Using genome-wide expression profiling of a panel of 27 human mammary cell lines with different mechanisms of E-cadherin inactivation, we evaluated the relationship between E-cadherin status and gene expression levels. Expression profiles of cell lines with E-cadherin (CDH1) promoter methylation were significantly different from those with CDH1 expression or, surprisingly, those with CDH1 truncating mutations. Furthermore, we found no significant differentially expressed genes between cell lines with wild-type and mutated CDH1. The expression profile complied with the fibroblastic morphology of the cell lines with promoter methylation, suggestive of epithelial -mesenchymal transition (EMT). All other lines, also the cases with CDH1 mutations, had epithelial features. Three non-tumorigenic mammary cell lines derived from normal breast epithelium also showed CDH1 promoter methylation, a fibroblastic phenotype and expression profile. We suggest that CDH1 promoter methylation, but not mutational inactivation, is part of an entire programme, resulting in EMT and increased invasiveness in breast cancer. The molecular events that are part of this programme can be inferred from the differentially expressed genes and include genes from the TGFb pathway, transcription factors involved in CDH1 regulation (i.e. ZFHX1B, SNAI2, but not SNAI1, TWIST), annexins, AP1/2 transcription factors and members of the actin and intermediate filament cytoskeleton organisation.

Immunohistochemistry (IHC) of mismatch repair (MMR) proteins in colorectal tumors together with microsatellite analysis (MSI) can be helpful in identi-fying families eligible for mutation analysis. The aims were to determine sensitivity of IHC for MLH1, MSH2, and MSH6 and MSI analysis in tumors from known MMR gene mutation carriers; and to evaluate the use of tissue microarrays for IHC (IHC-TMA) of colon tumors in its ability to identify potential carriers of MMR gene mutations, and compare it with IHC on whole slides. IHC on whole slides was performed in colorectal tumors from 45 carriers of a germline mutation in one of the MMR genes. The TMA cohort consisted of 129 colon tumors from (suspected) hereditary nonpolyposis colorectal cancer (HNPCC) patients. Whole slide IHC analysis had a sensitivity of 89% in detecting MMR deficiency in carriers of a pathogenic MMR mutation. Sensitivity by MSI analysis was 93%. IHC can also be used to predict which gene is expected to harbor the mutation: for MLH1, MSH2, and MSH6, IHC on whole slides would have correctly predicted the mutation in 48%, 92%, and 75% of the cases, respectively. We propose a scheme for the diagnostic approach of families with (suspected) HNPCC. Comparison of the IHC results based on whole slides versus TMA, showed a concordance of 85%, 95%, and 75% for MLH, MSH2, and MSH6, respectively. This study therefore shows that IHC-TMA can be reliably used to simultaneously screen a large number of tumors from (suspected) HNPCC patients, at first in a research setting. Colorectal cancer (CRC) is the second most common cause of death because of malignancy in the Western world. The cause of CRC is multifactorial, involving hereditary and environmental factors and somatic genetic changes during tumor progression. 1 A family history of CRC is a clinically significant risk factor and may be found in up to 15% of all patients with CRC. 2 The most common hereditary CRC syndromes are familial adenomatous polyposis coli (FAP), accounting for Ͻ1% of CRC cases and HNPCC (hereditary nonpolyposis colorectal cancer), accounting for 1 to 6% of the cases. 3 HNPCC is an autosomal dominantly inherited disorder that is clinically defined by the Amsterdam Criteria. 4,5 In HNPCC, germline mutations have been identified in four DNA mismatch repair (MMR) genes, MSH2, 6 MLH1, 7 PMS2, 8 and MSH6. 9 -14 In 50 to 70% of the families fulfilling the Amsterdam criteria a germline mutation is detected in MLH1 or MSH2. 15,16 Germline mutations have been found in MSH6 in families with atypical HNPCC, ie, not entirely fulfilling the Amsterdam criteria. [11][12][13][14] Microsatellite instability (MSI) in colorectal tumors, first reported in 1993, [17][18][19] is caused by a failure of the DNA MMR machinery to repair errors occurring during DNA replication and leading to length alterations in simple, repetitive microsatellite sequences distributed throughout the genome. 20 According to international guidelines, a panel of five specific microsatellite markers has been recommended for MSI evalua...

Background: Abnormalities in Human Leukocyte Antigen (HLA) class I expression are common in colorectal cancer. Since HLA expression is required to activate tumor antigen-specific cytotoxic Tlymphocytes (CTL), HLA class I abnormalities represent a mechanism by which tumors circumvent immune surveillance. Tumors with high microsatellite instability (MSI-H) are believed to face strong selective pressure to evade CTL activity since they produce large amounts of immunogenic peptides. Previous studies identified the prevalence of HLA class I alterations in MSI-H tumors. However, those reports did not compare the frequency of alterations between hereditary and sporadic MSI-H tumors neither the mechanisms that led to HLA class I alterations in each subgroup.

Most human cancers show genetic instabilities leading to allelic imbalances, including loss of heterozygosity (LOH). Single nucleotide polymorphism (SNP) arrays can be used to detect LOH. Currently, these arrays require intact genomic DNA as obtained from frozen tissue; however, for most cancer cases, only low-quality DNA from formalin-fixed, paraffin-embedded (FFPE)

Background: Previous studies indicate that alterations in Human Leukocyte Antigen (HLA) class I expression are frequent in colorectal tumors. This would suggest serious limitations for immunotherapy-based strategies involving T-cell recognition. Distinct patterns of HLA surface expression might conceal different immune escape mechanisms employed by the tumors and are worth further study.