Loss of Expression and Promoter Methylation of SLIT2 Are Associated with Sessile Serrated Adenoma Formation.

Serrated adenomas form a distinct subtype of colorectal pre-malignant lesions that may progress to malignancy along a different molecular pathway than the conventional adenoma-carcinoma pathway. Previous studies have hypothesised that BRAF mutation and promoter hypermethylation plays a role, but the evidence for this is not robust. We aimed to carry out a whole-genome loss of heterozygosity analysis, followed by targeted promoter methylation and expression analysis to identify potential pathways in serrated adenomas. An initial panel of 9 sessile serrated adenomas (SSA) and one TSA were analysed using Illumina Goldengate HumanLinkage panel arrays to ascertain regions of loss of heterozygosity. This was verified via molecular inversion probe analysis and microsatellite analysis of a further 32 samples. Methylation analysis of genes of interest was carried out using methylation specific PCR (verified by pyrosequencing) and immunohistochemistry used to correlate loss of expression of genes of interest. All experiments used adenoma samples and normal tissue samples as control. SSA samples were found on whole-genome analysis to have consistent loss of heterozygosity at 4p15.1–4p15.31, which was not found in the sole TSA, adenomas, or normal tissues. Genes of interest in this region were PDCH7 and SLIT2, and combined MSP/IHC analysis of these genes revealed significant loss of SLIT2 expression associated with promoter methylation of SLIT2. Loss of expression of SLIT2 by promoter hypermethylation and loss of heterozygosity events is significantly associated with serrated adenoma development, and SLIT2 may represent a epimutated tumour suppressor gene according to the Knudson “two hit” hypothesis

VEGF-A, VEGF-C, and VEGF-D in Colorectal Cancer Progression

We aimed to assess the relationship of the angiogenic cytokines VEGF-A, VEGF-C, and VEGF-D and their receptors VEGFR-2 and VEGFR-3 in the adenoma-carcinoma sequence and in metastatic spread of colorectal cancer (CRC). mRNA expression levels were measured using semi-quantitative reverse transcription polymerase chain reaction in 70 CRC (35 with paired mucosae) and 20 adenomatous polyps. Immuohistochemistry and ELISA assessed protein expression. VEGF-D mRNA expression was significantly lower in both polyps and CRCs compared with normal mucosa (P=.0002 and .002, respectively), whereas VEGF-A and VEGF-C were significantly raised in CRCs (P=.006 and .004, respectively), but not polyps (P=.22 and P=.5, respectively). Receptor expression was similar in tumor tissue and normal mucosae. Tumors with lymph node metastases had significantly higher levels of VEGF-A compared with non-metastatic tumors (P=.043). There was no association between VEGF-C or VEGF-D and lymphatic spread. The decrease in VEGF-D occurring in polyps and carcinomas may allow the higher levels of VEGF-A and VEGF-C to bind more readily to the VEGF receptors, and produce the angiogenic switch required for tumor growth. Increased expression of VEGF-A within CRCs was associated with lymphatic metastases, and therefore, this member of the VEGF family may be the most important in determining metastatic spread

The rectosigmoid problem

The lack of consensus over the transition point for the end of the sigmoid and beginning of the rectum is a problem for the colorectal multidisciplinary team. In this review, we survey the wide number of landmarks for the rectosigmoid junction, and describe the theoretical and evidence-based strengths and weaknesses of each one. Without a reliable definition of the rectum, sigmoid and rectal cancers will be classified inconsistently. As the treatment strategies for sigmoid and rectal cancers are radically different, incorrect tumour localisation has a substantial impact on patient management, leading to under or over treatment. Inconsistent classification will confound investigation of metastatic patterns and treatment outcomes. Now that the rectosigmoid junction has been recognised as a distinct segment of colon by the International Classification of Diseases, further heterogeneity in management and outcomes could result to the detriment of patients and research. We describe a bespoke, anatomical and reliable landmark for the rectosigmoid junction; the sigmoid take-off