ORIGINAL ARTICLE TPX2 and AURKA promote 20q amplicon-driven colorectal adenoma to carcinoma progression Anke H Sillars-Hardebol, 1 Beatriz Carvalho, 1 Marianne Tijssen, 1 Jeroen A M Belie ¨n, 1 Meike de Wit, 1 Pien M Delis-van Diemen, 1 Fredrik Ponte ´n, 2 Mark A van de Wiel, 3,4 Remond J A Fijneman, 1 Gerrit A Meijer 1 ABSTRACT Background and objective Progression of a colorectal adenoma to invasive cancer occurs in a minority of adenomas and is the most crucial step in colorectal cancer pathogenesis. In the majority of cases, this is associated with gain of a substantial part of chromosome 20q, indicating that multiple genes on the 20q amplicon may drive carcinogenesis. The aim of this study was to identify genes located on the 20q amplicon that promote progression of colorectal adenoma to carcinoma. Design Functional assays were performed for 32 candidate driver genes for which a positive correlation between 20q DNA copy number and mRNA expression had been demonstrated. Effects of gene knockdown on cell viability, anchorage-independent growth, and invasion were analysed in colorectal cancer cell lines with 20q gain. Colorectal tumour protein expression was examined by immunohistochemical staining of tissue microarrays. Results TPX2, AURKA, CSE1L, DIDO1, HM13, TCFL5, SLC17A9, RBM39 and PRPF6 affected cell viability and/ or anchorage-independent growth. Chromosome 20q DNA copy number status correlated significantly with TPX2 and AURKA protein levels in a series of colorectal adenomas and carcinomas. Moreover, downmodulation of TPX2 and AURKA was shown to inhibit invasion. Conclusion These data identify TPX2 (20q11) and AURKA (20q13.2) as two genes located on distinct regions of chromosome 20q that promote 20q amplicon- driven progression of colorectal adenoma to carcinoma. Therefore the selection advantage imposed by 20q gain in tumour progression is achieved by gain-of-function of multiple cancer-related genesdknowledge that can be translated into novel tests for early diagnosis of progressive adenomas. INTRODUCTION Colorectal cancer (CRC) is the third most prevalent and second most fatal type of cancer in the Western world. It develops from normal colon epithelium through an adenoma precursor stage. Only 5% of these adenomas are estimated to progress to cancer, 1 a transition that requires significant biological changes that are facilitated by an enhanced rate of genomic instability. 23 Chromosomal aberrations are detected in w85% of CRCs and occur as non- random events, often involving gain of chromosome regions 8q, 13q and 20q, and loss of 4q, 8p, 17p and 18q. 45 We previously demonstrated that gain of the long arm of chromosome 20 (20q) is strongly asso- ciated with progression of colorectal adenoma to carcinoma. 6 The clinical relevance of 20q gain in cancer is emphasised by its association with a poor prognosis in CRC and other cancer types. 78 The fact that amplification of substantial parts of 20q is associated with progression of colorectal adenoma to carcinoma implies that increased DNA copy numbers of one or more genes must have functional consequences, most likely caused by < Additional materials are published online only. To view these files, please visit the journal online (http://dx.doi.org/ 10.1136/gutjnl-2011-301153). 1 Department of Pathology, VU University Medical Center, Amsterdam, The Netherlands 2 Department of Genetics and Pathology, The Rudbeck Laboratory, Uppsala University, Uppsala, Sweden 3 Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands 4 Department of Mathematics, VU University, Amsterdam, The Netherlands Correspondence to Dr Remond J A Fijneman, VU University Medical Center, Department of Pathology, CCA 1.08, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands; rja.fijneman@vumc.nl Revised 12 October 2011 Accepted 14 October 2011 Significance of this study What is already known about this subject? < Detection of colorectal tumours at an early (pre- malignant) stage of disease development is an effective approach for reducing colorectal cancer mortality. < Progression of colorectal adenomas to invasive cancer is a critical step in colorectal cancer pathogenesis, which occurs in a minority of only 5% of adenomas. < The transition of colorectal adenomas to carcinomas is driven by non-random molecular alterations, the most prominent of which is gain of a large region of chromosome 20q. < Aurora kinase A (AURKA) is considered to be one of several candidate genes that promote chromosome 20q amplicon-driven progression of adenoma to carcinoma. What are the new findings? < TPX2 (20q11), in addition to AURKA (20q13.2), is identified as a novel gene that promotes 20q amplicon-driven progression of colorectal adenoma to carcinoma. < The selection advantage imposed by gain of a large region of chromosome 20q in colorectal tumour progression is achieved by gain-of- function of multiple cancer-related genes, rather than being caused by a single driver gene. How might it impact on clinical practice in the foreseeable future? < Molecular screening tests for colorectal cancer may be fine-tuned to detect the minority of adenomas that are truly at high risk of progression. Colon 1568 Gut 2012;61:1568–1575. doi:10.1136/gutjnl-2011-301153 Published Online First 29 December 2011