The immunogenicity of colorectal cancers with high-degree microsatellite instability

BACKGROUND: High-degree microsatellite instability (MSI-H) is a feature of approximately 15% of sporadic colorectal cancers. Patients with MSI-H cancers have been reported to have a better prognosis than those with non-MSI-H cancers. The MSI-H subset is also characterised by a dense infiltrate of intra-epithelial lymphocytes and the hypothesis that the latter represents an efficacious immune response contributing to improved outcome is very attractive. METHODS: Data for this review were identified by searches of MEDLINE, PubMed, and cross references from relevant articles using the search terms 'microsatellite instability', 'colorectal cancer' and 'immunology', 'immune response' or 'immunogenicity'. RESULTS: A total of 38 articles were identified by the search criteria and a further 95 articles by cross-referencing. The relevance of the articles to be interviewed was established by hand searching. Out of a total of 133 articles identified, 47 articles were rejected due to lack of relevance. A total of 86 articles were included in the review, pertaining to microsatellite instability in colorectal cancer, and immune mechanisms in colorectal cancer. CONCLUSION: It is suggested that this distinct group of colorectal cancers may have inherent immunogenic properties and that further elucidation of these may be invaluable to the development of successful immunotherapy

Novel approach to defining major abdominal surgery

Introduction: Over 5.8 million abdominal operations and procedures were recorded in England between April 2021 and March 20221. Although a definition of major surgery has been proposed by the Delphi consensus among European Surgical Association members2, there is no clear consensus regarding which surgical procedures constitute major abdominal surgery (MAS). Despite this, multiple sources in the literature, including perioperative morbidity and mortality scoring systems, national audits, and private healthcare coding schedules3–5, have alluded to this type of surgery without any underlying qualification. To clarify this area, a scoping literature review was conducted to derive a definition of MAS, based on content analysis of the terminology used to describe major abdominal surgical procedures6. MAS was defined as an intraperitoneal operation with no primary involvement of the thorax, involving either luminal resection and/or resection of a solid organ associated with the gastrointestinal tract. The aim of the current study was to verify the discriminative ability of this hypothesized definition of MAS using real-world data analysis and unsupervised machine learning

Colorectal cancers with microsatellite instability display mRNA expression signatures characteristic of increased immunogenicity

BACKGROUND: Colorectal cancers displaying high-degree microsatellite instability (MSI-H) have an improved prognosis compared to microsatellite stable (MSS) cancers. The observation of pronounced lymphocytic infiltrates suggests that MSI-H cancers are inherently more immunogenic. We aimed to compare the gene expression profiles of MSI-H and MSS cancers to provide evidence for an activated immune response in the former. RESULTS: We analysed tissue from 133 colorectal cancer patients with full consent and Local Ethics Committee approval. Genomic DNA was analysed for microsatellite instability in BAT-26. High-quality RNA was used for microarray analysis on the Affymetrix(® )HG-U133A chip. Data was analysed on GeneSpring software version 6.0. Confirmatory real-time RT-PCR was performed on 28 MSI-H and 26 MSS cancers. A comparison of 29 MSI-H and 104 MSS cancers identified 2070 genes that were differentially expressed between the two groups [P < 0.005]. Significantly, many key immunomodulatory genes were up-regulated in MSI-H cancers. These included antigen chaperone molecules (HSP-70, HSP-110, Calreticulin, gp96), pro-inflammatory cytokines (Interleukin (IL)-18, IL-15, IL-8, IL-24, IL-7) and cytotoxic mediators (Granulysin, Granzyme A). Quantitative RT-PCR confirmed up-regulation of HSP-70 [P = 0.016], HSP-110 [P = 0.002], IL-18 [P = 0.004], IL-8 [0.002] and Granulysin [P < 0.0001]. CONCLUSIONS: The upregulation of a large number of genes implicated in immune response supports the theory that MSI-H cancers are immunogenic. The novel observation of Heat Shock Protein up-regulation in MSI-H cancer is highly significant in light of the recognised roles of these proteins in innate and antigen-specific immunogenicity. Increased mRNA levels of pro-inflammatory cytokines and cytotoxic mediators also indicate an activated anti-tumour immune response