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Background: The immune response has important clinical value in colorectal cancer (CRC) in both prognosis and response to immunotherapy. This study aims to explore tumour immune cell infiltration in relation to clinically well-established molecular markers of CRC.

Methods: Multiplex immunohistochemistry and multispectral imaging was used to evaluate tumour infiltration of cytotoxic T cells (CD8+), Th1 cells (T-bet+), T regulatory cells (FoxP3+), B cells (CD20+), and macrophages (CD68+) in a cohort of 257 CRC patients.

Results: We found the expected association between higher immune-cell infiltration and microsatellite instability. Also, whereas BRAF-mutated tumours displayed increased immune-cell infiltration compared to BRAF wild-type tumours, the opposite was seen for KRAS-mutated tumours, differences that were most prominent for cytotoxic T cells and Th1 cells. The opposing relationships of BRAF and KRAS mutations with tumour infiltration of cytotoxic T cells was validated in an independent cohort of 608 CRC patients. A positive prognostic importance of cytotoxic T cells was found in wild-type as well as KRAS and BRAF-mutated CRCs in both cohorts.

Conclusion: A combined evaluation of MSI status, KRAS and BRAF mutational status, and immune infiltration (cytotoxic T cells) may provide important insights to prognosis and response to immunotherapy in CRC.

Background: Mounting evidence suggests a significant role of the gut microbiota in the development and progression of colorectal cancer (CRC). In particular, an over-representation of oral pathogens has been linked to CRC. The aim of this study was to further investigate the faecal microbial landscape of CRC patients, with a focus on the oral pathogens Parvimonas micra and Fusobacterium nucleatum.

Methods: In this study, 16S rRNA sequencing was conducted using faecal samples from CRC patients (n = 275) and controls without pathological findings (n = 95).

Results: We discovered a significant difference in microbial composition depending on tumour location and microsatellite instability (MSI) status, with P. micra, F. nucleatum, and Peptostreptococcus stomatis found to be more abundant in patients with MSI tumours. Moreover, P. micra and F. nucleatum were associated with a cluster of CRC-related bacteria including Bacteroides fragilis as well as with other oral pathogens such as P. stomatis and various Porphyromonas species. This cluster was distinctly different in the control group, suggesting its potential linkage with CRC.

Conclusions: Our results suggest a similar distribution of several CRC-associated bacteria within CRC patients, underscoring the importance of considering the concomitant presence of bacterial species in studies investigating the mechanisms of CRC development and progression.

Colorectal cancer is caused by a sequence of somatic genomic alterations affecting driver genes in core cancer pathways1. Here, to understand the functional and prognostic impact of cancer-causing somatic mutations, we analysed the whole genomes and transcriptomes of 1,063 primary colorectal cancers in a population-based cohort with long-term follow-up. From the 96 mutated driver genes, 9 were not previously implicated in colorectal cancer and 24 had not been linked to any cancer. Two distinct patterns of pathway co-mutations were observed, timing analyses identified nine early and three late driver gene mutations, and several signatures of colorectal-cancer-specific mutational processes were identified. Mutations in WNT, EGFR and TGFβ pathway genes, the mitochondrial CYB gene and 3 regulatory elements along with 21 copy-number variations and the COSMIC SBS44 signature correlated with survival. Gene expression classification yielded five prognostic subtypes with distinct molecular features, in part explained by underlying genomic alterations. Microsatellite-instable tumours divided into two classes with different levels of hypoxia and infiltration of immune and stromal cells. To our knowledge, this study constitutes the largest integrated genome and transcriptome analysis of colorectal cancer, and interlinks mutations, gene expression and patient outcomes. The identification of prognostic mutations and expression subtypes can guide future efforts to individualize colorectal cancer therapy.

Background and Objectives: Disparities between tumors arising via different sporadic carcinogenetic pathways have not been studied systematically. This retrospective multicenter cohort study evaluated the differences in the risk for non-colorectal malignancy between sporadic colorectal cancer (CRC) patients from different DNA mismatch repair status.

Methods: A retrospective European multicenter cohort study including in total of 1706 CRC patients treated between 1996 and 2019 in three different countries. The proficiency (pMMR) or deficiency (dMMR) of mismatch repair was determined by immunohistochemistry. Cases were analyzed for tumor BRAFV600E mutation, and BRAF mutated tumors were further analyzed for hypermethylation status in the promoter region of MLH1 to distinguish between sporadic and hereditary cases. Swedish and Finish patients were matched with their respective National Cancer Registries. For the Czech cohort, thorough scrutiny of medical files was performed to identify any non-colorectal malignancy within 20 years before or after the diagnosis of CRC. Poisson regression analysis was performed to identify the incidence rates of non-colorectal malignancies. For validation purposes, standardized incidence ratios were calculated for the Swedish cases adjusted for age, year, and sex.

Results: Of the 1706 CRC patients included in the analysis, 819 were female [48%], median age at surgery was 67 years [interquartile range: 60–75], and sporadic dMMR was found in 188 patients (11%). Patients with sporadic dMMR CRC had a higher incidence rate ratio (IRR) for non-colorectal malignancy before and after diagnosis compared to patients with a pMMR tumor, in both uni- (IRR = 2.49, 95% confidence interval [CI] = 1.89–3.31, p = 0.003) and multivariable analysis (IRR = 2.24, 95% CI = 1.67–3.01, p = 0.004). This association applied whether or not the non-colorectal tumor developed before or after the diagnosis of CRC in both uni- (IRR = 1.91, 95% CI = 1.28–2.98, p = 0.004), (IRR = 2.45, 95% CI = 1.72–3.49, p = 0.004) and multivariable analysis (IRR = 1.67,95% CI = 1.05–2.65, p = 0.029), (IRR = 2.35, 95% CI = 1.63–3.42, p = 0.005), respectively.

Conclusion: In this retrospective European multicenter cohort study, patients with sporadic dMMR CRC had a higher risk for non-colorectal malignancy than those with pMMR CRC. These findings indicate the need for further studies to establish the need for and design of surveillance strategies for patients with dMMR CRC.

The systemic inflammatory response (SIR), defined as elevated levels of circulating C-reactive protein (CRP), is an important predictor of impaired survival in colorectal cancer. The aim of this study was to explore the prognostic role of SIR and its association with tumour mismatch repair status and the immune response. Immune activity profiles of mononuclear cells isolated from CRC tissues and blood in the U-CAN exploration cohort (n = 69), were analysed by flow cytometry. In the U-CAN validation cohort (n = 257), T-helper cells (T-bet⁺), cytotoxic T cells (CD8⁺), regulatory T cells (FoxP3⁺), B cells (CD20⁺), and macrophages (CD68⁺) were analysed by multispectral imaging. Microsatellite instability was determined using five mononucleotide-repeat microsatellite markers. Patients with high CRP levels (> 10 mg/l) were significantly more often diagnosed with high-grade tumours and tumours exhibiting microsatellite instability. However, some patients with high CRP levels were found to have microsatellite-stable tumours. Furthermore, high CRP levels were associated with specific tumour immune traits including an augmented macrophage response and were significantly linked to poorer cancer-specific survival, particularly in patients with microsatellite-stable tumours. In conclusion, our findings suggest an interplay between SIR and mismatch repair status in CRC prognosis which needs to be further explored.

Microbiota dysbiosis may affect both the development and progression of colorectal cancer (CRC). Large metagenomic studies have highlighted specific oral bacteria linked to CRC including Porphyromonas gingivalis. Few studies have however analysed the implications of this bacterium in CRC progression and survival. In this study, we investigated the intestinal presence of P. gingivalis by qPCR in both faecal and mucosal samples from two different patient cohorts, including patients with precancerous dysplasia or CRC, as well as controls. P. gingivalis was detected in 2.6-5.3% of CRC patients and significantly different levels of P. gingivalis were found in faeces of CRC patients compared to controls (P = 0.028). Furthermore, an association was found between the presence of P. gingivalis in faeces and tumour tissue (P < 0.001). Our findings further suggested a potential link between mucosal P. gingivalis and tumours of MSI subtype (P = 0.040). Last but not least, patients with faecal P. gingivalis were found to have a significantly decreased cancer-specific survival (P = 0.040). In conclusion, P. gingivalis could be linked to patients with CRC and to a worse patient prognosis. Further studies are needed to elucidate the role of P. gingivalis in CRC pathogenesis.

The importance of the tumour microbiome in different aspects of colorectal cancer (CRC) has been increasingly recognised, but many questions remain. The aim of this study was to explore the effect of specific CRC associated microbes on the tumour immune response, which has a considerable prognostic value in CRC. We applied specific qPCR to detect Parvimonas micra and Fusobacterium nucleatum in tumour tissues from an immunologically well-characterised cohort of 69 CRC patients. This cohort included detailed analyses of immune profiles based on flow cytometry and transcriptomics in tumour tissue and blood, along with comprehensive analyses of molecular subtypes. P. micra and F. nucleatum were detected in 24% and 64% of tumour tissues, respectively. We found a significant association of P. micra with high-grade tumours and tumours of CMS1 subtype. F. nucleatum was significantly associated with right-sided tumours, microsatellite instability, and CMS1 tumours. The immunological analyses revealed significant associations of P. micra with activated CD69+ T lymphocytes and increased antigen-presenting HLA-DR+ B lymphocytes. P. micra was also positively associated with M1 and M2 macrophage traits. The impact of P. micra tumour colonisation on the immune response was further assessed using transcriptomics in validation of our findings. No associations were found between F. nucleatum and immune profiles in this study. Our findings support novel associations between P. micra and the immune response in CRC. A better understanding of these interactions might help to identify important predictive and prognostic tools as well as new targets for therapy.

Increasing evidence suggests that the gut microbiota may impact colorectal cancer (CRC) development and progression. In this study, the tumour colonisation of two CRC-associated bacteria, Parvimonas micra and Fusobacterium nucleatum, was studied in relation to patient survival in a cohort of 257 CRC patients. Colonisation of P. micra and F. nucleatum was analysed in fresh frozen tumour tissue (n = 112) and in faeces (n = 250) by qPCR. When analysing tumour tissues, both P. micra and F. nucleatum were found to be associated with decreased five-year cancer-specific survival, an association that remained significant in multivariable analysis for P. micra. Furthermore, we found significant associations of high levels of P. micra and F. nucleatum with tumour molecular characteristics, i.e., tumours mutated in BRAF^V600E, and tumours of the MSI subtype. The analysis of faecal samples showed weaker associations with prognosis and tumour molecular characteristics. In conclusion, our findings support a novel association of tumour colonisation of P. micra with decreased patient survival. A better understanding of the role of the gut microbiota in CRC might contribute to the advancement of prognostic tools and new targets for therapy.

Colorectal cancer (CRC) is a heterogeneous disease with different genetic and molecular backgrounds, leading to a diverse patient prognosis and treatment response. Four consensus molecular subtypes (CMS 1–4) have recently been proposed based on transcriptome profiling. A clinically practical immunohistochemistry (IHC) based CMS classifier consisting of the four markers FRMD6, ZEB1, HTR2B, and CDX2 was then demonstrated. However, the IHC-CMS classifier did not distinguish between CMS2 and CMS3 tumours. In this study, we have applied the proposed transcriptome based and IHC-based CMS classifiers in a CRC cohort of 65 patients and found a concordance of 77.5 %. Further, we modified the IHC-CMS classifier by analysing the differentially expressed genes between CMS2 and CMS3 tumours using RNA-sequencing data from the TCGA dataset. The result showed that WNT signalling was among the most upregulated pathways in CMS2 tumours, and the expression level of CTNNB1 (encoding β-catenin), a WNT pathway hallmark, was significantly upregulated (P = 1.15 × 10−6). We therefore introduced nuclear β-catenin staining to the IHC-CMS classifier. Using the modified classifier in our cohort, we found a 71.4 % concordance between the IHC and RNA-sequencing based CMS classifiers. Moreover, β-catenin staining could classify 16 out of the 19 CMS2/3 tumours into CMS2 or CMS3, thereby showing an 84.2 % concordance with the RNA-sequencing-based classifier. In conclusion, we evaluated CMS classifiers based on transcriptome and IHC analysis. We present a modified IHC panel that categorizes CRC tumours into the four CMS groups. To our knowledge, this is the first study using IHC to identify all four CMS groups.

Background: The effect of the genetic imprint on the emergency presentation of colon cancer remains unclear. The disparity between tumours evolving along different carcinogenetic pathways has not been studied systematically. This retrospective multicenter cohort study evaluates the association between mismatch repair status and the risk for acute surgery of colon cancer.

Patients and methods: A retrospective multicenter cohort study including in total 870 patients from three different countries. Scandinavian cohort (Finland and Sweden), including a total of 412 patients operated between January 1, 1995 and December 31, 2010, was validated against a cohort from the Czech Republic, including a total of 458 patients, operated between January 1, 2018 and December 31, 2019. The proficiency or deficiency of mismatch repair was determined by immunohistochemistry. Primary outcome was the risk for acute colon cancer surgery given as the Odds Ratio (OR) in the univariable and multivariable analyses. Acute colon cancer surgery was defined as surgery performed during the same hospital admission as when the diagnosis of colon cancer was made.

Results: Of the 870 patients (399 females [46%]) included in the analyses, median age at surgery was 69 [interquartile range, 61–76] years, deficient Mismatch Repair (dMMR) status was found in 190 patients (22%), and 179 patients (21%) underwent acute surgery during the same hospital admission as when the diagnosis of colon cancer was made. In the Scandinavian cohort, a significant association between dMMR status and acute surgery was seen in both the univariable (OR 1.82, 95% CI 1.11–3.02, P = 0.017) and the multivariable (OR = 2.21, 95% CI 1.28–3.95, P = 0.005) analyses. This was confirmed in the Czech validation cohort in both the univariable (OR = 1.94, 95% CI 1.09–3.26, P = 0.022) and the multivariable (OR = 1.77, 95% CI 1.15–3.18, P = 0.021) analyses.

Conclusion: This multicenter study reveals a strong association between acute colon cancer surgery and dMMR tumour status.