Young age and a positive family history of colorectal cancer are complementary selection criteria for the identification of Lynch syndrome

An online self-test added to colorectal cancer screening can increase the effectiveness of familial cancer risk assessment without increasing distress

AIM

Most people who are at increased familial colorectal cancer (FCRC) risk are not identified, despite the need for enhanced surveillance colonoscopy for effective CRC prevention. An online self-test may enhance this identification. We assessed whether taking an online self-test to identify increased FCRC risk increases anxiety, distress or CRC risk perception in population-based CRC screening.

METHOD

After the precolonoscopy consultation, patients who had a positive immunohistochemical occult faecal blood test (iFOBT+) in population-based CRC screening were invited by email to take an online self-test at home which returned details of family history. Anxiety (STAI-DY), distress (HADS) and CRC risk perception were assessed immediately before and after taking the online self-test and 2 weeks later.

RESULTS

Of 250 participants invited, 177 (71%) completed the online self-test and psychological questionnaires and 153 (61%) completed questionnaires 2 weeks later. The median age was 65 years (range 61-75). The FCRC risk was increased in 17 participants (9.6%). Of these, 12 (6.8%) had a highly increased FCRC risk and may benefit from germline genetic testing for Lynch syndrome. In 7 of 17 participants (40%) the self-test obtained novel information on family history. Anxiety and distress levels were, and remained, below a clinically relevant level. Perception of CRC risk remained unchanged. Most participants (83%) would recommend the online self-test to others.

CONCLUSION

Of those with a iFOBT+, 9.6% had a previously unidentified increasedFCRC risk and require an enhanced surveillance colonoscopy instead of iFOBT. As screening for this risk did not increase anxiety or distress, and was highly acceptable, we recommend adding the online self-test to population-based CRC screening.

Cancer prevention by aspirin in children with Constitutional Mismatch Repair Deficiency (CMMRD)

Constitutional MisMatch Repair Deficiency (CMMRD) is caused by homozygous or compound heterozygous germline variants in one of the mismatch repair (MMR) genes (MSH2, MSH6, PMS2, MLH1). This syndrome results in early onset colorectal cancer, leukemia and lymphoma, brain tumors and other malignancies. Children with CMMRD are at high risk of developing multiple cancers and cancer surveillance does not guarantee detection of cancer at a curable stage. The development of a preventive treatment strategy would be a major step forward. Long-term daily use of acetylsalicylic acid (ASA) has been shown to reduce cancer risk in individuals with Lynch syndrome (LS). LS is caused by heterozygous germline variants of MSH2, MSH6, PMS2 and MLH1 and characterized by an increased risk of developing colorectal and endometrial cancer at adult age. Here we discuss the potential use of ASA for cancer prevention in patients with CMMRD.

Opportunities for immunotherapy in microsatellite instable colorectal cancer

Microsatellite instability (MSI), the somatic accumulation of length variations in repetitive DNA sequences called microsatellites, is frequently observed in both hereditary and sporadic colorectal cancer (CRC). It has been established that defects in the DNA mismatch repair (MMR) pathway underlie the development of MSI in CRC. After the inactivation of the DNA MMR pathway, misincorporations, insertions and deletions introduced by DNA polymerase slippage are not properly recognized and corrected. Specific genomic regions, including microsatellites, are more prone for DNA polymerase slippage and, therefore, more susceptible for the introduction of these mutations if the DNA MMR capacity is lost. Some of these susceptible genomic regions are located within the coding regions of genes. Insertions and deletions in these regions may alter their reading frame, potentially resulting in the transcription and translation of frameshift peptides with c-terminally altered amino acid sequences. These frameshift peptides are called neoantigens and are highly immunogenic, which explains the enhanced immunogenicity of MSI CRC. Neoantigens contribute to increased infiltration of tumor tissue with activated neoantigen-specific cytotoxic T lymphocytes, a hallmark of MSI tumors. Currently, neoantigen-based vaccination is being studied in a clinical trial for Lynch syndrome and in a trial for sporadic MSI CRC of advanced stage. In this Focussed Research Review, we summarize current knowledge on molecular mechanisms and address immunological features of tumors with MSI. Finally, we describe their implications for immunotherapeutic approaches and provide an outlook on next-generation immunotherapy involving neoantigens and combinatorial therapies in the setting of MSI CRC.

Long anticipation complicates identifying Lynch syndrome in monozygotic twins

Anticipation is a term used to express an earlier age of disease onset in successive generations. Patients with Lynch syndrome (LS) harbor mutations in MMR genes that appear to be associated with the phenomenon where disease is diagnosed 5–12 years earlier in mutation carrying children compared with their affected parent. This has the potential to complicate the recognition of LS as defined by the Amsterdam criteria (or iterations of it) in young probands affected by colorectal cancer. In this report, we describe a case of an LS family with an MLH1 mutation (c.1748 del T). The phenomenon of anticipation was observed in the son of a monozygotic twin who developed two colon cancers that were diagnosed at an age 20 years earlier than the first diagnosis of cancer in his mother. Both the mother and her twin went on to simultaneously develop a rectal carcinoma.

Fourfold increased detection of Lynch syndrome by raising age limit for tumour genetic testing from 50 to 70 years is cost-effective

BACKGROUND

Recognising colorectal cancer (CRC) patients with Lynch syndrome (LS) can increase life expectancy of these patients and their close relatives. To improve identification of this under-diagnosed disease, experts suggested raising the age limit for CRC tumour genetic testing from 50 to 70 years. The present study evaluates the efficacy and cost-effectiveness of this strategy.

METHODS

Probabilistic efficacy and cost-effectiveness analyses were carried out comparing tumour genetic testing of CRC diagnosed at age 70 or below (experimental strategy) versus CRC diagnosed at age 50 or below (current practice). The proportions of LS patients identified and cost-effectiveness including cascade screening of relatives, were calculated by decision analytic models based on real-life data.

RESULTS

Using the experimental strategy, four times more LS patients can be identified among CRC patients when compared with current practice. Both the costs to detect one LS patient (€9437/carrier versus €4837/carrier), and the number needed to test for detecting one LS patient (42 versus 19) doubled. When family cascade screening was included, the experimental strategy was found to be highly cost-effective according to Dutch standards, resulting in an overall ratio of €2703 per extra life-year gained in additionally tested patients.

CONCLUSION

Testing all CRC tumours diagnosed at or below age 70 for LS is cost-effective. Implementation is important as relatives from the large number of LS patients that are missed by current practice, can benefit from life-saving surveillance.

Efficient and reproducible identification of mismatch repair deficient colon cancer: validation of the MMR index and comparison with other predictive models

Background

The identification of mismatch-repair (MMR) defective colon cancer is clinically relevant for diagnostic, prognostic and potentially also for treatment predictive purposes. Preselection of tumors for MMR analysis can be obtained with predictive models, which need to demonstrate ease of application and favorable reproducibility.

Methods

We validated the MMR index for the identification of prognostically favorable MMR deficient colon cancers and compared performance to 5 other prediction models. In total, 474 colon cancers diagnosed ≥ age 50 were evaluated with correlation between clinicopathologic variables and immunohistochemical MMR protein expression.

Results

Female sex, age ≥60 years, proximal tumor location, expanding growth pattern, lack of dirty necrosis, mucinous differentiation and presence of tumor-infiltrating lymphocytes significantly correlated with MMR deficiency. Presence of at least 4 of the MMR index factors identified MMR deficient tumors with 93% sensitivity and 76% specificity and showed favorable reproducibility with a kappa value of 0.88. The MMR index also performed favorably when compared to 5 other predictive models.

Conclusions

The MMR index is easy to apply and efficiently identifies MMR defective colon cancers with high sensitivity and specificity. The model shows stable performance with low inter-observer variability and favorable performance when compared to other MMR predictive models.

An Escherichia coli effector protein promotes host mutation via depletion of DNA mismatch repair proteins

Enteropathogenic Escherichia coli (EPEC) is an attaching and effacing (A/E) human pathogen that causes diarrhea during acute infection, and it can also sustain asymptomatic colonization. A/E E. coli depletes host cell DNA mismatch repair (MMR) proteins in colonic cell lines and has been detected in colorectal cancer (CRC) patients. However, until now, a direct link between infection and host mutagenesis has not been fully demonstrated. Here we show that the EPEC-secreted effector protein EspF is critical for complete EPEC-induced depletion of MMR proteins. The mechanism of EspF activity on MMR protein was posttranscriptional and dependent on EspF mitochondrial targeting. EPEC infection also induced EspF-independent elevation of host reactive oxygen species levels. Moreover, EPEC infection significantly increased spontaneous mutation frequency in host cells, and this effect was dependent on mitochondrially targeted EspF. Taken together, these results support the hypothesis that A/E E. coli can promote colorectal carcinogenesis in humans.

There is mounting evidence linking the gut microbiota with the induction of colorectal tumorigenesis. We previously described the downregulation of host cell mismatch repair (MMR) protein levels upon enteropathogenic Escherichia coli (EPEC) infection and speculated that this depletion may lead to an ablated DNA repair system. In this work, we identify EspF, a translocated EPEC effector protein, as one of the factors required for this phenotype and show that this effector protein must be targeted to the mitochondria in order to exert its effect. Furthermore, we found that the impaired mismatch repair system resulting from EPEC infection led to the generation of spontaneous mutations within host DNA at a site of microsatellite instability, a trait typical of colorectal tumors. Thus, this work provides a novel means by which enteric bacteria may promote colorectal carcinogenesis.

An Escherichia coli effector protein promotes host mutation via depletion of DNA mismatch repair proteins

Enteropathogenic Escherichia coli (EPEC) is an attaching and effacing (A/E) human pathogen that causes diarrhea during acute infection, and it can also sustain asymptomatic colonization. A/E E. coli depletes host cell DNA mismatch repair (MMR) proteins in colonic cell lines and has been detected in colorectal cancer (CRC) patients. However, until now, a direct link between infection and host mutagenesis has not been fully demonstrated. Here we show that the EPEC-secreted effector protein EspF is critical for complete EPEC-induced depletion of MMR proteins. The mechanism of EspF activity on MMR protein was posttranscriptional and dependent on EspF mitochondrial targeting. EPEC infection also induced EspF-independent elevation of host reactive oxygen species levels. Moreover, EPEC infection significantly increased spontaneous mutation frequency in host cells, and this effect was dependent on mitochondrially targeted EspF. Taken together, these results support the hypothesis that A/E E. coli can promote colorectal carcinogenesis in humans.

Acceptance of genetic counseling and testing in a hospital-based series of patients with gynecological cancer

Referral of patients with endometrial (EC) and/or ovarian cancer (OC) for genetic counseling is based on age at diagnosis and family history. Many patients with hereditary cancers are missed by following this strategy. We determined acceptance and mutation detection rate of offering genetic counseling and testing to unselected EC and OC patients. Therefore, in 2007, EC and OC patients were invited for genetic counseling and testing. Patients were asked for their reasons to accept or decline. Nineteen out of fifty-two EC patients (36 %) and twenty-two out of thirty-five OC patients (63 %) accepted genetic counseling, mainly to receive risk assessment for themselves and relatives. Counseling was declined mainly because patients did not want more tests or had no relatives for whom it was relevant. Eighteen out of nineteen EC patients (95 %) and twenty out of twenty-two OC patients (91 %) underwent genetic testing. One EC patient carried an MSH6 mutation (mutation detection rate: 6 %). BRCA1/2 mutations were found in two out of twenty OC patients (10 %). Eleven patients (29 %) received surveillance recommendations for themselves and their relatives. Finally, family history recorded by the gynecologist was compared to that taken by the clinical geneticist. Gynecologists reported family history in ten out of forty-one participants (24 %). In conclusion, genetic counseling and testing are acceptable to patients with OC and/or EC. The 10 % BRCA1/2 mutation detection rate and underreporting of family history by gynecologists warrant referral for genetic counseling for all OC patients, followed by BRCA1/2 testing if indicated. We recommend that microsatellite instability and immunohistochemical analysis be performed in all EC patients, followed by genetic counseling if appropriate. These strategies will lead to better cancer prevention in gynecological cancer patients and their relatives.

Anticipation in lynch syndrome: where we are where we go

Lynch syndrome (LS) is the most common form of inherited predisposition to develop cancer mainly in the colon and endometrium but also in other organ sites. Germline mutations in DNA mismatch repair (MMR) gene cause the transmission of the syndrome in an autosomal dominant manner. The management of LS patients is complicated by the large variation in age at cancer diagnosis which requires these patients to be enrolled in surveillance protocol starting as early as in their second decade of life. Several environmental and genetic factors have been proposed to explain this phenotypic heterogeneity, but the molecular mechanisms remain unknown. Although the presence of genetic anticipation in Lynch syndrome has been suspected since 15 years, only recently the phenomenon has been increasingly reported to be present in different cancer genetic syndromes including LS. While the biological basis of earlier cancer onset in successive generations remains poorly known, recent findings point to telomere dynamics as a mechanism significantly contributing to genetic anticipation in Lynch syndrome and in other familial cancers. In this review, we summarize the clinical and molecular features of Lynch syndrome, with a particular focus on the latest studies that have investigated the molecular mechanisms of genetic anticipation.