Abstract PD1-04: The contribution of rare variants, polygenic risk, and novel candidate genes to the hereditary risk of breast cancer in a large cohort of breast cancer families

Background: Identifying the missing hereditary factors underlying the familial risk of breast cancer could have a major and immediate impact on managing the breast cancer risk for these families.

Methods: We identified candidate breast cancer predisposition genes through whole exome sequencing of BRCAx families and subsequently sequenced up to 1325 genes, along with 76 common low penetrance variants associated with breast cancer, in index cases from 6,000 BRCAx families and 6,000 cancer free women (ethnically matched on principal component analysis).

Results: The role of recently described (PALB2) or suspected (MRE11A) moderately penetrant genes was confirmed. Conversely, the size of the cohort means that the absence of enrichment for loss of function (LoF mutations) provides strong evidence against other reported breast cancer genes (BRIP1, RINT1, RECQL). For further moderate risk variants (in CHEK2, ATM, BRCA2) we observed significant risk modification based on the polygenic risk score (PRS - calculated from the common variant data), with the risk restricted to the co-occurrence of the rare variant and high PRS. Novel candidate genes were identified based on LoF mutations, including NTHL1 (38 cases versus 15 controls, OR 2.5 p=0.002): a member of the base excision repair (BER) pathway. DNA sequencing of the breast carcinomas from 17 heterozygous NTHL1 mutation carriers revealed a strong bias towards a C:G>T:A (C>T) transitions, consistent with a BER defect, which confirmed the recent findings in colorectal carcinomas from bi-allelic NTHL1 mutation carriers. This data extends the cancer predisposition phenotype of NTHL1 to heterozygous carriers. In addition to NTHL1, there are a large number of candidate genes where the ratio of LoF mutations in cases versus controls indicates that they may convey an actionable level of risk; 46 genes (519 families) meet the basic criteria of multiple LoF variants and an OR >2 for cases versus controls – including previously proposed breast cancer genes MRE11A, BLM, MLH1, MYH, FANCD2 and functionally plausible candidates such as MLH3, PARP2 and ATR. Collectively the OR of breast cancer for LoF mutations in this group of genes is 3.3 (95% CI 2.7-3.9, P=3.5x10-41).

Conclusion: Our data shows that the effect of rare variation in established and novel breast cancer genes, along with consideration of the background polygenic risk, together explains a substantial component of the heritable risk of breast cancer in our cohort.

Citation Format: Campbell IG, Li N, Rowley S, Goode D, Devereux L, McInerny S, Grewal N, Lee A, Trainer A, Wong-Brown M, Scott R, Gorringe K, James P. The contribution of rare variants, polygenic risk, and novel candidate genes to the hereditary risk of breast cancer in a large cohort of breast cancer families [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD1-04.

Abstract PD1-07: Population genetic testing for breast cancer susceptibility

Background. Germline mutations in certain genes account for a large proportion of inherited risk for breast and ovarian cancer. The identification of asymptomatic mutation carriers could significantly reduce the incidence of these diseases as active risk management can dramatically reduce the risk of developing cancer.

In most countries, identifying high-risk individuals is based on their family history. In general, a family is first identified because one family member develops cancer and, because of high-risk indicators is referred to a familial cancer centre (FCC). However, current data suggests that many BRCA1 or BRCA2 mutation carriers do not have a remarkable history of cancer in a close relative. Population-based genetic testing would be a far more effective strategy for identification of at-risk individuals. To test the feasibility of such a strategy we are conducting a population genetic testing trial for actionable mutations in 11 breast/ovarian cancer predisposition genes (BRCA1, BRCA2, PALB2, ATM, CDH1, PTEN, STK11, TP53, BRIP1, RAD51C, RAD51D) among 15,000 healthy women from the Australian population.

Methods. All subjects are female participants in the LifePool cohort (www.lifepool.org) who had no personal history of breast or ovarian cancer at the time of DNA collection. Participants found to carry an actionable germline mutation were notified by letter with an invitation to contact the PeterMac telephone genetic counselling service for further information and/or also invited for counselling at an FCC. Only participants with an actionable mutation were notified of their genetic testing result.

Results. Of the 5,557 women tested to date, 40 (0.72%) were carriers of mutations that are currently actionable in the Australian context (BRCA1 n=7, BRCA2 n=15, PALB2 n=15, ATM n=3). All 40 women accepted the invitation to attend a familial cancer centre for formal predictive testing. Less than 20% of the women would have met the minimum threshold for clinical genetic testing under current guidelines. A further 16 participants (0.29%) carried mutations in BRIP1, RAD51C and RAD51D but were not notified of the result as these genes are not currently actionable in Australia. No mutations were identified in CDH1, PTEN, STK11 or TP53.

Conclusions. A relatively large proportion of cancer free-women from Australia carry high-risk mutations in BRCA genes and subsequent uptake of clinical genetic testing was very high. Population-based genetic testing is well accepted and can identify a much larger proportion of the at risk-population than contemporary family history based approaches.

Citation Format: Campbell IG, Rowley S, Devereux L, McInerny S, Grewal N, Young M-A, Lee A, Trainer A, James P. Population genetic testing for breast cancer susceptibility [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD1-07.

Pathogenesis of aortic wall complications in Marfan syndrome

BACKGROUND

Patients with Marfan (MFS) syndrome and patients with a bicuspid aortic valve (BAV) are more prone to develop aortic dilation and dissection compared to persons with a tricuspid aortic valve (TAV). To elucidate potential common as well as distinct pathways of clinical relevance, we compared the histopathological substrates of aortic pathology.

PATIENT AND METHODS

Ascending aortic wall specimen were divided in five groups: BAV (n=36) and TAV (n=23) without and with dilation and non-dilated MFS (n=8). We performed routine histology to study aortic wall features based on the aortic consensus statement. Immunohistological markers for vascular smooth muscle cell (VSMC) maturation, and expression of fibrillin-1 were additionally investigated for the underlying pathogenesis.

RESULTS

On basis of the routine histology the aorta in MFS was similar to the aorta in dilated TAVs (overall medial degeneration, elastic fiber fragmentation, loss and disorganization, , and VSMC nuclei loss). The other markers aided in clustering the MFS and BAV patients with a significantly lower fibrillin-1 expression as compared to the TAVs (p<0.05), a lower level of differentiated VSMC markers (p<0.05) and elastic fiber thinning.

CONCLUSIONS

Pathogenesis of aortopathy in MFS overlaps with mechanisms seen in BAV and TAV, leading to a so called double hit hypothesis for aortic complications in MFS. The ascending aortic wall in MFS is immature with undifferentiated VSMCs and low levels of fibrillin-1. The immature media becomes even more vulnerable for aortopathy due to other degenerative features which develop probably as a direct consequence of the fibrillin-1 mutation.

The extent of the raphe in bicuspid aortic valves is associated with aortic regurgitation and aortic root dilatation

Background

The clinical course of bicuspid aortic valves (BAVs) is variable. Data on predictors of aortopathy and valvular dysfunction mainly focus on valve morphology.

Aim

To determine whether the presence and extent of the raphe (fusion site of valve leaflets) is associated with the degree of aortopathy and valvular dysfunction in patients with isolated BAV and associated aortic coarctation (CoA).

Methods

Valve morphology and aortic dimensions of 255 BAV patients were evaluated retrospectively by echocardiography.

Results

BAVs with a complete raphe had a significantly higher prevalence of valve dysfunction (especially aortic regurgitation) than BAVs with incomplete raphes (82.9 vs. 66.7 %, p = 0.01). Type 1A BAVs (fusion of right and left coronary leaflets) and complete raphe had larger aortic sinus diameters compared with the rest of the population (37.74 vs. 36.01, p = 0.031). Patients with CoA and type 1A BAV had significantly less valve regurgitation (13.6 vs. 55.8 %, p < 0.001) and smaller diameters of the ascending aorta (33.7 vs. 37.8 mm, p < 0.001) and aortic arch (25.8 vs. 30.2 mm, p < 0.001) than patients with isolated BAV.

Conclusions

Type 1A BAV with complete raphe is associated with more aortic regurgitation and root dilatation. The majority of CoA patients have incomplete raphes, associated with smaller aortic root diameters and less valve regurgitation.

Histopathology of aortic complications in bicuspid aortic valve versus Marfan syndrome: relevance for therapy?

Patients with bicuspid aortic valve (BAV) and patients with Marfan syndrome (MFS) are more prone to develop aortic dilation and dissection compared to persons with a tricuspid aortic valve (TAV). To elucidate potential common and distinct pathways of clinical relevance, we compared the histopathological substrates of aortopathy. Ascending aortic wall biopsies were divided in five groups: BAV (n = 36) and TAV (n = 23) without and with dilation and non-dilated MFS (n = 8). General histologic features, apoptosis, the expression of markers for vascular smooth muscle cell (VSMC) maturation, markers predictive for ascending aortic dilation in BAV, and expression of fibrillin-1 were investigated. Both MFS and BAV showed an altered distribution and decreased fibrillin-1 expression in the aorta and a significantly lower level of differentiated VSMC markers. Interestingly, markers predictive for aortic dilation in BAV were not expressed in the MFS aorta. The aorta in MFS was similar to the aorta in dilated TAV with regard to the presence of medial degeneration and apoptosis, while other markers for degeneration and aging like inflammation and progerin expression were low in MFS, comparable to BAV. Both MFS and BAV aortas have immature VSMCs, while MFS and TAV patients have a similar increased rate of medial degeneration. However, the mechanism leading to apoptosis is expected to be different, being fibrillin-1 mutation induced increased angiotensin-receptor-pathway signaling in MFS and cardiovascular aging and increased progerin in TAV. Our findings could explain why angiotensin inhibition is successful in MFS and less effective in TAV and BAV patients.

Bicuspid aortic valve: phosphorylation of c-Kit and downstream targets are prognostic for future aortopathy

OBJECTIVES

The clinical course of many patients with a bicuspid aortic valve (BAV) is complicated by ascending aortic dilatation. Currently, the indication for aortic surgery is solely based on the aortic diameter and subsequently only a small proportion of BAV patients undergoing valve surgery require concomitant ascending aortic replacement based on these recommendations. Unfortunately, a substantial number of BAV patients still develop aortic dilatation in the future and would potentially benefit from a more aggressive approach towards ascending aortic replacement. We, therefore, designed this study to identify molecular biological markers in the aortic wall predictive of aortopathy in BAV.

METHODS

Ascending aortic wall specimen of BAV (n = 36) and tricuspid aortic valve (TAV) (n = 23), both without and with (>44 mm) dilatation were investigated histologically and immunohistochemically for the expression of markers for vascular remodelling [transforming growth factor (TGF)-β, phosphorylated Smad2, matrix metalloproteinase 9 (MMP9)], cellular differentiation [c-Kit, phosphorylated-c-Kit, hypoxia-inducable factor-1 alpha (HIF1α)] and haemodynamic influences on the aortic wall [endothelial nitric oxide (eNOS)].

RESULTS

All BAV patients showed significantly less inflammation (P < 0.001) and an altered intima/media ratio when compared with TAV patients. The expression of markers of a signalling pathway characteristic for cellular dedifferentiation, as exemplified by the marked expression of c-Kit, phosphorylated c-Kit and HIF1α; in the dilated BAV group was however completely comparable with only a subgroup of the non-dilated BAV (BAb), whereas the remainder of the non-dilated BAV group (BAa) was significantly distinct. This difference between the dilated BAV and BAa was further confirmed in the expression of TGF-β, phosphorylated Smad2, MMP9 and eNOS. Besides the expression pattern, similarity in the dilated BAV and BAb was also noted clinically in the most common variant of commissure position and conjoined raphe of the BAV. Based on these observations, we consider the BAb group a likely candidate for future dilatation as opposed to the BAa group.

CONCLUSIONS

Using a panel of molecular tissue markers, the non-dilated BAV patients can be divided into groups susceptible and non-susceptible to aortopathy.

Ascending aorta dilation in association with bicuspid aortic valve: a maturation defect of the aortic wall

OBJECTIVE

Patients with a bicuspid aortic valve have increased susceptibility to the development of ascending aortic dilation and dissection compared with persons with a tricuspid valve. To unravel a possible different mechanism underlying dilation in bicuspidy and tricuspidy, a comparison of the structure of the aortic wall was made.

METHODS

Ascending aortic wall biopsies were divided into 4 groups: bicuspid (n=36) and tricuspid (n=23) without and with dilation. The expression of vascular smooth muscle cell maturation markers including lamin A/C, which plays a pivotal role in smooth muscle cell differentiation, and its splicing variant progerin indicative of aging, were studied immunohistochemically. Attention was also paid to the inflammatory status.

RESULTS

There is a significant difference in the structure and maturation of the aortic wall in bicuspidy, persisting in the dilated aortic wall, presenting with a thinner intima, lower expression of α smooth muscle actin, smooth muscle 22α, calponin, and almost absent expression of smoothelin. We show for the first time significantly lowered lamin A/C expression in bicuspidy. Progerin was found to be significantly increased in the media of the dilated wall in tricuspidy, also showing increased periaortic inflammation.

CONCLUSIONS

The structure of the nondilated and dilated aortic wall in bicuspidy and tricuspidy are intrinsically different, with the latter having more aspects of aging. In bicuspidy there is a defective smooth muscle cell differentiation possibly linked to lowered lamin A/C expression. Based on this vessel wall immaturity and increased susceptibility to dilation, different diagnostic and therapeutic approaches are warranted.

Comparative in vivo evaluation of restoring severely mutilated primary anterior teeth with biological post and crown preparation and reinforced composite restoration

BACKGROUND

This study was designed to compare the success rate of biological and composite restorations when used to replace structural loss of primary anterior teeth using intracanal post for radicular support of the restoration.

MATERIALS AND METHODS

Forty-two patients aged between 3-5 years presenting with early childhood caries (ECC) received at least one or more composite and biological restorations for comparative evaluation. A total of 150 restorations were done (75 biological restorations and 75 composite restorations). The restorations were evaluated single-blind according to a modified USPHS system. Assessment of the patient's response in accepting a biological restoration, psychological impact of the restorations, view of the parents, and peer group reviews, etc. were recorded in a response sheet in presence of the child and the parents.

OBSERVATIONS AND RESULTS

In vivo clinical performance of biological post and crown restorations and intracanal reinforced composite restorations was comparable with respect to shade match, marginal discoloration, marginal integrity, surface finish, gingival health, retention, and recurrent carious lesions. The cost effectiveness of biological restorations was certainly a positive attribute.

CONCLUSION

The biological restoration presented as a cost effective, clinician friendly, less-technique sensitive, and esthetic alternative to commercially available restorative materials used for restoring deciduous teeth affected by ECC.

The effect of fissure morphology and eruption time on penetration and adaptation of pit and fissure sealants: An SEM study

This study was designed to examine the effect of fissure morphology on penetration and adaptation of fissure sealants and their relationship with the eruption time of tooth.

MATERIALS AND METHODS

One hundred and fifty extracted molars and premolars were divided into two groups on the basis of their eruption time. The two groups were further divided into five subgroups on the basis of fissure morphology. An scanning electron microscopic analysis of penetration and adaptation of sealant was done.

OBSERVATIONS AND RESULTS

V- and U-shaped fissures were found to have the maximum penetration. Penetration was very poor for I- and IK-types of fissures. No significant difference in penetration was found in relation to eruption time. Adaptation of sealant was not affected by any of the factors.

CONCLUSION

Even the well-applied sealant does not necessarily provide complete obturation of pits and fissures, thus necessitating periodical clinical observation to determine the success or potential failure of the sealant treatment.

Root canal configuration of deciduous mandibular first molars--an in vitro study

Root canal morphology of deciduous mandibular first molar was studied using roentgenographic and decalcification and clearing methods. Two groups of 15 teeth were formed. In the roentgenographic group, roots of the teeth were separated from the crown at the level of CEJ. Cut roots of the teeth were radiographed from both mesiodistal and buccolingual directions using separate IOPA films. In the decalcification and clearing group, teeth were decalcified and made transparent. Dye was injected later. The roots of the teeth were examined under 10 times for number, curvature, types and additional features of root canals. Deciduous mandibular first molar showed variability in root canal morphology. Four to five root canals were recorded. Majority of the teeth had 1-1 type of root canal anatomy, but 1-2 type anatomy was also reported. Straight, curved and S-shaped canal curvatures were recorded. Horizontal anastomosis, lateral canals and buccolingually broad root canals were also recorded.

Implementation of behaviour management techniques--how well accepted they are today

Dynamic changes in society with working parents and smaller nuclear families have brought about a sea of changes in parental attitudes and anxieties towards their children. This has affected the perception and implementation of behaviour modification techniques by the dentist. Today, the significance of Tell Show Do technique and its efficiency in behaviour modification is questionable. Insistence of parents on conscious sedation is seen to be on the rise. This study aimed to assess the change in the utilization pattern of behaviour management techniques by pediatric dentists of Punjab in the past five years along with identification of change in parental attitude towards these techniques.

A comparative study of microleakage below cemento-enamel junction using light cure and chemically cured glass ionomer cement liners

Posterior composite resins have gained considerable importance over last few years. However, improper placement techniques continue to be a prime cause of failure of these restorations. This study was done to compare the microleakage at the tooth restoration interface extending below cementoenamel junction when posterior composite restorations were placed directly in the cavity or when placed over a glass ionomer cement liner, both chemically cured and light cured. The results have shown that light cured glass ionomer when used as a liner under a composite restoration used below gingival cementum/dentin margin has the best sealing capability.

Retentive [correction of Preventive] efficacy of glass ionomer, zinc phosphate and zinc polycarboxylate luting cements in preformed stainless steel crowns: a comparative clinical study

This study was undertaken to assess the efficacy of three luting cements, namely, glass ionomer, zinc phosphate and zinc polycarboxylate in retainng the preformed stainless steel crowns in-vivo. Twenty subjects, with an indication for restoration of three primary molars with stainless steel crowns, were selected. Sixty teeth were taken up for the study, and twenty crowns were cemented with each of the three luting cements. After an eight month follow up the crowns were assessed for their presence/ absence or "rocking". Statistical analysis was done using Chi-square test. The results have shown no significant difference in retentivity of stainless steel crowns with the use of either of the three luting agents.

Complete genome sequence of Salmonella enterica serovar Typhimurium LT2

Salmonella enterica subspecies I, serovar Typhimurium (S. typhimurium), is a leading cause of human gastroenteritis, and is used as a mouse model of human typhoid fever. The incidence of non-typhoid salmonellosis is increasing worldwide, causing millions of infections and many deaths in the human population each year. Here we sequenced the 4,857-kilobase (kb) chromosome and 94-kb virulence plasmid of S. typhimurium strain LT2. The distribution of close homologues of S. typhimurium LT2 genes in eight related enterobacteria was determined using previously completed genomes of three related bacteria, sample sequencing of both S. enterica serovar Paratyphi A (S. paratyphi A) and Klebsiella pneumoniae, and hybridization of three unsequenced genomes to a microarray of S. typhimurium LT2 genes. Lateral transfer of genes is frequent, with 11% of the S. typhimurium LT2 genes missing from S. enterica serovar Typhi (S. typhi), and 29% missing from Escherichia coli K12. The 352 gene homologues of S. typhimurium LT2 confined to subspecies I of S. enterica-containing most mammalian and bird pathogens-are useful for studies of epidemiology, host specificity and pathogenesis. Most of these homologues were previously unknown, and 50 may be exported to the periplasm or outer membrane, rendering them accessible as therapeutic or vaccine targets.

D-Aspartate oxidase and D-amino acid oxidase are localised in the peroxisomes of terrestrial gastropods

D-Aspartate oxidase and D-amino acid oxidase were found in high activity in the tissues of representative species of terrestrial gastropods. Analytical subcellular fractionation demonstrated that both of these oxidases co-localised with the peroxisome markers, acyl-CoA oxidase and catalase, in the digestive gland homogenate. Electron microscopy of peak peroxisome fractions showed particles of uniform size with generally well preserved variably electron-dense matrices bounded by an apparently single limiting membrane. Many of the particles exhibited a core region of enhanced electron density. Catalase cytochemistry of peak fractions confirmed the peroxisome identity of the organelles. Peroxisome-enriched subcellular fractions were used to investigate the properties of gastropod D-aspartate oxidase and D-amino acid oxidase activities. The substrate and inhibitor specificities of the two activities demonstrated that two distinct enzymes were present analogous to, but not identical to, the equivalent mammalian peroxisomal enzymes.

Gastropod mollusc aliphatic alcohol oxidase: subcellular localisation and properties

The digestive gland and other tissues of several species of terrestrial gastropod mollusc contain an aliphatic alcohol oxidase activity (EC1.1.3.13). The enzyme is FAD dependent, consumes oxygen and generates hydrogen peroxide and the corresponding aldehyde. Saturated primary alcohols are favoured as substrates with octanol preferred with an apparent Km of 3-4 microM. The activity is clearly distinguishable from previously reported molluscan aromatic alcohol oxidase (EC1.1.3.7) on the basis of FAD dependence, sensitivity to heat treatment and high salt concentration and with regard to substrate preferences. The aliphatic alcohol oxidase is membrane associated and most likely localised to the endoplasmic reticulum. Extraction of membranes with 1% Igipal solubilises the enzyme in active form. This enzyme is a further example of an oxidase apparently restricted to molluscs.

Relationship of tongue-thrust swallowing and anterior open bite with articulation disorders: a clinical study

A Paediatric dentist may be the first person consulted for professional advice concerning children with speech problems. A positive significant relationship has been hypothesized by some authors between tongue-thrust swallowing and articulation disorders in children. This study was undertaken to find out whether any articulation disorders are associated with the habit of tongue-thrust swallowing, or is it the type of anterior bite that plays an important role in the normal or abnormal speech production in tongue-thrust swallowers. Forty subjects with tongue-thrust swallowing in the age group of 7-16 years were examined. Of these 20 had normal anterior bite while rest had anterior open bite. A word articulation test was used and word level articulation testing was done for initial, medial and final positions. The sounds tested were: Linguoalveolars, Labiodentals, Linguodentals, Linguopalatals, Bilabials and Linguovelars. The results of the study have indicated that the presence of articulation disorders is strongly associated with the anterior open bite present in tongue-thrust swallowers but a simple, direct relationship between the presence of defective consonant sounds and tongue-thrust swallowing has not been found.