guanosine-diphosphate and Neoplasms

To search more therapeutic strategies for Ras-mutant tumors, regulators of the Ras superfamily involved in the GTP/GDP (guanosine triphosphate/guanosine diphosphate) cycle have been well concerned for their anti-tumor potentials. GTPase activating proteins (GAPs) provide the catalytic group necessary for the hydrolysis of GTPs, which accelerate the switch by cycling between GTP-bound active and GDP-bound inactive forms. Inactivated GAPs lose their function in activating GTPase, leading to the continuous activation of downstream signaling pathways, uncontrolled cell proliferation, and eventually carcinogenesis. A growing number of evidence has shown the close link between GAPs and human tumors, and as a result, GAPs are believed as potential anti-tumor targets. The present review mainly summarizes the critically important role of GAPs in human tumors by introducing the classification, function and regulatory mechanism. Moreover, we comprehensively describe the relationship between dysregulated GAPs and the certain type of tumor. Finally, the current status, research progress, and clinical value of GAPs as therapeutic targets are also discussed, as well as the challenges and future direction in the cancer therapy.

Topics: GTP Phosphohydrolases; GTPase-Activating Proteins; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Neoplasms; ras GTPase-Activating Proteins

Directly inhibiting oncogenic RAS proteins has proven to be an arduous task, as after more than thirty years of intensive investigation, no clinically relevant therapies exist. Recently, two classes of selective small molecule inhibitors that target a cysteine-containing RAS mutant have been developed, representing the first directed approaches to specifically inhibit an oncogenic KRAS mutant. In this mini-review, we first assess the development and targeting strategies associated with novel cysteine-directed RAS inhibitors. Next, we describe the variable oncogenic potency of the KRAS G12C mutant when compared to other KRAS G12 mutants. Lastly, we evaluate how the redox properties of KRAS G12C may play a role in differential signaling and tumorigenic potency of the oncogene, the efficacy of small molecules targeting this specific RAS mutant and further development of directed oncogenic RAS inhibitors.

Topics: Allosteric Regulation; Antineoplastic Agents; Cysteine; Guanosine Diphosphate; Humans; Mutation; Neoplasms; ras Proteins; Small Molecule Libraries

Ras proteins play a major role in human cancers but have not yielded to therapeutic attack. Ras-driven cancers are among the most difficult to treat and often excluded from therapies. The Ras proteins have been termed "undruggable," based on failures from an era in which understanding of signaling transduction, feedback loops, redundancy, tumor heterogeneity, and Ras' oncogenic role was poor. Structures of Ras oncoproteins bound to their effectors or regulators are unsolved, and it is unknown precisely how Ras proteins activate their downstream targets. These knowledge gaps have impaired development of therapeutic strategies. A better understanding of Ras biology and biochemistry, coupled with new ways of targeting undruggable proteins, is likely to lead to new ways of defeating Ras-driven cancers.

Topics: Animals; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Mice; Neoplasms; Oncogene Protein p21(ras); Protein Processing, Post-Translational; Proto-Oncogene Proteins p21(ras); Retroviridae Infections; Signal Transduction; Tumor Virus Infections

Rac GTPases are crucial signaling regulators in eukaryotic cells, acting downstream of many cell surface receptors. They play essential roles in diverse cellular functions including cytoskeleton dynamics, cell motility, cell survival and apoptosis. Their activities are controlled by a tightly regulated GDP/GTP cycle coupled with an alternation between cytoplasm and membrane compartments. Aberrant Rac signaling is found in some human cancers as a result of changes in the GTPase itself or in its regulation loops. This review highlights recent findings regarding the molecular and functional aspects of Rac that mediate tumorigenic transformation and metastasis. It also describes the cellular mechanisms that potentially explain the complex role of Rac in tumorigenesis. Finally, it discusses approaches for modulating Rac function as a potential anticancer strategy.

Topics: Animals; Antineoplastic Agents; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Mice; Mice, Knockout; NADPH Oxidases; Neoplasm Invasiveness; Neoplasm Metastasis; Neoplasms; Neovascularization, Pathologic; rac GTP-Binding Proteins

The concept of Molecular Science of the Living Organism was described, where the living state is explained as the purposive flows of the quantum mechanically controlled chemical reaction systems which support the homeostasis of the living organism. In the 21st century, the post genomic sequence era, the concept may be a self-evident truth. Molecular Science of the Living Organism was presented in the case of G-proteins: i.e., the atomically controlled mechanism of 1. the carcinogenesis which originates from the point mutation of ras p21, 2. the activation of a receptor protein at the cell membrane, especially in the case of bacteriorhodopsin, 3. the activation of an inactive G-protein by the activated receptor protein.

Topics: Alkyl and Aryl Transferases; Bacteriorhodopsins; Computational Biology; Genes, ras; GTP-Binding Proteins; GTPase-Activating Proteins; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Neoplasms; Point Mutation; Protein Conformation; Protons

Endogenous active substance guanosine diphosphate (GDP) is involved in the physiological process of DNA transfection and expression in the cytoplasm by binding to Ran proteins. To substantially improve the gene delivery efficiency of nanoparticles, phospholipid-coated Ca(P-GDP)/pDNA/NLS hybrid nanoparticles were prepared using GDP as a common biophosphorus source based on the biological process of exogenous gene expression in the cells. This nanoparticle has a relative uniform particle size distribution and in vitro stability. The addition of GDP in nanoparticles significantly enhanced the gene expression efficiency with good biocompatibility. Moreover, an in vivo study further verified that hybrid nanoparticles were more effective in increasing the p53 gene expression, thus significantly inhibiting the tumor growth in the heterotopic tumor model of nude mice. These results demonstrated that phospholipid-coated Ca(P-GDP) nanoparticles were a potential nonviral gene vector to promote gene expression. The experimental results confirmed the feasibility of designing a delivery system based on active substances and provided a new solution to improve the transfection efficiency of gene drugs.

Topics: Animals; Gene Expression; Genetic Therapy; Guanosine Diphosphate; Mice; Mice, Nude; Nanoparticles; Neoplasms; Particle Size; Phospholipids; ran GTP-Binding Protein

Topics: Gene Expression Regulation; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Neoplasms; Oncogenes; ras Proteins; Signal Transduction

A mutated KRAS protein is frequently observed in human cancers. Traditionally, the oncogenic properties of KRAS missense mutants at position 12 (G12X) have been considered as equal. Here, by assessing the probabilities of occurrence of all KRAS G12X mutations and KRAS dynamics we show that this assumption does not hold true. Instead, our findings revealed an outstanding mutational bias. We conducted a thorough mutational analysis of KRAS G12X mutations and assessed to what extent the observed mutation frequencies follow a random distribution. Unique tissue-specific frequencies are displayed with specific mutations, especially with G12R, which cannot be explained by random probabilities. To clarify the underlying causes for the nonrandom probabilities, we conducted extensive atomistic molecular dynamics simulations (170 μs) to study the differences of G12X mutations on a molecular level. The simulations revealed an allosteric hydrophobic signaling network in KRAS, and that protein dynamics is altered among the G12X mutants and as such differs from the wild-type and is mutation-specific. The shift in long-timescale conformational dynamics was confirmed with Markov state modeling. A G12X mutation was found to modify KRAS dynamics in an allosteric way, which is especially manifested in the switch regions that are responsible for the effector protein binding. The findings provide a basis to understand better the oncogenic properties of KRAS G12X mutants and the consequences of the observed nonrandom frequencies of specific G12X mutations.

Topics: DNA Mutational Analysis; Genes, ras; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Hydrophobic and Hydrophilic Interactions; Ligands; Markov Chains; Molecular Conformation; Molecular Dynamics Simulation; Mutation; Mutation, Missense; Neoplasms; Principal Component Analysis; Probability; Proto-Oncogene Proteins p21(ras)

KRAS mutations are the most common genetic abnormalities in cancer, but the distribution of specific mutations across cancers and the differential responses of patients with specific KRAS mutations in therapeutic clinical trials suggest that different KRAS mutations have unique biochemical behaviors. To further explain these high-level clinical differences and to explore potential therapeutic strategies for specific KRAS isoforms, we characterized the most common KRAS mutants biochemically for substrate binding kinetics, intrinsic and GTPase-activating protein (GAP)-stimulated GTPase activities, and interactions with the RAS effector, RAF kinase. Of note, KRAS G13D shows rapid nucleotide exchange kinetics compared with other mutants analyzed. This property can be explained by changes in the electrostatic charge distribution of the active site induced by the G13D mutation as shown by X-ray crystallography. High-resolution X-ray structures are also provided for the GDP-bound forms of KRAS G12V, G12R, and Q61L and reveal additional insight. Overall, the structural data and measurements, obtained herein, indicate that measurable biochemical properties provide clues for identifying KRAS-driven tumors that preferentially signal through RAF.. Biochemical profiling and subclassification of KRAS-driven cancers will enable the rational selection of therapies targeting specific KRAS isoforms or specific RAS effectors.

Topics: Animals; Crystallography, X-Ray; GTPase-Activating Proteins; Guanosine Diphosphate; Humans; Mutation; Neoplasms; Proto-Oncogene Proteins p21(ras); raf Kinases

Receptor tyrosine kinases participate in several signaling pathways through small G proteins such as Ras (rat sarcoma). An important component in the activation of these G proteins is Son of sevenless (SOS), which catalyzes the nucleotide exchange on Ras. For optimal activity, a second Ras molecule acts as an allosteric activator by binding to a second Ras-binding site within SOS. This allosteric Ras-binding site is blocked by autoinhibitory domains of SOS. We have reported recently that Ras activation also requires the actin-binding proteins ezrin, radixin, and moesin. Here we report the mechanism by which ezrin modulates SOS activity and thereby Ras activation. Active ezrin enhances Ras/MAPK signaling and interacts with both SOS and Ras in vivo and in vitro. Moreover, in vitro kinetic assays with recombinant proteins show that ezrin also is important for the activity of SOS itself. Ezrin interacts with GDP-Ras and with the Dbl homology (DH)/pleckstrin homology (PH) domains of SOS, bringing GDP-Ras to the proximity of the allosteric site of SOS. These actions of ezrin are antagonized by the neurofibromatosis type 2 tumor-suppressor protein merlin. We propose an additional essential step in SOS/Ras control that is relevant for human cancer as well as all physiological processes involving Ras.

Topics: Animals; Cytoskeletal Proteins; Guanosine Diphosphate; Humans; MAP Kinase Signaling System; Mice; Neoplasms; Neurofibromin 2; NIH 3T3 Cells; Oncogene Protein p21(ras); Son of Sevenless Proteins

To investigate the unregulated Ras activation associated with cancer, we developed and validated a mathematical model of Ras signaling. The model-based predictions and associated experiments help explain why only one of two classes of activating Ras point mutations with in vitro transformation potential is commonly found in cancers. Model-based analysis of these mutants uncovered a systems-level process that contributes to total Ras activation in cells. This predicted behavior was supported by experimental observations. We also used the model to identify a strategy in which a drug could cause stronger inhibition on the cancerous Ras network than on the wild-type network. This system-level analysis of the oncogenic Ras network provides new insights and potential therapeutic strategies.

Topics: Antineoplastic Agents; Cell Line; Cell Line, Tumor; Cell Transformation, Neoplastic; Computer Simulation; Extracellular Signal-Regulated MAP Kinases; Genes, ras; GTP Phosphohydrolases; GTPase-Activating Proteins; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Mathematics; Metabolic Networks and Pathways; Models, Biological; Neoplasms; Phosphorylation; Point Mutation; ras Proteins; Signal Transduction

Embryonic stem (ES) cells are pluripotent cells derived from early mammalian embryos. Their immortality and rapid growth make them attractive sources for stem cell therapies; however, they produce tumours (teratomas) when transplanted, which could preclude their therapeutic usage. Why ES cells, which lack chromosomal abnormalities, possess tumour-like properties is largely unknown. Here we show that mouse ES cells specifically express a Ras-like gene, which we have named ERas. We show that human HRasp, which is a recognized pseudogene, does not contain reported base substitutions and instead encodes the human orthologue of ERas. This protein contains amino-acid residues identical to those present in active mutants of Ras and causes oncogenic transformation in NIH 3T3 cells. ERas interacts with phosphatidylinositol-3-OH kinase but not with Raf. ERas-null ES cells maintain pluripotency but show significantly reduced growth and tumorigenicity, which are rescued by expression of ERas complementary DNA or by activated phosphatidylinositol-3-OH kinase. We conclude that the transforming oncogene ERas is important in the tumour-like growth properties of ES cells.

Topics: 3T3 Cells; Amino Acid Sequence; Animals; Cell Division; Cell Transformation, Neoplastic; Cloning, Molecular; Embryo, Mammalian; Genes, ras; Guanosine Diphosphate; Guanosine Triphosphate; Mice; Molecular Sequence Data; Neoplasms; Oncogene Protein p21(ras); Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-raf; Pseudogenes; Stem Cells

A cancer-specific form of NADH oxidase inhibited or stimulated by 1 or 100 microM capsaicin (8-methyl-N-vanillyl-6-noneamide) is present in sera from cancer patients. The capsaicin-inhibited NADH oxidase activity appears to be absent from sera of individuals free of cancer. The capsaicin-inhibited activity is present both in freshly collected sera and in sera stored frozen for varying periods of time. For the latter, an assay was carried out under renaturing conditions in the presence of NADH and reduced glutathione followed by dilute hydrogen peroxide. Inhibition was half maximal at about 1 microM capsaicin. The capsaicin-inhibited activity was found in sera over a broad spectrum of cancer patients including patients with solid cancers (e.g., breast, prostate, lung, ovarian) as well as with leukemias and lymphomas.

Topics: Capsaicin; Chloromercuribenzoates; Enzyme Activation; Enzyme Inhibitors; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Kinetics; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Neoplasms; p-Chloromercuribenzoic Acid

A substitution of Gly for Val at position 19, which corresponds to oncogenic Gly13-->Val mutation of ras p21, was introduced in a low Mr GTP-binding protein, ram p25. The protein was expressed in cytosolic fraction of Escherichia coli and purified by using specific antibody raised against ram p25. The mutated protein had no guanine nucleotide-binding activity although [Val13]ras p21 was reported to have. The analysis of guanine nucleotide composition of the purified [Val19]ram p25 revealed that the protein was free of nucleotide whereas the normal ram p25 bound about 1 mol of GDP per mol of protein. These results strongly suggested that some part(s) of variable regions as well as the consensus regions are important for the biochemical properties of ram p25.

Topics: Amino Acid Sequence; Base Sequence; Cloning, Molecular; Escherichia coli; Genes, ras; Glycine; GTP Phosphohydrolases; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Diphosphate; Guanosine Triphosphate; Humans; Kinetics; Molecular Sequence Data; Molecular Weight; Multigene Family; Mutagenesis, Site-Directed; Neoplasms; Oligodeoxyribonucleotides; Peptide Fragments; rab GTP-Binding Proteins; rab27 GTP-Binding Proteins; Recombinant Proteins; Sequence Homology, Amino Acid; Trypsin; Valine

Topics: Adipose Tissue, Brown; Adolescent; Child; Child, Preschool; Guanosine Diphosphate; Humans; Infant; Neoplasms

The crystal structure at 2.7 A resolution of the normal human c-H-ras oncogene protein lacking a flexible carboxyl-terminal 18 residue reveals that the protein consists of a six-stranded beta sheet, four alpha helices, and nine connecting loops. Four loops are involved in interactions with bound guanosine diphosphate: one with the phosphates, another with the ribose, and two with the guanine base. Most of the transforming proteins (in vivo and in vitro) have single amino acid substitutions at one of a few key positions in three of these four loops plus one additional loop. The biological functions of the remaining five loops and other exposed regions are at present unknown. However, one loop corresponds to the binding site for a neutralizing monoclonal antibody and another to a putative "effector region"; mutations in the latter region do not alter guanine nucleotide binding or guanosine triphosphatase activity but they do reduce the transforming activity of activated proteins. The data provide a structural basis for understanding the known biochemical properties of normal as well as activated ras oncogene proteins and indicate additional regions in the molecule that may possibly participate in other cellular functions.

Topics: Amino Acid Sequence; Antibodies, Monoclonal; Binding Sites; Catalysis; Crystallization; Epitopes; Escherichia coli; GTP Phosphohydrolases; Guanosine Diphosphate; Guanosine Triphosphate; Neoplasms; Phosphates; Protein Conformation; Proto-Oncogene Proteins; Proto-Oncogene Proteins p21(ras); Recombinant Proteins; X-Ray Diffraction