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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphoinositide-3-OH kinases (PI(3)Ks) constitute a family of evolutionarily conserved lipid kinases that regulate a vast array of fundamental cellular responses, including proliferation, transformation, differentiation and protection from apoptosis. PI(3)K-mediated activation of the cell survival kinase PKB/Akt, and negative regulation of PI(3)K signalling by the tumour suppressor PTEN (refs 3, 4) are key regulatory events in tumorigenesis. Thus, a model has arisen that PI(3)Ks promote development of cancers. Here we report that genetic inactivation of the p110gamma catalytic subunit of PI(3)Kgamma (ref. 8) leads to development of invasive colorectal adenocarcinomas in mice. In humans, p110gamma protein expression is lost in primary colorectal adenocarcinomas from patients and in colon cancer cell lines. Overexpression of wild-type or kinase-dead p110gamma in human colon cancer cells with mutations of the tumour suppressors APC and p53, or the oncogenes beta-catenin and Ki-ras, suppressed tumorigenesis. Thus, loss of p110gamma in mice leads to spontaneous, malignant epithelial tumours in the colorectum and p110gamma can block the growth of human colon cancer cells.
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PMID:Colorectal carcinomas in mice lacking the catalytic subunit of PI(3)Kgamma. 1167 95

We hypothesized that the tolerance for nutrient deprivation as well as angiogenesis might be an important factor for tumor progression under hypovascular conditions. When normal human fibroblasts were subjected to extreme nutrient starvation by culturing in a medium without serum, glucose, and amino acids, cells died within 24 h. When substituted with liver cancer cell lines HepG2, Hep3B, HLE, and HuH-7, cell death occurred within 36 h. In contrast, four of six pancreas cancer cell lines, PANC-1, AsPC-1, BxPC-1, and KP-3, survived for remarkably longer periods; >50% of the cells survived, even after starvation for 48 h. Among three gastric cancer cell lines, MKN28, MKN45, and MKN74, only the most poorly differentiated MKN45 cells survived >36 h. More than 50% of the cells in colon cancer cell lines SW480, WiDr, and DLD-1 survived after 36 h, and the most undifferentiated SW480 cell line survived longest. We examined the possible involvement of PKB/Akt expression in the survival of various cell lines under nutrient starvation conditions. High expression of PKB/Akt was found to be associated with tolerance for nutrient starvation. When Akt antisense RNA expression vectors were introduced into PANC-1 cells, the tolerance was partially but significantly diminished by vectors for Akt1 and Akt2 but not Akt3. Because elimination of the tolerance might serve as a new strategy for cancer therapy, several compounds were tested for this purpose, and troglitazone, an insulin sensitizer, as well as LY294002, a phosphatidylinositol 3-kinase inhibitor, were found to kill PANC-1 cells only under nutrient starvation conditions.
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PMID:Remarkable tolerance of tumor cells to nutrient deprivation: possible new biochemical target for cancer therapy. 1108 46

The tumor suppressor PTEN is a dual protein and phosphoinositide phosphatase that negatively controls the phosphatidylinositol (PI) 3-kinase/protein kinase B (Akt/PKB) signaling pathway. Interleukin-13 via the activation of the class I PI 3-kinase has been shown to inhibit the macroautophagic pathway in the human colon cancer HT-29 cells. Here we demonstrate that the wild-type PTEN is expressed in this cell line. Its overexpression directed by an inducible promoter counteracts the interleukin-13 down-regulation of macroautophagy. This effect was dependent upon the phosphoinositide phosphatase activity of PTEN as determined by using the mutant G129E, which has only protein phosphatase activity. The role of Akt/PKB in the signaling control of interleukin-13-dependent macroautophagy was investigated by expressing a constitutively active form of the kinase ((Myr)PKB). Under these conditions a dramatic inhibition of macroautophagy was observed. By contrast a high rate of autophagy was observed in cells expressing a dominant negative form of PKB. These data demonstrate that the signaling control of macroautophagy overlaps with the well known PI 3-kinase/PKB survival pathway and that the loss of PTEN function in cancer cells inhibits a major catabolic pathway.
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PMID:The tumor suppressor PTEN positively regulates macroautophagy by inhibiting the phosphatidylinositol 3-kinase/protein kinase B pathway. 1147 64

Autophagy is a major catabolic process allowing the renewal of intracellular organelles by which cells maintain their homeostasis. We have previously shown that autophagy is controlled by two transduction pathways mediated by a heterotrimeric Gi3 protein and phosphatidylinositol 3-kinase activities in the human colon cancer cell line HT-29. Here, we show that 3-methyladenine, an inhibitor of autophagy, increases the sensitivity of HT-29 cells to apoptosis induced by sulindac sulfide, a nonsteroidal anti-inflammatory drug which inhibits the cyclooxygenases. Similarly, HT-29 cells overexpressing a GTPase-deficient mutant of the G(alpha i3) protein (Q204L), which have a low rate of autophagy, were more sensitive to sulindac sulfide-induced apoptosis than parental HT-29 cells. In both cell populations we did not observe differences in the expression patterns of COX-2, Bcl-2, Bcl(XL), Bax, and Akt/PKB activity. However, the rate of cytochrome c release was higher in Q204L-overexpressing cells than in HT-29 cells. These results suggest that autophagy could retard apoptosis in colon cancer cells by sequestering mitochondrial death-promoting factors such as cytochrome c.
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PMID:Autophagy delays sulindac sulfide-induced apoptosis in the human intestinal colon cancer cell line HT-29. 1147 40

Molecular mechanisms associated with tumor metastasis remain poorly understood. Here we report that acquired expression of periostin by colon cancer cells greatly promoted metastatic development of colon tumors. Periostin is overexpressed in more than 80% of human colon cancers examined with highest expression in metastatic tumors. Periostin expression dramatically enhanced metastatic growth of colon cancer by both preventing stress-induced apoptosis in the cancer cells and augmenting endothelial cell survival to promote angiogenesis. At the molecular level, periostin activated the Akt/PKB signaling pathway through the alpha(v)beta(3) integrins to increase cellular survival. These data demonstrated that the survival-promoting function is crucial for periostin to promote tumor metastasis of colon cancer.
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PMID:Periostin potently promotes metastatic growth of colon cancer by augmenting cell survival via the Akt/PKB pathway. 2575 31

It has been shown that in hereditary and most sporadic colon tumours, components of the Wnt pathway are mutated. The Wnt target MET has been implicated in the development of colon cancer. Here, we show that overexpression of wild-type or a constitutively activated form of MET in colon epithelial cells leads to increased transformation irrespective of Wnt signalling. Fetal human colon epithelial cells without aberrant Wnt signalling were transfected with wild-type or mutated MET constructs. Expression of these constructs leads to increased phosphorylation of MET and its downstream targets PKB and MAPK. Upon stimulation with HGF, the expression of E-cadherin is downregulated in wild-type MET-transfected cells, whereas cells expressing mutated MET show low E-cadherin levels independent of stimulation with ligand. This implies a higher migratory propensity of these cells. Furthermore, fetal human colon epithelial cells expressing the mutated form of MET have colony-forming capacity in soft agar, while cells expressing wild-type MET show an intermediate phenotype. Subcutaneous injection of mutated MET-transfected cells in nude mice leads to the formation of tumours within 12 days in all mice injected. At this time point, mock-transfected cells do not form tumours, while wild-type MET-transfected cells form subcutaneous tumours in one out of five mice. We thus show that MET signalling can lead to increased transformation of colon epithelial cells independent of Wnt signalling and in this way could play an essential role in the onset and progression of colorectal cancer.
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PMID:MET signalling in primary colon epithelial cells leads to increased transformation irrespective of aberrant Wnt signalling. 1578 35

The search for effective chemopreventive compounds is a major challenge facing research into preventing the progression of cancer cells. The naturally occurring polyphenol antioxidants look very promising, but their mechanism of action still remains poorly understood. Here, we show that 2-(3,4-dihydroxyphenyl)ethanol (DPE), a phenol antioxidant derived from olive oil, induces growth arrest and apoptosis in human colon carcinoma HT-29 cells. The mechanisms involve prolonged stress of the endoplasmic reticulum (ER) leading to the activation of the two main branches of the unfolded protein response (UPR), including the Ire1/XBP-1/GRP78/Bip and PERK/eIF2alpha arms. DPE treatment led to overexpression of the pro-apoptotic factor CHOP/GADD153 and persistent activation of the Jun-NH2-terminal kinase/activator protein-1 signaling pathway. DPE concomitantly modulated the extracellular signal-regulated kinase 1/2 and Akt/PKB pro-survival factors by altering their phosphorylation status as well as inhibiting tumor necrosis factor-alpha-induced nuclear factor-kappaB activation by inactivating the phosphorylation of nuclear factor inhibitor-kappaB kinase. These findings prompted us to investigate the possible involvement of phosphatases in DPE-mediated action. Using phosphatase inhibitors and RNA interference to silence the Ser/Thr phosphatase 2A (PP2A) prevented DPE-induced cell death. These findings demonstrate that DPE specifically activates PP2A, which plays a key initiating role in various pathways that lead to apoptosis in colon cancer cells.
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PMID:Dihydroxyphenylethanol induces apoptosis by activating serine/threonine protein phosphatase PP2A and promotes the endoplasmic reticulum stress response in human colon carcinoma cells. 1652 88

The aim of this investigation was to evaluate the chemopreventative/antiproliferative potential of a grape seed proanthocyanidin extract (GSPE) against colon cancer cells (CaCo2 cells) and to investigate its mechanism of action. GSPE (10-100 microg/ml) significantly inhibited cell viability and increased apoptosis in CaCo2 cells, but did not alter viability in the normal colon cell line (NCM460). The increased apoptosis observed in GSPE-treated CaCo2 cells correlated with an attenuation of PI3-kinase (p110 and p85 subunits) and decreased PKB Ser(473) phosphorylation. GSPE might thus exert its beneficial effects by means of increased apoptosis and suppression of the important PI3-kinase survival-related pathway.
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PMID:Proanthocyanidin from grape seeds inactivates the PI3-kinase/PKB pathway and induces apoptosis in a colon cancer cell line. 1792 79

Peroxisome proliferator-activated receptor gamma (PPAR gamma) are members of the largest nuclear hormone receptor family of transcription factors (1). PPAR gamma (PPARgamma) plays an important role in adipogenesis, control of sensitivity to insulin, inflammation and atherosclerosis but recent studies also suggest that PPARgamma is involved in cell cycle withdrawal. PPARgamma can promote cell differentiation, exert an antiproliferative action and inhibit angiogenesis (2, 3). However, there are studies showing that activation of PPARgamma promotes the development of colon cancer (4). These data are in sharp contrast with studies that attribute anticancer effects to PPARgamma in gastrointestinal malignancies. Probably, the action of PPARgamma on cell cycle and proliferation depends on the cell type and presence of other stimuli that predispose cells to cancer development. Amidated and non-amidated gastrins may play an important role in the proliferation and carcinogenesis of GI cancers. It is known that gastrin peptides activate phosphorylation of Protein Kinase B (PKB/Akt) and anti-apoptotic signalling but there is little known about the link between gastrins and PPARgamma receptors in relation to apoptosis.
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PMID:Transcriptional upregulation of gastrin in response to peroxisome proliferator-activated receptor gamma agonist triggers cell survival pathways. 1819 88

Periostin is a secreted protein and has been shown to be frequently overexpressed in various types of human cancers. We have previously reported that periostin potently promotes metastatic growth of colon cancer by augmenting cell survival. However, little is known about the functions of periostin in non-small-cell lung cancer. Here, we revealed that increased expression of periostin in non-small-cell lung cancer A549 cells was one kind of cellular responses to the stress of chemical-mimic hypoxia, and this effect could be regulated by hypoxia inducible growth factors, such as TGF-alpha and bFGF. We further demonstrated that RTK/PI3-K pathway activated by TGF-alpha and bFGF was evoked in upregulating the expression of periostin, and then periostin promoted the survival of A549 cells under hypoxic microenvironment via activation of Akt/PKB pathway. Therefore, periostin and the pathway that it involved might provide a target for lung cancer treatment.
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PMID:Upregulated expression of periostin by hypoxia in non-small-cell lung cancer cells promotes cell survival via the Akt/PKB pathway. 1932 25


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