Molecular functions of MCM8 and MCM9 and their associated pathologies

Minichromosome Maintenance 8 Homologous Recombination Repair Factor (MCM8) and Minichromosome Maintenance 9 Homologous Recombination Repair Factor (MCM9) are recently discovered minichromosome maintenance proteins and are implicated in multiple DNA-related processes and pathologies, including DNA replication (initiation), meiosis, homologous recombination and mismatch repair. Consistent with these molecular functions, variants of MCM8/MCM9 may predispose carriers to disorders such as infertility and cancer and should therefore be included in relevant diagnostic testing. In this overview of the (patho)physiological functions of MCM8 and MCM9 and the phenotype of MCM8/MCM9 variant carriers, we explore the potential clinical implications of MCM8/MCM9 variant carriership and highlight important future directions of MCM8 and MCM9 research. With this review, we hope to contribute to better MCM8/MCM9 variant carrier management and the potential utilization of MCM8 and MCM9 in other facets of scientific research and medical care.

The present and future of gastroenterology and hepatology: an international SWOT analysis (the GASTROSWOT project)

GASTROSWOT is a strategic analysis of the current and projected states of the different subspecialties in gastroenterology that aims to provide guidance for research, clinical, and financial planning in gastroenterology. We executed a consensus-based international strengths, weaknesses, opportunities, and threats (SWOT) analysis. Four general coordinators, six field coordinators, and 12 experts participated in the study. SWOTs were provided for the following fields: neurogastroenterology, functional gastrointestinal disorders, and upper gastrointestinal diseases; inflammatory bowel disease; pancreatology and biliary diseases; endoscopy; gastrointestinal oncology; and hepatology. The GASTROSWOT analysis highlights the following in the current state of the field of gastroenterology: the incidence and complexity of several gastrointestinal diseases, including malignancies, are increasing; the COVID-19 pandemic has affected patient care on several levels; and with the advent of technical innovations in gastroenterology, a well trained workforce and strategic planning are required to optimise health-care utilisation. The analysis calls attention to the following in the future of gastroenterology: artificial intelligence and the use of big data will speed up discovery and smarter health-care provision in the field; the growth and diversification of gastroenterological specialties will improve specialised care for patients, but could promote fragmentation of care and health system inefficiencies; and furthermore, thoughtful planning is needed to reach an effective balance between the need for subspecialists and the value of general gastroenterology services.

Prognostic Impact of An Integrative Landscape of Clinical, Immune, and Molecular Features in Non-Metastatic Rectal Cancer

Rectal Cancer (RC) is a complex disease that involves highly variable treatment responses. Currently, there is a lack of reliable markers beyond TNM to deliver a personalized treatment in a cancer setting where the goal is a curative treatment. Here, we performed an integrated characterization of the predictive and prognostic role of clinical features, mismatch-repair deficiency markers, HER2, CDX2, PD-L1 expression, and CD3-CD8+ tumor-infiltrating lymphocytes (TILs) coupled with targeted DNA sequencing of 76 non-metastatic RC patients assigned to total mesorectal excision upfront (TME; n = 15) or neoadjuvant chemo-radiotherapy treatment (nCRT; n = 61) followed by TME. Eighty-two percent of RC cases displayed mutations affecting cancer driver genes such as TP53, APC, KRAS, ATM, and PIK3CA. Good response to nCRT treatment was observed in approximately 40% of the RC cases, and poor pathological tumor regression was significantly associated with worse disease-free survival (DFS, HR = 3.45; 95%CI = 1.14-10.4; p = 0.028). High neutrophils-platelets score (NPS) (OR = 10.52; 95%CI=1.34-82.6; p = 0.025) and KRAS mutated cases (OR = 5.49; 95%CI = 1.06-28.4; p = 0.042) were identified as independent predictive factors of poor response to nCRT treatment in a multivariate analysis. Furthermore, a Cox proportional-hazard model showed that the KRAS mutational status was an independent prognostic factor associated with higher risk of local recurrence (HR = 9.68; 95%CI = 1.01-93.2; p <0.05) and shorter DFS (HR = 2.55; 95%CI = 1.05-6.21; p <0.05), while high CEA serum levels were associated with poor DFS (HR = 2.63; 95%CI = 1.01-6.85; p <0.05). Integrated clinical and molecular-based unsupervised analysis allowed us to identify two RC prognostic groups (cluster 1 and cluster 2) associated with disease-specific OS (HR = 20.64; 95%CI = 2.63-162.2; p <0.0001), metastasis-free survival (HR = 3.67; 95%CI = 1.22-11; p = 0.012), local recurrence-free survival (HR = 3.34; 95%CI = 0.96-11.6; p = 0.043) and worse DFS (HR = 2.68; 95%CI = 1.18-6.06; p = 0.012). The worst prognosis cluster 2 was enriched by stage III high-risk clinical tumors, poor responders to nCRT, with low TILs density and high frequency of KRAS and TP53 mutated cases compared with the best prognosis cluster 1 (p <0.05). Overall, this study provides a comprehensive and integrated characterization of non-metastatic RC cases as a new insight to deliver a personalized therapeutic approach.

Germline biallelic Mcm8 variants are associated with early-onset Lynch-like syndrome

Lynch syndrome is the most common cause of hereditary colorectal cancer (CRC), and it is characterized by DNA mismatch repair (MMR) deficiency. The term Lynch-like syndrome (LLS) is used for patients with MMR-deficient tumors and neither germline mutation in MLH1, MSH2, MSH6, PMS2, or EPCAM nor MLH1 somatic methylation. Biallelic somatic inactivation or cryptic germline MMR variants undetected during genetic testing have been proposed to be involved. Sixteen patients with early-onset LLS CRC were selected for germline and tumor whole-exome sequencing. Two potentially pathogenic germline MCM8 variants were detected in a male patient with LLS with fertility problems. A knockout cellular model for MCM8 was generated by CRISPR/Cas9 and detected genetic variants were produced by mutagenesis. DNA damage, microsatellite instability, and mutational signatures were monitored. DNA damage was evident for MCM8^KO cells and the analyzed genetic variants. Microsatellite instability and mutational signatures in MCM8^KO cells were compatible with the involvement of MCM8 in MMR. Replication in an independent familial cancer cohort detected additional carriers. Unexplained MMR-deficient CRC cases, even showing somatic biallelic MMR inactivation, may be caused by underlying germline defects in genes different than MMR genes. We suggest MCM8 as a gene involved in CRC germline predisposition with a recessive pattern of inheritance.

MCM8 may be involved in germline predisposition to colorectal cancer in Lynch-like syndrome cases.

Abstract 2366: Germline biallelic mutations in MCM8 are associated with early-onset Lynch-like syndrome

Purpose: The most frequent cause of hereditary colorectal cancer (CRC) is Lynch syndrome, accounting for 3% of all CRC cases. The underlying germline predisposition is a mutation in any of the four mismatch repair (MMR) genes (MLH1, MSH2, MSH6, PMS2), while microsatellite instability (MSI) is a hallmark of these tumors. However, CRC cases with MSI, no MLH1 somatic hypermethylation and absence of MMR germline mutation account for up to 60% of cases of MMR-defective tumors. They have been termed Lynch-like syndrome (LLS) and treatment management decisions are complicated due to unconfirmed suspicions of hereditary cancer. The aim of the present study was to investigate whether LLS cases in patients under the age of 40 carry potentially pathogenic germline variants in new genes for CRC predisposition causing a MMR-defective tumor phenotype.

Methods: We performed whole-exome sequencing (WES) in the germline and tumoral DNA of 16 early-onset LLS patients. We filtered for recessive germline variants in genes involved in DNA repair. An exhaustive functional evaluation for 2 MCM8 genetic variants detected in one patient was performed. The CRISPR/Cas9 system was used to generate MCM8ko clones in a cell model (DLD-1). Site-directed mutagenesis produced the genetic variants for ectopic expression in the MCM8ko model. Functional characterization included the comet assay, which detected DNA damage induced by oxaliplatin in the transfected cells. MCM8ko cells were evaluated for MSI after 30, 60 and 90 days of culture, and mutational signatures were assessed with SigProfiler.

Results: The MCM8 variants c.351_354delAAAG (p.Lys118GlufsTer5, p.K118fs) and c.414A&gt;G (p.Ile138Met, p.I138M) were identified in one early-onset LLS patient with biallelic somatic inactivation of MLH1. Manual evaluation of WES data showed that germline MCM8 variants were in trans. In the comet assay, both MCM8 variants revealed higher sensitivity to oxaliplatin and more DNA damage compared to the wild-type control. One of the MCM8KO clones showed MSI after 30 days of sub-culturing. After 120 days, MCM8KO clones had acquired a significant contribution of the SBS20 mutational signature, which is associated with defective MMR DNA.

Conclusions: We postulate that MCM8 is a new germline CRC predisposing gene in early-onset LLS, which may be involved in both MMR and double-strand break repair. We further provide evidence that in some LLS CRC cases, especially in young patients, the biallelic somatic MMR inactivation may be caused by new CRC germline predisposing genes. Additional mutational screening is warranted for such cases.

Citation Format: Mariano Golubicki, Laia Bonjoch, José G. Acuña-Ochoa, Marcos Diaz-Gay, Jennifer Muñoz, Miriam Cuatrecasas, Teresa Ocaña, Juan Robbio, Enrique L. Roca, Antoni Castells, Fracesc Balaguer, Marina Antelo, Sergi Castellvi-Bel. Germline biallelic mutations in MCM8 are associated with early-onset Lynch-like syndrome [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2366.

Lynch-like syndrome is as frequent as Lynch syndrome in early-onset nonfamilial nonpolyposis colorectal cancer

Early-onset (<50 years-old) nonpolyposis nonfamilial colorectal cancer (EO NP NF CRC) is a common clinical challenge. Although Lynch syndrome (LS) is associated with EO CRC, the frequency of this syndrome in the EO NF cases remains unknown. Besides, mismatch repair deficient (MMRd) CRCs with negative MMR gene testing have recently been described in up to 60% of cases and termed "Lynch-like syndrome" (LLS). Management and counseling decisions of these patients are complicated because of unconfirmed suspicions of hereditary cancer. To define the prevalence of MMR deficient CRCs, LS and LLS in patients with EO NP NF CRC, we recruited 102 patients with a first diagnosis of NP NF CRC ≤ 50 years old during 2003-2009 who underwent genetic counseling at our institution in Argentina. Tumor immunohistochemical (IHC) MMR for protein expression and microsatellite instability (MSI) status were evaluated, and in those with loss of MLH1 expression by IHC, somatic BRAF V600E mutation and both somatic and germline MLH1 methylation levels were studied. Tumors characterized as MMRd without somatic BRAF mutation nor MLH1 methylation were sent for germline analysis. Twenty one (20.6%) tumors were MMRd. Fourteen of 16 putative LS cases underwent germline testing: 6 pathogenic mutations were identified and 8 cases had no identifiable pathogenic mutations. The prevalence of LS and LLS in this cohort was 5.8% (6/102) and 7.8% (8/102), respectively. As a conclusion we found that 20% of patients with EO NP NF CRC have MMRd tumors, and at least half of these are likely to have LLS.

From colorectal cancer pattern to the characterization of individuals at risk: Picture for genetic research in Latin America

Colorectal cancer (CRC) is one of the most common cancers in Latin America and the Caribbean, with the highest rates reported for Uruguay, Brazil and Argentina. We provide a global snapshot of the CRC patterns, how screening is performed, and compared/contrasted to the genetic profile of Lynch syndrome (LS) in the region. From the literature, we find that only nine (20%) of the Latin America and the Caribbean countries have developed guidelines for early detection of CRC, and also with a low adherence. We describe a genetic profile of LS, including a total of 2,685 suspected families, where confirmed LS ranged from 8% in Uruguay and Argentina to 60% in Peru. Among confirmed LS, path_MLH1 variants were most commonly identified in Peru (82%), Mexico (80%), Chile (60%), and path_MSH2/EPCAM variants were most frequently identified in Colombia (80%) and Argentina (47%). Path_MSH6 and path_PMS2 variants were less common, but they showed important presence in Brazil (15%) and Chile (10%), respectively. Important differences exist at identifying LS families in Latin American countries, where the spectrum of path_MLH1 and path_MSH2 variants are those most frequently identified. Our findings have an impact on the evaluation of the patients and their relatives at risk for LS, derived from the gene affected. Although the awareness of hereditary cancer and genetic testing has improved in the last decade, it is remains deficient, with 39%–80% of the families not being identified for LS among those who actually met both the clinical criteria for LS and showed MMR deficiency.

A high degree of LINE-1 hypomethylation is a unique feature of early-onset colorectal cancer

OBJECTIVE

Early-onset colorectal cancer (CRC) represents a clinically distinct form of CRC that is often associated with a poor prognosis. Methylation levels of genomic repeats such as LINE-1 elements have been recognized as independent factors for increased cancer-related mortality. The methylation status of LINE-1 elements in early-onset CRC has not been analyzed previously.

DESIGN

We analyzed 343 CRC tissues and 32 normal colonic mucosa samples, including 2 independent cohorts of CRC diagnosed ≤ 50 years old (n=188), a group of sporadic CRC >50 years (MSS n=89; MSI n=46), and a group of Lynch syndrome CRCs (n=20). Tumor mismatch repair protein expression, microsatellite instability status, LINE-1 and MLH1 methylation, somatic BRAF V600E mutation, and germline MUTYH mutations were evaluated.

RESULTS

Mean LINE-1 methylation levels (± SD) in the five study groups were early-onset CRC, 56.6% (8.6); sporadic MSI, 67.1% (5.5); sporadic MSS, 65.1% (6.3); Lynch syndrome, 66.3% (4.5) and normal mucosa, 76.5% (1.5). Early-onset CRC had significantly lower LINE-1 methylation than any other group (p<0.0001). Compared to patients with <65% LINE-1 methylation in tumors, those with ≥ 65% LINE-1 methylation had significantly better overall survival (p=0.026, log rank test).

CONCLUSIONS

LINE-1 hypomethylation constitutes a potentially important feature of early-onset CRC, and suggests a distinct molecular subtype. Further studies are needed to assess the potential of LINE-1 methylation status as a prognostic biomarker for young people with CRC.

[Image-guided percutaneous biopsy of gastric lesions with suspicion of malignancy and negative endoscopic biopsies: report of our experience and revision of the literature]

BACKGROUND

Endoscopic biopsy is the most efficient way to obtain a biopsy specimen from neoplastic lesions located in the stomach. Therefore, it is the procedure of choice to obtain a histologic diagnosis of gastric cancer. Image guided percutaneous biopsy is an alternative method to obtain histologic material for definitive diagnosis when the biopsies are negative for neoplastic cells in several endoscopies.

OBJECTIVE

The purpose of this study was to evaluate the efficacy, complications, and histologic results of image guided percutaneous biopsies of gastric lesions in our center.

MATERIALS AND METHODS

Between March 2004 and March 2007, 6 patients with strong suspicion of gastric cancer and negative endoscopic biopsies were referred for image guided percutaneous biopsy of gastric lesions (5 were guided by ultrasonography and 1 by CT scan).

RESULTS

A histologic diagnosis was made in 5 patients: poorly differentated signet-ring cell carcinoma 3, B-cell non-Hodgkin's lymphoma 2. One patient suffered a perforation during the procedure and the final histologic diagnosis was obtained after the consequent surgery (B-cell non-Hodgkin's lymphoma).

CONCLUSION

Despite of the scant published series, image guided percutaneous biopsy of gastric lesions is an useful, safe and effective technique to obtain a histologic diagnosis in patients with strong suspicion of gastric cancer and negative endoscopic biopsies.

Systematic review and meta-analysis of observational studies on the prevalence of fractures in coeliac disease

BACKGROUND/AIMS

Evidence of an increased bone fracture risk in coeliac disease is on debate. Our aim was to review systematically the current published information on fractures in coeliac disease and to perform a meta-analysis.

METHODS

Case-control and cohort designs were identified by searching MEDLINE (1966-April 2007) and LILACS (1982-April 2007). Participants were adult coeliac disease patients of any sex and the outcome measure was the presence of any fracture. Studies were screened for inclusion by two authors who independently extracted the data. Methodological quality was assessed using the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology Statement) recommendations. Data were analysed using the RevMan Analyses statistical package in Review Manager (version 4.2.8) and reported as pooled odds ratio using a random effect model. Heterogeneity was investigated (standard chi(2) test) and sensitivity analysis was performed based on the reported quality and design type.

RESULTS

While 60 of 405 studies met the initial screening criteria, only 8 met inclusion criteria after detailed review. These studies evaluated a total of 20,955 coeliac disease patients having 1819 (8.7%) fractures and 96,777 controls with 5955 (6.1%) fractures (pooled odds ratio=1.43; 95% confidence interval 1.15-1.78) with considerable heterogeneity among studies (p<0.00001).

CONCLUSIONS

Our meta-analysis confirms a significant association between bone fractures and coeliac disease. However, qualitative and quantitative differences among studies were evident. Further research is necessary to investigate the relevance of this heterogeneity.

Relationship among cystectomy, microvessel density and prognosis in stage T1 transitional cell carcinoma of the bladder

PURPOSE

The selection of therapy for stage T1 bladder cancer is controversial, and reliable biomarkers that identify patients likely to require cystectomy for local disease control have not been established. We evaluated our experience with T1 bladder cancer to determine whether early cystectomy improves prognosis, and whether microvessel density has prognostic value for T1 lesions and could be used for patient selection.

MATERIALS AND METHODS

We retrospectively reviewed the records of 88 patients with T1 transitional cell carcinoma of the bladder. Patient outcome was correlated with therapeutic intervention. Paraffin embedded tissue from 54 patients was available for factor VIII immunohistochemical staining for microvessel density quantification.

RESULTS

Median followup was 48 months (range 12 to 239). Of the patients 34% had no tumor recurrence. The rates of recurrence only and progression to higher stage disease were 41 and 25%, respectively. The survival of patients in whom disease progressed was diminished (p = 0.0002). Grade did not predict recurrence or progression nor did cystectomy provide a survival advantage. Microvessel density did not correlate with recurrence or progression.

CONCLUSIONS

Patients with T1 bladder cancer have a high risk of recurrence and progression. Tumor progression has a significant negative impact on survival. Neither grade nor early tumor recurrence predicted disease progression. Because early cystectomy did not improve patient outcome, we suggest reserving cystectomy for patients with progression or disease refractory to local therapy. Microvessel density is not a prognostic marker for T1 bladder cancer and has no value in selecting patients with T1 disease for cystectomy.

p53 and RB expression predict progression in T1 bladder cancer

The optimal clinical management of minimally invasive (stage T1) bladder cancer is controversial. T1 bladder cancers share characteristics of both noninvasive (Ta) papillary cancer and high stage, muscle-invasive bladder cancers. Patients with T1 bladder cancer have a higher risk of cancer progression and death than do patients with Ta bladder cancer. However, this risk is much lower than that of patients with high-stage bladder cancers. Methods of identifying T1 bladder cancer patients at greatest risk for progression may significantly improve clinical management. We retrospectively evaluated two tumor suppressor genes, p53 and RB, as potential prognostic markers for progression in a cohort of 45 patients with pT1 bladder cancer. Median follow-up for these individuals was greater than 3.5 years. Of this group, 58% had altered p53 expression based on positive p53 immunostaining. Three patterns for RB nuclear protein staining were observed: absent, heterogeneous (normal), and strongly homogeneous. Progression-free survival was similar for patients with loss of RB protein expression and those with apparent overexpression of RB protein. Therefore, both staining patterns were considered abnormal. Patients with normal expression of both proteins (i.e., p53 negative and RB heterogeneously positive) had an excellent outcome, with no patient showing disease progression, whereas patients with abnormal expression of either or both proteins had a significant increase in progression (P = 0.04 and P = 0.005, respectively). These data support the stratification of T1 bladder cancer patients based on p53 and RB nuclear protein status and suggest that patients with normal protein expression for both genes can be managed conservatively, whereas patients with alterations in one and particularly both genes require more aggressive treatment.