RNA-based mutation analysis identifies an unusual MSH6 splicing defect and circumvents PMS2 pseudogene interference

Heterozygous germline mutations in one of the mismatch repair (MMR) genes MLH1, MSH2, MSH6, and PMS2 cause hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome, a dominantly inherited cancer susceptibility syndrome. Recent reports provide evidence for a novel recessively inherited cancer syndrome with constitutive MMR deficiency due to biallelic germline mutations in one of the MMR genes. MMR-deficiency (MMR-D) syndrome is characterized by childhood brain tumors, hematological and/or gastrointestinal malignancies, and signs of neurofibromatosis type 1 (NF1). We established an RNA-based mutation detection assay for the four MMR genes, since 1) a number of splicing defects may escape detection by the analysis of genomic DNA, and 2) DNA-based mutation detection in the PMS2 gene is severely hampered by the presence of multiple highly similar pseudogenes, including PMS2CL. Using this assay, which is based on direct cDNA sequencing of RT-PCR products, we investigated two families with children suspected to suffer from MMR-D syndrome. We identified a homozygous complex MSH6 splicing alteration in the index patients of the first family and a novel homozygous PMS2 mutation (c.182delA) in the index patient of the second family. Furthermore, we demonstrate, by the analysis of a PMS2/PMS2CL "hybrid" allele carrier, that RNA-based PMS2 testing effectively avoids the caveats of genomic DNA amplification approaches; i.e., pseudogene coamplification as well as allelic dropout, and will, thus, allow more sensitive mutation analysis in MMR deficiency and in HNPCC patients with PMS2 defects.     

Does the interval from tumour surgery to radiotherapy influence survival in paediatric high grade glioma?

Purpose

Paediatric high grade glioma (pHGG) are rare. Following maximum safe resection, children >3 years with HGG receive radiotherapy as standard of care. Whether the interval from tumour surgery to radiotherapy (ISRT) influences survival is disputed in adults with glioblastoma, data for children are lacking. This retrospective single-centre analysis investigates a possible impact of ISRT on survival in paediatric patients with HGG.

Methods

Survival was analysed in patients aged 3–19 years with non-pontine HGG.

Results

Thirty-eight patients were included (female:male 19:19) with a median age of 11.0 years (3.4–17.7). Seventeen patients had grade 3 and 21 grade 4 glioma. Gross total resection was achieved in 26.3%, partial resection in 36.8% and 36.8% underwent biopsy only. All patients received concomitant and adjuvant chemotherapy. Fifty percent (n?=?19) started irradiation ≤17 days (median interval 12 days [range 5–17]), 50% thereafter (median 28 days [range 19–78]). More patients with grade 4 tumours were irradiated shortly after surgery. ISRT (as a continuous variable and dichotomised into two groups by the median ISRT of 18 days) did not significantly influence overall survival (OS) or progression-free survival (PFS). Higher extent of resection (EOR), lower tumour grade as well as chemotherapy with temozolomide had a significant positive impact on OS and PFS in univariate analysis and (except for the effect of temozolomide on PFS) also in multivariable analysis.

Conclusions

ISRT did not influence survival in pHGG. In view of upcoming targeted treatment options in pHGG the present data suggest that it is safe to perform molecular analyses within a 4-week timeframe before radiotherapy.

     

Monitoring of plexiform neurofibroma in children and adolescents with neurofibromatosis type 1 by [18F]FDG‐PET imaging. Is it of value in asymptomatic patients?

1 Purpose

About 10% of patients with neurofibromatosis type 1 (NF‐1) develop malignant peripheral nerve sheath tumours (MPNST) mostly arising in plexiform neurofibroma (PN); 15% of MPNST arise in children and adolescents. 2‐[¹⁸F]fluoro‐2‐deoxy‐d‐glucose ([¹⁸F]FDG)‐PET (where PET is positron emission tomography) is a sensitive method in differentiating PN and MPNST in symptomatic patients with NF‐1. This study assesses the value of [¹⁸F]FDG‐PET imaging in detecting malignant transformation in symptomatic and asymptomatic children with PN.

2 Methods

Forty‐one patients with NF‐1 and extensive PN underwent prospective [¹⁸F]FDG imaging from 2003 to 2014. Thirty‐two of the patients were asymptomatic. PET data, together with histological results and clinical course were re‐evaluated retrospectively. Maximum standardised uptake values (SUVmax) and lesion‐to‐liver ratio were assessed.

3 Results

A total of 104 examinations were performed. Mean age at first PET was 13.5 years (2.6–22.6). Eight patients had at least one malignant lesion; four of these patients were asymptomatic. Two of four symptomatic patients died, while all patients with asymptomatic malignant lesions are alive. All malignant tumours could be identified by PET imaging in both symptomatic and asymptomatic patients. All lesions judged as benign by [¹⁸F]FDG imaging and clinical judgment were either histologically benign if removed or remained clinically silent during follow‐up. SUVmax of malignant and benign lesions overlapped, but no malignant lesion showed FDG uptake ≤3.15. Asymptomatic malignant lesions were detected with a sensitivity of 100%, a negative predictive value of 100% and a specificity of 45.1%.

4 Conclusion

Malignant transformation of PN also occurs in asymptomatic children and adolescents. Detection of MPNST at early stages could increase the possibility of oncologically curative resections.     

How can we optimize the long-term outcome in children with intracranial cavernous malformations? A single-center experience of 61 cases

Neurosurgical Review - The objective is to provide a treatment algorithm for pediatric patients with intracranial cavernous malformations (CMs) based on our experience....     

Safety of Ommaya reservoirs in children with brain tumors: a 20-year experience with 5472 intraventricular drug administrations in 98 patients

The Ommaya reservoir facilitates repetitive delivery of drugs into the CSF and is a pharmacologically rational system for intrathecal chemotherapy. Because previous studies have found a high rate of infection and other complications we herein studied our experience with this device. Between 1993 and 2013, 98 children with brain tumors aged 3 months to 21 years (38 ≤ 3 years) had an Ommaya reservoir placed. All patients received perioperative antibiotics. Only specially trained personnel that followed standardized guidelines were allowed to access the reservoir. As of April 2014, 5,472 chemotherapy instillations were performed amounting to a median of 36 deliveries (2–280) per reservoir. Ommaya reservoirs were present for 199,956 days and a median of 1,336 days per device. Median survival of the 52 patients still alive is 7.5 years. Only one patient developed an Ommaya reservoir infection (1 %) that could be temporarily sterilized but eventually required Ommaya reservoir explantation. Early complications related to Ommaya reservoir placement occurred in two patients, in one catheter malposition was corrected intraoperatively and in the other kinking of the catheter at the burr-hole required minor surgical correction. Two delayed complications requiring surgical revision included malpositioning of the catheter tip after rapid shrinkage of the ventricles and disconnection of the ventricular catheter after 24 accesses. No leucodystrophic changes occurred along the catheter track. In conclusion, Ommaya reservoirs are safe and complications infrequent providing that all personnel involved in implanting and subsequently accessing the device are specially trained and pay meticulous attention to strict aseptic conditions.     

Expressional pattern of chaperones in neuronal, glial, amnion, mesothelial, and bronchial epithelial cell lines

Although literature is abundant on expression of individual heat shock proteins (HSPs) and molecular chaperones, no comprehensive information is given on their expressional pattern. The aim of our study was therefore to study expressional differences between several cell types that may provide evidence for the types of HSPs and chaperones that may be operating in the corresponding lineages. For this purpose neuronal (HCN-2), glial (SVG-p12), amnion, mesothelial (Met-5A), and bronchial epithelial (16HBE14o(-)) cell lines were grown, harvested, and protein was separated on two-dimensional electrophoresis with subsequent in-gel digestion and identification of protein spots by MALDI-MS and specific software. A series of 29 high abundance HSPs and chaperones were unambiguously identified altogether. We observed distinct expressional patterns and although overlapping, there was an apparent paucity of HSPs and chaperones in bronchial epithelial and mesothelial cells. We learn from this study that individual cell lines express and may use different HSP and chaperones systems and strategies. Specific functions of cells may be responsible as well as the presence of protein specific chaperones, although we cannot rule out that cell culture conditions were at least in part responsible for the different expressional patterns.