RAS Regulates the Transition from Naive to Primed Pluripotent Stem Cells.

The transition from naive to primed state of pluripotent stem cells is hallmarked by epithelial-mesenchymal transition, metabolic switch from oxidative phosphorylation to aerobic glycolysis, and changes in the epigenetic landscape. Since these changes are also seen as putative hallmarks of neoplastic cell transformation, we hypothesized that oncogenic pathways may be involved in this process. We report that the activity of RAS is repressed in the naive state of mouse embryonic stem cells (ESCs) and that all three RAS isoforms are significantly activated upon early differentiation induced by LIF withdrawal, embryoid body formation, or transition to the primed state.

Novel LIMK2 Inhibitor Blocks Panc-1 Tumor Growth in a mouse xenograft model.

LIM kinases (LIMKs) are important cell cytoskeleton regulators that play a prominent role in cancer manifestation and neuronal diseases. The LIMK family consists of two homologues, LIMK1 and LIMK2, which differ from one another in expression profile, intercellular localization, and function. The main substrate of LIMK is cofilin, a member of the actin-depolymerizing factor (ADF) protein family.

Interplay Between HGF/SF-Met-Ras Signaling, Tumor Metabolism and Blood Flow as a Potential Target for Breast Cancer Therapy.

High glucose uptake and increase blood flow is a characteristic of most metastatic tumors. Activation of Ras signaling increases glycolytic flux into lactate, de novo nucleic acid synthesis and uncoupling of ATP synthase from the proton gradient. Met tyrosine kinase receptor signaling upon activation by its ligand, hepatocyte growth factor/scatter factor (HGF/SF), increases glycolysis, oxidative phosporylation, oxygen consumption, and tumor blood volume.

Vitamin D and S-farnesylthiosalicylic acid have a synergistic effect on hepatic stellate cells proliferation.

Background: Hepatic stellate cells (HSCs) have a key role in the formation of hepatic fibrosis. The active form of vitamin D, 1,25(OH)2D3, has been found to have antiproliferative and antifibrotic effects in various tissues including liver. Farnesylthiosalicylic acid (FTS), a novel Ras antagonist, was also found to inhibit hepatic fibrosis.

Chloroquine synergizes with FTS to enhance cell growth inhibition and cell death.

The Ras family of small GTPases transmits extracellular signals that regulate cell growth, differentiation, motility and death. Ras signaling is constitutively active in a large number of human cancers. Ras can also regulate autophagy by affecting several signaling pathways including the mTOR pathway.

Growth of poorly differentiated endometrial carcinoma is inhibited by combined action of medroxyprogesterone acetate and the Ras inhibitor Salirasib.

Type 2 endometrial carcinoma (EC) is a poorly differentiated EC. Unlike type 1 EC, which responds to hormonal treatment (progestins), type 2 EC is refractory to hormonal treatment because of its low expression of active estrogen and progesterone receptors (ER, PR). The aim of this study was to develop a novel drug combination designed to treat these aggressive type 2 EC tumors without surgery and with fertility potential preserved.

Ras chaperones: new targets for cancer and immunotherapy.

The Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS, Salirasib®) interferes with Ras membrane interactions that are crucial for Ras-dependent signaling and cellular transformation. FTS had been successfully evaluated in clinical trials of cancer patients. Interestingly, its effect is mediated by targeting Ras chaperones that serve as key coordinators for Ras proper folding and delivery, thus offering a novel target for cancer therapy.

Computer-based identification of a novel LIMK1/2 inhibitor that synergizes with salirasib to destabilize the actin cytoskeleton.

Neurofibromin regulates cell motility via three distinct GTPase pathways acting through two different domains, the Ras GTPase-activating protein-related domain (GRD) and the pre-GRD domain. First, the GRD domain inhibits Ras-dependent changes in cell motility through the mitogen activated protein cascade. Second, it also regulates Rho-dependent (Ras-independent) changes by activating LIM kinase 2 (LIMK2), an enzyme that phosphorylates and inactivates cofilin (an actin-depolymerizing factor).

Prevention of induced colitis in mice by the ras antagonist farnesylthiosalicylic acid.

Background: Ras proteins are crucial for cell differentiation and proliferation. Targeting Ras with farnesylthiosalicylic acid (FTS), a Ras antagonist, has been suggested as a therapeutic strategy in proliferative and inflammatory diseases.

Aims: To examine the role of Ras and the therapeutic potential of FTS in experimental colitis.

Inhibition of contact sensitivity by farnesylthiosalicylic acid-amide, a potential Rap1 inhibitor.

We hypothesized that Ras proximate 1 (Rap1) functions as an additional target for farnesylthiosalicylic acid (FTS) or its derivatives, and that the inhibition of Rap1 in lymphocytes by these agents may represent a method for treating inflammatory disorders. Indeed, we found that FTS-amide (FTS-A) was able to inhibit the elicitation phase of delayed cutaneous hypersensitivity in vivo. This effect was associated with the inhibition of Rap1 more than with the inhibition of Harvey rat sarcoma viral oncogene (Ras).

Farnesylthiosalicylic acid (salirasib) inhibits Rheb in TSC2-null ELT3 cells: a potential treatment for lymphangioleiomyomatosis.

The small GTPase proteins, Ras and Rheb, serve as molecular switches regulating cell proliferation, differentiation and apoptosis. Ras also regulates Rheb by inactivating the tuberous sclerosis complex (TSC), which includes products of the TSC1 and TSC2 genes encoding hamartin (TSC1) and tuberin (TSC2), respectively, and acts as a Rheb-specific GTPase-activating protein. Loss of function of TSC1 or TSC2 results in an increase in active Rheb.

The Ras antagonist, farnesylthiosalicylic acid (FTS), decreases fibrosis and improves muscle strength in dy/dy mouse model of muscular dystrophy.

The Ras superfamily of guanosine-triphosphate (GTP)-binding proteins regulates a diverse spectrum of intracellular processes involved in inflammation and fibrosis. Farnesythiosalicylic acid (FTS) is a unique and potent Ras inhibitor which decreased inflammation and fibrosis in experimentally induced liver cirrhosis and ameliorated inflammatory processes in systemic lupus erythematosus, neuritis and nephritis animal models. FTS effect on Ras expression and activity, muscle strength and fibrosis was evaluated in the dy(2J)/dy(2J) mouse model of merosin deficient congenital muscular dystrophy.

Oncogenic synergism between ErbB1, nucleolin, and mutant Ras.

Alterations in the ErbB family of growth factor receptors, their signaling components, and mutational activation of Ras proteins are major contributors to malignant transformation. Recently, mutant Ras was shown to be capable of activating ErbB receptors in a ligand-independent manner. Furthermore, it was observed that nucleolin, a transcriptional regulator and ribosome biogenesis factor, can bind both K-Ras and the cytoplasmic tail of ErbB receptors to enhance ErbB receptor activation.

H-Ras nanocluster stability regulates the magnitude of MAPK signal output.

H-Ras is a binary switch that is activated by multiple co-factors and triggers several key cellular pathways one of which is MAPK. The specificity and magnitude of downstream activation is achieved by the spatio-temporal organization of the active H-Ras in the plasma membrane. Upon activation, the GTP bound H-Ras binds to Galectin-1 (Gal-1) and becomes transiently immobilized in short-lived nanoclusters on the plasma membrane from which the signal is propagated to Raf.

Composite fiber structures with antiproliferative agents exhibit advantageous drug delivery and cell growth inhibition in vitro.

Composite core/shell fiber structures loaded with the antiproliferative drugs paclitaxel or farnesylthiosalicylate (FTS) were developed and studied. The latter is a specific nontoxic Ras inhibitor with a mild hydrophobic nature, which can also be used for local cancer treatment and stent applications. The fibers were composed of a dense polyglyconate core and a porous drug-loaded poly(D,L-lactic-glycolic acid) shell, prepared using freeze drying of inverted emulsions.

Rasosomes spread Ras signals from plasma membrane 'hotspots'.

Ras proteins regulate cell growth, differentiation, and apoptosis from various cellular platforms. We have recently identified a novel potential signaling platform, the rasosome, which moves rapidly near the plasma membrane (PM) and in the cytosol, carrying multiple copies of palmitoylated Ras proteins. In the present study we demonstrate that rasosomes are unique entities distinct from PM nanoclusters or from endocytotic compartments.

New derivatives of farnesylthiosalicylic acid (salirasib) for cancer treatment: farnesylthiosalicylamide inhibits tumor growth in nude mice models.

The Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS, Salirasib) interferes with Ras membrane interactions that are crucial for Ras-dependent transformation. It remains unknown whether modifications of the carboxyl group of FTS can affect its activity. Here we show that specific modifications of the FTS carboxyl group by esterification or amidation yield compounds with improved growth inhibitory activity, compared to FTS, as shown in Panc-1 and U87 cells.

The Ras inhibitor farnesylthiosalicylic acid (Salirasib) disrupts the spatiotemporal localization of active Ras: a potential treatment for cancer.

Chronic activation of Ras proteins by mutational activation or by growth factor stimulation is a common occurrence in many human cancers and was shown to induce and be required for tumor growth. Even if additional genetic defects are present, "correction" of the Ras defect has been shown to reverse Ras-dependent tumorigenesis. One way to block Ras protein activity is by interfering with their spatiotemporal localization in cellular membranes or in membrane microdomains, a prerequisite for Ras signaling and biological activity.

Orally administered FTS (salirasib) inhibits human pancreatic tumor growth in nude mice.

Background: S-trans,trans-farnesylthiosalicylic acid (salirasib, FTS) is a synthetic small molecule that acts as a potent Ras inhibitor. Salirasib inhibits specifically both oncogenically activated Ras and growth factor receptor-mediated Ras activation, resulting in the inhibition of Ras-dependent tumor growth. The objectives of this study were to develop a sensitive LC-MS/MS assay for determination of FTS in plasma, to assess the bioavailabilty of FTS after oral administration to mice, and then to examine the efficacy of orally administered FTS for inhibition of tumor growth in a nude mouse model.

Custom-designed wells and flow chamber for exposing air-liquid interface cultures to wall shear stress.

The effects of mechanical stimuli such as wall shear stresses (WSS) on cellular processes have been studied in vitro in numerous cell types. In order to study WSS effects on cells cultured under air-liquid interface (ALI) conditions, we developed a custom-designed well that can be disassembled into sub-units that allow installation of the cultured cells in a flow chamber, and then, re-assembled for further incubation or biological tests. Human nasal epithelial cells were cultured in the new wells under ALI conditions, and some of their biological characteristics were compared with those cultured in commercial Millicells.

Spatiotemporal organization of Ras signaling: rasosomes and the galectin switch.

1. Ras signaling and oncogenesis depend on the dynamic interplay of Ras with distinctive plasma membrane (PM) microdomains and various intracellular compartments. Such interaction is dictated by individual elements in the carboxy-terminal domain of the Ras proteins, including a farnesyl isoprenoid group, sequences in the hypervariable region (hvr)-linker, and palmitoyl groups in H/N-Ras isoforms.

Ras and its signals diffuse through the cell on randomly moving nanoparticles.

Spatiotemporal modulation of Ras signaling from different intracellular compartments requires mechanisms allowing Ras and its signals to navigate across cells. Here, we describe one mechanism by which clusters of palmitoylated H-Ras and N-Ras isoforms but not nonpalmitoylated K-Ras diffuse through the cytoplasm, independently of ATP, on fast, randomly moving, small cytosolic nanoparticles ("rasosomes"). Rasosomes forced to diffuse out of live cells and trapped by Ras antibody beads appear as round structures of 80- to 100-nm diameter.

Galectin-3 augments K-Ras activation and triggers a Ras signal that attenuates ERK but not phosphoinositide 3-kinase activity.

Depending on the cellular context, Ras can activate characteristic effectors by mechanisms still poorly understood. Promotion by galectin-1 of Ras activation of Raf-1 but not of phosphoinositide 3-kinase (PI3-K) is one such mechanism. In this report, we describe a mechanism controlling selectivity of K-Ras4B (K-Ras), the most important Ras oncoprotein.

Inhibition of intimal thickening in the rat carotid artery injury model by a nontoxic Ras inhibitor.

Background: Neointimal formation with and without previous vascular injury is common after balloon dilation and in transplant arteriosclerosis. It involves proliferation and migration of medial smooth muscle cells and inflammation, processes that are regulated by Ras proteins and their down-stream effectors. Farnesylthiosalicylate (FTS) is a Ras inhibitor that interferes with Ras membrane anchorage and affects Ras proteins in their active state.

The Ras inhibitor S-trans, trans-farnesylthiosalicylic acid exerts long-lasting neuroprotection in a mouse closed head injury model.

Traumatic brain injury activates N-methyl-d-aspartate receptors (NMDAR) inducing activation of the Ras protein (a key regulator of cell growth, survival, and death) and its effectors. Thus, trauma-induced increase in active Ras-GTP might contribute to traumatic brain injury pathology. Based on this hypothesis, a new concept of neuroprotection is proposed, examined here by investigating the effect of the Ras inhibitor S-trans, trans-farnesylthiosalicylic acid (FTS) in a mouse model of closed head injury (CHI).