Does the Microbiota Composition Influence the Efficacy of Colorectal Cancer Immunotherapy?

The power of microbes: the key role of gut microbiota in the initiation and progression of colorectal cancer

Colorectal cancer (CRC) is ranked as the third most prevalent malignancy and is a leading cause of cancer-related mortality globally, significantly affecting the health and longevity of middle-aged individuals and the elderly. The primary risk factors for CRC are mainly due to unhealthy dietary habits and lifestyle choices, and they have been shown to profoundly influence the composition of the gut microbiota. Given that dietary patterns are critical determinants of gut microbial diversity, a compelling association exists between gut microbiota and the pathogenesis of CRC. Recent research has increasingly focused on the intricate interplay between gut microbiota and CRC, exploring its role in disease initiation, progression, and the modulation of host immune responses. Investigations have demonstrated that certain specific microbial communities can promote inflammation, disrupt metabolic pathways, and produce carcinogenic compounds, thereby contributing to the development of CRC. Conversely, a diverse and balanced gut microbiome may confer protective effects against cancer through mechanisms such as the production of short-chain fatty acids and the enhancement of intestinal barrier integrity. This article provides a comprehensive overview of the characteristics of the gut microbial community and its complex relationship with CRC. It highlights potential mechanisms through which gut microbiota may influence CRC pathogenesis, including chronic inflammation, toxins, metabolites, epigenetic dysregulation, and immune regulatory dysfunction. Additionally, this review summarizes innovative strategies for CRC prevention and treatment, emphasizing the therapeutic potential of probiotics and natural plant extracts. By elucidating these connections, this work aims to enhance the understanding of the gut microbiome's role in CRC.

Clinicopathological, molecular, and prognostic features of colorectal carcinomas with KRAS c.34G>T (p.G12C) mutation

Evidence indicates that combinations of anti-EGFR antibodies and KRAS p.G12C (c.34G>T) inhibitors can be an effective treatment strategy for advanced colorectal cancer. We hypothesized that KRAS c.34G>T (p.G12C)-mutated colorectal carcinoma might be a distinct tumor subtype. We utilized a prospective cohort incident tumor biobank (including 1347 colorectal carcinomas) and detected KRAS c.34G>T (p.G12C) mutation in 43 cases (3.2%) and other KRAS mutations (in codon 12, 13, 61, or 146) in 467 cases (35%). The CpG island methylator phenotype (CIMP)-low prevalence was similarly higher in KRAS c.34G>T mutants (52%) and other KRAS mutants (49%) than in KRAS-wild-type tumors (31%). KRAS c.34G>T mutants showed higher CIMP-high prevalence (14%) and lower CIMP-negative prevalence (33%) compared with other KRAS mutants (6% and 45%, respectively; p = 0.0036). Similar to other KRAS mutants, KRAS c.34G>T-mutated tumors were associated with cecal location, non-microsatellite instability (MSI)-high status, BRAF wild type, and PIK3CA mutation when compared with KRAS-wild-type tumors. Compared with BRAF-mutated tumors, KRAS c.34G>T mutants showed more frequent LINE-1 hypomethylation, a biomarker for early-onset colorectal carcinoma. KRAS c.34G>T mutants were not associated with other features, including the tumor tissue abundance of Fusobacterium nucleatum (F. animalis), pks+ Escherichia coli, Bifidobacterium, or (enterotoxigenic) Bacteroides fragilis. Among 1122 BRAF-wild-type colorectal carcinomas, compared with KRAS-wild-type tumors, multivariable-adjusted colorectal cancer-specific mortality hazard ratios (95% confidence interval) were 1.82 (1.05-3.17) in KRAS c.34G>T (p.G12C)-mutated tumors (p = 0.035) and 1.57 (1.22-2.02) in other KRAS-mutated tumors (p = 0.0004). Our study provides novel evidence for clinical and tumor characteristics of KRAS c.34G>T (p.G12C)-mutated colorectal carcinoma.

Exploring the Role of the Gut Microbiota in Modulating Colorectal Cancer Immunity

The gut microbiota plays an essential role in maintaining immune homeostasis and influencing the immune landscape within the tumor microenvironment. This review aims to elucidate the interactions between gut microbiota and tumor immune dynamics, with a focus on colorectal cancer (CRC). The review spans foundational concepts of immuno-microbial interplay, factors influencing microbiome composition, and evidence linking gut microbiota to cancer immunotherapy outcomes. Gut microbiota modulates anti-cancer immunity through several mechanisms, including enhancement of immune surveillance and modulation of inflammatory responses. Specific microbial species and their metabolic byproducts can significantly influence the efficacy of cancer immunotherapies. Furthermore, microbial diversity within the gut microbiota correlates with clinical outcomes in CRC, suggesting potential as a valuable biomarker for predicting response to immunotherapy. Conclusions: Understanding the relationship between gut microbiota and tumor immune responses offers potential for novel therapeutic strategies and biomarker development. The gut microbiota not only influences the natural history and treatment response of CRC but also serves as a critical modulator of immune homeostasis and anti-cancer activity. Further exploration into the microbiome's role could enhance the effectiveness of existing treatments and guide the development of new therapeutic modalities.

How do tumours outside the gastrointestinal tract respond to dietary fibre supplementation?

Cancer remains one of the leading causes of death worldwide, despite advances in treatments such as surgery, chemotherapy, radiotherapy and immunotherapy. The role of the gut microbiota in human health and disease, particularly in relation to cancer incidence and treatment response, has gained increasing attention. Emerging evidence suggests that dietary fibre, including prebiotics, can modulate the gut microbiota and influence antitumour effects. In this review, we provide an overview of how dietary fibre impacts the gut-tumour axis through immune and non-immune mechanisms. Preclinical evidence shows that β-glucan or inulin effectively suppress extraintestinal tumour growth via immunomodulation. Other fibres such as resistant starch, modified citrus pectin and rye bran may confer antitumour effects through metabolic regulation, production of metabolites or downregulation of the insulin/insulin-like growth factor 1 axis. Additionally, we highlight the potential for dietary fibre to modify the response to immunotherapy, chemotherapy and radiotherapy, as shown by inulin increasing the abundance of beneficial gut bacteria, such as Bifidobacterium, Akkermansia, Lactobacillus and Faecalibacterium prausnitzii, which have been associated with enhanced immunotherapy outcomes, particularly in melanoma-bearing mice. Furthermore, certain types of dietary fibre, such as psyllium, partially hydrolysed guar gum, hydrolysed rice bran and inulin plus fructooligosaccharide, have been shown to mitigate gastrointestinal toxicities in patients with cancer undergoing pelvic radiotherapy. Despite the proven benefits, it is noteworthy that most adults do not consume enough dietary fibre, underscoring the importance of promoting dietary fibre supplementation in patients with cancer to optimise their treatment responses.

How the interplay among the tumor microenvironment and the gut microbiota influences the stemness of colorectal cancer cells

Colorectal cancer (CRC) remains the third most prevalent cancer disease and involves a multi-step process in which intestinal cells acquire malignant characteristics. It is well established that the appearance of distal metastasis in CRC patients is the cause of a poor prognosis and treatment failure. Nevertheless, in the last decades, CRC aggressiveness and progression have been attributed to a specific cell population called CRC stem cells (CCSC) with features like tumor initiation capacity, self-renewal capacity, and acquired multidrug resistance. Emerging data highlight the concept of this cell subtype as a plastic entity that has a dynamic status and can be originated from different types of cells through genetic and epigenetic changes. These alterations are modulated by complex and dynamic crosstalk with environmental factors by paracrine signaling. It is known that in the tumor niche, different cell types, structures, and biomolecules coexist and interact with cancer cells favoring cancer growth and development. Together, these components constitute the tumor microenvironment (TME). Most recently, researchers have also deepened the influence of the complex variety of microorganisms that inhabit the intestinal mucosa, collectively known as gut microbiota, on CRC. Both TME and microorganisms participate in inflammatory processes that can drive the initiation and evolution of CRC. Since in the last decade, crucial advances have been made concerning to the synergistic interaction among the TME and gut microorganisms that condition the identity of CCSC, the data exposed in this review could provide valuable insights into the biology of CRC and the development of new targeted therapies.

Prognostic role of detailed colorectal location and tumor molecular features: analyses of 13,101 colorectal cancer patients including 2994 early-onset cases

BACKGROUND

The pathogenic effect of colorectal tumor molecular features may be influenced by several factors, including those related to microbiota, inflammation, metabolism, and epigenetics, which may change along colorectal segments. We hypothesized that the prognostic association of colon cancer location might differ by tumor molecular characteristics.

METHODS

Utilizing a consortium dataset of 13,101 colorectal cancer cases, including 2994 early-onset cases, we conducted survival analyses of detailed tumor location stratified by statuses of microsatellite instability (MSI), CpG island methylator phenotype (CIMP), and KRAS and BRAF oncogenic mutation.

RESULTS

There was a statistically significant trend for better colon cancer-specific survival in relation to tumor location from the cecum to sigmoid colon (Ptrend = 0.002), excluding the rectum. The prognostic association of colon location differed by MSI status (Pinteraction = 0.001). Non-MSI-high tumors exhibited the cecum-to-sigmoid trend for better colon cancer-specific survival [Ptrend < 0.001; multivariable hazard ratio (HR) for the sigmoid colon (vs. cecum), 0.80; 95% confidence interval (CI) 0.70-0.92], whereas MSI-high tumors demonstrated a suggestive cecum-to-sigmoid trend for worse survival (Ptrend = 0.020; the corresponding HR, 2.13; 95% CI 1.15-3.92). The prognostic association of colon tumor location also differed by CIMP status (Pinteraction = 0.003) but not significantly by age, stage, or other features. Furthermore, MSI-high status was a favorable prognostic indicator in all stages.

CONCLUSIONS

Both detailed colonic location and tumor molecular features need to be accounted for colon cancer prognostication to advance precision medicine. Our study indicates the important role of large-scale studies to robustly examine detailed colonic subsites in molecular oncology research.

Is red blood cell distribution width a prognostic factor for colorectal cancer? A meta-analysis

Background

RDW might be an easy and cost-effective pre-operative prognostic factor for cancer patients. The aim of the current study was to analyze whether red blood cell distribution width (RDW) was a prognostic factor for colorectal cancer (CRC) patients who underwent radical surgery.

Methods

We conducted the searching strategy in three databases including the PubMed, Embase and Cochrane Library from the inception to May 07, 2022, to find eligible studies. In this meta-analysis, we focused on the prognosis. Pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for overall survival (OS), disease-free survival (DFS) and cancer-specific survival (CSS).

Results

A total of seven studies involving 7,541 patients were included in this meta-analysis. After pooling up the HRs, red blood cell distribution width-coefficient of variation (RDW-CV) was not an independent prognostic factor of OS (HR = 1.48, I²= 90%, 95% CI = 0.93 to 2.36, P = 0.10), however, red blood cell distribution width-standard deviation (RDW-SD) was an independent prognostic factor of OS (HR = 1.99, I²= 0%, 95% CI = 1.59 to 2.49, P < 0.01). As for DFS, we found that RDW-CV (HR = 1.51, I²= 83%, 95% CI = 0.94 to 2.43, P = 0.09 < 0.10) and RDW-SD (HR = 1.77, I²= 56%, 95% CI = 0.91 to 3.43, P = 0.09 < 0.10) were both the independent prognostic factors. In terms of CSS, we found that RDW-CV was not an independent prognostic factor (HR = 1.23, I²= 95%, 95% CI = 0.72 to 2.10, P = 0.46).

Conclusion

RDW-SD was an independent prognostic factor of OS and DFS, and RDW-CV was an independent prognostic factor of DFS.