Pathogenic Germline Mutations of DNA Repair Pathway Components in Early-Onset Sporadic Colorectal Polyp and Cancer Patients

Comparison of immediate germline sequencing and multi-step screening for Lynch syndrome detection in high-risk endometrial and colorectal cancer patients

OBJECTIVE

Lynch syndrome (LS) is a hereditary cancer predisposition syndrome with a significantly increased risk of colorectal and endometrial cancers. Current standard practice involves universal screening for LS in patients with newly diagnosed colorectal or endometrial cancer using a multi-step screening protocol (MSP). However, MSP may not always accurately identify LS cases. To address this limitation, we compared the diagnostic performance of immediate germline sequencing (IGS) with MSP in a high-risk group.

METHODS

A total of 31 Taiwanese women with synchronous or metachronous endometrial and colorectal malignancies underwent MSP which included immunohistochemical staining of DNA mismatch repair (MMR) proteins, MLH1 promoter hypermethylation analysis, and germline sequencing to identify pathogenic variants. All patients who were excluded during MSP received germline sequencing for MMR genes to simulate IGS for the detection of LS.

RESULTS

Our findings indicate that IGS surpassed MSP in terms of diagnostic yield (29.0% vs. 19.4%, respectively) and sensitivity (90% vs. 60%, respectively). Specifically, IGS successfully identified nine LS cases, which is 50% more than the number detected through MSP. Additionally, germline methylation analysis revealed one more LS case with constitutional MLH1 promoter hypermethylation, bringing the total LS cases to ten (32.3%). Intriguingly, we observed no significant differences in clinical characteristics or overall survival between patients with and without LS in our cohort.

CONCLUSION

Our study suggests that IGS may potentially offer a more effective approach compared to MSP in identifying LS among high-risk patients. This advantage is evident when patients have been pre-selected utilizing specific clinical criteria.

Whole exome sequencing identifies MAP3K1, MSH2, and MLH1 as potential cancer-predisposing genes in familial early-onset colorectal cancer

The incidence of early-onset colorectal cancer (CRC), which affects people under 50, is increasing for unknown reasons. Additionally, no underlying genetic cause is found in 20%-30% of patients suspected of having familial CRC syndrome. Whole exome sequencing (WES) has generated evidence for new genes associated with CRC susceptibility, but many patients remain undiagnosed. This study applied WES in five early-onset CRC patients from three unrelated families to identify novel genetic variants that could be linked to rapid disease development. Furthermore, the candidate variants were validated using Sanger sequencing. Two heterozygote variations, c.1077-2A>G and c.199G>A, were found in the MSH2 and the MLH1 genes, respectively. Sanger sequencing analysis confirmed that these (likely) pathogenic mutations segregated in all the affected families' members. In addition, we identified a rare heterozygote variant (c.175C>T) with suspected pathogenic potential in the MAP3K1 gene; formally the variant is of uncertain significance (VUS). Our findings support the hypothesis that CRC onset may be oligogenic and molecularly heterogeneous. Larger and more robust studies are needed to understand the genetic basis of early-onset CRC development, combined with novel functional analyses and omics approaches.

Variant Characterization of a Representative Large Pedigree Suggests "Variant Risk Clusters" Convey Varying Predisposition of Risk to Lynch Syndrome

Recently, worldwide incidences of young adult aggressive colorectal cancer (CRC) have rapidly increased. Of these incidences diagnosed as familial Lynch syndrome (LS) CRC, outcomes are extremely poor. In this study, we seek novel familial germline variants from a large pedigree Tunisian family with 12 LS-affected individuals to identify putative germline variants associated with varying risk of LS. Whole-genome sequencing analysis was performed to identify known and novel germline variants shared between affected and non-affected pedigree members. SNPs, indels, and structural variants (SVs) were computationally identified, and their oncological influence was predicted using the Genetic Association of Complex Diseases and Disorders, OncoKB, and My Cancer Genome databases. Of 94 germline familial variants identified with predicted functional impact, 37 SNPs/indels were detected in 28 genes, 2 of which (MLH1 and PRH1-TAS2R14) have known association with CRC and 4 others (PPP1R13B, LAMA5, FTO, and NLRP14) have known association with non-CRC cancers. In addition, 48 of 57 identified SVs overlap with 43 genes. Three of these genes (RELN, IRS2, and FOXP1) have a known association with non-CRC digestive cancers and one (RRAS2) has a known association with non-CRC cancer. Our study identified 83 novel, predicted functionally impactful germline variants grouped in three "variant risk clusters" shared in three familiarly associated LS groups (high, intermediate and low risk). This variant characterization study demonstrates that large pedigree investigations provide important evidence supporting the hypothesis that different "variant risk clusters" can convey different mechanisms of risk and oncogenesis of LS-CRC even within the same pedigree.

High-LET-Radiation-Induced Persistent DNA Damage Response Signaling and Gastrointestinal Cancer Development

Ionizing radiation (IR) dose, dose rate, and linear energy transfer (LET) determine cellular DNA damage quality and quantity. High-LET heavy ions are prevalent in the deep space environment and can deposit a much greater fraction of total energy in a shorter distance within a cell, causing extensive DNA damage relative to the same dose of low-LET photon radiation. Based on the DNA damage tolerance of a cell, cellular responses are initiated for recovery, cell death, senescence, or proliferation, which are determined through a concerted action of signaling networks classified as DNA damage response (DDR) signaling. The IR-induced DDR initiates cell cycle arrest to repair damaged DNA. When DNA damage is beyond the cellular repair capacity, the DDR for cell death is initiated. An alternative DDR-associated anti-proliferative pathway is the onset of cellular senescence with persistent cell cycle arrest, which is primarily a defense mechanism against oncogenesis. Ongoing DNA damage accumulation below the cell death threshold but above the senescence threshold, along with persistent SASP signaling after chronic exposure to space radiation, pose an increased risk of tumorigenesis in the proliferative gastrointestinal (GI) epithelium, where a subset of IR-induced senescent cells can acquire a senescence-associated secretory phenotype (SASP) and potentially drive oncogenic signaling in nearby bystander cells. Moreover, DDR alterations could result in both somatic gene mutations as well as activation of the pro-inflammatory, pro-oncogenic SASP signaling known to accelerate adenoma-to-carcinoma progression during radiation-induced GI cancer development. In this review, we describe the complex interplay between persistent DNA damage, DDR, cellular senescence, and SASP-associated pro-inflammatory oncogenic signaling in the context of GI carcinogenesis.

Early-Onset GI Cancers: Rising Trends, Genetic Risks, Novel Strategies, and Special Considerations

Cancers in young adults (commonly described as early-onset [EO] cancer) represent a group of malignancies that have unique and challenging biology and genetic, treatment, social, and psychological implications. Even more concerning is a rising trend of EO cancers in multiple tumor types. Research and investigation in EO cancers will help elucidate mechanisms of carcinogenesis, differences in biology and response to treatment, and the need for multidisciplinary care to ensure comprehensive treatment and support for young patients.

Germline Cancer Risk Profiles of Patients With Young-Onset Colorectal Cancer: Findings From a Prospective Universal Germline Testing and Telegenetics Program

BACKGROUND

Colorectal cancer is being increasingly diagnosed in people younger than 50 years. An inheritable cancer predisposition has been reported in 22% of the young-onset cases. Assessment of germline risk is critical for personalized cancer care.

OBJECTIVE

The study aimed to implement universal germline cancer risk assessment and testing and to define the germline cancer risk profiles of patients presenting with young-onset disease.

DESIGN

This is a prospective cohort study.

SETTINGS

This study was conducted at a tertiary-referral academic medical center.

PATIENTS

This study included newly diagnosed patients presenting to surgical clinics between September 2019 and February 2021 who were treated on a standardized care pathway including the universal germline risk assessment.

INTERVENTIONS

Patients received educational material on young-onset disease, genetic testing, and insurance coverage followed by genetic counseling (either remotely by telegenetics or in person). Consenting patients were assessed on a 47-gene common hereditary cancer panel.

MAIN OUTCOME MEASURES

The primary outcome was a proportion of patients with identifiable germline cancer predisposition.

RESULTS

Among 500 patients with colorectal cancer, 185 (37%) were 50 years of age or younger (median: 44). A family history was absent for the majority of patients (123; 67%), and in 15 patients, tumors (8.1%) were deficient in DNA mismatch repair. Germline testing was completed in 130 patients (70%); the remainder were pending (7%), deceased (1%), or declined (22%). Pathogenic germline mutations were identified in 25 of 130 (19%) patients: 12 in mismatch repair genes and 13 in other genes. A variant of uncertain significance was found in 23 (18%) patients. Importantly, a pathogenic germline mutation was identified in 12% of the patients without a family history (versus 32% with; p = 0.015) and in 13% of those with proficient mismatch repair colorectal cancers (versus 71% if deficient; p < 0.001).

LIMITATIONS

The study is limited by its implementation at a single tertiary academic institution.

CONCLUSIONS

One in 5 patients with young-onset disease harbored germline cancer predisposition. This detection rate, coupled with a high level of interest and acceptance from patients and feasibility of implementation, supports universal germline cancer risk assessment in this patient population. See Video Abstract at http://links.lww.com/DCR/B925 .

PERFILES DE RIESGO DE CNCER DE LNEA GERMINAL DE PACIENTES CON CNCER COLORRECTAL DE INICIO JOVEN HALLAZGOS DE UN PROGRAMA UNIVERSAL PROSPECTIVO DE PRUEBAS DE LNEA GERMINAL Y TELEGENTICA

ANTECEDENTES:El cáncer colorrectal se diagnostica cada vez más en personas menores de 50 años. Se ha informado una predisposición hereditaria al cáncer en el 22 % de los casos de aparición temprana. La evaluación del riesgo de la línea germinal es fundamental para la atención personalizada del cáncer.OBJETIVO:Implementar la evaluación y las pruebas universales de riesgo de cáncer de línea germinal, y definir los perfiles de riesgo de cáncer de línea germinal de los pacientes que presentan una enfermedad de aparición temprana.DISEÑO:Un estudio de cohorte prospectivo.AJUSTE:Un centro médico académico de referencia terciaria.PACIENTES:Los pacientes recién diagnosticados que se presentaron en clínicas quirúrgicas entre Septiembre de 2019 y Febrero de 2021 fueron tratados en una vía de atención estandarizada que incluye una evaluación de riesgo de línea germinal universal.INTERVENCIÓN:Los pacientes recibieron material educativo sobre enfermedades de aparición temprana, pruebas genéticas y cobertura de seguro, seguido de asesoramiento genético (ya sea a distancia por telegenética o en persona). Los pacientes que dieron su consentimiento fueron evaluados en un panel de cánceres hereditarios comunes de 47 genes.MEDIDA DE RESULTADO PRINCIPAL:Proporción de pacientes con predisposición identificable al cáncer de línea germinal.RESULTADOS:Entre 500 pacientes con cáncer colorrectal, 185 (37%) tenían 50 años o menos (mediana: 44). No había antecedentes familiares en la mayoría (123, 67%) y 15 tumores (8,1%) eran deficientes en la reparación del desajuste de ácido desoxirribonucleico. La prueba de línea germinal se completó en 130 pacientes (70%); el resto estaban pendientes (7%), fallecidos (1%) o declinados (22%). Se identificaron mutaciones patogénicas de la línea germinal en 25 (de 130, 19%) pacientes: 12 en genes de reparación de errores de emparejamiento y 13 en otros genes. Se encontró una variante de significado incierto en 23 (18%) pacientes. Es importante señalar que se identificó una mutación germinal patogénica en el 12% de los pacientes sin antecedentes familiares (frente al 32% con; p = 0,015) y en el 13% de aquellos con cánceres colorrectales competentes en la reparación de errores de emparejamiento (frente al 71% si eran deficientes; p < 0,001).LIMITACIÓN:Implementado en una sola institución académica terciaria.CONCLUSIÓN:Uno de cada cinco pacientes con enfermedad de inicio joven albergaba predisposición al cáncer de línea germinal. Esta tasa de detección, junto con un alto nivel de interés y aceptación por parte de los pacientes y la viabilidad de la implementación, respaldan la evaluación universal del riesgo de cáncer de línea germinal en esta población de pacientes. Consulte el Video Resumen en http://links.lww.com/DCR/B925 . (Traducción-Dr. Yesenia Rojas-Khalil ).

Delphi Initiative for Early-Onset Colorectal Cancer (DIRECt) International Management Guidelines

BACKGROUND & AIMS

Patients with early-onset colorectal cancer (eoCRC) are managed according to guidelines that are not age-specific. A multidisciplinary international group (DIRECt), composed of 69 experts, was convened to develop the first evidence-based consensus recommendations for eoCRC.

METHODS

After reviewing the published literature, a Delphi methodology was used to draft and respond to clinically relevant questions. Each statement underwent 3 rounds of voting and reached a consensus level of agreement of ≥80%.

RESULTS

The DIRECt group produced 31 statements in 7 areas of interest: diagnosis, risk factors, genetics, pathology-oncology, endoscopy, therapy, and supportive care. There was strong consensus that all individuals younger than 50 should undergo CRC risk stratification and prompt symptom assessment. All newly diagnosed eoCRC patients should receive germline genetic testing, ideally before surgery. On the basis of current evidence, endoscopic, surgical, and oncologic treatment of eoCRC should not differ from later-onset CRC, except for individuals with pathogenic or likely pathogenic germline variants. The evidence on chemotherapy is not sufficient to recommend changes to established therapeutic protocols. Fertility preservation and sexual health are important to address in eoCRC survivors. The DIRECt group highlighted areas with knowledge gaps that should be prioritized in future research efforts, including age at first screening for the general population, use of fecal immunochemical tests, chemotherapy, endoscopic therapy, and post-treatment surveillance for eoCRC patients.

CONCLUSIONS

The DIRECt group produced the first consensus recommendations on eoCRC. All statements should be considered together with the accompanying comments and literature reviews. We highlighted areas where research should be prioritized. These guidelines represent a useful tool for clinicians caring for patients with eoCRC.

Intestinal and extraintestinal neoplasms in patients with NTHL1 tumor syndrome: a systematic review

Germline biallelic pathogenic variants (PVs) in NTHL1 have since 2015 been associated with the autosomal recessive tumor predisposition syndrome: NTHL1 tumor syndrome or NTHL1-associated polyposis. In this systematic review, we aim to systematically investigate the phenotypic and genotypic spectrum of the condition including occurrence of both benign and malignant tumors. The databases PubMed, EMBASE, and Scopus were searched. The search was conducted the 25th of august 2021. We included patients with germline PVs, both heterozygous and homo-/compound heterozygous carriers. Twenty-one papers were selected including 47 patients with biallelic PVs in NTHL1 in 32 families. Twenty-three out of 47 patients (49%) were diagnosed with colorectal cancer (CRC) (mean age: 55, range: 31-73) and 12 out of 22 female patients (55%) were diagnosed with breast cancer (mean age: 49, range: 36-63). Apart from three, all patients who underwent a colonoscopy, had colonic adenomas (93%), and three patients (6%) had duodenal adenomatosis. We also identified 158 heterozygous carriers of germline PVs in NTHL1. Twenty-six out of 68 (38%) heterozygous carriers, who underwent colonoscopy, had colonic polyps or adenomas. Twenty-nine heterozygous carriers (18%) were diagnosed with CRC and 59 (49%) with breast cancer. We observed a high frequency of early onset CRC and breast cancer in patients with NTHL1 tumor syndrome. Subsequently, colorectal, breast, and endometrial cancer screening programs are recommended for NTHL1 biallelic carriers. Trial registry PROSPERO: CRD42021275159.

Fanconi Anemia Pathway in Colorectal Cancer: A Novel Opportunity for Diagnosis, Prognosis and Therapy

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and has the second highest mortality rate globally. Thanks to the advent of next-generation sequencing technologies, several novel candidate genes have been proposed for CRC susceptibility. Germline biallelic mutations in one or more of the 22 currently recognized Fanconi anemia (FA) genes have been associated with Fanconi anemia disease, while germline monoallelic mutations, somatic mutations, or the promoter hypermethylation of some FANC genes increases the risk of cancer development, including CRC. The FA pathway is a substantial part of the DNA damage response system that participates in the repair of DNA inter-strand crosslinks through homologous recombination (HR) and protects genome stability via replication fork stabilization, respectively. Recent studies revealed associations between FA gene/protein tumor expression levels (i.e., FANC genes) and CRC progression and drug resistance. Moreover, the FA pathway represents a potential target in the CRC treatment. In fact, FANC gene characteristics may contribute to chemosensitize tumor cells to DNA crosslinking agents such as oxaliplatin and cisplatin besides exploiting the synthetic lethal approach for selective targeting of tumor cells. Hence, this review summarizes the current knowledge on the function of the FA pathway in DNA repair and genomic integrity with a focus on the FANC genes as potential predisposition factors to CRC. We then introduce recent literature that highlights the importance of FANC genes in CRC as promising prognostic and predictive biomarkers for disease management and treatment. Finally, we represent a brief overview of the current knowledge around the FANC genes as synthetic lethal therapeutic targets for precision cancer medicine.