Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytoplasmic sequestration of the p53 tumor suppresser protein has been proposed as a mechanism involved in abolishing p53 function. However, the mechanisms regulating p53 subcellular localization remain unclear. In this report, we analyzed the possible existence of cis-acting sequences involved in intracellular trafficking of the p53 protein. To study p53 trafficking, the jellyfish green fluorescent protein (GFP) was fused to the wild-type or mutated p53 proteins for fast and sensitive analysis of protein localization in human MCF-7 breast cancer, RKO colon cancer, and SAOS-2 sarcoma cells. The wild-type p53/GFP fusion protein was localized in the cytoplasm, the nucleus, or both compartments in a subset of the cells. Mutagenesis analysis demonstrated that a single amino acid mutation of Lys-305 (mt p53) caused cytoplasmic sequestration of the p53 protein in the MCF-7 and RKO cells, whereas the fusion protein was distributed in both the cytoplasm and the nucleus of SAOS-2 cells. In SAOS-2 cells, the mutant p53 was a less efficient inducer of p21/CIP1/WAF1 expression. Cytoplasmic sequestration of the mt p53 was dependent upon the C-terminal region (residues 326-355) of the protein. These results indicated the involvement of cis-acting sequences in the regulation of p53 subcellular localization. Lys-305 is needed for nuclear import of p53 protein, and amino acid residues 326-355 can sequester mt p53 in the cytoplasm.
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PMID:Cooperation of a single lysine mutation and a C-terminal domain in the cytoplasmic sequestration of the p53 protein. 967 15

Recently, apoptosis has been implicated as one of the end points of cells exposed to chemotherapeutic agents. The p53 and Bcl-2 family of proteins are involved in chemotherapy-induced apoptosis, but in a cell type-dependent manner. We sought to determine the roles played by the p53 and Bcl-2 family of proteins in 5-fluorouracil (5-FU)-induced apoptosis of human colon cancer cell lines. We first studied the p53 genetic and functional status, and then 5-FU, at inhibitory concentration of 50% (IC50) doses, was used to induce apoptosis, which was confirmed by morphological analysis and enzyme-linked immunosorbent assay (ELISA). Bcl-2, Bcl-X(L), Bax, Bad, Bak and p53 protein expression was analysed by Western blotting. Using five human colon cancer cell lines, we found that equitoxic (IC50) doses of 5-FU induced apoptosis in both wild-type p53 and mutant p53 cells. Analysis of the steady-state levels of Bcl-2 family proteins showed high expression of Bcl-X(L) in all of the cell lines except Colo320. Bcl-2 was expressed in two of them. Bax presented with the lowest basal expression and Bad showed homogeneous expression. On the other hand, Bak expression varied more than fivefold among these cells. In cells containing wild-type p53 (e.g. LoVo), 5-FU-induced apoptosis was accompanied by increased expression of Bax and Bak without consistent modulation of other bcl-2 family proteins. In contrast in cells containing mutant p53 (e.g. DLD1), Bak expression was remarkably increased. There was a significant correlation between chemosensitivity and Bcl-X(L) to Bax ratio, rather than Bcl-2 to Bax. In conclusion, these results suggest that some members of the Bcl-2 family of proteins, in human colon cancer cell lines, are modulated by 5-FU and that the ratio of Bcl-X(L) to Bax may be related to chemosensitivity to 5-FU.
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PMID:5-Fluorouracil induces apoptosis in human colon cancer cell lines with modulation of Bcl-2 family proteins. 979 40

We have introduced an inducible wild-type p53 allele into the human SW480 colon cancer cell line, which bears an endogenous mutant p53 allele. The expression of inducible wild-type p53 is under basal repression by the lac repressor and is induced by isopropyl-beta-thiogalactopyranoside. The addition of isopropyl-beta-thiogalactopyranoside induces expression of wild-type p53 transcript and protein at a level no greater than that of the endogenous mutant p53. This level of wild-type p53 induction is sufficient both to induce expression of WAF1/CIP1 and to induce G1 cell cycle arrest. This p53-induced growth arrest is reversible after 6 days of continuous p53 expression, indicating that apoptosis is not induced. These results demonstrate that in a human colon epithelial cell background, wild-type p53 is functionally dominant over this mutant p53 and thus provides a mechanism for the observed inactivation of both copies of the p53 gene in most colon cancers. Moreover, despite the well-documented role of apoptosis in maintaining homeostasis in the nontransformed colon epithelium, these results demonstrate that restoration of wild-type p53 expression is insufficient to trigger apoptosis of transformed colonic cells.
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PMID:Wild-type p53 demonstrates functional dominance in a human colon carcinoma cell line in which it induces reversible growth arrest. 981 11

Wild-type p53 is induced by DNA damage. In different cell types, this induction is suggested either to facilitate DNA repair by inducing a cell cycle pause or to potentiate cell death via apoptosis. Wild-type p53 in different cell types has similarly been associated with either enhancement of or increased resistance to the cytotoxicity of many cancer therapeutic agents. We have constructed a colorectal cancer cell line bearing, in addition to endogenous mutant p53 alleles, an exogenous wild-type p53 allele that is under the regulatable control of the lac repressor. Induction of wild-type p53 by isopropyl-beta-thiogalactopyranoside in these cells induces a reversible growth arrest but does not induce cell death. However, we find that the induction of wild-type p53 powerfully potentiates the cytotoxicity of both irradiation and 5-fluorouracil, two agents that are used clinically in the treatment of colorectal cancer. We also find that induction of wild-type p53 potentiates the cytotoxicity of topotecan, a member of the camptothecin family of drugs that also has clinical activity against colon cancer. These findings suggest that the common loss of wild-type p53 in many colorectal cancers may play a role in the clinical resistance of these tumors to anticancer agents. Although some cancer cells may not be directly killed by p53 gene therapy, our findings suggest that genetic alteration of some cancers to induce wild-type p53 may increase their sensitivity to cytotoxic gene therapy.
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PMID:Wild-type p53 protein potentiates cytotoxicity of therapeutic agents in human colon cancer cells. 981 12

In various types of human malignant tumors, the presence or absence of expression of apoptosis-associated gene products (p53 protein and Bcl-2 protein) and the tumor proliferation activity-related factor (Ki-67) was assessed by immunohistochemical staining and the correlation between this expression and chemosensitivity to anticancer drugs was investigated. Study subjects comprised 55 preoperative patients with untreated malignant tumors (9 with esophageal cancer, 11 with stomach cancer, 11 with colon cancer, 13 with hepatic cancer and 11 with breast cancer). A chemosensitivity test was carried out with the histoculture drug response assay (HDRA) method using 4 drugs, mitomycin C (MMC), 5-fluorouracil (5-FU), doxorubicin hydrochloride (ADM), and cisplatin (CDDP). Immunohistochemical staining was used to assess expression of p53 protein, Bcl-2 protein and Ki-67. The tumor growth inhibition index (I.I.) of the 4 drugs was significantly lower in a group of the patients with p53 protein overexpression-type (mutant p53 protein positive expression-type) tumors than in a group with p53 protein negative expression-type tumors (p<0.05). No significant correlation was found between the expression of the Bcl-2 protein by and the I.I. of any drug studied in any type of cancer. A negative correlation was found between the labeling index (L.I.) for Ki-67 in all cases and I.I. for MMC and ADM and thus, chemosensitivity of the tumors with high growth activity was lower. Furthermore, a positive correlation existed between the L.I. for Ki-67 and that for p53 protein. The patients with p53 protein overexpression-type (mutant p53 protein positive) tumors showed low chemosensitivity. In addition, overexpression of p53 protein is suggested to be one of the factors involved in the lowered chemosensitivity of the tumors with high growth activity. Summarizing these findings, the p53 protein can play an important role in cancer therapy.
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PMID:Usefulness of p53 protein, Bcl-2 protein and Ki-67 as predictors of chemosensitivity of malignant tumors. 1020 14

An ultra-high metastatic model of human colon cancer was developed in order to represent highly malignant patient disease for which there is no current model. Surgical orthotopic implantation (SOI) of a histologically intact liver metastasis fragment derived from a surgical specimen of a patient with metastatic colon cancer was initially implanted in the colon, liver and subcutaneously in nude mice. This tumor did not metastasize for the first 10 passages. At the eleventh passage, the tumor exhibited metastasis from the colon to the liver, spleen, and lymph nodes. At this time, two selective passages were carried out by transplanting resulting liver metastases in the nude mice to the colon of additional nude mice. After these two passages, the tumor became stably ultra-metastatic and was termed AC3488UM. One-hundred percent of mice transplanted with AC3488UM with SOI to the colon exhibited local growth, regional invasion, and spontaneous metastasis to the liver, lymph nodes, and spleen. While the maximum size of the primary tumor was 0.9 g, the metastatic liver was over 9 times the weight of the normal liver with the maximum weight of the metastatic liver over 12 g. Liver metastases were detected by the tenth day after transplantation in all animals. Half the animals died of metastatic tumor 25 days after transplantation. Histological characteristics of AC3488UM tumor were poorly differentiated adenocarcinoma of colon. Mutant p53 is expressed heterogeneously in the primary tumor and more homogeneously in the liver metastasis suggesting a possible role of p53 in the liver metastasis. The human origin of AC3488UM was confirmed by positive fluorescence staining for in situ hybridization of human DNA. The AC3488 human colon-tumor model with its ultra-high metastatic capability in each transplanted animal, short latency and a short median survival period is different from any known human colon cancer model and will be an important tool for the study of and development of new therapy for highly metastatic human colon cancer.
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PMID:An ultra-metastatic model of human colon cancer in nude mice. 1039 Jan 46

Two common genetic alterations in colon carcinoma, p53 mutation and microsatellite instability (MSI), were investigated to determine their prognostic importance for cancer-specific survival and response to adjuvant chemotherapy in patients with Dukes' C colon cancer. The p53 tumour suppressor gene encodes for a nuclear phosphoprotein involved in cellular response to DNA damage, while MSI is a characteristic feature of tumours with defective DNA mismatch repair. The cellular response mechanisms to DNA-damaging agents in tumours with mutant p53 or MSI may as a consequence differ, and this might translate into different outcomes following adjuvant chemotherapy. A consecutive series of 388 Dukes' C colon carcinomas with 5-year median follow-up was analysed for p53 mutation and for MSI (in proximal/transverse carcinomas only) using polymerase chain reaction single-strand conformation polymorphism. The incidence of p53 mutation was 28% in all carcinomas while that of MSI in proximal/transverse carcinomas was 19%. One hundred and thirty-three patients (34%) received adjuvant chemotherapy (5-fluorouracil/levamisole) with curative intent. The presence of p53 mutation did not predict for survival in either the treated or untreated groups. The presence of MSI in the proximal/transverse colon carcinoma group was associated with significantly better 5-year survival: 58 versus 32% (p = 0.015, log rank test). This was largely due to better survival observed in the MSI subgroup that received adjuvant chemotherapy (p = 0.017, log rank test). Further work in prospective, randomised clinical trials investigating the effects of adjuvant therapy should consider incorporating MSI status in order to determine whether this is an independent predictive factor for survival and/or response to adjuvant chemotherapy.
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PMID:p53 gene mutation, microsatellite instability and adjuvant chemotherapy: impact on survival of 388 patients with Dukes' C colon carcinoma. 1064 41

Genetic lesions in the p53 tumor suppressor gene are the most frequently observed alterations in human cancers. Typically in tumors, one allele of the p53 gene is initially mutated, followed by deletion of the remaining wildtype allele. In human colon cancer, for example, approximately 70% of late stage tumors are hemizygous mutant p53. Since the precise gene environment surrounding the p53 gene is not known, the neighboring genes concomitantly lost with wildtype p53 deletion remain undetermined. A restriction enzyme map and clone array of 1.1 Mb surrounding the p53 gene were constructed using a combination of YAC, BAC, NotI linking, and NotI jumping clones. The resulting physical map and clone array include approximately 400 kb telomeric and 700 kb centromeric to the p53 gene. Sequence determination and analysis adjacent to NotI and AscI sites, indicative of CpG islands, allowed the rapid identification of numerous genes within the cloned region. Twenty-seven transcription units were identified, including 18 characterized genes. Limited analysis of primary human colon tumors, hemizygous for the p53 gene, indicates loss of the entire 1.1-Mb region upon deletion of wildtype p53.
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PMID:Physical map of 17p13 and the genes adjacent to p53. 1066 45

Photodynamic therapy (PDT) using the silicon phthalocyanine photosensitizer Pc 4 [HOSiPcOSi(CH3)2(CH2)3N-(CH3)2] is an oxidative stress associated with induction of apoptosis in various cell types. We assessed the effectiveness of Pc 4-PDT on SW480 colon cancer xenografts grown in athymic nude mice. Animals bearing xenografts were treated with 1 mg/kg body weight Pc 4 and 48 h later were irradiated with 150 J/cm2 672-nm light from a diode laser delivered at 150 mW/cm2. Biochemical studies were performed in xenografts resected at various time points up to 26 h after Pc 4-PDT treatment, whereas tumor size was evaluated over a 4-week period in parallel experiments. In the tumors resected for biochemical studies, apoptosis was visualized by activation of caspase-9 and caspase-3 and a gradual increase in the cleavage of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) to a maximum of approximately 60% of the total PARP present at approximately 26 h. At that time all Pc 4-PDT-treated tumors had regressed significantly. Two signaling responses that have previously been shown to be associated with Pc 4-PDT-induced apoptosis in cultured cells, p38 mitogen-activated protein kinase and p21/WAF1/Cip1, were examined. A marked increase in phosphorylation of p38 was observed within 1 h after Pc 4-PDT without changes in levels of the p38 protein. Levels of p21 were not altered in the xenografts in correspondence with the presence of mutant p53 in SW480 cells. Evaluation of tumor size showed that tumor growth resumed after a delay of 9-15 days. Our results suggest that: (a) Pc 4-PDT is effective in the treatment of SW480 human colon cancer xenografts independent of p53 status; (b) PARP cleavage may be mediated by caspase-9 and caspase-3 activation in the Pc 4-PDT-treated tumors; and (c) p38 phosphorylation may be a trigger of apoptosis in response to PDT in vivo in this tumor model.
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PMID:Photodynamic therapy with the phthalocyanine photosensitizer Pc 4 of SW480 human colon cancer xenografts in athymic mice. 1081 28

KILLER/DR5 is a death-domain-containing proapoptotic receptor that binds to the cytotoxic ligand TRAIL. It was originally reported that induction of KILLER/DR5 mRNA following DNA damage was p53-dependent, but some drugs that induce apoptosis can upregulate KILLER/DR5 mRNA expression in cell lines with mutated p53. We further extend those findings by classifying the capability of various apoptosis-inducing drugs to increase the expression of KILLER/DR5 mRNA in a p53-independent manner. beta-Lapachone, a topoisomerase inhibitor, increased KILLER/DR5 mRNA in colon cancer cell lines with wild-type p53 but not with mutant p53. In contrast, betulinic acid, a novel chemotherapeutic compound, induced apoptosis and KILLER/DR5 mRNA in melanoma and glioblastoma cells through a p53-independent mechanism. The synthetic glucocorticoid dexamethasone elevated KILLER/DR5 mRNA in glioblastoma, ovarian cancer, and colon cancer cell lines with mutant p53 undergoing apoptosis, and this induction was inhibited by the transcriptional inhibitor actinomycin D. Although another glucocorticoid, prednisolone, also induced apoptosis, it did not increase KILLER/DR5 mRNA. Finally, the cytokine interferon-gamma (IFN-gamma) induced apoptosis and KILLER/DR5 in cell lines with mutant p53, and the induction of KILLER/DR5 mRNA by IFN-gamma was delayed in cells lacking wild-type STAT1, a transcription factor implicated in IFN-gamma signaling. Similarly, the induction of KILLER/DR5 mRNA by the cytokine TNF-alpha was also delayed in cell lines with mutated STAT1. These findings suggest that KILLER/DR5 may play a role in p53-independent apoptosis induced by specific drugs and warrants further investigation as a novel target for chemotherapy of tumors lacking wild-type p53.
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PMID:p53-independent upregulation of KILLER/DR5 TRAIL receptor expression by glucocorticoids and interferon-gamma. 1113 40


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