Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0178874 (tumor progression)
 40,807 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Environmental chemicals may affect human health by disrupting endocrine function. Their possible role in the mammary gland and breast tumors is still unknown. Previous studies have demonstrated that vascular endothelial growth factor (VEGF), a key factor in angiogenesis and tumor progression, is an estrogen-regulated gene. We analyzed whether VEGF expression is regulated by different xenoestrogens in several breast cancer cells, MELN (derived from MCF-7) and MELP (derived from MDA-MB-231) and stably expressing estrogen receptor alpha (ERalpha); these cell lines stably express estrogen response element (beta-globin)-luciferase. Genistein, bisphenol A (BPA), 4-(tert-octyl)phenol (OP), dieldrin, and several phthalates, including benzyl butyl phthalate (BBP) and di-ethyl-2-hexyle phthalate (DEHP), were first shown to be estrogenic. These compounds induced a dose-dependent increase of VEGF secretion in MELN and MCF-7 cells; maximal effect was observed at 1-10 microM non-cytotoxic concentrations and was inhibited by the antiestrogen ICI 182 780. VEGF increase was not observed in ERalpha-negative MDA-MB-231 cells. Most substances increased VEGF transcript levels in MELN cells. In contrast, gamma-hexachlorocyclohexane, vinclozolin, and the phthalates (mono-n-butyl ester phthalic acid, di-isononyle phthalate, and di-isodecyle phthalate) were ineffective on both VEGF secretion and estrogenic luciferase induction in these cell lines. Specific kinase inhibitors PD98059, SB203580, or LY294002 suppressed the xenoestrogen-induced VEGF response, suggesting activation of MEK, p38 kinase, and phosphatidylinositol-3-kinase pathways. Our in vitro results show for the first time that genistein and xenoestrogens (BPA, OP, dieldrin, BBP, and DEHP at high concentrations) up-regulate VEGF expression in MELN cells by an ER-dependent mechanism. Since VEGF increases capillary permeability and breast tumor angiogenesis in vivo, the physiological relevance of these findings is discussed.
 ...
PMID:Xenoestrogens modulate vascular endothelial growth factor secretion in breast cancer cells through an estrogen receptor-dependent mechanism. 1825 63

Oncogenic K-ras mutations are frequently observed in colon cancers and contribute to transformed growth. Oncogenic K-ras is detected in aberrant crypt foci (ACF), precancerous colonic lesions, demonstrating that acquisition of a K-ras mutation is an early event in colon carcinogenesis. Here, we investigate the role of oncogenic K-ras in neoplastic initiation and progression. Transgenic mice in which an oncogenic K-ras(G12D) allele is activated in the colonic epithelium by sporadic recombination (K-rasLA2 mice) develop spontaneous ACF that are morphologically indistinguishable from those induced by the colon carcinogen azoxymethane (AOM). Similar neoplastic changes involving the entire colon are induced in transgenic mice constitutively expressing K-ras(G12D) throughout the colon (LSL-K-ras(G12D)/Villin-Cre mice). However, the biochemistry and fate of K-ras-induced lesions differ depending upon their location within the colon in these mice. In the proximal colon, K-ras(G12D) induces increased expression of procarcinogenic protein kinase C beta II (PKC beta II), activation of the MEK/ERK signaling axis and increased epithelial cell proliferation. In contrast, in the distal colon, K-ras(G12D) inhibits expression of procarcinogenic PKC beta II and induces apoptosis. Treatment of K-rasLA2 mice with AOM leads to neoplastic progression of small ACF to large, dysplastic microadenomas in the proximal, but not the distal colon. Thus, oncogenic K-ras functions differently in the proximal and distal colon of mice, inducing ACF capable of neoplastic progression in the proximal colon, and ACF with little or no potential for progression in the distal colon. Our data indicate that acquisition of a K-ras mutation is an initiating neoplastic event in proximal colon cancer development in mice.
 ...
PMID:Oncogenic K-ras promotes early carcinogenesis in the mouse proximal colon. 1827 Oct 8

Recent evidence has implied that disruption of a limited number of defined cellular pathways is necessary and sufficient for neoplastic conversion of a variety of normal human cell types in tissue culture. We show instead that malignancy in such models results from an iterative process of clonal selection in vitro and/or in vivo. Normal human fibroblasts underwent malignant transformation after transduction with telomerase, cyclin-dependent kinase 4, dominant-negative p53, and activated Ras or MEK. Furthermore, culture conditions favoring overgrowth resulted in clonal selection, which with added Ras or MEK oncogenes led to the emergence of tumorigenic clones. Such tumors showed variable degrees of malignancy with some even exhibiting metastasis. SV40 small t antigen (ST) has been reported to be necessary and sufficient to convert human fibroblasts with these pathway aberrations to a polyclonal tumor. However, we observed that clonal tumors emerged even with ST addition. Genomic instability was markedly increased by p53 and Rb pathway abrogation. Under the same conditions, fibroblasts with these alterations failed to induce tumors, implying that genomic instability may be necessary but not sufficient for malignant transformation. These findings indicate that the minimum number of events required for malignant transformation of human fibroblasts is greater than has been enumerated by such oncogene addition strategies and support a stochastic cancer progression model initiated by four defined cellular alterations.
 ...
PMID:Clonal selection in malignant transformation of human fibroblasts transduced with defined cellular oncogenes. 1831 5

Activation of the Raf/MEK/ERK pathway, often by gain-of-function mutations of RAS or RAF, is observed in many human cancers. The extracellular signal-regulated kinase (ERK) pathway is required for the proliferation of cancer cell lines harboring activating BRAF or, to a lesser extent, activating RAS mutations. It is still unclear, however, whether the pathway is required in vivo for tumor development, particularly in tumors in which B-Raf is not mutationally activated. During embryonic development, B-Raf is essential for angiogenesis in the placenta. To address the question of whether B-Raf contributed to tumor angiogenesis in vivo we conditionally ablated B-Raf in a model of pancreatic islet carcinoma driven by the functional inactivation of tumor suppressors (RIP1Tag2), which critically depends on angiogenesis for growth. We find that B-Raf is dispensable for the proliferation of tumor cells in culture, but necessary for ERK activation and for the expression of angiogenic factors by tumor cells in vivo and in vitro. In vivo, these defects result in the formation of hollow tumors with decreased vessel density and strongly reduced proliferation. The progression from adenoma to carcinoma is also significantly impaired. Thus, endogenous B-Raf contributes to the development of RIP1Tag2 tumors by supporting the stromal response and tumor progression.
 ...
PMID:B-Raf is required for ERK activation and tumor progression in a mouse model of pancreatic beta-cell carcinogenesis. 1849 Sep 24

TIMP-1 (Tissue inhibitor of matrix metalloproteinase-1) is typically associated with inhibition of matrix metalloproteinases (MMP) induced invasion. However, TIMP-1 is overexpressed in many malignancies and is associated with poor prognosis in breast cancer. The mechanisms by which TIMP-1 promotes tumorigenesis are unclear. Reduced levels of TIMP-1 mediated by shRNA in MDA-MB-231 breast cancer cells had no effect on cellular physiology in vitro or tumor growth in SCID mice compared to vector control MDA-MB-231 cells. However, overexpression of TIMP-1 in MDA-MB-231 cells resulted in inhibition of cell invasion and enhanced phosphorylation of p38 MAPK and AKT in vitro. Additionally, treatment of parental MDA-MB-231 cells with purified TIMP-1 protein led to activation of p38 MAPK and MKK 3/6. cDNA array analysis demonstrated that high expression of TIMP-1 in MDA-MB-231 cells resulted in alterations in expression of approximately 200 genes, 1.5 fold or greater compared to vector control cells (P < 0.1). Real-time RT-PCR confirmed changes in expression of several genes associated with cancer progression including DAPK1, FGFR4 and MAPK13. In vivo, high TIMP-1 expression induced tumor growth in SCID mice compared to vector control cells and increased tumor vessel density. Affymetrix array analysis of vector control and TIMP-1 MDA-MB-231 xenograft tumors revealed that TIMP-1 altered expression of approximately 600 genes in vivo, including MMP1, MMP13, S100A14, S100P, Rab25 and ID4. These combined observations suggest that the effects of TIMP-1 differ significantly in a 2-D environment compared to the 3-D environment and that TIMP-1 stimulates tumor growth.
 ...
PMID:TIMP-1 overexpression promotes tumorigenesis of MDA-MB-231 breast cancer cells and alters expression of a subset of cancer promoting genes in vivo distinct from those observed in vitro. 1878 47

Signaling by the receptor for stem cell factor (SCF), c-Kit, is of major importance for hematopoiesis, melanogenesis and reproduction, and the biological responses are commonly proliferation and cell survival. Thus, constitutive activation due to c-Kit mutations is involved in the pathogenesis of several forms of cancer, e.g. leukemias, gastrointestinal stromal tumors and testicular tumors. Tumor survival requires oxygen supply through induced neovascularization, a process largely mediated by the vascular endothelial growth factor (VEGF), a prominent target of the transcription factors hypoxia-inducible factor-1 (HIF-1) and HIF-2. Using Affymetrix microarrays we have identified genes that are upregulated following SCF stimulation. Interestingly, many of the genes induced were found to be related to a hypoxic response. These findings were corroborated by our observation that SCF stimulation of the hematopoietic cell lines M-07e induces HIF-1alpha and HIF-2alpha protein accumulation at normoxia. In addition, SCF-induced HIF-1alpha was transcriptionally active, and transcribed HIF-1 target genes such as VEGF, BNIP3, GLUT1 and DEC1, an effect that could be reversed by siRNA against HIF-1alpha. We also show that SCF-induced accumulation of HIF-1alpha is dependent on both the PI-3-kinase and Ras/MEK/Erk pathways. Our data suggest a novel mechanism of SCF/c-Kit signaling in angiogenesis and tumor progression.
 ...
PMID:Stem cell factor induces HIF-1alpha at normoxia in hematopoietic cells. 1883 62

Although the health benefits of dietary antioxidants have been extensively studied, their potential negative effects remain unclear. L-Ascorbic acid 6-palmitate (AAP), a synthetic derivative of ascorbic acid (AA), is widely used as an antioxidant and preservative in foods, vitamins, drugs, and cosmetics. Previously, we found that AA exerted an antitumor effect by protecting inhibition of gap-junctional intercellular communication (GJIC), which is closely associated with tumor progression. In this study, we examined whether AAP, an amphipathic derivative of AA, has chemopreventive effects using a GJIC model. AAP and AA exhibited dose-dependent free radical-scavenging activities and inhibited hydrogen peroxide (H(2)O(2))-induced intracellular reactive oxygen species (ROS) production in normal rat liver epithelial cells. Unexpectedly, however, AAP did not protect against the inhibition of GJIC induced by H(2)O(2); instead, it inhibited GJIC synergistically with H(2)O(2). AAP inhibited GJIC in a dose-dependent and reversible manner. This inhibitory effect was not due to the conjugated lipid structure of AAP, as treatment with palmitic acid alone failed to inhibit GJIC under the same conditions. The inhibition of GJIC by AAP was restored in the presence of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibitor U0126, but not in the presence of other signal inhibitors and antioxidant (PKC inhibitors, EGFR inhibitor, NADPH oxidase inhibitor, catalase, vitamin E, or AA), indicating the critical involvement of MEK signaling in the GJIC inhibitory activity of AAP. Phosphorylation of ERK and connexin 43 (Cx43) was observed following AAP treatment, and this was reversed by U0126. These results suggest that the AAP-induced inhibition of GJIC is mediated by the phosphorylation of Cx43 via activation of the MEK-ERK pathway. Taken together, our results indicate that AAP has a potent carcinogenic effect, and that the influence of dietary antioxidants on carcinogenesis may be paradoxical.
 ...
PMID:Ascorbic acid 6-palmitate suppresses gap-junctional intercellular communication through phosphorylation of connexin 43 via activation of the MEK-ERK pathway. 1902 67

Lung metastasis is one of the important characteristics of salivary adenoid cystic carcinoma (SACC). Although activation of extracellular signal-regulated kinase 1/2 (ERK1/2) pathway may be associated with cancer progression in some malignant tumors, its roles in lung metastasis of SACC remains unclear. We examined the expression of activated ERK1/2 in SACC-LM with high lung-metastatic rate and SACC-83 with low lung-metastatic rate, as well as in the tissues from lung-metastatic and non-metastatic groups of SACC patients. Western blot analysis indicated that SACC-LM exhibited higher expression of activated ERK1/2 than SACC-83. Similarly, immunohistochemistry showed that expression of activated ERK1/2 was detected in 73% (8/11) of the primary tissues from SACC patients with lung metastasis, while only 25% (3/12) of the primary tissues from SACC patients without lung metastasis (P<0.05). Furthermore, we examined the effects of U0126, a specific inhibitor of mitogen activated protein kinase kinase (MEK or MAPKK), on migration and invasion in SACC-LM cells, showing U0126 not only inactivated ERK1/2, but also inhibited migration and invasion of SACC-LM. The present findings suggested that the elevated expression of activated ERK1/2 may play a role in lung metastasis of salivary adenoid cystic carcinoma.
 ...
PMID:Relationship of activated extracellular signal-regulated kinase 1/2 with lung metastasis in salivary adenoid cystic carcinoma. 1908 54

The matricellular protein CCN2 (connective tissue growth factor, CTGF) has been previously implicated in tumorigenesis. In pancreatic cancer cells, CCN2 expression occurs downstream of ras/MEK/ERK. Direct evidence that CCN2 mediates tumor progression in pancreatic cancer has been lacking. An exciting recent report by Bennewith et al. (Cancer Res 69:775-784, 2009) has used shRNA knockdown of CCN2 to illustrate that CCN2 contributes to growth of pancreatic tumor cells, both in vitro and in vivo. This report briefly summarizes these findings.
 ...
PMID:Death of a tumor: targeting CCN in pancreatic cancer. 1926 21

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is known to promote cancer initiation and progression and accumulates in mammary fat tissue. Effects of TCDD are mediated by the aryl hydrocarbon receptor (AhR). Physiological conditions of moderate hypoxia in breast cancer also activate another transcription factor, hypoxia-inducible factor-1 alpha (HIF-1alpha). In addition, the transcription factors p53 and the estrogen receptor alpha (ERalpha) are important key players in breast cancer progression. Here, human breast cancer cells cultured under mild hypoxic conditions were exposed to TCDD and analyzed for regulation of p53 signaling and ERalpha transactivation. Simultaneous exposure to TCDD and hypoxia resulted in a moderate but reproducible inhibition of p53 expression. Both the direct activation of the ERalpha and the transcriptional regulation of Hdm2 mediated this inhibition. As consequence the p53-mediated target gene expression (Dusp5) was reduced. Silencing of Dusp5 by simultaneous exposure of TCDD and hypoxia or by RNAi led to increased phosphorylation of ERK1/2. This increase resulted in transactivation of ERalpha and induction of ERalpha-mediated transcription of Hdm2 and SOCS3. Specificity of ERalpha-transactivation by ERK1/2 was confirmed by treatment with MAPKK-inhibitor PD98059. The combination of inhibition of functional p53 protein and induction of ERalpha signaling could serve as a model for the operational sequence of TCDD effects to prevent cell death and promote breast tumor progression.
 ...
PMID:TCDD mediates inhibition of p53 and activation of ERalpha signaling in MCF-7 cells at moderate hypoxic conditions. 1957 57


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>