Search

Genomic analysis of tumors is transforming our understanding of cancer. However, although a great deal of attention is paid to the accuracy of the cancer genomic data itself, less attention has been paid to the accuracy of the associated clinical information that renders the genomic data useful for research. In this brief communication, we suggest that omissions and errors in clinical annotations have a major impact on the interpretation of cancer genomic data. We describe our discovery of annotation omissions and errors when reviewing an already carefully annotated colorectal cancer gene expression dataset from our laboratory. The potential importance of clinical annotation omissions and errors was then explored using simulation analyses with an independent genomic dataset. We suggest that the completeness and veracity of clinical annotations accompanying cancer genomic data require renewed focus by the oncology research community, when planning new collections and when interpreting existing cancer genomic data.

Diffuse gastric cancer (DGC) is one of the two primary types of stomach cancer. Carriers of germline mutations in the gene encoding E-cadherin are predisposed to DGC. The primary aim of the present study was to determine if genomic instability is an early event in DGC and how it may lead to disease progression. Chromosomal aberrations in early intramucosal hereditary diffuse gastric cancer (eHDGC) were assessed using array comparative genomic hybridization (array CGH). Notably, no aneuploidy or other large-scale chromosomal rearrangements were detected. Instead, all aberrations affected small regions (< 4.8 Mb) and were predominantly deletions. Analysis of DNA sequence patterns revealed that essentially all aberrations possessed the characteristics of common fragile sites. These results and the results of subsequent immunohistochemical examinations demonstrated that unlike advanced DGC, eHDGCs is characterized by low levels of genomic instability at fragile sites. Furthermore, they express an active DNA damage response, providing a molecular basis for the observed indolence of eHDGC. This finding is an important step to understanding the pathology underlying natural history of DGC and supports a revision of the current definition of eHDGC as a malignant disease.

Background: We have recently reported an inverse relationship between colon cancer progression and tumour proliferative activity. Here, we extend our findings by evaluating the proliferative activity of liver metastatic lesions and primary colorectal cancers (CRC) that differ in their metastatic potential. Methods: Using an earlier established multi-gene proliferation signature (GPS), proliferative levels were analysed in 73 primary CRCs and 27 liver metastases. Results: Compared with primary CRCs, we observed a significantly lower expression of the GPS in liver metastases and confirmed their lower proliferative levels by quantitative RT–PCR and Ki-67 immunostaining. No difference could be detected in apoptotic indices as assessed by M30 immunostaining, indicating that the net growth rate is lower in metastases relative to primary tumours. Notably, relapsed primaries or those with established metastases had significantly lower proliferative activity than CRCs that were non-metastatic and did not relapse. Conclusion: Our results suggest that slow proliferation is a biological characteristic of both liver metastases and those primary tumours with the ability to metastasise. The delineation of the mechanisms underlying the inverse association between proliferation and CRC aggressiveness may be important for the development of new therapeutic strategies.

Compromised quality of formalin-fixed paraffin-embedded (FFPE)-derived DNA has compounded the use of archival specimens for array-based genomic studies. Recent technological advances have led to first successes in this field; however, there is currently no general agreement on the most suitable platform for the array-based analysis of FFPE DNA. In this study, FFPE and matched fresh-frozen (FF) specimens were separately analyzed with Affymetrix single nucleotide polymorphism (SNP) 6.0 and Agilent 4x44 K oligonucleotide arrays to compare the genomic profiles from the two tissue sources and to assess the relative performance of the two platforms on FFPE material. Genomic DNA was extracted from matched FFPE–FF pairs of normal intestinal epithelium from four patients and were applied to the SNP and oligonucleotide platforms according to the manufacturer-recommended protocols. On the Affymetrix platform, a substantial increase in apparent copy number alterations was observed in all FFPE tissues relative to their matched FF counterparts. In contrast, FFPE and matched FF genomic profiles obtained via the Agilent platform were very similar. Both the SNP and the oligonucleotide platform performed comparably on FF material. This study demonstrates that Agilent oligonucleotide array comparative genomic hybridization generates reliable results from FFPE extracted DNA, whereas the Affymetrix SNP-based array seems less suitable for the analysis of FFPE material.

The association between cell proliferation and the malignant potential of colon cancer is not well understood. Here, we evaluated this association using a colon-specific gene proliferation signature (GPS). The GPS was derived by combining gene expression data obtained from the analysis of a cancer cell line model and a published colon crypt profile. The GPS was overexpressed in both actively cycling cells in vitro and the proliferate compartment of colon crypts. K-means clustering was used to independantly stratify two cohorts of colon tumours into two groups with high and low GPS expression. Notably, we observed a significant association between reduced GPS expression and an increased likelihood of recurrence (P

Introduction Mounting molecular evidence suggests that invasive lobular carcinoma (ILC) is developing from in situ lesions, atypical lobular hyperplasia (ALH), and lobular carcinoma in situ (LCIS). However, little is known about the mechanisms promoting the progression of lobular breast cancer (LBC) to invasive disease. Here, we investigated whether c-Src kinase, an established inducer of invasive states, contributes to the progression from ALH/LCIS to ILC. Methods Immunochemistry for c-Src and other cancer-related molecules was performed on archived tissue specimens from 57 LBC patients. Relative c-Src activity was estimated by comparing fluorescence intensity of ILC with that of adjacent ALH/LCIS and nonneoplastic epithelia after staining with an antibody against active c-Src. Expression of active c-Src was correlated with markers of invasion and malignancy and with relapse among LBC patients. Results Levels of activated c-Src were increased in ILC relative to ALH/LCIS (1.63-fold ± 0.24 SD) and nonneoplastic epithelia (1.47 ± 0.18 SD). Increased c-Src levels correlated with the activation of c-Src downstream targets (Fak, Stat-3) and the expression of mesenchymal markers. ILC cells with activated c-Src co-expressed metastatic markers (Opn, Cxcr4) and included cells positive for the cancer stem cell marker Aldh1. A tendency for high c-Src levels (P = 0.072) was observed among the seven LBC patients with relapsed disease. Conclusions Our data indicate elevated c-Src activity in ILC relative to noninvasive neoplastic tissue. The associated molecular changes suggest that c-Src promotes LBC invasiveness by inducing an epithelial-mesenchymal transition. Therefore, c-Src antagonists might counteract the acquisition of invasiveness during LBC progression. Inhibition of c-Src may also affect ILC cells thought to have a high metastatic potential and to be capable of initiating/maintaining tumor growth. Together with the possible association between high c-Src levels and disease recurrence, our findings encourage the evaluation of c-Src antagonists for the treatment of LBC.

Tumour cells have to undergo gene expression changes in order to metastasise and adapt to a new site. We investigated these changes in liver metastases of colorectal cancer by using genome-wide microarray analysis to profile the expression of 48 primary tumours and 28 liver metastases. Statistical analysis of these expression profiles using the significance analysis of microarrays (SAM) method identified 778 genes differentially expressed between primary tumours and metastases. Gene ontology analysis revealed that genes associated with tissue remodelling and immune response were upregulated in metastases relative to primary tumours, whereas genes associated with proliferation and oxidative phosphorylation were downregulated. Quantitative real-time PCR confirmed the differential expression of selected genes, osteopontin, versican, ADAM17, CKS2, PRDX1, CXCR4, CXCL12, and LCN2. The upregulation of genes associated with tissue remodelling and immune response are likely to be involved in metastatic invasion and colonisation of the new site because these genes can promote tumour progression. However, downregulation of genes associated with proliferation suggests that proliferation in metastases was reduced relative to primary tumours.

Background The immune response has been proposed to be an important factor in determining patient outcome in colorectal cancer (CRC). Previous studies have concentrated on characterizing T cell populations in the primary tumour where T cells with regulatory effect (Foxp3+ Tregs) have been identified as both enhancing and diminishing anti-tumour immune responses. No previous studies have characterized the T cell response in the regional lymph nodes in CRC. Methods Immunohistochemistry was used to analyse CD4, CD8 or Foxp3+ T cell populations in the regional lymph nodes of patients with stage II CRC (n = 31), with (n = 13) or without (n = 18) cancer recurrence after 5 years of follow up, to determine if the priming environment for anti-tumour immunity was associated with clinical outcome. Results The proportions of CD4, CD8 or Foxp3+ cells in the lymph nodes varied widely between and within patients, and there was no association between T cell populations and cancer recurrence or other clinicopathological characteristics. Conclusions These data indicate that frequency of these T cell subsets in lymph nodes may not be a useful tool for predicting patient outcome.