The biochemical basis of microsatellite instability and abnormal immunohistochemistry and clinical behavior in Lynch syndrome: from bench to bedside

All three MutL complexes are required for repeat expansion in a human stem cell model of CAG-repeat expansion mediated glutaminase deficiency

The Repeat Expansion Diseases (REDs) arise from the expansion of a disease-specific short tandem repeat (STR). Different REDs differ with respect to the repeat involved, the cells that are most expansion prone and the extent of expansion. Furthermore, whether these diseases share a common expansion mechanism is unclear. To date, expansion has only been studied in a limited number of REDs. Here we report the first studies of the expansion mechanism in induced pluripotent stem cells derived from a patient with a form of the glutaminase deficiency disorder known as Global Developmental Delay, Progressive Ataxia, And Elevated Glutamine (GDPAG; OMIM# 618412) caused by the expansion of a CAG-STR in the 5' UTR of the glutaminase (GLS) gene. We show that alleles with as few as ~ 120 repeats show detectable expansions in culture despite relatively low levels of R-loops formed at this locus. Additionally, using a CRISPR-Cas9 knockout approach we show that PMS2 and MLH3, the constituents of MutLα and MutLγ, the 2 mammalian MutL complexes known to be involved in mismatch repair (MMR), are essential for expansion. Furthermore, PMS1, a component of a less well understood MutL complex, MutLβ, is also important, if not essential, for repeat expansion in these cells. Our results provide insights into the factors important for expansion and lend weight to the idea that, despite some differences, the same mechanism is responsible for expansion in many, if not all, REDs.

Multiple Protein Biomarkers and Different Treatment Strategies for Colorectal Carcinoma: A Comprehensive Prospective

In this review, we emphasized important biomarkers, pathogenesis, and newly developed therapeutic approaches in the treatment of colorectal cancer (CRC). This includes a complete description of small-molecule inhibitors, phytopharmaceuticals with antiproliferative potential, monoclonal antibodies for targeted therapy, vaccinations as immunotherapeutic agents, and many innovative strategies to intervene in the interaction of oncogenic proteins. Many factors combine to determine the clinical behavior of colorectal cancer and it is still difficult to comprehend the molecular causes of a person's vulnerability to CRC. It is also challenging to identify the causes of the tumor's onset, progression, and responsiveness or resistance to antitumor treatment. Current recommendations for targeted medications are being updated by guidelines throughout the world in light of the growing number of high-quality clinical studies. So, being concerned about the aforementioned aspects, we have tried to present a summarized pathogenic view, including a brief description of biomarkers and an update of compounds with their underlying mechanisms that are currently under various stages of clinical testing. This will help to identify gaps or shortfalls that can be addressed in upcoming colorectal cancer research.

The Role of the AT-Rich Interaction Domain 1A Gene (ARID1A) in Human Carcinogenesis

The switch/sucrose non-fermentable (SWI/SNF) (SWI/SNF) complex uses energy from ATP hydrolysis to mobilise nucleosomes on chromatin. Components of SWI/SNF are mutated in 20% of all human cancers, of which mutations in AT-rich binding domain protein 1A (ARID1A) are the most common. ARID1A is mutated in nearly half of ovarian clear cell carcinoma and around one-third of endometrial and ovarian carcinomas of the endometrioid type. This review will examine in detail the molecular functions of ARID1A, including its role in cell cycle control, enhancer regulation, and the prevention of telomerase activity. ARID1A has key roles in the maintenance of genomic integrity, including DNA double-stranded break repair, DNA decatenation, integrity of the cohesin complex, and reduction in replication stress, and is also involved in mismatch repair. The role of ARID1A loss in the pathogenesis of some of the most common human cancers is discussed, with a particular emphasis on gynaecological cancers. Finally, several promising synthetic lethal strategies, which exploit the specific vulnerabilities of ARID1A-deficient cancer cells, are briefly mentioned.

In person and virtual process mapping experiences to capture and explore variability in clinical practice: application to genetic referral pathways across seven Australian hospital networks

Genetic referral for Lynch syndrome (LS) exemplifies complex clinical pathways. Identifying target behaviours (TBs) for change and associated barriers requires structured group consultation activities with busy clinicians - consolidating implementation activities whilst retaining rigour is crucial. This study aimed to: i) use process mapping to gain in-depth understandings of site-specific LS testing and referral practices in Australian hospitals and support identification of TBs for change, ii) explore if barriers to identified TBs could be identified through process mapping focus-group data, and iii) demonstrate pandemic-induced transition from in-person to virtual group interactive process mapping methods. LS clinical stakeholders attended interactive in-person or virtual focus groups to develop site-specific "process maps" visually representing referral pathways. Content analysis of transcriptions informed site-specific process maps, then clinical audit data was compared to highlight TBs for change. TBs were reviewed in follow-up focus groups. Secondary thematic analysis explored barriers to identified TBs, coded against the Theoretical Domains Framework (TDF). The transition from in-person to pandemic-induced virtual group interactive process mapping methods was documented. Process mapping highlighted six key areas of clinical practice variation across sites and site-specific TBs for change were identified. Key barriers to identified TBs emerged, categorised to seven TDF domains. Process mapping revealed variations in clinical practices surrounding LS referral between sites. Incorporating qualitative perspectives enhances process mapping by facilitating identification of TBs for change and barriers, providing a pathway to developing targeted interventions. Virtual process mapping activities produced detailed data and enabled comprehensive map development.

EMAST Type of Microsatellite Instability-A Distinct Entity or Blurred Overlap between Stable and MSI Tumors

Microsatellite instability (MSI) represents an accumulation of frameshifts in short tandem repeats, microsatellites, across the genome due to defective DNA mismatch repair (dMMR). MSI has been associated with distinct clinical, histological, and molecular features of tumors and has proven its prognostic and therapeutic value in different types of cancer. Recently, another type of microsatellite instability named elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) has been reported across many different tumors. EMAST tumors have been associated with chronic inflammation, higher tumor stage, and poor prognosis. Nevertheless, the clinical significance of EMAST and its relation to MSI remains unclear. It has been proposed that EMAST arises as a result of isolated MSH3 dysfunction or as a secondary event in MSI tumors. Even though previous studies have associated EMAST with MSI-low phenotype in tumors, recent studies show a certain degree of overlap between EMAST and MSI-high tumors. However, even in stable tumors, (MSS) frameshifts in microsatellites can be detected as a purely stochastic event, raising the question of whether EMAST truly represents a distinct type of microsatellite instability. Moreover, a significant fraction of patients with MSI tumors do not respond to immunotherapy and it can be speculated that in these tumors, EMAST might act as a modifying factor.

Constitutional Mismatch Repair Deficiency (CMMRD) Syndrome: A Case Report of a Patient With Multiple Metachronous Malignancies

Defective repair of DNA when heterozygous leads to Lynch syndrome (LS) which is inherited in an autosomal dominant fashion. When homozygous, defective repair of DNA leads to constitutional mismatch repair deficiency syndrome (CMMRD), inherited in an autosomal recessive fashion with a predisposition to develop a pattern of childhood malignancies including hematological and solid cancers. We report such a case of a 21-year-old male who developed anaplastic astrocytoma, Burkitt lymphoma, osteochondroma, and colon cancer successively. Each cancer was treated successfully except for colon cancer which developed liver metastasis after the initial treatment with curative intent. However, the patient has been treated for liver metastasis with curative intent and is currently on follow-up. This case report highlights the importance of maintaining a low threshold for investigating CMMRD and other potential cancer predisposition syndromes when a patient presents with multiple cancers in the early years of their life.

Microsatellite instability in pancreatic and ampullary carcinomas: histology, molecular pathology, and clinical implications

Microsatellite instability (MSI)/defective DNA mismatch repair (dMMR) represents an important molecular alteration with diagnostic, prognostic, and predictive value. The increasing interest toward this genetic alteration is given to the high response rate of MSI/dMMR tumors to immunotherapy. There are different cancers in the periampullary region that can harbor MSI/dMMR, and significant morphological-molecular correlates should be acknowledged in this district: (1) pancreatic ductal adenocarcinoma (PDAC): in this tumor category, the prevalence of MSI/dMMR is about 1-2%, and medullary and colloid variants are the most typically involved; (2) ampullary adenocarcinoma: here the prevalence of MSI/dMMR is up to 18%, and in this neoplastic group, MSI/dMMR is more commonly found in the intestinal subtype; (3) pancreatic acinar cell carcinoma: here the prevalence of MSI/dMMR is up to 14%; and (4) pancreatic and ampullary neuroendocrine carcinoma: in this tumor category, the prevalence of MSI/dMMR is up to 5-8%, and this molecular alteration should be assessed also in cases of mixed neuroendocrine-non-neuroendocrine neoplasms. Given the clinical importance of MSI/dMMR and its not-negligible prevalence among the different carcinomas arising in this district, its assessment should become part of the routine diagnostic workflow at least for the most typical histotypes. The test of choice is represented by immunohistochemistry for PDAC and ampullary carcinomas, and by direct molecular analyses including MSI-based polymerase chain reaction and next-generation sequencing for acinar cell and neuroendocrine carcinomas.

Concurrent loss of MLH1, PMS2 and MSH6 immunoexpression in digestive system cancers indicating a widespread dysregulation in DNA repair processes

Immunohistochemical analysis of mismatch repair (MMR) protein expression is widely used to identify tumors with a deficient MMR (dMMR). MMR proteins (MLH1/PMS2 and MSH2/MSH6) work as functional heterodimers, which usually leads to the loss of expression in only one functional MMR heterodimer. Recently, there have been studies showing the simultaneous loss of immunoexpression in proteins of both heterodimers. Yet, this phenomenon has been rarely investigated. In this study, we retrospectively considered cases of different digestive system cancers (gastric cancer, ampullary cancer, small bowel cancer, colorectal cancer), which were immunohistochemically tested for dMMR within a 4-year period at our university hospital (n=352). Of the 103 cases showing dMMR, 5 cases (1.4% of all, 5.1% of dMMR cases) showed a concurrent loss of MLH1, PMS2 and MSH6 immunoexpression, whereas in the other 98 dMMR cases only one MMR heterodimer was affected. MLH1^-/PMS2^-/MSH6^- cancer cases almost arose throughout the entire digestive tract: from the gastric antrum to the left colic flexur. To provide a comprehensive molecular characterization of this MLH1^-/PMS2^-/MSH6^- immunophenotype, tumors were analyzed for microsatellite instability, MLH1 promotor hypermethylation and BRAF exon 15 status. Furthermore, we performed next-generation sequencing focusing on genes related to DNA repair. Here, we could detect pathogenic germline variants as well as multiple sporadic mutations in different genes involved in MMR and homologous recombination repair (HRR) respectively. The affected MMR/HRR-related genes were: ATM, BARD1, BRCA1, CDK12, CHEK1, CHEK2, FANCA, MLH1, MSH6, PALB2, TP53. Considering the biologic function of HRR/MMR proteins as potential drug targets and the low frequency of most of these mutations in digestive system cancers in general, their common occurrence in our MLH1^-/PMS2^-/MSH6^- cases seems to be even more noteworthy, highlighting the need for recognition, awareness and further investigation of this unusual IHC staining pattern.

Microsatellite instability and oncological outcomes in Thai patients with endometrial cancer

Here, we determined the frequency of microsatellite instability (MSI) and the impact of MSI-high (MSI-H) on clinical outcomes of Thai patients with endometrial cancer (EC). Tissue samples of 110 Thai patients with EC, who had undergone surgical staging, were tested for mismatch repair (MMR) gene deficiency, and the patients were grouped into MSI-H and MSI-stable (MSI-S) groups; 24.5% had MSI-H. Unlike MSI-S group patients, MSI-H group patients had synchronous and metachronous cancer. They showed better 3-year disease-free survival (DFS) than those in the MSI-S group (p=.182; 92.3% vs. 82.6%). The 3-year overall survival was 96.2% in MSI-H and 86.4% in MSI-S groups (p=.163). Multivariate analyses showed lower uterine involvement (p=.004), myometrial invasion ≥50% (p=.032), lymphovascular space invasion (p<.001) and MSI-S (p=.006) as prognostic factors for DFS. Our study showed that the prevalence of MMR gene deficiency in Thai patients with EC is common and associated with better outcomes.Impact StatementWhat is already known on this subject? Microsatellite instability (MSI) occurs in approximately 20-40% of endometrial cancer (EC) cases. MSI analysis in EC can identify patients at higher risk of hereditary nonpolyposis colorectal cancer and those having prognostic factors. Additionally, it is predictive of immune checkpoint inhibitor treatment. However, current evidence shows a correlation between clinicopathological characteristics and EC prognosis. Studies on EC and MSI status effect on survival outcome have yielded inconsistent results regarding the pathological significance of MSI in such malignancies.What do the results of this study add? The prevalence of mismatch repair (MMR) gene deficiency in Thai patients with EC is common (24.5%) and associated with better outcomes.What are the implications of these findings for clinical practice and/or further research? This study highlights the prevalence and impact of MSI on oncological outcomes in patients with EC in a low-incidence country. Future studies should focus on the detection of germline mutation to understand the accurate prevalence of Lynch syndrome in Thai patients with EC.

Prevalence of DNA Mismatch Repair Deficiency in Endometrial Cancer Using Immunohistochemistry

Background: Endometrial cancer (EC) is known as the most common malignancy of the female reproductive system, suggested to be associated with hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome (LS). Objectives: Therefore, the aim of the present study was to screen for LS in patients with EC using immunohistochemistry (IHC). Methods: In this retrospective cross-sectional study, the patients with EC, referred to Qaem Hospital, Mashhad, Iran, from 2015 - 2019, were enrolled. Paraffin-embedded tissue blocks were then examined via IHC for the expression of four mismatch repair (MMR) proteins, including MLH1, MSH2, MSH6, and PMS2. The demographic and tumor-related data were also extracted from medical records and pathology reports. The data were consequently analyzed at the significance level of P < 0.05. Results: A total number of 100 patients with EC were evaluated using IHC, and 12 (12%) cases were found suspected. As well, no significant relationship was observed between LS and age, tumor site, tumor histology, tumor size, tumor grade, tumor-infiltrating lymphocytes (TILs), and a family/personal history of malignancies. Conclusions: The prevalence of LS based on the IHC expression of the MMR proteins (MLH1, MSH2, MSH6, and PMS2) was 12% in the patients with EC. There was also no significant relationship between the cases suspected and the demographic and tumor-related data.

Proteomic and functional characterization of intra-tumor heterogeneity in human endometrial cancer

Endometrial cancer is one of the most frequently diagnosed gynecological cancers worldwide, and its prevalence has increased by more than 50% over the last two decades. Despite the understanding of the major signaling pathways driving the growth and metastasis of endometrial cancer, clinical trials targeting these signals have reported poor outcomes. The heterogeneous nature of endometrial cancer is suspected to be one of the key reasons for the failure of targeted therapies. In this study, we perform a sequential window acquisition of all theoretical fragment ion spectra (SWATH)-based comparative proteomic analysis of 63 tumor biopsies collected from 20 patients and define differences in protein signature in multiple regions of the same tumor. We develop organoids from multiple biopsies collected from the same tumor and show that organoids capture heterogeneity in endometrial cancer growth. Overall, using quantitative proteomics and patient-derived organoids, we define the heterogeneous nature of endometrial cancer within a patient’s tumor.

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Proteomic analysis of endometrial cancer intra-tumor heterogeneity

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Identification of potential biomarkers of tumor volume and invasion

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Protein signatures correlate with pre-and postmenopausal cancers

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Patient-derived organoids capture endometrial cancer heterogeneity

Clinicopathologic significance of DNA mismatch repair protein status in endometrial cancer

OBJECTIVE

The prognostic implications of DNA mismatch repair protein (MMRP) have not been determined in endometrial cancer. Therefore, in this study, we aimed to evaluate the clinicopathologic characteristics of DNA MMRP deficiency in endometrial cancer.

MATERIALS AND METHODS

We examined the MMRP status of 206 patients with endometrial carcinomas, using immunohistochemistry, and analyzed their clinicopathologic factors and survival outcomes stratified by MMRP status using the Kaplan-Meier method and Cox regression analysis.

RESULTS

Forty-three cases were deficient for at least one MMRP (20.9%). Loss of MLH1 was the most common (13.1%), followed by MSH6 (7.8%). MMRP deficiency was significantly associated with lympho-vascular space invasion, deep myometrial invasion, and adjuvant treatment (P = 0.032, 0.041, and 0.047, respectively). MMRP-deficient patients had a better overall survival (OS), particularly at advanced cancer stages (III/IV) (100% vs. 73.7%, P = 0.170) or if they had received adjuvant treatment (100% vs. 86.7%, P = 0.087).

CONCLUSION

Although MMRP deficiency was associated with unfavorable prognostic risk factors in endometrial cancer, we found a trend in favor of OS in MMRP-deficient patients. More studies are needed to confirm its prognostic implication.

Immunopeptidomic analyses of colorectal cancers with and without microsatellite instability

Colorectal cancer is the second leading cause of cancer death worldwide, and the incidence of this disease is expected to increase as global socioeconomic changes occur. Immune checkpoint inhibition therapy is effective in treating a minority of colorectal cancer tumors; however, microsatellite stable tumors do not respond well to this treatment. Emerging cancer immunotherapeutic strategies aim to activate a cytotoxic T cell response against tumor-specific antigens, presented exclusively at the cell surface of cancer cells. These antigens are rare and are most effectively identified with a mass spectrometry-based approach, which allows the direct sampling and sequencing of these peptides. Although the few tumor-specific antigens identified to date are derived from coding regions of the genome, recent findings indicate that a large proportion of tumor-specific antigens originate from allegedly noncoding regions. Here, we employed a novel proteogenomic approach to identify tumor antigens in a collection of colorectal cancer-derived cell lines and biopsy samples consisting of matched tumor and normal adjacent tissue. The generation of personalized cancer databases paired with mass spectrometry analyses permitted the identification of more than 30,000 unique MHC I-associated peptides. We identified 19 tumor-specific antigens in both microsatellite stable and unstable tumors, over two-thirds of which were derived from noncoding regions. Many of these peptides were derived from source genes known to be involved in colorectal cancer progression, suggesting that antigens from these genes could have therapeutic potential in a wide range of tumors. These findings could benefit the development of T cell-based vaccines, in which T cells are primed against these antigens to target and eradicate tumors. Such a vaccine could be used in tandem with existing immune checkpoint inhibition therapies, to bridge the gap in treatment efficacy across subtypes of colorectal cancer with varying prognoses. Data are available via ProteomeXchange with identifier PXD028309.

Insertion of an SVA element in MSH2 as a novel cause of Lynch syndrome

Germline mutations in the DNA mismatch repair (MMR) genes cause Lynch syndrome (LS). In this study, we identified and characterized a novel SINE-VNTR-Alu (SVA) insertion in exon 12 of MSH2 in an individual with early-onset colorectal cancer and a very strong LS family history. RT-PCR analysis indicated a larger aberrant MSH2 transcript in one of the family members. MSK-IMPACT next-generation sequencing and long-range PCR analyses revealed an insertion in MSH2 exon 12 at the c.1972 position in an antisense orientation. The insertion was further characterized as an SVA element approximately 3 kb in length, belonging to the SVA_F1 family of retrotransposons. This variant also segregated with LS related cancers in four affected family members in this family. Based on this evidence, this MSH2 SVA insertion is considered pathogenic.

Effects of a Novel Thiadiazole Derivative with High Anticancer Activity on Cancer Cell Immunogenic Markers: Mismatch Repair System, PD-L1 Expression, and Tumor Mutation Burden

Microsatellite instability (MSI), tumor mutation burden (TMB), and programmed cell death ligand-1 (PD-L1) are particularly known as immunotherapy predictive biomarkers. MSI and TMB are closely related to DNA mismatch repair (MMR) pathway functionality, while the PD-L1 checkpoint mediates cancer cell evasion from immune surveillance via the PD-L1/PD-1 axis. Among all the novel triazolo[3,4-b]thiadiazole derivatives, the compound KA39 emerged as the most potent anticancer agent. In the present study, potential alterations in MSI, TMB, and/or PD-L1 expression upon cell treatment with KA39 are explored. We tested three MMR-deficient (DLD-1, LS174T, and DU-145) and two MMR-proficient (HT-29 and PC-3) human cancer cell lines. Our findings support KA39-induced PD-L1 overexpression in all cancer cell lines, although the most outstanding increase was observed in MMR-proficient HT-29 cells. MSI analysis showed that KA39 affects the MMR system, impairing its recognition or repair activity, particularly in MMR-deficient DLD-1 and DU-145 cells, enhancing oligonucleotide production. There were no remarkable alterations in the TMB between untreated and treated cells, indicating that KA39 does not belong to mutagenic agents. Taking together the significant in vitro anticancer activity with PD-L1 upregulation and MSI increase, KA39 should be investigated further for its implication in chemo-immunotherapy of cancer.

Frequent CTNNB1 or PIK3CA Mutations Occurred in Endometrial Endometrioid Adenocarcinoma With High Levels of Microsatellite Instability and Loss of MSH2/MSH6 Expression

BACKGROUND

DNA mismatch repair (MMR) proteins form 2 heterodimers-MutSα formed by MSH2 and MSH6, and MutLα by MLH1 and PMS2. In endometrial endometrioid adenocarcinomas, cases with MMR protein defect also usually harbor other recurrent genetic mutations of the neoplasm. However, it remains unknown whether defects of the 2 functionally different heterodimers are linked to mutations in different genes. We aimed to study the MMR protein expression, microsatellite instability (MSI), and other common genetic mutations of endometrial endometrioid adenocarcinoma.

MATERIALS AND METHODS

We investigated the MSI status of 107 endometrial endometrioid adenocarcinoma patients. MMR protein expression, and mutation of KRAS, CTNNB1, and PIK3CA were also evaluated by immunohistochemistry and sequencing.

RESULTS

An overall 34.6% (37/107) of endometrial endometrioid adenocarcinomas were MSI-H. All MSI-H tumors exhibited loss of MMR protein expression (loss of MLH1, PMS2, MSH6, and MSH2 was noted in 22, 25, 12, and 7 cases, respectively). CTNNB1, PIK3CA, and KRAS mutation were present in 9, 7, and 7 MSI-H tumors. Compared with patients with loss of PMS2 and/or MLH1 expression, patients with loss of MSH6 and/or MSH2 expression were associated with higher frequencies of CTNNB1 mutation (P=0.036) and PIK3CA mutation (P=0.025).

CONCLUSIONS

In MSI-H endometrial endometrioid adenocarcinomas, different types of MMR protein deficiency indicate different molecular genetic alterations.

Characterization of a germline splice site variant MLH1 c.678-3T>A in a Lynch syndrome family

Germline mutations in the DNA mismatch repair (MMR) genes cause Lynch syndrome. Classification and interpretation of intronic variants, especially those outside the consensus ± 1 ~ 2 splice sites are challenging as it is uncertain whether such variants would affect splicing accuracy and efficiency. The assessment of the pathogenicity of splice site variants in MLH1 is further complicated by the various isoforms due to alternative splicing. In this report, we describe a 42-year-old female with Lynch syndrome who carries a germline variant, MLH1 c.678-3T>A, in the splice acceptor site of intron 8. Functional studies and semiquantitative analysis demonstrated that this variant causes a significant increase in the transcripts with exon 9 or exon 9 and 10 deletions, which presumably leads to premature protein truncation or abnormal protein. In addition, we also observed MSI-H and loss of MLH1 by IHC in patient's tumor tissue. This variant also segregated with Lynch Syndrome related cancers in three affected family members. Based on these evidence, the MLH1 c.678-3T>A variant is considered pathogenic.

The utility of evaluating mismatch repair proteins in endometrial carcinoma: an experience from a tertiary referral centre in North India

Background

Endometrial cancer (EC) is a common gynecological malignancy. Around 25-30% patients have mismatch repair deficiency (MMRd). Lynch syndrome is caused by germline mutations in MMR genes. Lynch-associated tumours have better prognosis, however implications for prognosis and survival is less known. Microsatellite insufficiency (MSI) is associated with high neoantigen loads and number of tumor infiltrating lymphocytes, which overexpresses PD-1 and PD-L1 and are excellent candidates for PD-1-targeted immunotherapies. In this study, we aim to evaluate the utility of MMR in patients with EC and its clinico-pathological correlation.

Methods

Eighty-two cases of EC which underwent MMR evaluation over a period of five years at our centre were included. Demographics, clinical details including family history, histopathological and immunohistochemical (IHC) parameters were recorded. Tumors with loss-of at least one protein were considered MMR deficient (MMRd) and those with intact expression were MMR proficient (MMRp).

Results

Of 82 cases tested, 27 (33%) were MMRd. Frequencies of IHC MMR loss of expression were: MLH1/PMS2: 17 (21%), MSH6 loss only: 3 (4%), MSH2/MSH6 loss: 3 (4%), PMS2 loss: 2 (2%). In MMRd cases, most common histologic tumor type was endometrioid adenocarcinoma (70%). Loss of expression was significantly (p < 0.001) more frequent in lower uterine segment involvement and positive family history.

Conclusions

MSI plays an important role in the progression of endometrial cancer. Lower uterine segment involvement and positive family history are significant predictor of MMR loss. Routine testing of MMR proteins in endometrial cancer can contribute to screening of Lynch syndrome families and make immunotherapy available as a treatment option.

Molecular Genetics and the Role of Molecularly Targeted Agents in Metastatic Colorectal Carcinoma

BACKGROUND

Colorectal cancer (CRC) is one of the leading causes of mortality and morbidity in the world. It is the third most common malignancy and fourth leading cancer-related deaths worldwide. In the USA, CRC is the third most commonly diagnosed cancer in both men and women. It is caused by genetic components and potential environmental factors such as consumption of processed meat, red meat, animal fats, low fiber intake, and obesity. Despite the utilization of effective screening modalities and guidelines in the USA, a significant number of patients are diagnosed with advanced, metastatic disease at the time of presentation to the physician. Recent advances in the understanding of molecular medicine with subsequent development and incorporation of newer therapeutic agents into current chemotherapeutic regimens have improved outcomes; however, the management of metastatic CRC remains challenging, particularly for the treating oncologists.

METHODS

We conducted a literature search on CRC mainly related to molecular genetics, targeted biologic agents, and published clinical trials. We also searched and reviewed ongoing clinical trials from Clinicaltrials.gov.

RESULTS AND CONCLUSIONS

Alterations in several oncogenes are associated with CRC, among those RAS, BRAF, and HER2 are of current clinical importance. Chemotherapy drugs, along with vascular endothelial growth factor or epidermal growth factor receptor monoclonal antibodies, are proven to be efficient with manageable toxicity profiles in metastatic CRC. Additional researches on Her-2-directed therapy, BRAF-targeted agents, immunotherapeutic, and newer molecularly targeted agents are needed for further improvement in outcome.

Understanding the clinical implication of mismatch repair deficiency in endometrioid endometrial cancer through a prospective study

OBJECTIVES

Findings on impact of mismatch repair deficiency (MMRd) on patient outcomes in endometrial cancer (EC) have been inconsistent to date. The objective of this study was to compare the oncologic outcomes and recurrence patterns between MMRd and MMR-intact (MMRi) endometrioid EC (EEC).

METHODS

Between 2015 and 2018, we prospectively recruited 492 EEC cases from three cancer centers in Ontario, Canada. Tumors were reflexively assessed for MMR protein expression by immunohistochemistry (IHC). Clinicopathological, survival and recurrence patterns were compared between MMRd and MMRi cases.

RESULTS

Of 492 EEC, 348 were MMRi (71%) and 144 were MMRd (29%) with median follow-up of 16.8 months (0-69.6). MMRd tumors tended to be grade 2 or 3 (56% vs. 29%, p < 0.001), with propensity for lymphovascular space invasion (28% vs. 18%, p = 0.024), lymph node involvement (7% vs. 5%, p < 0.001) and received more adjuvant treatment (46% vs. 33%, p = 0.027). This group also had significantly lower 3-year recurrence-free survival (78% vs. 90%, p = 0.014) although there was no difference in OS (p = 0.603). MMRd cases were more likely to recur in retroperitoneal lymph nodes (p = 0.045). Upon subgroup analysis, MLH1 methylated tumors had the worst prognostic features and survival outcomes.

CONCLUSIONS

MLH1 methylated EECs exhibit more aggressive features compared to other MMRd and MMRi EECs. This may indicate an inherent difference in tumor biology, suggesting the importance of individualized management based on EC molecular phenotype.

Lynch syndrome and Muir-Torre phenotype associated with a recurrent variant in the 3'UTR of the MSH6 gene

A MSH6 3'UTR variant (c.*23_26dup) was found in 13 unrelated families consulted for Lynch/Muir-Torre Syndrome. This variant, which is very rare in the genomic databases, was absent in healthy controls and strongly segregated with the disease in the studied pedigrees. All tumors were defective for MSH2/MSH6/MSH3 proteins expression, but only MSH2 somatic pathogenic mutations were found in 5 of the 12 sequenced tumors. Moreover, we had no evidence of MSH6 transcript decrease in carriers, whereas MSH2 transcript was downregulated. Additional evaluations performed in representative carriers, including karyotype, arrayCGH and Linked-Reads whole genome sequencing, failed to evidence any MSH2 germline pathogenic variant. Posterior probability of pathogenicity for MSH6 c.*23_26dup was obtained from a multifactorial analysis incorporating segregation and phenotypic data and resulted >0.999, allowing to classify the variant as pathogenic (InSiGHT Class 5). Carriers shared a common haplotype involving MSH2/MSH6 loci, then a cryptic disease-associated variant, linked with MSH6 c.*23_26dup, cannot be completely excluded. Even if it is not clear whether the MSH6 variant is pathogenic per se or simply a marker of a disease-associated MSH2/MSH6 haplotype, all data collected on patients and pedigrees prompted us to manage the variant as pathogenic and to offer predictive testing within these families.

A Roadmap Toward the Definition of Actionable Tumor-Specific Antigens

The search for tumor-specific antigens (TSAs) has considerably accelerated during the past decade due to the improvement of proteogenomic detection methods. This provides new opportunities for the development of novel antitumoral immunotherapies to mount an efficient T cell response against one or multiple types of tumors. While the identification of mutated antigens originating from coding exons has provided relatively few TSA candidates, the possibility of enlarging the repertoire of targetable TSAs by looking at antigens arising from non-canonical open reading frames opens up interesting avenues for cancer immunotherapy. In this review, we outline the potential sources of TSAs and the mechanisms responsible for their expression strictly in cancer cells. In line with the heterogeneity of cancer, we propose that discrete families of TSAs may be enriched in specific cancer types.

The health and economic impact of implementation strategies for improving detection of hereditary cancer patients—protocol for an in-depth cost-effectiveness evaluation with microsimulation modelling

Background

Patients with Lynch syndrome (an inherited cancer predisposition syndrome) remain largely underdiagnosed despite clinically and cost-effective testing strategies to detect patients. This is largely due to poor referral rates for high-risk patients for consideration of genetic testing. Targeted approaches to improve the implementation of guidelines and thus uptake rates of genetic testing require the use of limited and valuable healthcare resources. Decision makers must carefully balance the potential health impacts of implementation approaches against the associated costs, similar to when assessing the direct impact of health interventions. This protocol outlines the methods used to conduct an economic evaluation of different implementation approaches aimed at improving referral rates of high-risk patients, including estimating implementation approach costs.

Methods

A cluster randomised controlled trial (the Hide and Seek Project, HaSP) is underway to compare two different implementation approaches aimed at improving referral rates, and thus detection, of Lynch syndrome among colorectal cancer patients across eight Australian hospital networks. An in-depth process evaluation is being conducted alongside the trial and includes measures to collect comprehensive data on both implementation and intervention costs. These costs, in addition to HaSP outcome data, will be incorporated as inputs into an existing microsimulation model—Policy1-Lynch—to project the downstream economic and health impacts and determine the more cost-effective implementation approach from the Australian healthcare perspective.

Discussion

The ability to model the impact of different implementation approaches will enable the most efficient way of improving Lynch syndrome detection. The approach used in this study could also be applied to assess other implementation approaches aimed at increasing the uptake of cost-effective health interventions.

Trial registration

ANZCTR, ACTRN12618001072202. Registered on 27 June 2018.

Tumor-Based Genetic Testing and Familial Cancer Risk

As genetic testing on somatic tumor tissue becomes a more routine part of personalized cancer treatment, a growing opportunity arises to identify hereditary germline variants within those results. These germline results can affect future cancer screening for both patients and their family members. Finding this germline information can be complicated as a result of differences between somatic and germline testing processes, nomenclature, and outcome goals (e.g., treatment impact). The goal of this review is to highlight differences between somatic and germline testing and outline a potential guide to allow for appropriate clinical interpretation of somatic testing results in order to better facilitate genetic counseling referrals and confirmatory germline testing.

The missing heritability of familial colorectal cancer

Pinpointing heritability factors is fundamental for the prevention and early detection of cancer. Up to one-quarter of colorectal cancers (CRCs) occur in the context of familial aggregation of this disease, suggesting a strong genetic component. Currently, only less than half of the heritability of CRC can be attributed to hereditary syndromes or common risk loci. Part of the missing heritability of this disease may be explained by the inheritance of elusive high-risk variants, polygenic inheritance, somatic mosaicism, as well as shared environmental factors, among others. A great deal of the missing heritability in CRC is expected to be addressed in the coming years with the increased application of cutting-edge next-generation sequencing technologies, routine multigene panel testing and tumour-focussed germline predisposition screening approaches. On the other hand, it will be important to define the contribution of environmental factors to familial aggregation of CRC incidence. This review provides an overview of the known genetic causes of familial CRC and aims at providing clues that explain the missing heritability of this disease.

Clinicopathological features of 50 mismatch repair (MMR)-deficient endometrial carcinomas, tested by immunohistochemistry: A single institutional feasibility study, India

There are few comprehensive studies from Asia on clinicopathologic features of mismatch repair (MMR)-deficient endometrial carcinomas, including rarely from our country. One hundred and four cases of endometrial carcinomas were tested for four MMR proteins by immunohistochemistry. Among 50 MMR-deficient (MMRd) tumors(48%), age-range was 27-68 years(median = 53) and tumor size(n = 34) varied from 1.2-10 cm(average = 4.6). Lower uterine segment(LUS) was involved in 21/31 cases(67.7%). Histopathologically, all cases were endometrioid adenocarcinomas(EMACs), of FIGO grade 2(low-grade)(18 cases) and 3(high-grade)(32 cases), displaying de-differentiated, undifferentiated and lymphoepithelioma(LE)-like patterns, in 24 cases(48%). Tumor infiltration ≥ half of myometrium was seen in 30/44 cases (68.1%); lymphovascular emboli in 19/43 cases(44.1%); and lymph node metastasis in 7/22(31.8%) cases. Uncommonly, clear cell component(n = 2) and focal neuroendocrine differentiation (n = 2) were observed. Immunohistochemically, tumor cells showed paired loss of MLH1 and PMS2 in 33(66%) and MSH2 and MSH6 in 14(28%) cases, along with loss of MSH2 and PMS2, in two and a single case, respectively. Nine patients(18%) were treated for another cancer and 9/33(27.2%) disclosed familial history of cancer. MSH2 was the most frequently lost MMR protein in those cases. Additionally, tumor cells displayed ER positivity in 41/50 cases(82%), PR in 38/41cases(92.6%) and wild-type p53 staining in 24/28 cases(85.7%). Tumor with LE-pattern showed PDLI immunoexpression. Certain clinicopathologic features suggestive for MMRd associated ECs, such as relatively large-sized tumors, involving LUS; especially high-grade, infiltrative EMACs, with undifferentiated/de-differentiated, and LE-like patterns; showing deep muscle invasion, frequent PR immunoexpression and invariably, wild-type p53 immunostaining can be useful in screening cases of Lynch syndrome. This constitutes the first report on these tumors from our country.

Risk of Metachronous Colorectal Neoplasm after a Segmental Colectomy in Lynch Syndrome Patients According to Mismatch Repair Gene Status

BACKGROUND

Because of increased risk of metachronous colorectal cancer (CRC), all patients with Lynch syndrome (LS) are offered a total colectomy. However, because metachronous CRC rate by mismatch repair (MMR) gene is uncertain, and total colectomy negatively impacts quality of life, it remains unclear whether segmental resection is indicated for lower penetrance MMR genes. We evaluated metachronous CRC incidence according to MMR gene in LS patients who underwent a segmental colectomy.

STUDY DESIGN

Single-center, retrospective cohort study in patients with an earlier colectomy for CRC and an MMR germline mutation in MLH1, MSH2, MSH6, or PMS2 followed prospectively in a hereditary CRC family registry. All patients underwent surveillance colonoscopy. Metachronous CRC was defined as one detected more than 1 year after index resection. Primary end point was cumulative incidence of metachronous CRC overall and by MMR gene.

RESULTS

One hundred and ten patients were included: 35 with MLH1 likely pathogenic/pathogenic (LP/P) variants (32%), 42 MSH2 (38%), 20 MSH6 (18%), and 13 PMS2 (12%). Median follow-up 4.26 years (range 0.53 to 19.92 years). Overall, metachronous CRC developed in 22 patients (20%). At 10-year follow-up, incidence was 12% (95% CI 6% to 23%), with no metachronous CRC detected in patients with a PMS2 or MSH6 LP/P variant.

CONCLUSIONS

After index segmental resection, metachronous CRC is less likely to develop in LS patients with MSH6 or PMS2 LP/P variant than in MLH1 or MSH2 carriers. Our data support segmental resection and long-term colonoscopic surveillance rather than total colectomy in carefully selected, well-informed LS patients with MSH6 or PMS2 LP/P variant.

Lynch syndrome-associated ultra-hypermutated pediatric glioblastoma mimicking a constitutional mismatch repair deficiency syndrome

Pediatric glioblastoma multiforme (GBM) has a poor prognosis as a result of recurrence after treatment of surgery and radiochemotherapy. A small subset of pediatric GBMs presenting with an ultra-high tumor mutational burden (TMB) may be sensitive to immune checkpoint inhibition. Here we report a 16-yr-old male with an ultra-hypermutated GBM. After incomplete surgical resection, molecular analysis of the tumor identified unusually high numbers of mutations and intratumor heterogeneity by a hotspot next-generation sequencing (NGS) panel. Further comprehensive molecular profiling identified a TMB of 343 mutations/Mb. An ultra-hypermutation genotype in pediatric GBMs is suggestive of a constitutive mismatch repair deficiency syndrome (CMMRD), which often acquires additional somatic driver mutations in replicating DNA polymerase genes. Tumor sequencing identified two MSH6 nonsense variants, a hotspot POLE mutation and a mutational signature supportive of a germline MMR deficiency with a somatic POLE mutation. However, constitutional testing identified only one nonsense MSH6 variant consistent with a Lynch syndrome diagnosis. This case represents the first confirmed Lynch syndrome case mimicking CMMRD by manifesting as an ultra-hypermutated pediatric GBM, following somatic mutations in MSH6 and POLE These findings permitted the patient's enrollment in an anti-PD-1 clinical trial for children with ultra-hypermutated GBM. Immunotherapy response has resulted in the patient's stable condition for over more than 1 year postdiagnosis.

Evidence of response to pembrolizumab in a patient with Lynch syndrome-related metastatic colon cancer

Patients with Lynch Syndrome (LS) are at high risk of developing colorectal cancer at an early age. Germline mutations in DNA mismatch repair genes and microsatellite instability are clear signatures of this autosomal dominant disorder. Here, we report the clinical history of a 38-year-old patient with LS-related metastatic colon cancer treated in Chile with immunotherapy (pembrolizumab). The patient exhibited a pathogenic deletion in Epithelial cell Adhesion Molecule (EPCAM) and mutS homolog 2 (MSH2) genes, and after diagnosis received 12 cycles of FOLFOX. The tumor mass, however, continued to grow, and a new metastatic mucinous adenocarcinoma of 13 mm appeared at the level of the 11th right dorsal vertebra. To treat these lesions, the patient received immunotherapy scheme with pembrolizumab (200 mg every 21 days). After only four cycles, the patient’s symptoms improved and the lesions showed less metabolic activity. After 12 cycles with pembrolizumab, the patient started palliative radiation and systemic second-line treatment with FOLFIRI and Avastin. The immunotherapy scheme with pembrolizumab was capable of delaying the second-line treatment for at least 8 months, becoming a useful therapeutic option for this patient. Thus, our study highlights the importance of implementing immunotherapy treatment programs for LS-colorectal cancer patients in South American countries.

Must Peutz-Jeghers syndrome patients have the LKB1/STK11 gene mutation? A case report and review of the literature

Peutz-Jeghers syndrome (PJS) is an autosomal dominant inherited disease, which is characterized by mucocutaneous pigmentation and multiple gastrointestinal hamartoma polyps. The germline mutation of LKB1/STK11 gene on chromosome 19p13.3 is considered to be the hereditary cause of PJS. However, must a patient with PJS have the LKB1/STK11 gene mutation? We here report a case of a male patient who had typical manifestations of PJS and a definite family history, but did not have LKB1/STK11 gene mutation. By means of high-throughput sequencing technology, only mutations in APC gene (c.6662T > C: p.Met2221Thr) and MSH6 gene (c.3488A > T: p.Glu1163Val) were detected. The missense mutations in APC and MSH6 gene may lead to abnormalities in structure and function of their expression products, and may result in the occurrence of PJS. This study suggests that some other genetic disorders may cause PJS besides LKB1/STK11 gene mutation.

Relationship between mismatch repair immunophenotype and long-term survival in patients with resected periampullary adenocarcinoma

Background

Periampullary adenocarcinomas, including pancreatic cancer, are a heterogeneous group of tumors with poor prognosis, where classification into intestinal type (I-type) or pancreatobiliary type (PB-type) is a relevant prognostic factor. The clinical significance of deficient mismatch repair (dMMR) in periampullary adenocarcinoma is comparatively unexplored. Herein, we examined the associations of MMR immunophenotype with long-term survival in patients with resected periampullary adenocarcinoma, with particular reference to morphology and adjuvant treatment response.

Methods

MMR protein expression was assessed by immunohistochemistry on tissue microarrays with primary tumors from a retrospective cohort of 175 patients with periampullary adenocarcinoma treated with pancreaticoduodenectomy during 2001–2011 in Malmö and Lund University Hospitals, Sweden. Cox proportional hazards models were applied to calculate hazard ratios (HR) and 95% confidence intervals (CI).

Results

After a mean follow-up of 46.5 (1.9–185.1) months, 35 patients (20.3%) were alive, 24 with I-type and 11 with PB-type tumors. MMR protein expression could be evaluated in 172 cases, in which dMMR was denoted in 20 (11.6%) cases, 13/63 (20.6%) in I-type and 7/109 (6.4%) in PB-type tumors. dMMR was associated with a significantly prolonged overall survival in the entire cohort (HR = 0.28, 95% CI 0.13–0.57), and in I-type tumors (HR = 0.20, 95% CI 0.06–0.68), however not independent of conventional prognostic factors. In PB-type tumors, dMMR was not prognostic, but there was a significant negative interaction between dMMR and adjuvant treatment (p_interaction = 0.015).

Conclusions

dMMR is more frequent in I-type compared to PB-type periampullary adenocarcinoma, and is a prognostic factor for long-term survival only in the former. The finding of the small number of PB-type tumors with dMMR potentially lacking benefit from adjuvant chemotherapy is however noteworthy and merits further validation.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1444-4) contains supplementary material, which is available to authorized users.

Endometrial cancer risk and survival by tumor MMR status

Objective

The risk of developing endometrial cancer (EC) and/or survival following a diagnosis of EC might differ by tumor DNA mismatch repair (MMR) status. We assessed the association between tumor MMR status (classified as MMR-proficient, somatic MMR-deficient, germline MMR-deficient) and the risk of developing EC and survival following a diagnosis of EC.

Methods

We analyzed data from women who participated in the Australian National Endometrial Cancer Study (ANECS) conducted between 2005 and 2007. Risk analyses (698 cases/691 population controls) utilized sociodemographic and lifestyle information obtained from telephone interviews at recruitment. For survival analyses (728 cases), patients' clinical data was abstracted from medical records, and survival data were obtained via linkage with the Australian National Death Index. We used logistic regression analysis to evaluate the associations between tumor MMR status and EC risk, and proportional hazards models to perform survival analyses with adjustment of known prognostic factors.

Results

Established risk factors for EC did not differ significantly by tumor MMR status. In analyses including all EC subtypes, overall and EC-specific survival did not differ by tumor MMR status. Among women with the most common endometrioid subtype, EC-specific survival was worse for women with somatic MMR-deficient EC compared to women with MMR-proficient EC (hazard ratio [HR]=2.18; 95% confidence interval [CI]=1.19–4.01).

Conclusion

The risk of EC is not associated with MMR status. Accurate separation of germline from somatic causes of MMR deficiency suggests that patients with endometrioid subtype somatic MMR-deficient tumors have poorer EC-specific survival than those with MMR-proficient tumors, after accounting for other prognostic factors.

Hereditary or sporadic polyposis syndromes

Polyposis syndromes are encountered in endoscopy practice, and are considered rare entities, accounting for ≤1% of colorectal cancer. Polyposis can occur within inherited syndromes or as "sporadic" cases of unknown etiology. Their proper characterization is relevant for patient management, and should nowadays drive appropriate genetic tests which have a key role in clinical practice for driving surveillance and colorectal cancer prevention, enlarged to relatives. Polyposis classification is based upon polyp number and histology, familial and personal history. This review will explore the polyposis nosology and their genetic determinants in the emerging scenario of Next Generation Sequencing which allow testing multiples genes in parallel. This capability will likely continue to increase the range of polyposis predisposing genes, contributing to define new clinical entities.

Isolated Loss of PMS2 Immunohistochemical Expression is Frequently Caused by Heterogenous MLH1 Promoter Hypermethylation in Lynch Syndrome Screening for Endometrial Cancer Patients

Lynch syndrome (LS) is an autosomal-dominant inherited disorder mainly caused by a germline mutation in the DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, and PMS2) and is associated with increased risk for various cancers, particularly colorectal cancer and endometrial cancer (EC). Women with LS account for 2% to 6% of EC patients; it is clinically important to identify LS in such individuals for predicting and/or preventing additional LS-associated cancers. PMS2 germline mutation (PMS2-LS) is the rarest contribution to LS etiology among the 4 LS-associated MMR germline mutations, and its detection is complicated. Therefore, prudent screening for PMS2-LS is important as it leads to an efficient LS identification strategy. Immunohistochemistry is recommended as a screening method for LS in EC. Isolated loss of PMS2 (IL-PMS2) expression is caused not only by PMS2-LS but also by MLH1 germline mutation or MLH1 promoter hypermethylation (MLH-PHM). This study aimed to determine the association between MLH1-PHM and IL-PMS2 to avoid inappropriate genetic analysis. We performed MLH1 methylation analysis and MLH1/PMS2 germline mutation testing on the IL-PMS2 cases. By performing MMR-immunohistochemistry on 360 unselected ECs, we could select 8 (2.2%) cases as IL-PMS2. Heterogenous MLH1 staining and MLH1-PHM were detected in 4 of 8 (50%) IL-PMS2 tumors. Of the 5 IL-PMS2 patients who underwent genetic analysis, 1 had PMS2 germline mutation with normal MLH1 expression (without MLH1-PHM), and no MLH1 germline mutation was detected. We suggest that MLH1 promoter methylation analysis for IL-PMS2 EC should be performed to exclude sporadic cases before further PMS2 genetic testing.

Familial Colorectal Cancer Type X in Central Iran: A New Clinicopathologic Description

Background: Familial colorectal cancer type X (FCCX) is a subtype of mismatch repair (MMR)-proficient colorectal cancerin which the patients are clinically at risk for Lynch syndrome (LS), a common hereditary cancer predisposing syndrome. In this study, we described a new clinicopathological feature of the condition in central Iran. Materials and Methods: We designed a descriptive, retrospective study to screenat-risk colorectal cancer (CRC) patients, using Amsterdam II criteria and Molecular analysis in Isfahan (central Iran) throughout 2000-2013 period. Results: 219 early-onset (≤ 50 years) CRC patients of 1659 were selected for the evaluation. Amsterdam II criteria were positive in 45 families; of whom 31 were finally analyzed by molecular testing. MMR deficiency was detected in 7/31 probands (22.6%) as affected to LS, so 24 families (77.4%) were identified as FCCX. The mean age of the probands at diagnosis among FCCX families was 45.3 years (range 24-69) versus 38.0 years (range 31-50) in LS families. The frequency of CRC among FCCX and LS families was calculated 27.9% and 67.5%, respectively. Also, the most frequent extracolonic cancer among both FCCX and LS families was stomach by 25.5% and 30.8%, respectively. Tumor site was proximal to the splenic flexure in 20.8% and 57.1% of index CRC patients in FCCX and LS families, respectively. Conclusion: Given the relative high frequency of FCCX and its different phenotype among Iranian populations, we need to set up more advanced molecular studies for exploration of unknown molecular pathways leading to tumorigenesis in this class of CRC patients.

Risk of metachronous colorectal cancer following colectomy in Lynch syndrome: a systematic review and meta-analysis

AIM

Lynch syndrome (LS) accounts for 2-4% of all colorectal cancer (CRC) cases, and is associated with an increased risk of developing metachronous colorectal cancer (mCRC). The role of extended colectomy in LS CRC is controversial. There are limited studies comparing the risk of mCRC following segmental colectomy and extended colectomy. The objective of this systematic review is to evaluate the risk of developing mCRC following segmental and extended colectomy for LS CRC and endoscopic compliance.

METHOD

A systematic review of major databases was performed using predefined terms. All original articles published in English comparing the risk of mCRC in LS patients after segmental and extended colectomy from 1950 to January 2016 were included.

RESULTS

The search retrieved 324 studies. Six studies involving 871 patients met the inclusion criteria. Of these, 705 (80.9%) underwent segmental colectomy and 166 (19.1%) extended colectomy. Average follow-up was 91.2 months. The mCRC rate was 22.8% and 6% in the segmental and extended colectomy groups, respectively. The segmental group were over four times more likely to develop mCRC (OR 4.02, 95% CI: 2.01-8.04, P < 0.0001). mCRC occurred in patients after segmental colectomy despite 1-2-yearly postoperative endoscopic surveillance.

CONCLUSION

This result suggests that extended colectomy reduces the risk of mCRC by over four-fold compared with segmental colectomy. mCRC occurred in the segmental group despite postoperative endoscopic surveillance. This needs to be borne in mind when deciding on the appropriate surgical management of LS patients with CRC. We recommend that extended colectomy should be considered for patients with confirmed LS CRC.

A case report of Muir-Torre syndrome in a woman with breast cancer and MSI-Low skin squamous cell carcinoma

Background

The tumor spectrum in the Lynch syndrome is well defined, comprising an increased risk of developing colonic and extracolonic malignancies. Muir-Torre syndrome is a variant with a higher risk of skin disease. Patients have been described carrying mutations in the mismatch repair genes and presenting tumors with unusual histology or affected organ not part of the Lynch syndrome spectrum. Hence, the real link between Lynch syndrome, or Muir-Torre syndrome, and these tumors remains difficult to assess.

Case presentation

We present the case of a 45-year-old-woman, diagnosed with breast cancer at 39 years of age and skin squamous cell carcinoma (SCC) at 41 years of age, without personal history of colorectal cancer. The microsatellite instability analysis performed on the skin SCC showed a low-level of microsatellite instability (MSI-Low). The immunohistochemical expression analysis of the four DNA mismatch repair proteins MLH1, MSH2, MSH6 and PMS2 showed a partial loss of the expression of MSH2 and MSH6 proteins. Germline deletion was found in MSH2 gene (c.1277-? _1661 + ?del), exon 8 to 10. Then, at 45 years of age, she presented hyperplastic polyps of the colon and a sebaceous adenoma.

Conclusion

Squamous cell carcinomas have been described in Lynch syndrome and Muir-Torre syndrome in two studies and two case reports. This new case further supports a possible relationship between Lynch syndrome and squamous cell carcinoma.

Neoadjuvant therapy in microsatellite-stable colorectal carcinoma induces concomitant loss of MSH6 and Ki-67 expression

Universal screening using immunohistochemistry for DNA mismatch-repair proteins (MLH1, MSH2, MSH6, and PMS2) is advocated by major professional medical organizations to identify Lynch syndrome-associated colorectal carcinoma. Loss of MSH6 expression independent of MSH2 expression has been reported in microsatellite-stable (MSS) colorectal carcinoma after neoadjuvant therapy. The mechanism remains unclear. We studied the immunohistochemical expression of MSH2, MSH6, and Ki-67 in MSS colorectal carcinoma with (n=50) or without (n=64) preoperative neoadjuvant therapy and Lynch syndrome-associated colorectal carcinoma with confirmed MSH6 germline mutation (n=3). Twelve of 50 MSS colorectal carcinoma postneoadjuvant resections demonstrated reduced MSH6 expression, with loss of expression ranging from 20% to 100% of tumor cells. Eight of 64 MSS colorectal carcinomas without neoadjuvant therapy also exhibited reduced MSH6 expression but to a lesser degree (10%-50% of tumor cells with loss of expression). In both subgroups, concomitant loss of MSH6 and Ki-67 expressions was demonstrated in the same tumor areas in consecutive tissue sections. However, 3 cases of Lynch syndrome-associated colorectal carcinoma due to germline MSH6 mutation revealed complete loss of MSH6 expression with discordant positive Ki-67 staining in the tumor cells. The MSH2-independent, Ki-67-related expression of MSH6 in colorectal carcinoma helps to explain the heterogeneous MSH6 staining in MSS colorectal carcinoma with or without neoadjuvant therapy.

Cytoplasmic MSH2 immunoreactivity in a patient with Lynch syndrome with an EPCAM-MSH2 fusion

AIMS

Immunohistochemistry for mismatch repair (MMR) proteins is being increasingly used to examine MMR status in tumours. The aim of the present article was to report the case of a colon cancer patient with Lynch syndrome who showed unusual cytoplasmic MMR protein localization.

METHODS AND RESULTS

Histologically, the colon cancer was diagnosed as medullary carcinoma associated with prominent tumour-infiltrating lymphocytes and a Crohn's-like reaction. Immunohistochemistry revealed cytoplasmic and nuclear expression of MSH2 in non-neoplastic cells, and exclusively cytoplasmic expression in tumour cells. MSH6 expression was nuclear in non-neoplastic cells, but was lost in tumour cells. Nuclear expression of MLH1 and PMS2 was retained in both non-neoplastic and tumour cells. The tumour was microsatellite instability-high, which is indicative of defective MMR function. A subsequent germline mutation analysis identified a genomic deletion spanning the 3' region of EPCAM and the 5' region of MSH2, resulting in an in-frame fusion of EPCAM and MSH2.

CONCLUSIONS

The unusual cytoplasmic immunoreactivity of MSH2 was considered to be attributable to the non-functional EPCAM-MSH2 fusion product. The present case illustrates that not only loss of expression, but also abnormal localization, of MMR proteins is indicative of a defective MMR system.

Survival Outcome and Risk of Metachronous Colorectal Cancer After Surgery in Lynch Syndrome

BACKGROUND

The survival benefit of extensive colectomy is controversial in Lynch syndrome, and risk factors for metachronous colorectal cancer (CRC) after segmental colectomy are unclear.

OBJECTIVE

The aim of this study was to investigate the survival outcome and risk of metachronous CRC after surgery in Lynch syndrome patients diagnosed with their first CRC.

METHODS

Overall, 106 patients with Lynch syndrome who underwent surgery for CRC were included in the study. The demographics, genotype, clinicopathological characteristics of the index CRC, and follow-up data were reviewed from a single-institution Lynch syndrome database.

RESULTS

Of 30 patients who underwent extensive surgery, no metachronous CRC was developed during a mean follow-up of 68.1 months. Of 76 patients who underwent segmental colectomy, 13 (17.1 %) developed metachronous CRC during a mean follow-up of 77.2 months. The cumulative risk of metachronous CRC was 8.4 % at 5 years and 20.4 % at 10 years after segmental colectomy. No difference in overall and CRC-specific survival was observed between segmental colectomy and extensive colectomy (p = 0.277 and p = 0.659, respectively). A 25 cm or longer resection of bowel decreased the risk of metachronous CRC after segmental colectomy compared with less extensive resection (hazard ratio 0.10, 95 % confidence interval 0.01-0.86). Annual surveillance colonoscopy did not decrease the risk of metachronous CRC compared with less frequent surveillance colonoscopy. Although not statistically significant, none of the MSH6 gene mutation carriers were diagnosed with metachronous CRC.

CONCLUSIONS

Although no survival benefit was identified, surgeons and patients might consider extensive colectomy to prevent metachronous CRC in Lynch syndrome patients regardless of their clinicopathological characteristics.

Molecular analysis of Iranian colorectal cancer patients at risk for Lynch syndrome: a new molecular, clinicopathological feature

PURPOSE

Microsatellite instability (MSI) and mismatch repair (MMR) gene expression present a hallmark mutational signature of Lynch syndrome as a common hereditary cancer predisposing condition. Since there is not enough data of molecular and clinicopathological aspects of the disease in Iranian populations, this article is a new description in Central Iran.

METHODS

It is a descriptive analytical study in which we screened 1659 colorectal cancer (CRC) patients based on early-onset disease and Amsterdam II criteria during 14 years (2000-2013). MSI testing was applied through a commercial kit evaluating five mononucleotide markers (BAT-25, BAT-26, MON0-27, NR-21, and NR-24) using a fluorescent multiplex PCR method. Immunohistochemistry (IHC) staining was set up to detect expression of four mismatch repair (MMR) genes including MLH1, MSH2, MSH6, and PMS2. SPSS 16 software was used to analyze the data.

RESULTS

Overall, 31 of 45 screened at-risk families were eventually included to MSI testing of which 9/31 patients (∼29 %) showed MSI in their tumor tissues including 6 (19.4 %) MSI-H (high). BAT-26 was the most instable marker with instability in 7/31 MSI tumors (22.6 %). IHC-MMR staining was absent in 7/31 probands (22.6 %) of which in 4 cases, both MSH2/MSH6 (57.1 %) and, in 2 cases, both MLH1/PMS2 showed deficiency (28.6 %), and just in one case, MSH6 was defective (14.3 %). IHC-MMR was absent in all 6 MSI-H tumors while none of 3 MSI-L tumors were MMR-deficient. Just single MSH6-defective tumor showed MSS state. The frequency of CRC among MMR-deficient and MMR-proficient families was 67.5 and 27.9 %, respectively. The most common extracolonic cancer among both MMR-deficient and MMR-proficient groups was stomach, respectively, with 26.7 and 16.5 %.

CONCLUSIONS

A different molecular and clinicopathological phenotype of tumors in CRC Iranian patients at risk for Lynch syndrome could suggest some new molecular mechanisms about which more evaluations are necessary.