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

Human colon cancer cells produce and secrete a variety of polypeptide growth factors. The functional role of these growth factors, however, is poorly understood. Though the secretion of epidermal growth factor (EGF)-like activity and EGF-related molecules by human colon cancer cells in culture has been reported, it is not known whether colon cancer cells produce and secrete EGF, and the functional role of EGF in the growth control of these cells is also unknown. We have shown that EGF acts as a potent growth stimulator on the moderately differentiated Moser colon cancer cell line and as an inhibitor on the highly metastatic KM12SM cell line. In the present study, we show that EGF is produced by human colon cancer cells and characterize the levels of EGF mRNA expression and EGF protein secretion from 8 human colon cancer cell lines. The cell-surface EGF receptors on these cell lines were also characterized by radiolabeled ligand binding and Scatchard analyses. All the cell lines expressed EGF mRNA and secreted EGF. Both high- and low-affinity subtypes of EGF receptor were detected on 7 of the cell lines. These lines also secreted transforming growth factor (TGF)alpha. Some cell lines exhibited a proliferative response to treatment with either exogenous EGF or TGF alpha, while others did not respond to treatment with these growth factors. Antibody-blocking experiments, using anti-EGF or anti-EGF receptor antibody, suggested that these cell lines could be broadly classified into 2 groups in terms of their autocrine or paracrine growth regulation via the cell-surface EGF receptor: (1) cells that utilized EGF and/or TGF alpha; and (2) cells that did not utilize EGF or TGF alpha (via the cell-surface receptor), even though they secreted abundant amounts of these growth factors.
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PMID:Proliferation of human colon cancer cells: role of epidermal growth factor and transforming growth factor alpha. 145 40

Analogues of somatostatin (SS) and luteinizing hormone-releasing hormone (LH-RH) activate tyrosine phosphatases in MIA PaCa-2 human pancreatic cancer cell line membranes and inhibit growth. We compared the substrates phosphorylated by epidermal growth factor (EGF) to those dephosphorylated by the SS analogue RC-160 (D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2) and [D-Trp6]LH-RH in cancer cell lines such as MIA PaCa-2 (human pancreatic cancer), HCPC (hamster cheek pouch carcinoma), A-549 (human lung cancer), HT-29 (human colon cancer), and R3230AC (breast cancer). EGF phosphorylated proteins of 170, 65, and 60 kDa and analogues of SS and LH-RH promoted the dephosphorylation of these proteins in MIA PaCa-2 and HCPC cell lines. The EGF receptor is 170 kDa. pp60src (60 kDa) is known to be a substrate for EGF receptor. The LH-RH receptor is also 60 kDa. The effects of RC-160 and [D-Trp6]LH-RH were quantitatively different. Examinations of HT-29, A-549, and R3230AC cancer cell lines revealed no phosphorylation by EGF or dephosphorylation by RC-160 and [D-Trp6]LH-RH. In addition to the 170-, 65-, and 60-kDa proteins, 35-kDa proteins were also phosphorylated in some cancer cell lines. This work demonstrates that analogues of SS and LH-RH can reverse the effects of EGF biochemically as well as functionally.
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PMID:Effects of epidermal growth factor and analogues of luteinizing hormone-releasing hormone and somatostatin on phosphorylation and dephosphorylation of tyrosine residues of specific protein substrates in various tumors. 167 42

Amphiregulin (AR) and cripto are proteins that are structurally related to epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha). AR is also functionally related to this family of growth regulatory molecules and is able to bind and activate the 170-kDa EGF receptor (EGFR). Human EGFR-3 (HER3)/ERBB3 is a recently identified protein related to the EGFR that is widely expressed in breast carcinomas and is a candidate receptor for EGF-like growth factors. Differential expression of these putative ligands and receptors in transformed cells suggests that they may function in an autocrine manner to regulate tumor cell growth. Specific mRNA transcripts for TGF-alpha [4.8 kilobases (kb)], AR (1.4 kb), cripto (2.2 kb), and HER3 (6.2 kb) were expressed in a majority of human colon cancer cell lines. HER3 mRNA was detected in 55% of primary or metastatic human colorectal carcinomas but in only 22% of normal colon mucosa and 32% of normal liver samples. In contrast, cripto and AR mRNA were expressed in 60-70% of primary or metastatic human colorectal cancers but in only 2-7% of normal human colonic mucosa. Immunostaining also detected AR protein in primary and metastatic colorectal tumors but not in normal colon or uninvolved liver. These findings suggest that cripto and AR may be useful markers to discriminate between normal and malignant colonic epithelium and may provide a selective growth advantage for colorectal carcinomas.
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PMID:Differential expression of epidermal growth factor-related proteins in human colorectal tumors. 171 80

A cDNA encoding transforming growth factor type alpha (TGF alpha) was fused to the 5' end of a gene encoding a modified form of Pseudomonas exotoxin A (PE), which is devoid of the cell recognition domain (domain Ia). The chimeric molecule, termed TGF alpha-PE40, was expressed in Escherichia coli and isolated from the periplasm or inclusion bodies depending on the construction expressed. TGF alpha-PE40 was found to be extremely cytotoxic to cells displaying epidermal growth factor (EGF) receptors. Comparison with a similar molecule in which TGF alpha was placed at the carboxyl end of PE40 demonstrated the importance of the position of the cell recognition element; TGF alpha-PE40 was found to be about 30-fold more cytotoxic to cells bearing EGF receptors than PE40-TGF alpha. In addition, TGF alpha-PE40 was shown to be extremely cytotoxic to a variety of cancer cell lines including liver, ovarian, and colon cancer cell lines, indicating high levels of EGF receptor expression in these cells.
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PMID:Cytotoxic activities of a fusion protein comprised of TGF alpha and Pseudomonas exotoxin. 255 14

Three human colon cancer lines (SW480, SW620, WIDR) secrete different levels of transforming growth factor beta (TGF beta)-like and transforming growth factor alpha (TGF alpha)/epidermal growth factor (EGF)-like molecules into serum-free conditioned media as measured by competing activity in TGF beta and EGF radioreceptor assays. SW480 cells, the highest producers of TGF beta-like activity, lack detectable TGF beta receptors while SW620 cells, the highest producers of TGF alpha/EGF-like activity, lack EGF receptors. This study investigated the production of these growth factors at the mRNA level and examined the mechanism of loss of detectable receptors. Using complementary DNA probes for TGF beta and TGF alpha, it was demonstrated that mRNA levels correlated with the amounts of TGF beta and TGF alpha produced; TGF beta gene expression was highest in SW480 cells and TGF alpha gene expression was highest in SW620 cells. Acid washing of the SW480 cells prior to performing the TGF beta binding assay resulted in the unmasking of substantial levels of TGF beta receptors. Neither acid washing nor preincubation with suramin uncovered EGF receptors in SW620 cells. Also, and in contrast to the other two lines, EGF receptor expression could not be detected in SW620 cells by Northern gel analysis of receptor messenger RNA or by immunological analysis of receptor protein. Thus two distinct mechanisms (occupation of TGF beta receptor in SW480 cells, or absence of EGF receptor in SW620 cells) explain the lack of detectable TGF beta and EGF receptors in the binding assays. The autocrine hypothesis remains viable for TGF beta in SW480 cells but not for TGF alpha in SW620 cells; this would not discount a paracrine role in this latter case.
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PMID:Transforming growth factor alpha and beta expression in human colon cancer lines: implications for an autocrine model. 288 81

The human colon cancer cell line HT-29 produces a growth factor (CRDGF; Mr = 25,000) which inhibits EGF binding to a wide variety of different normal and tumoral cell types in culture. Scatchard analysis of EGF binding shows that CRDGF induces a decrease in EGF receptor affinity. In contrast, EGF binding to any of the human colorectal cancer cell lines tested, i.e., HT-29, HT-29 (clone D4), HRT-18 or CAL-14, remains unaltered in the presence of exogenous CRDGF. However, the inhibitory effect of CRDGF becomes apparent on HT-29 cells after overnight exposure of these to suramin (at 37 degrees C). A short exposure to suramin (1 hr at 4 degrees C) or a mild acid washing of HT-29 cells can partially restore the inhibitory activity of CRDGF. These observations suggest that the action of suramin results in an unmasking of substantial levels of CRDGF receptors on HT-29 cells. Scatchard analysis of EGF binding on suramin-treated HT-29 cells shows that CRDGF inhibits EGF binding by decreasing EGF receptor affinity, as previously observed with the non-colonic cell types. A similar unmasking of CRDGF receptors is observed when the other colorectal cell lines are exposed to suramin. These results provide evidence for a model in which the colorectal cell lines have the property of secreting a unique growth factor that binds to its receptor by an autocrine mechanism.
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PMID:Autocrine secretion of a colorectum-derived growth factor by HT-29 human colon carcinoma cell line. 326 53

Six colon cancer cell lines, 13 colon tumors and ten normal colon tissues were analyzed for RNA expression using probes for c-myc, c-k-ras, c-myb, and c-fos and for the p53, TGF-alpha, and EGF receptor genes. No aberrant transcripts were detected. Levels of expression in tumors ranged from two-fold below that of normal tissue when the v-fos probe was used to 10 fold above the normal level when the c-myc probe was used. Enhanced c-myc expression was also observed in the cell lines. Southern and DNA dot blot analyses revealed c-myc amplification in three of the six cell lines.
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PMID:Oncogene expression in adenocarcinomas of the colon and in colon tumor-derived cell lines. 328 75

Human colon cancer cell lines express epidermal growth factor (EGF) mRNA, secrete EGF and may respond to it via the cell-surface EGF receptor (EGFR). Expression of these molecules in human colon and colon tumor, however, is not clear. Reverse transcription-polymerase chain reaction (RT-PCR) analyses of RNA prepared from paired normal human colon and colon tumor samples from 12 individuals followed by Southern blotting analyses of the RT-PCR products revealed a major fragment of 527 bp and a minor fragment of 404 bp that hybridized to a human EGF cDNA probe under stringent conditions. Identical results were obtained from 8 human colon cancer cell lines. Cloning and sequencing of PCR products confirmed that both fragments were from the human EGF gene; the 527-bp fragment corresponded exactly to nucleotides 2,891 to 3,417 of the human EGF mRNA reported by others. A deletion of 123 nucleotides (nucleotides 3,172 to 3,294) was found in the 404-bp fragment. Immunohistochemical studies using cyostat sections of human colon specimens showed that EGF was expressed in the human colon and that expression was restricted to the epithelial colonic crypt cells and epithelium-derived cancer cells. Since EGF and EGF-related molecules are potent mitogens that mediated their effect through the EGFR, we also determined the efficacy of anti-sense EGFR RNA in circumventing the EGFR-related pathway of proliferation. Expression of anti-sense EGFR RNA, by transfection with an inducible anti-sense EGFR expression vector, down-regulated cell-surface EGFR expression and proliferation of these cells and their ability to grow in soft agar. Anti-sense EGFR RNA was found to be an anti-proliferative agent in both relatively non-aggressive and highly aggressive human colon cancer cells.
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PMID:Epidermal growth factor expression in human colon and colon carcinomas: anti-sense epidermal growth factor receptor RNA down-regulates the proliferation of human colon cancer cells. 755 11

Two morphologically distinct cell lines, GP2d and GP5d, derived from the same adenocarcinoma of the colon, have been established and characterised. Both clones have the same genetic changes, consistent with the usual pattern of tumour progression in colon cancer. The cells also have an inverted duplication of bands 10q11 to 10q21, but Southern blot analysis failed to identify any translocations involving the ret protooncogene, which maps to this region. GP2d grew by spreading from the edges of microcolonies to form a confluent layer of cells. GP5d grew in discrete islands of cells forming multi-layered colonies. These differing patterns of growth correlated with variation in expression or cellular distribution of alpha 2-integrin, desmoplakin and e-cadherin. Only GP2d responded to exogenously added epidermal growth factor (EGF), transforming growth factor-alpha (TGF alpha) or insulin with an increase in cell numbers, even though both cell lines possessed similar numbers of EGF receptors. Analysis of EGF receptor ligand expression showed that GP5d cells expressed relatively more TGF alpha mRNA than did GP2d; in contrast, amphiregulin mRNA, which was abundant in GP2d, was virtually undetectable in GP5d. Even though GP5d failed to exhibit a growth response to EGF, it underwent a marked epithelial-mesenchymal transition when treated with EGF, indicating separation of growth and morphological responses to EGF.
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PMID:Two newly established cell lines derived from the same colonic adenocarcinoma exhibit differences in EGF-receptor ligand and adhesion molecule expression. 760 66

In this article we have reviewed and discussed the results of our investigation of lipid metabolites as modulators of epidermal growth factor (EGF) signaling pathways. We have studied epidermal growth factor-dependent mitogenesis in BALB/c 3T3 and Syrian hamster embryo (SHE) cells in culture. We observed that EGF stimulates the formation of prostaglandins in BALB/c 3T3 cells and their formation appears to be necessary for EGF dependent mitogenesis. EGF did not stimulate PGE2 formation in SHE cells and in fact, exogenously added PGE2 inhibited mitogenesis. In both cell lines, EGF stimulated the formation of lipoxygenase-derived 13(S)-hydroxyoctadecadienoic acid (13-HODE) and inhibition of 13-HODE formation attenuated mitogenesis. The addition of 13-(S)-HODE enhanced EGF-dependent mitogenesis but when added alone, the compound was not mitogenic. Other metabolites, including lipoxygenase metabolites of arachidonic acid, were either weak simulators of EGF-dependent mitogenesis or essentially inactive. The 13(S)-HODE appears to be formed by an apparently unique lipoxygenase that is regulated by the tyrosine kinase activity of the EGF receptor. The mechanisms by which lipids, particularly the lipoxygenase-derived linoleic acid metabolites, modulate the EGF signaling pathways leading to cell proliferation is discussed. The possible significance of lipoxygenase and prostaglandin H synthase-dependent metabolism of unsaturated fatty acids in breast and colon cancer is also discussed.
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PMID:Cellular proliferation and lipid metabolism: importance of lipoxygenases in modulating epidermal growth factor-dependent mitogenesis. 771 98


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