Emma R. Woodward

Germline SDHB mutations and familial renal cell carcinoma.

Familial renal cell carcinoma (RCC) is a heterogeneous disorder that is most commonly caused by germline mutations in the VHL, MET, and FLCN genes or by constitutional chromosome 3 translocations. However, for many patients with familial RCC, the genetic basis of the disease is undefined. We investigated whether germline mutations in fumarate hydratase (FH) or succinate dehydrogenase subunit genes (SDHB, SDHC, SDHD) were associated with RCC susceptibility in 68 patients with no clinical evidence of an RCC susceptibility syndrome. No mutations in FH, SDHC, or SDHD were identified in probands, but 3 of the 68 (4.4%) probands had a germline SDHB mutation. Patients with a germline SDHB mutation presented with familial RCC (n = 1) or bilateral RCC (n = 2) and no personal or family history of pheochromocytoma or head and neck paraganglioma. Age at diagnosis of RCC in SDHB mutation carriers ranged from 24 to 73 years. These findings 1) demonstrate that patients with suspected inherited RCC should be examined for germline SDHB mutations, 2) suggest that all identified SDHB mutation carriers should be offered surveillance for RCC, and 3) provide a further link between familial RCC and activation of hypoxic-gene response pathways.

Tumor Risks and Genotype-Phenotype-Proteotype Analysis in 358 Patients With Germline Mutations in SDHB and SDHD

Succinate dehydrogenase B (SDHB) and D (SDHD) subunit gene mutations predispose to adrenal and extraadrenal pheochromocytomas, head and neck paragangliomas (HNPGL), and other tumor types. We report tumor risks in 358 patients with SDHB (n=295) and SDHD (n=63) mutations. Risks of HNPGL and pheochromocytoma in SDHB mutation carriers were 29% and 52%, respectively, at age 60 years and 71% and 29%, respectively, in SDHD mutation carriers. Risks of malignant pheochromocytoma and renal tumors (14% at age 70 years) were higher in SDHB mutation carriers; 55 different mutations (including a novel recurrent exon 1 deletion) were identified. No clear genotype–phenotype correlations were detected for SDHB mutations. However, SDHD mutations predicted to result in loss of expression or a truncated or unstable protein were associated with a significantly increased risk of pheochromocytoma compared to missense mutations that were not predicted to impair protein stability (most such cases had the common p.Pro81Leu mutation). Analysis of the largest cohort of SDHB/D mutation carriers has enhanced estimates of penetrance and tumor risk and supports in silicon protein structure prediction analysis for functional assessment of mutations. The differing effect of the SDHD p.Pro81Leu on HNPGL and pheochromocytoma risks suggests differing mechanisms of tumorigenesis in SDH‐associated HNPGL and pheochromocytoma. Hum Mutat 31:41–51, 2010.

Germline SDHD mutation in familial phaeochromocytoma

The genetic basis for familial phaeochromocytoma is unknown in many cases. Since the disorder has been reported in some cases of familial head and neck paraganglioma, which is caused by a mutation in the gene encoding succinate dehydrogenase complex subunit D (SDHD), we investigated this gene in kindreds with familial phaeochromocytoma. A germline SDHD frameshift mutation was identified in a two-generation family consisting of four children with phaeochromocytoma, but somatic mutations were not detected in 24 sporadic phaeochromocytoma tumours. Germline SDHD mutation analysis should be done in individuals with familial, multiple, or early-onset phaeochromocytomas even if a personal or family history of head and neck paraganglioma is absent.

Penetrance estimates for BRCA1 and BRCA2 based on genetic testing in a Clinical Cancer Genetics service setting: Risks of breast/ovarian cancer quoted should reflect the cancer burden in the family

BackgroundThe identification of a BRCA1 or BRCA2 mutation in familial breast cancer kindreds allows genetic testing of at risk relatives. However, considerable controversy exists regarding the cancer risks in women who test positive for the family mutation.MethodsWe reviewed 385 unrelated families (223 with BRCA1 and 162 with BRCA2 mutations) ascertained through two regional cancer genetics services. We estimated the penetrance for both breast and ovarian cancer in female mutation carriers (904 proven mutation carriers – 1442 females in total assumed to carry the mutation) and also assessed the effect on penetrance of mutation position and birth cohort.ResultsBreast cancer penetrance to 70 and to 80 years was 68% (95%CI 64.7–71.3%) and 79.5% (95%CI 75.5–83.5%) respectively for BRCA1 and 75% (95%CI 71.7–78.3%) and 88% (95%CI 85.3–91.7%) for BRCA2. Ovarian cancer risk to 70 and to 80 years was 60% (95%CI 65–71%) and 65% (95%CI 75–84%) for BRCA1 and 30% (95%CI 25.5–34.5%) and 37% (95%CI 31.5–42.5%) for BRCA2. These risks were borne out by a prospective study of cancer in the families and genetic testing of unaffected relatives. We also found evidence of a strong cohort effect with women born after 1940 having a cumulative risk of 22% for breast cancer by 40 years of age compared to 8% in women born before 1930 (p = 0.0005).ConclusionIn high-risk families, selected in a genetics service setting, women who test positive for the familial BRCA1/BRCA2 mutation are likely to have cumulative breast cancer risks in keeping with the estimates obtained originally from large families. This is particularly true for women born after 1940.

Phenocopies in BRCA1 and BRCA2 families: Evidence for modifier genes and implications for screening?

Background: The identification of BRCA1 and BRCA2 mutations in familial breast cancer kindreds allows genetic testing of at-risk relatives. Those who test negative are usually reassured and additional breast cancer surveillance is discontinued. However, we postulated that in high-risk families, such as those seen in clinical genetics centres, the risk of breast cancer might be influenced not only by the BRCA1/BRCA2 mutation but also by modifier genes. One manifestation of this would be the presence of phenocopies in BRCA1/BRCA2 kindreds. Methods: 277 families with pathogenic BRCA1/BRCA2 mutations were reviewed and 28 breast cancer phenocopies identified. The relative risk of breast cancer in those testing negative was assessed using incidence rates from our cancer registry based on local population. Results: Phenocopies constituted up to 24% of tests on women with breast cancer after the identification of the mutation in the proband. The standardised incidence ratio for women who tested negative for the BRCA1/BRCA2 family mutation was 5.3 for all relatives, 5.0 for all first-degree relatives (FDRs) and 3.2 (95% confidence interval 2.0 to 4.9) for FDRs in whose family all other cases of breast and ovarian cancer could be explained by the identified mutation. 13 of 107 (12.1%) FDRs with breast cancer and no unexplained family history tested negative. Conclusion: In high-risk families, women who test negative for the familial BRCA1/BRCA2 mutation have an increased risk of breast cancer consistent with genetic modifiers. In light of this, such women should still be considered for continued surveillance.

Annual surveillance by CA125 and transvaginal ultrasound for ovarian cancer in both high-risk and population risk women is ineffective.

Objective  To assess the efficacy of annual CA125 and transvaginal ultrasound (TVU) scan as surveillance for ovarian cancer.

Germline FH Mutations Presenting With Pheochromocytoma

CONTEXT At least a third of the patients with pheochromocytoma (PCC) or paraganglioma (PGL) harbor an underlying germline mutation in a known PCC/PGL gene. Mutations in genes (SDHB, SDHD, SDHC, and SDHA) encoding a component of the tricarboxylic acid cycle, succinate dehydrogenase (SDH), are a major cause of inherited PCC and PGL. SDHB mutations are also, albeit less frequently, associated with inherited renal cell carcinoma. Inactivation of SDH and another tricarboxylic acid cycle component, fumarate hydratase (FH), have both been associated with abnormalities of cellular metabolism, responsible for the activation of hypoxic gene response pathways and epigenetic alterations (eg, DNA methylation). However, the clinical phenotype of germline mutations in SDHx genes and FH is usually distinct, with FH mutations classically associated with hereditary cutaneous and uterine leiomyomatosis and renal cell carcinoma, although recently an association with PCC/PGL has been reported. OBJECTIVE AND DESIGN To identify potential novel PCC/PGL predisposition genes, we initially undertook exome resequencing studies in a case of childhood PCC, and subsequently FH mutation analysis in a further 71 patients with PCC, PGL, or head and neck PGL. RESULTS After identifying a candidate FH missense mutation in the exome study, we then detected a further candidate missense mutation (p.Glu53Lys) by candidate gene sequencing. In vitro analyses demonstrated that both missense mutations (p.Cys434Tyr and p.Glu53Lys) were catalytically inactive. CONCLUSIONS These findings 1) confirm that germline FH mutations may present, albeit rarely with PCC or PGL; and 2) extend the clinical phenotype associated with FH mutations to pediatric PCC.

A Comprehensive Next Generation Sequencing–Based Genetic Testing Strategy To Improve Diagnosis of Inherited Pheochromocytoma and Paraganglioma

CONTEXT Pheochromocytomas and paragangliomas are notable for a high frequency of inherited cases, many of which present as apparently sporadic tumors. OBJECTIVE The objective of this study was to establish a comprehensive next generation sequencing (NGS)-based strategy for the diagnosis of patients with pheochromocytoma and paraganglioma by testing simultaneously for mutations in MAX, RET, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127, and VHL. DESIGN After the methodology for the assay was designed and established, it was validated on DNA samples with known genotype and then patients were studied prospectively. SETTING The study was performed in a diagnostic genetics laboratory. PATIENTS DNA samples from 205 individuals affected with adrenal or extraadrenal pheochromocytoma/head and neck paraganglioma (PPGL/HNPGL) were analyzed. A proof-of-principle study was performed using 85 samples known to contain a variant in 1 or more of the genes to be tested, followed by prospective analysis of an additional 120 samples. MAIN OUTCOME MEASURES We assessed the ability to use an NGS-based method to perform comprehensive analysis of genes implicated in inherited PPGL/HNPGL. RESULTS The proof-of-principle study showed that the NGS assay and analysis gave a sensitivity of 98.7%. A pathogenic mutation was identified in 16.6% of the prospective analysis cohort of 120 patients. CONCLUSIONS A comprehensive NGS-based strategy for the analysis of genes associated with predisposition to PPGL and HNPGL was established, validated, and introduced into diagnostic service. The new assay provides simultaneous analysis of 9 genes and allows more rapid and cost-effective mutation detection than the previously used conventional Sanger sequencing-based methodology.

Parity and breast cancer risk among BRCA1 and BRCA2 mutation carriers

IntroductionIncreasing parity and age at first full-term pregnancy are established risk factors for breast cancer in the general population. However, their effects among BRCA1 and BRCA2 mutation carriers is still under debate. We used retrospective data on BRCA1 and BRCA2 mutation carriers from the UK to assess the effects of parity-related variables on breast cancer risk.MethodsThe data set included 457 mutation carriers who developed breast cancer (cases) and 332 healthy mutation carriers (controls), ascertained through families seen in genetic clinics. Hazard ratios were estimated by using a weighted cohort approach.ResultsParous BRCA1 and BRCA2 mutation carriers were at a significantly lower risk of developing breast cancer (hazard ratio 0.54, 95% confidence interval 0.37 to 0.81; p = 0.002). The protective effect was observed only among carriers who were older than 40 years. Increasing age at first live birth was associated with an increased breast cancer risk among BRCA2 mutation carriers (p trend = 0.002) but not BRCA1 carriers. However, the analysis by age at first live birth was based on small numbers.ConclusionThe results suggest that the relative risks of breast cancer associated with parity among BRCA1 and BRCA2 mutation carriers may be similar to those in the general population and that reproductive history may be used to improve risk prediction in carriers.

Familial Non-VHL Clear Cell (Conventional) Renal Cell Carcinoma: Clinical Features, Segregation Analysis, and Mutation Analysis of FLCN

Purpose: Familial renal cell carcinoma (RCC) is genetically heterogeneous. The most common histopathologic subtype of sporadic and familial RCC is clear cell (cRCC) and von Hippel-Lindau (VHL) disease is the most common cause of inherited cRCC. Familial cRCC may also be associated with chromosome 3 translocations and has recently been described in patients with Birt-Hogg-Dube (BHD) syndrome, caused by germline FLCN mutation. Fewer than 20 kindreds with familial cRCC without VHL disease or a constitutional translocation have been described. The purpose of this investigation was to define the clinical and genetic features of familial non-VHL cRCC (FcRCC) and to evaluate whether unrecognized BHD syndrome might be present in patients with apparent nonsyndromic RCC susceptibility. Experimental Design: We analyzed the clinical features of, and undertook segregation analysis in, 60 kindreds containing two or more cases of RCC (at least one confirmed case of cRCC) and no evidence of an RCC susceptibility syndrome. We also undertook FLCN analysis to evaluate whether unrecognized BHD syndrome might be present in 69 patients with apparent nonsyndromic RCC susceptibility. Results: FcRCC was characterized by an earlier age at onset than sporadic cases and more frequent occurrence of bilateral or multicentric tumors. Segregation analysis showed autosomal dominant inheritance with sex- and age-dependent penetrance. A germline FLCN mutation was detected in 3 of 69 (4.3%) patients with apparent nonsyndromic RCC susceptibility. Conclusions: We describe the clinical and genetic features of the largest series of FcRCC and recommend these patients be offered FLCN analysis, in addition to constitutional cytogenetic and VHL analysis.