Germline MBD4 deficiency causes a multi-tumor predisposition syndrome.

We report an autosomal recessive, multi-organ tumor predisposition syndrome, caused by bi-allelic loss-of-function germline variants in the base excision repair (BER) gene MBD4. We identified five individuals with bi-allelic MBD4 variants within four families and these individuals had a personal and/or family history of adenomatous colorectal polyposis, acute myeloid leukemia, and uveal melanoma. MBD4 encodes a glycosylase involved in repair of G:T mismatches resulting from deamination of 5'-methylcytosine. The colorectal adenomas from MBD4-deficient individuals showed a mutator phenotype attributable to mutational signature SBS1, consistent with the function of MBD4. MBD4-deficient polyps harbored somatic mutations in similar driver genes to sporadic colorectal tumors, although AMER1 mutations were more common and KRAS mutations less frequent. Our findings expand the role of BER deficiencies in tumor predisposition. Inclusion of MBD4 in genetic testing for polyposis and multi-tumor phenotypes is warranted to improve disease management.

BRAF V600E is associated with higher incidence of second cancers in adults with Langerhans cell histiocytosis.

In this retrospective study, BRAF mutation status did not correlate with disease extent or (event-free) survival in 156 adults with Langerhans cell histiocytosis. BRAFV600E was associated with an increased incidence of second malignancies, often comprising hematological cancers, which may be clonally related.

Molecular and Clinicopathologic Characterization of Mismatch Repair-Deficient Endometrial Carcinoma Not Related to MLH1 Promoter Hypermethylation.

Universal tumor screening in endometrial carcinoma (EC) is increasingly adopted to identify individuals at risk of Lynch syndrome (LS). These cases involve mismatch repair-deficient (MMRd) EC without MLH1 promoter hypermethylation (PHM). LS is confirmed through the identification of germline MMR pathogenic variants (PV). In cases where these are not detected, emerging evidence highlights the significance of double-somatic MMR gene alterations as a sporadic cause of MMRd, alongside POLE/POLD1 exonuclease domain (EDM) PV leading to secondary MMR PV. Our understanding of the incidence of different MMRd EC origins not related to MLH1-PHM, their associations with clinicopathologic characteristics, and the prognostic implications remains limited. In a combined analysis of the PORTEC-1, -2, and -3 trials (n = 1254), 84 MMRd EC not related to MLH1-PHM were identified that successfully underwent paired tumor-normal tissue next-generation sequencing of the MMR and POLE/POLD1 genes. Among these, 37% were LS associated (LS-MMRd EC), 38% were due to double-somatic hits (DS-MMRd EC), and 25% remained unexplained. LS-MMRd EC exhibited higher rates of MSH6 (52% vs 19%) or PMS2 loss (29% vs 3%) than DS-MMRd EC, and exclusively showed MMR-deficient gland foci. DS-MMRd EC had higher rates of combined MSH2/MSH6 loss (47% vs 16%), loss of >2 MMR proteins (16% vs 3%), and somatic POLE-EDM PV (25% vs 3%) than LS-MMRd EC. Clinicopathologic characteristics, including age at tumor onset and prognosis, did not differ among the various groups. Our study validates the use of paired tumor-normal next-generation sequencing to identify definitive sporadic causes in MMRd EC unrelated to MLH1-PHM. MMR immunohistochemistry and POLE-EDM mutation status can aid in the differentiation between LS-MMRd EC and DS-MMRd EC. These findings emphasize the need for integrating tumor sequencing into LS diagnostics, along with clear interpretation guidelines, to improve clinical management. Although not impacting prognosis, confirmation of DS-MMRd EC may release patients and relatives from burdensome LS surveillance.

Impact of genetic counseling strategy on diagnostic yield and workload for genome-sequencing-based tumor diagnostics.

PURPOSE: Genome sequencing (GS) enables comprehensive molecular analysis of tumors and identification of hereditary cancer predisposition. According to guidelines, directly determining pathogenic germline variants (PGVs) requires pretest genetic counseling, which is cost-ineffective. Referral for genetic counseling based on tumor variants alone could miss relevant PGVs and/or result in unnecessary referrals. METHODS: We validated GS for detection of germline variants and simulated 3 strategies using paired tumor-normal GS data of 937 metastatic patients. In strategy-1, genetic counseling before tumor testing allowed direct PGV analysis. In strategy-2 and -3, germline testing and referral for post-test genetic counseling is based on tumor variants using Dutch (strategy-2) or Europen Society for Medical Oncology (ESMO) Precision Medicine Working Group (strategy-3) guidelines. RESULTS: In strategy-1, PGVs would be detected in 50 patients (number-needed-to counsel; NTC = 18.7). In strategy-2, 86 patients would have been referred for genetic counseling and 43 would have PGVs (NTC = 2). In strategy-3, 94 patients would have been referred for genetic counseling and 32 would have PGVs (NTC = 2.9). Hence, 43 and 62 patients, respectively, were unnecessarily referred based on a somatic variant. CONCLUSION: Both post-tumor test counseling strategies (2 and 3) had significantly lower NTC, and strategy-2 had the highest PGV yield. Combining pre-tumor test mainstreaming and post-tumor test counseling may maximize the clinically relevant PGV yield and minimize unnecessary referrals.

Enrichment of colibactin-associated mutational signatures in unexplained colorectal polyposis patients.

BACKGROUND: Colibactin, a genotoxin produced by polyketide synthase harboring (pks+) bacteria, induces double-strand breaks and chromosome aberrations. Consequently, enrichment of pks+Escherichia coli in colorectal cancer and polyposis suggests a possible carcinogenic effect in the large intestine. Additionally, specific colibactin-associated mutational signatures; SBS88 and ID18 in the Catalogue of Somatic Mutations in Cancer database, are detected in colorectal carcinomas. Previous research showed that a recurrent APC splice variant perfectly fits SBS88. METHODS: In this study, we explore the presence of colibactin-associated signatures and fecal pks in an unexplained polyposis cohort. Somatic targeted Next-Generation Sequencing (NGS) was performed for 379 patients. Additionally, for a subset of 29 patients, metagenomics was performed on feces and mutational signature analyses using Whole-Genome Sequencing (WGS) on Formalin-Fixed Paraffin Embedded (FFPE) colorectal tissue blocks. RESULTS: NGS showed somatic APC variants fitting SBS88 or ID18 in at least one colorectal adenoma or carcinoma in 29% of patients. Fecal metagenomic analyses revealed enriched presence of pks genes in patients with somatic variants fitting colibactin-associated signatures compared to patients without variants fitting colibactin-associated signatures. Also, mutational signature analyses showed enrichment of SBS88 and ID18 in patients with variants fitting these signatures in NGS compared to patients without. CONCLUSIONS: These findings further support colibactins ability to mutagenize colorectal mucosa and contribute to the development of colorectal adenomas and carcinomas explaining a relevant part of patients with unexplained polyposis.

Somatic hits in mismatch repair genes in colorectal cancer among non-seminoma testicular cancer survivors.

BACKGROUND: Non-seminoma testicular cancer survivors (TCS) have an increased risk of developing colorectal cancer (CRC) when they have been treated with platinum-based chemotherapy. Previously we demonstrated that among Hodgkin lymphoma survivors (HLS) there is enrichment of rare mismatch repair (MMR) deficient (MMRd) CRCs with somatic hits in MMR genes. We speculate that this phenomenon could also occur among other cancer survivors. We therefore aim to determine the MMR status and its underlying mechanism in CRC among TCS (TCS-CRC). METHODS: Thirty TCS-CRC, identified through the Dutch pathology registry, were analysed for MMR proteins by immunohistochemistry. Next-generation sequencing was performed in MMRd CRCs without MLH1 promoter hypermethylation (n = 4). Data were compared with a male cohort with primary CRC (P-CRC, n = 629). RESULTS: MMRd was found in 17% of TCS-CRCs vs. 9% in P-CRC (p = 0.13). MMRd was more often caused by somatic double or single hit in MMR genes by mutation or loss of heterozygosity in TCS-CRCs (3/30 (10%) vs. 11/629 (2%) in P-CRCs (p < 0.01)). CONCLUSIONS: MMRd CRCs with somatic double or single hit are more frequent in this small cohort of TCS compared with P-CRC. Exposure to anticancer treatments appears to be associated with the development of these rare MMRd CRC among cancer survivors.

Statin use is associated with a reduced incidence of colorectal cancer expressing SMAD4.

BACKGROUND: Long-term use of statins is associated with a small reduced risk of colorectal cancer but their mechanism of action is not well understood. While they are generally believed to act on KRAS, we have previously proposed that they act via influencing the BMP pathway. The objective of this study was to look for associations between statin use and the risk of developing colorectal cancer of a particular molecular subtype. METHODS: By linking two registries unique to the Netherlands, 69,272 statin users and 94,753 controls were identified and, if they developed colorectal cancer, their specimens traced. Colorectal cancers were molecularly subtyped according to the expression of SMAD4 and the mutation status of KRAS and BRAF. RESULTS: Statin use was associated with a reduction in the risk of developing colorectal cancer regardless of molecular subtype (HR 0.77; 95% CI 0.66-0.89) and a larger reduction in the risk of developing SMAD4-positive colorectal cancer (OR 0.64; 95% CI 0.42-0.82). There was no relationship between statin use and the risk of developing colorectal cancer with a mutation in KRAS and/or BRAF. CONCLUSIONS: Statin use is associated with a reduced risk of developing colorectal cancer with intact SMAD4 expression.

Multicenter Comparison of Molecular Tumor Boards in The Netherlands: Definition, Composition, Methods, and Targeted Therapy Recommendations.

BACKGROUND: Molecular tumor boards (MTBs) provide rational, genomics-driven, patient-tailored treatment recommendations. Worldwide, MTBs differ in terms of scope, composition, methods, and recommendations. This study aimed to assess differences in methods and agreement in treatment recommendations among MTBs from tertiary cancer referral centers in The Netherlands. MATERIALS AND METHODS: MTBs from all tertiary cancer referral centers in The Netherlands were invited to participate. A survey assessing scope, value, logistics, composition, decision-making method, reporting, and registration of the MTBs was completed through on-site interviews with members from each MTB. Targeted therapy recommendations were compared using 10 anonymized cases. Participating MTBs were asked to provide a treatment recommendation in accordance with their own methods. Agreement was based on which molecular alteration(s) was considered actionable with the next line of targeted therapy. RESULTS: Interviews with 24 members of eight MTBs revealed that all participating MTBs focused on rare or complex mutational cancer profiles, operated independently of cancer type-specific multidisciplinary teams, and consisted of at least (thoracic and/or medical) oncologists, pathologists, and clinical scientists in molecular pathology. Differences were the types of cancer discussed and the methods used to achieve a recommendation. Nevertheless, agreement among MTB recommendations, based on identified actionable molecular alteration(s), was high for the 10 evaluated cases (86%). CONCLUSION: MTBs associated with tertiary cancer referral centers in The Netherlands are similar in setup and reach a high agreement in recommendations for rare or complex mutational cancer profiles. We propose a "Dutch MTB model" for an optimal, collaborative, and nationally aligned MTB workflow. IMPLICATIONS FOR PRACTICE: Interpretation of genomic analyses for optimal choice of target therapy for patients with cancer is becoming increasingly complex. A molecular tumor board (MTB) supports oncologists in rationalizing therapy options. However, there is no consensus on the most optimal setup for an MTB, which can affect the quality of recommendations. This study reveals that the eight MTBs associated with tertiary cancer referral centers in The Netherlands are similar in setup and reach a high agreement in recommendations for rare or complex mutational profiles. The Dutch MTB model is based on a collaborative and nationally aligned workflow with interinstitutional collaboration and data sharing.

Comedonecrosis Gleason pattern 5 is associated with worse clinical outcome in operated prostate cancer patients.

Individual growth patterns and cribriform architecture are increasingly considered in risk stratification and clinical decision-making in men with prostate cancer. Our objective was to establish the prognostic value of individual Gleason 5 patterns in a radical prostatectomy (RP) cohort. We reviewed 1064 RPs and recorded Grade Group (GG), pT-stage, surgical margin status, Gleason 4 and 5 growth patterns as well as intraductal carcinoma. The clinical endpoints were biochemical recurrence and post-operative distant metastasis. Gleason pattern 5 was present in 339 (31.9%) RPs, of which 47 (4.4%) presented as primary, 166 (15.6%) as secondary, and 126 (11.8%) as tertiary pattern. Single cells/cords were present in 321 (94.7%) tumors with Gleason pattern 5, solid fields in 90 (26.5%), and comedonecrosis in invasive carcinoma in 32 (9.4%) tumors. Solid fields demonstrated either a small nested morphology (n = 50, 14.7%) or medium to large solid fields (n = 61, 18.0%). Cribriform architecture was present in 568 (53.4%) RPs. Medium to large solid fields and comedonecrosis coincided with cribriform architecture in all specimens, and were not observed in cribriform-negative cases. In multivariable analysis adjusted for Prostate-Specific Antigen, pT-stage, GG, surgical margin status and lymph node metastases, cribriform architecture (Hazard Ratio (HR) 9.9; 95% Confidence Interval (CI) 3.9-25.5, P < 0.001) and comedonecrosis (HR 2.1, 95% CI 1.2-3.7, P = 0.01) were independent predictors for metastasis-free survival, while single cells/cords (HR 1.2; 95% CI 0.7-1.8, P = 0.55) and medium to large solid fields (HR 1.6, 95% CI 0.9-2.7, P = 0.09) were not. In conclusion, comedonecrosis in invasive carcinoma is an independent prognostic Gleason 5 pattern for metastasis-free survival after RP. These data support the current recommendations to routinely include cribriform pattern in pathology reports and indicate that comedonecrosis should also be commented on.

Cribriform architecture in radical prostatectomies predicts oncological outcome in Gleason score 8 prostate cancer patients.

The Gleason score is an important parameter for clinical outcome in prostate cancer patients. Gleason score 8 is a heterogeneous disease including Gleason score 3 + 5, 4 + 4, and 5 + 3 tumors, and encompasses a broad range of tumor growth patterns. Our objective was to characterize individual growth patterns and identify prognostic parameters in Gleason score 8 prostate cancer patients. We reviewed 1064 radical prostatectomy specimens, recorded individual Gleason 4 and 5 growth patterns as well as presence of intraductal carcinoma, and evaluated biochemical recurrence- and metastasis-free survival. Gleason score 8 disease was identified in 140 (13%) patients, of whom 76 (54%) had Gleason score 3 + 5, 46 (33%) 4 + 4, and 18 (13%) 5 + 3 disease. Invasive cribriform and/or intraductal carcinoma (n = 87, 62%) was observed more frequently in Gleason score 4 + 4 (93%) than 3 + 5 (47%; P < 0.001) and 5 + 3 (44%; P < 0.001) patients. Gleason pattern 5 was present in 110 (79%) men: as single cells and/or cords in 99 (90%) and solid fields in 32 (29%) cases. Solid field pattern 5 coexisted with cribriform architecture (23/32, 72%) more frequently than nonsolid pattern 5 cases (36/78, 46%, P = 0.02). In multivariable analysis including age, prostate-specific antigen, pT-stage, surgical margin status, and lymph node metastases, presence of cribriform architecture was an independent parameter for biochemical recurrence-free (hazard ratio (HR) 2.0, 95% confidence interval (CI) 1.0-3.7; P = 0.04) and metastasis-free (HR 3.5, 95% CI 1.0-12.3; P = 0.05) survival. In conclusion, invasive cribriform and/or intraductal carcinoma occurs more frequently in Gleason score 4 + 4 prostate cancer patients than in Gleason score 3 + 5 and 5 + 3, and is an independent parameter for biochemical recurrence and metastasis. Therefore, cribriform architecture has added value in risk stratification of Gleason score 8 prostate cancer patients.

NTRK fusions are extremely rare in bone tumours.

AIMS: Because of the efficacy of tropomyosin receptor kinase (Trk) inhibitor therapy in tumours with rearrangements of the neurotrophic tyrosine kinase receptor genes (NRTK genes), there has been a surge in demand for NTRK fusion screening. To date, most studies involving mesenchymal tumours have focused on soft tissue tumours, and data on bone tumours are sparse. Hence, we aimed to explore the frequency of NTRK fusions in a large series of primary bone tumours. METHODS AND RESULTS: Immunohistochemical expression of pan-Trk was successfully assessed in 354 primary bone tumours by the use of tissue microarrays. In a selection of positive cases, additional molecular analysis for NTRK fusions was performed with anchored multiplex polymerase chain reaction-based targeted next-generation sequencing. Positivity was found in 19 cases (5%), which comprised Ewing sarcoma (n = 6, 33%), osteosarcoma (n = 11, 13%), and giant-cell tumour of bone (n = 2, 3%). In all except one case, cytoplasmic staining was observed. Weak staining was most often observed (n = 13), although five cases showed moderate staining and one case showed focal strong staining. Molecular analysis was successful in six cases, all of which were negative for NTRK fusions. CONCLUSION: The likelihood of finding an NTRK fusion in bone tumours in clinical practice is extremely low. This may imply that, if more comprehensive large-scale molecular studies confirm this, routine predictive NTRK testing in bone tumour patients with advanced disease may be reconsidered.

The coding microsatellite mutation profile of PMS2-deficient colorectal cancer.

Lynch syndrome (LS) is caused by a pathogenic heterozygous germline variant in one of the DNA mismatch repair (MMR) genes: MLH1, MSH2, MSH6 or PMS2. LS-associated colorectal carcinomas (CRCs) are characterized by MMR deficiency and by accumulation of multiple insertions/deletions at coding microsatellites (cMS). MMR deficiency-induced variants at defined cMS loci have a driver function and promote tumorigenesis. Notably, PMS2 variant carriers face only a slightly increased risk of developing CRC. Here, we investigate whether this lower penetrance is also reflected by differences in molecular features and cMS variant patterns. Tumor DNA was extracted from formalin-fixed paraffin-embedded (FFPE) tissue cores or sections (n = 90). Tumors originated from genetically proven germline pathogenic MMR variant carriers (including 14 PMS2-deficient tumors). The mutational spectrum was analyzed using fluorescently labeled primers specific for 18 cMS previously described as mutational targets in MMR-deficient tumors. Immune cell infiltration was analyzed by immunohistochemical detection of T-cells on FFPE tissue sections. The cMS spectrum of PMS2-deficient CRCs did not show any significant differences from MLH1/MSH2-deficient CRCs. PMS2-deficient tumors, however, displayed lower CD3-positive T-cell infiltration compared to other MMR-deficient cancers (28.00 vs. 55.00 per 0.1 mm2, p = 0.0025). Our study demonstrates that the spectrum of potentially immunogenic cMS variants in CRCs from PMS2 gene variant carriers is similar to that observed in CRCs from other MMR gene variant carriers. Lower immune cell infiltration observed in PMS2-deficient CRCs could be the result of alternative mechanisms of immune evasion or immune cell exclusion, similar to those seen in MMR-proficient tumors.

Digenic inheritance of MSH6 and MUTYH variants in familial colorectal cancer.

We describe a family severely affected by colorectal cancer (CRC) where whole-exome sequencing identified the coinheritance of the germline variants encoding MSH6 p.Thr1100Met and MUTYH p.Tyr179Cys in, at least, three CRC patients diagnosed before 60 years of age. Digenic inheritance of monoallelic MSH6 variants of uncertain significance and MUTYH variants has been suggested to predispose to Lynch syndrome-associated cancers; however, cosegregation with disease in the familial setting has not yet been established. The identification of individuals carrying multiple potential cancer risk variants is expected to rise with the increased application of whole-genome sequencing and large multigene panel testing in clinical genetic counseling of familial cancer patients. Here we demonstrate the coinheritance of monoallelic variants in MSH6 and MUTYH consistent with cosegregation with CRC, further supporting a role for digenic inheritance in cancer predisposition.

Clinicopathological characteristics of glomeruloid architecture in prostate cancer.

Glomeruloid architecture is the least common Gleason 4 growth pattern in prostate adenocarcinoma. Its clinicopathological features and relation with cribriform architecture, which has been recognized as an adverse feature, remains to be established. Our objective was to investigate clinicopathological features of glomeruloid architecture in radical prostatectomies. We reviewed 1064 radical prostatectomy specimens and recorded Grade Group, pT-stage, margin status, Gleason pattern percentages, and growth patterns. Simple and complex glomerulations were distinguished by gland size and intraluminal cribriform protrusions. Clinical endpoint was biochemical recurrence-free survival. Glomerulations were identified in 365 (34%) specimens. In 472 Grade Group 2 patients, 210 (44%) had simple and 92 (19%) complex glomerulations. Complex glomerulations coincided with cribriform architecture more often than simple glomerulations (67% versus 52%; P = 0.01). Men with simple glomerulations had significantly lower prostate specific antigen (PSA) levels (9.7 versus 12.1 ng/ml; P = 0.03), percentage Gleason pattern 4 (19% versus 25%; P = 0.001), extra-prostatic extension (34% versus 50%; P = 0.01), and positive surgical margins (25% versus 39%; P = 0.04) than those with cribriform architecture. Extra-prostatic extension (37%) and positive surgical margins (30%) in men with complex glomerulations resembled those with simple glomeruloid rather than those with cribriform architecture. In multivariate Cox regression analysis adjusted for PSA, pT-stage, margin status, and lymph node metastases, cribriform architecture had independent predictive value for biochemical recurrence-free survival (hazard ratio (HR)) 1.9; 95% confidence interval (CI) 1.2-2.9; P = 0.004), while simple (HR 0.8; 95% CI 0.5-1.2; P = 0.26) and complex (HR 0.9; 95% CI 0.5-1.6; P = 0.67) glomerulations did not. Both simple and complex glomeruloid architecture are associated with better outcome than cribriform architecture in Grade Group 2 prostate cancer patients. Therefore, glomeruloid pattern and particularly complex glomerulations should not be classified as a cribriform growth pattern variant in radical prostatectomy specimens.

MYD88 mutations identify a molecular subgroup of diffuse large B-cell lymphoma with an unfavorable prognosis.

The 2016 World Health Organization classification defines diffuse large B-cell lymphoma (DLBCL) subtypes based on Epstein-Barr virus (EBV) infection and oncogenic rearrangements of MYC/BCL2/BCL6 as drivers of lymphomagenesis. A subset of DLBCL, however, is characterized by activating mutations in MYD88/CD79B We investigated whether MYD88/CD79B mutations could improve the classification and prognostication of DLBCL. In 250 primary DLBCL, MYD88/CD79B mutations were identified by allele-specific polymerase chain reaction or next-generation-sequencing, MYC/BCL2/BCL6 rearrangements were analyzed by fluorescence in situ hybridization, and EBV was studied by EBV-encoded RNA in situ hybridization. Associations of molecular features with clinicopathologic characteristics, outcome, and prognosis according to the International Prognostic Index (IPI) were investigated. MYD88 and CD79B mutations were identified in 29.6% and 12.3%, MYC, BCL2, and BCL6 rearrangements in 10.6%, 13.6%, and 20.3%, and EBV in 11.7% of DLBCL, respectively. Prominent mutual exclusivity between EBV positivity, rearrangements, and MYD88/CD79B mutations established the value of molecular markers for the recognition of biologically distinct DLBCL subtypes. MYD88-mutated DLBCL had a significantly inferior 5-year overall survival than wild-type MYD88 DLBCL (log-rank; P=0.019). DLBCL without any of the studied aberrations had superior overall survival compared to cases carrying ≥1 aberrancy (log-rank; P=0.010). MYD88 mutations retained their adverse prognostic impact upon adjustment for other genetic and clinical variables by multivariable analysis and improved the prognostic performance of the IPI. This study demonstrates the clinical utility of defining MYD88-mutated DLBCL as a distinct molecular subtype with adverse prognosis. Our data call for sequence analysis of MYD88 in routine diagnostics of DLBCL to optimize classification and prognostication, and to guide the development of improved treatment strategies.

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.

Molecular Background of Colorectal Tumors From Patients With Lynch Syndrome Associated With Germline Variants in PMS2.

BACKGROUND & AIMS: Germline variants in mismatch repair genes MLH1, MSH2 (EPCAM), MSH6, or PMS2 cause Lynch syndrome. Patients with these variants have an increased risk of developing colorectal cancers (CRCs) that differ from sporadic CRCs in genetic and histologic features. It has been a challenge to study CRCs associated with PMS2 variants (PMS2-associated CRCs) because these develop less frequently and in older patients than CRCs with variants in other mismatch repair genes. METHODS: We analyzed 20 CRCs associated with germline variants in PMS2, 22 sporadic CRCs, 18 CRCs with germline variants in MSH2, and 24 CRCs from patients with germline variants in MLH1. Tumor tissue blocks were collected from Dutch pathology departments in 2017. After extraction of tumor DNA, we used a platform designed to detect approximately 3,000 somatic hotspot variants in 55 genes (including KRAS, APC, CTNNB1, and TP53). Somatic variant frequencies were compared using the Fisher exact test. RESULTS: None of the PMS2-associated CRCs contained any somatic variants in the catenin-ß1 gene (CTNNB1), which encodes ß-catenin, whereas 14 of 24 MLH1-associated CRCs (58%) contained variants in CTNNB1. Half the PMS2-associated CRCs contained KRAS variants, but only 20% of these were in hotspots that encoded G12D or G13D. These hotspot variants occurred more frequently in CRCs associated with variants in MLH1 (37.5%; P = .44) and MSH2 (71.4%; P = .035) than in those associated with variants in PMS2. CONCLUSIONS: In a genetic analysis of 84 colorectal tumors, we found tumors from patients with PMS2-associated Lynch syndrome to be distinct from colorectal tumors associated with defects in other mismatch repair genes. This might account for differences in development and less frequent occurrence.

HLA-G protein expression in colorectal cancer evaluated by immunohistochemistry and western blot analysis: Its expression characteristics remain enigmatic.

HLA-G protein expression could play a role in evasion of tumor immune surveillance. Accumulating evidence demonstrates that HLA-G is expressed in different types of malignancies, including colorectal cancer (CRC). The purpose of the current study was to further unravel whether HLA-G protein expression could play a role in immune evasion of CRC. Therefore, to firmly establish HLA-G protein expression, eight early passage human CRC cell lines and five human rectal cancer tissues were analyzed by western blot analysis. The results obtained by western blot analysis were compared with immunohistochemistry on tumor tissue sections of the same patient. Furthermore, multiple monoclonal antibodies (mAbs), 4H84, MEM-G/1 and 5A6G7, targeting HLA-G were used to unravel staining patterns. We showed that results obtained with immunohistochemistry did not correlate with protein expression detected by western blot analysis, using three different HLA-G targeting mAbs. Furthermore, with respect to the specificity of the mAbs employed, additional immune reactivity was detected using the mAbs MEM-G/1 and 5A6G7 in western blot analysis with K562 control cell lines overexpressing HLA-A2 or HLA-G, all tumor tissues and in two out of eight CRC cell lines. Based on the current study and our previously reported results, we conclude that claiming HLA-G plays a role in immune modulation of CRC seems premature, as results from anti-body based detection of HLA-G protein remain inconclusive. Until the time that detection of HLA-G is sensitive enough to detect all aspects of HLA-G expression in biological samples, rather than transfected cells or long time cultured cell lines, conclusions should be drawn with great care.