Colorectal adenomas form a biologically and clinically distinct intermediate stage in development of colorectal cancer (CRC) from normal colon epithelium. Only 5% of adenomas progress into adenocarcinomas, indicating that malignant transformation requires other biological alterations than those involved in adenoma formation. The present study aimed to explore which cancer-related biological processes are affected during colorectal adenoma-to-carcinoma progression and to identify key genes within these pathways that can serve as tumor markers for malignant transformation. The activity of 12 cancer-related biological processes was compared between 37 colorectal adenomas and 31 adenocarcinomas, using the pathway analysis tool Gene Set Enrichment Analysis. Expression of six gene sets was significantly increased in CRCs compared to adenomas, representing chromosomal instability, proliferation, differentiation, invasion, stroma activation, and angiogenesis. In addition, 18 key genes were identified for these processes based on their significantly increased expression levels. For AURKA and PDGFRB, increased mRNA expression levels were verified at the protein level by immunohistochemical analysis of a series of adenomas and CRCs. This study revealed cancer-related biological processes whose activities are increased during malignant transformation and identified key genes which may be used as tumor markers to improve molecular characterization of colorectal tumors.Electronic supplementary materialThe online version of this article (doi:10.1007/s13277-009-0012-1) contains supplementary material, which is available to authorized users.

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 genes—knowledge that can be translated into novel tests for early diagnosis of progressive adenomas.

Background: Gain of a large segment of chromosome 20q is associated with progression of colorectal adenomas into carcinomas, implying that multiple genes on the 20q amplicon drive carcinogenesis. Candidate driver genes are expected to be expressed at mRNA and protein levels that correlate with the 20q amplicon DNA copy number status, while functionally affecting one or several cancer-related processes. Integration of CGH profiles with mRNA profiles of a series of colorectal tumors revealed thirty-two candidate genes whose DNA copy number status correlated with mRNA expression levels. Aim: To functionally analyse the effects of the candidate oncogenes on cancer-related processes by downregulation using siRNA strategies. Results: Downmodulation of TPX2 (20q11.2) and AURKA (20q13.2) mRNA expression in CRC cell lines with 20q gain affected cell viability, anchorage-independent growth, and invasion. Moreover, immunohistochemical evaluation demonstrated a significant correlation between their protein levels and 20q DNA copy number status in a series of colorectal adenomas and carcinomas. Conclusion: These data demonstrate that at least two genes located on distinct regions of chromosome 20q promote colorectal adenoma-to-carcinoma progression and indicate that TPX2, like AURKA, is a promising target for anti-cancer drug development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3042. doi:10.1158/1538-7445.AM2011-3042

BackgroundColorectal cancer develops in a multi-step manner from normal epithelium, through a pre-malignant lesion (so-called adenoma), into a malignant lesion (carcinoma), which invades surrounding tissues and eventually can spread systemically (metastasis). It is estimated that only about 5% of adenomas do progress to a carcinoma.AimThe present study aimed to unravel the biology of adenoma to carcinoma progression by mRNA expression profiling, and to identify candidate biomarkers for adenomas that are truly at high risk of progression.MethodsGenome-wide mRNA expression profiles were obtained from a series of 37 colorectal adenomas and 31 colorectal carcinomas using oligonucleotide microarrays. Differentially expressed genes were validated in an independent colorectal gene expression data set. Gene Set Enrichment Analysis (GSEA) was used to identify altered expression of sets of genes associated with specific biological processes, in order to better understand the biology of colorectal adenoma to carcinoma progression.ResultsmRNA expression of 248 genes was significantly different, of which 96 were upregulated and 152 downregulated in carcinomas compared to adenomas. Classification of adenomas and carcinomas using the expression of these genes showed to be very accurate, also when tested in an independent expression data set. Gene-sets associated with ageing (which is related to senescence) and chromosomal instability were upregulated, and a gene-set associated with fatty acid metabolism was downregulated in carcinomas compared to adenomas. Moreover, gene-sets associated with chromosomal location revealed chromosome 4q22 loss and chromosome 20q gain of gene-set expression as being relevant in this progression.Concluding remarkThese data are consistent with the notion that adenomas and carcinomas are distinct biological entities. Disruption of specific biological processes like senescence (ageing), maintenance of chromosomal instability and altered metabolism, are key factors in the progression from adenoma to carcinoma.Electronic supplementary materialThe online version of this article (doi:10.1007/s13402-011-0065-1) contains supplementary material, which is available to authorized users.

Colorectal cancer (CRC) is the second leading cause of cancer death in the western world. The majority of CRCs, which develop from adenoma precursor lesions, show gain of chromosome arm 20q, where BCL2L1 is located. BCL2L1 is an important apoptosis regulating gene that codes for both an anti-apoptotic (Bcl-x(L)) and a pro-apoptotic (Bcl-x(S)) splice variant. The aim of the present study was to investigate whether BCL2L1 contributes to 20q gain-driven colorectal adenoma-to-carcinoma progression. To this end, the functional role of BCL2L1 in cancer-related processes was investigated, and differences in BCL2L1 DNA, mRNA, and protein levels were compared between colorectal adenomas and CRCs, as well as between tumours with and without 20q gain. Down-modulation of BCL2L1 inhibited cell viability and anchorage-independent growth of CRC cells, while invasion was not affected. BCL2L1 DNA copy number and protein expression were increased in CRCs compared to adenomas (p = 0.00005 and p = 0.03, respectively), while mRNA expression was not. Differences in BCL2L1 protein expression were even more pronounced between tumours with and without 20q gain (p = 0.0001). In conclusion, BCL2L1 is functionally involved in several cancer-related processes and its protein expression is associated with 20q gain. This supports a role for 20q gain-dependent expression of BCL2L1 in colorectal adenoma-to-carcinoma progression. However, the absence of a direct correlation between BCL2L1 mRNA and protein expression implies that BCL2L1 protein expression is regulated at the post-transcriptional level by a distinct factor on the 20q amplicon (eg ZNF217, AURKA or miRNAs). Therefore, even though BCL2L1 affects CRC biology in a 20q gain-dependent manner, it is not likely to be a driver of chromosome 20q gain associated adenoma-to-carcinoma progression.