Prevalence of microsatellite instable and Epstein-Barr Virus-driven gastroesophageal cancer in a large Belgian cohort.

Introduction: Patients with gastroesophageal adenocarcinoma (GEC) with microsatellite instability-high (MSI-H) or Epstein Barr Virus positivity (EBV+) might be good candidates for immunotherapy. Incidences of about 10% have been reported for both features, but are dependent on geographical region and disease stage. Aim: The aim is to study the prevalence of MSI-H and EBV+ in a Belgian single center cohort of patients with GEC. Methods: We retrospectively assessed the files of all patients with a newly diagnosed GEC between August, 1st 2018 and February, 29th 2020 at the University Hospitals Leuven, Belgium. Microsatellite instability (MSI) status was determined using immunohistochemistry (IHC) and polymerase chain reaction (PCR). EBV+ was assessed using in situ hybridization (ISH). A case report is provided to illustrate the importance of testing for MSI in GEC. Results: 247 gastroesophageal adenocarcinomas were included in this analysis. 62 (56% stage IV) of those were tested for EBV, but only 1 turned out to be EBV positive (1.6%). 116 patients (44.0% stage IV) were tested for MSI, of which 11 were MSI-H (9.5%). Half of the MSI-H tumors identified were at the gastroesophageal junction (GEJ). A patient with MSI-H metastatic GEC obtained a complete response with nivolumab, which persisted after discontinuation of treatment. Conclusion: While we confirm that about 10% of GECs are MSI-H, the incidence of EBV+ in our cohort (1.6%) is clearly lower than expected. Given the important prognostic and predictive implications, every gastroesophageal cancer should be tested for MSI.

Analysis of 108 patients with endometrial carcinoma using the PROMISE classification and additional genetic analyses for MMR-D.

OBJECTIVES: To apply the Proactive Molecular Risk Classifier for Endometrial Cancer (ProMisE) to a consecutive series of endometrial cancer (EC) patients diagnosed at a tertiary referral center and assign EC specimens to one of four molecular subgroups using immunohistochemistry (IHC) for p53/mismatch repair protein expression and sequencing for Polymerase Epsilon Exonuclease Domain Mutations (POLE-EDM). Mismatch Repair Deficient (MMR-D) cases were more thoroughly investigated to identify underlying somatic or germline genetic defects. METHODS: Hundred-and eight consecutive endometrial cancer patients, diagnosed between March 2017 and April 2019, were subjected to immunohistochemical and molecular analysis, according to ProMisE. IHC for p53 and the mismatch repair proteins (MLH1, PMS2, MSH6 and PMS2) was performed. All patients were also tested for POLE-EDM by Sanger sequencing. In addition, tumor and corresponding normal tissue of cases with abnormal MMR IHC were tested by PCR for microsatellite instability (MSI) (MSI analysis system, Promega). Hypermethylation of MLH1 promotor was tested with (methylation specific) multiplex ligation dependent probe amplification. MMR-D cases were subjected to germline mutation analysis of the mismatch repair genes, using next generation sequencing on MiSeq (Illumina) with the BRCA Hereditary Cancer MASTR Plus, (Multiplicom/Agilent), RNA mutation analysis and MLPA. RESULTS: FIGO classification was stage IA (n = 54), IB (n = 22) II(n = 8), III(n = 18) and IV(n = 6). Of the 33 patients with MMR-D on IHC (31%), 26 showed MLH1 promotor hypermethylation as the probable cause of MMR-D. The remaining 7 patients without MLH1 promotor hypermethylation were referred for germline analysis of Lynch syndrome. Six patients carried a pathogenic germline mutation in one of the mismatch repair genes: MSH6(n = 3), PMS2(n = 1), MLH1(n = 1) and MSH2 (n = 1). Pathogenic POLE-EDM were identified in 7 (6%) patients. Multiple molecular features (POLE-EDM + MMR-D or POLE-EDM + p53 abnormal) were observed in 4 patients (4%). A high concordance between MMR-D and microsatellite instability was observed in our cohort. In cases of a genetic defect in the MMR genes, we do note a large proportion of cases exhibiting microsatellite instability. On the contrary a hypermutation state, as seen in POLE EDM, does not result in accompanied phenotypic changes in MSI status. CONCLUSION: The ProMisE classification proved to be an efficient and easily implementable system. Future research should elucidate the precise biological and prognostic meaning of the cases with multiple molecular markers.

Erratum: Capturing the wide variety of impaired fracture healing phenotypes in Neurofibromatosis Type 1 with eight key factors: a computational study.

This corrects the article DOI: 10.1038/srep20010.

Choroidal abnormalities in café-au-lait syndromes: a new differential diagnostic tool?

The best known café-au-lait syndrome is neurofibromatosis type 1 (NF1). Legius syndrome (LS) is another, rarer syndrome with café-au-lait macules (CALMs). In young patients their clinical picture is often indistinguishable. We investigated the presence of choroidal abnormalities in syndromes with CALMs as a candidate tool for a more efficient diagnosis. Thirty-four patients with NF1 (14 with a truncating mutation, 14 with a non-truncating mutation and 6 with unknown mutation) and 11 patients with LS. All patients underwent an ophthalmological examination. Infrared images were performed. Choroidal nodules were diagnosed in 65% of the NF1 group. About 71% of NF1 patients with a truncating mutation and 50% of patients with a non-truncating mutation were found to have nodules. Choroidal nodules were seen in 18% of the LS patients, never more than one nodule/eye was detected in this group. Choroidal nodules are more abundantly present in NF1 genotypes with truncating mutations. In contrast, the number of choroidal nodules in LS is comparable with their presence in healthy individuals. Especially at an early age, when the clinical picture is incomplete, the detection of choroidal nodules is of diagnostic value, and helps in an appropriate genetic counselling and follow-up. These results support the suggestion to include choroidal nodules to the diagnostic criteria for NF1.

Capturing the wide variety of impaired fracture healing phenotypes in Neurofibromatosis Type 1 with eight key factors: a computational study.

Congenital pseudarthrosis of the tibia (CPT) is a rare disease which normally presents itself during early childhood by anterolateral bowing of the tibia and spontaneous tibial fractures. Although the exact etiology of CPT is highly debated, 40-80% of CPT patients are carriers of a mutation in the Neurofibromatosis Type 1 (NF1) gene, which can potentially result in an altered phenotype of the skeletal cells and impaired bone healing. In this study we use a computational model of bone regeneration to examine the effect of the Nf1 mutation on bone fracture healing by altering the parameter values of eight key factors which describe the aberrant cellular behaviour of Nf1 haploinsufficient and Nf1 bi-allelically inactivated cells. We show that the computational model is able to predict the formation of a hamartoma as well as a wide variety of CPT phenotypes through different combinations of altered parameter values. A sensitivity analysis by "Design of Experiments" identified the impaired endochondral ossification process and increased infiltration of fibroblastic cells as key contributors to the degree of severity of CPT. Hence, the computational model results have added credibility to the experimental hypothesis of a genetic cause (i.e. Nf1 mutation) for CPT.

Preimplantation genetic diagnosis using fluorescent in situ hybridization for cancer predisposition syndromes caused by microdeletions.

BACKGROUND: Neurofibromatosis type 1 (NF1) and Von Hippel-Lindau (VHL) are dominantly inherited late onset cancer predisposition syndromes caused by mutations in the respective tumor suppressor genes (TSGs) NF1 and VHL. Less frequently TSGs are partially or fully deleted. Preimplantation genetic diagnosis (PGD) for cancer predisposition can be applied to select against the mutant allele in carrier couples. However, microdeletions within a single cell can, at present, not be detected by molecular diagnostic methods usually applied for PGD of monogenic disorders. METHODS: We performed PGD using interphase fluorescent in situ hybridization (FISH) on single blastomeres for three couples of which the women carried a microdeletion. One patient had the recurrent 1.4 Mb microdeletion covering NF1, a second suffered from an intragenic NF1 deletion and the last had a deletion of VHL. RESULTS: In total, seven PGD cycles were carried out for these couples, which resulted in the delivery of a healthy twin for the VHL microdeletion carrier. CONCLUSIONS: FISH-based PGD is a straightforward approach to detect (micro)deletions in single blastomeres. It seems likely that the number of conditions for which PGD-FISH is beneficial will increase rapidly with the advent of high-resolution arrays.

Elevated risk for MPNST in NF1 microdeletion patients.

An NF1 microdeletion is the single most commonly reported mutation in individuals with neurofibromatosis type 1 (NF1). Individuals with an NF1 microdeletion have, as a group, more neurofibromas at a younger age than the group of all individuals with NF1. We report that NF1 microdeletion individuals additionally have a substantially higher lifetime risk for the development of malignant peripheral nerve sheath tumors than individuals with NF1 who do not have an NF1 microdeletion. This should be taken into account in the medical follow-up of individuals with an NF1 microdeletion.

Second polar body inclusion results in diploid/triploid mixoploidy.

We report three cases with a typical diploid/triploid mixoploidy. Cytogenetic analysis showed a normal diploid karyotype in peripheral blood lymphocytes and a mixture of diploid and triploid cells in skin fibroblasts. We analysed microsatellite markers in patients blood lymphocytes and skin fibroblasts and compared the results with the microsatellite markers in the parents. The extra haploid set was in all three cases of maternal origin. In one case the markers were not very informative but in two cases pericentromeric markers showed a single dose of one paternal allele and a double dose of one maternal allele, more telomeric markers showed one paternal allele and two different maternal alleles. These observations can only be explained by the inclusion of the second polar body in one of the blastomeres at the cleavage stage.

Recombination hotspot in NF1 microdeletion patients.

Neurofibromatosis type 1 (NF1) patients that are heterozygous for an NF1 microdeletion are remarkable for an early age at onset and an excessive burden of dermal neurofibromas. Microdeletions are predominantly maternal in origin and arise by unequal crossover between misaligned NF1REP paralogous sequence blocks which flank the NF1 gene. We mapped and sequenced the breakpoints in several patients and designed primers within each paralog to specifically amplify a 3.4 kb deletion junction fragment. This assay amplified a deletion junction fragment from 25 of the 54 unrelated NF1 microdeletion patients screened. Sequence analysis demonstrated that each of the 25 recombination events occurred in a discrete 2 kb recombination hotspot within each of the flanking NF1REPs. Two recombination events were accompanied by apparent gene conversion. A search for recombination-prone motifs revealed a chi-like sequence; however, it is unknown whether this element stimulates recombination to occur at the hotspot. The deletion-junction assay will facilitate the prospective identification of patients with NF1 microdeletion at this hotspot for genotype-phenotype correlation studies and diagnostic evaluation.

Unequal meiotic crossover: a frequent cause of NF1 microdeletions.

Neurofibromatosis type 1 is a common autosomal dominant disorder caused by mutations of the NF1 gene on chromosome 17. In only 5%-10% of cases, a microdeletion including the NF1 gene is found. We analyzed a set of polymorphic dinucleotide-repeat markers flanking the microdeletion on chromosome 17 in a group of seven unrelated families with a de novo NF1 microdeletion. Six of seven microdeletions were of maternal origin. The breakpoints of the microdeletions of maternal origin were localized in flanking paralogous sequences, called "NF1-REPs." The single deletion of paternal origin was shorter, and no crossover occurred on the paternal chromosome 17 during transmission. Five of the six cases of maternal origin were informative, and all five showed a crossover, between the flanking markers, after maternal transmission. The observed crossovers flanking the NF1 region suggest that these NF1 microdeletions result from an unequal crossover in maternal meiosis I, mediated by a misalignment of the flanking NF1-REPs.

Molecular studies in 20 submicroscopic neurofibromatosis type 1 gene deletions.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder characterized by a marked variability in expression. A more severe phenotype is frequently observed in the group of patients carrying a large NF1 deletion. To study the extent of the microdeletion in these NF1 patients, we generated a partial physical map of the NF1 flanking region. We describe seven PACs and three new polymorphic dinucleotide repeats located outside the NF1 gene and analyzed 20 unrelated individuals with an NF1 microdeletion in a collaborative study. We detected one individual with a substantially smaller deletion including only the NF1 gene and its three embedded genes. In the other 19 patients, the deletion extended at least 1 Mb. The parental origin of the deletion was determined in 15 individuals and was maternal in 13 and paternal in two cases. The new molecular tools described here can be used to unequivocally diagnose a possible extragenic extension of an NF1 deletion.

Bone marrow stromal cells as targets for gene therapy of hemophilia A.

Attempts to develop an ex vivo gene therapy strategy for hemophilia A, using either primary T cells or bone marrow (BM) stem/progenitor cells have been unsuccessful, due to the inability of these cell types to express coagulation factor VIII (FVIII). As an alternative, we evaluated the potential of BM-derived stromal cells which can be readily obtained and expanded in vitro. Human and murine BM stromal cells were transduced with an intron-based Moloney murine leukemia virus (MoMLV) retroviral vector expressing a B-domain-deleted human factor VIII cDNA (designated as MFG-FVIIIdeltaB). Transduction efficiencies were increased 10- to 15-fold by phosphate depletion and centrifugation, which obviated the need for selective enrichment of the transduced BM stromal cells. This resulted in high FVIII expression levels in transduced human (180 +/- 4 ng FVIII/10[6] cells per 24 hr) and mouse (900 +/- 130 ng FVIII/10[6] cells per 24 hr) BM stromal cells. Pseudotyping of the MFG-FVIIIdeltaB retroviral vectors with the gibbon ape leukemia virus envelope (GALV-env) resulted in significantly higher transduction efficiencies (100 +/- 20%) and FVIII expression levels (390 +/- 10 ng FVIII/10[6] cells per 24 hr) in transduced human BM stromal cells than with standard amphotropic vectors. This difference in transduction efficiency correlated with the higher titer of the GALV-env pseudotyped viral vectors and with the higher GALV receptor (GLVR-1) versus amphotropic receptor (GLVR-2) mRNA expression levels in human BM stromal cells. These findings demonstrate the potential of BM stromal cells for gene therapy in general and hemophilia A in particular.