Detection of lymph node micrometastases in colorectal cancer.
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Colorectal Neoplasms↗
Biomedical subjects
D Ogreid
Publications and source records attributed to D Ogreid.
[New drugs in the treatment of advanced colorectal cancer].
BACKGROUND: Colorectal cancer is one of the leading cancers in industrialised countries in terms of incidence and mortality. Advanced colorectal cancer has traditionally been treated with 5-fluorouracil, alone or in combination with leucovorin. This treatment has shown response rates of 10-25%; however, little effect has been observed on survival. MATERIAL, METHODS AND RESULTS: In recent years, a number of new drugs for advanced colorectal cancer have been developed and tested. We have made a comprehensive survey of the literature and find that phase II and phase III clinical studies show improved response rates compared to the traditional use of 5-fluorouracil and leucovorin. Thymidylate-synthase inhibitors, oxaliplatine and topoisomerase inhibitors, used singly or in combination, improve response rates and show a significant effect on survival in patients with metastatic colorectal disease. INTERPRETATION: Several new drugs now available in hospital treatment of metastatic colorectal cancer show improved response and increased survival compared to traditional 5-fluorouracil regimens.
Antimetabolites, Antineoplastic↗
[Fluorinated pyrimidines in oral treatment of advanced colorectal cancer].
BACKGROUND: For several years, fluorinated pyrimidines have been used in the treatment of advanced colorectal cancer, mainly in the form of intravenous injections of 5-fluorouracil (5-FU), alone or in combination with leucovorin. Oral treatment with 5-FU has been difficult because of high toxicity and low bioavailability. MATERIAL, METHODS AND RESULTS: Increased knowledge of the metabolism of 5-FU, reviewed in this article, has led to the development of a number of new oral drugs for the treatment of advanced colorectal cancer. Administration of prodrugs and inhibitors of 5-FU-catabolic enzymes has led to stable and high levels of active drug. Several drugs have shown promising results in new clinical trials. INTERPRETATION: New 5-FU related drugs for oral administration show results comparable to those of the cytotoxic drugs that have been administered in hospital. In the future, general practitioners could possibly treat and follow up a larger proportion of these patients.
Administration, Oral↗
[Outplacement of medical students in local hospitals].
The organisation and content of the training of medical students in practical and clinical skills at Norwegian universities is presented and discussed. Based on experience from Tromsø University, an increased use of local hospitals for training medical students in practical and clinical skills is planned for all universities in Norway.
Curriculum↗
Frequent mutations of the p53 gene in cutaneous melanoma of the nodular type.
The frequency and significance of p53 alterations in cutaneous melanoma have not been completely clarified. In the present study, 31 primary melanomas of the nodular type and 15 metastases occurring between 1981 and 1983 were studied with respect to mutations in exons 7 and 8, as well as to p53 protein immunostaining using different antibodies. Altogether 13% of the primary tumors showed strong p53 staining using the DO-7 antibody. Different results were obtained with other antibodies. Seven mutations were found in primary and metastatic tumors; all of these were single base changes, most of which occurred in the core domain of the p53 protein responsible for sequence-specific DNA binding (residues 102-293). The mutations were not significantly associated with p53 staining results, and p53 alterations (mutations or marked immunopositivity) had no prognostic value. Our results indicate that point mutations in exons 7 and 8 are more frequent than previously reported in primary melanomas, and such changes may be important for the development of certain melanoma subgroups.
Adult↗
[Medical education in Norway. One common education, four different models].
There are four medical schools in Norway- in Oslo, Bergen, Trondheim and Tromsø. The curriculum at each faculty has undergone many changes during the last decade. The four curricula vary in both content and teaching methods. Two of the faculties base their curricula on problem-based learning and two have chosen other approaches. Terms with clerkships in local hospitals and in the primary health care system exist in each curriculum as periods which the students must spend on research work of their own choice. All faculties set the same standards in practical clinical skills with which the students must be familiar before graduation. We believe that having four different curricular is of benefit to the education of doctors. Only future evaluation and standard national examinations will determine whether there are any measurable differences in the practical and theoretical knowledge among graduates coming from these medical schools.
Curriculum↗
Genotypes of glutathione transferase M1 and P1 and their significance for lung DNA adduct levels and cancer risk.
The A-G polymorphism at codon 104 in the glutathione S-transferase P1 (GSTP1) gene was examined in 138 male lung cancer patients and 297 healthy controls. The patients had significantly higher frequency of the GG genotype (15.9%) and a lower frequency of AA (38.4%) than the controls (9.1% and 51.5%, respectively). The level of hydrophobic DNA-adducts were determined in lung tissue from 70 current smokers. Patients with the GG genotype had a significantly higher adduct level than patients with AA (15.5 +/- 10.2 vs 7.9 +/- 5.1 per 10(8) nucleotides, P = 0.006). We also analyzed the deletion polymorphism in the GSTM1 gene in 135 male patients and 342 controls. The patients were stratified according to histology, smoking dose, age, adduct level and mutational types found in the tumors (Ki-ras and p53 genes). The results consistently indicated that the GSTM1 null genotype was associated with a slightly increased lung cancer risk. When the combined GST M1 and P1 genotypes were examined, patients with the combination null and AG or GG had significantly higher adduct levels than all other genotype combinations (P = 0.011). The distribution of combined genotypes was also significantly different in cases and controls, mainly due to increased frequency of the combination GSTM1 null and GSTP1 AG or GG among patients.
Adult↗
Arginine 210 is not a critical residue for the allosteric interactions mediated by binding of cyclic AMP to site A of regulatory (RIalpha) subunit of cyclic AMP-dependent protein kinase.
The guanidinium groups of conserved arginines in the two intrachain cAMP-binding sites of regulatory (R) subunit of cAMP-dependent protein kinase have been implicated in the allosteric interactions by which cAMP binding leads to kinase activation. We have investigated the functional role of Arg-210, the conserved arginine in site A of murine type Ialpha R subunit, by analyzing the effects of nine different substitutions at this residue on cAMP binding and allosteric properties of bacterially expressed RIalpha subunits. All substitutions reduced the cAMP binding affinity of site A, but the magnitude of reduction varied from several hundredfold to 10(6)-fold. The differential effects of the different substitutions could not easily be rationalized by interactions with cAMP and might, in part, reflect interactions with other residues in the unoccupied cAMP-binding pocket. None of the Arg-210 substitutions appeared to disrupt the allosteric interaction by which occupation of site A slows dissociation of cAMP from site B, although the effect was difficult to elicit in full with mutations that had strong effects on cAMP binding. The two weakest substitutions, Arg-210 --> Ile and Arg-210 --> Thr, could be shown to have essentially no effect on the allosteric interaction by which occupation of site A reduces the affinity of R subunit for the catalytic subunit. The weaker mutations had a smaller effect on kinase activation by the suboptimal activator Rp-adenosine cyclic 3',5'-phosphorothioate than by cAMP, suggesting that the analog largely bypasses interactions with the guanidinium group of Arg-210.
Allosteric Regulation↗
Isoleucine 368 is involved in low-affinity binding of N6-modified cAMP analogues to site B of the regulatory subunit of cAMP-dependent protein kinase I.
The regulatory (R) subunit of cAMP-dependent protein kinase has a well-defined domain structure including the two in-tandem cAMP-binding sites that constitute the C-terminus of the protein. The N-terminal binding site (A) has a considerably higher affinity for analogues of cAMP that are substituted with bulky and hydrophobic substituents at the 6-amino group of the adenine ring compared to the affinity observed at the second site (B). On the basis of the crystal structure of the catabolite gene activator protein from Escherichia coli, molecular modelling of the binding domains suggested that a tyrosine (Y244) in site A could be involved in a high-affinity hydrophobic interaction, whereas a corresponding isoleucine (I368) in domain B could lead to steric hindrance in the binding of bulky N6-substituted analogues. Site-directed mutagenesis was used to construct mutations in Y244 and I368. Binding displacement experiments showed that replacing the tyrosine in site A with isoleucine (Y244I) did not affect the interaction of either N6-substituted or otherwise modified analogues with this site. However, replacing I368 with tyrosine (I368Y) led to a 3-4-fold increase in affinity for those N6-modified analogues that had a hydrophobic group attached directly or close to the 6-amino molecule. We conclude that I368 is involved in the molecular interaction between binding domain B and the 6-amino group of the adenine moiety of cAMP and that this residue is partly responsible for the reduced affinity of N6-substituted cAMP analogues for this site.
Amino Acid Sequence↗
[Prostate-specific membrane antigen. A new sensitive molecular indicator in metastasizing prostatic cancer].
Prostate cancer is the most common malignant disease in men in western societies. Extracapsular spread of carcinoma is found in approximately half of the patients that are treated by radical prostatectomy. Recently, a new prostate-specific membrane glycoprotein was cloned and sequenced. A highly sensitive and specific nested reverse transcriptase polymerase chain reaction has been developed to detect early occult haematogeneous micrometastatic prostate cells. We analysed venous samples from 17 patients with metastatic prostate cancer using a modified reaction assay. This showed presence of micrometastatic prostate cells in 14 patients. Molecular detection of circulating prostatic epithelial cells could improve clinical staging and treatment of early prostate cancer.
Aged↗
Detection and identification of Ki-ras exon 1 mutations by minigel single-strand conformation polymorphism.
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Base Sequence↗
[Determination of the activated proto-oncogene (Ki-ras) in feces. A new laboratory analysis for early diagnosis of colorectal cancer].
Colorectal cancer is one of the most common malignancies in Norway. Many cases of the disease are detected at a stage where surgery is unlikely to result in cure. Currently used screening tests based on faecal occult blood and other tumour markers are poor indicators of colorectal neoplasia. Multiple gene alterations are associated with colorectal carcinogenesis. Mutations in the Ki-ras oncogene occur in 50% of colorectal carcinomas and also in 50% of the precursor lesions, the adenomas. These mutations have proved to be detectable in the faeces of patients with colorectal tumours, but the techniques used so far have been impractical for screening purposes. We have developed a rapid and simple laboratory technique, based on the polymerase chain reaction, for detecting mutated Ki-ras in the faeces. In eight of 12 patients with mutated Ki-ras in adenomas or carcinomas we found the corresponding mutations in stool samples. Our results represent a significant progression towards a simple and effective DNA-based screening strategy for early detection of curable colorectal cancer.
Aged↗
Ala335 is essential for high-affinity cAMP-binding of both sites A and B of cAMP-dependent protein kinase type I.
A single amino acid substitution (Ala335Asp) in cAMP binding site B of the regulatory subunit of cAMP-dependent protein kinase type I was sufficient to abolish high affinity cAMP binding for both cAMP binding sites A and B. Furthermore, the Ala335Asp mutation increased the activation constant for cAMP of the mutant holoenzyme 30-fold and also enhanced the rate of holoenzyme formation. Thus, the substitution was responsible for the dominant negative phenotype of the enzyme. Activation of mutant holoenzyme with site-selective cAMP analogs indicated that the enzyme dissociated through binding to site A only. Our results provide evidence that Ala335 is an essential residue for high affinity cAMP binding of both sites as well as for the functional integrity of the enzyme.
Alanine↗
Aldolase B A149P mutation and hereditary fructose intolerance are not associated with sudden infant death syndrome.
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Chromosome Aberrations↗
[Congenital fructose intolerance. New molecular aspects].
Hereditary fructose intolerance is a human autosomal recessive disease caused by a deficiency of aldolase B that results in an inability to metabolize fructose and related sugars. Molecular analyses have shown that most defects are caused by point mutations in critical regions of the aldolase B gene. We have performed PCR-based DNA analysis of members of two Norwegian families with hereditary fructose intolerance. The affected individuals from both families contained a point mutation (A149P) in exon 5 of the aldolase B gene. Molecular diagnosis of fructose intolerance is rapid and specific, and causes no inconvenience to the patient. It should be preferred to conventional fructose intolerance tests and visceral biopsy analyses.
Adult↗
[Analysis of Ki-ras in pancreatic fluid aspirate. A new diagnostic possibility in investigation of pancreatic cancer].
The prognosis for pancreatic carcinoma is generally poor. The chance of survival could be improved if curative surgery were performed, but early diagnosis is then essential. Fine-needle aspiration cytology and endoscopic retrograde cholepancreaticography (ERCP) are widely used in order to obtain a precise diagnosis before laparotomy. In almost all patients with pancreatic adenocarcinomas, the oncogene Ki-ras is activated by point mutation. We describe a patient where conventional diagnostic procedures were inconclusive. However, DNA-analysis of aspirate from the pancreatic duct and from a pancreatic cyst showed activated Ki-ras oncogene. A malignant diagnosis was later confirmed. We propose that DNA-analyses of pancreatic fluid or tissues should be used whenever facing problems with an early and accurate diagnosis of pancreatic lesions.
Adenocarcinoma↗
Arg-242 is necessary for allosteric coupling of cyclic AMP-binding sites A and B of RI subunit of cyclic AMP-dependent protein kinase.
The functional consequences of Arg-242 to Ser or Lys substitutions in type I alpha regulatory (R) subunits of cAMP-dependent protein kinase were analyzed by using recombinant murine R subunits expressed in Escherichia coli. These mutations arose in cAMP-resistant mutants to S49 mouse lymphoma cells and were shown previously to inhibit cAMP binding to site A, the more amino-terminal of two intrachain cAMP-binding sites. Binding of cAMP to site A of the mutant R subunits could be detected by cAMP-dependent quenching of endogenous tryptophan fluorescence, [3H]cAMP binding to mutant R subunits with the Arg-242 mutations without or with an inactivating mutation in site B, or biphasic dissociation of [3H]cAMP from the mutant subunits at low temperature. The mutations reduced site A affinities by about 25-fold, and the reductions were attributable to accelerated rates of cAMP dissociation. While the presence of cAMP in site A retards dissociation of [3H]cAMP from site B of wild-type R subunits, saturation of site A had little or no effect on dissociation of [3H]cAMP from site B of the mutant subunits. The predominant effect of the mutations, therefore, was loss of allosteric coupling between the two cAMP-binding sites. A second allosteric interaction, that coupling occupation of site A with a reduced affinity of R for catalytic subunit, was inhibited only partially by these mutations at Arg-242.
Allosteric Regulation↗
(Rp)- and (Sp)-8-piperidino-adenosine 3',5'-(cyclic)thiophosphates discriminate completely between site A and B of the regulatory subunits of cAMP-dependent protein kinase type I and II.
8-Piperidino-cAMP has been shown to bind with high affinity to site A of the regulatory subunit of cAMP-dependent protein kinase type I (AI) whereas it is partially excluded from the homologous site (AII) of isozyme II [Ogreid, D., Ekanger, R., Suva, R. H., Miller, J. P., and Døskeland, S. O. (1989), Eur. J. Biochem. 181, 19-31]. To further increase this selectivity, the (Rp)- and (Sp)-diastereoisomers of 8-piperidino-cAMP[S] were synthesized and analyzed for their potency to inhibit binding of [3H]cAMP to site A and site B from type I (rabbit skeletal muscle) and type II (bovine myocardium) cAMP-dependent protein kinases. (Sp)-8-Piperidino-cAMP[S] showed an enhanced relative affinity for site AI, thus being by far the best A-selective compound (more than 100-fold) tested for this isozyme. In contrast, the (Rp)-isomer was less selective for AI than 8-Piperidino-cAMP itself. The reduction in affinities for BII, compared to 8-piperidino-cAMP, were 10-fold and 50-fold for the (Sp)- and (Rp)-isomer, respectively. Both isomers were almost completely excluded from AII, with affinities about 1000-fold lower than 8-piperidino-cAMP itself. The (Rp)-isomer selected BII with an affinity about 10,000 times higher than for AII, whereas the (Sp)-isomer showed a preference of about 70,000-fold in favour of BII. 8-Piperidino-cAMP as well as its (Sp)-isomer activated both types of holoenzyme protein kinases whereas the (Rp)-isomer acted as an antagonist of cAMP-induced activation. The study concludes that the combination of piperidino- and exocyclic sulfur substitutions generate cAMP analogs that completely discriminate between site A and B of cAMP-dependent protein kinases.
Binding Sites↗