• Journal of Life Science
• /
• v.20 no.2
• /
• pp.202-207
• /
• 2010

Ras genes are responsible for up to 30% of human tumor mutations and are composed of three isoforms: H-Ras, K-Ras and N-Ras. The post-translational modification of the CAAX motif of the Ras protein is essential in Ras actions. In the present study, we studied the effects of novel farnesyl transferase inhibitors (FTIs), YH3938 and YH3945, on the actions of oncogenic mutants of H-Ras, K-Ras and N-Ras. YH3938 and YH3945 completely reverted the proliferation and morphology of oncogenic H-Ras-transformed Rat2 cells, but not of oncogenic K-Ras-transformed Rat2 cells. Oncogenic N-Ras-transformed Rat2 cells were slightly affected. Activation of SRE promoters by oncogenic H-Ras and N-Ras, but not by K-Ras, were inhibited by treatment with YH3938 and YH3945. Using bandshift analysis, YH3938 suppressed the processing of oncogenic H-Ras and N-Ras, but not that of oncogenic K-Ras protein. YH3945 only inhibited the processing of H-Ras. From these results, we conclude that YH3938 and YH3945 specifically inhibit actions of oncogenic H-Ras through inhibition of its farnesylation, that YH3938 also inhibits N-Ras activity in a dose-dependent manner, and that these drugs have no effect on oncogenic K-Ras activity.

• BMB Reports
• /
• v.49 no.7
• /
• pp.370-375
• /
• 2016

Ras oncoproteins are small molecular weight GTPases known for their involvement in oncogenesis, which operate in a complex signaling network with multiple effectors. Approximately 25% of human tumors possess mutations in a member of this family. The Raf1/MEK/Erk1/2 pathway is one of the most intensively studied signaling mechanisms. Different levels of regulation account for the inactivation of MAP kinases by MAPK phosphatases in a cell type- and stimuli-dependent manner. In the present study, using three inducible Ras-expressing NIH/3T3 cell lines, we demonstrated that MKP3 upregulation requires the activation of the Erk1/2 pathway, which correlates with the shutdown of this pathway. We also demonstrated, by applying pharmacological inhibitors and effector mutants of Ras, that induction of MKP3 at the protein level is positively regulated by the oncogenic Ras/Raf/MEK/Erk1/2 signaling pathway.

• Biomolecules & Therapeutics
• /
• v.6 no.4
• /
• pp.345-350
• /
• 1998

The adverse effects of ethanol on cell proliferation have been described for a variety of tissues and cells. In the present study, we investigated whether chronic ethanol intoxication impairs the cell proliferation and DNA synthesis induced by oncogenic $H-ras^{V12}$ - and $v-K-ras^{V12}$-transformed cells. Ethanol treatment inhibited the cell proliferation and the DNA synthesis of control parental fibroblasts in a time- and dose-dependent manner. In contrast, ethanol did not suppress the proliferation of either oncogenic $H-ras^{V12}$ - or $v-K-ras^{V12}$ -transformed fibroblasts. Microinjection of oncogenic $H-Ras^{V12}$ protein induces DNA synthesis and ethanol treatment did not interfere with the DNA synthesis. The antiproliferative toxicity of ethanol was rescued by antioxidants, such as N-acetylcysteine and 4-methlpyrazole. These results indicate that the antiproliferative action site of ethanol toxicity lies upstream or is independent of Ras and ethanol exerts its toxicity through a free radical formation.

• BMB Reports
• /
• v.32 no.2
• /
• pp.196-202
• /
• 1999

The existence of the Ras-independent signal transduction pathway of insulin leading to DNA synthesis was investigated in Rat-1 fibroblasts overexpressing human insulin receptor (HIRc-B) using the single-cell microinjection technique. Microinjection of a dominant-negative mutant $Ras^{N17}$ protein into quiescent HIRc-B cells inhibited the DNA synthesis stimulated by insulin. Microinjection of oncogenic H-$Ras^{V12}$ protein ($H-Ras^{V12}$) (0.1 mg/ml) induced DNA synthesis by 35%, whereas that of control-injected IgG was induced by 20%. When the marginal amount of oncogenic H-$Ras^{V12}$ protein was coinjected with a dominant-negative mutant of the H-Ras protein ($Ras^{N17}$), DNA synthesis was 35% and 74% in the absence and presence of insulin, respectively. This full recovery of DNA synthesis by insulin suggests the existence of the Ras-independent pathway. The same recovery was observed in the cells coinjected with either H-$Ras^{V12}$ plus H-$Ras^{N17}$ plus SH2 domain of the p85 subunit of PI3-kinase ($p85^{SH2-N}$) or H-$Ras^{V12}$ plus H-$Ras^{N17}$ plus interfering anti-Shc antibody. When co-injected with a dominant-negative H-$Ras^{N17}$, the DNA synthesis induced by the Ras-independent pathway was blocked. These results indicate that the Ras-independent pathway of insulin leading to DNA synthesis exists, bypassing the p85 of PI3-kinase and Shc protein, and requires Rac1 protein.

• The Korean Journal of Physiology and Pharmacology
• /
• v.24 no.3
• /
• pp.267-276
• /
• 2020

T In the present study, we investigated the effect of oncogenic H-Ras on rat mdr1b expression in NIH3T3 cells. The constitutive expression of H-Ras^V12 was found to downregulate the mdr1b promoter activity and mdr1b mRNA expression. The doxorubicin-induced mdr1b promoter activity of the H-Ras^V12 expressing NIH3T3 cells was markedly lower than that of control NIH3T3 cells. Additionally, there is a positive correlation between the level of H-Ras^V12 expression and a sensitivity to doxorubicin toxicity. To examine the detailed mechanism of H-Ras^V12-mediated down-regulation of mdr1b expression, antioxidant N-acetylcysteine (NAC) and NADPH oxidase inhibitor diphenylene iodonium (DPI) were used. Pretreating cells with either NAC or DPI significantly enhanced the oncogenic H-Ras-mediated down-regulation of mdr1b expression and markedly prevented doxorubicin-induced cell death. Moreover, NAC and DPI treatment led to a decrease in ERK activity, and the ERK inhibitors PD98059 or U0126 enhanced the mdr1b-Luc activity of H-Ras^V12-NIH3T3 and reduced doxorubicin-induced apoptosis. These data suggest that Ras^V12 expression could downregulate mdr1b expression through intracellular reactive oxygen species (ROS) production, and ERK activation induced by ROS, is at least in part, contributed to the downregulation of mdr1b expression.

• Archives of Pharmacal Research
• /
• v.25 no.6
• /
• pp.759-769
• /
• 2002

Mutated forms of ras are found in many human tumors and the rate of incidence is significantly higher in colon and pancreatic cancers. The protein product from the ras oncogene is a small G-protein, $p21^{ras}{\;}(Ras)$ that is known to playa key role in the signal transduction cascade and cell differentiation and proliferation. Mutated Ras is unable to regulate itself and remains constantly activated, leading to uncontrolled cell growth. The function of Ras in signal transduction requires its location near the growth factor receptor at the cell membrane. However, Ras does not have a transmembrane domain. Ras requires farnesylation to increase its hydrophobicity and subsequent plasma membrane association for its transforming activity. This key post-translational modification is catalyzed by the enzyme Ras farnesyltransferase (FTase), which transfers a farnesyl group from farnesylpyrophosphate to the C-terminal cysteine of the Ras protein. The requirement has focused attention on FTase as a target for therapeutic intervention. Selective inhibition of FTase will prevent Ras protein from association with the plasma membrane, leading to a disruption of oncogenic Ras function.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.6
• /
• pp.2787-2793
• /
• 2016

Background: Urinary bladder cancer is a common malignancy in the West and ranks as the $7^{th}$ most common cancer in our region of Kashmir, India. FGFR3 mutations are frequent in superficial urothelial carcinoma (UC) differing from the RAS gene mutational pattern. The aim of this study was to analyze the frequency and association of FGFR3 and RAS gene mutations in UC cases. Materials and Methods: Paired tumor and adjacent normal tissue specimens of 65 consecutive UC patients were examined. DNA preparations were evaluated for the occurrence of FGFR3 and RAS gene mutations by PCR-SCCP and DNA sequencing. Results: Somatic point mutations of FGFR3 were identified in 32.3% (21 of 65). The pattern and distribution were significantly associated with low grade/stage (p<0.05). The overall mutations in exon 1 and 2 in all the forms of RAS genes aggregated to 21.5% and showed no association with any clinic-pathological parameters. In total, 53.8% (35 of 65) of the tumors studied had mutations in either a RAS or FGFR3 gene, but these were totally mutually exclusive in and none of the samples showed both the mutational events in mutually exclusive RAS and FGFR3. Conclusions: We conclude that RAS and FGFR3 mutations in UC are mutually exclusive and non-overlapping events which reflect activation of oncogenic pathways through different elements.

• Proceedings of the Korean Society of Toxicology Conference
• /
• 2001.10a
• /
• pp.154-155
• /
• 2001

Cyclooxygenase-2 (COX-2) is an inducible enzyme expressed in response to a variety of proinflammatory agents and cytokines. COX-2 expression has been shown to be elevated in several different types of human cancer. The presence of oncogenic ras has been associated with constitutive induction of COX-2 in certain H-ras transformed cells, and COX-2 overexpression confers resistance to apoptosis.(omitted)

• Journal of Life Science
• /
• v.22 no.4
• /
• pp.538-544
• /
• 2012

Ethanol is known as being carcinogenic to humans. In addition, the anti-proliferative effects of ethanol have been described for a variety of tissues and cells. In this study, we investigated the anti-proliferative effects of ethanol on various cancer cells, particularly on oncogenic $ras$-transformed or-injected cells. Ethanol treatment inhibited the cell proliferation of normal control cells, but did not suppress the proliferation of various cancer cells and oncogenic $ras$-transformed cells. Furthermore, ethanol treatment did not interfere with DNA synthesis, which was induced by microinjecting the oncogenic $H-Ras^{V12}$ protein. The anti-proliferative effect of ethanol was rescued by antioxidants, such as $N$-acetylcysteine and 4-methlpyrazole. These results suggest that ethanol cytotoxicity is exerted through free radical formation, and that the anti-proliferative action site of ethanol cytotoxicity either lies upstream, or is independent of Ras.

• Proceedings of the PSK Conference
• /
• 2001.04a
• /
• pp.117.1-117.1
• /
• 2001