Associations of Pathogenic Variants in MLH1, MSH2, and MSH6 With Risk of Colorectal Adenomas and Tumors and With Somatic Mutations in Patients With Lynch Syndrome

Gastrointestinal Cancer Precursor Conditions and Their Detection

Gastrointestinal cancers are a leading cause of cancer morbidity and mortality. Many gastrointestinal cancers develop from cancer precursor lesions, which are commonly found in individuals with hereditary cancer syndromes. Hereditary cancer syndromes have advanced our understanding of cancer development and progression and have facilitated the evaluation of cancer prevention and interception efforts. Common gastrointestinal hereditary cancer syndromes, including their organ-specific cancer risk and surveillance recommendations, are reviewed in this article. The management of common gastroesophageal, pancreatic, and colonic precursor lesions is also discussed, regardless of their genetic background. Further research is needed to advance chemoprevention and immunoprevention strategies.

Colorectal cancer and advanced adenoma characteristics according to causative mismatch repair gene variant in Japanese colorectal surveillance for Lynch syndrome

BACKGROUND

The optimal interval of colonoscopy (CS) surveillance in cases with Lynch syndrome (LS), and stratification according to the causative mismatch repair gene mutation, has received much attention. To verify a feasible and effective CS surveillance strategy, we investigated the colorectal cancer (CRC) incidence at different intervals and the characteristics of precancerous colorectal lesions of LS cases.

METHODS

This retrospective multicenter study was conducted in Japan. CRCs and advanced adenomas (AAs) in 316 LS cases with germline pathogenic variants (path_) were analyzed according to the data of 1,756 registered CS.

RESULTS

The mean time interval for advanced CRCs (ACs) detected via CS surveillance was 28.7 months (95% confidence interval: 13.8-43.5). The rate of AC detection within (2.1%) and beyond 2 years (8.7%) differed significantly (p = 0.0003). AAs accounted for 43%, 46%, and 41% of lesions < 10 mm in size in the MLH1-, MSH2-, and MSH6-groups, respectively. The lifetime incidence of metachronous CRCs requiring intestinal resection for path_MLH1, path_MSH2, and path_MSH6 cases was 34%, 23%, and 14% in these cases, respectively. The cumulative CRC incidence showed a trend towards a 10-year delay for path_MSH6 cases as compared with that for path_MLH1 and path_MSH2 cases.

CONCLUSIONS

In cases with path_MLH1, path_MSH2, and path_MSH6, maintaining an appropriate CS surveillance interval of within 2 years is advisable to detect of the colorectal lesion amenable to endoscopic treatment. path_MSH6 cases could be stratified with path_MLH1 and MSH2 cases in terms of risk of metachronous CRC and age of onset.

Colonoscopic surveillance in Lynch syndrome: guidelines in perspective

Lynch syndrome predisposes to a high risk of colorectal cancer and colonoscopy remains the primary preventive strategy. The prevention of colorectal cancer through colonoscopy relies on identifying and removing adenomas, the main precursor lesion. Nevertheless, colonoscopy is not an optimal strategy since post-colonoscopy colorectal cancer remains an important issue. In continuation of a 2021 journal review, the present article seeks to offer an updated perspective by examining relevant articles from the past 3 years. We place recent findings in the context of existing guidelines, with a specific focus on colonoscopy surveillance. Key aspects explored include colonoscopy quality standards, timing of initiation, and surveillance intervals. Our review provides a comprehensive analysis of adenoma-related insights in Lynch syndrome, delving into emerging technologies like virtual chromoendoscopy and artificial intelligence-assisted endoscopy. This review aims to contribute valuable insights into the topic of colonoscopy surveillance in Lynch syndrome.

The ubiquitin ligase UBR4 and the deubiquitylase USP5 modulate the stability of DNA mismatch repair protein MLH1

MLH1 plays a critical role in DNA mismatch repair and genome maintenance. MLH1 deficiency promotes cancer development and progression, but the mechanism underlying MLH1 regulation remains enigmatic. In this study, we demonstrate that MLH1 protein is degraded by the ubiquitin-proteasome system and have identified vital cis-elements and trans-factors involved in MLH1 turnover. We found that the region encompassing the amino acids 516-650 is crucial for MLH1 degradation. The mismatch repair protein PMS2 may shield MLH1 from degradation as it bind to the MLH1 segment key to its turnover. Furthermore, we have identified the E3 ubiquitin ligase UBR4 and the deubiquitylase USP5, which oppositely modulate MLH1 stability. In consistence, UBR4 or USP5 deficiency affects the cellular response to nucleotide analog 6-TG, supporting their roles in regulating mismatch repair. Our study has revealed important insights into the regulatory mechanisms underlying MLH1 proteolysis, critical to DNA mismatch repair related diseases.

Nfe2l2/NRF2 Deletion Attenuates Tumorigenesis and Increases Bacterial Diversity in a Mouse Model of Lynch Syndrome

Lynch syndrome (LS) is the most prevalent heritable form of colorectal cancer. Its early onset and high lifetime risk for colorectal cancer emphasize the necessity for effective chemoprevention. NFE2L2 (NRF2) is often considered a potential druggable target, and many chemopreventive compounds induce NRF2. However, although NRF2 counteracts oxidative stress, it is also overexpressed in colorectal cancer and may promote tumorigenesis. In this study, we evaluated the role of NRF2 in the prevention of LS-associated neoplasia. We found increased levels of NRF2 in intestinal epithelia of mice with intestinal epithelium-specific Msh2 deletion (MSH2ΔIEC) compared with C57BL/6 (wild-type) mice, as well as an increase in downstream NRF2 targets NAD(P)H dehydrogenase (quinone 1) and glutamate-cysteine ligase catalytic subunit. Likewise, NRF2 levels were increased in human MSH2-deficient LS tumors compared with healthy human controls. In silico analysis of a publicly accessible RNA sequencing LS dataset also found an increase in downstream NRF2 targets. Upon crossing MSH2ΔIEC with Nrf2null (MSH2ΔIECNrf2null) mice, we unexpectedly found reduced tumorigenesis in MSH2ΔIECNrf2null mice compared with MSH2ΔIEC mice after 40 weeks, which occurred despite an increase in oxidative damage in MSH2ΔIECNrf2null mice. The loss of NRF2 impaired proliferation as seen by Ki67 intestinal staining and in organoid cultures. This was accompanied by diminished WNT/β-catenin signaling, but apoptosis was unaffected. Microbial α-diversity increased over time with the loss of NRF2 based upon 16S rRNA gene amplicon sequencing of murine fecal samples. Altogether, we show that NRF2 protein levels are increased in MSH2 deficiency and associated neoplasia, but the loss of NRF2 attenuates tumorigenesis. Activation of NRF2 may not be a feasible strategy for chemoprevention in LS. Prevention Relevance: Patients with LS have an early onset and high lifetime risk for colorectal cancer. In this study, we show that NRF2 protein levels are increased in MSH2 deficiency and associated neoplasia, but the loss of NRF2 attenuates tumorigenesis. This suggests that NRF2 may not be a tumor suppressor in this specific context.

Quality of endoscopic surveillance of Lynch syndrome patients in a Swedish cohort

Background and study aims Risk factors for colorectal cancer (CRC) in Lynch syndrome (LS) include sex, age, smoking, high body mass index (BMI), surveillance interval length, and risk genotype. The Boston Bowel Preparation Scale (BBPS) produces a standardized bowel cleanliness rating. A low BBPS score might be a risk factor for missed early lesions. The aim of this study was to investigate the correlation between BBPS score and adenoma detection (with known risk factors for CRC) and surveillance interval with CRC detection in LS patients. Methods A retrospective cohort study including 366 LS patients with 1,887 colonoscopies under surveillance in Stockholm, Sweden from 1989 to 2021 was conducted. Associations were tested using linear and logistic regression. Results We found no association between BBPS score and number of adenomas detected. A low BBPS score was found to be associated with older age (regression coefficient (coeff) -0.015; 95% confidence interval [CI] -0.026 to -0.004; P = 0.007) and obesity (coeff = -0.48; 95% CI: -0.89 to -0.062; P = 0.024). A higher number of detected adenomas was associated with older age (coeff = 0.008; 95% CI 0.004 to 0.012; P < 0.001), male sex (coeff = 0.097; 95% CI 0.008 to 0.19; P = 0.033) and CRC (coeff = 0.28; 95% CI 0.061 to 0.50; P = 0.012). Surveillance interval length was not significant in CRC detection. Conclusions Bowel cleanliness was not associated with adenoma detection and was less likely achieved in patients who were older and had higher BMI. Adenoma detection was associated with older age and male sex. The results indicate the need for better adherence to guidelines and attention to older age groups, men, and patients with obesity.

Mismatch Repair (MMR) Gene Mutation Carriers Have Favorable Outcome in Colorectal and Endometrial Cancer: A Prospective Cohort Study

Germline (Lynch syndrome, LS) and somatic deficiencies of mismatch repair proteins (MMRd) are linked to colorectal and endometrial cancer; however, their prognostic impact in Asian populations remains unclear. This prospective cohort study aimed to determine the prevalence and outcome of germline and somatic MMRd in cancer patients suspected of LS. Patients with colorectal or endometrial cancer suspected of LS were enrolled and underwent gene sequencing for germline MMRd (gMMRd) and immunohistochemistry staining of MMR proteins in a subset of the pathological samples (pMMRd). Among the 451 enrolled patients, 36 patients were gMMRd (+). Compared with gMMRd (-) patients, the 10-year relapse-free survival in gMMRd (+) patients was significantly higher (100% vs. 77.9%; p = 0.006), whereas the 10-year overall survival was similar (100% vs. 90.9%; p = 0.12). Among the 102 gMMRd (-) patients with available pMMR status, 13.7% were pMMRd (+). The 5-year relapse-free survival was 62.9% in gMMRd (-) pMMRd (+) patients and 35.0% in gMMRd (-) pMMRd (-) patients, both lower than gMMRd (+) patients (100%; p < 0.001). This study showed that having LS confers a favorable outcome in colorectal and endometrial cancer patients and highlights the importance of germline genetic testing following the detection of somatic MMRd.

Emerge of colorectal cancer in Lynch syndrome despite colonoscopy surveillance: A challenge of hide and seek

Even with colonoscopy surveillance, Lynch syndromes (LS) carriers still develop colorectal cancer (CRC). The cumulative incidence of CRCs under colonoscopy surveillance varies depending on the affected mismatch repair (MMR) gene. However, the precise mechanisms driving these epidemiological patterns remain incompletely understood. In recent years, several potential mechanisms explaining the occurrence of CRCs during colonoscopy surveillance have been proposed in individuals with and without LS. These encompass biological factors like concealed/accelerated carcinogenesis through a bypassed adenoma stage and accelerated progression from adenomas. Alongside these, various colonoscopy-related factors may contribute to formation of CRCs under colonoscopy surveillance, like missed yet detectable (pre)cancerous lesions, detected yet incompletely removed (pre)cancerous lesions, and colonoscopy-induced carcinogenesis due to tumor cell reimplantation. In this comprehensive literature update, we reviewed these potential factors and evaluated their relevance to each MMR group in an attempt to raise further awareness and stimulate research regarding this conflicting phenomenon.

Mitotic abnormalities precede microsatellite instability in lynch syndrome-associated colorectal tumourigenesis

BACKGROUND

Lynch syndrome (LS) is one of the most common hereditary cancer syndromes worldwide. Dominantly inherited mutation in one of four DNA mismatch repair genes combined with somatic events leads to mismatch repair deficiency and microsatellite instability (MSI) in tumours. Due to a high lifetime risk of cancer, regular surveillance plays a key role in cancer prevention; yet the observation of frequent interval cancers points to insufficient cancer prevention by colonoscopy-based methods alone. This study aimed to identify precancerous functional changes in colonic mucosa that could facilitate the monitoring and prevention of cancer development in LS.

METHODS

The study material comprised colon biopsy specimens (n = 71) collected during colonoscopy examinations from LS carriers (tumour-free, or diagnosed with adenoma, or diagnosed with carcinoma) and a control group, which included sporadic cases without LS or neoplasia. The majority (80%) of LS carriers had an inherited genetic MLH1 mutation. The remaining 20% included MSH2 mutation carriers (13%) and MSH6 mutation carriers (7%). The transcriptomes were first analysed with RNA-sequencing and followed up with Gorilla Ontology analysis and Reactome Knowledgebase and Ingenuity Pathway Analyses to detect functional changes that might be associated with the initiation of the neoplastic process in LS individuals.

FINDINGS

With pathway and gene ontology analyses combined with measurement of mitotic perimeters from colonic mucosa and tumours, we found an increased tendency to chromosomal instability (CIN), already present in macroscopically normal LS mucosa. Our results suggest that CIN is an earlier aberration than MSI and may be the initial cancer driving aberration, whereas MSI accelerates tumour formation. Furthermore, our results suggest that MLH1 deficiency plays a significant role in the development of CIN.

INTERPRETATION

The results validate our previous findings from mice and highlight early mitotic abnormalities as an important contributor and precancerous marker of colorectal tumourigenesis in LS.

FUNDING

This work was supported by grants from the Jane and Aatos Erkko Foundation, the Academy of Finland (330606 and 331284), Cancer Foundation Finland sr, and the Sigrid Jusélius Foundation. Open access is funded by Helsinki University Library.

Surveillance of the small-bowel by capsule endoscopy in Lynch syndrome - A systematic review with meta-analysis

BACKGROUND & AIMS

The role of small-bowel (SB) cancer surveillance by capsule endoscopy (CE) in Lynch syndrome (LS) patients has been investigated in recent years, with contradicting results. This meta-analysis evaluates the diagnostic yield (DY) of CE as a screening tool in asymptomatic LS patients.

METHODS

A systematic literature search was performed for all studies reporting the results of SB cancer screening in patients with LS. The primary outcome was the evaluation of the DY of CE in this setting for consecutive screening rounds.

RESULTS

Five studies comprising 428 patients and CE 677 procedures were included for data extraction and statistical analysis. The estimated pooled DY for CE-identified pathological findings was 8% in the first screening round and 6% in the second. Limiting the analysis to histologically-confirmed pathological findings, the pooled DY of second-round screening dropped to 0%. The included studies showed a significantly different prevalence of pathogenic variants in mismatch repair (path_MMR) genes, which underlie different cumulative incidences of extracolonic cancers.

CONCLUSIONS

SB surveillance by CE with a 2-year interval in asymptomatic LS individuals does not appear to be an effective screening strategy. Confirmatory prospective studies in this context are needed, considering the different cumulative incidence of SB tumors according to underlying path_MMR defects.

Association between colorectal cancer, the frequency of Bacteroides fragilis, and the level of mismatch repair genes expression in the biopsy samples of Iranian patients

BACKGROUND

Deficient DNA mismatch repair (MMR) can cause microsatellite instability (MSI) and is more common in colorectal cancer (CRC) patients. Understanding the carcinogenic mechanism of bacteria and their impact on cancer cells is crucial. Bacteroides fragilis (B. fragilis) has been identified as a potential promoter of tumorigenesis through the alteration of signaling pathways. This study aims to assess the expression levels of msh2, msh6, mlh1, and the relative frequency of B. fragilis in biopsy samples from CRC patients.

MATERIALS AND METHODS

Based on the sequence of mlh1, msh2, and msh6 genes, B. fragilis specific 16srRNA and bacterial universal 16srRNA specific primers were selected, and the expression levels of the target genes were analyzed using the Real-Time PCR method.

RESULTS

Significant increases in the expression levels of mlh1, msh2, and msh6 genes were observed in the cancer group. Additionally, the expression of these MMR genes showed a significant elevation in samples positive for B. fragilis presence. The relative frequency of B. fragilis in the cancer group demonstrated a significant rise compared to the control group.

CONCLUSION

The findings suggest a potential correlation between the abundance of B. fragilis and alterations in the expression of MMR genes. Since these genes can play a role in modifying colon cancer, investigating microbial characteristics and gene expression changes in CRC could offer a viable solution for CRC diagnosis.

Lynch Syndrome: From Multidisciplinary Management to Precision Prevention

BACKGROUND AND AIMS

Lynch syndrome (LS) is currently one of the most prevalent hereditary cancer conditions, accounting for 3% of all colorectal cancers and for up to 15% of those with DNA mismatch repair (MMR) deficiency, and it was one of the first historically identified. The understanding of the molecular carcinogenesis of LS tumors has progressed significantly in recent years. We aim to review the most recent advances in LS research and explore genotype-based approaches in surveillance, personalized cancer prevention, and treatment strategies.

METHODS

PubMed was searched to identify relevant studies, conducted up to December 2023, investigating molecular carcinogenesis in LS, surveillance strategies, cancer prevention, and treatment in LS tumors.

RESULTS

Multigene panel sequencing is becoming the benchmark in the diagnosis of LS, allowing for the detection of a pathogenic constitutional variant in one of the MMR genes. Emerging data from randomized controlled trials suggest possible preventive roles of resistant starch and/or aspirin in LS. Vaccination with immunogenic frameshift peptides appears to be a promising approach for both the treatment and prevention of LS-associated cancers, as evidenced by pre-clinical and preliminary phase 1/2a studies.

CONCLUSIONS

Although robust diagnostic algorithms, including prompt testing of tumor tissue for MMR defects and referral for genetic counselling, currently exist for suspected LS in CRC patients, the indications for LS screening in cancer-free individuals still need to be refined and standardized. Investigation into additional genetic and non-genetic factors that may explain residual rates of interval cancers, even in properly screened populations, would allow for more tailored preventive strategies.

[The two-in-one hit model of the short-cut carcinogenesis of colorectal carcinomas in MLH1-associated Lynch syndrome]

In a recently published study a new genetic hypothesis was established that explained the existence of CTNNB1 mutations in Lynch syndrome-associated colorectal carcinomas (MLH1-LS-CRC). This hypothesis states that a mitotic recombination on chromosome 3p simultaneously leads to inactivation of the mismatch repair gene MLH1 and to the activation of CTNNB1. This explains the increased frequency of CTNNB1 mutations in MLH1-LS-CRC compared with other colon carcinomas. To test this hypothesis, various experiments were carried out that show that the first phase of recombination occurs in non-cancerous tissues, which favours the development of CTNNB1 mutations. This mechanism could explain the rapid tumour progression in MLH1-LS-CRC. The results highlight the importance of mitotic recombination in carcinogenesis and provide an insight into the genetic basis of colorectal carcinoma in the context of Lynch syndrome.

MTHFR C677T and A1298C polymorphism's effect on risk of colorectal cancer in Lynch syndrome

Lynch syndrome (LS) is characterised by an increased risk of developing colorectal cancer (CRC) and other extracolonic epithelial cancers. It is caused by pathogenic germline variants in DNA mismatch repair (MMR) genes or the EPCAM gene, leading to a less functional DNA MMR system. Individuals diagnosed with LS (LS individuals) have a 10-80% lifetime risk of developing cancer. However, there is considerable variability in the age of cancer onset, which cannot be attributed to the specific MMR gene or variant alone. It is speculated that multiple genetic and environmental factors contribute to this variability, including two single nucleotide polymorphisms (SNPs) in the methylenetetrahydrofolate reductase (MTHFR) gene: C677T (rs1801133) and A1298C (rs1801131). By decreasing MTHFR activity, these SNPs theoretically reduce the silencing of DNA repair genes and increase the availability of nucleotides for DNA synthesis and repair, thereby protecting against early-onset cancer in LS. We investigated the effect of these SNPs on LS disease expression in 2,723 LS individuals from Australia, Poland, Germany, Norway and Spain. The association between age at cancer onset and SNP genotype (risk of cancer) was estimated using Cox regression adjusted for gender, country and affected MMR gene. For A1298C (rs1801131), both the AC and CC genotypes were significantly associated with a reduced risk of developing CRC compared to the AA genotype, but no association was seen for C677T (rs1801133). However, an aggregated effect of protective alleles was seen when combining the alleles from the two SNPs, especially for LS individuals carrying 1 and 2 alleles. For individuals with germline pathogenic variants in MLH1, the CC genotype of A1298C was estimated to reduce the risk of CRC significantly by 39% (HR = 0.61, 95% CI 0.42, 0.89, p = 0.011), while for individuals with pathogenic germline MSH2 variants, the AC genotype (compared to AA) was estimated to reduce the risk of CRC by 26% (HR = 0.66, 95% CI 0.53, 0.83, p = 0.01). In comparison, no association was observed for C677T (rs1801133). In conclusion, our study suggests that combining the MMR gene information with the MTHFR genotype, including the aggregated effect of protective alleles, could be useful in developing an algorithm that estimates the risk of CRC in LS individuals.

Incidence and prevalence of advanced colorectal neoplasia in Lynch syndrome

BACKGROUND AND AIMS

Lynch syndrome (LS) is the most common hereditary cause of colorectal cancer (CRC) and endometrial cancer (EC). Although colonoscopy reduces CRC in LS, the protection is variable. We assessed the prevalence and incidence of neoplasia in LS during surveillance colonoscopy in the United States and factors associated with advanced neoplasia.

METHODS

Patients with LS undergoing ≥1 surveillance colonoscopy and with no personal history of invasive CRC or colorectal surgery were included. Prevalent and incident neoplasia was defined as occurring <6 months before and ≥6 months after germline diagnosis of LS, respectively. We assessed advanced adenoma (AA), CRC, and the impact of mismatch repair pathogenic variant (PV) and typical LS cancer history (personal history of EC and/or family history of EC/CRC) on outcome.

RESULTS

A total of 132 patients (inclusive of 112 undergoing prevalent and incident surveillance) were included. The median examination interval and duration of prevalent and incident surveillance was .88 and 1.06 years and 3.1 and 4.6 years, respectively. Prevalent and incident AA were detected in 10.7% and 6.1% and invasive CRC in 0% and 2.3% of patients. All incident CRC occurred in MSH2 and MLH1 PV carriers and only 1 (.7%) while under surveillance in our center. AAs were detected in both LS cancer history cohorts and represented in all PVs.

CONCLUSIONS

In a U.S. cohort of LS, advanced neoplasia rarely occurred over annual surveillance. CRC was diagnosed only in MSH2/MLH1 PV carriers. AAs occurred regardless of PV or LS cancer history. Prospective studies are warranted to confirm our findings.

Biology of Precancers and Opportunities for Cancer Interception: Lesson from Colorectal Cancer Susceptibility Syndromes

Hereditary gastrointestinal cancer is associated with molecular and neoplastic precursors which have revealed much about sporadic carcinogenesis. Therefore, an appreciation of constitutional and somatic events linked to these syndromes have provided a useful model for the development of risk models and preventative strategies. In this review, we focus of two of the best characterized syndromes, Lynch syndrome (LS) and familial adenomatous polyposis (FAP). Our understanding of the neoplasia-immune interaction in LS has contributed to the development of immune mediated therapies including cancer preventing vaccines and immunotherapy for cancer precursors. Chemoprevention in LS with aspirin and nonsteroidal anti-inflammatory drugs has also translated into clinical cancer, however the efficacy of such agents in FAP remains elusive when cancer is applied as an endpoint in trials rather than the use of 'indirect' endpoints such as polyp burden, and requires further elucidation of biological mechanisms in FAP. Finally, we review controversies in gastrointestinal surveillance for LS and FAP, including limitations and opportunities of upper and lower gastrointestinal endoscopy in the prevention and early detection of cancer.

Microsatellite Instability: A Review of Molecular Epidemiology and Implications for Immune Checkpoint Inhibitor Therapy

Microsatellite instability (MSI) is one of the most important molecular characteristics of a tumor, which occurs among various tumor types. In this review article, we examine the molecular characteristics of MSI tumors, both sporadic and Lynch-associated. We also overview the risks of developing hereditary forms of cancer and potential mechanisms of tumor development in patients with Lynch syndrome. Additionally, we summarize the results of major clinical studies on the efficacy of immune checkpoint inhibitors for MSI tumors and discuss the predictive role of MSI in the context of chemotherapy and checkpoint inhibitors. Finally, we briefly discuss some of the underlying mechanisms causing therapy resistance in patients treated with immune checkpoint inhibitors.

Mortality by age, gene and gender in carriers of pathogenic mismatch repair gene variants receiving surveillance for early cancer diagnosis and treatment: a report from the prospective Lynch syndrome database

Background

The Prospective Lynch Syndrome Database (PLSD) collates information on carriers of pathogenic or likely pathogenic MMR variants (path_MMR) who are receiving medical follow-up, including colonoscopy surveillance, which aims to the achieve early diagnosis and treatment of cancers. Here we use the most recent PLSD cohort that is larger and has wider geographical representation than previous versions, allowing us to present mortality as an outcome, and median ages at cancer diagnoses for the first time.

Methods

The PLSD is a prospective observational study without a control group that was designed in 2012 and updated up to October 2022. Data for 8500 carriers of path_MMR variants from 25 countries were included, providing 71,713 years of follow up. Cumulative cancer incidences at 65 years of age were combined with 10-year crude survival following cancer, to derive estimates of mortality up to 75 years of age by organ, gene, and gender.

Findings

Gynaecological cancers were more frequent than colorectal cancers in path_MSH2, path_MSH6 and path_PMS2 carriers [cumulative incidence: 53.3%, 49.6% and 23.3% at 75 years, respectively]. Endometrial, colon and ovarian cancer had low mortality [8%, 13% and 15%, respectively] and prostate cancers were frequent in male path_MSH2 carriers [cumulative incidence: 39.7% at 75 years]. Pancreatic, brain, biliary tract and ureter and kidney and urinary bladder cancers were associated with high mortality [83%, 66%, 58%, 27%, and 29%, respectively]. Among path_MMR carriers undergoing colonoscopy surveillance, particularly path_MSH2 carriers, more deaths followed non-colorectal Lynch syndrome cancers than colorectal cancers.

Interpretation

In path_MMR carriers undergoing colonoscopy surveillance, non-colorectal Lynch syndrome cancers were associated with more deaths than were colorectal cancers. Reducing deaths from non-colorectal cancers presents a key challenge in contemporary medical care in Lynch syndrome.

Funding

We acknowledge funding from the Norwegian Cancer Society, contract 194751-2017.

Germline Variants in MLH1 and ATM Genes in a Young Patient with MSI-H in a Precancerous Colonic Lesion

Lynch syndrome (LS) is an autosomal dominant inherited disorder that primarily predisposes individuals to colorectal and endometrial cancer. It is associated with pathogenic variants in DNA mismatch repair (MMR) genes. In this study, we report the case of a 16-year-old boy who developed a precancerous colonic lesion and had a clinical suspicion of LS. The proband was found to have a somatic MSI-H status. Analysis of the coding sequences and flanking introns of the MLH1 and MSH2 genes by Sanger sequencing led to the identification of the variant of uncertain significance, namely, c.589-9_589-6delGTTT in the MLH1 gene. Further investigation revealed that this variant was likely pathogenetic. Subsequent next-generation sequencing panel analysis revealed the presence of two variants of uncertain significance in the ATM gene. We conclude that the phenotype of our index case is likely the result of a synergistic effect of these identified variants. Future studies will allow us to understand how risk alleles in different colorectal-cancer-prone genes interact with each other to increase an individual's risk of developing cancer.

Genotype-Phenotype Correlations in Autosomal Dominant and Recessive APC Mutation-Negative Colorectal Adenomatous Polyposis

The most prevalent type of intestinal polyposis, colorectal adenomatous polyposis (CAP), is regarded as a precancerous lesion of colorectal cancer with obvious genetic characteristics. Early screening and intervention can significantly improve patients' survival and prognosis. The adenomatous polyposis coli (APC) mutation is believed to be the primary cause of CAP. There is, however, a subset of CAP with undetectable pathogenic mutations in APC, known as APC (-)/CAP. The genetic predisposition to APC (-)/CAP has largely been associated with germline mutations in some susceptible genes, including the human mutY homologue (MUTYH) gene and the Nth-like DNA glycosylase 1 (NTHL1) gene, and DNA mismatch repair (MMR) can cause autosomal recessive APC (-)/CAP. Furthermore, autosomal dominant APC (-)/CAP could occur as a result of DNA polymerase epsilon (POLE)/DNA polymerase delta 1 (POLD1), axis inhibition protein 2 (AXIN2), and dual oxidase 2 (DUOX2) mutations. The clinical phenotypes of these pathogenic mutations vary greatly depending on their genetic characteristics. Therefore, in this study, we present a comprehensive review of the association between autosomal recessive and dominant APC (-)/CAP genotypes and clinical phenotypes and conclude that APC (-)/CAP is a disease caused by multiple genes with different phenotypes and interaction exists in the pathogenic genes.

Lynch Syndrome Genetics and Clinical Implications

Lynch syndrome (LS) is one of the most prevalent hereditary cancer syndromes in humans and accounts for some 3% of unselected patients with colorectal or endometrial cancer and 10%-15% of those with DNA mismatch repair-deficient tumors. Previous studies have established the genetic basis of LS predisposition, but there have been significant advances recently in the understanding of the molecular pathogenesis of LS tumors, which has important implications in clinical management. At the same time, immunotherapy has revolutionized the treatment of advanced cancers with DNA mismatch repair defects. We aim to review the recent progress in the LS field and discuss how the accumulating epidemiologic, clinical, and molecular information has contributed to a more accurate and complete picture of LS, resulting in genotype- and immunologic subtype-specific strategies for surveillance, cancer prevention, and treatment.

Long-term benefit of immunotherapy in a patient with squamous lung cancer exhibiting mismatch repair deficient/high microsatellite instability/high tumor mutational burden: A case report and literature review

Genetic mutations that render mismatch repair defective may result in microsatellite instability, which is common in colorectal carcinomas and gastric cancers as well as Lynch syndrome. Mismatch repair deficiency/high microsatellite instability (dMMR/MSI-H) predicts the tumor response to immune checkpoint inhibitors. However, few studies have evaluated the efficacy of immune checkpoint inhibitors in non-small cell lung cancer (NSCLC) patients with dMMR/MSI-H. In this work, we present a patient with advanced squamous lung cancer with dMMR/MSI-H and a high tumor mutational burden (TMB-H) who obtained a long-term benefit from immunotherapy. NSCLC patients with dMMR/MSI-H/TMB-H may thus benefit from immune checkpoint inhibitors.

PMS2-associated Lynch syndrome: Past, present and future

Carriers of any pathogenic variant in one of the MMR genes (path_MMR carriers) were traditionally thought to be at comparable risk of developing a range of different malignancies, foremost colorectal cancer (CRC) and endometrial cancer. However, it is now widely accepted that their cancer risk and cancer spectrum range notably depending on which MMR gene is affected. Moreover, there is increasing evidence that the MMR gene affected also influences the molecular pathogenesis of Lynch syndrome CRC. Although substantial progress has been made over the past decade in understanding these differences, many questions remain unanswered, especially pertaining to path_PMS2 carriers. Recent findings show that, while the cancer risk is relatively low, PMS2-deficient CRCs tend to show more aggressive behaviour and have a worse prognosis than other MMR-deficient CRCs. This, together with lower intratumoral immune infiltration, suggests that PMS2-deficient CRCs might have more in common biologically with sporadic MMR-proficient CRCs than with other MMR-deficient CRCs. These findings could have important consequences for surveillance, chemoprevention and therapeutic strategies (e.g. vaccines). In this review we discuss the current knowledge, current (clinical) challenges and knowledge gaps that should be targeted by future studies.

Strong Hereditary Predispositions to Colorectal Cancer

Cancer is one of the most common causes of death worldwide. A strong predisposition to cancer is generally only observed in colorectal cancer (5% of cases) and breast cancer (2% of cases). Colorectal cancer is the most common cancer with a strong genetic predisposition, but it includes dozens of various syndromes. This group includes familial adenomatous polyposis, attenuated familial adenomatous polyposis, MUTYH-associated polyposis, NTHL1-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis syndrome, Cowden syndrome, Lynch syndrome, and Muir-Torre syndrome. The common symptom of all these diseases is a very high risk of colorectal cancer, but depending on the condition, their course is different in terms of age and range of cancer occurrence. The rate of cancer development is determined by its conditioning genes, too. Hereditary predispositions to cancer of the intestine are a group of symptoms of heterogeneous diseases, and their proper diagnosis is crucial for the appropriate management of patients and their successful treatment. Mutations of specific genes cause strong colorectal cancer predispositions. Identifying mutations of predisposing genes will support proper diagnosis and application of appropriate screening programs to avoid malignant neoplasm.

Lynch Syndrome: From Carcinogenesis to Prevention Interventions

Simple Summary

Promoting proper preventive interventions to reduce morbidity and mortality is one of the most important challenges pertaining to inherited conditions. Lynch syndrome (LS) is an inherited disorder that predisposes to several kinds of tumor and is responsible for a relevant proportion of human colorectal and endometrial cancers. Recent knowledge has allowed for a better understanding of the genetic cause, pathogenesis, underlying immunological mechanisms, epidemiological distribution, and prevalence of this disease. This opens up unpredictable perspectives of translating such knowledge into validated programs for prevention and surveillance, in order to reduce the health impact of this disease through medical interventions before cancer development. In our review, we summarize the updated guidelines of the screening, surveillance, and risk-reducing strategies for LS patients. Moreover, we present novel opportunities in the treatment and prevention of LS patients through harnessing the immune system using immunocheckpoint inhibitors and vaccines.

Abstract

Lynch syndrome (LS) is the most common inherited disorder responsible for an increased risk of developing cancers at different sites, most frequently in the gastrointestinal and genitourinary tracts, caused by a germline pathogenic variant affecting the DNA mismatch repair system. Surveillance and risk-reducing procedures are currently available and warranted for LS patients, depending on underlying germline mutation, and are focused on relevant targets for early cancer diagnosis or primary prevention. Although pharmacological approaches for preventing LS-associated cancer development were started many years ago, to date, aspirin remains the most studied drug intervention and the only one suggested by the main surveillance guidelines, despite the conflicting findings. Furthermore, we also note that remarkable advances in anticancer drug discovery have given a significant boost to the application of novel immunological strategies such as immunocheckpoint inhibitors and vaccines, not only for cancer treatment, but also in a preventive setting. In this review, we outline the clinical, biologic, genetic, and morphological features of LS as well as the recent three-pathways carcinogenesis model. Furthermore, we provide an update on the dedicated screening, surveillance, and risk-reducing strategies for LS patients and describe emerging opportunities of harnessing the immune system.

Diagnosis and management of Lynch syndrome

Lynch syndrome (LS) is a dominantly inherited cancer susceptibility syndrome defined by presence of pathogenic variants in DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2, or in deletions of the EPCAM gene. Although LS is present in about 1 in 400 people in the UK, it estimated that only 5% of people with this condition are aware of the diagnosis. Therefore, testing for LS in all new diagnoses of colorectal or endometrial cancers is now recommended in the UK, and gastroenterologists can offer 'mainstreamed' genetic testing for LS to patients with cancer. Because LS results in a high lifetime risk of colorectal, endometrial, gastric, ovarian, hepatobiliary, brain and other cancers, the lifelong care of affected individuals and their families requires a coordinated multidisciplinary approach. Interventions such as high-quality 2-yearly colonoscopy, prophylactic gynaecological surgery, and aspirin are proven to prevent and facilitate early diagnosis and prevention of cancers in this population, and improve patient outcomes. Recently, an appreciation of the mechanism of carcinogenesis in LS-associated cancers has contributed to the development of novel therapeutic and diagnostic approaches, with a gene-specific approach to disease management, with potential cancer-preventing vaccines in development. An adaptive approach to surgical or oncological management of LS-related cancers may be considered, including an important role for novel checkpoint inhibitor immunotherapy in locally advanced or metastatic disease. Therefore, a personalised approach to lifelong gene-specific management for people with LS provides many opportunities for cancer prevention and treatment which we outline in this review.

Vaccines for immunoprevention of DNA mismatch repair deficient cancers

The development of cancer vaccines to induce tumor-antigen specific immune responses was sparked by the identification of antigens specific to or overexpressed in cancer cells. However, weak immunogenicity and the mutational heterogeneity in many cancers have dampened cancer vaccine successes. With increasing information about mutational landscapes of cancers, mutational neoantigens can be predicted computationally to elicit strong immune responses by CD8 +cytotoxic T cells as major mediators of anticancer immune response. Neoantigens are potentially more robust immunogens and have revived interest in cancer vaccines. Cancers with deficiency in DNA mismatch repair have an exceptionally high mutational burden, including predictable neoantigens. Lynch syndrome is the most common inherited cancer syndrome and is caused by DNA mismatch repair gene mutations. Insertion and deletion mutations in coding microsatellites that occur during DNA replication include tumorigenesis drivers. The induced shift of protein reading frame generates neoantigens that are foreign to the immune system. Mismatch repair-deficient cancers and Lynch syndrome represent a paradigm population for the development of a preventive cancer vaccine, as the mutations induced by mismatch repair deficiency are predictable, resulting in a defined set of frameshift peptide neoantigens. Furthermore, Lynch syndrome mutation carriers constitute an identifiable high-risk population. We discuss the pathogenesis of DNA mismatch repair deficient cancers, in both Lynch syndrome and sporadic microsatellite-unstable cancers. We review evidence for pre-existing immune surveillance, the three mechanisms of immune evasion that occur in cancers and assess the implications of a preventive frameshift peptide neoantigen-based vaccine. We consider both preclinical and clinical experience to date. We discuss the feasibility of a cancer preventive vaccine for Lynch syndrome carriers and review current antigen selection and delivery strategies. Finally, we propose RNA vaccines as having robust potential for immunoprevention of Lynch syndrome cancers.

Lynch syndrome pre-screening and comprehensive characterization in a multi-center large cohort of Chinese patients with colorectal cancer

Objective:

Lynch syndrome (LS) pre-screening methods remain under-investigated in colorectal cancers (CRCs) in Asia. Here, we aimed to systematically investigate LS pre-screening and comprehensively characterize LS CRCs.

Methods:

Microsatellite instability (MSI) and germline variants of DNA mismatch repair (MMR) genes were examined in 406 deficient MMR (dMMR) and 250 proficient MMR CRCs. The genetic differences between LS and sporadic CRCs were studied with whole exome sequencing analysis.

Results:

The incidence of dMMR in Chinese patients with CRCs was 13.8%. Consistency analysis between MMR immunohistochemistry (IHC) and MSI testing showed the kappa value was 0.758. With next-generation sequencing (NGS), germline variants were detected in 154 CRCs. Finally, 88 patients with CRC were identified as having LS by Sanger sequencing. Among them, we discovered 21 previously unreported pathogenic germline variants of MMR genes. Chinese patients with LS, compared with sporadic CRCs, tended to be early-onset, right-sided, early-stage and mucinous. Overall, the performance of MMR IHC and MSI testing for LS pre-screening was comparable: the area under the ROC curve for dMMR, MSI-H, and MSI-H/L was 0.725, 0.750, and 0.745, respectively. dMMR_MSI-H LS and sporadic CRCs showed substantial differences in somatic genetic characteristics, including different variant frequencies of APC, CREBBP, and KRAS, as well as different enriched pathways of VEGF, Notch, TGFβR, mTOR, ErbB, and Rac protein signal transduction.

Conclusions:

MMR IHC and MSI testing were effective methods for LS pre-screening. The revealed clinical and somatic genetic characteristics in LS CRCs may have the potential to improve the performance of LS pre-screening in combination with dMMR/MSI.

Review article: Lynch Syndrome-a mechanistic and clinical management update

BACKGROUND

Lynch syndrome (LS) is an autosomal dominant familial condition caused by a pathogenic variant (PV) in a DNA mismatch repair gene, which then predisposes carriers to various cancers.

AIM

To review the pathogenesis, clinical presentation, differential diagnosis and clinical strategies for detection and management of LS.

METHODS

A narrative review synthesising knowledge from published literature, as well as current National Comprehensive Cancer Network guidelines for management of LS was conducted.

RESULTS

LS tumours are characterised by unique pathogenesis, ultimately resulting in hypermutation, microsatellite instability and high immunogenicity that has significant implications for cancer risk, clinical presentation, treatment and surveillance. LS is one of the most common hereditary causes of cancer, and about 1 in 279 individuals carry a PV in an LS gene that predisposes to associated cancers. Individuals with LS have increased risks for colorectal, endometrial and other cancers, with significant variation in lifetime risk by LS-associated gene.

CONCLUSIONS

As genetic testing becomes more widespread, the number of individuals identified with LS is expected to increase in the population. Understanding the pathogenesis of LS informs current strategies for detection and clinical management, and also guides future areas for clinical innovation. Unravelling the mechanisms by which these tumours evolve may help to more precisely tailor management by the gene involved.

Lynch syndrome; towards more personalized management?

Lynch syndrome is the most common inherited cause of colorectal (lifetime risk up to 70%) and endometrial cancer. The diagnosis of Lynch syndrome facilitates preventive measures aimed at reducing the incidence and mortality of cancer. Colonoscopic surveillance for colorectal cancer, aspirin, and prophylactic hysterectomy and bilateral salpo-oopherectomy for endometrial and/or ovarian cancer have demonstrated to effectively reduce cancer mortality in this population. However, the lifetime risk of each cancer in people with Lynch syndrome is gene-specific and may be modified by environmental factors. Furthermore, the benefits of surveillance strategies need to be balanced against the risk of over-diagnosis and be supported by evidence of improved outcomes from cancer diagnosis in surveillance. Therefore, people with Lynch syndrome may benefit from a personalized management approach.

The Different Immune Profiles of Normal Colonic Mucosa in Cancer-Free Lynch Syndrome Carriers and Lynch Syndrome Colorectal Cancer Patients

BACKGROUND & AIMS

Owing to the high load of immunogenic frameshift neoantigens, tumors arising in individuals with Lynch syndrome (LS), the most common inherited colorectal cancer (CRC) syndrome, are characterized by a pronounced immune infiltration. However, the immune status of normal colorectal mucosa in LS is not well characterized. We assessed the immune infiltrate in tumor-distant normal colorectal mucosa from LS CRC patients, sporadic microsatellite-unstable (MSI) and microsatellite-stable (MSS) CRC patients, and cancer-free LS carriers.

METHODS

CD3-positive, FOXP3-positive, and CD8-positive T cells were quantified in, respectively, 219, 233, and 201 formalin-fixed paraffin-embedded (FFPE) normal colonic mucosa tissue sections from CRC patients and cancer-free LS carriers and 26, 22, and 19 LS CRCs. CD3-positive T cells were also quantified in an independent cohort of 97 FFPE normal rectal mucosa tissue sections from LS carriers enrolled in the CAPP2 clinical trial. The expression of 770 immune-relevant genes was analyzed in a subset of samples with the use of the NanoString nCounter platform.

RESULTS

LS normal mucosa specimens showed significantly elevated CD3-, FOXP3-, and CD8-positive T-cell densities compared with non-LS control specimens. Gene expression profiling and cluster analysis revealed distinct immune profiles in LS carrier mucosa with and without cancer manifestation. Long-term follow-up of LS carriers within the CAPP2 trial found a correlation between mucosal T-cell infiltrate and time to subsequent tumor occurrence.

CONCLUSIONS

LS carriers show elevated mucosal T-cell infiltration even in the absence of cancer. The normal mucosa immune profile may be a temporary or permanent tumor risk modifier in LS carriers.

Quality of Colonoscopy Is Associated With Adenoma Detection and Postcolonoscopy Colorectal Cancer Prevention in Lynch Syndrome

BACKGROUND & AIMS

Colonoscopy reduces colorectal cancer (CRC) incidence and mortality in Lynch syndrome (LS) carriers. However, a high incidence of postcolonoscopy CRC (PCCRC) has been reported. Colonoscopy is highly dependent on endoscopist skill and is subject to quality variability. We aimed to evaluate the impact of key colonoscopy quality indicators on adenoma detection and prevention of PCCRC in LS.

METHODS

We conducted a multicenter study focused on LS carriers without previous CRC undergoing colonoscopy surveillance (n = 893). Incident colorectal neoplasia during surveillance and quality indicators of all colonoscopies were analyzed. We performed an emulated target trial comparing the results from the first and second surveillance colonoscopies to assess the effect of colonoscopy quality indicators on adenoma detection and PCCRC incidence. Risk analyses were conducted using a multivariable logistic regression model.

RESULTS

The 10-year cumulative incidence of adenoma and PCCRC was 60.6% (95% CI, 55.5%-65.2%) and 7.9% (95% CI, 5.2%-10.6%), respectively. Adequate bowel preparation (odds ratio [OR], 2.07; 95% CI, 1.06-4.3), complete colonoscopies (20% vs 0%; P = .01), and pan-chromoendoscopy use (OR, 2.14; 95% CI, 1.15-3.95) were associated with significant improvement in adenoma detection. PCCRC risk was significantly lower when colonoscopies were performed during a time interval of less than every 3 years (OR, 0.35; 95% CI, 0.14-0.97). We observed a consistent but not significant reduction in PCCRC risk for a previous complete examination (OR, 0.16; 95% CI, 0.03-1.28), adequate bowel preparation (OR, 0.64; 95% CI, 0.17-3.24), or previous use of high-definition colonoscopy (OR, 0.37; 95% CI, 0.02-2.33).

CONCLUSIONS

Complete colonoscopies with adequate bowel preparation and chromoendoscopy use are associated with improved adenoma detection, while surveillance intervals of less than 3 years are associated with a reduction of PCCRC incidence. In LS, high-quality colonoscopy surveillance is of utmost importance for CRC prevention.

Prevalence and Spectrum of Predisposition Genes With Germline Mutations Among Chinese Patients With Bowel Cancer

Background: Bowel cancer is the third-most common cancer and the second leading cause of cancer-related death worldwide. Bowel cancer has a substantial hereditary component; however, additional hereditary risk factors involved in bowel cancer pathogenesis have not been systematically defined.

Materials and Methods: A total of 573 patients with bowel cancer were enrolled in the present study, of whom 93.72% had colorectal cancer (CRC). Germline mutations were integrated with somatic mutation information via utilizing target next-generation sequencing.

Results: Pathogenic/Likely Pathogenic (P/LP) germline alterations were identified in 47 (8.2%) patients with bowel cancer and the ratio of the number of these patients with family history was significantly higher in the P/LP group than that noted in the non-pathogenic (Non-P) group. Certain rare germline alterations were noted, such as those noted in the following genes: FANCD2, CDH1, and FLCN. A total of 32 patients (68.1%) had germline alterations in the DNA-damage repair (DDR) genes and homologous recombination (HR) accounted for the highest proportion of this subgroup. By comparing 573 patients with bowel cancer with reference controls (China_MAPs database), significant associations (p < 0.01) were observed between the incidence of bowel cancer and the presence of mutations in APC, ATM, MLH1, FANCD2, MSH3, MSH6, PMS1, and RAD51D. Somatic gene differential analysis revealed a marked difference in 18 genes and a significant difference was also noted in tumor mutation burden (TMB) between germline mutation carriers and non-germline mutation subjects (p < 0.001). In addition, TMB in DDR mutation groups indicated a dramatic difference compared with the non-DDR mutation group (p < 0.01). However, no statistically significant differences in TMB were noted among detailed DDR pathways for patients with bowel cancer, irrespective of the presence of germline mutations. Moreover, a significantly higher level (p < 0.0001) of mutation count was observed in the DDR group from The Cancer Genome Atlas (TCGA) database and the DDR and non-DDR alteration groups displayed various immune profiles.

Conclusion: Chinese patients with bowel cancer exhibited a distinct spectrum of germline variants, with distinct molecular characteristics such as TMB and DDR. Furthermore, the information on somatic mutations obtained from TCGA database indicated that a deeper understanding of the interactions among DDR and immune cells would be useful to further investigate the role of DDR in bowel cancer.

How many is too many? Polyposis syndromes and what to do next

PURPOSE OF REVIEW

The goal of this review is to help providers recognize, diagnose and manage gastrointestinal (GI) polyposis syndromes.

RECENT FINDINGS

Intestinal polyps include a number of histological sub-types such as adenomas, serrated, hamartomas among others. Over a quarter of individuals undergoing screening colonoscopy are expected to have colonic adenomas. Although it is not uncommon for adults to have a few GI polyps in their lifetime, some individuals are found to have multiple polyps of varying histology throughout the GI tract. In these individuals, depending on polyp histology, number, location and size as well as extra-intestinal features and/or family history, a polyposis syndrome should be considered with appropriate testing and management.

SUMMARY

Diagnosis and management of polyposis syndromes has evolved with advent of multigene panel testing and new data on optimal surveillance strategies. Evidence-based recommendations and current practice guidelines for polyposis syndromes are reviewed here. Areas of uncertainty and future research are also highlighted.

Colorectal Cancer Screening Recommendations and Outcomes in Lynch Syndrome

Screening for colorectal cancer (CRC) in Lynch syndrome enables early detection and likely cancer prevention. CRC screening guidelines have evolved from universal to gene-specific recommendations based on lifetime neoplasia risks. Regular screening for Lynch syndrome reduces CRC-related mortality; however, high CRC incidence during regular colonoscopy screening suggests the possibility of nonpolypoid carcinogenesis. Colonoscopy is the primary modality for screening for Lynch syndrome with mixed and emerging data on quality metrics, chromoendoscopy, artificial intelligence, and nonendoscopic modalities. Screening adherence varies across studies. In this review, we present the current state of CRC screening recommendations, outcomes, and modalities in Lynch syndrome.

Gene-Specific Variation in Colorectal Cancer Surveillance Strategies for Lynch Syndrome

BACKGROUND AND AIMS

Lynch syndrome is associated with pathogenic variants in 4 mismatch repair (MMR) genes that increase lifetime risk of colorectal cancer. Guidelines recommend intensive colorectal cancer surveillance with colonoscopy every 1-2 years starting at age 25 years for all carriers of Lynch syndrome-associated variants, regardless of gene product. We constructed a simulation model to analyze the effects of different ages of colonoscopy initiation and surveillance intervals for each MMR gene (MLH1, MSH2, MSH6, and PMS2) on colorectal cancer incidence and mortality, quality-adjusted life-years, and cost.

METHODS

Using published literature, we developed a Markov simulation model of Lynch syndrome progression for patients with each MMR variant. The model simulated clinical trials of Lynch syndrome carriers, varying age of colonoscopy initiation (5-year increments from 25-40 years), and surveillance intervals (1-5 years). We assessed the optimal strategy for each gene, defined as the strategy with the highest quality-adjusted life-years and incremental cost-effectiveness ratio below a $100,000 willingness-to-pay threshold.

RESULTS

Optimal surveillance for patients with pathogenic variants in the MLH1 and MSH2 genes was colonoscopy starting at age 25 years, with 1- to 2-year surveillance intervals. Initiating colonoscopy at age 35 and 40 years, with 3-year intervals, was cost-effective for patients with pathogenic variants in MSH6 or PMS2, respectively.

CONCLUSIONS

We developed a simulation model to select optimal surveillance starting ages and intervals for patients with Lynch syndrome based on MMR variant. The model supports recommendations for intensive surveillance of patients with Lynch syndrome-associated variants in MLH1 or MSH2. However, for patients with Lynch syndrome-associated variants of MSH6 or PMS2, later initiation of surveillance at 35 and 40 years, respectively, and at 3-year intervals, can be considered.

Mismatch Repair (MMR) Gene Alteration and BRAF V600E Mutation Are Potential Predictive Biomarkers of Immune Checkpoint Inhibitors in MMR-Deficient Colorectal Cancer

BACKGROUND

Immune checkpoint inhibitor (ICI) therapy is highly effective in metastatic mismatch repair-deficient (MMR-D) colorectal cancer (CRC). In this study, we evaluated molecular and clinical predictors of ICI response in MMR-D CRC.

MATERIALS AND METHODS

Patient databases at four cancer institutions were queried. The Fisher exact test was performed to test the association of clinical and molecular markers. The Kaplan-Meier method was used to estimate progression-free survival (PFS) and compared by the log-rank test. Twelve- and 24-month PFS rates were compared by the Z test.

RESULTS

A total of 60 patients with CRC with MMR-D/microsatellite instability-high who previously received ICIs were identified. Patients with liver metastasis had a lower overall response rate as compared with other sites of metastasis (36.4% vs. 68.7%; p = .081). Patients with MLH1/PMS2 loss had worse 1-year and 2-year PFS rates compared with patients with MSH2/MSH6 loss (84.2% vs. 57.8% and 78.2% vs. 54.2%, respectively; p < .001). There were improved 1-year and 2-year PFS rates in patients with wild-type BRAF when compared with patients with BRAF V600E mutation (73.3% vs. 40%, and 73.3% vs. 26.7%; respectively; p < .001). Patients aged >65 had significantly worse PFS rates as compared with patients aged ≤65 (p < .001).

CONCLUSION

BRAF V600E mutation, MLH1 and/or PMS2 loss, as well as age >65 years and liver metastasis, may be predictive of duration of ICI response in patients with MMR-D CRC. Larger cohorts are needed to confirm our findings.

IMPLICATIONS FOR PRACTICE

The results of this study reveal clinically important biomarkers that potentially predict immune checkpoint inhibitor response in patients with mismatch repair-deficient colorectal cancer.

Endoscopy to Diagnose and Prevent Digestive Cancers in Lynch Syndrome

Lynch syndrome patients could benefit from various recommendations to prevent digestive cancers. In this review, we summarize the criteria to identify Lynch syndrome in patients with digestive cancers. We detail endoscopic screening procedures in patients with Lynch syndrome for gastric, small bowel, pancreatic, and colorectal cancers. We review the precise modalities of endoscopic follow-up, particularly the discrepancies that exist between the guidelines of the various scientific societies. We discuss the treatment of colorectal cancers in Lynch syndrome cases and patient adherence to endoscopic follow-up programs.

Defining the current role of immune checkpoint inhibitors in the treatment of mismatch repair-deficient/microsatellite stability-high colorectal cancer and shedding light on future approaches

Introduction: Mismatch repair deficient (MMR-D)/microsatellite instability-high (MSI-H) colorectal cancer (CRC) carries unique biologic features including high tumor mutation burden, increased amount of mutation-associated neoantigen generation, and the presence of marked tumor-infiltrating lymphocytes. Immune checkpoint inhibitor (ICI) therapy has rapidly changed the treatment algorithm of MMR-D/MSI-H CRC.Areas covered: In this review article, we discuss the recent data regarding the use of ICIs in metastatic MMR-D/MSI-H CRC patients. We also elaborated on potential biomarkers of ICI response and innovative therapeutic approaches that may prevail resistance mechanisms for the treatment of MMR-D/MSI-H colorectal cancer.Expert opinion: Pembrolizumab was recently granted approval by the FDA as first-line therapy for metastatic MMR-D/MSI-H CRC based on the results of the Keynote 177 study. The combination of nivolumab and ipilimumab will also likely be a choice for the initial therapy of MMR-D/MSI-H CRC in the near future. More therapeutic modalities with novel immunomodulatory agents as well as targeted therapy directed to immune resistance pathways are needed. The novel approaches discussed in this review article will define potential treatment options for the management of MMR-D/MSI-H CRC patients who progress on first-line ICI therapy.

From Genetics to Histomolecular Characterization: An Insight into Colorectal Carcinogenesis in Lynch Syndrome

Lynch syndrome is a hereditary cancer-predisposing syndrome caused by germline defects in DNA mismatch repair (MMR) genes such as MLH1, MSH2, MSH6, and PMS2. Carriers of pathogenic mutations in these genes have an increased lifetime risk of developing colorectal cancer (CRC) and other malignancies. Despite intensive surveillance, Lynch patients typically develop CRC after 10 years of follow-up, regardless of the screening interval. Recently, three different molecular models of colorectal carcinogenesis were identified in Lynch patients based on when MMR deficiency is acquired. In the first pathway, adenoma formation occurs in an MMR-proficient background, and carcinogenesis is characterized by APC and/or KRAS mutation and IGF2, NEUROG1, CDK2A, and/or CRABP1 hypermethylation. In the second pathway, deficiency in the MMR pathway is an early event arising in macroscopically normal gut surface before adenoma formation. In the third pathway, which is associated with mutations in CTNNB1 and/or TP53, the adenoma step is skipped, with fast and invasive tumor growth occurring in an MMR-deficient context. Here, we describe the association between molecular and histological features in these three routes of colorectal carcinogenesis in Lynch patients. The findings summarized in this review may guide the use of individualized surveillance guidelines based on a patient’s carcinogenesis subtype.

Distinct Mutational Profile of Lynch Syndrome Colorectal Cancers Diagnosed under Regular Colonoscopy Surveillance

Regular colonoscopy even with short intervals does not prevent all colorectal cancers (CRC) in Lynch syndrome (LS). In the present study, we asked whether cancers detected under regular colonoscopy surveillance (incident cancers) are phenotypically different from cancers detected at first colonoscopy (prevalent cancers). We analyzed clinical, histological, immunological and mutational characteristics, including panel sequencing and high-throughput coding microsatellite (cMS) analysis, in 28 incident and 67 prevalent LS CRCs (n total = 95). Incident cancers presented with lower UICC and T stage compared to prevalent cancers (p < 0.0005). The majority of incident cancers (21/28) were detected after previous colonoscopy without any pathological findings. On the molecular level, incident cancers presented with a significantly lower KRAS codon 12/13 (1/23, 4.3% vs. 11/21, 52%; p = 0.0005) and pathogenic TP53 mutation frequency (0/17, 0% vs. 7/21, 33.3%; p = 0.0108,) compared to prevalent cancers; 10/17 (58.8%) incident cancers harbored one or more truncating APC mutations, all showing mutational signatures of mismatch repair (MMR) deficiency. The proportion of MMR deficiency-related mutational events was significantly higher in incident compared to prevalent CRC (p = 0.018). In conclusion, our study identifies a set of features indicative of biological differences between incident and prevalent cancers in LS, which should further be monitored in prospective LS screening studies to guide towards optimized prevention protocols.

The diverse molecular profiles of lynch syndrome-associated colorectal cancers are (highly) dependent on underlying germline mismatch repair mutations

Lynch syndrome (LS) is a hereditary cancer syndrome that accounts for 3% of all new colorectal cancer (CRC) cases. Patients carry a germline pathogenic variant in one of the mismatch repair (MMR) genes (MLH1, MSH2, MSH6 or PMS2), which encode proteins involved in a post-replicative proofreading and editing mechanism. The clinical presentation of LS is highly heterogeneous, showing high variability in age at onset and penetrance of cancer, which may be partly attributable to the molecular profiles of carcinomas. This review discusses the frequency of alterations in the WNT/B-CATENIN, RAF/MEK/ERK and PI3K/PTEN/AKT pathways identified in all four LS subgroups and how these changes may relate to the 'three pathway model' of carcinogenesis, in which LS CRCs develop from MMR-proficient adenomas, MMR-deficient adenomas or directly from MMR-deficient crypts. Understanding the specific differences in carcinogenesis for each LS subgroup will aid in the further optimization of guidelines for diagnosis, surveillance and treatment.

A Meta-Analysis of Obesity and Risk of Colorectal Cancer in Patients with Lynch Syndrome: The Impact of Sex and Genetics

There appears to be a sex-specific association between obesity and colorectal neoplasia in patients with Lynch Syndrome (LS). We meta-analyzed studies reporting on obesity and colorectal cancer (CRC) risk in LS patients to test whether obese subjects were at increased risk of cancer compared to those of normal weight. We explored also a possible sex-specific relationship between adiposity and CRC risk among patients with LS. The summary relative risk (SRR) and 95% confidence intervals (CI) were calculated through random effect models. We investigated the causes of between-study heterogeneity and assessed the presence of publication bias. We were able to retrieve suitable data from four independent studies. We found a twofold risk of CRC in obese men compared to nonobese men (SRR = 2.09; 95%CI: 1.23–3.55, I² = 33%), and no indication of publication bias (p = 0.13). No significantly increased risk due to obesity was found for women. A 49% increased CRC risk for obesity was found for subjects with an MLH1 mutation (SRR = 1.49; 95%CI: 1.11–1.99, I² = 0%). These results confirm the different effects of sex on obesity and CRC risk and also support the public measures to reduce overweight in people with LS, particularly for men.

Mathematical modeling of multiple pathways in colorectal carcinogenesis using dynamical systems with Kronecker structure

Like many other types of cancer, colorectal cancer (CRC) develops through multiple pathways of carcinogenesis. This is also true for colorectal carcinogenesis in Lynch syndrome (LS), the most common inherited CRC syndrome. However, a comprehensive understanding of the distribution of these pathways of carcinogenesis, which allows for tailored clinical treatment and even prevention, is still lacking. We suggest a linear dynamical system modeling the evolution of different pathways of colorectal carcinogenesis based on the involved driver mutations. The model consists of different components accounting for independent and dependent mutational processes. We define the driver gene mutation graphs and combine them using the Cartesian graph product. This leads to matrix components built by the Kronecker sum and product of the adjacency matrices of the gene mutation graphs enabling a thorough mathematical analysis and medical interpretation. Using the Kronecker structure, we developed a mathematical model which we applied exemplarily to the three pathways of colorectal carcinogenesis in LS. Beside a pathogenic germline variant in one of the DNA mismatch repair (MMR) genes, driver mutations in APC, CTNNB1, KRAS and TP53 are considered. We exemplarily incorporate mutational dependencies, such as increased point mutation rates after MMR deficiency, and based on recent experimental data, biallelic somatic CTNNB1 mutations as common drivers of LS-associated CRCs. With the model and parameter choice, we obtained simulation results that are in concordance with clinical observations. These include the evolution of MMR-deficient crypts as early precursors in LS carcinogenesis and the influence of variants in MMR genes thereon. The proportions of MMR-deficient and MMR-proficient APC-inactivated crypts as first measure for the distribution among the pathways in LS-associated colorectal carcinogenesis are compatible with clinical observations. The approach provides a modular framework for modeling multiple pathways of carcinogenesis yielding promising results in concordance with clinical observations in LS CRCs.

Colorectal cancer screening in Lynch syndrome: Indication, techniques and future perspectives

Lynch syndrome (LS) is an inherited predisposition to colorectal cancer (CRC), responsible for 3-5% of all CRC. This syndrome is characterized by the early occurrence of colorectal neoplastic lesions, with variable incidences depending on the type of pathogenic variants in MMR genes (MLH1, MSH2, MSH6, PMS2 and EPCAM) and demographics factors such as gender, body mass index, tobacco use and physical activity. Similar to sporadic cancers, colorectal screening by colonoscopy is efficient because it is associated with a reduction >50% of both CRC incidence and CRC related mortality. To that end, most guidelines recommend high definition screening colonoscopies in dedicated centers, starting at the age of 20-25 years old, with a surveillance interval of 1-2 years. In this review, we discuss the importance of high definition colonoscopies, including the compliance to specific key performance indicators, as well as the expected benefits of specific imaging modalities including virtual chromoendoscopy and dye-spray chromoendoscopy.

Discovering the Mutational Profile of Early Colorectal Lesions: A Translational Impact

Simple Summary

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Next-generation sequencing technologies have identified new candidate genes and deepened the knowledge of the molecular mechanisms underlying the progression of colonic adenomas towards CRC. The main genetic, epigenetic, and molecular alterations driving the onset and progression of CRC in both hereditary and sporadic settings have also been investigated. The evaluation of the CRC risk based on the molecular characterization of early pre-cancerous lesions may contribute to the development of targeted preventive strategies development, help define specific risk profiles, and identify patients who will benefit from targeted endoscopic surveillance.

Abstract

Colorectal cancer (CRC) develops through a multi-step process characterized by the acquisition of multiple somatic mutations in oncogenes and tumor-suppressor genes, epigenetic alterations and genomic instability. These events lead to the progression from precancerous lesions to advanced carcinomas. This process requires several years in a sporadic setting, while occurring at an early age and or faster in patients affected by hereditary CRC-predisposing syndromes. Since advanced CRC is largely untreatable or unresponsive to standard or targeted therapies, the endoscopic treatment of colonic lesions remains the most efficient CRC-preventive strategy. In this review, we discuss recent studies that have assessed the genetic alterations in early colorectal lesions in both hereditary and sporadic settings. Establishing the genetic profile of early colorectal lesions is a critical goal in the development of risk-based preventive strategies.