Annette Gylling

Is gastric cancer part of the tumour spectrum of hereditary non‐polyposis colorectal cancer? A molecular genetic study

Background: Gastric cancer is the second most common extracolonic malignancy in individuals with hereditary non-polyposis colorectal cancer (HNPCC)/Lynch syndrome. As gastric cancer is relatively common in the general population as well, it is not clear whether or not gastric cancer is a true HNPCC spectrum malignancy. Aim: To determine whether or not gastric cancer is a true HNPCC spectrum malignancy. Subjects and methods: The molecular and clinicopathological profiles of gastric cancers (n = 13) from HNPCC mutation carriers were evaluated and compared with the profiles of sporadic gastric cancers (n = 46) stratified by histology and microsatellite instability (MSI) status. Results: This study on sporadic and HNPCC gastric cancers revealed several important universal associations. Loss of heterozygosity in the adenomatous polyposis coli (APC) region was associated with intestinal histology regardless of the MSI (p = 0.007). KRAS-mutations (p = 0.019) and frameshift mutations in repeat tracts of growth-regulatory genes (p<0.001) were associated with MSI tumours being absent in microsatellite stable (MSS) tumours. The average number of methylated tumour suppressor gene loci among the 24 genes studied (methylation index) was higher in MSI than in MSS tumours regardless of histology (p<0.001). Gastric cancers from HNPCC mutation carriers resembled sporadic intestinal MSI gastric cancers, except that MLH1 promoter methylation was absent (p<0.001) and the general methylation index was lower (p = 0.038), suggesting similar, but not identical, developmental pathways. All these lacked the mismatch repair protein corresponding to the germline mutation and displayed high MSI. Conclusion: The present molecular evidence, combined with the previous demonstration of an increased incidence relative to the general population, justify considering gastric cancers as true HNPCC spectrum malignancies.

Large genomic rearrangements and germline epimutations in Lynch syndrome.

In one‐third of families fulfilling the Amsterdam criteria for hereditary nonpolyposis colorectal cancer/Lynch syndrome, and a majority of those not fulfilling these criteria point mutations in DNA mismatch repair (MMR) genes are not found. The role of large genomic rearrangements and germline epimutations in MLH1, MSH2 and MSH6 was evaluated in 2 such cohorts. All 45 index patients were mutation‐negative by genomic sequencing and testing for a prevalent population‐specific founder mutation, and selectively lacked MMR protein expression in tumor tissue. Eleven patients (“research cohort”) represented 11 mutation‐negative families among 81 verified or putative Lynch syndrome families from the nation‐wide Hereditary Colorectal Cancer Registry of Finland. Thirty‐four patients from 33 families (“clinic‐based cohort”) represented suspected Lynch syndrome patients tested for MMR gene mutations in a diagnostic laboratory during 2004–2007. Multiplex ligation‐dependent probe amplification (MLPA) and methylation‐specific (MS)‐MLPA were used to detect rearrangements and epimutations, respectively. Large genomic deletions occurred in 12/45 patients (27%), being present in 3/25 (12%), 9/16 (56%) and 0/4 (0%) among index patients lacking MLH1, MSH2 or MSH6 expression, respectively. Germline epimutations of MLH1, one of which coexisted with a genomic deletion, occurred in 2 patients (4%) and were accompanied by monoallelic expression in mRNA. Large genomic deletions (mainly MSH2) and germline epimutations (MLH1) together explain a significant fraction of point mutation‐negative families suspected of Lynch syndrome and are associated with characteristic clinical and family features. Our findings have important implications in the diagnosis and management of such families.

Differential cancer predisposition in Lynch syndrome: insights from molecular analysis of brain and urinary tract tumors

Hereditary non-polyposis colorectal carcinoma (Lynch syndrome) is among the most common hereditary cancers in man and a model of cancers arising through deficient DNA mismatch repair (MMR). Lynch syndrome patients are predisposed to different cancers in a non-random fashion, the basis of which is poorly understood. We addressed this issue by determining the molecular profiles for different tumors from a nationwide cohort of Lynch syndrome families (approximately 150 tumors in total). We focused on some less prevalent cancers, affecting the brain (n = 7) and urinary tract (five bladder and five ureter uroepithelial cancers and four kidney adenocarcinomas), and compared their molecular characteristics to those of the most common cancers, colorectal, gastric and endometrial adenocarcinomas, from the same families. Despite origin from verified MMR gene mutation carriers, the frequency of high-level microsatellite instability in tumors varied between high (100-96% for ureter, stomach and colon), intermediate (63-60% for endometrium and bladder) and low (25-0% for kidney and brain). In contrast to gastrointestinal and endometrial carcinomas, active (nuclear) beta-catenin was rare and KRAS mutations were absent in brain and urological tumors. Compared with other tumors, frequent stabilization of p53 protein characterized urinary tract cancers. Promoter methylation of tumor suppressor genes discriminated the tumors in an organ-specific manner. Our findings suggest that different Lynch syndrome tumors develop along different routes. Uroepithelial cancers of the ureter (and bladder to lesser extent) share many characteristics of MMR deficiency-driven tumorigenesis, whereas brain tumors and kidney adenocarcinomas follow separate pathways.

Molecular analysis of endometrial tumorigenesis: importance of complex hyperplasia regardless of atypia.

Purpose: Endometrial carcinoma (EC) is common in the population and the most frequent extracolonic malignancy in hereditary nonpolyposis colorectal carcinoma (HNPCC)/Lynch syndrome. We characterized precursor lesions of endometrioid EC to identify markers of malignant transformation and tumor progression. Experimental Design: Serial specimens of normal endometrium, simple hyperplasia, complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma obtained during a 10-year surveillance of DNA mismatch repair (MMR) gene mutation carriers (together 110 samples) were molecularly profiled and compared with a sporadic reference series of endometrial specimens taken for nonmalignant reasons (62 samples). Results: Among MMR gene mutation carriers, decreased MMR protein expression was present in 7% in normal endometrium, 40% in simple hyperplasia, 100% in complex hyperplasia without atypia, 92% in complex hyperplasia with atypia, and 100% in endometrial carcinoma. Microsatellite instability frequencies were lower (6%, 17%, 67%, 38%, and 64%, respectively). Among 24 tumor suppressor genes, the number of methylated loci increased from normal endometrium to simple hyperplasia to complex hyperplasia (complex hyperplasia without atypia/complex hyperplasia with atypia) in both Lynch syndrome and reference series. The most frequently methylated genes were CDH13, RASSF1A, and GSTP1. In MMR gene mutation carriers, MMR and methylation defects appeared up to 12 years before endometrial carcinoma. Conclusions: Molecular changes in endometrial tissue are detectable several years before endometrial carcinoma in genetically predisposed individuals. Abnormal MMR and methylation classify normal endometrium and simple hyperplasia into one category and complex hyperplasia without atypia, complex hyperplasia with atypia, and endometrial carcinoma into another, suggesting that, contrary to a traditional view, complex hyperplasia without atypia and complex hyperplasia with atypia are equally important as precursor lesions of endometrial carcinoma. (Clin Cancer Res 2009;15(18):5772–83)

Patterns of PIK3CA alterations in familial colorectal and endometrial carcinoma

While the phosphatidylinositol 3‐kinase (PI3K)/AKT signaling pathway is known to be activated in multiple sporadic cancers, the role of this pathway in familial tumors is mostly unknown. We searched for alterations in the catalytic domain of PI3K (PIK3CA), PTEN and KRAS, all of which may contribute to PI3K/AKT pathway activation, in a total of 160‐familial colorectal (CRC) and endometrial carcinomas (EC), stratified by the presence vs. absence of germline mutations in DNA mismatch repair (MMR) genes. PIK3CA alterations (consisting of point mutations or low‐level amplification, which were mutually exclusive with 1 exception) occurred in 10/70 (14%) of CRCs and 19/90 (21%) of ECs. Within ECs, amplification was significantly associated with the subgroup lacking germline mutations in MMR genes (familial site‐specific endometrial cancer) (p = 0.015). Decreased or lost PTEN expression was characteristic of endometrial tumourigenesis (51/81, 63%, in EC compared with 24/62, 39%, in CRC, p = 0.004) and KRAS mutations of colorectal tumourigenesis (19/70, 27% in CRC vs. 9/89, 10%, in EC, p = 0.006) regardless of the MMR gene mutation status. PIK3CA alterations frequently coexisted with PTEN or KRAS changes. Combined with published studies on sporadic tumors, our data broaden the understanding of the role for PI3K pathway genes in human tumorigenesis.

Breast carcinoma and Lynch syndrome: molecular analysis of tumors arising in mutation carriers, non-carriers, and sporadic cases

IntroductionBreast carcinoma is the most common cancer in women, but its incidence is not increased in Lynch syndrome (LS) and studies on DNA mismatch repair deficiency (MMR) in LS-associated breast cancers have arrived at conflicting results. This study aimed to settle the question as to whether breast carcinoma belongs to the LS tumor spectrum.MethodsMMR status and epigenetic profiles were determined for all available breast carcinomas identified among 200 LS families from a nation-wide registry (23 tumors from mutation carriers and 18 from non-carriers). Sporadic breast carcinomas (n = 49) and other cancers (n = 105) from MMR gene mutation carriers were studied for comparison.ResultsThe proportion of breast carcinomas that were MMR-deficient based on absent MMR protein, presence of microsatellite instability, or both was significantly (P = 0.00016) higher among breast carcinomas from mutation carriers (13/20, 65%) compared to non-carriers (0/14, 0%). While the average age at breast carcinoma diagnosis was similar in carriers (56 years) and non-carriers (54 years), it was lower for MMR-deficient versus proficient tumors in mutation carriers (53 years versus 61 years, P = 0.027). Among mutation carriers, absent MMR protein was less frequent in breast carcinoma (65%) than in any of seven other tumor types studied (75% to 100%). Tumor suppressor promoter methylation patterns were organ-specific and similar between breast carcinomas from mutation carriers and non-carriers.ConclusionsBreast carcinoma from MMR gene mutation carriers resembles common breast carcinoma in many respects (for example, general clinicopathological and epigenetic profiles). MMR status makes a distinction: over half are MMR-deficient typical of LS spectrum tumors, while the remaining subset which is MMR-proficient may develop differently. The results are important for appropriate surveillance in mutation carriers and may be relevant for LS diagnosis in selected cases.

Promoter-specific alterations of APC are a rare cause for mutation-negative familial adenomatous polyposis.

In familial adenomatous polyposis (FAP), 20% of classical and 70% of attenuated/atypical (AFAP) cases remain mutation‐negative after routine testing; yet, allelic expression imbalance may suggest an APC alteration. Our aim was to determine the proportion of families attributable to genetic or epigenetic changes in the APC promoter region. We studied 51 unrelated families/cases (26 with classical FAP and 25 with AFAP) with no point mutations in the exons and exon/intron borders and no rearrangements by multiplex ligation‐dependent probe amplification (MLPA, P043‐B1). Promoter‐specific events of APC were addressed by targeted resequencing, MLPA (P043‐C1), methylation‐specific MLPA, and Sanger sequencing of promoter regions. A novel 132‐kb deletion encompassing the APC promoter 1B and upstream sequence occurred in a classical FAP family with allele‐specific APC expression. No promoter‐specific point mutations or hypermethylation were present in any family. In conclusion, promoter‐specific alterations are a rare cause for mutation‐negative FAP (1/51, 2%). The frequency and clinical correlations of promoter 1B deletions are poorly defined. This investigation provides frequencies of 1/26 (4%) for classical FAP, 0/25 (0%) for AFAP, and 1/7 (14%) for families with allele‐specific expression of APC. Clinically, promoter 1B deletions may associate with classical FAP without extracolonic manifestations.

Desmoid tumor patients carry an elevated risk of familial adenomatous polyposis

The prevalence of desmoid tumors among patients with familial adenomatous polyposis (FAP) is at least 10%, and the prevalence of FAP among desmoid patients varies between 7.5–16%.

Abstract 1910: 3′UTR poly(T/U) tract deletions and altered expression of EWSR1 are a hallmark of mismatch repair-deficient cancers.

Background: Microsatellite instability (MSI), the genome-wide accumulation of DNA replication errors, is the hallmark lesion of DNA mismatch repair (MMR) deficient cancers, present in Lynch syndrome (LS)-related and 10-20% of sporadic colorectal (CRC), gastric and endometrial cancers. MSI testing is widely used to guide clinical management but the functional significance of MSI at distinct genic loci remains largely elusive. Here, we characterize a novel MSI target locus consisting of a mononucleotide (T/U)16 tract located in the 3’untranslated region (UTR) of the Ewing sarcoma break point region 1 (EWSR1) gene (EWS16T). Methods: The diagnostic accuracy of EWS16T to identify MMR-deficient cancers was determined by analyzing 319 cancers (240 colorectal, 72 gastric, 7 endometrial) from two different populations. The functional consequences of EWS16T contractions were assessed in vitro (siRNA-mediated poly(A) site selection and pull-down assays) and in vivo (mRNA and protein expression by qPCR and tissue microarray analysis). Results: The EWS16T locus discriminates MMR-proficient (n=128) from deficient (n=191) cancers with perfect diagnostic sensitivity (100%) and specificity (100%). Biochemical analyses indicate that EWS16T contractions alter poly(A) site selection by promoting SFPQ-mediated distal poly(A) site usage in EWSR1 pre-mRNAs and result in decreased mRNA as well as EWS protein expression. In contrast to their MMR-proficient counterparts (n=64), MMR-deficient, LS-related CRC (n=94) display altered subcellular localization of EWS (p Conclusions: The EWS16T locus represents a novel, quasi-monomorphic MSI target locus to accurately identify both hereditary and sporadic MMR-deficient cancers. Contractions therein affect multiple regulatory mechanisms implicating the RNA-/DNA-binding Ewing sarcoma protein in MSI-associated colorectal tumorigenesis. Citation Format: Salvatore Piscuoglio, Shivendra Kishore, Michal Kovac, Annette Gylling, Friedel Wenzel, Francesca Trapani, Hans Joerg Altermatt, Valentina Mele, Giancarlo Marra, Paivi Peltomaki, Luigi Terracciano, Mihaela Zavolan, Karl Heinimann. 3′UTR poly(T/U) tract deletions and altered expression of EWSR1 are a hallmark of mismatch repair-deficient cancers. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1910. doi:10.1158/1538-7445.AM2013-1910

Abstract 5018: Genetic and epigenetic investigation of breast carcinoma arising in Lynch syndrome families

Breast carcinoma is the most common cancer type in females, but its incidence is generally not increased in Lynch syndrome (LS). Deficient DNA mismatch repair (MMR) is a hallmark of LS tumors that are unequivocal manifestations of the syndrome (e.g., colorectal and breast carcinoma). Because of controversial study results, it is unclear at present whether or not breast carcinoma is specifically associated with LS. We addressed this question by determining the genetic and epigenetic profiles for all available breast carcinomas from LS families from a nation-wide registry, including 24 tumors from MMR gene mutation carriers and 17 tumors from non-carriers. The average age at breast carcinoma diagnosis was similar in mutation carriers and non-carriers (56 years for each). Among breast carcinomas from mutation carriers, 43% showed loss of MMR protein corresponding to the germline mutation, and high-degree microsatellite instability (MSI-H) was present in 36%. Moreover, in mutation carriers, the age at diagnosis was lower for breast carcinomas that were MMR-deficient (by absent MMR protein and/or MSI present) compared to MMR proficient tumors (51 vs. 60 years, p= 0.031). Breast carcinomas showed frequent inactivation of tumor suppressor genes (TSG) by promoter methylation. The average number of methylated TSGs out of 24 per tumor was 3.1 for mutation carriers and 2.8 for non-carriers. The gene-specific distribution of methylation was also similar between the two breast tumor sets. In mutation carriers, the most frequently methylated TSGs were RASSF1 (77%), APC (45%), CDH13 (45%), GSTP1 (32%) and CDKN2B (27%). In non-carriers, the respective frequencies were 75%, 47%, 59%, 35%, and 29%. When compared to tumors arising in other organs from LS mutation carriers, methylation of CDKN2B was seen as a particular characteristic of breast tumorigenesis. Our investigation shows that TSG promoter methylation is a common characteristic of breast carcinomas arising in LS and affects mutation carriers and non-carriers with comparable overall rates and gene-specific distributions. Analysis of MMR protein expression and MSI revealed that while many breast carcinomas from LS mutation carriers follow MMR-driven tumorigenesis characteristic of tumors of the LS spectrum in general, a significant subset of breast tumors also exists that appears to arise and progress along separate pathways. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5018. doi:1538-7445.AM2012-5018