Aurora kinase A (AURKA) interaction with Wnt and Ras-MAPK signalling pathways in colorectal cancer.

Hyperactivation of Wnt and Ras-MAPK signalling are common events in development of colorectal adenomas. Further progression from adenoma-to-carcinoma is frequently associated with 20q gain and overexpression of Aurora kinase A (AURKA). Interestingly, AURKA has been shown to further enhance Wnt and Ras-MAPK signalling. However, the molecular details of these interactions in driving colorectal carcinogenesis remain poorly understood. Here we first performed differential expression analysis (DEA) of AURKA knockdown in two colorectal cancer (CRC) cell lines with 20q gain and AURKA overexpression. Next, using an exact algorithm, Heinz, we computed the largest connected protein-protein interaction (PPI) network module of significantly deregulated genes in the two CRC cell lines. The DEA and the Heinz analyses suggest 20 Wnt and Ras-MAPK signalling genes being deregulated by AURKA, whereof ß-catenin and KRAS occurred in both cell lines. Finally, shortest path analysis over the PPI network revealed eight 'connecting genes' between AURKA and these Wnt and Ras-MAPK signalling genes, of which UBE2D1, DICER1, CDK6 and RACGAP1 occurred in both cell lines. This study, first, confirms that AURKA influences deregulation of Wnt and Ras-MAPK signalling genes, and second, suggests mechanisms in CRC cell lines describing these interactions.

CSE1L, DIDO1 and RBM39 in colorectal adenoma to carcinoma progression.

BACKGROUND: Gain of chromosome 20q is an important factor in the progression from colorectal adenomas to carcinomas. Genes that drive 20q gain are expected to show correlation of mRNA and protein expression levels with 20q DNA copy number status while functionally influencing cancer processes. CSE1L, DIDO1 and RBM39 are located on the 20q amplicon and affect processes such as cell viability and anchorage-independent growth in colorectal cancer. This study aimed to investigate whether CSE1L, DIDO1 and RBM39 may drive 20q amplification. METHODS: Protein expression levels were examined by immunohistochemical evaluation of tissue microarrays containing a series of colorectal adenoma and carcinoma samples, which were characterized by genome-wide (microarray-based) DNA and mRNA profiling. RESULTS: CSE1L, DIDO1 and RBM39 mRNA expression levels correlated with chromosome 20q DNA copy number status. CSE1L protein expression was not associated with 20q gain, although its expression was increased in carcinomas compared to adenomas. DIDO1 and RBM39 protein expression was quite strong in the majority of tumors irrespective of 20q DNA copy number status. CONCLUSION: The lack of correlation between protein expression levels and 20q DNA copy number status implies that CSE1L, DIDO1 and RBM39 are merely passengers rather than drivers of chromosome 20q gain in colorectal adenoma-to-carcinoma progression.

Colorectal adenoma to carcinoma progression is accompanied by changes in gene expression associated with ageing, chromosomal instability, and fatty acid metabolism.

BACKGROUND: Colorectal 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. AIM: The 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. METHODS: Genome-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. RESULTS: mRNA 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 REMARK: These 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.

BCL2L1 has a functional role in colorectal cancer and its protein expression is associated with chromosome 20q gain.

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.

The adenoma hunt in colorectal cancer screening: defining the target.

Colorectal adenomas are precursor lesions of colorectal cancer. Different biological and metabolic processes contribute to adenomagenesis. Subsequent progression to carcinoma occurs in only about 5% of the cases. Detection and removal of all adenomas would reduce CRC incidence and mortality, but at the cost of major over-treatment. Classical morphological characteristics fail to accurately discriminate between adenomas that will become malignant and those that will not. Understanding the biology of cancer development will help to better characterize adenomas at high risk of progression, and subsequently establish triage tests that allow to safely reserve colonoscopy only for individuals at high probability of having truly high-risk colorectal adenomas. Screening tests based on genomic changes that affect relevant biological and metabolic processes hold most promise in this respect.

TPX2 and AURKA promote 20q amplicon-driven colorectal adenoma to carcinoma progression.

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.

Identification of key genes for carcinogenic pathways associated with colorectal adenoma-to-carcinoma progression.

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.