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Query: UMLS:C0027627 (metastases)
 103,950 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A mathematical model of the process of metastases is formulated in which the hematogenous metastatic process from a solid tumor is considered to consist of a series of stages. A mathematical expression is obtained for the probability that no metastases will have been established by a characteristic time interval after tumor initiation. The murine T241 fibrosarcoma that rapidly and reproduceably produces pulmonary metastases was studied. Estimates of parameters required for the expression of probability of metastases formation were derived experimentally. The probability remains close to one for a characteristic time at which point it drops to zero. This indicates that at least in this experimental system there is a predictable critical time period beyond which micrometastases are virtually certain to have been formed.
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PMID:Micrometastases formation: a probabilistic model. 90 56

Aristolochic acid I (AAI), a nitrophenanthrene derivative, is the major component of the carcinogenic plant extract aristolochic acid, which has been used as a medicine since antiquity. Long term oral administration of AAI to male Wistar rats induces multiple tumors, mainly in the forestomach, ear duct, and small intestine. The presence of activated transforming genes was investigated in various tumors of 18 AAI treated rats, namely in 14 squamous cell carcinomas of the forestomach, 7 squamous cell carcinomas of the ear duct, 8 tumors of the small intestine, 3 tumors of the pancreas, 1 adenocarcinoma of the kidney, 1 lymphoma, and 2 metastases in the lung and the pancreas. By utilizing the tumorigenicity assay and Southern blot analysis, we have detected an activated c-Ha-ras gene in the DNAs of 5 of 5 squamous cell carcinomas of the forestomach. Direct sequencing of amplified material revealed an AT----TA transversion mutation at the second position of codon 61 of the c-Ha-ras gene (CAA to CTA) in all transfectants as well as in the 5 original rat tumors. Enzymatic amplification of ras sequences followed by selective oligonucleotide hybridization detected identical mutations in 93% (13 of 14) of forestomach tumors, in 100% (7 of 7) of ear duct tumors, and in the lung metastasis. Among those tumors tested, we had 4 cases in which the forestomach tumors and the ear duct tumors originated from the same rat, showing the same mutation in both tissues. Moreover, similar mutations were demonstrated at c-Ki-ras codon 61 in 1 of 7 ear duct tumors (CAA to CAT) and in 1 of 8 tumors of the small intestine (CAA to CTA) as well as at c-N-ras 61 (CAA to CTA) in a pancreatic metastasis. Additional transfection experiments of some tumors scoring negative for ras gene mutations in dot blot analyses revealed a CAA to CTA transversion at codon 61 of the c-Ha-ras gene in 1 forestomach tumor as well as at codon 61 of the c-N-ras in 1 hyperplasia of the pancreas and in 1 lymphoma. The apparent selectivity for mutations at adenine residues in AAI induced tumors is consistent with the identification of an N6-deoxyadenosine-AAI adduct formed by reaction of AAI with DNA in vitro, suggesting that carcinogen-deoxyadenosine adducts are the critical lesions in the tumor initiation by aristolochic acid.
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PMID:Aristolochic acid activates ras genes in rat tumors at deoxyadenosine residues. 220 37

Spontaneous metastasis from tumor transplants of two representative mouse B16 melanoma clones, G3.5 and G3.12, was examined experimentally to determine whether initial dissemination to the lungs, or secondary systemic spread from established lung metastases, resulted from organ-specific tropism or from nonspecific trapping of circulating tumor cells in capillary beds. In parabiosed mice, subcutaneous tumors metastasized extensively within hosts, but guests remained metastasis-free except following the rare involvement of the parabiotic junction during secondary spread. Intrasplenic tumor transplants metastasized to the liver, whereas intrarenal transplants metastasized to the lungs, reflecting patterns of venous drainage. Subcutaneous implants of neonatal lung and kidney in the flank opposite from the site of tumor initiation acquired metastases only during secondary systemic spread, and there was no evidence of organ selectivity. Metastases from various organs, and derived cell lines, when transplanted subcutaneously grew into tumors that initially metastasized exclusively to the lungs. These results indicate that both initial and secondary metastases of these B16 melanoma transplants occurred by nonspecific trapping of tumor cells in the first capillary bed encountered. In contrast, organ colonization following intravenous injection of tumor cells frequently proceeded beyond the first capillary bed.
Invasion Metastasis 1988
PMID:Metastatic dissemination of B16 melanoma: evidence that metastases can result from nonspecific trapping of disseminated tumor cells. 334 90

Sporadic and familial malignant melanoma susceptibility has been linked to defects in the chromosomal region 9p21. Recently, a putative 9p21 tumor suppressor gene, the cyclin dependent kinase inhibitor 2 (CDKN2) or p16 gene, has been shown to be deleted, mutated, or rearranged in a high percentage of sporadic melanoma cell lines, as well as mutated in the germline of a proportion of familial melanoma patients. CDKN2 encodes a M(r) 16,000 protein (p16) that plays a key role in cell cycle control by binding to the cyclin-dependent kinase 4 enzyme and inhibiting its ability to phosphorylate critical substrates necessary for transition past the G1 phase of the cell cycle. Thus, mutations or deletions of the CDKN2 gene could result in abnormal proliferation via defective cell cycle control. The correlation of 9p21 cytogenetic and molecular alterations with the clinical stages of melanoma progression suggests that dysfunction of a gene within this chromosomal region is critical to the evolution of melanoma. However, it remains unclear whether this gene is the CDKN2 gene. If so, then loss of p16 is potentially an initiating or early event in melanoma progression. To address the issues of what is the potential involvement of the CDKN2 gene in sporadic melanoma and precisely when during the clinically evident stages of melanoma progression defects in CDKN2 occur, we have evaluated by immunohistochemistry the expression of p16 protein in 103 melanocytic lesions representing all stages in the progression of melanoma. Our results suggest that loss of p16 protein expression is (a) not necessary for tumor initiation in malignant melanoma because all melanomas in situ and the majority of primary invasive melanomas retain expression of this protein; and (b) potentially more related to invasiveness or the ability to metastasize, because 52% of primary invasive tumors and 72% of metastatic lesions show partial or complete loss of expression of p16.
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PMID:Loss of expression of the p16/cyclin-dependent kinase inhibitor 2 tumor suppressor gene in melanocytic lesions correlates with invasive stage of tumor progression. 779 91

Gene amplification or structural alteration of different erbB genes exerts a transforming effect in a variety of human neoplasms. Overexpression of the EGF receptor is associated with tumor initiation and progression of renal cell carcinoma (RCC). However, the role of erbB-2 in these processes remains unknown. We investigated 34 renal cell carcinomas for gene amplification and expression of the EGFR and erbB-2 genes at the mRNA and protein level and their relationship to pathological and clinical parameters. No amplification of both genes has been observed. However, high expression of the EGF receptor protein and p185erbB2 was frequent in RCC and statistically significantly related to higher tumor grades. We could demonstrate a close correlation of p185erbB2 overexpression with high EGF receptor levels. Co-overexpression of both receptor types was significantly associated with metastatic disease. Our results suggest a synergistic involvement of both EGF receptor and p185erbB2 in the progression of RCC.
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PMID:Concomitant overexpression of the EGFR and erbB-2 genes in renal cell carcinoma (RCC) is correlated with dedifferentiation and metastasis. 860 53

Whereas apoptosis is a critical mode of cell deletion in normal organism development, apoptotic cells are also observed in tumors, especially following cytotoxic treatments, leading to questions about their role in tumor response to therapy. We have conducted a series of studies using murine tumor models and found that the ability of the tumor cells to undergo apoptosis correlates with tumor response to radiation. The best correlation was with the pretreatment apoptotic index, suggesting that apoptosis in some tumors may govern radiocurability by regulating the number of tumor clonogens. However, other roles for apoptosis in tumor response to radiation have not been ruled out. One of the important observations that has come from this work has been the heterogeneity in apoptosis propensity both within the cell population of a given tumor and among different types of tumors. Such findings underscore the fact that apoptosis is under complex genetic control and that some of the same oncogenes and tumor suppressor genes that are responsible for tumor initiation and progression to malignancy also dictate the apoptotic response to treatment. Understanding the biochemical and molecular pathways that govern this process may ultimately allow the development of strategies for modulating apoptosis for therapeutic benefit.
Cancer Metastasis Rev 1996 Mar
PMID:Programmed cell death and radioresistance. 884 83

Metastasis is a complex process involving a series of tumor-host interactions that follow tumor initiation and progression. Metastatic cancer cells must be capable of completing all stages of this process to establish secondary foci at distant sites. Most studies infer the functional significance of various observations based on models designed to emphasize the contributions of single molecules or ligand-receptor pairs. While providing useful insights into potential mechanisms of tumorigenesis and metastasis, additional studies are needed to elucidate the complex dynamic interactions involved in these processes. Nonetheless, a better understanding of how tumor cells metastasize is leading to new therapies to prevent and treat micrometastatic disease.
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PMID:The biology of colorectal cancer metastasis. 896 Aug 94

Twenty-nine nonendocrine pancreatic carcinomas (20 primary tumors and nine metastases) were studied by chromosome banding after short-term culture. Acquired clonal aberrations were found in 25 tumors and a detailed analysis of these revealed extensive cytogenetic intratumor heterogeneity. Apart from six carcinomas with one clone only, 19 tumors displayed from two to 58 clones, bringing the total number of clones to 230. Karyotypically related clones, signifying evolutionary variation, were found in 16 tumors, whereas unrelated clones were present in nine, the latter finding probably reflecting a distinct pathogenetic mechanism. The cytogenetic profile of pancreatic carcinoma was characterized by multiple numerical and structural changes. In total, more than 500 abnormal chromosomes, including rings, markers, homogeneously stained regions, and double minutes, altogether displaying 608 breakpoints, were detected. This complexity and heterogeneity notwithstanding, a nonrandom karyotypic pattern can be discerned in pancreatic cancer. Chromosomes 1, 3, 6, 7, 8, 11, 12, 17, and 19 and bands 1q12, 1q21, 3q11, 6p21, 6q21, 7q11, 7q22, 7q32, 11q13, 13cen, 14cen, 17q11, 17q21, and 19q13 were most frequently involved in structural rearrangements. A total of 19 recurrent unbalanced structural changes were identified, 11 of which were not reported previously: del(1)(q11), del(3)(p11), i(3)(q10), del(4)(q25), del(11)(p13), dup(11)(q13q23), i(12)(p10), der(13;15)(q10;q10), del(18)(q12), del(18)(q21), and i(19)(q10). The main karyotypic imbalances were entire-copy losses of chromosomes 18, Y, and 21, gains of chromosomes 7, 2, and 20, partial or whole-arm losses of 1p, 3p, 6q, 8p, 9p, 15q, 17p, 18q, 19p, and 20p, and partial or whole-arm gains of 1q, 3q, 5p, 6p, 7q, 8q, 11q, 12p, 17q, 19q, and 20q. In general, the karyotypic pattern of pancreatic carcinoma fits the multistep carcinogenesis concept. The observed cytogenetic heterogeneity appears to reflect a multitude of interchangeable but oncogenetically equivalent events, and the nonrandomness of the chromosomal alterations underscores the preferential pathways involved in tumor initiation and progression.
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PMID:Cytogenetic analysis of pancreatic carcinomas: intratumor heterogeneity and nonrandom pattern of chromosome aberrations. 973 11

The interaction of the adenomatous polyposis coli (APC) tumor-suppressor protein and the intracellular cell-adhesion protein beta-catenin is crucial for the development of colorectal tumors. Since functional nuclear complexes of beta-catenin with transcription factors have been identified recently, the knowledge of level and distribution of beta-catenin in sporadic colorectal tumors will give important insights into the intracellular mechanism of sporadic colorectal tumor initiation and progression. In contrast to the familiar adenomatous polyposis syndrome and to the majority of sporadic colorectal tumors, Peutz-Jeghers (PJ) syndrome is not caused by mutations in the APC gene. Since PJ syndrome is an inherited disease with an increased risk for gastrointestinal adenocarcinoma, whether beta-catenin plays a similarly important role for the development of PJ polyps should be further investigated. For these reasons we analyzed the distribution of beta-catenin in a total of 60 sporadic colorectal tumors at different stages of progression and in 6 PJ polyps. In addition to the localization at the cell-to-cell border membranes, fluorescence immunohistochemistry revealed a nuclear accumulation of beta-catenin in single tumor cells of 10/14 small adenomas with mild dysplasia and in 14/16 adenomas with moderate dysplasia. Further tumor progression is accompanied by an expansion of cells with increased level of nuclear and cytoplasmic beta-catenin. These cells were observed in 5/16 adenomas with moderate dysplasia and in 15/15 adenomas with severe dysplasia. In all adenocarcinomas investigated, as well as in the corresponding lymph node metastases, a sub-population of tumor cells exhibited a remarkably increased level of beta-catenin within the entire cytoplasm and the nucleus. In contrast to the situation in sporadic colorectal tumors, nuclear and cytoplasmic beta-catenin was not increased in PJ polyps. These results point to an extensive redistribution of beta-catenin, which starts early in colorectal tumorigenesis. The nuclear accumulation in single cells of small adenomas can be considered as the first visible sign of the loss of APC function. Thus the immunohistochemical detection of beta-catenin distribution could serve as a criterion for estimating the malignant potential in the clinico-pathological evaluation of colon tumors during their early progression.
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PMID:Intracellular distribution of beta-catenin in colorectal adenomas, carcinomas and Peutz-Jeghers polyps. 1035 35

To determine the role of retinoblastoma (Rb) gene alteration in hepatocarcinogenesis, we examined Rb protein expression immuno-histochemically in a series of surgically resected specimens including non-cancerous liver tissues with cirrhosis or chronic hepatitis, large regenerative nodules, pre-cancerous adenomatous hyperplasias as well as primary and metastatic lesions of hepatocellular carcinoma (HCC). All of the non-cancerous liver tissues, large regenerative nodules and adenomatous hyperplasias showed normal Rb protein expression. Altered Rb protein expression was observed in 31 (lack of Rb protein in 16 and over-expression in 15) of the 81 primary HCCs (38%) and was significantly associated with tumor differentiation grade: altered Rb protein expression occurred in 1 of 23 (4%), 16 of 43 (37%) and 14 of 15 (93%) well-, moderately and poorly differentiated tumors (moderately vs. well-differentiated p < 0.01; poorly vs. moderately differentiated p < 0.001). Incidences of both Rb protein absence and over-expression were higher for moderately differentiated than for well-differentiated tumors and even higher for poorly differentiated tumors. Rb protein absence and over-expression were observed in 9 (39%) and 10 (44%) of the 23 metastatic lesions of HCC, respectively, and the incidence of altered Rb protein expression (absence or over-expression) was significantly higher than in primary lesions (83% vs. 38%, p < 0.001). Our observations suggest that elevated and absent Rb protein are closely associated with tumor progression and developing metastatic disease rather than tumor initiation in cases of HCC. Int. J. Cancer (Pred. Oncol.) 84:604-608, 1999.
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PMID:Over-expression and lack of retinoblastoma protein are associated with tumor progression and metastasis in hepatocellular carcinoma. 1056 6


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