UMLS:C0178874 - FACTA Search

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Query: UMLS:C0178874 (tumor progression)
40,807 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Gene mutations in APC, K-ras, and p53 are thought to be essential events for colorectal cancer development. Recent data seem to indicate that K-ras and p53 mutations rarely co-exist in the same tumor, indicating that these alterations do not represent a synergistic evolutionary pathway. Moreover, an inverse relation between K-ras gene activation and BRAF mutations has been demonstrated, suggesting alternative pathways for colorectal cancer transformation. To reconstruct the chronological modulation of these gene mutations during cell transformation and colorectal cancer progression, mutations of p53, K-ras, and BRAF genes were analyzed by Single Strand Conformation Polymorphism (SSCP) or sequencing analysis in 100 colorectal cancer samples, evenly distributed among different Dukes' stages. We found mutations in p53, K-ras, and BRAF genes in 35%, 30%, and 4% of tumors, respectively, and observed a minimal or no co-presence of these gene alterations. Moreover, the frequency of molecular p53 mutations increased as tumor stage increased, suggesting an important role for this gene in the progression of colorectal cancer. Conversely, K-ras or BRAF genes were not related to tumor stage or location. These data seem to indicate the absence of a co-presence of the genes, highlighting the possibility of multiple pathways for colorectal tumor progression. Moreover, mutations in p53, K-ras, and BRAF are not present in about one-third of colorectal cancers and therefore other gene mutations need to be investigated to better understand molecular mechanisms at the basis of cell transformation and the progression of colorectal cancer.
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PMID:Mutation analysis of p53, K-ras, and BRAF genes in colorectal cancer progression. 1570 78

Evolution of intratumoral genetic heterogeneity during colorectal tumor progression has not been investigated so far. Multiple sample areas in colorectal adenocarcinoma at early and advanced stages and in metastases were studied for the well-known genetic alterations: K-ras and p53 point mutations and loss of heterozygosity (LOH) on chromosomes 5q and 18q. In primary colorectal cancers (CRCs), intratumoral genetic heterogeneity was more often observed in early than in advanced stages, at 90 and 67%, respectively. All but one of the advanced CRCs were composed of one predominant clone and other minor clones, whereas no predominant clone has been identified in half of the early cancers. At the early stage, the last events that were produced, the p53 mutation and LOH of 18q, were also the most heterogeneous. At the advanced stage, the LOH of 5q and 18q were the most frequent heterogeneous events (67 and 58%, respectively). The intratumoral heterogeneity for mutations was significantly reduced, from the early to the advanced stages (from 60 to 20% for K-ras and from 70 to 20% for p53). On the other hand, a quasi absence of intratumoral genetic heterogeneity was observed for K-ras and p53 in distant metastasis. In conclusion, colorectal adenocarcinomas are characterized by marked intratumoral genetic heterogeneity. A reduction of the intratumoral genetic heterogeneity for point mutations and a relative stability of the heterogeneity for allelic losses indicate that, during the progression of CRC, clonal selection and chromosome instability continue, while an increase cannot be proven.
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PMID:Evolution of intratumoral genetic heterogeneity during colorectal cancer progression. 1573 Nov 68

While Wnt and Ras signaling pathways are activated during progression of colorectal cancers, many of their important downstream targets remain to be elucidated. The gastrin gene encodes for a family of peptide growth factors that are commonly upregulated in colorectal neoplasia. Previously, we showed that the Wnt signaling pathway moderately stimulates the gastrin promoter. To determine whether Ras signaling can cooperate with Wnt signaling in transcriptional regulation of gastrin gene expression, we have analyzed the response of murine gastrin promoter-reporter gene constructs to combinations of oncogenic stimulation in transient transfection assays. We found a strong (25- to 40-fold) synergistic stimulation of the gastrin promoter by the combination of oncogenic beta-catenin and K-ras overexpression. Deletion analysis localized the response element to an area between -140 and -110bp upstream in the murine gastrin promoter. Electrophoretic mobility shift assays detected a complex containing beta-catenin/TCF, AP1, and SMAD3/4 transcription factors that bound to a DNA element through AP1 and SMAD binding sites. Gastrin promoter activation could be further enhanced or suppressed by the co-expression of wild type SMAD4 or dominant negative mutant of SMAD4, respectively, and abrogated by the PI3K inhibitor, LY20004, but not by the MEK inhibitor, PD98059. Taken together, our data strongly suggest that oncogenic Wnt and Ras signaling pathways can synergistically induce gastrin expression, possibly contributing to neoplastic progression.
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PMID:Synergistic activation of the murine gastrin promoter by oncogenic Ras and beta-catenin involves SMAD recruitment. 1613

Mutation of the K-ras gene is one of the most common genetic alterations in solid tumors, including colorectal cancer. The relatively late emergence of K-ras mutations in colorectal cancer is particularly striking in the class of mismatch repair-deficient tumors associated with early-onset microsatellite instability. We, therefore, tested the hypothesis that the microsatellite instability phenotype itself does not efficiently trigger K-ras mutations in colorectal cancer cells, but rather that tumor-associated microenvironmental conditions (e.g., hypoxia and hypoglycemia) contribute to this event by modulating genetic instability. We examined K-ras(G13D) mutation using PCR-RFLP analysis in two different microsatellite instability colorectal cancer cell lines (HCT116 and DLD-1) and their variants in which the mutant (but not the wild-type) K-ras allele has been genetically disrupted (Hkh-2 and Dks-8). We found K-ras(G13D) mutation to occur at far greater incidence in cells derived from xenografted tumors or exposed to conditions of combined hypoxia and hypoglycemia in vitro. Interestingly, this mutagenesis was neither enhanced by induced oxidative damage nor prevented by the antioxidant vitamin E. Moreover, the accumulation of K-ras mutations was paralleled by down-regulation of the key mismatch repair protein MSH2 in xenografted tumors, particularly in hypoperfused areas and under hypoglycemic conditions (in vitro). In contrast, the microsatellite stable colorectal cancer cell line Caco-2 neither accumulated K-ras mutations nor showed down-regulation of MSH2 under these conditions. Thus, our study suggests that ischemia may not simply select for, but can actually trigger, increased mutation rate in crucial colorectal cancer oncoproteins. This finding establishes a novel linkage between genetic instability, tumor ischemia, and genetic tumor progression and carries important implications for applying anticancer therapies involving tumor hypoxia (e.g., antiangiogenesis) in microsatellite instability cancers.
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PMID:Ischemia-induced K-ras mutations in human colorectal cancer cells: role of microenvironmental regulation of MSH2 expression. 1616 87

Although ras and p53 are the most commonly found oncogene and tumor suppressor gene, respectively, in human cancers, their collective roles in tumor progression have yet to be defined in animal models. Here, we demonstrated the synergistic effect between ras and p53 in promoting tumor progression during lung tumorigenesis using bitransgenic mice. Mice with a heterozygous knockout of K-ras (K-ras(wt/ko)) were mated to p53 transgenic mice (p53(val135/wt)) in lung tumorigenesis (K-ras(wt/ko) x p53(val135/wt)). F(1) mice exhibited a significant increase in lung tumor load (tumor multiplicity x tumor volume) when compared to those seen in either K-ras(wt/ko) mice or p53(val135/wt) mice alone. Furthermore, over 50% of the lung tumors were lung adenocarcinomas in bitransgenic mice compared to only 3% in wild-type mice. Alterations of ras and p53 appear to promote the development of lung adenocarcinomas. These results provide the in vivo experimental evidence of synergistic interactions of ras and p53 in lung tumor progression.
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PMID:A mouse model for tumor progression of lung cancer in ras and p53 transgenic mice. 1624 44

Bexarotene (Targretin), is a synthetic high-affinity RXR receptor agonist with limited affinity for RAR receptors. Bexarotene has shown efficacy in a phase I/II trial of non-small-cell lung cancers. However, the chemopreventive efficacy of bexarotene has not been determined in mouse lung cancer models. In this study, we have investigated the ability of bexarotene to inhibit lung tumor progression in the mutant A/J mouse models with genetic alterations in p53 or K-ras, two of the most commonly altered genes in human lung tumorigenesis. Mice were administered vinyl carbamate (VC), a carcinogen, by a single intraperitoneal injection (i.p.) at 6 weeks of age. Bexarotene was given by gavage starting at 16 weeks after VC and was continued for 12 weeks. Although all mice developed lung tumors, only 7% of lung tumors were adenocarcinomas in wild-type mice, whereas 22 and 26% of lung tumors were adenocarcinomas in p53 transgenic or K-ras heterozygous deficient mice. Bexarotene inhibited both tumor multiplicity and tumor volume in mice of all three genotypes. Furthermore, bexarotene reduced the progression of adenoma to adenocarcinoma by approximately 50% in both p53(wt/wt)K-ras(ko/wt) and p53(wt/wt)K-ras(wt/wt) mice. Thus, bexarotene appears to be an effective preventive agent against lung tumor growth and progression.
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PMID:Prevention of lung cancer progression by bexarotene in mouse models. 1624 46

Activating mutations in the K-ras gene are genetic alterations frequently found in human carcinomas, particularly in pancreatic adenocarcinomas. Mutation of the K-ras gene is thought to be an early and important event in pancreatic tumor initiation, but the precise role of the mutant K-Ras proteins in neoplastic progression is still unknown. In the present study, we have characterized the influence of oncogenic K-Ras on the phenotype and on the signal transduction of epitheloid PANC-1 pancreatic carcinoma cells by generating PANC-1 cell clones, which stably express EGFP(enhanced green fluorescent protein)-K-Ras (V12). EGFP-K-Ras (V12)-expressing cells exhibited a more fibroblastoid cellular phenotype with irregular cell shape and disorganized cytokeratin filaments. Moreover, these cells showed a marked enhancement of their migratory and invasive properties. Stable expression of EGFP-K-Ras (V12) down-regulated the activity of Rac1 and RhoA, resulting in reduced subcortical actin filaments and stress fibers, which might contribute to the epithelial dedifferentiation. Characterization of the activity of mitogen-activated protein kinases revealed that EGFP-K-Ras (V12) enhanced the activity of p38, but did not affect the activities of the Raf/MEK/ERK cascade and JNK. While inhibition of either MEK or JNK activity had no effect on EGFP-K-Ras (V12)-induced migration, inhibition of p38 activity markedly reduced EGFP-K-Ras (V12)-induced migration. Collectively, the results suggest that oncogenic K-Ras enhances the malignant phenotype and identify the mitogen-activated protein kinase p38 as a target to inhibit oncogenic K-Ras-induced pancreatic tumor cell migration.
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PMID:Oncogenic K-Ras down-regulates Rac1 and RhoA activity and enhances migration and invasion of pancreatic carcinoma cells through activation of p38. 1625 81

Activating mutations in K-ras are one of the most common genetic alterations in human lung cancer. To dissect the role of K-ras activation in bronchial epithelial cells during lung tumorigenesis, we created a model of lung adenocarcinoma by generating a conditional mutant mouse with both Clara cell secretory protein (CC10)-Cre recombinase and the Lox-Stop-Lox K-ras(G12D) alleles. The activation of K-ras mutant allele in CC10 positive cells resulted in a progressive phenotype characterized by cellular atypia, adenoma and ultimately adenocarcinoma. Surprisingly, K-ras activation in the bronchiolar epithelium is associated with a robust inflammatory response characterized by an abundant infiltration of alveolar macrophages and neutrophils. These mice displayed early mortality in the setting of this pulmonary inflammatory response with a median survival of 8 weeks. Bronchoalveolar lavage fluid from these mutant mice contained the MIP-2, KC, MCP-1 and LIX chemokines that increased significantly with age. Cell lines derived from these tumors directly produced MIP-2, LIX and KC. This model demonstrates that K-ras activation in the lung induces the elaboration of inflammatory chemokines and provides an excellent means to further study the complex interactions between inflammatory cells, chemokines and tumor progression.
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PMID:K-ras activation generates an inflammatory response in lung tumors. 1628 13

Progression of human malignancies is accompanied by vascular events, such as formation and remodeling of blood vessels and systemic coagulopathy. Though long appreciated as comorbidity of cancer (Trousseau syndrome), vascular involvement is increasingly recognized as a central pathogenetic mechanism of tumor growth, invasion and metastasis. The major outstanding question in relation to this role has been, whether vascular perturbations are simply a reaction to the conditions of the tumor microenvironment, or are linked to the known genetic lesions causal for the onset and progression of malignancy. In this regard, we have previously hypothesized, and recently demonstrated experimentally that deregulation of certain hemostatic mechanisms, namely upregulation of tissue factor (TF) and possibly other changes (e.g. expression of thrombin receptor - PAR-1) are controlled by cancer-associated oncogenic events, such as activation of K-ras, epidermal growth factor receptor (EGFR), or inactivation of the p53 tumor suppressor gene in various human cancer cells. It appears that these respective transforming alterations exert their impact on both, cell-associated and soluble/circulating (microvesicle- associated) TF, i.e. may cause a systemic hypercoagulable state. Other genes, which more recently emerged as regulators of cancer coagulopathy include: PML-RARalpha, PTEN, and MET. While the spectrum of procoagulant targets of these genes may vary somewhat it includes: TF, PAI-1, COX-2 and possibly other hemostatic proteins. It is noteworthy that these prothrombotic changes may impact the malignant process directly (e.g. stimulate angiogenesis, tumor growth or metastasis) as a consequence of both coagulation-dependent and -independent effects. The latter are mostly related to cellular signaling events and changes in gene expression which are now known to be induced by the TF/FVIIa/Xa complex, thrombin and PARs, expressed on the surface of cancer cells, as well as tumor-associated endothelium. Interestingly, certain anticoagulants possess antimetastatic and anticancer properties (e.g. LMWH), an observation that further suggests that hypercoagulability may act as an effector mechanism of genetically driven tumor progression. Conversely, we suggest that oncogene-directed (targeted) anticancer agents could, at least in some cases, ameliorate not only cellular transformation itself, but also some of the chronic components of the cancer-related coagulopathy, something that may be relevant to therapeutic efficacy of these drugs. We also postulate that since TF is the oncogene target, circulating TF (microparticles) could serve as surrogate marker of the biological activity oncogene-directed agents exert in vivo. Thus, both genetic and epigenetic factors appear to conspire to activate various components of the hemostatic system in cancer patients, both locally and systemically. These activities act as mediators of cancer coagulopathy, angiogenesis, metastasis and other events involved in disease progression and should be recognized in designing better anticancer therapies.
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PMID:Genetic determinants of cancer coagulopathy, angiogenesis and disease progression. 1663 63

Mouse glioma 261 (Gl261) cells are used frequently in experimental glioblastoma therapy; however, no detailed description of the Gl261 tumor model is available. Here we present that Gl261 cells carry point mutations in the K-ras and p53 genes. Basal major histocompatibility complex (MHC)I, but not MHCII, expression was detected in Gl261 cells. The introduction of interferon-gamma-encoding genes increased expression of both MHCI and MHCII. A low amount of B7-1 and B7-2 RNA was detected in wild-type cells, but cytokine production did not change expression levels. Gl261 cells were transduced efficiently by adenoviral vectors; the infectivity of retroviral vectors was limited. Low numbers of transplanted Gl261 cells formed both subcutaneous and intracranial tumors in C57BL/6 mice. The cells were moderately immunogenic: prevaccination of mice with irradiated tumor cells 7 days before intracranial tumor challenge prevented tumor formation in approximately 90% of mice. When vaccination was carried out on the day or 3 days after tumor challenge, no surviving animals could be found. In vitro-growing cells were radiosensitive: less than 2 Gy was required to achieve 50% cell mortality. Local tumor irradiation with 4 Gy X-rays in brain tumor-bearing mice slowed down tumor progression, but none of the mice were cured off the tumor. In conclusion, the Gl261 brain tumor model might be efficiently used to study the antitumor effects of various therapeutic modalities, but the moderate immunogenicity of the cells should be considered.
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PMID:Detailed characterization of the mouse glioma 261 tumor model for experimental glioblastoma therapy. 1673 35

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