Gerrit A. Meijer

Copy Number Gain at 8q12.1-q22.1 is Associated with a Malignant Tumor Phenotype in Salivary Gland Myoepitheliomas

Salivary gland myoepithelial tumors are relatively uncommon tumors with an unpredictable clinical course. More knowledge about their genetic profiles is necessary to identify novel predictors of disease. In this study, we subjected 27 primary tumors (15 myoepitheliomas and 12 myoepithelial carcinomas) to genome‐wide microarray‐based comparative genomic hybridization (array CGH). We set out to delineate known chromosomal aberrations in more detail and to unravel chromosomal differences between benign myoepitheliomas and myoepithelial carcinomas. Patterns of DNA copy number aberrations were analyzed by unsupervised hierarchical cluster analysis. Both benign and malignant tumors revealed a limited amount of chromosomal alterations (median of 5 and 7.5, respectively). In both tumor groups, high frequency gains (≥20%) were found mainly at loci of growth factors and growth factor receptors (e.g., PDGF, FGF(R)s, and EGFR). In myoepitheliomas, high frequency losses (≥20%) were detected at regions of proto‐cadherins. Cluster analysis of the array CGH data identified three clusters. Differential copy numbers on chromosome arm 8q and chromosome 17 set the clusters apart. Cluster 1 contained a mixture of the two phenotypes (n = 10), cluster 2 included mostly benign tumors (n = 10), and cluster 3 only contained carcinomas (n = 7). Supervised analysis between malignant and benign tumors revealed a 36 Mbp‐region at 8q being more frequently gained in malignant tumors (P = 0.007, FDR = 0.05). This is the first study investigating genomic differences between benign and malignant myoepithelial tumors of the salivary glands at a genomic level. Both unsupervised and supervised analysis of the genomic profiles revealed chromosome arm 8q to be involved in the malignant phenotype of salivary gland myoepitheliomas.

Abstract 1197: Chromosomal aberrations implicated in colorectal adenoma to carcinoma progression as markers of high risk colorectal adenomas.

Background: Colorectal adenomas are precursor lesions of colorectal cancer. About 5% of colorectal adenomas are estimated to progress to colorectal cancer (CRC). The currently used histo-pathological characteristics to identify adenomas at risk of malignant progression, i.e. scoring of size ≥ 10mm, villous component or high grade dysplasia, are not sufficiently sensitive and specific and prone to inter-observer variability. Integrating molecular markers reflecting the underlying biology of CRC into the current classification system is expected to better characterize adenomas at high-risk of progression. Aim: Here we compared the prevalence of genetic changes, in particular DNA copy number changes, between advanced and non-advanced adenomas. Methods: Formalin-fixed paraffin-embedded tissue samples from 121 patients (mean age 65.4±11.6, 52.9% male) with colorectal adenomas (63 non-advanced adenomas and 58 advanced adenomas) were retrospectively collected from the archives of the department of pathology of the VU - University medical center (VUmc), Amsterdam, the Netherlands. DNA was extracted and DNA copy number analysis was performed using Multiplex Ligation-dependent Probe Amplification (MLPA), focusing on 7 chromosomal regions previously associated with adenoma-to-carcinoma progression, namely 8p, 15q, 17p and 18q loss and 8q,13q and 20q gain (1). Comparison of DNA copy number aberrations between sub-groups was done using a Chi-square test, or Fisher9s exact test when appropriate. For multivariate analysis logistic regression was used. Data analysis was performed using SPSS version 22 (IBM SPSS Statistics) and p-values below 0.05 were considered to be statistically significant (using two-sided tests). Results: Of the adenomas analyzed 23.1% (28/121) showed at least one gain or loss of the investigated chromosomal regions. Two or more chromosomal aberrations were present in 22.4 % (13/58) of the advanced adenomas and 1.6% (1/63) of the non-advanced adenomas (p=0,001). Since advanced colorectal adenomas are defined based on their histological characteristics ((tubulo)villous component and/or high degree dysplasia and/or ≥ 10mm), we searched for associations of these histological features with the analyzed chromosomal aberrations (CAE9s). Multivariate analysis showed that only gains of 13q and 20q were significantly associated with adenomas ≥ 10mm (p=0.01 and p=0.003, respectively) and losses of 18q were significantly associated with high-grade dysplasia (p=0.04). Conclusion: Our data indicate that DNA copy number alterations are not as frequent as expected in advanced adenomas and are also found in non-advanced and diminutive lesions. Combining histological and molecular features in adenoma follow-up studies could increase the knowledge on malignant potential of adenomas. (1) Hermsen et al, Gastroenterology, 2002; 123:1109-1119 Citation Format: Beatriz Carvalho, Begona Diosdado, Jochim S. Terhaar Sive Droste, Anne S. Bolijn, Meike de Wit, Myrthe van Burink, Remond JA Fijneman, Nicole CT van Grieken, Gerrit A. Meijer. Chromosomal aberrations implicated in colorectal adenoma to carcinoma progression as markers of high-risk colorectal adenomas. [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer: From Initiation to Outcomes; 2016 Sep 17-20; Tampa, FL. Philadelphia (PA): AACR; Cancer Res 2017;77(3 Suppl):Abstract nr A04.

Abstract 3086: Gain of chromosome 13 is a cause of CDK8 overexpression associated with colorectal adenoma to carcinoma progression

Introduction: Colorectal adenomas are common precursors of colorectal cancer (CRC). About only 5% of adenomas progress to cancer and this progression is mostly associated with overall onset/increase of chromosomal instability. Gain of 13q is often implicated in this progression of adenoma to carcinoma (1). Until recently however no genes were identified to be the drivers of this amplicon. Recently, Firestein and collaborators (2) showed that cyclin 8 (CDK8), at 13q12.13, functions as an oncogene in CRC. The aim of this study was to evaluate CDK8 gene dosage effects in colorectal adenoma to carcinoma progression. Material and methods: Sixty seven colorectal tumours (34 adenomas and 28 carcinomas) were analysed by array CGH (5k BAC platform, including contig coverage of 13q) and by expression microarray (30k Compugen library). Integration of DNA copy number dosage and gene expression was performed using the Ace-it tool (3). Results: In the tumours analysed we observed 13q copy number gain in 9% and 46% of adenomas and carcinomas, respectively. Integrating copy number and mRNA expression with the differential upregulation of genes between carcinomas and adenomas, provided us with a list of 43 genes. Within this list, CDK8 ranked 7th in significancy (p=0.003). Conclusions: Copy number gain of 13q has a gene dosage effect on CDK8 mRNA expression, indicating a role of this gene in colorectal adenoma to carcinoma progression. (1) Hermsen M, Postma C, Baak J, Weiss M, Rapallo A, Sciutto A, Roemen G, Arends JW, Williams R, Giaretti W, De Goeij A, Meijer G. Colorectal adenoma to carcinoma progression follows multiple pathways of chromosomal instability. Gastroenterology 2002 Oct;123(4):1109-19. (2) Firestein R, Bass AJ, Kim SY, Dunn IF, Silver SJ, Guney I, Freed E, Ligon AH, Vena N, Ogino S, Chheda MG, Tamayo P, Finn S, Shrestha Y, Boehm JS, Jain S, Bojarski E, Mermel C, Barretina J, Chan JA, Baselga J, Tabernero J, Root DE, Fuchs CS, Loda M, Shivdasani RA, Meyerson M, Hahn WC. CDK8 is a colorectal cancer oncogene that regulates beta-catenin activity. Nature 2008 Sep 25;455(7212):547-51. (3) van Wieringen WN, Belien JA, Vosse SJ, Achame EM, Ylstra B. ACE-it: a tool for genome-wide integration of gene dosage and RNA expression data. Bioinformatics. 2006 Aug 1;22(15):1919-20. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3086.