclusion Stattic, a selective STAT3 inhibitor, can induce the apoptosis and IL-8 production by activating ERK signaling pathway in THP-1 cells.

LY404039 Inhibits Proliferation and Metastasis of Osteosarcoma Cells via PI3K Signaling Pathway

Osteosarcoma is one of the most aggressive primary malignant bone tumors, and the effect of first-line therapeutic schedule had no improvement in past few years. Therefore, it is extremely urgent to develop new drugs against osteosarcoma. In this study, human osteosarcoma U2 OS cells as a model in vitro were treated with LY404039 and dimethyl sulfoxide. CCK-8 proliferation test, transwell assay, and flow cytometry were used to assess cell proliferation, invasion/migration, and apoptosis, respectively. Moreover, western blotting was performed to determine the relative expression of protein related to apoptosis and PI3K signaling pathway. The proliferation of U2 OS cells was significantly inhibited 72 h after LY404039-treatment by CCK-8 proliferation test. Matrigel invasion analysis showed the numbers of invasive cells were significantly decreased in LY404039-treated group compared with the NC group. Furthermore, LY404039 led to the remarkable reduction of the number of U2 OS cells passing through the microwells of the transwell chamber. The expression levels of anti-apoptotic protein BCL-2 decreased, and the expression of pro-apoptotic proteins Active Caspase3, Bax increased concurrently after LY404039 stimulation using western blot. The phosphorylation of AKT and mTOR were significantly inhibited in U2 OS cells treated with LY404039. Also, the activity of the downstream proteins such as p70S6K and Cyclin D1 were also significantly decreased. LY404039 could inhibit proliferation and metastasis of osteosarcoma cells, which might be attributed to the enhancement of apoptosis via PI3K pathway.

Signal transducer and activator of transcription 3 promotes the Warburg effect possibly by inducing pyruvate kinase M2 phosphorylation in liver precancerous lesions

BACKGROUND

Study shows that signal transducer and activator of transcription 3 (STAT3) can increase the Warburg effect by stimulating hexokinase 2 in breast cancer and upregulate lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 in myeloma. STAT3 and pyruvate kinase M2 (PKM2) can also be activated and enhance the Warburg effect in hepatocellular carcinoma. Precancerous lesions are critical to human and rodent hepatocarcinogenesis. However, the underlying molecular mechanism for the development of liver precancerous lesions remains unknown. We hypothesized that STAT3 promotes the Warburg effect possibly by upregulating p-PKM2 in liver precancerous lesions in rats.

AIM

To investigate the mechanism of the Warburg effect in liver precancerous lesions in rats.

METHODS

A model of liver precancerous lesions was established by a modified Solt-Farber method. The liver pathological changes were observed by HE staining and immunohistochemistry. The transformation of WB-F344 cells induced with N-methyl-N’-nitro-N-nitrosoguanidine and hydrogen peroxide was evaluated by the soft agar assay and aneuploidy. The levels of glucose and lactate in the tissue and culture medium were detected with a spectrophotometer. The protein levels of glutathione S-transferase-π, proliferating cell nuclear antigen (PCNA), STAT3, and PKM2 were examined by Western blot and immunofluorescence.

RESULTS

We found that the Warburg effect was increased in liver precancerous lesions in rats. PKM2 and p-STAT3 were upregulated in activated oval cells in liver precancerous lesions in rats. The Warburg effect, p-PKM2, and p-STAT3 expression were also increased in transformed WB-F344 cells. STAT3 activation promoted the clonal formation rate, aneuploidy, alpha-fetoprotein expression, PCNA expression, G1/S phase transition, the Warburg effect, PKM2 phosphorylation, and nuclear translocation in transformed WB-F344 cells. Moreover, the Warburg effect was inhibited by stattic, a specific inhibitor of STAT3, and further reduced in transformed WB-F344 cells after the intervention for PKM2.

CONCLUSION

The Warburg effect is initiated in liver precancerous lesions in rats. STAT3 activation promotes the Warburg effect by enhancing the phosphorylation of PKM2 in transformed WB-F344 cells.

Hepatic STAT3 inhibition amplifies the inflammatory response in obese mice during sepsis

The purpose of this study was to better understand the role obesity plays in the inflammatory response during sepsis, specifically regarding the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway in the liver. We hypothesized that inhibiting STAT3 would lead to an increase in the inflammatory response and that obesity would amplify this effect. To investigate this, we inhibited STAT3 in two ways: pharmacological systemic inhibition and genetic hepatic-specific inhibition. In pharmacological inhibition studies, male C57BL/6 mice were randomized to a high-fat (60% kcal fat) or normal (16% kcal fat) diet for 6-7 wk and pretreated with Stattic before inducing sepsis by cecal ligation and puncture. In genetic inhibition studies, mice were randomized by genotype before induction of sepsis. To investigate obesity in mice with hepatic-specific STAT3 inhibition, we randomized mice to a high-fat or normal diet as described above for 6 mo before induction of sepsis. Body composition was analyzed using EchoMRI. We found that systemic STAT3 inhibition by Stattic resulted in an increased inflammatory response and that obesity amplified this effect. We also found that genetically inhibiting STAT3 in the liver resulted in higher mortality, increased inflammation, and liver injury. High-fat-fed mice with hepatic STAT3 inhibition gained more weight and had more fat than control mice on the same diet, and obesity increased neutrophil infiltration to the liver of these mice during sepsis. In conclusion, STAT3 plays an important regulatory role in the inflammatory response during sepsis, and obesity contributes to the dysregulated response observed when STAT3 is inhibited.

Dual requirement for STAT signaling in dendritic cell immunobiology

Dendritic cells (DC) represent an attractive target for therapeutic manipulation of the immune system and enhancement of insufficient immune response in cancer. STAT family members play key roles in the differentiation and activation of DC, a feature that is currently being exploited in DC-based therapies. We previously reported that the small-molecule Stattic, originally developed as a STAT3-specific inhibitor, also inhibits STAT1 and STAT2 phosphorylation in DC exposed to cytokines or LPS. Aim of this study was to investigate the functional consequences of in vitro treatment with Stattic on DC immunobiology. Interestingly, we observed an opposite effect of Stattic on DC immunophenotype depending on the activation state. While the expression of costimulatory, coinhibitory, MHC class II and CD83 molecules was enhanced in immature DC exposed to Stattic, the LPS induced up-modulation of these molecules was strongly repressed. An effective blockade of LPS-induced secretion of proinflammatory cytokines and capacity to stimulate a Th1 polarization was also observed in the presence of Stattic. Our results indicate that the immunological consequences of STAT inhibition in DC vary depending on the cell activation state. This knowledge is of relevance for anticipating potential effects of STAT-targeted therapeutics, and pursuing selective DC manipulation in clinical applications.

Stat3 regulates centrosome clustering in cancer cells via Stathmin/PLK1

Cancer cells frequently have amplified centrosomes that must be clustered together to form a bipolar mitotic spindle, and targeting centrosome clustering is considered a promising therapeutic strategy. A high-content chemical screen for inhibitors of centrosome clustering identified Stattic, a Stat3 inhibitor. Stat3 depletion and inhibition in cancer cell lines and in tumours in vivo caused significant inhibition of centrosome clustering and viability. Here we describe a transcription-independent mechanism for Stat3-mediated centrosome clustering that involves Stathmin, a Stat3 interactor involved in microtubule depolymerization, and the mitotic kinase PLK1. Furthermore, PLK4-driven centrosome amplified breast tumour cells are highly sensitive to Stat3 inhibitors. We have identified an unexpected role of Stat3 in the regulation of centrosome clustering, and this role of Stat3 may be critical in identifying tumours that are sensitive to Stat3 inhibitors.

Acquired resistance of pancreatic cancer cells to treatment with gemcitabine and HER-inhibitors is accompanied by increased sensitivity to STAT3 inhibition

Drug-resistance is a major contributing factor for the poor prognosis in patients with pancreatic cancer. We have shown previously that the irreversible ErbB family blocker afatinib, is more effective than the reversible EGFR tyrosine kinase inhibitor erlotinib in inhibiting the growth of human pancreatic cancer cells. The aim of this study was to develop human pancreatic cancer cell (BxPc3) variants with acquired resistance to treatment with gemcitabine, afatinib, or erlotinib, and to investigate the molecular changes that accompany the acquisition of a drug-resistant phenotype. We also investigated the therapeutic potential of various agents in the treatment of such drug-resistant variants. Three variant forms of BxPc3 cells with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) were developed following treatment with increasing doses of such drugs. The expression level, mutational and phosphorylation status of various growth factor receptors and downstream cell signaling molecules were determined by FACS, human phopsho-RTK array, and western blot analysis while the sulforhodamine B assay was used for determining the effect of various agents on the growth of such tumours. We found that all three BxPc3 variants with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) also become less sensitive to treatment with the two other agents. Acquisition of resistance to these agents was accompanied by upregulation of p-c-MET, p-STAT3, CD44, increased autocrine production of EGFR ligand amphiregulin and differential activation status of EGFR tyrosine residues as well as downregulation of total and p-SRC. Of all therapeutic interventions examined, including the addition of an anti-EGFR antibody ICR62, an anti-CD44 monoclonal antibody, and of STAT3 or c-MET inhibitors, only treatment with the STAT3 inhibitor Stattic produced a higher growth inhibitory effect in all three drug-resistant variants. In addition, treatment with a combination of afatinib with either c-MET inhibitor Crizotinib or Stattic resulted in an additive or synergistic growth inhibition in all three variants. Our results suggest that activation of STAT3 may play an important role in the acquisition of resistance to gemcitabine and HER inhibitors in pancreatic cancer and warrant further studies on the therapeutic potential of STAT3 inhibitors in such a setting.

Modulation of mGlu2 Receptors, but Not PDE10A Inhibition Normalizes Pharmacologically-Induced Deviance in Auditory Evoked Potentials and Oscillations in Conscious Rats

Improvement of cognitive impairments represents a high medical need in the development of new antipsychotics. Aberrant EEG gamma oscillations and reductions in the P1/N1 complex peak amplitude of the auditory evoked potential (AEP) are neurophysiological biomarkers for schizophrenia that indicate disruption in sensory information processing. Inhibition of phosphodiesterase (i.e. PDE10A) and activation of metabotropic glutamate receptor (mGluR2) signaling are believed to provide antipsychotic efficacy in schizophrenia, but it is unclear whether this occurs with cognition-enhancing potential. The present study used the auditory paired click paradigm in passive awake Sprague Dawley rats to 1) model disruption of AEP waveforms and oscillations as observed in schizophrenia by peripheral administration of amphetamine and the N-methyl-D-aspartate (NMDA) antagonist phencyclidine (PCP); 2) confirm the potential of the antipsychotics risperidone and olanzapine to attenuate these disruptions; 3) evaluate the potential of mGluR2 agonist LY404039 and PDE10 inhibitor PQ-10 to improve AEP deficits in both the amphetamine and PCP models. PCP and amphetamine disrupted auditory information processing to the first click, associated with suppression of the P1/N1 complex peak amplitude, and increased cortical gamma oscillations. Risperidone and olanzapine normalized PCP and amphetamine-induced abnormalities in AEP waveforms and aberrant gamma/alpha oscillations, respectively. LY404039 increased P1/N1 complex peak amplitudes and potently attenuated the disruptive effects of both PCP and amphetamine on AEPs amplitudes and oscillations. However, PQ-10 failed to show such effect in either models. These outcomes indicate that modulation of the mGluR2 results in effective restoration of abnormalities in AEP components in two widely used animal models of psychosis, whereas PDE10A inhibition does not.

Pharmacokinetic characterization of 2-(3-benzoyl)-4-hydroxy-1,1-dioxo-2H-1,2-benzothiazine-2-yl-1-phenylethanone, a novel 11β-hydroxysteroid dehydrogenase type 1 inhibitor in rats

11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is associated with metabolic syndromes such as type 2 diabetes mellitus and obesity. A new 11β-HSD1 inhibitor known as 2-(3-benzoyl)-4-hydroxy-1, 1-dioxo-2H-1, 2-benzothiazine-2-yl-1-phenylethanone (KR-66344) is being developed as a therapeutic agent for these metabolic diseases. The purpose of this study was to characterize the pharmacokinetics of KR-66344 to support further preclinical development. KR-66344 showed high liver microsomal stability with T1/2 values >3 h and high permeability with apparent permeability coefficients of 15.2-24.2 × 10(-6) cm/s in Caco-2 cell monolayers. KR-66344 was also strongly bound to plasma proteins (>98%). After intravenous dosing, KR-66344 exhibited low systemic clearance (0.27-0.37 L/h/kg) and a low to moderate volume of distribution at steady state (0.79-0.8 L/kg). The bioavailability and terminal half-lives of KR-66344 following oral administration were 25% and 1.7-3.3 h, respectively. In addition, KR-66344 showed dose-independent pharmacokinetics at 0.5-10 mg/kg in intravenous and oral pharmacokinetic studies.

Discovery of biomarkers predictive of GSI response in triple-negative breast cancer and adenoid cystic carcinoma

Next-generation sequencing was used to identify Notch mutations in a large collection of diverse solid tumors. NOTCH1 and NOTCH2 rearrangements leading to constitutive receptor activation were confined to triple-negative breast cancers (TNBC; 6 of 66 tumors). TNBC cell lines with NOTCH1 rearrangements associated with high levels of activated NOTCH1 (N1-ICD) were sensitive to the gamma-secretase inhibitor (GSI) MRK-003, both alone and in combination with paclitaxel, in vitro and in vivo, whereas cell lines with NOTCH2 rearrangements were resistant to GSI. Immunohistochemical staining of N1-ICD in TNBC xenografts correlated with responsiveness, and expression levels of the direct Notch target gene HES4 correlated with outcome in patients with TNBC. Activating NOTCH1 point mutations were also identified in other solid tumors, including adenoid cystic carcinoma (ACC). Notably, ACC primary tumor xenografts with activating NOTCH1 mutations and high N1-ICD levels were sensitive to GSI, whereas N1-ICD-low tumors without NOTCH1 mutations were resistant.

SIGNIFICANCE

NOTCH1 mutations, immunohistochemical staining for activated NOTCH1, and HES4 expression are biomarkers that can be used to identify solid tumors that are likely to respond to GSI-based therapies.

Association of toxicity of sorafenib and sunitinib for human keratinocytes with inhibition of signal transduction and activator of transcription 3 (STAT3)

Hand–foot skin reaction is a most common multi-kinase inhibitor-related adverse event. This study aimed to examine whether the toxicity of sorafenib and sunitinib for human keratinocytes was associated with inhibiting signal transduction and activator of transcription 3 (STAT3). We studied whether STAT3 activity affects sorafenib- and sunitinib-induced cell growth inhibition in HaCaT cells by WST-8 assay. Stattic enhanced the cell-growth inhibitory and apoptotic effects of sorafenib and sunitinib. HaCaT cells transfected with constitutively-active STAT3 (STAT3C) were resistant to the sorafenib- and sunitinib-induced cell growth inhibition. STAT3 activity decreased after short-term treatment with sorafenib and sunitinib in a dose-dependent manner and recovered after long-term treatment with sorafenib and sunitinib at low doses. Moreover, the expression of survivin and bcl-2 decreased after treatment with sorafenib and sunitinib was concomitant with variations in STAT3 activity. Sorafenib-induced STAT3 inhibition was mediated by regulation via MAPK pathways in HaCaT cells, while sunitinib-induced STAT3 inhibition was not. Thus, STAT3 activation mediating apoptosis suppressors may be a key factor in sorafenib and sunitinib-induced keratinocyte cytotoxicity.

STAT3 modulation to enhance motor neuron differentiation in human neural stem cells

Spinal cord injury or amyotrophic lateral sclerosis damages spinal motor neurons and forms a glial scar, which prevents neural regeneration. Signal transducer and activator of transcription 3 (STAT3) plays a critical role in astrogliogenesis and scar formation, and thus a fine modulation of STAT3 signaling may help to control the excessive gliogenic environment and enhance neural repair. The objective of this study was to determine the effect of STAT3 inhibition on human neural stem cells (hNSCs). In vitro hNSCs primed with fibroblast growth factor 2 (FGF2) exhibited a lower level of phosphorylated STAT3 than cells primed by epidermal growth factor (EGF), which correlated with a higher number of motor neurons differentiated from FGF2-primed hNSCs. Treatment with STAT3 inhibitors, Stattic and Niclosamide, enhanced motor neuron differentiation only in FGF2-primed hNSCs, as shown by increased homeobox gene Hb9 mRNA levels as well as HB9+ and microtubule-associated protein 2 (MAP2)+ co-labeled cells. The increased motor neuron differentiation was accompanied by a decrease in the number of glial fibrillary acidic protein (GFAP)-positive astrocytes. Interestingly, Stattic and Niclosamide did not affect the level of STAT3 phosphorylation; rather, they perturbed the nuclear translocation of phosphorylated STAT3. In summary, we demonstrate that FGF2 is required for motor neuron differentiation from hNSCs and that inhibition of STAT3 further increases motor neuron differentiation at the expense of astrogliogenesis. Our study thus suggests a potential benefit of targeting the STAT3 pathway for neurotrauma or neurodegenerative diseases.

Increased STAT1 signaling in endocrine-resistant breast cancer

Proteomic profiling of the estrogen/tamoxifen-sensitive MCF-7 cell line and its partially sensitive (MCF-7/LCC1) and fully resistant (MCF-7/LCC9) variants was performed to identify modifiers of endocrine sensitivity in breast cancer. Analysis of the expression of 120 paired phosphorylated and non-phosphorylated epitopes in key oncogenic and tumor suppressor pathways revealed that STAT1 and several phosphorylated epitopes (phospho-STAT1(Tyr701) and phospho-STAT3(Ser727)) were differentially expressed between endocrine resistant and parental controls, confirmed by qRT-PCR and western blotting. The STAT1 inhibitor EGCG was a more effective inhibitor of the endocrine resistant MCF-7/LCC1 and MCF-7/LCC9 lines than parental MCF-7 cells, while STAT3 inhibitors Stattic and WP1066 were equally effective in endocrine-resistant and parental lines. The effects of the STAT inhibitors were additive, rather than synergistic, when tested in combination with tamoxifen in vitro. Expression of STAT1 and STAT3 were measured by quantitative immunofluorescence in invasive breast cancers and matched lymph nodes. When lymph node expression was compared to its paired primary breast cancer expression, there was greater expression of cytoplasmic STAT1 (∼3.1 fold), phospho-STAT3(Ser727) (∼1.8 fold), and STAT5 (∼1.5 fold) and nuclear phospho-STAT3(Ser727) (∼1.5 fold) in the nodes. Expression levels of STAT1 and STAT3 transcript were analysed in 550 breast cancers from publicly available gene expression datasets (GSE2990, GSE12093, GSE6532). When treatment with tamoxifen was considered, STAT1 gene expression was nearly predictive of distant metastasis-free survival (DMFS, log-rank p = 0.067), while STAT3 gene expression was predictive of DMFS (log-rank p<0.0001). Analysis of STAT1 and STAT3 protein expression in a series of 546 breast cancers also indicated that high expression of STAT3 protein was associated with improved survival (DMFS, p = 0.006). These results suggest that STAT signaling is important in endocrine resistance, and that STAT inhibitors may represent potential therapies in breast cancer, even in the resistant setting.

Evaluation of STAT3 signaling in ALDH+ and ALDH+/CD44+/CD24- subpopulations of breast cancer cells

BACKGROUND

STAT3 activation is frequently detected in breast cancer and this pathway has emerged as an attractive molecular target for cancer treatment. Recent experimental evidence suggests ALDH-positive (ALDH(+)), or cell surface molecule CD44-positive (CD44(+)) but CD24-negative (CD24(-)) breast cancer cells have cancer stem cell properties. However, the role of STAT3 signaling in ALDH(+) and ALDH(+)/CD44(+)/CD24(-) subpopulations of breast cancer cells is unknown.

METHODS AND RESULTS

We examined STAT3 activation in ALDH(+) and ALDH(+)/CD44(+)/CD24(-) subpopulations of breast cancer cells by sorting with flow cytometer. We observed ALDH-positive (ALDH(+)) cells expressed higher levels of phosphorylated STAT3 compared to ALDH-negative (ALDH(-)) cells. There was a significant correlation between the nuclear staining of phosphorylated STAT3 and the expression of ALDH1 in breast cancer tissues. These results suggest that STAT3 is activated in ALDH(+) subpopulations of breast cancer cells. STAT3 inhibitors Stattic and LLL12 inhibited STAT3 phosphorylation, reduced the ALDH(+) subpopulation, inhibited breast cancer stem-like cell viability, and retarded tumorisphere-forming capacity in vitro. Similar inhibition of STAT3 phosphorylation, and breast cancer stem cell viability were observed using STAT3 ShRNA. In addition, LLL12 inhibited STAT3 downstream target gene expression and induced apoptosis in ALDH(+) subpopulations of breast cancer cells. Furthermore, LLL12 inhibited STAT3 phosphorylation and tumor cell proliferation, induced apoptosis, and suppressed tumor growth in xenograft and mammary fat pad mouse models from ALDH(+) breast cancer cells. Similar in vitro and tumor growth in vivo results were obtained when ALDH(+) cells were further selected for the stem cell markers CD44(+) and CD24(-).

CONCLUSION

These studies demonstrate an important role for STAT3 signaling in ALDH(+) and ALDH(+)/CD44(+)/CD24(-) subpopulations of breast cancer cells which may have cancer stem cell properties and suggest that pharmacologic inhibition of STAT3 represents an effective strategy to selectively target the cancer stem cell-like subpopulation.

Stat3 inhibitor Stattic exhibits potent antitumor activity and induces chemo- and radio-sensitivity in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus-associated malignancy most common in East Asia, Africa and Alaska. Radiotherapy and cisplatin-based chemotherapy are the main treatment options. Unfortunately, disease response to concurrent chemoradiotherapy varies among patients with NPC, and many cases are resistant to cisplatin and radiotherapy. Signal transducer and activator of transcription 3 (Stat3) has been implicated in the development and progression of various solid tumors. In this study, we assessed the activation and expression of Stat3 in NPC cells. We found that Stat3 was activated and could be blocked by the small molecule inhibitor Stattic. The inhibition of Stat3 in NPC cells by Stattic decreased the expression of cyclin D1 in a dose- and time-dependent manner. Thus, Stattic was used to target Stat3 in NPC cell lines. We found that Stattic could inhibit cell viability and proliferation in NPC cells and significantly induced apoptosis. Additionally, Stat3 transfection attenuated, whereas Stat3 knockdown enhanced, the effects of Stattic upon cell viability inhibition and apoptosis induction. Furthermore, Stattic sensitized NPC cells to cisplatin and ionizing radiation (IR) by preventing cell proliferation and inducing apoptosis. Taken together, Stattic inhibit Stat3 and display antitumor effect in NPC, and enhanced chemosensitivity and radiosensitivity in NPC. Therefore, our findings provide the base for more rational approaches to treat NPC in the clinic.

APE1/Ref-1 regulates STAT3 transcriptional activity and APE1/Ref-1-STAT3 dual-targeting effectively inhibits pancreatic cancer cell survival

Pancreatic cancer is a largely incurable disease, and increasing evidence supports strategies targeting multiple molecular mediators of critical functions of pancreatic ductal adenocarcinoma cells. Intracellular redox state modulates the activity of various signal transduction pathways and biological processes, including cell survival, drug resistance and responsiveness to microenvironmental factors. Recently, it has been shown that the transcription factor STAT3 is under redox control, but the mechanisms involved in its regulation are unknown. Here, we demonstrate for the first time that STAT3 DNA binding and transcriptional activity is directly regulated by the redox function of the APE1/Ref-1 endonuclease, using overexpression and redox-specific mutational strategies, and gene knockdown. Also, pharmacological blockade of APE1/Ref-1 by the redox-selective inhibitor E3330 abrogates STAT3 DNA binding. Since APE1/Ref-1 also exerts redox control on other cancer-associated transcription factors, we assessed the impact of dual-targeting of STAT3 signaling and APE1/Ref-1 redox on pancreatic cancer cell functions. We observed that disruption of APE1/Ref-1 redox activity synergizes with STAT3 blockade to potently inhibit the proliferation and viability of human PDAC cells. Mechanistically, we show that STAT3–APE1/Ref-1 dual targeting promotes marked tumor cell apoptosis, with engagement of caspase-3 signaling, which are significantly increased in comparison to the effects triggered by single target blockade. Also, we show that STAT3–APE1/Ref-1 dual blockade results in significant inhibition of tumor cell migration. Overall, this work demonstrates that the transcriptional activity of STAT3 is directly regulated by the redox function of APE1/Ref-1, and that concurrent blockade of STAT3 and APE1/Ref-1 redox synergize effectively inhibit critical PDAC cell functions.

Diabetes reduces β-cell mitochondria and induces distinct morphological abnormalities, which are reproducible by high glucose in vitro with attendant dysfunction

We investigated the impact of a diabetic state with hyperglycemia on morphometry of β cell mitochondria and modifying influence of a K (+) -ATP channel opener and we related in vivo findings with glucose effects in vitro. For in vivo experiments islets from syngeneic rats were transplanted under the kidney capsule to neonatally streptozotocin-diabetic or non-diabetic recipients. Diabetic recipients received vehicle, or tifenazoxide (NN414), intragastrically for 9 weeks. Non-diabetic rats received vehicle. Transplants were excised 7 d after cessation of treatment (wash-out) and prepared for electron microscopy. Morphological parameters were measured from approx. 25,000 mitochondria. Rat islets were cultured in vitro for 2-3 weeks at 27 or 11 (control) mmol/l glucose. Transplants to diabetic rats displayed decreased numbers of mitochondria (-31%, p < 0.05), increased mitochondrial volume and increased mitochondrial outer surface area, p < 0.001. Diabetes increased variability in mitochondrial size with frequent appearance of mega-mitochondria. Tifenazoxide partly normalized diabetes-induced effects, and mega-mitochondria disappeared. Long-term culture of islets at 27 mmol/l glucose reproduced the in vivo morphological abnormalities. High-glucose culture was also associated with reduced ATP and ADP contents, reduced oxygen consumption, reduced signaling by MitoTracker Red and reduction of mitochondrial proteins (complexes I-IV), OPA 1 and glucose-induced insulin release. We conclude that (1) a long-term diabetic state leads to a reduced number of mitochondria and to distinct morphological abnormalities which are replicated by high glucose in vitro; (2) the morphological abnormalities are coupled to dysfunction; (3) K (+) -ATP channel openers may have potential to partly reverse glucose-induced effects.

Gamma secretase inhibition promotes hypoxic necrosis in mouse pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is a highly lethal disease that is refractory to medical intervention. Notch pathway antagonism has been shown to prevent pancreatic preneoplasia progression in mouse models, but potential benefits in the setting of an established PDA tumor have not been established. We demonstrate that the gamma secretase inhibitor MRK003 effectively inhibits intratumoral Notch signaling in the KPC mouse model of advanced PDA. Although MRK003 monotherapy fails to extend the lifespan of KPC mice, the combination of MRK003 with the chemotherapeutic gemcitabine prolongs survival. Combination treatment kills tumor endothelial cells and synergistically promotes widespread hypoxic necrosis. These results indicate that the paucivascular nature of PDA can be exploited as a therapeutic vulnerability, and the dual targeting of the tumor endothelium and neoplastic cells by gamma secretase inhibition constitutes a rationale for clinical translation.

Targeting both Notch and ErbB-2 signalling pathways is required for prevention of ErbB-2-positive breast tumour recurrence

BACKGROUND

We reported that Notch-1, a potent breast oncogene, is activated in response to trastuzumab and contributes to trastuzumab resistance in vitro. We sought to determine the preclinical benefit of combining a Notch inhibitor (γ-secretase inhibitor (GSI)) and trastuzumab in both trastuzumab-sensitive and trastuzumab-resistant, ErbB-2-positive, BT474 breast tumours in vivo. We also studied if the combination therapy of lapatinib plus GSI can induce tumour regression of ErbB-2-positive breast cancer.

METHODS

We generated orthotopic breast tumour xenografts from trastuzumab- or lapatinib-sensitive and trastuzumab-resistant BT474 cells. We investigated the antitumour activities of two distinct GSIs, LY 411 575 and MRK-003, in vivo.

RESULTS

Our findings showed that combining trastuzumab plus a GSI completely prevented (MRK-003 GSI) or significantly reduced (LY 411 575 GSI) breast tumour recurrence post-trastuzumab treatment in sensitive tumours. Moreover, combining lapatinib plus MRK-003 GSI showed significant reduction of tumour growth. Furthermore, a GSI partially reversed trastuzumab resistance in resistant tumours.

CONCLUSION

Our data suggest that a combined inhibition of Notch and ErbB-2 signalling pathways could decrease recurrence rates for ErbB-2-positive breast tumours and may be beneficial in the treatment of recurrent trastuzumab-resistant disease.

In vitro recovery of ATP-sensitive potassium channels in β-cells from patients with congenital hyperinsulinism of infancy

OBJECTIVE

Congenital hyperinsulinism in infancy (CHI) is characterized by unregulated insulin secretion from pancreatic β-cells; severe forms are associated with defects in ABCC8 and KCNJ11 genes encoding sulfonylurea receptor 1 (SUR1) and Kir6.2 subunits, which form ATP-sensitive K(+) (K(ATP)) channels in β-cells. Diazoxide therapy often fails in the treatment of CHI and may be a result of reduced cell surface expression of K(ATP) channels. We hypothesized that conditions known to facilitate trafficking of cystic fibrosis transmembrane regulator (CFTR) and other proteins in recombinant expression systems might increase surface expression of K(ATP) channels in native CHI β-cells.

RESEARCH DESIGN AND METHODS

Tissue was isolated during pancreatectomy from eight patients with CHI and from adult cadaver organ donors. Patients were screened for mutations in ABCC8 and KCNJ11. Isolated β-cells were maintained at 37°C or 25°C and in the presence of 1) phorbol myristic acid, forskolin and 3-isobutyl-1-methylxanthine, 2) BPDZ 154, or 3) 4-phenylbutyrate. Surface expression of functional channels was assessed by patch-clamp electrophysiology.

RESULTS

Mutations in ABCC8 were detected for all patients tested (n = 7/8) and included three novel mutations. In five of eight patients, no changes in K(ATP) channel activity were observed under different cell culture conditions. However, in three patients, in vitro recovery of functional K(ATP) channels occurred. Here, we report the first cases of recovery of defective K(ATP) channels in human β-cells using modified cell culture conditions.

CONCLUSIONS

Our study establishes the principle that chemical modification of K(ATP) channel subunit trafficking could be of benefit for the future treatment of CHI.

Inhibition of permeability transition pore opening by mitochondrial STAT3 and its role in myocardial ischemia/reperfusion

The signal transducer and activator of transcription 3 (STAT3) contributes to cardioprotection by ischemic pre- and postconditioning. Mitochondria are central elements of cardioprotective signaling, most likely by delaying mitochondrial permeability transition pore (MPTP) opening, and STAT3 has recently been identified in mitochondria. We now characterized the mitochondrial localization of STAT3 and its impact on respiration and MPTP opening. STAT3 was mainly present in the matrix of subsarcolemmal and interfibrillar cardiomyocyte mitochondria. STAT1, but not STAT5 was also detected in mitochondria under physiological conditions. ADP-stimulated respiration was reduced in mitochondria from mice with a cardiomyocyte-specific deletion of STAT3 (STAT3-KO) versus wildtypes and in rat mitochondria treated with the STAT3 inhibitor Stattic (STAT3 inhibitory compound, 6-Nitrobenzo[b]thiophene 1,1-dioxide). Mitochondria from STAT3-KO mice and Stattic-treated rat mitochondria tolerated less calcium until MPTP opening occurred. STAT3 co-immunoprecipitated with cyclophilin D, the target of the cardioprotective agent and MPTP inhibitor cyclosporine A (CsA). However, CsA reduced infarct size to a similar extent in wildtype and STAT3-KO mice in vivo. Thus, STAT3 possibly contributes to cardioprotection by stimulation of respiration and inhibition of MPTP opening.

Inhibition of Notch signaling reduces the stem-like population of breast cancer cells and prevents mammosphere formation

BACKGROUND

Cancer stem cells (CSCs) are believed to be responsible for breast cancer formation and recurrence; therefore, therapeutic strategies targeting CSCs must be developed. One approach may be targeting signaling pathways, like Notch, that are involved in stem cell self-renewal and survival.

MATERIALS AND METHODS

Breast cancer stem-like cells derived from cell lines and patient samples were examined for Notch expression and activation. The effect of Notch inhibition on sphere formation, proliferation, and colony formation was determined.

RESULTS

Breast cancer stem-like cells consistently expressed elevated Notch activation compared with bulk tumor cells. Blockade of Notch signaling using pharmacologic and genomic approaches prevented sphere formation, proliferation, and/or colony formation in soft agar. Interestingly, a gamma-secretase inhibitor, MRK003, induced apoptosis in these cells.

CONCLUSION

Our findings support a crucial role for Notch signaling in maintenance of breast cancer stem-like cells, and suggest Notch inhibition may have clinical benefits in targeting CSCs.

LY-2140023, a prodrug of the group II metabotropic glutamate receptor agonist LY-404039 for the potential treatment of schizophrenia

LY-2140023 is a methionine amide prodrug of the orthosteric metabotropic glutamate receptor (mGluR)2/3 agonist LY-404039, being developed by Eli Lilly & Co, for the potential oral treatment of schizophrenia. LY-404039 is a rigid glutamate analog that selectively binds to mGluR2/3 compared with all other glutamate receptors and transporters, and with other monoaminergic receptors that have been implicated in the therapeutic efficacy of atypical antipsychotic drugs. Activation of mGluR2 has been associated with the antipsychotic-like behavioral effects of LY-404039, as indicated by experiments using mGluR2-/- and mGluR3-/- mice. Furthermore, mGluR2 acts as a glutamatergic autoreceptor in the brain regions that are believed to be important in the pathophysiology of schizophrenia, such as the prefrontal cortex, striatum, hippocampal formation and the thalamus. The antipsychotic efficacy of LY-2140023, predicted by a common battery of preclinical behavioral screens for antipsychotic drugs, was confirmed in a randomized, placebo-controlled, phase II clinical trial in patients with schizophrenia. In addition, LY-2140023 lacked the extrapyramidal and metabolic side effects that are commonly observed with the majority of currently approved antipsychotic drugs. Thus, LY-2140023 represents a rare psychiatric medicine that demonstrates the promise of being rationally developed from bench to bedside.

Amplified hormonal counterregulatory responses to hypoglycemia in rats after systemic delivery of a SUR-1-selective K(+) channel opener?

OBJECTIVE

In glucose-sensing neurons, ATP-sensitive K(+) channels (K(ATP) channels) are thought to translate metabolic signals into an alteration in neuronal firing rates. Because these neurons express the Kir6.2/SUR-1 isoform of the K(ATP) channel, we sought to examine the therapeutic potential of the SUR-1-selective potassium channel opener (KCO), NN414, to amplify counterregulatory response to hypoglycemia.

RESEARCH DESIGN AND METHODS

In vivo dose-response studies with NN414 delivered intravenously to normal Sprague-Dawley rats before the induction of controlled hypoglycemia were performed. Based on these studies, the potential for NN414 to restore counterregulatory responses in chronically cannulated nondiabetic and diabetic BB rats was explored using the in vivo hyperinsulinemic-hypoglycemic clamp technique.

RESULTS

NN414 delivered systemically amplified epinephrine responses during acute hypoglycemia and showed a persisting effect to amplify the epinephrine response when given 24 h before the hypoglycemic study. Local delivery of a potassium-channel blocker to the ventromedial hypothalamus reversed the effects of systemic NN414. In addition, NN414 amplified the epinephrine response to hypoglycemia in both nondiabetic and diabetic BB rats with defective hormonal counterregulation.

CONCLUSIONS

These studies demonstrate in a variety of rodent models that systemic delivery of Kir6.2/SUR-1-selective KCOs enhance the glucose counterregulatory response to insulin-induced hypoglycemia. Future studies in human subjects are now required to determine their potential as a therapy for hypoglycemia-associated autonomic failure in type 1 diabetes.

Novel triple neurokinin receptor antagonist CS-003 inhibits respiratory disease models in guinea pigs

Neurokinins are known to induce neurogenic inflammation related to respiratory diseases. The effects of CS-003 ([1-{2-[(2R)-(3,4-dichlorophenyl)-4-(3,4,5-trimethoxybenzoyl)morpholin-2-yl]ethyl}spiro[benzo[c]thiophene-1(3H),4'-piperidine]-(2S)-oxide hydrochloride]), a novel triple neurokinin receptor antagonist, on several respiratory disease models were evaluated in guinea pigs. As we have already shown that CS-003 is intravenously effective, we first determined if CS-003 was orally effective. CS-003 dose-dependently inhibited substance P-induced tracheal vascular hyperpermeability, neurokinin A- and neurokinin B-induced bronchoconstriction with ID(50) values of 3.6, 1.3 and 0.89 mg/kg (p.o.), respectively. CS-003 (10 mg/kg, p.o.) inhibited the number of coughs induced by capsaicin aerosol (P<0.01) and the antitussive effect was comparable to that of codeine. CS-003 (10 mg/kg, p.o.) also inhibited airway hyperresponsiveness to methacholine chloride in ovalbumin-induced asthma models (P<0.01), a milder one and a severer one. On the other hand, montelukast (10 mg/kg, p.o.), a leukotriene receptor antagonist, significantly inhibited the hyperresponsiveness only in the milder model (P<0.05). In an ovalbumin-induced rhinitis model, oral administration of CS-003 inhibited nasal blockade in a dose-dependent manner and the inhibitory effect was comparable to that of dexamethasone (10 mg/kg, p.o.). CS-003 (i.v.) also dose-dependently inhibited cigarette smoke-induced bronchoconstriction, tracheal vascular hyperpermeability and mucus secretion. These data show that CS-003, a potent orally active triple neurokinin receptor antagonist, may be useful for the treatment of respiratory diseases associated with neurokinins, such as allergic asthma, allergic rhinitis, chronic obstructive pulmonary disease and cough.

Gamma-secretase inhibitor prevents Notch3 activation and reduces proliferation in human lung cancers

Notch receptors are key regulators of development by controlling cell-fate determination in many multicellular organisms. Genes that are important for normal differentiation play a role in cancer when their normal functions became dysregulated. Notch signaling has been shown to promote and maintain survival of many types of cancers, and we previously have shown that Notch3 plays an important role in lung cancer. In this study, we showed that a high percentage of lung cancer lines expressed Jagged1, Notch receptors, and their transcriptional target genes (HES1, Hey1), suggesting that the Notch pathway plays an important role in lung cancer biology. Thus, inhibition of Notch receptor activation represents a compelling treatment strategy. Notch activation requires proteolytic cleavage of the receptor by gamma-secretase protein complex. In this study, we determined the ability of MRK-003, a gamma-secretase inhibitor, to inhibit Notch3 signaling, growth, and apoptosis of lung cancer cell lines in vitro and in vivo using mouse xenograft models. We also found that MRK-003 inhibited Notch3 signaling, reduced tumor cell proliferation, inhibited serum independence, and induced apoptosis. This drug had no effect when Notch3 expression was knocked down using small interfering RNA (siRNA), suggesting that the observed effects were mediated by specific action on this receptor. In conclusion, these results support the hypothesis that inhibition of Notch activation using a gamma-secretase inhibitor represents a potential new approach for the targeted therapy of lung cancer.

In vivo pharmacological characterization of the structurally novel, potent, selective mGlu2/3 receptor agonist LY404039 in animal models of psychiatric disorders

RATIONALE

Data from both preclinical and clinical studies have provided proof of concept that modulation of limbic and forebrain glutamate, via mGlu2/3 receptor agonists, might provide therapeutic benefits in many psychiatric disorders including schizophrenia and anxiety.

OBJECTIVE

The aim of this study was to assess the efficacy of a structurally novel, potent, selective mGlu2/3 receptor agonist with improved bioavailability (LY404039) in animal models predictive of antipsychotic and anxiolytic efficacy.

MATERIALS AND METHODS

LY404039 was assessed in amphetamine- and phencyclidine-induced hyperlocomotion, conditioned avoidance responding, fear-potentiated startle, marble burying, and rotarod behavioral tests. Monoamine release and turnover were assessed using microdialysis and ex vivo tissue levels.

RESULTS

LY404039 attenuated amphetamine- and phencyclidine-induced hyperlocomotion (3-30 and 10 mg/kg, respectively). LY404039 (3-10 mg/kg) inhibited conditioned avoidance responding. LY404039 also reduced fear-potentiated startle in rats (3-30 microg/kg) and marble burying in mice (3-10 mg/kg), indicating anxiolytic-like effects. Importantly, LY404039 did not produce sedative effects or motor impairment as measured by rotarod performance and lack of escape failures in the conditioned avoidance task (at doses up to 30 and 10 mg/kg, respectively). LY404039 (10 mg/kg) also increased dopamine and serotonin release/turnover in the prefrontal cortex.

CONCLUSIONS

These results demonstrate the broad preclinical efficacy of LY404039 across multiple animal models of antipsychotic and anxiolytic efficacy. Additionally, this compound modulates mesocortical neurotransmission and provides a novel mechanism for the treatment of psychiatric disorders that may be associated with improved efficacy and reduced incidence of undesirable side effects. As glutamatergic dysfunction has been linked to the etiology of schizophrenia, clinical studies with more potent mGlu2/3 agonists, such as LY404039, may be useful to explore the validity of this hypothesis.

Design, Synthesis, and Pharmacology of Novel 7-Substituted 3,4-Dihydro-2H-1,2,4-benzothiadiazine 1,1-Dioxides as Positive Allosteric Modulators of AMPA Receptors

A series of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides have been synthesized and evaluated as potentiators of AMPA receptors. Attention was paid to the impact of the substituent introduced at the 7-position of the heterocycle. The biological evaluation was achieved by measuring the AMPA current in rat cortex mRNA-injected Xenopus oocytes. The most potent compound, 4-ethyl-7-fluoro-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide (12a) was found to be active in an object recognition test in rats demonstrating cognition enhancing effects in vivo after oral administration.

Apoptosis in T cell acute lymphoblastic leukemia cells after cell cycle arrest induced by pharmacological inhibition of notch signaling

In this report, inhibitors of the gamma-secretase enzyme have been exploited to characterize the antiproliferative relationship between target inhibition and cellular responses in Notch-dependent human T cell acute lymphoblastic leukemia (T-ALL) cell lines. Inhibition of gamma-secretase led to decreased Notch signaling, measured by endogenous NOTCH intracellular domain (NICD) formation, and was associated with decreased cell viability. Flow cytometry revealed that decreased cell viability resulted from a G(0)/G(1) cell cycle block, which correlated strongly to the induction of apoptosis. These effects associated with inhibitor treatment were rescued by exogenous expression of NICD and were not mirrored when a markedly less active enantiomer was used, demonstrating the gamma-secretase dependency and specificity of these responses. Together, these data strengthen the rationale for using gamma-secretase inhibitors therapeutically and suggest that programmed cell death may contribute to reduction of tumor burden in the clinic.

Pharmacological and pharmacokinetic properties of a structurally novel, potent, and selective metabotropic glutamate 2/3 receptor agonist: in vitro characterization of agonist (-)-(1R,4S,5S,6S)-4-amino-2-sulfonylbicyclo[3.1.0]-hexane-4,6-dicarboxylic acid (LY404039)

Group II metabotropic glutamate (mGlu) receptor agonists, including (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate (LY354740) and (-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate (LY379268), have demonstrated efficacy in animal models of anxiety and schizophrenia, and LY354740 decreased anxiety in human subjects. Herein, we report the in vitro pharmacological profile and pharmacokinetic properties of another potent, selective, and structurally novel mGlu2/3 receptor agonist, (-)-(1R,4S,5S,6S)-4-amino-2-sulfonylbicyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY404039) and provide comparisons with LY354740. Similar to LY354740, LY404039 is a nanomolar potent agonist at recombinant human mGlu2 and mGlu3 receptors (K(i) = 149 and 92, respectively) and in rat neurons expressing native mGlu2/3 receptors (Ki = 88). LY404039 is highly selective for mGlu2/3 receptors, showing more than 100-fold selectivity for these receptors, versus ionotropic glutamate receptors, glutamate transporters, and other receptors targeted by known anxiolytic and antipsychotic medications. Functionally, LY404039 potently inhibited forskolin-stimulated cAMP formation in cells expressing human mGlu2 and mGlu3 receptors. Electrophysiological studies indicated that LY404039 suppressed electrically evoked excitatory activity in the striatum, and serotonin-induced l-glutamate release in the prefrontal cortex; effects reversed by LY341495. These characteristics suggest LY404039 modulates glutamatergic activity in limbic and forebrain areas relevant to psychiatric disorders; and that, similar to LY354740, it works through a mechanism that may be devoid of negative side effects associated with current antipsychotics and anxiolytics. Interestingly, despite the slightly lower potency (approximately 2-5-fold) of LY404039 versus LY354740 in binding, functional, and electrophysiological assays, LY404039 demonstrated higher plasma exposure and better oral bioavailability in pharmacokinetic experiments. Collectively, the current data indicate that LY404039 may be valuable in the treatment of neuropsychiatric disorders, including anxiety and psychosis.

Stattic: a small-molecule inhibitor of STAT3 activation and dimerization

Signal transducers and activators of transcription (STATs) are a family of latent cytoplasmic transcription factors that transmit signals from the cell membrane to the nucleus. One family member, STAT3, is constitutively activated by aberrant upstream tyrosine kinase activities in a broad spectrum of cancer cell lines and human tumors. Screening of chemical libraries led to the identification of Stattic, a nonpeptidic small molecule shown to selectively inhibit the function of the STAT3 SH2 domain regardless of the STAT3 activation state in vitro. Stattic selectively inhibits activation, dimerization, and nuclear translocation of STAT3 and increases the apoptotic rate of STAT3-dependent breast cancer cell lines. We propose Stattic as a tool for the inhibition of STAT3 in cell lines or animal tumor models displaying constitutive STAT3 activation.

Three-dimensional quantitative structure-activity relationships of ATP-sensitive potassium (KATP) channel openers belonging to the 3-alkylamino-4H-1,2,4-benzo- and 3-alkylamino-4H-1,2,4-pyridothiadiazine 1,1-dioxide families

Recent studies have demonstrated that selective activation of pancreatic ATP-sensitive potassium (KATP) channels could be of clinical value in the treatment of type I and type II diabetes, obesity, and hypersinsulinemia. Taking into account these promising therapeutic opportunities, we have explored the 3-alkylamino-4H-1,2,4-pyrido- and 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide families. Among these series, numerous drugs were identified as highly potent and selective openers of either the pancreatic or the aortic KATP channels. Thanks to comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA), quantitative structure-activity relationship approaches using more than 100 compounds, pharmacophoric models explaining the activity and selectivity of the drugs have been elaborated. These models highlighted the importance of several chemical regions for KATP channel activation and could be very helpful for future improvement of drug potency, selectivity, or both. Moreover, an original CoMSIA analysis, using a selectivity index (SI) as a dependent variable, was also performed with the aim of identifying the structural parameters influencing tissue selectivity.

Synthesis and Metabotropic Glutamate Receptor Activity of S-Oxidized Variants of (−)-4-Amino-2-thiabicyclo-[3.1.0]hexane-4,6-dicarboxylate: Identification of Potent, Selective, and Orally Bioavailable Agonists for mGlu2/3 Receptors

(-)-4-Amino-2-thiabicyclo-[3.1.0]hexane-4,6-dicarboxylate (LY389795, (-)-3) is a highly potent and selective agonist of metabotropic glutamate receptors 2 (mGlu2) and 3 (mGlu3). As part of our ongoing research program, we have prepared S-oxidized variants of (-)-3, compounds (-)-10, (+)-11 (LY404040), and (-)-12 (LY404039). Each of these chiral heterobicyclic amino acids displaced specific binding of the mGlu2/3 receptor antagonist 3H-2S-2-amino-2-(1S,2S-2-carboxycycloprop-1-yl)-3-(xanth-9-yl)propanoic acid (3H-LY341495) from membranes expressing recombinant human mGlu2 or mGlu3 and acted as potent agonists in cells expressing these receptor subtypes. Docking of the most potent of these derivatives, (+)-11, to mGlu2 revealed the possibility of an additional H-bond interaction between the sulfoxide oxygen of (+)-11 with tyrosine residue Y236. Pharmacokinetic analysis of mGlu active enantiomers (+)-11 and (-)-12 in rats showed each to be well absorbed following oral administration. Consistent with their mGlu2/3 agonist potency and pharmacokinetic properties, both (+)-11 and (-)-12 blocked phencyclidine-evoked ambulations in a dose-dependent manner, indicating their potential as nonclassical antipsychotic agents.

Synthesis and anti-HIV-1 activity of a novel series of 1,4,2-benzodithiazine-dioxides

Previously, we discovered a series of novel benzodithiazines-dioxides with both antiviral and anticancer activities. In order to design compounds with distinct antiviral properties, we prepared new compounds with modifications on the imidazole and pyrimidine rings. Herein, we present the synthesis and antiviral activity of 8-chloro-2,3-dihydroimidazo[1,2-b][1,4,2]benzodithiazine 5,5-dioxides (22, 23, 30, and 31) and 9-chloro-2,3,4-trihydropyrimido[1,2-b][1,4,2]benzodithiazine 6,6-dioxides (14, 24, 25, and 27). We successfully identified a lead compound with remarkable anti-HIV-1 activity (EC(50)=0.09microM). These compounds showed minimal cytotoxicity and are therefore suitable for antiviral development.

Identification of New Compounds That Trigger Apoptosome-Independent Caspase Activation and Apoptosis

Identification of alternative pathways of caspase activation is an important step to develop new antitumor treatments. We report here the result of a screening with a small chemical library, the Developmental Therapeutics Program-National Cancer Institute "challenge set," on cells expressing mutated caspase-9. We have identified two molecules capable of activating an apoptosome-independent apoptotic pathway. These compounds, named F6 and G5, target the ubiquitin-proteasome system by inhibiting the ubiquitin isopeptidases. We have shown that F6 and G5 induce a rather unique apoptotic pathway, which includes a Bcl-2-dependent but apoptosome-independent mitochondrial pathway with up-regulation of the BH3-only protein Noxa, stabilization of the inhibitor of apoptosis antagonist Smac, but also the involvement of the death receptor pathway. Noxa plays an important role in the induction of mitochondrial fragmentation and caspase activation, whereas the death receptor pathway becomes critical in the absence of a functional apoptosome. This study suggests that screening of chemical libraries on cancer cells with defined mutations in apoptotic key elements can lead to the identification of compounds that are useful to characterize alternative pathways of caspase activation.

New 3-Alkylamino-4H-thieno-1,2,4-thiadiazine 1,1-Dioxide Derivatives Activate ATP-Sensitive Potassium Channels of Pancreatic Beta Cells

Compound 1a (NN414) is a potent opener of Kir6.2/SUR1 K(ATP) channels. Compound 1a inhibits insulin release in vitro and in vivo and preserves beta cell function in preclinical animal models suggesting that such a compound could find use in treatment or prevention of type 1 and type 2 diabetes. The crystal structure and a convergent synthesis of 1a are presented together with a range of new analogues of 1a. Several compounds, e.g., 6-chloro-3-(1-methyl-1-phenylethyl)amino-4H-thieno[3,2-e]-1,2,4-thiadiazine 1,1-dioxide (1h), were found to be potent openers of Kir6.2/SUR1 K(ATP) channels and were able to suppress glucose-stimulated insulin release from rat islets in vitro (EC(50) = 0.04 +/- 0.01 muM) and in vivo after intravenous or peroral administration to hyperinsulinemic obese Zucker rats (ED(50) = 4.0 mg/kg). Structural modifications of this series of K(ATP) channel openers have provided compounds with promising pharmacokinetic properties indicating that brief periods of beta cell rest can be achieved.