Increased frequency of 20q gain and copy-neutral loss of heterozygosity in mismatch repair proficient familial colorectal carcinomas.

Many hereditary nonpolyposis colorectal cancers (CRCs) cannot be explained by Lynch syndrome. Other high penetrance genetic risk factors are likely to play a role in these mismatch repair (MMR)-proficient CRC families. Because genomic profiles of CRC tend to vary with CRC susceptibility syndromes, our aim is to analyze the genomic profile of MMR-proficient familial CRC to obtain insight into the biological basis of MMR-proficient familial CRC. We studied 30 MMR-proficient familial colorectal carcinomas, from 15 families, for genomic aberrations, including gains, physical losses, and copy-neutral loss of heterozygosity LOH (cnLOH) using SNP array comparative genomic hybridization. In addition, we performed somatic mutation analysis for KRAS, BRAF, PIK3CA and GNAS. The frequency of 20q gain (77%) is remarkably increased when compared with sporadic CRC, suggesting that 20q gain is involved in tumor progression of familial CRC. There is also a significant increase in the frequency of cnLOH and, as a consequence, a reduced frequency of physical loss compared with sporadic CRC. The most frequent aberrations observed included gains of 7p, 7q, 8q, 13q, 20p and 20q as well as physical losses of 17p, 18p and 18q. Most of these changes are also observed in sporadic CRC. Mutations in KRAS were identified in 37% of the MMR-proficient CRCs, and mutations in BRAF were identified in 16%. No mutations were identified in PIK3CA or chromosome 20 candidate gene GNAS. We show that the patterns of chromosomal instability of MMR-proficient familial CRC are clearly distinct from those from sporadic CRC. Both the increased gain on chromosome 20 and the increased levels of cnLOH suggest the presence of yet undiscovered germline defects that can, in part, underlie the cancer risk in these families.

Dual role of LOH at MMR loci in hereditary non-polyposis colorectal cancer?

hMLH1 and hMSH2 can be considered tumor suppressor genes, as both alleles must be inactivated in order to lose the mismatch repair (MMR) function. In this regard, it has been proposed that LOH at MMR loci is a common Knudson's second-hit mechanism in HNPCC patients. However, experimental evidence supporting this view is scarcely found in the literature. We have performed a comprehensive analysis of LOH in 45 HNPCC tumors carrying a germline alteration in MMR loci. Overall, we have detected LOH at MMR loci in 56% of the cases. However, up to 40% of the LOH events targeted the mutant allele, arguing against a second-hit role in these tumors. Interestingly, the age at diagnosis was significantly older in these patients. To explain this and previous data, we propose a dual role for LOH at MMR loci in HNPCC.

Duodenal carcinoma in MUTYH-associated polyposis.

Bi-allelic germline mutations in the MUTYH gene give rise to multiple adenomas and an increased incidence of colorectal cancer. In addition, duodenal adenomas and other extra-colonic manifestations have been described in MUTYH-associated polyposis (MAP) patients. We describe two patients with bi-allelic MUTYH gene mutations with duodenal carcinoma. The tumour in Patient A was detected during evaluation of non-specific abdominal complaints. Patient B was already diagnosed with tens of adenomas and a colon carcinoma, when a duodenal neoplasm was detected. The identification of somatic G>T mutations in codon 12 of the K-RAS2 gene provides evidence that the duodenal lesions were induced by MUTYH deficiency. Studies in larger series of MAP patients are needed to investigate the risk of upper-gastro-intestinal malignancies and to determine further guidelines for endoscopical surveillance.

Bias in detection of instability of the (C)8 mononucleotide repeat of MSH6 in tumours from HNPCC patients.

Recently, we and others reported instability in the (C)8 repeat in exon 5 of MSH6 as a preferential target for somatic mutations in tumours from MSH6 germline mutation carriers. Here, we report that in 45% of tumours from MLH1, MSH2 and MSH6 germline mutation carriers no sequence change in the (C)8 repeat of MSH6 was found upon DNA sequencing analysis of PCR products with a shift in electrophoresis mobility. Using "standard" PCR primers a high frequency of instability (50-86%) of the (C)8 repeat was found, but using a modified PCR reverse primer, accomplishing modulation of non-templated addition of adenine during in vitro PCR amplification by the Taq polymerase, a markedly lower frequency of instability was found in tumours from MLH1, MSH2 and MSH6 mutation carriers (6, 13 and 40%, respectively). Furthermore, a significant difference of the frequency of instability of the (C)8 repeat in tumours from MSH6 mutation carriers was found compared to MLH1, MSH2 mutation carriers. These results might have important implications for the detection of instability of other short mononucleotide repeats, e.g. TGFbetaRII, BAX, IGFRII, PTEN, BRCA2.

Identification of HNPCC by molecular analysis of colorectal and endometrial tumors.

Hereditary nonpolyposis colorectal cancer (HNPCC, Lynch syndrome) is a dominantly inherited syndrome characterized by the development of colorectal cancer, endometrial cancer and other cancers and the presence of microsatellite instability (MSI) in tumors. The Bethesda guidelines have been proposed for the identification of families suspected of HNPCC that require further molecular analysis. We have evaluated the yield of MSI-analysis in a large series of Dutch families suspected of HNPCC. We also analysed whether the loss of mismatch repair (MMR) protein detected by immunohistochemistry (IHC) of colorectal cancer (CRC) and endometrial cancer correlated with the presence of MSI and/or a MMR gene mutation. The results showed that the Bethesda criteria with a few modifications are appropriate to identify families eligible for genetic testing. In addition, we found that MSI and IHC-analysis of CRC using antibodies against MLH1, MSH2, MSH6 and PMS2 proteins are equally effective for identifying carriers of the known MMR gene defects. However, as long as the role of other putative MMR genes in hereditary CRC has not been elucidated, IHC-analysis cannot completely replace MSI. For this reason, we prefer MSI-analysis as first step in families suspected of HNPCC. On the other hand, in families fulfilling the revised Amsterdam criteria in which the probability of detecting a mutation is relatively high, we would recommend IHC as first diagnostic step because the result might predict the specific underlying MMR gene mutation. MSI or IHC-analysis of endometrial cancer alone was found to be less sensitive compared with these tests performed in colorectal cancer. Therefore, probably the best approach in the analysis of this cancer is to perform both techniques. The identification of HNPCC is important as it makes it possible to target effective preventative measures. Our studies showed that MSI and IHC analysis of colorectal and endometrial cancer, are reliable cost-effective tools that can be used to identify patients with HNPCC.

[Organ donation in a general hospital]. / Orgaandonatie in een algemeen ziekenhuis.

There is an acute shortage of donor organs for transplantation in The Netherlands. It is presumed that many potentially available organs are lost due to insufficient alertness. A retrospective study was made of the results of the procedure for obtaining permission for post-mortem donorship. Records of patients succumbed in the Intensive Care Unit in the period 1983-1987 were checked to ascertain whether these patients had met the current selection criteria for donorship. According to these criteria, 104 of the 531 deceased patients had been suitable. Death had been due to irreversible brain damage in 71 cases, to CVA in 29, to a primary brain tumour in three and to an intoxication in one. The donation procedure was followed in 53 cases of death. In 20 cases relatives refused permission and in 12 there were insuperable practical and technical difficulties. Relatives of 19 deceased patients were not asked for permission for post-mortem donorship. Once the procedure for obtaining permission for post-mortem donorship was implemented according to protocol and on a multidisciplinary basis, the proportion of cases in which requesting permission was omitted fell from 37% to 3%. Greater alertness of those involved to the possibilities of organ donation and good organization result in a growing number of organs available for transplantation, reducing an acute shortage.

High frequency of copy-neutral LOH in MUTYH-associated polyposis carcinomas.

Genetic instability is known to drive colorectal carcinogenesis. Generally, a distinction is made between two types of genetic instability: chromosomal instability (CIN) and microsatellite instability (MIN or MSI). Most CIN tumours are aneuploid, whereas MSI tumours are considered near-diploid. However, for MUTYH-associated polyposis (MAP) the genetic instability involved in the carcinogenesis remains unclear, as near-diploid adenomas, aneuploid adenomas and near-diploid carcinomas have been reported. Remarkably, our analysis of 26 MAP carcinomas, using SNP arrays and flow sorting, showed that these tumours are often near-diploid (52%) and mainly contain chromosomal regions of copy-neutral loss of heterozygosity (LOH) (71%). This is in contrast to sporadic colon cancer, where physical loss is the main characteristic. The percentage of chromosomal gains (24%) is comparable to sporadic colorectal cancers with CIN. Furthermore, we verified our scoring of copy-neutral LOH versus physical loss in MAP carcinomas by two methods: fluorescence in situ hybridization, and LOH analysis using polymorphic markers on carcinoma fractions purified by flow sorting. The results presented in this study suggest that copy-neutral LOH is an important mechanism in the tumorigenesis of MAP.

Identification of MEN1 and HRPT2 somatic mutations in paraffin-embedded (sporadic) parathyroid carcinomas.

OBJECTIVE: Parathyroid carcinoma remains difficult to diagnose. Recently, it has been shown that mutations in the HRPT2 gene (encoding parafibromin) are associated with the development of parathyroid carcinoma. Although MEN1 is not typically thought to be involved in carcinoma formation, parathyroid carcinoma may be an extremely rare feature of the multiple endocrine neoplasia type 1 (MEN1) syndrome. We recently concluded that loss of heterozygosity (LOH) of the MEN1 gene is present in a relatively large number of parathyroid carcinomas, often in combination with LOH at the HRPT2 locus. The aim of this study was to evaluate the role of MEN1 and HRPT2 mutations in sporadic parathyroid tumours fulfilling histological criteria for malignancy. PATIENTS AND DESIGN: Formalin-fixed, paraffin-embedded (FFPE) parathyroid carcinoma tissue from 28 cases identified in the period 1985-2000 in the Netherlands was studied. HRPT2 (27/28 cases) and MEN1 (23/28 cases) were analysed by direct sequencing. RESULTS: Somatic MEN1 mutations were found in three of 23 (13%) sporadic parathyroid carcinoma cases; these consisted of one missense and two frameshift mutations. One of the latter two cases displayed lymph-node and lung metastases during follow-up. Six HRPT2 mutations were found in 4/27 cases (15%): five were truncating mutations and one was a missense mutation. Consistent with previously published reports, we found double mutations (2x) and germline mutations (2x) in apparently sporadic parathyroid carcinomas. CONCLUSIONS: These results suggest that not only HRPT2 but also MEN1 mutations may play a role in sporadic parathyroid cancer formation.

Therapy with antibodies against CD40L (CD154) and CD44-variant isoforms reduces experimental autoimmune encephalomyelitis induced by a proteolipid protein peptide.

Interactions between mononuclear cells are required for the formation of inflammatory infiltrates in the CNS and the activation of cellular effector functions provoking demyelination in MS. Membrane-expressed costimulatory molecules are crucial to such interactions. We therefore investigated whether two costimulatory molecules, CD40L (CD154, expressed on activated CD4-possible T cells) and selected CD44-variant isoforms (expressed on activated CD4-positive T cells), are targets for immunotherapy in MS. The model of experimental autoimmune encephalomyelitis (EAE) induced in SJL-mice by immunization with a peptide derived from the proteolipid protein (PLP139-151) was optimized to address these questions. A previous observation that anti-CD40L (CD154) monoclonal antibodies can effectively prevent EAE in this model was confirmed, and extended by demonstrating that CD40 is expressed by cells of the monocytic lineage infiltrating the spinal cord. In vivo treatment with antibody against the standard isoform of CD44 (CD44s or CD44H) did not affect disease burden. In contrast, combined treatment with antibodies against the isoforms CD44v6, v7 and v10, which are thought to be involved in inflammatory processes, reduced the disease burden considerably. In addition, CD44v10-expressing cells were detected in the spinal cord. These data support the idea that CD40-CD40L interactions form a target for immunotherapy of MS, and indicate that cells expressing CD44v6, v7 and/or v10-containing isoforms have such potential as well.