It's Not All Sunshine: Non-sun-related Melanoma Risk-factors

There is increasing evidence that the behaviour of naevi and melanoma is under significant genetic and/or epigenetic control. Melanoma tumours behaves similarly all over the world. Many genes have now been implicated in melanoma risk and naevi number. Embryogenesis has also been important in the discovery of links between several neurological diseases and melanoma susceptibility. Telomere biology, which regulates cell senescence, is increasingly relevant in melanoma. Melanoma is often found in the context of family cancer syndromes and the identification of these families is important as screening for cancer will save lives. Melanoma is also one of the most immunogenic cancer as the behaviour of naevi and melanoma differ in patients with vitiligo or eczema. The search for non-sun related melanoma risk factors should continue as it is likely to lead to important discoveries which will, in turn, have an impact on therapeutic targets for this tumour.

Discoveries beyond BRCA1/2: Multigene testing in an Asian multi-ethnic cohort suspected of hereditary breast cancer syndrome in the real world

BACKGROUND

Due to historically low uptake of genetic testing, the mutational spectrum of Asians with Hereditary Breast Cancer (HBC) is not well understood. This study sought to understand the incidence and spectrum of germline mutations in Asian patients with suspected HBC in a clinic setting.

METHODS

1056 patients with suspected HBC were seen in our Cancer (CA) Genetics Clinic from 2000-2017, of which 460 underwent genetic testing.

RESULTS

Of 460 probands tested, 93% were female, 61% Chinese, 90% had prior CA, with 19% (77/414) having ≥2 primary CA. Median age at CA-diagnosis was 43y (17-83); 70% had Breast CA (BC) and 25% Ovarian CA (OC). 34% had young-onset BC, 8% bilateral BC, and 4% BC/OC. Majority had family history of BC (53%) or OC (20%). 57% underwent multigene testing (14-49 genes), 34% targeted testing, and 8% predictive testing. 30% were found to have a pathogenic mutation: 80% in BRCA1/2 (8 novel mutations noted). Of 33 non-BRCA1/2 pathogenic mutations detected, 61% were in 11 BC genes while 39% were in non-BC genes suggestive of alternative CA syndromes. Testing beyond BRCA1/2 impacted management for 15.9% (22/138) of carriers, but extensive testing identified variants of uncertain significance (VUS) in up to 44.5% of probands. Restricting multigene panel testing to a guideline-based 20-gene panel including Lynch Syndrome genes was found to be most optimal, detecting 94.6% of mutation carriers while reducing VUS rate to 21.5%.

CONCLUSIONS

Evolution of CA Genetics testing strategy to a multigene approach facilitated detection of pathogenic mutations in non-BRCA1/2 genes and aided management. Guideline-based panel testing is feasible and can be offered in Asians with suspected HBC.

Genomics of Hereditary Colorectal Cancer: Lessons Learnt from 25 Years of the Singapore Polyposis Registry

INTRODUCTION

The Singapore Polyposis Registry (SPR) was established in 1989 in Singapore General Hospital (SGH). The aims were to provide a central registry service to facilitate identification, surveillance and management of families and individuals at high risk of colorectal cancer.

MATERIALS AND METHODS

This is a review of published literature in the department.

RESULTS

The registry currently has 253 families with several genetic conditions-93 familial adenomatous polyposis (FAP) families, 138 Amsterdam-criteria positive presumed Lynch syndrome (LS) families, 12 families with Peutz Jeghers syndrome, 2 families with Cowden's syndrome, and 8 families with hereditary mixed polyposis syndrome (HMPS). There are also 169 families with a strong family history of colorectal cancer but no abnormal genes yet identified. In FAP, a diagnostic tool developed has allowed a 94% local APC germline detection rate in FAP families. Knowledge obtained studying the phenotype of FAP patients has allowed better choice of surgery between ileal pouch anal anastomosis (IPAA) against an ileal-rectal anastomosis (IRA). In LS, our review has noted a highly heterogenous mutational spectrum and novel variants made up 46.7% (28/60) of all variants identified in this cohort. This may suggest that our Southeast Asian ethnic groups have distinct mutational variants from Western populations. Pathogenic mutations were only confined to MLH1 and MSH2, and identified in 28.8% of families.

CONCLUSION

The impact of predictive gene testing for hereditary cancer risk in clinical practice has allowed evolution of care. Risk-reducing surgery and aggressive surveillance allows reduction in morbidity and mortality of patients. The SPR will continue to grow and improve outcomes in hereditary colorectal cancer patients and families.

Familial correlations of onset age of hepatocellular carcinoma: a population-based case-control family study

BACKGROUND

There was lack of evidence for familial aggregation in onset age of hepatocellular carcinoma (HCC) in Chinese population. We conducted a population-based case-control family study to examine familial correlation of age of HCC onset in Taixing, China.

METHODS

A total of 202 cases and 202 matched controls as well as their relatives were included in the study. Lifetime cumulative risks of HCC were estimated using the Kaplan-Meier approach. Cross ratios (CRs) were obtained from stratified Cox proportional hazard models, to assess the familial correlation of onset age.

RESULTS

The mean age of HCC onset was decreased as increasing number of HCC cases in a family. The onset age was the earliest for first-degree relatives, intermediate for second-degree relatives, and latest for non-blood relatives (spouse) (log-rank test, P<0.01). The onset age was significantly correlated between probands and their relatives. In stratified Cox proportional hazard models, the CRs for the probands versus their fathers, mothers, siblings and uncles/aunts were 6.25 (95% confidence interval (CI): 1.84-21.25), 9.81 (95% CI: 1.24-77.56), 6.22 (95% CI: 1.37-28.36) and 3.24 (95% CI: 1.26-8.33), respectively. After adjustment for hepatitis B virus infection, the CRs remained significant.

CONCLUSION

This current study suggested a significant correlation of onset age for HCC among blood relatives. Familial HCC cases yielded earlier age of onset and their relatives have higher HCC risk in early age, highlighting intensive surveillance should be start at an earlier age for individuals with family history of HCC.

[Constitutional risk factors in prostate cancer]

INTRODUCTION

The aim of this review is to update and divulge the main constitutional risk factors involved in the etiopathology of prostate cancer.

MATERIALS AND METHODS

Bibliographic review of the scientific literature on the constitutional risk factors associated with prostate cancer between 1985 and 2010, obtained from MedLine, CancerLit, Science Citation Index and Embase. The search profiles were Risk Factors, Genetic Factors, Genetic Polymorphisms, Genomics, Etiology, Epidemiology, Hormonal Factors, Endocrinology, Primary Prevention and Prostate Cancer.

RESULTS

The principal constitutional risk factors are: age (before the age of 50 years at least 0.7% of these neoplasms are diagnosed and between 75-85% are diagnosed after the age of 65 years), ethnic-racial and geographic (African Americans present the highest incidence rates, and the lowest are found in South East Asia), genetic, family and hereditary (family syndromes cover 13-26% of all prostate cancers, of which 5% are of autosomal dominant inheritance), hormonal (it is a hormone-dependent tumour), anthropometric (obesity increases the risk), perinatal, arterial hypertension and type 2 diabetes.

CONCLUSIONS

Constitutional risk factors play a very important role in the etiopathology of prostate cancer, especially age, ethnic-racial-geographic factors and genetic-family factors. We cannot know what percentage of these neoplasms are a result of constitutional factors, because our knowledge of these factors is currently lacking.

Mutation analysis and characterization of ATR sequence variants in breast cancer cases from high-risk French Canadian breast/ovarian cancer families

Background

Ataxia telangiectasia-mutated and Rad3-related (ATR) is a member of the PIK-related family which plays, along with ATM, a central role in cell-cycle regulation. ATR has been shown to phosphorylate several tumor suppressors like BRCA1, CHEK1 and TP53. ATR appears as a good candidate breast cancer susceptibility gene and the current study was designed to screen for ATR germline mutations potentially involved in breast cancer predisposition.

Methods

ATR direct sequencing was performed using a fluorescent method while widely available programs were used for linkage disequilibrium (LD), haplotype analyses, and tagging SNP (tSNP) identification. Expression analyses were carried out using real-time PCR.

Results

The complete sequence of all exons and flanking intronic sequences were analyzed in DNA samples from 54 individuals affected with breast cancer from non-BRCA1/2 high-risk French Canadian breast/ovarian families. Although no germline mutation has been identified in the coding region, we identified 41 sequence variants, including 16 coding variants, 3 of which are not reported in public databases. SNP haplotypes were established and tSNPs were identified in 73 healthy unrelated French Canadians, providing a valuable tool for further association studies involving the ATR gene, using large cohorts. Our analyses led to the identification of two novel alternative splice transcripts. In contrast to the transcript generated by an alternative splicing site in the intron 41, the one resulting from a deletion of 121 nucleotides in exon 33 is widely expressed, at significant but relatively low levels, in both normal and tumoral cells including normal breast and ovarian tissue.

Conclusion

Although no deleterious mutations were identified in the ATR gene, the current study provides an haplotype analysis of the ATR gene polymorphisms, which allowed the identification of a set of SNPs that could be used as tSNPs for large-scale association studies. In addition, our study led to the characterization of a novel Δ33 splice form, which could generate a putative truncated protein lacking several functional domains. Additional studies in large cohorts and other populations will be needed to further evaluate if common and/or rare ATR sequence variants can be associated with a modest or intermediate breast cancer risk.

The BARD1 Cys557Ser variant and breast cancer risk in Iceland

BACKGROUND

Most, if not all, of the cellular functions of the BRCA1 protein are mediated through heterodimeric complexes composed of BRCA1 and a related protein, BARD1. Some breast-cancer-associated BRCA1 missense mutations disrupt the function of the BRCA1/BARD1 complex. It is therefore pertinent to determine whether variants of BARD1 confer susceptibility to breast cancer. Recently, a missense BARD1 variant, Cys557Ser, was reported to be at increased frequencies in breast cancer families. We investigated the role of the BARD1 Cys557Ser variant in a population-based cohort of 1,090 Icelandic patients with invasive breast cancer and 703 controls. We then used a computerized genealogy of the Icelandic population to study the relationships between the Cys557Ser variant and familial clustering of breast cancer.

METHODS AND FINDINGS

The Cys557Ser allele was present at a frequency of 0.028 in patients with invasive breast cancer and 0.016 in controls (odds ratio [OR] = 1.82, 95% confidence interval [CI] 1.11-3.01, p = 0.014). The alleleic frequency was 0.037 in a high-predisposition group of cases defined by having a family history of breast cancer, early onset of breast cancer, or multiple primary breast cancers (OR = 2.41, 95% CI 1.22-4.75, p = 0.015). Carriers of the common Icelandic BRCA2 999del5 mutation were found to have their risk of breast cancer further increased if they also carried the BARD1 variant: the frequency of the BARD1 variant allele was 0.047 (OR = 3.11, 95% CI 1.16-8.40, p = 0.046) in 999del5 carriers with breast cancer. This suggests that the lifetime probability of a BARD1 Cys557Ser/BRCA2 999del5 double carrier developing breast cancer could approach certainty. Cys557Ser carriers, with or without the BRCA2 mutation, had an increased risk of subsequent primary breast tumors after the first breast cancer diagnosis compared to non-carriers. Lobular and medullary breast carcinomas were overrepresented amongst Cys557Ser carriers. We found that an excess of ancestors of contemporary carriers lived in a single county in the southeast of Iceland and that all carriers shared a SNP haplotype, which is suggestive of a founder event. Cys557Ser was found on the same SNP haplotype background in the HapMap Project CEPH sample of Utah residents.

CONCLUSIONS

Our findings suggest that BARD1 Cys557Ser is an ancient variant that confers risk of single and multiple primary breast cancers, and this risk extends to carriers of the BRCA2 999del5 mutation.

Familial pancreatic carcinoma in Jews

Pancreatic cancer (PC) is the most fatal of all gastrointestinal cancers, wherein its mortality compares strikingly with its incidence. Unfortunately, 80-90% of PCs are diagnosed in the nonresectable stage. While the lifetime risk of PC in developed countries is approximately 1-3%, it is the fifth most common cause of cancer deaths among both males and females in Western countries. It occurs in excess in Jews. Approximately 5-10% of PC shows familial clustering. Examination of such familial clusters must take into consideration cancers of diverse anatomic sites, such as malignant melanoma in the familial atypical multiple melanoma (FAMMM) syndrome due to the CDKN2A (p16) germline mutation, and combinations of colorectal and endometrial carcinoma, ovarian carcinoma, and several other cancers in hereditary nonpolyposis colorectal cancer (HNPCC), which are due to mismatch repair germline mutations, the most common of which are MSH2 and MLH1 . Other hereditary disorders predisposing to PC include Peutz-Jeghers syndrome, due to the STK11 mutation, familial pancreatitis due to the cationic trypsinogen gene, site-specific familial pancreatic cancer which may be due to the 4q32-34 mutation, hereditary breast-ovarian cancer (HBOC) syndrome that is due to BRCA2 and possibly some families with HBOC that is due to BRCA1 , familial adenomatous polyposis due to the ATP gene, and ataxia telangiectasia due to the ATM germline mutation. This extant heterogeneity mandates that the physician be knowledgeable about these PC-prone syndromes which play such an important role when considering the differential diagnosis of hereditary PC. Unfortunately, there are no PC screening programs with acceptable sensitivity and specificity. However, the gold standard for screening at this time is endoscopic ultrasound. Clearly, there is a great need for the development of novel screening approaches with acceptable sensitivity and specificity. Further research is needed to elucidate those etiologic factors that contribute to the apparent excess of PC in Ashkenazi Jews. Attention should also be given to the search for mutations predisposing to PC in Jews so that opportunities to learn more about the disease's pathogenesis, as well as screening and control, may take place.

A rapid and sensitive approach to mutation detection using real-time polymerase chain reaction and melting curve analyses, using BRCA1 as an example

BACKGROUND

The detection of 2 recurrent mutations in the BRCA1 gene (Ashkenazi Jewish and Dutch populations) was studied with real-time polymerase chain reaction (PCR) and melting curve analyses.

METHODS

PCR products were designed around the 185delAG in exon 2 and the single- base substitution 2841G>T in exon 11. Hybridization probe sets were designed for both PCR products, with each probe overlapping the specific mutation. The exon 11 probe set also covered another mutation, the 2814insA. The 39 end of the 59 probe was labeled with fluorescein isothiocyanate and the 59 end of the 39 probe with LightCycler Red 640 (Roche Diagnostics, Indianapolis, IN).

RESULTS

The 185del and 2841G mutations were easily detected with the hybridization probes, resulting in dual peaks for heterozygotes in melting curve analyses. The differences in melting characteristics of the heteroduplexes in heterozygotes were not detectable with SYBR Green I.

CONCLUSION

For known mutations, melting curve analyses using hybridization-specific probes provide a sensitive, rapid, and efficient approach to mutation detection.

Colorectal cancer and the Muir-Torre syndrome in a Gypsy family: a review

OBJECTIVES

The Muir-Torre syndrome (MTS) is characterized by an autosomal dominant predilection to sebaceous adenomas, sebaceous carcinomas, and multiple keratoacanthomas, in concert with the cancer phenotype of hereditary nonpolyposis colorectal cancer (HNPCC). Proof that patients showing a familial aggregation of MTS's cutaneous signs in combination with a specific pattern of visceral cancers which are consonant with an HNPCC diagnosis has been buttressed by the discovery of hMSH2 and hMLH1 germ-line mutations in such families. Our purpose in this investigation was to determine the germ-line mutation in a Gypsy family with MTS in concert with HNPCC cancer features, and to provide genetic counseling. An added objective for this paper is to review the literature on MTS.

METHODS

We describe a Gypsy family with MTS in concert with HNPCC cancer features, as well as the molecular genetic and genetic counseling procedures used in the interest of improved compliance with cancer control recommendations. We review the clinical phenotype, natural history, and molecular genetics involved in the MTS variant HNPCC.

RESULTS

An hMSH2 germ-line mutation was identified as the culprit germ-line mutation in this family.

CONCLUSIONS

The presence of the hMSH2 germ-line mutation in this family provides powerful predictability of colorectal and other HNPCC integral cancers. The gastroenterologist must assume an important role in the diagnosis and management of MTS.

Low proportion of BRCA1 and BRCA2 mutations in Finnish breast cancer families: evidence for additional susceptibility genes

One hundred breast and breast-ovarian cancer families identified at the Helsinki University Central Hospital in southern Finland and previously screened for mutations in the BRCA2 gene were now analyzed for mutations in the BRCA1 gene. The coding region and splice boundaries of BRCA1 were analyzed by protein truncation test (PTT) and heteroduplex analysis (HA)/SSCP in all 100 families, and 70 were also screened by direct sequencing. Contrary to expectations based on Finnish population history and strong founder effects in several monogenic diseases in Finland, a wide spectrum of BRCA1 and BRCA2 mutations was found. In the BRCA1 gene, 10 different protein truncating mutations were found each in one family. Six of these are novel Finnish mutations and four have been previously found in other European populations. Six different BRCA2 mutations were found in 11 families. Altogether only 21% of the breast cancer families were accounted for by mutations in these two genes. Linkage to both chromosome 17q21 (BRCA1) and 13q12 (BRCA2) was also excluded in a subset of seven mutation-negative families with four or more cases of breast or ovarian cancer. These data indicate that additional breast and breast-ovarian cancer susceptibility genes are likely to be important in Finland.