Payal P. Khincha

Risks of first and subsequent cancers among TP53 mutation carriers in the National Cancer Institute Li-Fraumeni syndrome cohort.

Li‐Fraumeni syndrome (LFS) is an autosomal dominant cancer predisposition syndrome characterized by a very high lifetime cancer risk and an early age at diagnosis of a wide cancer spectrum. Precise estimates for the risk of first and subsequent cancers are lacking.

Genomic characterization of the inherited bone marrow failure syndromes.

The inherited bone marrow failure syndromes (IBMFS) are a set of clinically related yet heterogeneous disorders in which at least one hematopoietic cell lineage is significantly reduced. Many of the IBMFS have notably increased cancer risks, as well as other physical findings. Highly penetrant germline mutations in key pathways, such as DNA repair, telomere biology, or ribosomal biogenesis, are causative of Fanconi anemia (FA), dyskeratosis congenita (DC), and Diamond-Blackfan anemia (DBA), respectively. Next-generation sequencing (NGS) generally refers to high-throughput, large-scale sequencing technologies and is being used more frequently to understand disease etiology. In the IBMFS, NGS has facilitated the discovery of germline mutations that cause thrombocytopenia absent radii syndrome (TAR), a subset of DC and DBA, and other uncharacterized, but related, disorders. Panels of large numbers of genes are being used to molecularly characterize patients with IBMFS, such as FA and DBA. NGS is also accelerating the discovery of the genetic etiology of previously unclassified IBMFS. In this review, we will highlight recent studies that have employed NGS to ascertain the genetic etiology of IBMFS, namely, FA, DC, DBA, and TAR, and discuss the translational utility of these findings.

Response to Androgen Therapy in Patients with Dyskeratosis Congenita

Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome and telomere biology disorder characterized by dysplastic nails, reticular skin pigmentation and oral leucoplakia. Androgens are a standard therapeutic option for bone marrow failure in those patients with DC who are unable to undergo haematopoietic stem cell transplantation, but there are no systematic data on its use in those patients. We evaluated haematological response and side effects of androgen therapy in 16 patients with DC in our observational cohort study. Untreated DC patients served as controls. Seventy percent of treated DC patients had a haematological response with red blood cell and/or platelet transfusion independence. The expected age‐related decline in telomere length was noted in androgen‐treated patients. All treated DC patients had at least one significant lipid abnormality. Additional treatment‐related findings included a significant decrease in thyroid binding globulin, accelerated growth in pre‐pubertal children and splenic peliosis in two patients. Liver enzymes were elevated in both androgen‐treated and untreated patients, suggesting underlying liver involvement in DC. This study suggests that androgen therapy can be effectively used to treat bone marrow failure in DC, but that side effects need to be closely monitored.

Novel and known ribosomal causes of Diamond-Blackfan anaemia identified through comprehensive genomic characterisation

Background Diamond-Blackfan anaemia (DBA) is an inherited bone marrow failure syndrome (IBMFS) characterised by erythroid hypoplasia. It is associated with congenital anomalies and a high risk of developing specific cancers. DBA is caused predominantly by autosomal dominant pathogenic variants in at least 15 genes affecting ribosomal biogenesis and function. Two X-linked recessive genes have been identified. Objectives We aim to identify the genetic aetiology of DBA. Methods Of 87 families with DBA enrolled in an institutional review board-approved cohort study (ClinicalTrials.gov Identifier:NCT00027274), 61 had genetic testing information available. Thirty-five families did not have a known genetic cause and thus underwent comprehensive genomic evaluation with whole exome sequencing, deletion and CNV analyses to identify their disease-associated pathogenic variant. Controls for functional studies were healthy mutation-negative individuals enrolled in the same study. Results Our analyses uncovered heterozygous pathogenic variants in two previously undescribed genes in two families. One family had a non-synonymous variant (p.K77N) in RPL35; the second family had a non-synonymous variant (p. L51S) in RPL18. Both of these variants result in pre-rRNA processing defects. We identified heterozygous pathogenic variants in previously known DBA genes in 16 of 35 families. Seventeen families who underwent genetic analyses are yet to have a genetic cause of disease identified. Conclusions Overall, heterozygous pathogenic variants in ribosomal genes were identified in 44 of the 61 families (72%). De novo pathogenic variants were observed in 57% of patients with DBA. Ongoing studies of DBA genomics will be important to understand this complex disorder.

Baseline Surveillance in Li-Fraumeni Syndrome Using Whole-Body Magnetic Resonance Imaging: A Meta-analysis

Importance Guidelines for clinical management in Li-Fraumeni syndrome, a multiple-organ cancer predisposition condition, are limited. Whole-body magnetic resonance imaging (WBMRI) may play a role in surveillance of this high-risk population. Objective To assess the clinical utility of WBMRI in germline TP53 mutation carriers at baseline. Data Sources Clinical and research surveillance cohorts were identified through the Li-Fraumeni Exploration Research Consortium. Study Selection Cohorts that incorporated WBMRI for individuals with germline TP53 mutations from January 1, 2004, through October 1, 2016, were included. Data Extraction and Synthesis Data were extracted by investigators from each cohort independently and synthesized by 2 investigators. Random-effects meta-analysis methods were used to estimate proportions. Main Outcomes and Measures The proportions of participants at baseline in whom a lesion was detected that required follow-up and in whom a new primary malignant neoplasm was detected. Results A total of 578 participants (376 female [65.1%] and 202 male [34.9%]; mean [SD] age, 33.2 [17.1] years) from 13 cohorts in 6 countries were included in the analysis. Two hundred twenty-five lesions requiring clinical follow-up were detected by WBMRI in 173 participants. Sixty-one lesions were diagnosed in 54 individuals as benign or malignant neoplasms. Overall, 42 cancers were identified in 39 individuals, with 35 new localized cancers treated with curative intent. The overall estimated detection rate for new, localized primary cancers was 7% (95% CI, 5%-9%). Conclusions and Relevance These data suggest clinical utility of baseline WBMRI in TP53 germline mutation carriers and may form an integral part of baseline clinical risk management in this high-risk population.

Neonatal manifestations of inherited bone marrow failure syndromes

The inherited bone marrow failure syndromes (IBMFS) are a rare yet clinically important cause of neonatal hematological and non-hematological manifestations. Many of these syndromes, such as Fanconi anemia, dyskeratosis congenita and Diamond-Blackfan anemia, confer risks of multiple medical complications later in life, including an increased risk of cancer. Some IBMFS may present with cytopenias in the neonatal period whereas others may present only with congenital physical abnormalities and progress to pancytopenia later in life. A thorough family history and detailed physical examination are integral to the work-up of any neonate in whom there is a high index of suspicion for an IBMFS. Correct detection and diagnosis of these disorders is important for appropriate long-term medical surveillance and counseling not only for the patient but also for appropriate genetic counselling of their families regarding recurrence risks in future children and generations.

The limitations of qPCR telomere length measurement in diagnosing dyskeratosis congenita.

Telomere length <1st percentile‐for‐age in leukocyte subsets by flow cytometry with fluorescence in situ hybridization (flow FISH) is highly sensitive and specific in diagnosing patients with dyskeratosis congenita (DC), a telomere biology disorder.

Effect of pre-analytic variables on the reproducibility of qPCR relative telomere length measurement

Telomeres, long nucleotide repeats and a protein complex at chromosome ends, shorten with each cell division and are susceptible to oxidative damage. Quantitative PCR (qPCR) is a widely-used technique to measure relative telomere length (RTL) in DNA samples but is challenging to optimize and significant lab-to-lab variability has been reported. In this study, we evaluated factors that may contribute to qPCR RTL measurement variability including DNA extraction methods, methods used for removing potential residual PCR inhibitors, sample storage conditions, and sample location in the PCR plate. Our results show that the DNA extraction and purification techniques, as well as sample storage conditions introduce significant variability in qPCR RTL results. We did not find significant differences in results based on sample location in the PCR plate or qPCR instrument used. These data suggest that lack of reproducibility in published association studies of RTL could be, in part, due to methodological inconsistencies. This study illustrates the importance of uniform sample handling, from DNA extraction through data generation and analysis, in using qPCR to determine RTL.

Pulmonary arteriovenous malformations: an uncharacterised phenotype of dyskeratosis congenita and related telomere biology disorders

The telomere biology disorder (TBD) dyskeratosis congenita (DC) is a multisystem inherited bone marrow failure syndrome and cancer predisposition syndrome caused by germline mutations in telomere biology genes (DKC1, TINF2, TERC, TERT, NOP10, NHP2, CTC1, WRAP53, ACD, RTEL1 and PARN). The classic triad of reticular skin pigmentation, dysplastic nails and oral leukoplakia is diagnostic of DC [1, 2]. Leukocyte telomere lengths less than the first percentile for age measured by flow cytometry with fluorescence in situ hybridisation are consistent with DC in the presence of other phenotypic features [3]. Pulmonary fibrosis, a known complication of DC/TBD, occurs in ≥20% of patients [1]. Pulmonary arteriovenous malformations (PAVMs) in DC have been previously described in case reports or small case series in the context of hepatopulmonary syndrome (HPS) [4–9]. Presenting features of PAVMs may overlap with those of pulmonary fibrosis, including dyspnoea, orthopnoea, platypnoea, cyanosis and digital clubbing. HPS is described as pulmonary vascular dilatation due to liver disease of any cause (cirrhotic/noncirrhotic with/without portal hypertension), leading to deficient arterial oxygenation [10]. PAVMs are underrecognised in telomere biology disorders and present diagnostic and therapeutic challenges http://ow.ly/2lPc304eu0t

Investigation of chromosome X inactivation and clinical phenotypes in female carriers of DKC1 mutations.

Dyskeratosis congenita (DC) is an inherited bone marrow failure and cancer susceptibility syndrome caused by germline mutations in telomere biology genes. Germline mutations in DKC1, which encodes the protein dyskerin, cause X‐linked recessive DC. Because of skewed X‐chromosome inactivation, female DKC1 mutation carriers do not typically develop clinical features of DC. This study evaluated female DKC1 mutation carriers with DC‐associated phenotypes to elucidate the molecular features of their mutations, in comparison with unaffected carriers and mutation‐negative female controls. All female DKC1 mutation carriers had normal leukocyte subset telomere lengths and similarly skewed X‐inactivation in multiple tissue types, regardless of phenotype. We observed dyskerin expression, telomerase RNA accumulation, and pseudouridylation present in all mutation carriers at levels comparable to healthy wild‐type controls. Our study suggests that mechanisms in addition to X chromosome inactivation, such as germline mosaicism or epigenetics, may contribute to DC‐like phenotypes present in female DKC1 mutation carriers. Future studies are warranted to understand the molecular mechanisms associated with the phenotypic variability in female DKC1 mutation carriers, and to identify those at risk of disease. Am. J. Hematol. 91:1215–1220, 2016.