Biomedical subjects

G Griffioen

Publications and source records attributed to G Griffioen.

At least 55 records · Page 3Linked to original sources

PubMed1998

Is Barrett's esophagus characterized by more pronounced acid reflux than severe esophagitis?

OBJECTIVE: Barrett's esophagus is related to gastroesophageal reflux disease (GERD). However, only a small fraction of patients with GERD develop Barrett's esophagus. We evaluated whether gastroesophageal acid reflux is more pronounced in Barrett's patients than in patients with moderate or severe endoscopic esophagitis. METHODS: Retrospective evaluation of results of esophageal manometry and 24 hour ambulatory pH monitoring performed between 1990 and 1996 at the Leiden University Medical Center in those patients who also underwent endoscopy < or = 3 months before pH-metry. Included were 51 patients with Barrett's esophagus, 30 patients with severe esophagitis, 45 patients with moderate esophagitis, and 24 healthy control subjects. RESULTS: Patients with Barrett's esophagus had significantly increased acid reflux time (p < 0.01-0.05) compared to patients with moderate, but not compared to patients with severe esophagitis. Distal esophageal body motility and LES pressure were significantly (p < 0.01-0.05) reduced in patients with Barrett's esophagus compared to patients with moderate esophagitis but not compared to those with severe esophagitis. CONCLUSION: Although acid reflux is increased in patients with Barrett's esophagus and esophageal motility is impaired, other factors apart from acid exposure and motility contribute to the development of Barrett's esophagus.

Analysis of Variance↗

PubMed1998

Diagnosis of Crohn's ileitis and monitoring of disease activity: value of Doppler ultrasound of superior mesenteric artery flow.

OBJECTIVE: To assess the value of measurements of superior mesenteric artery flow using Doppler ultrasound for detecting disease activity in patients with proven or suspected Crohn's disease. METHODS: Superior mesenteric artery flow was measured prospectively in 31 patients with known or suspected small-bowel disease. Sixteen patients were known to suffer from Crohn's disease and were suspected of having active disease. Fifteen patients had abdominal complaints without a specific diagnosis. Enteroclysis was used as the standard of reference to detect Crohn's disease, to define the location of small-bowel Crohn's disease, and to assess disease activity by demonstrating cobblestoning. Disease activity was further substantiated by clinical signs, laboratory values, and clinical follow-up. RESULTS: Ten patients with active disease on enteroclysis made up group 1. Group 2 comprised nine patients known to have Crohn's disease but without active disease (inactive small-bowel disease). The remaining 12 patients made up group 3. In group 1, the flow volume values were significantly higher than those in group 2 and group 3: 738 +/- 411 (mean +/- SD) versus 364 +/- 101 and 300 +/- 91, respectively (p < 0.05). CONCLUSIONS: Whereas the initial diagnosis of small-bowel involvement in Crohn's disease may rely on enteroclysis, Doppler measurements of superior mesenteric artery flow are useful to monitor the activity of Crohn's disease.

Adult↗

PubMed1997

Molecular analysis of the APC gene in 105 Dutch kindreds with familial adenomatous polyposis: 67 germline mutations identified by DGGE, PTT, and southern analysis.

Germline mutations of the adenomatous polyposis coli (APC) gene are responsible for familial adenomatous polyposis (FAP), an autosomal dominant predisposition to colorectal cancer. We screened the entire coding region of the APC gene for mutations in an unselected series of 105 Dutch FAP kindreds. For the analysis of exons 1-14, we employed the GC-clamped denaturing gradient gel electrophoresis (DGGE), while the large exon 15 was examined using the protein truncation test. Using this approach, we identified 65 pathogenic mutations in the above 105 apparently unrelated FAP families. The mutations were predominantly either frameshifts (39/65) or single base substitutions (18/65), resulting in premature stop codons. Mutations that would predict abnormal RNA splicing were identified in seven cases. In one of the families, a nonconservative amino acid change was found to segregate with the disease. In spite of the large number of APC mutations reported to date, we identified 27 novel germline mutations in our patients, which reiterates the great heterogeneity of the mutation spectrum in FAP. In addition to the point mutations identified in our patients, structural rearrangements of APC were found in two pedigrees, by Southern blot analysis. The present study indicates that the combined use of DGGE, protein truncation test, and Southern blot analysis offers an efficient strategy for the presymptomatic diagnosis of FAP by direct mutation detection. We found that the combined use of the currently available molecular approaches still fails to identify the underlying genetic defect in a significant subset of the FAP families. The possible causes for this limitation are discussed.

Adenomatous Polyposis Coli↗

PubMed1997

Crohn's disease of the upper gastrointestinal tract.

Although Crohn's disease (CD) is generally found in the ileum and/or colon, since the 1960s it has become evident that this chronic inflammatory disorder of unknown aetiology can affect the whole gastrointestinal tract from mouth to anus. In 0.5-13% of patients with ileocolonic CD the disease occurs in the upper gastrointestinal tract as well (i.e., from mouth through jejunum). With the radiological double-contrast technique, however, early signs of upper gastrointestinal CD may be detected in 20-40% of patients with ileocolitis. On the other hand, histologically evaluated biopsies from the lower oesophagus, body of the stomach, gastric antrum and the duodenal bulb of patients with Crohn's disease from whom the upper gastrointestinal tract is normal, according to X-ray or endoscopy may reveal lesions, which are considered to be pathologically diagnostic. Jejunal involvement occurs in 4-10% of patients with ileitis, ileocolitis or colitis. In early studies biopsies of apparently normal buccal mucosa from patients with Crohn's disease showed a significant correlation between the activity of the disease, as defined by the Crohn's Disease Activity Index, and the number of plasma cells containing IgM, suggesting a generalized activated humoral defence system during relapse. A diagnosis of Crohn's disease of the upper gastrointestinal tract can be achieved by combining recognition of clinical, roentgenographic, and endoscopic features. Provided that other causes of granulomatous involvement of the gastrointestinal tract can be excluded, non-caseating granulomas are generally accepted as the histological proof of Crohn's disease. When Crohn's disease does involve the upper gastrointestinal tract, there is nearly always concomitant disease in the small bowel or colon. Compared to patients with an ileocolonic localization, patients with Crohn's disease in the upper gastrointestinal tract more frequently have colic-like abdominal pain and/or cramps, nausea and anorexia as presenting symptoms and are younger at onset of the disease. Medical therapeutic principles are the same as for Crohn's disease elsewhere in the gastrointestinal tract. Absolute indications for surgical treatment are massive bleeding, progressive stenosis, and extensive fistula formation.

Crohn Disease↗

PubMed1997

Inflammatory bowel disease activity assessment using technetium-99m-HMPAO leukocytes.

Aim of the study was to evaluate [99mTc]hexamethyl-propylamine-oxime (HMPAO) leukocyte scintigraphy for the assessment of disease activity and extent in inflammatory bowel disease patients. Results and scores of scintigraphy using [99mTc]HMPAO-labeled leukocytes were retrospectively compared with the activity index of van Hees, laboratory parameters, and gastroenterologists' assessment of disease using endoscopy, radiology, and histology plus clinical parameters in 136 patients with Crohn's disease (115) and ulcerative colitis (21) and in 29 controls. There were 114 positive and 22 negative [99mTc]HMPAO leukocyte scintigrams. Sensitivities for active disease at 1 and 3 hr were 98% and 98% and specificities were 100% and 83%, respectively. [99mTC]HMPAO leukocyte scintigraphy is superior to the activity index and the gastroenterologists' clinical assessment of active inflammation in IBD patients. Scintigraphy allows assessment of the existence, extent, and intensity of active inflammation in IBD patients in one examination with high accuracy.

Adolescent↗

PubMed1997

Contribution of plasminogen activators and their inhibitors to the survival prognosis of patients with Dukes' stage B and C colorectal cancer.

Despite the advances in pre-, peri- and post-operative medical care of colorectal carcinoma patients, the prognosis has improved only marginally over recent decades. Thus, additional prognostic indicators would be of great clinical value to select patients for adjuvant therapy. In previous studies we found that colorectal carcinomas have a marked increase of the urokinase-type of plasminogen activator (u-PA), and the inhibitors PAI-1 and PAI-2, whereas the tissue-type plasminogen activator (t-PA) is found to be decreased in comparison with adjacent normal mucosa. In the present study we evaluated the prognostic value of several plasminogen activation parameters, determined in both normal and carcinomatous tissue from colorectal resection specimens, for overall survival of 136 Dukes' stage B and C colorectal cancer patients, in relation to major clinicopathological parameters. Uni- and multivariate analyses indicated that a high PAI-2 antigen level in carcinoma, a low t-PA activity and antigen level and a high u-PA/t-PA antigen ratio in adjacent normal mucosa are significantly associated with a poor overall survival. A high ratio of u-PA antigen in the carcinomas and t-PA antigen in normal mucosa, i.e. u-PA(C)/t-PA(N), was found to be predictive of a poor overall survival as well. All these parameters were found to be prognostically independent of the clinicopathological parameters. Multivariate analysis of combinations of these prognostically significant plasminogen activation parameters revealed that they are important independent prognostic indicators and have in fact a better prognostic value than their separate components. Based on these combined parameters, subgroups of patients with Dukes' stage B and C colorectal cancer could be identified as having either a high or a low risk regarding overall survival. In conclusion, these findings emphasize the relevance of the intestinal plasminogen activation system for survival prognosis of patients with colorectal cancer and, in the future, might constitute a patient selection criterion for adjuvant therapy.

Aged↗

PubMed1997

Suppression of intestinal mucosal natural killer cells by corticosteroids.

BACKGROUND: Corticosteroid therapy of patients with inflammatory bowel disease can give rise to systemic side-effects. Budesonide is a topically acting corticosteroid with low systemic bioavailability and is efficacious in the treatment of inflammatory bowel disease. Natural killer cells were previously found to be altered, both systemically and locally, in patients with inflammatory bowel disease. Modulatory effects of budesonide, prednisolone, dexamethasone, and cortisol on peripheral blood NK cells have already been described, but have never been assessed on mucosal NK cells from the intestine. METHODS: The effect of the synthetic corticosteroids prednisolone and budesonide, the endogenous corticosteroid cortisol, and adrenocorticotropic hormone was analysed on NK cells isolated from the lamina propria of human intestinal resection specimens. RESULTS: The three corticosteroids suppressed intestinal NK cell activity, not only during the cytotoxicity assay, but also after pre-incubation of the lamina propria mononuclear cells. ACTH, however, did not affect the activity of intestinal NK cells. We previously showed that corticosteroid-suppressed peripheral blood NK cell activity could be restored in vivo, but not in vitro, by the administration of ACTH. In the present study, the in vitro incubation of budesonide- or prednisolone-suppressed mucosal NK cells with cortisol, alone or combined with ACTH, did not revert the suppressed NK cell activity. These findings are similar to our previous observations with peripheral blood NK cells. CONCLUSIONS: Intestinal mucosal NK cells can be suppressed by systemically as well as locally acting corticosteroids. This suppression in NK cell activity is not reversed by incubation with cortisol and/or ACTH.

Adrenocorticotropic Hormone↗

PubMed1997

Signalling pathways leading to transcriptional regulation of genes involved in the activation of glycolysis in yeast.

Addition of glucose to yeast cells growing on less preferred carbon sources triggers profound changes in the expression levels of several genes. This paper focuses on the signal transduction pathways leading to transcriptional activation of the glycolysis in Saccharomyces cerevisiae during the transition from respiratory to fermentative growth conditions. To this end, we studied the transcriptional regulation of glycolytic genes (PFK1, PYK1 and PDC), one gluconeogenic gene (FBP1) and the two genes encoding the 6-phosphofructo-2-kinase isoenzymes (PFK26 and PFK27) during this transition. The results of experiments using glycolysis mutants, different fermentable carbon sources and 2-deoxyglucose indicate that proper transcriptional regulation of these genes is dependent on the ability to form glucose 6-phosphate by any one of the three hexose kinases. In addition, we conclude that signalling via the Ras-adenylate cyclase pathway is not necessary for the proper transcriptional response of glycolytic and gluconeogenic genes to glucose, because the transcription of these genes is not significantly affected in mutants having either high or low activities of this pathway. In contrast, the transcriptional regulation of the PFK26 and PFK27 genes is significantly altered in several of the Ras-adenylate cyclase pathway mutants studied, indicating that protein kinase A plays an important role in the transcriptional regulation of these genes.

Adenylyl Cyclases↗

PubMed1997

Decision analysis in the management of duodenal adenomatosis in familial adenomatous polyposis.

BACKGROUND: Patients with familial adenomatous polyposis are not only at high risk of developing adenomas in the colorectum but a substantial number of patients also develop polyps in the duodenum. Because treatment of duodenal polyps is extremely difficult and it is unknown how many patients ultimately develop duodenal cancer, the value of surveillance of the upper digestive tract is uncertain. AIMS: (1) To assess the cumulative risk of duodenal cancer in a large series of polyposis patients. (2) To develop a decision model to establish whether surveillance would lead to increased life expectancy. METHODS: Risk analysis was performed in 155 Dutch polyposis families including 601 polyposis patients, and 142 Danish families including 376 patients. Observation time was from birth until date of last contact, death, diagnosis of duodenal cancer, or closing date of the study. RESULTS: Seven Dutch and five Danish patients developed duodenal cancer. The lifetime risk of developing this cancer by the age of 70 was 4% (95% confidence interval 1-7%) in the Dutch series and 3% (95% confidence interval 0-6%) in the Danish series. Decision analysis showed that surveillance led to an increase in life expectancy by seven months. CONCLUSIONS: Surveillance of the upper digestive tract led to a moderate gain in life expectancy. Future studies should evaluate whether this increase in life expectancy outweighs the morbidity of endoscopic examination and proximal pancreaticoduodenectomy.

Adenomatous Polyposis Coli↗

PubMed1997

Doppler sonography evaluation of superior mesenteric artery flow to assess Crohn's disease activity: correlation with clinical evaluation, Crohn's disease activity index, and alpha 1-antitrypsin clearance in feces.

OBJECTIVE: This study was undertaken to investigate the value of Doppler flow measurements of the superior mesenteric artery (SMA) as a marker for disease activity in patients with Crohn's disease. SUBJECTS AND METHODS: Duplex Doppler sonography measurements of SMA blood flow volume were obtained in 29 consecutive patients with suspected Crohn's disease. We prospectively sought a correlation between the independent assessment of Doppler flow measurements and markers for disease activity: Crohn's disease activity index and fecal alpha 1-antitrypsin clearance and our reference standard based on clinical history, physical examination, laboratory values, endoscopy, surgery, and follow-up. RESULTS: In 27 of 29 patients, adequate measurements of SMA blood flow were obtained. In 15 patients no disease activity was judged to be present or no Crohn's disease (n = 2) was found at follow-up (group 1). In 12 patients, activity of Crohn's disease was diagnosed (group 2) on the basis of the reference standard. In group 2 the Doppler SMA blood flow values were significantly higher (p < .05) than those for group 1 (826 +/- 407 ml/min versus 323 +/- 103 ml/min). Of the other parameters investigated, only the alpha 1-antitrypsin value correlated with the reference standard but to a lesser degree than the values for SMA blood flow measurement. CONCLUSION: This prospective study shows that SMA Doppler blood flow measurements can be used to assess disease activity in patients with Crohn's disease. This approach may be of value in the diagnosis and follow-up of patients with Crohn's disease, providing directly available, quantifiable, noninvasive information on disease activity.

Adult↗

PubMed1996

Prognostic value of the plasminogen activation system in patients with gastric carcinoma.

BACKGROUND: Patients with gastric cancer have a poor prognosis and can be cured by surgery only if the cancer is detected in an early stage. Extended surgery, down staging with chemotherapy before operation, and new postoperative treatments are recent approaches to increase survival rates. Categorizing patients' prognoses as good or poor by pathophysiologic markers, however, may be of great help in selecting therapies for these patients. For example, plasminogen activation (PA) parameters, that play an important role in tumor invasion and metastasis, have prognostic value for several human malignancies. METHODS: We evaluated the relation between several PA parameters in tissue with standard clinicopathologic parameters and with the overall survival of 50 consecutive patients with gastric carcinoma. RESULTS: Univariate analysis showed that a low tissue-type plasminogen activator (t-PA) activity in normal mucosa and in carcinomas and a high antigen level of inhibitor type-1 (PAI-1), and, to a lesser extent, of urokinase-type plasminogen activator (u-PA) receptor, in carcinomas are associated with a poor overall survival of the patients. In contrast, of the 14 clinicopathological parameters only the number of eosinophils in the tumors was associated with survival. Multivariate analysis revealed that the t-PA and PAI-1 levels are independently associated with survival. CONCLUSIONS: Plasminogen activation parameters in both normal and carcinomatous tissue of the stomach of patients with gastric carcinoma are of particular clinical interest because of their prognostic impact on overall survival.

Aged↗

PubMed1996

The risk of brain tumours in hereditary non-polyposis colorectal cancer (HNPCC).

Hereditary non-polyposis colorectal cancer (HNPCC) is known to be associated with several extracolonic cancers, e.g., cancers of the endometrium, stomach, urinary tract, small bowel and ovary. An association between HNPCC and brain tumours has also been reported, although previous risk analysis did not reveal an excess of this type of tumour. To determine whether HNPCC predisposes patients to brain tumours, we used risk analysis to compare families with HNPCC to those in the general population. Of the 1,321 subjects from 50 HNPCC families (with 60,237 person-years of follow-up) in the Dutch HNPCC Registry which satisfy the Amsterdam Criteria, 312 had colorectal cancer. The registry revealed 14 brain tumours in the HNPCC-patients and their first-degree relatives: 5 astrocytomas, 3 oligodendrogliomas, 1 ependymoma and 5 tumours for which a pathological report was not available. The relative risk of brain tumour in patients with HNPCC and their first-degree relatives was 6 times greater than in the general population (95% confidence interval, 3.5 to 10.1). After exclusion of the cases based only on family history, the relative risk was 4.3 (95% confidence interval, 2.3 to 8.0). Although the relative risk of brain tumour was increased, the lifetime risk was low (3.35%). Because it is not certain whether an improvement of the overall prognosis can be achieved by early diagnosis and intervention, and in view of the low lifetime risk, we do not recommend screening for brain tumours in HNPCC families.

Adolescent↗

PubMed1996

Budesonide in inflammatory bowel disease.

Due to its immunomodulatory and anti-inflammatory properties glucocorticosteroids have proved to be highly efficacious in patients with inflammatory bowel disease. However, because of the risk of side-effects, the dose and duration of therapy with systemically acting glucocorticosteroids have to be restricted. Recently the use of topically acting glucocorticosteroids has attracted great interest. Among the various topically acting glucocorticosteroids budesonide has emerged as the most promising. Budesonide is highly potent, is readily water-soluble and has low systemic bioavailability, thus reducing the risk of corticosteroid-related side-effects. When given as enema to patients with proctitis or proctosigmoiditis, the efficacy of budesonide is greater than that of placebo and equal to that of prednisolone or 5-aminosalicylic acid enemas. In an enteric-coated formulation budesonide is more effective than placebo in achieving and maintaining remission in patients with ileocecal Crohn's disease. Although corticosteroid-related side-effects are rare, some suppression of the hypothalamic-pituitary-adrenal axis may occur.

Administration, Oral↗

PubMed1996

Tissue levels of matrix metalloproteinases MMP-2 and MMP-9 are related to the overall survival of patients with gastric carcinoma.

Proteinases are involved in tumour invasion and metastasis. Several matrix metalloproteinases (MMPs) have been shown to be increased in various human carcinomas. We assessed the levels of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) in 50 gastric carcinomas and corresponding mucosa using quantitative gelatin zymography. Both MMP levels were significantly enhanced in gastric carcinomas compared with adjacent mucosal tissue, showed a relatively poor intercorrelation and no relation was found with histopathological carcinoma classifications according to Laurén, WHO and tumour-node-metastasis (TNM). Cox's multivariate proportional hazards analyses revealed that high carcinomatous MMP values are of prognostic significance for a poor overall survival of the patients, independent of the major clinicopathological parameters.

Aged↗

PubMed1996

Cancer risk in families with hereditary nonpolyposis colorectal cancer diagnosed by mutation analysis.

BACKGROUND & AIMS: Hereditary nonpolyposis colorectal cancer is characterized by early-onset colorectal cancer and the occurrence of various other cancers. The recent isolation of four mismatch repair genes responsible for hereditary nonpolyposis colorectal cancer allows for the identification of carriers within affected families. The purpose of this study was to assess the age-specific cancer risk in a large series of gene carriers. METHODS: Thirty-four families were studied by mutation analysis. In 19 of these families, pathogenic mutations were found at hMSH2 or hMLH1. Of 382 relatives, 124 had a mutation in hMLH1 and 86 in hMSH2. RESULTS: The lifetime risk of colorectal cancer was the same in both groups of gene carriers (80%). The risk of endometrial cancer was greater in hMSH2 gene carriers compared with hMLH1 gene carriers (61% vs. 42%), but the difference was not statistically significant. A very high relative risk of cancer of the small bowel (relative risk of >100) was observed in carriers of either gene. Only the carriers of hMSH2 mutations had a significantly increased relative risk of cancer of the urinary tract (kidney and ureter) (relative risk of 75.3), stomach (relative risk of 19.3), and ovaries (relative risk of 8.0). CONCLUSIONS: This study provides estimates of cancer risk that may contribute to the appropriate management of gene carriers within families with hereditary nonpolyposis colorectal cancer.

Adolescent↗

PubMed1996

Glucose-triggered signalling in Saccharomyces cerevisiae: different requirements for sugar phosphorylation between cells grown on glucose and those grown on non-fermentable carbon sources.

Addition of glucose or fructose to cells of the yeast Saccharomyces cerevisiae grown on a nonfermentable carbon source triggers within a few minutes posttranslational activation of trehalase, repression of the CTT1 (catalase) and SSA3 (Hsp70) genes, and induction of the ribosomal protein genes RPL1, RPL25 and RPS33. By using appropriate sugar kinase mutants, it was shown that rapid glucose- or fructose-induced activation of trehalase requires phosphorylation of the sugar. On the other hand, partial induction of RPL1, RPL25 and RPS33 as well as partial repression of CTT1 and SSA3 were observed in the absence of sugar phosphorylation. In glucose-grown nitrogen-starved yeast cells readdition of a nitrogen source triggers activation of trehalase in a glucose- or fructose-dependent way, but with no apparent requirements for phosphorylation of the sugar. Repression of CTT1 and SSA3 under the same conditions was also largely dependent on the presence of the sugar and also in these cases there was a strong effect when the sugar could not be phosphorylated. Nitrogen induction of RPL1, RPL25 and RPS33 was much less dependent on the presence of the sugar, and only phosphorylated sugar caused a further increase in expression. These results show that two glucose-dependent signalling pathways, which can be distinguished on the basis of their requirement for glucose phosphorylation, appear to be involved in activation of trehalase, repression of CTT1 and SSA3 and induction of ribosomal protein genes. They also show that nutrient-induced repression of CTT1 and SSA3 is not a response to improvement of the growth conditions because the addition of nonmetabolizable sugar does not ameliorate the growth conditions. Similarly, the upshift in ribosomal protein synthesis cannot be a response to increased availability of energy or biosynthetic capacity derived from glucose, but it is apparently triggered to a significant extent by specific detection of glucose as such.

Carbohydrate Metabolism↗

PubMed1996

Ribosomal protein gene transcription in Saccharomyces cerevisiae shows a biphasic response to nutritional changes.

Nutrients are major determinants of ribosomal protein (rp-) gene transcription in Saccharomyces cerevisiae. In order to investigate the molecular mechanisms underlying this nutritional control, yeast mutants that display defects in the glucose up-shift response of rp-gene transcription were isolated. Interestingly, although growth of these mutants on glucose-containing medium was severely affected an initial increase in rp-gene transcription by nutritional up-shift was still observed. However, at later time points, rp-mRNA levels decreased strongly. Various other types of severe growth limitation also did not prevent the initial up-shift in transcription. The results suggest that the glucose up-shift response of rp-gene transcription comprises two phases: an initial, transient response independent of the actual growth potential, and a sustained response which is dependent on growth and requires both glucose and adequate nitrogen sources. Previously, it was found that protein kinase A (Pka) mediates the initial up-shift response, without the need for regulation of Pka activity by cAMP. The present data substantiate that, besides the RAS/adenylate cyclase pathway, an alternative pathway through Pka regulates rp-gene transcription. In addition, evidence is presented that the sustained response does not require Pka activity. Based on these results, taken together, a model is proposed in which rp-gene transcription is dynamically regulated by multiple signal transduction pathways.

Blotting, Northern↗

PubMed1996

Majority of hMLH1 mutations responsible for hereditary nonpolyposis colorectal cancer cluster at the exonic region 15-16.

Hereditary nonpolyposis colorectal cancer (HNPCC) is a common autosomal dominant cancer susceptibility condition. Inherited mutations in at least four DNA mismatch repair genes, hMSH2, hMLH1, hPMS1, and hPMS2, are known to cause HNPCC. In this study we used denaturing gradient gel electrophoresis (DGGE) to screen for hMLH1 mutations in 34 unrelated HNPCC families (30 Dutch, 3 Italian, and 1 Danish). Ten novel pathogenic germ-line mutations (seven affecting splice sites, two frameshifts, and one in-frame deletion of a single amino acid) have been identified in 12 (35%) of these families. In a previous study, hMSH2 mutations were found in 21% of the same families. While the spectrum of mutations at the hMSH2 gene among HNPCC patients appears heterogeneous, a cluster of hMLH1 mutations has been found in the region encompassing exons 15 and 16, which accounts for 50% of all the independent hMLH1 mutations described to date and for > 20% of the unrelated HNPCC kindreds here analyzed. This unexpected finding has a great practical value in the clinical scenario of genetic services.

Adaptor Proteins, Signal Transducing↗