A regulatory circuit controlled by extranuclear and nuclear retinoic acid receptor α determines T cell activation and function

Ligation of retinoic acid receptor alpha (RARα) by RA promotes varied transcriptional programs associated with immune activation and tolerance, but genetic deletion approaches suggest the impact of RARα on TCR signaling. Here, we examined whether RARα would exert roles beyond transcriptional regulation. Specific deletion of the nuclear isoform of RARα revealed an RARα isoform in the cytoplasm of T cells. Extranuclear RARα was rapidly phosphorylated upon TCR stimulation and recruited to the TCR signalosome. RA interfered with extranuclear RARα signaling, causing suboptimal TCR activation while enhancing FOXP3+ regulatory T cell conversion. TCR activation induced the expression of CRABP2, which translocates RA to the nucleus. Deletion of Crabp2 led to increased RA in the cytoplasm and interfered with signalosome-RARα, resulting in impaired anti-pathogen immunity and suppressed autoimmune disease. Our findings underscore the significance of subcellular RA/RARα signaling in T cells and identify extranuclear RARα as a component of the TCR signalosome and a determinant of immune responses.

NANOBODY® Molecule, a Giga Medical Tool in Nanodimensions

Although antibodies remain the most widely used tool for biomedical research, antibody technology is not flawless. Innovative alternatives, such as Nanobody® molecules, were developed to address the shortcomings of conventional antibodies. Nanobody® molecules are antigen-binding variable-domain fragments derived from the heavy-chain-only antibodies of camelids (VHH) and combine the advantageous properties of small molecules and monoclonal antibodies. Nanobody® molecules present a small size (~15 kDa, 4 nm long and 2.5 nm wide), high solubility, stability, specificity, and affinity, ease of cloning, and thermal and chemical resistance. Recombinant production in microorganisms is cost-effective, and VHH are also building blocks for multidomain constructs. These unique features led to numerous applications in fundamental research, diagnostics, and therapy. Nanobody® molecules are employed as biomarker probes and, when fused to radioisotopes or fluorophores, represent ideal non-invasive in vivo imaging agents. They can be used as neutralizing agents, receptor-ligand antagonists, or in targeted vehicle-based drug therapy. As early as 2018, the first Nanobody®, Cablivi (caplacizumab), a single-domain antibody (sdAb) drug developed by French pharmaceutical giant Sanofi for the treatment of adult patients with acquired thrombocytopenic purpura (aTTP), was launched. Nanobody® compounds are ideal tools for further development in clinics for diagnostic and therapeutic purposes.

KRAS Addiction Promotes Cancer Cell Adaptation in Harsh Microenvironment Through Macropinocytosis

KRAS is the most frequently mutated oncogene in cancer and despite intensive studies, attempts to develop effective therapies targeting KRAS or its downstream signaling have failed mostly due to the complexity of KRAS activation and function in cancer initiation and progression. Over the years, KRAS has been involved in several biological processes including cell survival, proliferation, and metabolism by promoting not only a favorable tumor environment but also a cell-microenvironment dialog to allow cancer cells to adapt to tumor microenvironment scarcity. One of the mechanisms involved in this adaption is KRAS-mediated macropinocytosis. Macropinocytosis is an evolutionarily conserved, large-scale, and nonselective form of endocytosis involving actin-driven cell membrane remodeling to engulf large amounts of extracellular fluids and proteins from the local environment. While macropinocytosis process has been known for decades, recent gain interest due to its regulation of KRAS-driven tumor growth in adverse microenvironments. By promoting extracellular protein and other macromolecules internalization, macropinocytosis provides a survival mechanism under nutrient scarce conditions and the potential for unrestricted tumor growth. Thus, a better understanding of macropinocytotic process is needed to develop alternative therapeutic strategies.

Lung Adenocarcinoma Tumor Origin: A Guide for Personalized Medicine

Simple Summary

Lung cancer is the leading cause of cancer-related death worldwide, with an average 5-year survival rate of approximately 15%. Among the multiple histological type of lung cancer, adenocarcinoma is the most common. Adenocarcinoma is characterized by a high degree of heterogeneity at many levels, including histological, cellular, and molecular. Understanding the cell of origin of adenocarcinoma, and the molecular changes during tumor progression, will allow better therapeutic strategies.

Abstract

Lung adenocarcinoma, the major form of lung cancer, is the deadliest cancer worldwide, due to its late diagnosis and its high heterogeneity. Indeed, lung adenocarcinoma exhibits pronounced inter- and intra-tumor heterogeneity cofounding precision medicine. Tumor heterogeneity is a clinical challenge driving tumor progression and drug resistance. Several key pieces of evidence demonstrated that lung adenocarcinoma results from the transformation of progenitor cells that accumulate genetic abnormalities. Thus, a better understanding of the cell of origin of lung adenocarcinoma represents an opportunity to unveil new therapeutic alternatives and stratify patient tumors. While the lung is remarkably quiescent during homeostasis, it presents an extensive ability to respond to injury and regenerate lost or damaged cells. As the lung is constantly exposed to potential insult, its regenerative potential is assured by several stem and progenitor cells. These can be induced to proliferate in response to injury as well as differentiate into multiple cell types. A better understanding of how genetic alterations and perturbed microenvironments impact progenitor-mediated tumorigenesis and treatment response is of the utmost importance to develop new therapeutic opportunities.

Macropinocytosis requires Gal-3 in a subset of patient-derived glioblastoma stem cells

Recently, we involved the carbohydrate-binding protein Galectin-3 (Gal-3) as a druggable target for KRAS-mutant-addicted lung and pancreatic cancers. Here, using glioblastoma patient-derived stem cells (GSCs), we identify and characterize a subset of Gal-3high glioblastoma (GBM) tumors mainly within the mesenchymal subtype that are addicted to Gal-3-mediated macropinocytosis. Using both genetic and pharmacologic inhibition of Gal-3, we showed a significant decrease of GSC macropinocytosis activity, cell survival and invasion, in vitro and in vivo. Mechanistically, we demonstrate that Gal-3 binds to RAB10, a member of the RAS superfamily of small GTPases, and β1 integrin, which are both required for macropinocytosis activity and cell survival. Finally, by defining a Gal-3/macropinocytosis molecular signature, we could predict sensitivity to this dependency pathway and provide proof-of-principle for innovative therapeutic strategies to exploit this Achilles' heel for a significant and unique subset of GBM patients.

A small-molecule P2RX7 activator promotes anti-tumor immune responses and sensitizes lung tumor to immunotherapy

Only a subpopulation of non-small cell lung cancer (NSCLC) patients responds to immunotherapies, highlighting the urgent need to develop therapeutic strategies to improve patient outcome. We develop a chemical positive modulator (HEI3090) of the purinergic P2RX7 receptor that potentiates αPD-1 treatment to effectively control the growth of lung tumors in transplantable and oncogene-induced mouse models and triggers long lasting antitumor immune responses. Mechanistically, the molecule stimulates dendritic P2RX7-expressing cells to generate IL-18 which leads to the production of IFN-γ by Natural Killer and CD4+ T cells within tumors. Combined with immune checkpoint inhibitor, the molecule induces a complete tumor regression in 80% of LLC tumor-bearing mice. Cured mice are also protected against tumor re-challenge due to a CD8-dependent protective response. Hence, combination treatment of small-molecule P2RX7 activator followed by immune checkpoint inhibitor represents a strategy that may be active against NSCLC.

Dermal Fibroblast SLC3A2 Deficiency Leads to Premature Aging and Loss of Epithelial Homeostasis

Skin homeostasis relies on fine-tuning of epidermis-dermis interactions and is affected by aging. While extracellular matrix (ECM) proteins, such as integrins, are involved in aging, the molecular basis of the skin changes needs to be investigated further. Here, we showed that integrin co-receptor, SLC3A2, required for cell proliferation, is expressed at the surface of resting dermal fibroblasts in young patients and is reduced drastically with aging. In vivo SLC3A2 dermal fibroblast deletion induced major skin phenotypes resembling premature aging. Knockout mice (3 months old) presented strong defects in skin elasticity due to altered ECM assembly, which impairs epidermal homeostasis. SLC3A2 dermal fibroblast loss led to an age-associated secretome profile, with 77% of identified proteins belonging to ECM and ECM-associated proteins. ECM not only contributes to skin mechanical properties, but it is also a reservoir of growth factors and bioactive molecules. We demonstrate that dermal fibroblast SLC3A2 is required for ECM to fully exert its structural and reservoir role allowing proper and efficient TGF-β localization and activation. We identified SLC3A2 as a protective controller of dermal ECM stiffness and quality required to maintain the epidermis to dermis interface as functional and dynamic.

Glut3 Addiction Is a Druggable Vulnerability for a Molecularly Defined Subpopulation of Glioblastoma

While molecular subtypes of glioblastoma (GBM) are defined using gene expression and mutation profiles, we identify a unique subpopulation based on addiction to the high-affinity glucose transporter, Glut3. Although Glut3 is a known driver of a cancer stem cell phenotype, direct targeting is complicated by its expression in neurons. Using established GBM lines and patient-derived stem cells, we identify a subset of tumors within the "proneural" and "classical" subtypes that are addicted to aberrant signaling from integrin αvβ3, which activates a PAK4-YAP/TAZ signaling axis to enhance Glut3 expression. This defined subpopulation of GBM is highly sensitive to agents that disrupt this pathway, including the integrin antagonist cilengitide, providing a targeted therapeutic strategy for this unique subset of GBM tumors.

Galectin-3, a Druggable Vulnerability for KRAS-Addicted Cancers

Identifying the molecular basis for cancer cell dependence on oncogenes such as KRAS can provide new opportunities to target these addictions. Here, we identify a novel role for the carbohydrate-binding protein galectin-3 as a lynchpin for KRAS dependence. By directly binding to the cell surface receptor integrin αvβ3, galectin-3 gives rise to KRAS addiction by enabling multiple functions of KRAS in anchorage-independent cells, including formation of macropinosomes that facilitate nutrient uptake and ability to maintain redox balance. Disrupting αvβ3/galectin-3 binding with a clinically active drug prevents their association with mutant KRAS, thereby suppressing macropinocytosis while increasing reactive oxygen species to eradicate αvβ3-expressing KRAS-mutant lung and pancreatic cancer patient-derived xenografts and spontaneous tumors in mice. Our work reveals galectin-3 as a druggable target for KRAS-addicted lung and pancreas cancers, and indicates integrin αvβ3 as a biomarker to identify susceptible tumors.Significance: There is a significant unmet need for therapies targeting KRAS-mutant cancers. Here, we identify integrin αvβ3 as a biomarker to identify mutant KRAS-addicted tumors that are highly sensitive to inhibition of galectin-3, a glycoprotein that binds to integrin αvβ3 to promote KRAS-mediated activation of AKT. Cancer Discov; 7(12); 1464-79. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 1355.

Abstract 3067: Galectin-3, a target for KRAS-addicted lung cancer

KRAS-mutant cancers are notoriously therapy-resistant. While responsible for oncogenesis, mutant KRAS or the sustained activation of KRAS-driven effectors may or may not be required throughout the course of cancer progression. Thus, understanding which tumors remain dependent on oncogenic KRAS could lead to the identification of unique vulnerabilities and opportunities to treat them. We previously discovered that the carbohydrate-binding Galectin-3 (Gal-3) brings together KRAS with integrin αvβ3 at the cell membrane in epithelial cancer cells to promote tumor progression. Here, we show that by directly binding to the cell surface receptor integrin αvβ3, Gal-3 drives addiction to oncogenic KRAS by enhancing macropinocytosis and reducing mitochondrial reactive oxygen species (ROS). This pathway drives increased expression of SOD2, a superoxide dismutase that clears mitochondrial ROS to protect against cell death. Targeting Gal-3 with a clinically active drug decreases macropinocytosis and increases ROS to eradicate KRAS-addicted lung cancer in patient-derived xenografts and spontaneous KRAS-driven lung cancer in mice. Our work reveals Gal-3 as a druggable target for KRAS-addicted lung cancer, and indicates integrin αvβ3 as a biomarker to identify this dependence.

Citation Format: Laetitia Seguin, Maria F. Camargo, Hiromi I. Wettersten, Shumei Kato, Tami von Schalscha, Kathryn C. Elliott, Sara M. Weis, David A. Cheresh. Galectin-3, a target for KRAS-addicted lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3067. doi:10.1158/1538-7445.AM2017-3067

Abstract 3966: Targeting integrin αvβ3-expressing cancer stem cells to manipulate tumor-associated macrophages

Tumor associated macrophages are involved in regulation of cancer growth and aggressiveness. Whereas M1 macrophages trigger an inflammatory response and inhibit tumor growth, M2 macrophages secrete pro-tumor cytokines into the microenvironment to support tumor progression. A macrophage switch from M1 to M2 has been associated with lung cancer progression, and cancer stem cells have been implicated as a driver of this reprogramming.

We recently reported that integrin αvβ3 expression is induced on lung adenocarcinoma cells during drug resistance and is both necessary and sufficient to reprogram these tumors to a stem-like state. Given the role that cancer stem cells play in switching M1 to M2 macrophages, we asked whether αvβ3 expression on lung adenocarcinoma cells account for this macrophage conversion. The M1/M2 macrophage ratio in αvβ3-positive tumors was markedly decreased relative to tumors lacking αvβ3. We next treated mice bearing αvβ3-positive tumors with a monoclonal antibody (LM609) targeting this receptor to assess its ability to alter the macrophage phenotype within these tumors. LM609 was able to selectively eliminate the αvβ3-positive cancer stem cells via antibody-dependent cell-mediated cytotoxicity (ADCC), and this not only increased the M1 macrophage population, but also markedly enhanced the sensitivity of these tumors to the effects of therapy.

These findings reveal that αvβ3-expressing cancer stem cells favor the pro-tumor M2 macrophage phenotype. Eliminating αvβ3-positive cancer stem cells via ADCC serves to both increase pro-inflammatory macrophages within the tumor microenvironment and prolong tumor sensitivity to therapy.

Citation Format: Hiromi I. Wettersten, Toshiyuki Minami, Megan M. Kaneda, Laetitia Seguin, Judith A. Varner, Sara M. Weis, David A. Cheresh. Targeting integrin αvβ3-expressing cancer stem cells to manipulate tumor-associated macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3966. doi:10.1158/1538-7445.AM2017-3966

Kinase-independent role for CRAF-driving tumour radioresistance via CHK2

Although oncology therapy regimens commonly include radiation and genotoxic drugs, tumour cells typically develop resistance to these interventions. Here we report that treatment of tumours with ionizing radiation or genotoxic drugs drives p21-activated kinase 1 (PAK1)-mediated phosphorylation of CRAF on Serine 338 (pS338) triggering a kinase-independent mechanism of DNA repair and therapeutic resistance. CRAF pS338 recruits CHK2, a cell cycle checkpoint kinase involved in DNA repair, and promotes CHK2 phosphorylation/activation to enhance the tumour cell DNA damage response. Accordingly, a phospho-mimetic mutant of CRAF (S338D) is sufficient to induce the CRAF/CHK2 association enhancing tumour radioresistance, while an allosteric CRAF inhibitor sensitizes tumour cells to ionizing radiation or genotoxic drugs. Our findings establish a role for CRAF in the DNA damage response that is independent from its canonical function as a kinase.

Tumors hijack cellular pathways to evade the effects of cancer therapy. Here, Advani et al. show that DNA damage-induced phosphorylation of CRAF Serine 338 triggers DNA repair by recruiting CHK2, highlighting a role for CRAF independent from its canonical function as a kinase.

Glioblastomas require integrin αvβ3/PAK4 signaling to escape senescence

Integrin αvβ3 has been implicated as a driver of aggressive and metastatic disease, and is upregulated during glioblastoma progression. Here, we demonstrate that integrin αvβ3 allows glioblastoma cells to counteract senescence through a novel tissue-specific effector mechanism involving recruitment and activation of the cytoskeletal regulatory kinase PAK4. Mechanistically, targeting either αvβ3 or PAK4 led to emergence of a p21-dependent, p53-independent cell senescence phenotype. Notably, glioblastoma cells did not exhibit a similar requirement for either other integrins or additional PAK family members. Moreover, αvβ3/PAK4 dependence was not found to be critical in epithelial cancers. Taken together, our findings established that glioblastomas are selectively addicted to this pathway as a strategy to evade oncogene-induced senescence, with implications that inhibiting the αvβ3-PAK4 signaling axis may offer novel therapeutic opportunities to target this aggressive cancer.

Variety in the tumor microenvironment: integrin splicing regulates stemness

Recently in Cell Reports, Goel et al. (2014) identified mechanisms underlying cellular heterogeneity in triple negative breast cancer. They find that expression of α6 integrin and its splice variants differs between epithelial and mesenchymal tumor cell subpopulations, the latter of which relies on VEGF signaling to promote cancer stem cell function.

Integrins and cancer: regulators of cancer stemness, metastasis, and drug resistance

Interactions between cancer cells and their surroundings can trigger essential signaling cues that determine cell fate and influence the evolution of the malignant phenotype. As the primary receptors involved in cell-matrix adhesion, integrins present on the surface of tumor and stromal cells have a profound impact on the ability to survive in specific locations, but in some cases, these receptors can also function in the absence of ligand binding to promote stemness and survival in the presence of environmental and therapeutic stresses. Understanding how integrin expression and function is regulated in this context will enable the development of new therapeutic approaches to sensitize tumors to therapy and suppress their metastatic phenotype.

Abstract 4240: Targeting Galectin-3 to reverse tumor stemness and drug resistance

We have recently linked integrin αvβ3 expression to metastatic potential, stemness, and therapy resistance due to its capacity to couple to KRAS. This leads to the induction of RalB/TBK-1 and the activation of NFκB to shift tumor cells to a stem-like phenotype. To understand how integrin αvβ3 couples to KRAS, we generated β3 domain swap mutants containing either the intracellular or extracellular domains of β1 integrin. Each chimera partially reduced KRAS association with αvβ3, suggesting interactions on each side of the plasma membrane may contribute. Since the short β3 cytoplasmic tail has no putative KRAS binding regions, we considered Galectin-3 as a putative scaffolding partner to facilitate the αvβ3/KRAS association due to its reported binding to both KRAS and integrins. Indeed, treating cells with GCS-100, a complex polysaccharide that has the ability to bind to and block the effects of Galectin-3, decreased Galectin-3 surface expression, αvβ3 clustering, and αvβ3/KRAS association. Exposing cells to this drug also decreased tumor stem properties. Our observations provide a molecular basis for the αvβ3/KRAS/Galectin-3 complex and highlight the potential for Galectin-3 blockade as a therapeutic approach to reverse the aggressive behavior of αvβ3-expressing tumors.

Citation Format: Shumei Kato, Laetitia Seguin, Aleksandra Franovic, Hisashi Kato, Maria Camargo, Jay Desgrosellier, Sudarshan Anand, Sara Weis, Sanford Shattil, David A. Cheresh. Targeting Galectin-3 to reverse tumor stemness and drug resistance. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4240. doi:10.1158/1538-7445.AM2014-4240

Abstract 3034: Integrin αvβ3 drives Slug activation and stemness in the pregnant and neoplastic mammary gland

While integrin αvβ3 expression is linked to breast cancer progression its role in epithelial development is unclear. Here, we show that αvβ3 plays a critical role in adult mammary stem cells (MaSCs) during pregnancy. While αvβ3 is a luminal progenitor marker in the virgin gland, we noted increased αvβ3 expression in MaSCs at mid-pregnancy. Accordingly, mice lacking αvβ3 or expressing a signaling deficient receptor showed defective mammary gland morphogenesis during pregnancy. This was associated with decreased MaSC expansion, clonogenicity and expression of Slug, a master regulator of MaSCs. Surprisingly, αvβ3 deficient mice displayed normal development of the virgin gland with no effect on luminal progenitors. TGFβ2, but not RANKL, induced αvβ3 leading to Slug nuclear accumulation and MaSC clonogenicity. In human breast cancer cells, αvβ3 was necessary and sufficient for Slug activation and tumorsphere formation. Thus, pregnancy-associated MaSCs require a TGFβ2/αvβ3/Slug pathway, which may also contribute to breast cancer progression.

Citation Format: Jay S. Desgrosellier, Jacqueline Lesperance, Laetitia Seguin, Sanford J. Shattil, David A. Cheresh. Integrin αvβ3 drives Slug activation and stemness in the pregnant and neoplastic mammary gland. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3034. doi:10.1158/1538-7445.AM2014-3034

An integrin β₃-KRAS-RalB complex drives tumour stemness and resistance to EGFR inhibition

Tumour cells, with stem-like properties, are highly aggressive and often show drug resistance. Here, we reveal that integrin α(v)β₃ serves as a marker of breast, lung and pancreatic carcinomas with stem-like properties that are highly resistant to receptor tyrosine kinase inhibitors such as erlotinib. This was observed in vitro and in mice bearing patient-derived tumour xenografts or in clinical specimens from lung cancer patients who had progressed on erlotinib. Mechanistically, α(v)β₃, in the unliganded state, recruits KRAS and RalB to the tumour cell plasma membrane, leading to the activation of TBK1 and NF-κB. In fact, α(v)β₃ expression and the resulting KRAS-RalB-NF-κB pathway were both necessary and sufficient for tumour initiation, anchorage independence, self-renewal and erlotinib resistance. Pharmacological targeting of this pathway with bortezomib reversed both tumour stemness and erlotinib resistance. These findings not only identify α(v)β₃ as a marker/driver of carcinoma stemness but also reveal a therapeutic strategy to sensitize such tumours to RTK inhibition.

Abstract A036: Integrin αvβ3 drives the mammary stem cell state during pregnancy

Epithelial stem/progenitor cell properties are associated with aggressive carcinomas. The integrin αvβ3 promotes tumor progression and metastasis in a diverse array of human carcinomas, and may be integral to epithelial stem/progenitor cell behavior. Here we reveal a critical role for αvβ3 in adult mammary stem cells (MaSCs) during pregnancy. While αvβ3 is a luminal progenitor marker in the virgin mammary gland, we noted a dramatic increase in αvβ3 expression in the MaSC pool at mid-pregnancy associated with enhanced repopulating potential. Similar to pregnancy, we noted that TGFβ, and not RANKL, was sufficient to drive αvβ3 expression enhancing MaSC activity. Accordingly, mice lacking β3 or expressing a signaling deficient form of this receptor showed defective mammary gland morphogenesis during pregnancy associated with decreased MaSC clonogenicity, expansion and outgrowth potential. Surprisingly, these mice displayed normal development of the virgin gland with no effect on luminal progenitors. These findings support a role for αvβ3 as a critical determinant of the MaSC state during pregnancy and suggest a related role for this receptor in regulating stem-like behavior in human breast cancers.

Citation Format: Jay Desgrosellier, Jacqueline Lesperance, Laetitia Seguin, Sanford Shattil, David Cheresh. Integrin αvβ3 drives the mammary stem cell state during pregnancy. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr A036.

Abstract C78: Integrin αvβ3 drives stemness in the pregnant and neoplastic mammary gland

Carcinoma cell expression of the integrin αvβ3 is associated with enhanced tumorigenicity and metastasis in a diverse array of human tumors. Here, we reveal αvβ3 expression in a subset of CD44+CD24-/low cancer stem cells in human breast tumor biopsies. In fact, αvβ3 is both necessary and sufficient to account for stem-like properties in breast tumor cells, suggesting that αvβ3 may contribute to mammary stem (MaSC)/progenitor cell behavior. While αvβ3 is a luminal progenitor marker in the virgin murine mammary gland, we noted a dramatic, but transient, increase in αvβ3 levels that defined the mammary stem cell pool at mid-pregnancy. Genetic deletion of β3 surprisingly had no effect on luminal progenitor behavior or ductal morphogenesis. In contrast, β3 was specifically required for MaSC clonogenicity and alveologenesis at mid-pregnancy, yet had no influence on MaSCs in the virgin gland. These findings reveal an unexpected role for αvβ3 in driving mammary stemness during pregnancy that may be related to the stem-like properties, and high metastatic potential associated with αvβ3 expression in human breast cancers.

Citation Format: Jay Desgrosellier, Jacqueline Lesperance, Laetitia Seguin, David Cheresh. Integrin αvβ3 drives stemness in the pregnant and neoplastic mammary gland. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C78.

A MEK-independent role for CRAF in mitosis and tumor progression

RAF kinases regulate cell proliferation and survival and can be dysregulated in tumors. The role of RAF in cell proliferation has been linked to its ability to activate mitogen-activated protein kinase kinase 1 (MEK) and mitogen-activated protein kinase 1 (ERK). Here we identify a MEK-independent role for RAF in tumor growth. Specifically, in mitotic cells, CRAF becomes phosphorylated on Ser338 and localizes to the mitotic spindle of proliferating tumor cells in vitro as well as in murine tumor models and in biopsies from individuals with cancer. Treatment of tumors with allosteric inhibitors, but not ATP-competitive RAF inhibitors, prevents CRAF phosphorylation on Ser338 and localization to the mitotic spindle and causes cell-cycle arrest at prometaphase. Furthermore, we identify phospho-Ser338 CRAF as a potential biomarker for tumor progression and a surrogate marker for allosteric RAF blockade. Mechanistically, CRAF, but not BRAF, associates with Aurora kinase A (Aurora-A) and Polo-like kinase 1 (Plk1) at the centrosomes and spindle poles during G2/M. Indeed, allosteric or genetic inhibition of phospho-Ser338 CRAF impairs Plk1 activation and accumulation at the kinetochores, causing prometaphase arrest, whereas a phospho-mimetic Ser338D CRAF mutant potentiates Plk1 activation, mitosis and tumor progression in mice. These findings show a previously undefined role for RAF in tumor progression beyond the RAF-MEK-ERK paradigm, opening new avenues for targeting RAF in cancer.

Abstract 2919: Unexpected role of CRAF in tumor cell mitosis revealed by an allosteric inhibitor

RAF kinases regulate fundamental cellular processes such as proliferation and survival and can be mutated or dysregulated in tumors. Although, RAF inhibitors show clinical activity in some cancer patients, recent reports have shown that ATP-competitive RAF inhibitors can enhance the proliferation of RAS driven tumors by promoting B- and CRAF dimerization and phosphorylation of CRAF on serine 338. Recently, we characterized an allosteric inhibitor of RAF that disrupts RAF dimerization, CRAF serine 338 phosphorylation and tumor growth in mice. Here, we report the surprising finding that phospho-S338 CRAF localizes to the mitotic spindle of proliferating tumor cells in vitro and in biopsies from cancer patients. Importantly, treatment of these cells with an allosteric, but not an ATP-competitive inhibitor of RAF, prevents CRAF localization to the mitotic spindle and causes cell cycle arrest at pro-metaphase in a MAPK-independent manner. Mechanistically, phospho-S338 CRAF interacts and co-localizes with active Polo-like kinase 1 (Plk1) at the mitotic spindle of proliferating cells. In fact, allosteric or genetic inhibition of CRAF inhibits Plk1 activity and its accumulation at the kinetochores causing pro-metaphase arrest. These findings define an unexpected role for RAF in mitosis, revealing a novel mechanism for RAF as a therapeutic target in oncology.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2919. doi:10.1158/1538-7445.AM2011-2919

The antidepressant agomelatine reduces fear long term memory but not acquisition or short term expression of fear memories

Alterations in fear learning processes may be implicated in mood disorders. Fear learning has been investigated with Pavlovian classical fear conditioning paradigms, consisting of pairing a neutral conditioned stimulus (CS), such as a tone, with an aversive unconditioned stimulus (US), such as a footshock. Upon subsequent exposure, the CS is perceived as aversive and provokes a fear response.The novel antidepressant agomelatine acts as a melatonergic receptor agonist and a 5-HT2C receptor antagonist. Its antidepressant action was demonstrated in preclinical and clinical studies. Agomelatine has also anxiolytic properties. The aim of this study was to determine how acute agomelatine treatment might differentially alter fear circuits by using auditory fear conditioning in the rat.A single pre-training injection of agomelatine (40 mg/kg intraperitoneally) significantly reduced freezing to the fear arousing CS 24 hours after training but not during training or 3 hours after training. This pattern of results is consistent with an effect on the consolidation of the fear memory. A single pre-testing injection of agomelatine had no effect on conditioned fear expression.

These effects of agomelatine should be considered in relation to its antidepressant action. Agomelatine achieved a reduction of fear conditioning in a single dose, while classical SSRIs only reduced fear conditioning after chronic treatment. This finding is consistent with clinical studies suggesting a faster onset of action of agomelatine than classical SSRI treatment.

Abstract 3841: An integrin αvβ3/c-Src oncogenic unit promotes anchorage independence and tumor progression

Integrins regulate adhesion-dependent growth, survival and invasion of tumor cells. In particular, expression of integrin αvβ3 is associated with progression of a variety of human tumors. We recently described an adhesion-independent role for integrin αvβ3 in pancreatic cancer and other carcinomas resulting in increased anchorage-independent tumor growth in vitro and lymph node metastases in vivo. These effects required recruitment of c-Src to the β3 integrin cytoplasmic tail, leading to c-Src activation. Pharmacological blockade of c-Src kinase activity with Dasatinib or genetic suppression of endogenous c-Src not only inhibited anchorage-independent growth, but also suppressed metastasis in vivo. We now show that αvβ3 exerts these effects through ligand-independent clustering of the integrin on the surface of non-adherent tumor cells. Self-assembly/clustering appears to be a unique property of αvβ3 relative to other integrins and is dependent on c-Src recruitment to αvβ3. These data describe a c-Src-dependent self-assembly property of αvβ3 leading to increased anchorage-independence and malignancy of tumor cells expressing this integrin. These findings also underscore the potential benefits of using Src inhibitors, such as Dasatinib, for treating patients with αvβ3-expressing solid tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3841.

CUX1 and E2F1 regulate coordinated expression of the mitotic complex genes Ect2, MgcRacGAP, and MKLP1 in S phase

Rho GTPases are critical for mitosis progression and completion of cytokinesis. During mitosis, the GDP/GTP cycle of Rho GTPases is regulated by the exchange factor Ect2 and the GTPase activating protein MgcRacGAP which associates with the kinesin MKLP1 in the centralspindlin complex. We report here that expression of Ect2, MgcRacGAP, and MKLP1 is tightly regulated during cell cycle progression. These three genes share similar cell cycle-related signatures within their promoter regions: (i) cell cycle gene homology region (CHR) sites located at -20 to +40 nucleotides of their transcription start sites that are required for repression in G(1), (ii) E2F binding elements, and (iii) tandem repeats of target sequences for the CUX1 transcription factor. CUX1 and E2F1 bind these three promoters upon S-phase entry, as demonstrated by chromatin immunoprecipitation, and regulate transcription of these genes, as established using promoter-luciferase reporter constructs and expression of activated or dominant negative transcription factors. Overexpression of either E2F1 or CUX1 increased the levels of the endogenous proteins whereas small interfering RNA knockdown of E2F1 or use of a dominant negative E2F1 reduced their expression levels. Thus, CUX1, E2F, and CHR elements provide the transcriptional controls that coordinate induction of Ect2, MgcRacGAP, and MKLP1 in S phase, leading to peak expression of these interacting proteins in G(2)/M, at the time they are required to regulate cytokinesis.

Regulation of Rho signaling pathways in interleukin-2-stimulated human T-lymphocytes

Rho GTPases are key regulators of many cellular functions, including cytoskeleton organization which is important for cell morphology and mobility, gene expression, cell cycle progression, and cytokinesis. In addition, it has recently been recognized that Rho GTPase activity is required for development of the immune system, as well as for the specialized functions of the peripheral cells that act in the immune response such as antigen presenting cells and lymphocytes. Stimulation of T lymphocytes with interleukin-2 (IL-2) induces clonal expansion of antigen-specific populations and provides a model to study cell cycle entry and cell cycle progression. We have performed gene expression analysis in a model of human T lymphocytes, which proliferate in response to IL-2. In addition to changes in genes relevant to cell cycling and to the antiapoptotic effects of IL-2, we have analyzed expression and variations of more than 300 genes involved in Rho GTPase signaling pathways. We report here that IL-2 regulates the expression of a number of proteins, which participate in the Rho GTPase pathways, including some of the GTPases themselves, GDP/GTP exchange factors, GTPase activating proteins, as well as GDIs and effectors. Our results suggest that regulation of expression of components of the Rho GTPase pathways may be an important mechanism in assembling specific signal transduction cascades that need to be active at certain times during the cell cycle. Some of our findings may also be relevant to the roles of Rho GTPases in T lymphocyte functions and proliferation.

The role of dopamine D3 compared with D2 receptors in the control of locomotor activity: a combined behavioural and neurochemical analysis with novel, selective antagonists in rats

BACKGROUND

The role of dopamine D(3)/D(2) receptors in the control of locomotion is poorly understood.

OBJECTIVES

To examine the influence of selective antagonists at D(3) or D(2) receptors on locomotion in rats, alone and in interaction with the preferential D(3) versus D(2) receptor agonist, PD128,907.

METHODS

Affinities of ligands at rat D(2) and cloned, human hD(3), hD(2S), hD(2L) and hD(4) sites were determined by standard procedures. Locomotion was monitored automatically in rats pre-habituated for 30 min to an open-field environment. Extracellular levels of dopamine (DA) were determined by dialysis in the nucleus accumbens and striatum. Drugs were given acutely via the systemic route.

RESULTS

PD128,907, which preferentially recognised D(3) versus D(2) sites, biphasically reduced and enhanced locomotion at "low" (0.01-0.63 mg/kg) and "high" (2.5-10 mg/kg) doses, respectively. L741,626 and S23199, which behaved as preferential D(2) versus D(3) receptor antagonists, enhanced the reduction in locomotion evoked by the low dose of PD128,907, blocked the increase provoked by the high dose and suppressed spontaneous locomotion alone. Analogous findings were obtained with haloperidol and raclopride which showed equilibrated affinity at D(2) and D(3) receptors. UH232 and AJ76, which showed a mild preference for D(3) versus D(2) sites, did not modify the effect of a low dose of PD128,907, slightly enhanced the hyperlocomotion elicited by the high dose and exerted little influence on locomotion alone. S14297 and U99194, which acted as preferential D(3) versus D(2) receptor antagonists, abolished the reduction in locomotion elicited by a low dose of PD128,907, potentiated the induction of locomotion by a high dose, and failed to influence locomotion alone. The actions of S14297 were stereoselective inasmuch as they were mimicked by the racemic form, S11566, but not by the inactive enantiomer, S17777. In contrast to S14297, S11566 and U99194, however, S33084, SB269,652, GR218,231 and N-[-4-['-(1-naphtyl)piperazine-1-yl]butyl] anthracene-2-carboxamide ("NGB-1"), highly selective D(3) versus D(2) receptor antagonists, were inactive under all conditions. PD128,907 (0.01-10.0 mg/kg) suppressed dialysate levels of DA in the nucleus accumbens and striatum, actions blocked by L741,626 and haloperidol, yet unaffected by S14297 and S33084.

CONCLUSIONS

The facilitatory influence of a "high" dose of PD128,907 upon locomotion is mediated by postsynaptic D(2) receptors and, possibly, countered by their D(3) counterparts. Correspondingly, selective blockade of D(2) but not of D(3) receptors alone suppresses motor function. The reduction in locomotion provoked by a "low" dose of PD128,907 may be mediated by D(2) autoreceptors, but a role of postsynaptic D(3) receptors cannot be excluded. Finally, mechanisms underlying the contrasting influence of chemically diverse D(3) receptor antagonists upon locomotion remain to be elucidated.

Metabolic and anti-atherogenic effects of long-term benfluorex in dyslipidemic insulin-resistant sand rats (Psammomys obesus)

Benfluorex is a clinical lipid-lowering agent with antihyperglycemic properties. The effect of long-term oral treatment (10 mg/kg/day for 7.5 months) on carbohydrate and lipid metabolism and aortic morphology was investigated in 24 insulin-resistant sand rats receiving a standard laboratory diet supplemented with cholesterol (2%). Untreated controls (n=34) developed impaired glucose tolerance, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia and elevated plasma LDL- and VLDL-cholesterol, positively correlated with the proportion of the thoracic aorta displaying oil red O-positive atherosclerosis; ultrastructural examination showed intimal lipid deposits, foam cells, polymorph infiltrates and fibrosis. Benfluorex-treated animals showed significant decreases in glucose intolerance, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia, and plasma LDL- and VLDL-cholesterol, with no evidence of aortic atheroma. The metabolic benefits of benfluorex may protect against the long-term development of atherosclerosis in the insulin-resistant dyslipidemic syndrome.

Effects of moderate and intensive training on functional activity of central 5-HT1B receptors in the rat substantia nigra

The efficacy of the selective 5-HT1B receptor agonist CP 93,129 in inhibiting the forskolin-stimulated adenylyl cyclase activity in the rat substantia nigra was reduced by both moderate and intensive prolonged training compared with sedentary resting rats. The concentration-response curves of the agonist were shifted to the right with a sixfold increase of the half-maximal inhibitory concentration. A difference was observed between the two training exercises in regard to further changes in 5-HT1B receptor sensitivity induced by an acute restraint stress. This manipulation did not affect the functional response of the 5-HT1B receptors further in moderately trained rats, whereas an additional desensitization of the 5-HT1B receptors was observed in intensively trained rats. These results strongly suggest the existence of regulation mechanisms altering the functional efficacy of 5-HT1B receptors and, accordingly, affecting the serotonergic activity, since 5-HT1B receptors modulate the neuronal release of the amine.

The endogenous cerebral tetrapeptide 5-HT-moduline reduces in vivo the functional activity of central 5-HT1B receptors in the rat

5-HT-moduline (Leu-Ser-Ala-Leu, LSAL) is a novel endogenous peptide isolated from rat brain which interacts in vitro specifically with 5-HT(1B) receptors by a non-competitive mechanism. In the present study, we demonstrate that the efficacy of the selective 5-HT(1B) receptor agonist CP 93 129 in inhibiting the forskolin-stimulated adenylyl cyclase activity in the rat substantia nigra was reduced 15 min after intracerebral injection of LSAL compared to vehicle or ALLS (scrambled peptide) injected rats. Accordingly, the concentration-response curve of the agonist is shifted to the right with a 3.5-fold increase of the half-maximal inhibitory concentration compared to vehicle injected rats. Thus, the in vivo desensitization of serotonergic autoreceptors strongly strengthens the important role of 5-HT-moduline in the rapid adaptative control of the serotonergic system, implicated in numerous pathological events as anxiety and depression.

5-hydroxytryptamine-moduline, a new endogenous cerebral peptide, controls the serotonergic activity via its specific interaction with 5-hydroxytryptamine1B/1D receptors

The serotonergic system controls the activity of neurotransmissions involved in numerous physiological functions. It is also thought to be crucially implicated in various pathologies, including psychiatric disorders such as depression, anxiety, and aggressiveness. The properties of 5-hydroxytryptamine (5-HT)-moduline, a novel endogenous peptide, have been tested in vitro and in vivo. Binding studies have shown that the peptide specifically interacts with 5-HT1B/1D receptors via a noncompetitive mechanism corresponding to a high apparent affinity (EC50 = 10(10) M). The interaction was shown in rat and guinea pig brain tissues and in cells transfected with either 5-HT1B or 5-HT1D beta receptor gene. [3H]5-HT-moduline binds to a single population of sites in mammalian brain (Kd = 0.4 nM in rat, Kd = 0.8 nM in guinea pig) as well as in transfected cells expressing the 5-HT1B or the 5-HT1D beta receptors (Kd = 0.2 and 0.6 nM, respectively). Furthermore, the binding is clearly specific of the LSAL sequence. Autoradiographic studies showed an heterogeneous brain distribution of this site. The interaction of 5-HT-moduline with the 5-HT1B/1D receptor corresponds to a decrease in the functional activity of the receptor (i.e., a decrease in the inhibitory effect of a 5-HT1B agonist on the evoked release of [3H]5-HT from synaptosomal preparation). It was also shown that 5-HT-moduline possess an in vivo effect in the social interaction test in mouse. Finally, it was demonstrated that 5-HT-moduline was released from brain synaptosomal preparation by a K+/Ca(2+)-dependent mechanism. In conclusion, 5-HT-moduline is a novel endogenous peptide regulating the serotonergic activity via a direct action at presynaptic 5-HT receptor. It may play an important role in the physiological mechanisms involving the serotonergic system, particularly in mechanisms corresponding to the elaboration of an appropriate response of the central nervous system to a given stimulus.

Sub-chronic cold stress reduces 5-HT1A receptor responsiveness in the old but not in the young rat

The inhibitory effect of the prototypical 5-hydroxytryptamine (5-HT)1A receptor agonist 8-hydroxy-2-(di-n-propyl amino)tetraline (8-OH-DPAT) on forskolin-stimulated adenylyl cyclase activity, has been examined as an index of the functional activity of 5-HT1A receptors in the hippocampus of young (3 months) and old (18 months) rats exposed during 24 h or 5 days to cold. In both young and old rats exposed to cold stress during 24 h, there was a reduction in the potency (EC50) and/or the maximal inhibitory effect (Emax) of 8-OH-DPAT in reducing forskolin-induced cAMP accumulation. The properties of the hippocampal 5-HT1A sites labelled by [3H]8-OH-DPAT were not affected by these stressful conditions. Moreover, while the sensitivity of 5-HT1A receptors to 8-OH-DPAT in young rats returned to control values after 5 days of cold exposure, old rats still exhibited a significant desensitization of 5-HT1A receptors as compared to naive animals. These results point out the capacity of young but not of old rats to adapt to the aversive effects of a subchronic stressor.

Effects of stress on the functional properties of pre- and postsynaptic 5-HT1B receptors in the rat brain

Numerous studies have clearly shown that the turnover and release of serotonin (5-hydroxytryptamine, 5-HT) are increased under acute stressful conditions. Inasmuch as this latter process is under the control of a feedback mechanism involving the stimulation of presynaptic 5-HT1B autoreceptors, we have investigated the possible effects of acute restraint (40 min) on the functional properties of 5-HT1B receptors. The efficacy of the selective 5-HT1B receptor agonist 3-[1,2,5,6-tetrahydropyrid-4-yl]pyrrolo-[3,2-b]pyrid-5-one (CP-93,129) in inhibiting in vitro the K+-evoked release of [3H]5-HT, was significantly reduced in stressed rats as compared to naive animals. Similarly, the responsiveness of 5-HT1B receptors inhibiting the release of [3H]acetylcholine (presynaptic 5-HT1B heteroreceptors), was reduced by restraint. These effects were observed in the hippocampus, but using the inhibitory effect of CP-93,129 on forskolin-stimulated adenylyl cyclase activity as an index of 5-HT1B receptor function, it could be shown that the 5-HT1B receptors located in the substantia nigra are also desensitized by stress. The number as well as the apparent affinity constant of 5-HT1B binding sites labelled by [125I]iodocyanopindolol, as measured by quantitative autoradiography and membrane binding, were similar in naive and restraint-stressed rats suggesting that the stress-induced desensitization of 5-HT1B receptors is not due to a reduced number of 5-HT1B binding sites. As stress is thought to be a causal factor for the etiology of anxiety and depression, these results support the potential involvement of 5-HT1B receptor dysfunction in the development of these neurological disorders.

Pro- and antinociceptive actions of serotonin (5-HT)1A agonists and antagonists in rodents: relationship to algesiometric paradigm

In mice injected with formalin into the hindpaw, the 5-HT1A receptor agonists, 8-OH-DPAT and flesinoxan, equipotently inhibited the early phase (EP) and late phase (LP) of licking. At higher doses, they provoked ataxia and inhibited the writhing elicited by intra-abdominal acetic acid. The antagonists, (-)-alprenolol, (-)-tertatolol, WAY-100,135 and S 15931 were more potent against the LP than the EP. They also inhibited writhing, and only at very high doses did they elicit ataxia. In rats, 8-OH-DPAT and flesinoxan increased the current required to elicit vocalisation upon electrical stimulation of the tail. The action of 8-OH-DPAT was blocked by WAY-100,135, which, like other antagonists, was inactive alone. Interestingly, a low dose of 8-OH-DPAT partially inhibited the antinociceptive action of the mu-opioid agonist, morphine, the action of which was dose-dependently facilitated by (-)-alprenolol and S 15931. Administered s.c., 8-OH-DPAT elicited spontaneous tail-flicks (STFs) in rats: these were abolished by WAY-100,135, (-)-tertatolol, (-)-alprenolol and S 15931. STFs were also eliminated by s.c. or i.t. administration of the alpha 2-adrenergic receptor agonist, clonidine, the GABAA agonist, muscimol or the GABAB agonist, baclofen. The mu-opioid, morphine, blocked STFs only at high doses and the kappa-opioid agonists, U 50,488 and U 69,593, even at supra-ataxic doses, were inactive. Antagonists at neurokinin (NK)1 (RP 67580), NK2 (SR 48,968) and bradykinin (BK)2 (Hoe 140) receptors, as well as aspirin, did not block STFs, though indomethacin was effective. Antagonists at the glycine B site coupled to the NMDA receptor, L 687,414, L 701,324 and (+)-HA966, blocked STFs. Furthermore, (+)-HA 966 and the competitive NMDA receptor antagonist, CPP, were active upon i.t. administration. STFs were also blocked by s.c. or i.t. administration of the AMPA antagonists, YM 900 and NBQX. In conclusion, the influence of 5-HT1A ligands upon nociception is dependent upon the algesiometric paradigm. Intriguingly, modulation of 5-HT1A receptor-mediated STFs reveals parallels to neuropathic pain.

[Social support network evolution after the birth of their first baby: comparison between lower and middle class mothers]

The social support networks of a group of low socio-economic status (S.E.S.) mothers (n = 87) and a group of higher S.E.S. mothers (n = 44) are described and compared at the 30th week of pregnancy and at the third week after the birth of their first baby. The evolution of the support networks for these two groups of mothers during this period is also examined. A modified form of the ASSIS from Barrera has been used to measure the social support network. Results show that, during pregnancy, the social support network of low-S.E.S. mothers is more restricted than that of higher S.E.S. mothers. Although the actual number of people around them after the birth of the baby did not increase, low-S.E.S. mothers said they felt a slight increase in the number of people available to give support in some way. They also reported that conflicts were more frequent with some of them. For higher S.E.S. mothers, all social network variables remained stable from pregnancy through the first postpartum month.

Antinociceptive profiles of non-peptidergic neurokinin1 and neurokinin2 receptor antagonists: a comparison to other classes of antinociceptive agent

This study compared the antinociceptive properties of systemic administration of selective, non-peptidergic antagonists at neurokinin (NK1 and NK2) receptors to those of other classes of antinociceptive agent. (All doses are in mg/kg.) In mice, the NK1 antagonist, CP 99,994, preferentially (inhibitory dose50 (ID50) = 4.4) inhibited the late phase (LP) as compared to the early phase (EP) (16.1) of formalin-induced licking (FIL). A high dose (17.6) elicited ataxia in the rotarod test. Acetic acid-induced writhing was reduced at intermediate doses (10.0) whereas the tail-flick (TF) response to thermal and mechanical stimuli was inhibited only at high doses (22.7 and 17.7, respectively). Modulation of stimulus intensity did not modify the influence of CP 99,994 upon the response to heat. A similar pattern of data was acquired with RP 67,580, although this NK1 antagonist more potently inhibited writhing (2.8). In contrast, RP 68,651, the inactive isomer of RP 67,580, neither reduced the LP of FIL nor modified writhing indicating that these actions of RP 67,580 were stereospecific. Three further NK1 antagonists, SR 140,333, WIN 51,708 and WIN 62,577, likewise inhibited the LP of FIL and failed to modify the TF response at non-ataxic doses. Further, SR 140,333 (0.5) and WIN 51,708 (1.4) were potent ligands in the writhing procedure. The NK2 antagonist, SR 48,966, mimicked NK1 antagonists in preferentially inhibiting the LP (7.7) as compared to the EP (26.9) of FIL. Further, only at doses higher than those evoking ataxia (20.9) did SR 48,968 modify the TF response (36.5 and 32.0 for heat and pressure, respectively). However, it differed to NK1 antagonists in being inactive in the writhing test (> 40.0). In comparison to these NK1 and NK2 antagonists, the mu-opioid agonists (morphine and fentanyl) and kappa-opioid agonists (enadoline and U 69,593) equipotently inhibited all nociceptive responses at doses not provoking ataxia. While the glycine B receptor partial agonist, (+)-HA 966, selectively blocked the LP of FIL and did not evoke ataxia, the NMDA receptor channel blocker, (+)-MK 801, elicited antinociception only at doses close to those provoking ataxia. Finally, the NSAIDs, indomethacin and ibuprofen, the BK2 antagonist, Hoe 140 and the nitric oxide synthase (NOS) inhibitors, L-NAME and 7 nitroindazole, inhibited the LP (but not the EP) of FIL and (except for L-NAME) also reduced writhing: in contrast, they did not evoke ataxia and were inactive in the TF procedures.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemically-diverse ligands at the glycine B site coupled to N-methyl-D-aspartate (NMDA) receptors selectively block the late phase of formalin-induced pain in mice

The glycine B receptor partial agonists L 687,414, D-cycloserine and (+)-HA 966, and the glycine B receptor antagonists MDL 29,951 and 5,7-dichloro-2,4 dihydroxy-3-phenyl-quinoline dione (DCPQ) dose-dependently inhibited the late phase (LP) of formalin-induced licking (FIL) elicited by intraplantar formalin in mice at doses exerting little motor disruption in the rotarod test. In distinction, the early phase (EP) of FIL and the writhing response to intra-abdominal acetic acid were little influenced and, irrespective of stimulus intensity, they failed to modify the tail-flick response to phasic, thermal or mechanical stimulation of the tail. In contrast to glycine B ligands, competitive antagonists at the NMDA receptor recognition site (CPP, CGS 19755, CGP 34879 and 39551) and blockers of the associated ion channel ((+)-MK 801, (-)-MK 801, memantine and ketamine) all blocked both the LP and EP of FIL and induced ataxia at comparable doses. In conclusion, normalization of transmission at NMDA receptors by inhibition of the coupled glycine B site preferentially elicits antinociception against prolonged (chemical) noxious stimulation in the absence of a marked influence upon motor coordination.

The glycine B receptor partial agonist, (+)-HA966, enhances induction of antinociception by RP 67580 and CP-99,994

The tachykinin receptor antagonists (3aR,7aR)-7,7-diphenyl-2(1-imino-2-(2-methoxyphenyl/ethyl)++ +perhydroisoindole) (RP 67580) and (+)-(2S-3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994), which act selectively at neurokinin (NK)1 receptors, inhibited the early phase of formalin-induced pain in mice. Although (+)-(1-hydroxy-3-aminopyrrolidine-2-one) ((+)-HA966), a partial agonist at glycine B receptors, was inactive alone, it potentiated the actions of RP 67580 (but not its inactive stereoisomer, RP68651) and CP-99,994. In its presence, the dose-response curve for RP 67580 was dose-dependently shifted to the left. In contrast, (+)-HA966 did not modify the induction of ataxia by RP 67580 and CP-99,994. These data suggest that co-administration of partial agonists at glycine B receptors may improve the antinociceptive potency and 'therapeutic window' of tachykinin NK1 receptor antagonists.

(+)-HA 966, a partial agonist at the glycine site coupled to NMDA receptors, blocks formalin-induced pain in mice

(+)-(1-Hydroxy-3-aminopyrrolidine-2-one) ((+)-HA 966), a partial agonist at the glycine site coupled to N-methyl-D-aspartic acid (NMDA) receptors, abolished the late phase of licking induced by injection of formalin into the hind-paw of mice; inhibitory dose50 (ID50) = 1.6 mg/kg, s.c. In contrast, it was weakly active against the first phase; ID50 = 33.3 mg/kg, s.c. Further, (+)-HA 966 was inactive in the rotarod test of ataxia. These data support a role of NMDA receptors in the transmission of prolonged noxious stimulation and suggest that partial glycine receptor agonists may exert antinociceptive properties against persistent pain.

Effects of nucleotides on [3H]bradykinin binding in guinea pig: further evidence for multiple B2 receptor subtypes

We have suggested recently the existence of three subtypes of B2 bradykinin receptors in tissues of guinea pigs. We have classified these B2 bradykinin receptors into B2a, B2b, and B2c subtypes depending on their affinity for various bradykinin antagonists. Because the actions of bradykinin in different cell systems appear to be both dependent on and independent of G proteins, we sought to determine whether the binding of [3H]bradykinin to the B2 subtypes is sensitive to guanine nucleotides and, therefore, possibly coupled to G proteins. In the ileum, where we have demonstrated B2a and B2b subtypes, specific [3H]bradykinin binding was reduced with GDP (100 microM) and the nonmetabolized analogue of GTP, guanyl-5'-yl-imidodiphosphate (GppNHp; 100 microM). Competition studies with bradykinin and with [Hyp3]bradykinin, which shows approximately 20-fold greater selectivity for the B2a subtype than bradykinin, were performed in the presence or absence of GppNHp (100 microM). The competition experiments demonstrated that binding to the B2a subtype, which has higher affinity for [Hyp3]bradykinin and bradykinin than the B2b subtype, was lost in the presence of GppNHp, whereas binding to the B2b subtype was unaffected. In contrast, GppNHp (100 microM) and GDP (100 microM) failed to alter specific [3H]bradykinin binding to B2b and B2c subtypes in lung. [3H]Bradykinin binding was unaffected by AMP, ADP, ATP, and GMP (100 microM each). Based on this evidence, we suggest that the B2a bradykinin subtype is coupled to G proteins. The B2b and B2c subtypes are either not coupled to G proteins, or may be coupled to the Go-type GTP binding proteins, which have been suggested to be less sensitive to guanine nucleotides.(ABSTRACT TRUNCATED AT 250 WORDS)