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

We found that the human colon cancer cell line SW480 consists of two distinct subpopulations which we have designated E-type (epithelial) and R-type (round). Pure cultures of each type were obtained by subcloning, and both have maintained their characteristic phenotypes for at least 1 year (40 passages). E-type cells are the major (> 98%) type in the parental SW480 cell line. They form flat epithelial-like colonies. In contrast, R-type cells, which constitute a minor fraction (< 2%) of the parental cell line, have a rounded shape and grow in clusters of piled-up cells. Compared to E-type cells or the parental SW480 cells, isolated R-type cells display decreased doubling time, loss of contact inhibition, less adhesiveness to culture plates, higher anchorage-independent growth in soft agar, and a much more aneuploid karyotype. When injected s.c. into nude mice, R-type cells produce much larger tumors within the same period of time than E-type cells, and the tumors are less differentiated than those produced by the E-type cells. Cell fusion experiments between R-type and E-type cells revealed that the R-type phenotype is dominant, and the results suggest that this is due to one or a few genetic changes. Taken together, these findings suggest that the R-type cells represent a more malignant variant of the E-type cells. They may be useful, therefore, for studying mechanisms involved in tumor progression.
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PMID:Isolation and characterization of a highly malignant variant of the SW480 human colon cancer cell line. 145 72

Tumorigenesis is a multistep process involving mutations of dominantly acting proto-oncogenes and mutations and loss-of-function mutations of tumor suppressor genes. Some of these mutations may be inherited, but most of them are acquired. Models for the sequential steps of the genetic changes involved in tumor development have been proposed for certain cancers, such as colon cancer. In the case of ovarian cancer, relatively little is known about the genetic events associated with the initiation or subsequent progression and metastases of the tumor. Cytogenetic analysis has revealed a high incidence of both structural and numerical chromosome changes, and the extent of these changes seems to increase with tumor progression. Oncogene activations of the proto-oncogenes K-ras, c-myc and c-erbB-2 have been found more frequently in aggressive ovarian tumors and may be associated with poor survival. Tumor-specific allele loss involving putative tumor suppressor genes has been observed for loci at chromosomes 11p, 17p, and 17q,--loci commonly deleted in other cancers too. A relatively high incidence of allelic loss on chromosome 6q appears to be specific to ovarian carcinoma. Familial breast/ovarian cancer has been suggested to map to chromosome 8q. Recently we have found a germ-line mutation in the tumor suppressor gene p53 in a family with breast- and ovarian cancers, indicating that this is the predisposing gene in this family. Genetic changes important for the etiology of ovarian cancers seem to involve both somatic mutations of oncogenes and somatic or germ-line inactivation of tumor suppressor genes.
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PMID:Oncogenesis in ovarian cancer. 150 89

Let me summarize by reviewing a model which is meant to raise as many questions as it answers (Fig. 2). What I have discussed today are data suggesting that during progression of solid tumors, like colon cancer, an increased cellular DNA methylating capacity characterizes the initial stages of multi-clonal hyperplasia. Despite this increase, the altered pattern of DNA methylation which subsequently emerges is largely manifest by a widespread hypomethylation of DNA. However, on a more regional basis, areas of hypermethylation appear which can affect strategic areas such as normally unmethylated CpG islands. These shifted DNA methylation patterns have the capacity to both follow, or cause, chromatin changes that can both directly silence genes critical for normal cell maturation--and/or participate in the structural chromosome changes which constitute genetic instability during tumor progression (Fig. 2). I suggest that one must view these changes as an interchangeable cycle of events during tumor progression. The chromatin changes and abnormal methylation patterns can drive one another with increasingly deleterious effects as the malignant phenotype emerges (reviewed in Baylin, 1991). What are the molecular events that would initiate the above dynamics? A working construct model is shown in Fig. 3. As discussed for the normal adult cell, there is a delicate balance between the strategic location of DNA MTase, regulation of this enzyme, and rate of DNA synthesis at replication forks (top panel, Fig. 3). In pre-neoplastic and cancer cells, perhaps failure of cells to exit the cell cycle and halt DNA replication, facilitates some sort of pressure to increase cellular DNA methyltransferase activity (bottom panel, Fig. 3). This increase may involve loss of feedback inhibition of the enzyme during the post DNA replication phase. There are also probable structural alterations in the nucleus which may alter the geographic relationship between the DNA replication fork and DNA MTase. In consequence, many DNA areas that should be getting methylated do not, and novel areas of methylation also arise. This cycle of events leads to the imbalance of DNA methylation that I have talked about. Future investigations of these possibilities, and of their specific consequences for alterations of gene expression and chromosome structure, may reveal a key molecular step underlying virtually all stages of tumor progression.
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PMID:Abnormal regional hypermethylation in cancer cells. 151 32

The initial site of disease relapse was identified for 79 patients with metastatic renal cell cancer (RCC), melanoma, colon cancer, or non-Hodgkin's lymphoma (NHL), who had achieved partial or complete responses to one of five IL-2-based immunotherapy regimens. The initial site of relapse was evenly distributed between pre-existing sites of disease (33%), new sites of disease (38%), or both (29%). There was no difference in the distribution of recurrences between patients with partial or complete responses. Fifty-one patients with prior complete or partial responses were retreated with additional IL-2-based therapy following tumor progression. Five of 51 patients retreated following relapse developed new partial responses. There were no complete responses. Three patients with NHL were retreated with IL-2 and LAK cells and all achieved a second response, while only 2 of 48 patients with other histologic diagnoses reresponded. It is concluded that after a partial or complete response to IL-2-based immunotherapy, patients who relapse do so equally at new and pre-existing sites of disease. A response to retreatment following tumor progression may be attained in patients with NHL, while a new response is unlikely for patients with melanoma and RCC.
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PMID:Relapse after response to interleukin-2-based immunotherapy: patterns of progression and response to retreatment. 179 Jan 45

Mutations in the first exon of the c-Ki-ras protooncogene were analyzed in carcinomas and dysplasias from patients with sporadic colon cancer and chronic ulcerative colitis by a combination of histological enrichment, cell sorting, polymerase catalyzed chain reaction, and direct sequencing. In contrast to sporadic colon carcinomas, where 52% (11 of 21) contained mutations in codon 12, only 1 of 28 samples of ulcerative colitis associated carcinoma or dysplasia contained a c-Ki-ras mutation, despite the presence of aneuploid cell populations. These results suggest that a different genetic pathway for tumor progression may exist between sporadic colon carcinoma and carcinomas arising in chronic ulcerative colitis.
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PMID:c-Ki-ras mutations in chronic ulcerative colitis and sporadic colon carcinoma. 219 96

The Mayo Clinic and the North Central Cancer Treatment Group (NCCTG) conducted a randomized clinical trial comparing five different combination chemotherapeutic regimens to single-agent 5-fluorouracil (5-FU), given by intravenous bolus technique (500 mg/m2 for 5 days) as a control, in the treatment of advanced colorectal cancer. This report summarizes the results of treatment in 208 patients who were randomized to 5-FU alone or 5-FU with leucovorin in either a high-dose (200 mg/m2) or a low-dose regimen (20 mg/m2) intravenously for 5 days. Both of the 5-FU with leucovorin regimens were associated with improved survival compared with single-agent 5-FU (P less than 0.03). The interval to tumor progression, measurable tumor response rates, and measures of quality of life (performance status, weight gain, and symptomatic relief) were also improved significantly with the addition of leucovorin. There was no therapeutic advantage associated with the use of high-dose compared with low-dose leucovorin. The dose-limiting toxicity of 5-FU/leucovorin was stomatitis. There was one treatment-related fatality (due to sepsis) among the 138 patient receiving 5-FU/leucovorin (0.7%). The most favorable regimen in this trial was 5-FU with low-dose leucovorin, based upon considerations of therapeutic effectiveness, toxicity, and cost. A national intergroup trial is being coordinated by the National Cancer Institute that will test the efficacy of low-dose leucovorin with 5-FU as one approach to adjuvant therapy after a curative surgical resection in selected patients with Dukes' Stage B2 or C colon cancer.
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PMID:A phase III trial of 5-fluorouracil and leucovorin in the treatment of advanced colorectal cancer. A Mayo Clinic/North Central Cancer Treatment Group study. 246 76

In recent years molecular biology has been applied to the study of colonic carcinoma, both in the human and in the experimental animal. The data obtained have enriched our understanding of colonic carcinogenesis and are of potential interest for cancer diagnosis and prevention. In this paper we review part of the available literature on the molecular characterisation of colon tumors, with emphasis on the issues of clonality, in vitro cell lines, tumor progression and heredity of colon cancer.
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PMID:Molecular biology of colon cancer (review). 253 73

Leukocyte adherence inhibition-cell mediated immunity (LAI-CMI) studies were performed on leukocytes obtained from patients with various stages of breast cancer, colon carcinoma and lung cancer in order to monitor cell mediated immunity during tumor progression. In the presence of autologous serum, all patients with localized tumors showed positive LAI-CMI indexes (greater than 20%), while significant reduction of homologous tumor antigen recognition as measured by the LAI-CMI responses was observed in nearly all patients with Stage IV breast cancer, Duke C colon cancer and Stage III lung cancer. On substituting autologous serum with normal AB serum, leukocytes from patients with large tumor burdens responded to homologous tumor antigens. These results indicate the existence of organ-specific serum factor(s) which may mask the receptor sites on effector cells for tumor recognition. Patients with such serum blocking factor(s) showed significant increase of IgG immune complexes IgM, IgA and alpha-2-macroglobulins. Application of a protein A affinity column purification resulted in a major reduction of IgG and other immune globulins but not of alpha-2-macroglobulin. The blocking effects of autologous serum, however, were not completely abrogated by filtration on the protein A column, thus suggesting that SBF may be heterogeneous in nature and may occur in other serum protein fractions beside the immune globulins.
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PMID:Effector lymphocyte response to homologous tumor antigens in various stages of malignant disease as monitored by leukocyte adherence inhibition--cell mediated immunity (LAI-CMI). 328 Apr 78

We studied a series of 40 rats at various stages of colorectal carcinoma, as induced by N-methyl-N-nitro-Nitrosoguanidine. Lymphokine containing supernatants were obtained simultaneously from splenic and peripheral lymphocytes, after exposure to rat colon cancer antigen in vitro. The lymphokine was found capable of performing Macrophage Migration Inhibition (MIF) when obtained from rats with: carcinoma through serosa, carcinoma of submucosa, carcinoma of the mucosa and carcinoma in situ. All control rats were free of cancer and were MIF negative. The MIF response in this study was evaluated as a marker of chemically induced colorectal carcinoma in rats in order to better understand the lymphocyte response to tumor progression from atypia to adenocarcinoma of the colon.
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PMID:Colon cancer bearing rats produce a lymphokine which induces macrophage migration inhibition (MIF) in vitro. 328 27

To determine the frequency and clinical significance of oncogene abnormalities in colon cancer, deoxyribonucleic acids from 45 colon carcinomas and 15 benign adenomas were hybridized with 14 different protooncogene probes. Abnormalities of oncogenes were found in 22% of cancers at the time of resection. Amplification of c-myc or c-erbB-2 and allelic deletion of c-ras-Ha or c-myb were the most frequent abnormalities. The presence of altered oncogenes did not correlate with Dukes' stage, tumor progression, or patient survival after resection. One adenoma had an allelic deletion of the c-myb oncogene which was not seen in either the normal colon or an adjacent carcinoma. These data indicate that the spectrum of altered protooncogenes in colon carcinoma is similar to that of other adenocarcinomas, and that unstable oncogenes can be found before overt malignancy develops.
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PMID:Protooncogene abnormalities in colon cancers and adenomatous polyps. 355 13


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