Stem cell dynamics and pretumor progression in the intestinal tract

Colorectal carcinogenesis is a process that follows a stepwise cascade that goes from the normal to an invisible pretumor stage ultimately leading to grossly visible tumor progression. During pretumor progression, an increasing accumulation of genetic alterations occurs, by definition without visible manifestations. It is generally thought that stem cells in the crypt base are responsible for this initiation of colorectal cancer progression because they are the origin of the differentiated epithelial cells that occupy the crypt. Furthermore, they are characterized by a long life span that enables them to acquire these cumulative mutations. Recent studies visualized the dynamics of stem cells both in vitro and in vivo. Translating this work into clinical applications will contribute to the evaluation of patients’ predisposition for colorectal carcinogenesis and may help in the design of preventive measures for high-risk groups. In this review, we outline the progress made in the research into tracing stem cell dynamics. Further, we highlight the importance and potential clinical value of tracing stem cell dynamics in pretumor progression

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility.

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings

Stem cell dynamics and pretumor progression in the intestinal tract

Colorectal carcinogenesis is a process that follows a stepwise cascade that goes from the normal to an invisible pretumor stage ultimately leading to grossly visible tumor progression. During pretumor progression, an increasing accumulation of genetic alterations occurs, by definition without visible manifestations. It is generally thought that stem cells in the crypt base are responsible for this initiation of colorectal cancer progression because they are the origin of the differentiated epithelial cells that occupy the crypt. Furthermore, they are characterized by a long life span that enables them to acquire these cumulative mutations. Recent studies visualized the dynamics of stem cells both in vitro and in vivo. Translating this work into clinical applications will contribute to the evaluation of patients’ predisposition for colorectal carcinogenesis and may help in the design of preventive measures for high-risk groups. In this review, we outline the progress made in the research into tracing stem cell dynamics. Further, we highlight the importance and potential clinical value of tracing stem cell dynamics in pretumor progression

Stem cell dynamics and pretumor progression in the intestinal tract

Colorectal carcinogenesis is a process that follows a stepwise cascade that goes from the normal to an invisible pretumor stage ultimately leading to grossly visible tumor progression. During pretumor progression, an increasing accumulation of genetic alterations occurs, by definition without visible manifestations. It is generally thought that stem cells in the crypt base are responsible for this initiation of colorectal cancer progression because they are the origin of the differentiated epithelial cells that occupy the crypt. Furthermore, they are characterized by a long life span that enables them to acquire these cumulative mutations. Recent studies visualized the dynamics of stem cells both in vitro and in vivo. Translating this work into clinical applications will contribute to the evaluation of patients’ predisposition for colorectal carcinogenesis and may help in the design of preventive measures for high-risk groups. In this review, we outline the progress made in the research into tracing stem cell dynamics. Further, we highlight the importance and potential clinical value of tracing stem cell dynamics in pretumor progression

Intestinal renin-angiotensin system is stimulated after deletion of Lkb1

Background and aims: LKB1 is a serine-threonine kinase, mutation of which can lead to the development of multiple benign intestinal hamartomas (Peutz–Jeghers syndrome). In this study, the authors investigate the mechanisms underlying this phenotype by exploring the transcriptional changes associated with Lkb1 deletion in intestinal epithelium. Methods: The authors used mice with Lkb1 deleted in the intestinal epithelium using a Cyp1a1-specific inducible Cre recombinase and used Affymetrix (Santa Clara, California, USA) microarray analysis to examine the transcriptional changes occurring immediately after Lkb1 loss. The authors also generated crypt–villus organoid culture to analyse Lkb1 role in intestinal responses to exogenous stimuli. Results: Affymetrix analysis identified the most significant change to be in Ren1 expression, a gene encoding a protease involved in angiotensinogen processing. Lkb1 deletion also enhanced ACE expression and subsequently angiotensin II (AngII) production in the mouse intestine. Intestinal apoptosis induced by Lkb1 deficiency was suppressed by ACE inhibitor captopril. Lkb1-deficient intestinal epithelium showed dynamic changes in AngII receptor type 1, suggesting a possible compensatory response to elevated AngII levels. A similar reduction in epithelial AngII receptor type 1 was also observed in human Peutz–Jeghers syndrome tumours contrasting with high expression of the receptor in the tumour stroma. Mechanistically, the authors showed two pieces of data that position Lkb1 in renin expression regulation, and they implied the importance of Lkb1 in linking cell responses with nutrient levels. First, the authors showed that Lkb1 deletion in isolated epithelial organoid culture resulted in renin upregulation only when the organoids were challenged with external cues such as AngII; second, that renin upregulation was dependent upon the MEK/ERK pathway in a circadian fashion and corresponded to active feeding time when nutrient levels were high. Conclusions: Taken together, these data reveal a novel role for Lkb1 in regulation of the gastrointestinal renin–angiotensin system

Practical and robust identification of molecular subtypes in colorectal cancer by immunohistochemistry

URPOSE: Recent transcriptomic analyses have identified four distinct molecular subtypes of colorectal cancer (CRC) with evident clinical relevance. However, the requirement for sufficient quantities of bulk tumor and difficulties in obtaining high quality genome-wide transcriptome data from formalin-fixed paraffin-embedded tissue are obstacles towards widespread adoption of this taxonomy. Here, we develop an immunohistochemistry-based classifier to validate the prognostic and predictive value of molecular CRC subtyping in a multi-center study. EXPERIMENTAL DESIGN: Tissue microarrays from 1076 CRC patients from four different cohorts were stained for five markers (CDX2, FRMD6, HTR2B, ZEB1 and KER) by immunohistochemistry and assessed for microsatellite instability. An automated classification system was trained on one cohort using quantitative image analysis or semi-quantitative pathologist scoring of the cores as input, and applied to three independent clinical cohorts. RESULTS: This classifier demonstrated 87% concordance with the gold-standard transcriptome-based classification. Application to three validation datasets confirmed the poor prognosis of the mesenchymal-like molecular CRC subtype. In addition, retrospective analysis demonstrated the benefit of adding cetuximab to bevacizumab and chemotherapy in patients with RAS wild type metastatic cancers of the canonical epithelial-like subtypes. CONCLUSION: This study shows that a practical and robust immunohistochemical-assay can be employed to identify molecular CRC subtypes and uncover subtype-specific therapeutic benefit. Finally, the described tool is available online for rapid classification of CRC samples, both in the format of an automated image analysis pipeline to score tumour core staining, and as a classifier based on semi-quantitative pathology scoring

Practical and robust identification of molecular subtypes in colorectal cancer by immunohistochemistry

URPOSE: Recent transcriptomic analyses have identified four distinct molecular subtypes of colorectal cancer (CRC) with evident clinical relevance. However, the requirement for sufficient quantities of bulk tumor and difficulties in obtaining high quality genome-wide transcriptome data from formalin-fixed paraffin-embedded tissue are obstacles towards widespread adoption of this taxonomy. Here, we develop an immunohistochemistry-based classifier to validate the prognostic and predictive value of molecular CRC subtyping in a multi-center study. EXPERIMENTAL DESIGN: Tissue microarrays from 1076 CRC patients from four different cohorts were stained for five markers (CDX2, FRMD6, HTR2B, ZEB1 and KER) by immunohistochemistry and assessed for microsatellite instability. An automated classification system was trained on one cohort using quantitative image analysis or semi-quantitative pathologist scoring of the cores as input, and applied to three independent clinical cohorts. RESULTS: This classifier demonstrated 87% concordance with the gold-standard transcriptome-based classification. Application to three validation datasets confirmed the poor prognosis of the mesenchymal-like molecular CRC subtype. In addition, retrospective analysis demonstrated the benefit of adding cetuximab to bevacizumab and chemotherapy in patients with RAS wild type metastatic cancers of the canonical epithelial-like subtypes. CONCLUSION: This study shows that a practical and robust immunohistochemical-assay can be employed to identify molecular CRC subtypes and uncover subtype-specific therapeutic benefit. Finally, the described tool is available online for rapid classification of CRC samples, both in the format of an automated image analysis pipeline to score tumour core staining, and as a classifier based on semi-quantitative pathology scoring