Putative tumor suppressor loci at 6q22 and 6q23-q24 are involved in the malignant progression of sporadic endocrine pancreatic tumors

Our previous comparative genomic hybridization study on sporadic endocrine pancreatic tumors (EPTs) revealed frequent losses on chromosomes 11q, 3p, and 6q. The aim of this study was to evaluate the importance of 6q losses in the oncogenesis of sporadic EPTs and to narrow down the smallest regions of allelic deletion. A multimodal approach combining polymerase chain reaction-based allelotyping, double-target fluorescence in situ hybridization, and comparative genomic hybridization was used in a collection of 109 sporadic EPTs from 93 patients. Nine polymorphic microsatellite markers (6q13 to 6q25-q27) were investigated, demonstrating a loss of heterozygosity (LOH) in 62.2% of the patients. A LOH was significantly more common in tumors >2 cm in diameter than below this threshold as well as in malignant than in benign tumors. We were able to narrow down the smallest regions of allelic deletion at 6q22.1 (D6S262) and 6q23-q24 (D6S310-UTRN) with LOH-frequencies of 50.0% and 41.2 to 56.3%, respectively. Several promising tumor suppressor candidates are located in these regions. Additional fluorescence in situ hybridization analysis on 46 EPTs using three locus-specific probes (6q21, 6q22, and 6q27) as well as a centromere 6-specific probe revealed complete loss of chromosome 6 especially in metastatic disease. We conclude that the two hot spots found on 6q may harbor putative tumor suppressor genes involved not only in the oncogenesis but maybe also in the malignant and metastatic progression of sporadic EPTs.

Somatic mutation and germline variants of MINPP1, a phosphatase gene located in proximity to PTEN on 10q23.3, in follicular thyroid carcinomas

Various genes have been identified to play a role in the pathogenesis of follicular thyroid tumors. Cowden syndrome is the only known familial syndrome with an increased risk of both follicular thyroid adenoma (FA) and carcinoma (FTC). Germline mutations in the tumor suppressor gene PTEN, which encodes a dual-specificity phosphatase, have been found in up to 80% of patients with Cowden syndrome suggesting a role of PTEN in the pathogenesis of follicular thyroid tumors. Although somatic intragenic mutations in PTEN, which maps to 10q23.3, are rarely found in follicular tumors, loss of heterozygosity (LOH) of markers within 10q22-24 occurs in about 25%. Recently, another phosphatase gene, MINPP1, has been localized to 10q23.3. MINPP1 has the ability to remove 3-phosphate from inositol phosphate substrates, a function that overlaps that of PTEN. Because of this overlapping function with PTEN and the physical location of MINPP1 to a region with frequent LOH in follicular thyroid tumors, we considered it to be an excellent candidate gene that could contribute to the pathogenesis of follicular thyroid tumors. We analyzed DNA from tumor and corresponding normal tissue from 23 patients with FA and 15 patients with FTC for LOH and mutations at the MINPP1 locus. LOH was identified in four malignant and three benign tumors. One of these FTCs with LOH was found to harbor a somatic c.122C > T or S41L mutation. We also found two germline sequence variants, c.809A > G (Q270R) and IVS3 + 34T > A. The c.809A > G variant was found in only one patient with FA but not in patients with FTC or normal controls. More interestingly, IVS3 + 34T > A was found in about 15% of FA cases and normal controls but not in patients with FTC. These results suggest a role for MINPP1 in the pathogenesis of at least a subset of malignant follicular thyroid tumors, and MINPP1 might act as a low penetrance predisposition allele for FTC.

Mutation and expression analyses reveal differential subcellular compartmentalization of PTEN in endocrine pancreatic tumors compared to normal islet cells

The pathogenesis of sporadic endocrine pancreatic tumors (EPTs) is still primarily unknown. Comparative genomic hybridization studies revealed loss of 10q in a significant number (nine of 31) of EPTs. The tumor suppressor gene PTEN lies on 10q23, and so, is a candidate to play some role in EPT pathogenesis. Germline PTEN mutations are found in Cowden and Bannayan-Riley-Ruvalcaba syndromes, whereas somatic mutations and deletions are found in a variety of sporadic cancers. The mutation and expression status of PTEN in EPTs has not yet been examined. Mutation analysis of the entire coding region of PTEN including splice sites was performed in 33 tumors, revealing one tumor with somatic L182F (exon 6). Loss of heterozygosity of the 10q23 region was detected in eight of 15 informative malignant (53%) and in none of seven benign EPTs. PTEN expression was assessed in 24 available EPTs by immunohistochemistry using a monoclonal anti-PTEN antibody. Of these 24, 23 tumors showed strong immunoreactivity for PTEN. Only the EPTs with PTEN mutation lacked PTEN protein expression. Although normal islet cells always exhibited predominantly nuclear PTEN immunostaining, 19 of 23 EPTs had a predominantly cytoplasmic PTEN expression pattern. Exocrine pancreatic tissue was PTEN-negative throughout. PTEN mutation is a rare event in malignant EPTs and PTEN protein is expressed in most (23 of 24) EPTs. Thus, intragenic mutation or another means of physical loss of PTEN is rarely involved in the pathogenesis of EPTs. Instead, either an impaired transport system of PTEN to the nucleus or some other means of differential compartmentalization could account for impaired PTEN function. Loss of heterozygosity of the 10q23 region is a frequent event in malignant EPTs and might suggest several hypotheses: a different tumor suppressor gene in the vicinity of PTEN might be principally involved in EPT formation; alternatively, 10q loss, including PTEN, seems to be associated with malignant transformation, but the first step toward neoplasia might involve altered subcellular localization of PTEN.

Differential nuclear and cytoplasmic expression of PTEN in normal thyroid tissue, and benign and malignant epithelial thyroid tumors

Germline mutations in PTEN (MMAC1/TEP1) are found in patients with Cowden syndrome, a familial cancer syndrome which is characterized by a high risk of breast and thyroid neoplasia. Although somatic intragenic PTEN mutations have rarely been found in benign and malignant sporadic thyroid tumors, loss of heterozygosity (LOH) has been reported in up to one fourth of follicular thyroid adenomas (FAs) and carcinomas. In this study, we examined PTEN expression in 139 sporadic nonmedullary thyroid tumors (55 FA, 27 follicular thyroid carcinomas, 35 papillary thyroid carcinomas, and 22 undifferentiated thyroid carcinomas) using immunohistochemistry and correlated this to the results of LOH studies. Normal follicular thyroid cells showed a strong to moderate nuclear or nuclear membrane signal although the cytoplasmic staining was less strong. In FAs the neoplastic nuclei had less intense PTEN staining, although the cytoplasmic PTEN-staining intensity did not differ significantly from that observed in normal follicular cells. In thyroid carcinomas as a group, nuclear PTEN immunostaining was mostly weak in comparison with normal thyroid follicular cells and FAs. The cytoplasmic staining was more intense than the nuclear staining in 35 to 49% of carcinomas, depending on the histological type. Among 81 informative tumors assessed for LOH, there seemed to be an associative trend between decreased nuclear and cytoplasmic staining and 10q23 LOH (P = 0.003, P = 0.008, respectively). These data support a role for PTEN in the pathogenesis of follicular thyroid tumors.

Immunohistochemical evidence of loss of PTEN expression in primary ductal adenocarcinomas of the breast

Germline mutations in PTEN, encoding a dual-specificity phosphatase on 10q23.3, cause Cowden syndrome (CS), which is characterized by a high risk of breast and thyroid cancers. Loss of heterozygosity of 10q22-24 markers and somatic PTEN mutations have been found to a greater or lesser extent in a variety of sporadic component and noncomponent cancers of CS. Among several series of sporadic breast carcinomas, the frequency of loss of flanking markers around PTEN is approximately 30 to 40%, and the somatic intragenic PTEN mutation frequency is <5%. In this study, we analyzed PTEN expression in 33 sporadic primary breast carcinoma samples using immunohistochemistry and correlated this to structural studies at the molecular level. Normal mammary tissue had a distinctive pattern of expression: myoepithelial cells uniformly showed strong PTEN expression. The PTEN protein level in mammary epithelial cells was variable. Ductal hyperplasia with and without atypia exhibited higher PTEN protein levels than normal mammary epithelial cells. Among the 33 carcinoma samples, 5 (15%) were immunohistochemically PTEN-negative; 6 (18%) had reduced staining, and the rest were PTEN-positive. In the PTEN-positive tumors as well as in normal epithelium, the protein was localized in the cytoplasm and in the nucleus (or nuclear membrane). Among the immunostain negative group, all had hemizygous PTEN deletion but no structural alteration of the remaining allele. Thus, in these cases, an epigenetic phenomenon such as hypermethylation, -ecreased protein synthesis or increased protein degradation may be involved. In the cases with reduced staining, 5 of 6 had hemizygous PTEN deletion and 1 did not have any structural abnormality. Finally, clinicopathological features were analyzed against PTEN protein expression. Three of the 5 PTEN immunostain-negative carcinomas were also both estrogen and progesterone receptor-negative, whereas only 5 of 22 of the PTEN-positive group were double receptor-negative. The significance of this last observation requires further study.

[Adverse internal medicine drug effects at hospital admission]

Hospital admissions due to adverse drug reactions are an important concern, but there are few data concerning the specific situation in Switzerland. During one year we therefore prospectively studied all admissions to our medical department to determine the profile. 138 of 2168 patients presented a total of 150 adverse drug reactions at hospitalisation (6.4%) and among them 65% of the admissions were directly related to adverse drug reaction. Age stratification revealed that with each decade of age there was an increasing risk of adverse drug reactions and that the patients were sicker (more diagnoses), were consuming more drugs and had longer stays. The majority of adverse drug reactions were type A reactions and therefore potentially preventable. Cardio- and cerebrovascular drugs (diuretics, ACE-inhibitors, platelet aggregation inhibiting therapy) accounted for 65% of the side effects. Analysed by affected organ system, the most frequent adverse drug reactions were gastrointestinal complications followed by dehydration (contracted extracellular fluid volume) and hypo-/hyperkalaemia. Non-compliance by the patients was less frequently at the origin of the admission than iatrogenic causes related to physician errors. The patients generally did not know the reasons, details and side effects of their medical treatment. Based on our data, we estimate that the national number of drug-related hospital admissions caused by inappropriate or unnecessary treatment is 12,000-16,000, with direct annual extra costs of 70-100 million Swiss francs. Adverse drug reactions therefore represent a serious medical and financial problem. Specialised computing systems designed to reduce these events should be introduced in hospitals and ambulatory care.

Clonal analysis of sporadic pancreatic endocrine tumours

The clonal composition of 34 benign and malignant sporadic pancreatic endocrine tumours (PETs) of female patients was studied using a sensitive polymerase chain reaction (PCR)-mediated non-isotopic clonality analysis, which is based on the inactivation patterns of polymorphic X-linked genes encoding the androgen receptor (AR) and phosphoglycerate kinase (PGK-1) proteins. Predigestion of DNA with the methylation-sensitive restriction endonuclease Hpa II permitted selective PCR amplification of the methylated (uncleaved) allele. Amplification was successful in 27 of 34 samples. Twenty patient samples were heterozygous for the AR microsatellite region or Bst XI polymorphic site of the PGK-1 gene, permitting analysis of clonality. A monoclonal pattern of X-chromosome inactivation was found in 7 of 20 PETs (35 per cent), since DNA pretreatment with Hpa II blocked amplification of one of the two AR or PGK-1 alleles. One additional tumour exhibited an oligoclonal inactivation pattern and two others a loss of heterozygosity (LOH) at the AR locus, indicative of monoclonality. A random pattern of X-chromosome inactivation and polyclonal cellular composition was observed in the remaining ten PETs (50 per cent). When comparing informative benign and malignant PETs, only 2/7 (29 per cent) benign tumours showed a monoclonal pattern and 8/13 (61 per cent) malignant tumours a monoclonal (5), oligoclonal (1), or LOH (2) pattern. The clonal composition of PETs was not associated with a particular growth pattern, proliferation index or immunohistochemical expression pattern. These findings suggest that PETs might initially represent poly-/oligoclonal neoplastic lesions which are eventually outgrown by a single, more aggressive cell clone with the potential for invasive growth and metastatic spread.

[ARDS in plasmodium vivax malaria]

Acute renal failure, disseminated intravascular coagulation, ARDS, hypoglycaemia, coma or epileptic seizures are manifestations of severe Plasmodium falciparum malaria. On the other hand, vivax malaria or benign tertian malaria is usually free from complications. In the present report we describe a case of acute tertian malaria with a severe and complicated course. In this situation bacterial coinfection should always be suspected and treated empirically with broad-spectrum antibiotics, until the results of cultures are available. Mixed plasmodial infection (P. vivax and P. falciparum) must be excluded by repeated and meticulous examination of blood smears. Newer techniques such as PCR processing or ParaSight F Test are mentioned.