Germline TP53 mutational spectrum in French Canadians with breast cancer.

BACKGROUND: Specific germline mutations in the hereditary breast-ovarian cancer susceptibility (HBC/HBOC) genes, BRCA1, BRCA2 and PALB2, have been shown to recur in French Canadians of Quebec, Canada, and this has been attributed to common ancestors. Germline TP53 mutation carriers are known to segregate in Li-Fraumeni syndrome families, which feature young age of onset breast cancer. We have reported rare TP53 mutation carriers in French Canadian HBC families, though none recurred possibly due to the limited number of cancer families investigated. Here we describe TP53 germline mutations found in French Canadian cancer families provided from hereditary cancer clinics; investigate 37 new BRCA1 and BRCA2 mutation-negative HBC/HBOC families for the TP53 mutations; and assess the frequency of TP53 mutations in a 1235 French Canadian breast cancer cases not selected for family history of cancer. METHODS: TP53 mutation-positive pedigrees from French Canadian cancer families were provided from local hereditary cancer clinics. Bidirectional Sanger sequencing of all protein encoding exons of TP53 was performed using peripheral blood lymphocyte DNA from breast/ovarian cancer probands from 37 HBC/HBOC families of French Canadian descent. Targeted bidirectional Sanger sequencing assay of regions containing the identified TP53 mutations was performed on 1235 French Canadian breast cancer cases not selected for family history cancer. RESULTS: Five new TP53 mutations were identified in six pedigrees from hereditary cancer clinics. No deleterious mutations were identified in cancer probands from 37 HBC/HBOC families. A targeted mutation screen of the 1235 breast cancer cases identified a c.844C>T [p.Arg282Trp] mutation carrier. This mutation was also found among the six mutation-positive cancer families provided by the local hereditary cancer clinics. The targeted screen also uncovered a new TP53 mutation, c.685T>C [p.Cys229Arg] that was found in two breast cancer cases. All TP53 mutation carriers were among the 656 women with breast cancer diagnosed less than 50 years of age. CONCLUSIONS: In all six new TP53 mutations were identified in French Canadians, where two each occurred in independently ascertained cases/families. Although all newly identified breast cancer mutation carriers reported a family history of cancer, none were consistent with features of Li-Fraumeni syndrome families.

The BRCA2 c.9004G>A (E2002K) [corrected] variant is likely pathogenic and recurs in breast and/or ovarian cancer families of French Canadian descent.

Specific BRCA1 and BRCA2 mutations recur in French Canadian breast and/or ovarian cancer families because of common ancestors, facilitating carrier detection in this population. We recently reported a BRCA2 c.9004G>A variant of unknown clinical significance in two French Canadian breast cancer families. It confers a E3002K alteration in the conserved C-terminus domain of BRCA2, and has been reported in non-French Canadian cancer families. Seven variant positive French Canadian families have since been identified by mutation screening of referrals to hereditary cancer clinics. In this article, we describe the cancer phenotypes of these families and further assess the contribution of this variant in the French Canadian population. We screened index breast cancer cases from 58 cancer families with at least three confirmed cases of breast and/or ovarian cancer and 960 breast cancer cases (48 years mean age) not selected for family history of cancer that were previously found not to carry the most common BRCA1 and BRCA2 mutations reported in this population. The index variant-positive cases from each family had breast cancer between the ages of 35-55 years (43 years mean age); and reported close relatives with breast cancer diagnoses between the ages of 28-84 years (57 years mean age). Three families had ovarian or peritoneal cancers. BRCA2-associated cancers, such as bladder, esophagus, pancreas, prostate, and thyroid cancers also occurred in these families. One c.9004G>A carrier also harbored the PALB2 c.2323C>T (Q775X) mutation found to recur in French Canadian breast cancer cases. No new BRCA2 variant carriers were identified in mutation screens. The absence of BRCA2 c.9004G>A carriers in the breast cancer cases not selected for family history contrasts with familial cases, supporting a pathogenic status for this variant and addition to the existing common BRCA1 and BRCA2 mutation-screening panel for French Canadian breast and/or ovarian cancer families.

Derivation and characterization of matched cell lines from primary and recurrent serous ovarian cancer.

BACKGROUND: Cell line models have proven to be effective tools to investigate a variety of ovarian cancer features. Due to the limited number of cell lines, particularly of the serous subtype, the heterogeneity of the disease, and the lack of cell lines that model disease progression, there is a need to further develop cell line resources available for research. This study describes nine cell lines derived from three ovarian cancer cases that were established at initial diagnosis and at subsequent relapse after chemotherapy. METHODS: The cell lines from three women diagnosed with high-grade serous ovarian cancer (1369, 2295 and 3133) were derived from solid tumor (TOV) and ascites (OV), at specific time points at diagnosis and relapse (R). Primary treatment was a combination of paclitaxel/carboplatin (1369, 3133), or cisplatin/topotecan (2295). Second line treatment included doxorubicin, gemcitabine and topotecan. In addition to molecular characterization (p53, HER2), the cell lines were characterized based on cell growth characteristics including spheroid growth, migration potential, and anchorage independence. The in vivo tumorigenicity potential of the cell lines was measured. Response to paclitaxel and carboplatin was assessed using a clonogenic assay. RESULTS: All cell lines had either a nonsense or missense TP53 mutations. The ability to form compact spheroids or aggregates was observed in six of nine cell lines. Limited ability for migration and anchorage independence was observed. The OV3133(R) cell line, formed tumors at subcutaneous sites in SCID mice. Based on IC50 values and dose response curves, there was clear evidence of acquired resistance to carboplatin for TOV2295(R) and OV2295(R2) cell lines. CONCLUSION: The study identified nine new high-grade serous ovarian cancer cell lines, derived before and after chemotherapy that provides a unique resource for investigating the evolution of this common histopathological subtype of ovarian cancer.

The Genetic and Molecular Analyses of RAD51C and RAD51D Identifies Rare Variants Implicated in Hereditary Ovarian Cancer from a Genetically Unique Population.

To identify candidate variants in RAD51C and RAD51D ovarian cancer (OC) predisposing genes by investigating French Canadians (FC) exhibiting unique genetic architecture. Candidates were identified by whole exome sequencing analysis of 17 OC families and 53 early-onset OC cases. Carrier frequencies were determined by the genetic analysis of 100 OC or HBOC families, 438 sporadic OC cases and 1025 controls. Variants of unknown function were assayed for their biological impact and/or cellular sensitivity to olaparib. RAD51C c.414G>C;p.Leu138Phe and c.705G>T;p.Lys235Asn and RAD51D c.137C>G;p.Ser46Cys, c.620C>T;p.Ser207Leu and c.694C>T;p.Arg232Ter were identified in 17.6% of families and 11.3% of early-onset cases. The highest carrier frequency was observed in OC families (1/44, 2.3%) and sporadic cases (15/438, 3.4%) harbouring RAD51D c.620C>T versus controls (1/1025, 0.1%). Carriers of c.620C>T (n = 7), c.705G>T (n = 2) and c.137C>G (n = 1) were identified in another 538 FC OC cases. RAD51C c.705G>T affected splicing by skipping exon four, while RAD51D p.Ser46Cys affected protein stability and conferred olaparib sensitivity. Genetic and functional assays implicate RAD51C c.705G>T and RAD51D c.137C>G as likely pathogenic variants in OC. The high carrier frequency of RAD51D c.620C>T in FC OC cases validates previous findings. Our findings further support the role of RAD51C and RAD51D in hereditary OC.

Investigating the causal role of MRE11A p.E506* in breast and ovarian cancer.

The nuclease MRE11A is often included in genetic test panels for hereditary breast and ovarian cancer (HBOC) due to its BRCA1-related molecular function in the DNA repair pathway. However, whether MRE11A is a true predisposition gene for HBOC is still questionable. We determined to investigate this notion by dissecting the molecular genetics of the c.1516G > T;p.E506* truncating MRE11A variant, that we pinpointed in two unrelated French-Canadian (FC) HBOC patients. We performed a case-control study for the variant in ~ 2500 breast, ovarian, and endometrial cancer patients from the founder FC population of Quebec. Furthermore, we looked for the presence of second somatic alterations in the MRE11A gene in the tumors of the carriers. In summary, these investigations suggested that the identified variant is not associated with an increased risk of developing breast or ovarian cancer. We finally performed a systematic review for all the previously reported MRE11A variants in breast and ovarian cancer. We found that MRE11A germline variants annotated as pathogenic on ClinVar often lacked evidence for such classification, hence misleading the clinical management for affected patients. In summary, our report suggests the lack of clinical utility of MRE11A testing in HBOC, at least in the White/Caucasian populations.

A functionally impaired missense variant identified in French Canadian families implicates FANCI as a candidate ovarian cancer-predisposing gene.

BACKGROUND: Familial ovarian cancer (OC) cases not harbouring pathogenic variants in either of the BRCA1 and BRCA2 OC-predisposing genes, which function in homologous recombination (HR) of DNA, could involve pathogenic variants in other DNA repair pathway genes. METHODS: Whole exome sequencing was used to identify rare variants in HR genes in a BRCA1 and BRCA2 pathogenic variant negative OC family of French Canadian (FC) ancestry, a population exhibiting genetic drift. OC cases and cancer-free individuals from FC and non-FC populations were investigated for carrier frequency of FANCI c.1813C>T; p.L605F, the top-ranking candidate. Gene and protein expression were investigated in cancer cell lines and tissue microarrays, respectively. RESULTS: In FC subjects, c.1813C>T was more common in familial (7.1%, 3/42) than sporadic (1.6%, 7/439) OC cases (P = 0.048). Carriers were detected in 2.5% (74/2950) of cancer-free females though female/male carriers were more likely to have a first-degree relative with OC (121/5249, 2.3%; Spearman correlation = 0.037; P = 0.011), suggesting a role in risk. Many of the cancer-free females had host factors known to reduce risk to OC which could influence cancer risk in this population. There was an increased carrier frequency of FANCI c.1813C>T in BRCA1 and BRCA2 pathogenic variant negative OC families, when including the discovery family, compared to cancer-free females (3/23, 13%; OR = 5.8; 95%CI = 1.7-19; P = 0.005). In non-FC subjects, 10 candidate FANCI variants were identified in 4.1% (21/516) of Australian OC cases negative for pathogenic variants in BRCA1 and BRCA2, including 10 carriers of FANCI c.1813C>T. Candidate variants were significantly more common in familial OC than in sporadic OC (P = 0.04). Localization of FANCD2, part of the FANCI-FANCD2 (ID2) binding complex in the Fanconi anaemia (FA) pathway, to sites of induced DNA damage was severely impeded in cells expressing the p.L605F isoform. This isoform was expressed at a reduced level, destabilized by DNA damaging agent treatment in both HeLa and OC cell lines, and exhibited sensitivity to cisplatin but not to a poly (ADP-ribose) polymerase inhibitor. By tissue microarray analyses, FANCI protein was consistently expressed in fallopian tube epithelial cells and only expressed at low-to-moderate levels in 88% (83/94) of OC samples. CONCLUSIONS: This is the first study to describe candidate OC variants in FANCI, a member of the ID2 complex of the FA DNA repair pathway. Our data suggest that pathogenic FANCI variants may modify OC risk in cancer families.

The chemiluminescence based Ziplex automated workstation focus array reproduces ovarian cancer Affymetrix GeneChip expression profiles.

BACKGROUND: As gene expression signatures may serve as biomarkers, there is a need to develop technologies based on mRNA expression patterns that are adaptable for translational research. Xceed Molecular has recently developed a Ziplex technology, that can assay for gene expression of a discrete number of genes as a focused array. The present study has evaluated the reproducibility of the Ziplex system as applied to ovarian cancer research of genes shown to exhibit distinct expression profiles initially assessed by Affymetrix GeneChip analyses. METHODS: The new chemiluminescence-based Ziplex gene expression array technology was evaluated for the expression of 93 genes selected based on their Affymetrix GeneChip profiles as applied to ovarian cancer research. Probe design was based on the Affymetrix target sequence that favors the 3' UTR of transcripts in order to maximize reproducibility across platforms. Gene expression analysis was performed using the Ziplex Automated Workstation. Statistical analyses were performed to evaluate reproducibility of both the magnitude of expression and differences between normal and tumor samples by correlation analyses, fold change differences and statistical significance testing. RESULTS: Expressions of 82 of 93 (88.2%) genes were highly correlated (p < 0.01) in a comparison of the two platforms. Overall, 75 of 93 (80.6%) genes exhibited consistent results in normal versus tumor tissue comparisons for both platforms (p < 0.001). The fold change differences were concordant for 87 of 93 (94%) genes, where there was agreement between the platforms regarding statistical significance for 71 (76%) of 87 genes. There was a strong agreement between the two platforms as shown by comparisons of log2 fold differences of gene expression between tumor versus normal samples (R = 0.93) and by Bland-Altman analysis, where greater than 90% of expression values fell within the 95% limits of agreement. CONCLUSION: Overall concordance of gene expression patterns based on correlations, statistical significance between tumor and normal ovary data, and fold changes was consistent between the Ziplex and Affymetrix platforms. The reproducibility and ease-of-use of the technology suggests that the Ziplex array is a suitable platform for translational research.

Haplotype analysis of TP53 polymorphisms, Arg72Pro and Ins16, in BRCA1 and BRCA2 mutation carriers of French Canadian descent.

BACKGROUND: The TP53 polymorphisms Arg72Pro (Ex4+199 G>C) and Ins16 (IVS3+24 ins16) have been proposed to modify risk of breast cancer associated with germline BRCA1 and BRCA2 mutations. Allele frequencies of these polymorphisms were investigated to determine if they modify risk in BRCA mutation carriers in breast cancer cases drawn from French Canadian cancer families, a population shown to exhibit strong founder effects. METHODS: The frequencies of the TP53 alleles, genotypes and haplotypes of 157 index breast cancer cases comprised of 42 BRCA1 mutation carriers, 57 BRCA2 mutation carriers, and 58 BRCA mutation-negative cases, where each case was drawn from independently ascertained families were compared. The effect of TP53 variants on the age of diagnosis was also investigated for these groups. The TP53 polymorphisms were also investigated in 112 women of French Canadian descent with no personal history of cancer. RESULTS: The BRCA mutation-positive groups had the highest frequency of homozygous carriers of the 72Pro allele compared with mutation-negative group. The TP53 polymorphisms exhibited linkage disequilibrium (p < 0.001), where the 72Arg and Ins16minus alleles occurred in strong disequilibrium. The highest frequency of carriers of Ins16minus-72Arg haplotype occurred in the BRCA mutation-negative groups. The BRCA1 mutation carriers homozygous for the 72Pro allele had the youngest ages of diagnosis of breast cancer. However none of these observations were statistically significant. In contrast, the BRCA2 mutation carriers homozygous for the 72Pro allele had a significantly older age of diagnosis of breast cancer (p = 0.018). Moreover, in this group, the mean age of diagnosis of breast cancer in carriers of the Ins16minus-72Arg haplotype was significantly younger than that of the individuals who did not this carry this haplotype (p = 0.009). CONCLUSION: We observed no significant association of breast cancer risk with TP53 genetic variants based on BRCA1/2 mutation carrier status. Although the small sample size did not permit analysis of all possible haplotypes, we observed that BRCA2 mutation carriers harboring the Ins16minus-72Arg haplotype had a significantly younger mean age of diagnosis of breast cancer. These observations suggest that investigations in a larger French Canadian sample are warranted to further elucidate the effects of TP53 variants on age of diagnosis of breast cancer among BRCA1 and BRCA2 mutation carriers.

Characterization of three new serous epithelial ovarian cancer cell lines.

BACKGROUND: Cell lines constitute a powerful model to study cancer, and here we describe three new epithelial ovarian cancer (EOC) cell lines derived from poorly differentiated serous solid tumors (TOV-1946, and TOV-2223G), as well as the matched ascites for one case (OV-1946). METHODS: In addition to growth parameters, the cell lines were characterized for anchorage independent growth, migration and invasion potential, ability to form spheroids and xenografts in SCID mice. RESULTS: While all cell lines were capable of anchorage independent growth, only the TOV-1946 and OV-1946 cell lines were able to form spheroid and produce tumors. Profiling of keratins, p53 and Her2 protein expression was assessed by immunohistochemistry and western blot analyses. Somatic TP53 mutations were found in all cell lines, with TOV-1946 and OV-1946 harboring the same mutation, and none harbored the commonly observed somatic mutations in BRAF, KRAS or germline BRCA1/2 mutations found to recur in the French Canadian population. Conventional cytogenetics and spectral karyotype (SKY) analyses revealed complex karyotypes often observed in ovarian disease. CONCLUSION: This is the first report of the establishment of matched EOC cell lines derived from both solid tumor and ascites of the same patient.

Global analysis of chromosome X gene expression in primary cultures of normal ovarian surface epithelial cells and epithelial ovarian cancer cell lines.

The interpretation of loss of heterozygosity (LOH) in cancers is complicated as genes that map to LOH regions may be transcriptionally active (Xa) or inactive (Xi) due to X chromosome inactivation (XCI). We have analyzed the chromosome X transcriptome in four epithelial ovarian cancer (EOC) cell lines (TOV21G, TOV81D, TOV112D, and OV90) and 12 primary cultures of normal ovarian surface epithelial (NOSE) cells in relation to chromosome X integrity. Two-way comparative analysis using HuGeneFL Affymetrix GeneChips of TOV21G, TOV81D and OV90 relative to the NOSE samples was highly correlated (> 89%) in contrast to that of TOV112D (56-69%). TOV112D, followed by TOV21G, exhibited the largest number of up-regulated genes. XIST expression by RT-PCR was not detectable in TOV112D or TOV21G. Allele-specific transcription by cDNA sequence analysis of genes known to be subjected to XCI revealed maintenance of XCI in TOV81D and OV90, but not TOV21G. Biallelic expression could not be assessed in TOV112D due to reduction to hemizygosity of chromosome X. Chromosome X rearrangements were observed in FISH analysis of TOV112D and TOV21G, and both of these EOC cell lines were negative for Barr body analysis. The differentially expressed genes did not appear to map to any particular region of the X chromosome in any EOC cell line. The absence of XIST expression is consistent with Barr body loss in TOV112D and TOV21G. The combined evidence is consistent with two proposed mechanisms to account for absence of Xi in female cancers: Xi loss followed by Xa duplication (exemplified by TOV112D) and transcriptional reactivation of Xi (exemplified by TOV21G). Despite an alteration in XIST expression and differences in allelic content in the EOC cell lines, the chromosome X transcriptome was modified modestly when compared with that of NOSE samples.

Functionally Null RAD51D Missense Mutation Associates Strongly with Ovarian Carcinoma.

RAD51D is a key player in DNA repair by homologous recombination (HR), and RAD51D truncating variant carriers have an increased risk for ovarian cancer. However, the contribution of nontruncating RAD51D variants to cancer predisposition remains uncertain. Using deep sequencing and case-control genotyping studies, we show that in French Canadians, the missense RAD51D variant c.620C>T;p.S207L is highly prevalent and is associated with a significantly increased risk for ovarian high-grade serous carcinoma (HGSC; 3.8% cases vs. 0.2% controls). The frequency of the p.S207L variant did not significantly differ from that of controls in breast, endometrial, pancreas, or colorectal adenocarcinomas. Functionally, we show that this mutation impairs HR by disrupting the RAD51D-XRCC2 interaction and confers PARP inhibitor sensitivity. These results highlight the importance of a functional RAD51D-XRCC2 interaction to promote HR and prevent the development of HGSC. This study identifies c.620C>T;p.S207L as the first bona fide pathogenic RAD51D missense cancer susceptibility allele and supports the use of targeted PARP-inhibitor therapies in ovarian cancer patients carrying deleterious missense RAD51D variants. Cancer Res; 77(16); 4517-29. ©2017 AACR.

Haplotype analysis suggest common founders in carriers of the recurrent BRCA2 mutation, 3398delAAAAG, in French Canadian hereditary breast and/ovarian cancer families.

BACKGROUND: The 3398delAAAAG mutation in BRCA2 was recently found to recur in breast and/or ovarian cancer families from the French Canadian population of Quebec, a population that has genetic attributes consistent with a founder effect. To characterize the contribution of this mutation in this population, this study established the frequency of this mutation in breast and ovarian cancer cases unselected for family history of cancer, and determined if mutation carriers shared a common ancestry. METHODS: The frequency was estimated by assaying the mutation in series of French Canadian breast cancer cases diagnosed before age 41 (n = 60) or 80 (n = 127) years of age, and ovarian cancer cases (n = 80) unselected for family history of cancer by mutation analysis. Haplotype analysis was performed to determine if mutation carriers shared a common ancestry. Members from 11 families were analyzed using six polymorphic microsatellite markers (cen-D13S260-D13S1699-D13S1698-D13S1697-D13S1701-D13S171-tel) spanning approximately a 3.6 cM interval at the chromosomal region 13q13.1, which contains BRCA2. Allele frequencies were estimated by genotyping 47 unaffected female individuals derived from the same population. Haplotype reconstruction of unaffected individuals was performed using the program PHASE. RESULTS: The recurrent BRCA2 mutation occurred in 1 of 60 (1.7%) women diagnosed with breast cancer before 41 years of age and one of 80 (1.3%) women with ovarian cancer. No mutation carriers were identified in the series of breast cancer cases diagnosed before age 80. Mutation carriers harboured one of two haplotypes, 7-3-9-3 - [3/4]-7, that varied with marker D13S1701 and which occurred at a frequency of 0.001. The genetic analysis of D13S1695, a polymorphic marker located approximately 0.3 cM distal to D13S171, did not favour a genetic recombination event to account for the differences in D13S1701 alleles within the haplotype. Although mutation carriers harbour genotypes that are frequent in the French Canadian population, neither mutation-associated haplotype was plausible in reconstructed haplotypes of 47 individuals of French Canadian descent. CONCLUSION: These results suggest that mutation carriers share a related ancestry; further supporting the concept that recurrent BRCA1 and BRCA2 mutations in the French Canadian population could be attributed to common founders. This finding provides further support for targeted screening of recurrent mutations in this population before large-scale mutation analyses are performed.

OGG1 Cys326 variant, allelic imbalance of chromosome band 3p25.3 and TP53 mutations in ovarian cancer.

A Ser326Cys amino acid variant encoded by OGG1 that removes the highly mutagenic 8-oxo-7,8-dihydroguanine adducts resulting from the oxidative damage produced by reactive oxygen species, has been suggested to reduce activity of the enzyme and result in an increase in G:C --> T:A transversions. Carriers homozygous for the Cys326 variant have been associated with increased risk in some cancers. In this study, we tested the association of this polymorphism with epithelial ovarian cancer (EOC) (n=91 cases) in comparison with women unaffected by the disease (n=57). Although the genotype encoding the homozygous Cys326 variant was found more often in cases (11%) than controls (9%), this was not statistically significant (p=0.297). As OGG1 at chromosome band 3p25.3 overlaps a region exhibiting allelic imbalance (AI) in EOC, we also examined the frequency of AI of the OGG1 locus and its association with somatic mutations in the TP53 tumor suppressor gene, which is frequently mutated in EOC. The frequency of AI and TP53 mutations in EOC was 32 and 37%, respectively. Although the proportion of EOC cases harboring the genotype homozygous for Cys326 was greater in TP53 mutation-positive cases (5 of 34, 15%) than mutation-negative cases (5 of 57, 9%), the distribution of genotypes was not significantly different (p=0.289). Four of the six heterozygous Ser326/Cys326 samples exhibiting AI, displayed loss of the Ser326 variant. About 16% of samples exhibited both AI of the OGG1 locus and a TP53 mutation. Proportionately more EOC samples harbored a mutation in the group of samples exhibiting AI (15 of 29, 52%) in comparison to the group of samples with no AI (19 of 62, 31%) (p=0.036). Although the OGG1 Cys326 variant appears to play a minor role in conferring increased risk of ovarian cancer, the observed AI of the OGG1 locus in association with TP53 somatic mutations warrants further investigation in this disease.

Double PALB2 and BRCA1/BRCA2 mutation carriers are rare in breast cancer and breast-ovarian cancer syndrome families from the French Canadian founder population.

French Canadian families with breast cancer and breast-ovarian cancer syndrome harbor specific BRCA1, BRCA2 and PALB2 germline mutations, which have been attributed to common founders. Mutations in these genes confer an increased risk to breast and ovarian cancers, and have been identified to play a role in and directly interact with the common homologous recombination DNA repair pathways. Our previous study described the case of a female diagnosed with breast cancer at 45 years old, who harbored the PALB2:c.2323C>T [p.Q775X] and BRCA2:c.9004G>A [p.E3002K] germline mutations, which have been found to recur in the French Canadian cancer families. As the frequency of double heterozygous carriers of breast-ovarian cancer susceptibility alleles is unknown, and due to the possibility that there may be implications for genetic counseling and management for these carriers, the present study investigated the co-occurrence of BRCA1/BRCA2 and PALB2 mutations in the French Canadian cancer families. The PALB2:c.2323C>T [p.Q775X] mutation, which is the only PALB2 mutation to have been identified in French Canadian cancer families, was screened in 214 breast cancer cases and 22 breast-ovarian cancer cases from 114 BRCA1/BRCA2 mutation-positive French Canadian breast cancer (n=61) and breast-ovarian cancer (n=53) families using a tailored polymerase chain reaction-based TaqMan® SNP Genotyping Assay. No additional PALB2:c.2323C>T [p.Q775X] mutation carriers were identified among the BRCA1/BRCA2 mutation carriers. The results suggest that carriers of the PALB2:c.2323C>T [p.Q775X] mutation rarely co-occur in French Canadian breast cancer and breast-ovarian cancer families harboring BRCA1 or BRCA2 mutations.

Novel high-grade serous epithelial ovarian cancer cell lines that reflect the molecular diversity of both the sporadic and hereditary disease.

Few cell line models of epithelial ovarian cancer (EOC) have been developed for the high-grade serous (HGS) subtype, which is the most common and lethal form of gynaecological cancer. Here we describe the establishment of six new EOC cell lines spontaneously derived from HGS tumors (TOV2978G, TOV3041G and TOV3291G) or ascites (OV866(2), OV4453 and OV4485). Exome sequencing revealed somatic TP53 mutations in five of the cell lines. One cell line has a novel BRCA1 splice-site mutation, and another, a recurrent BRCA2 nonsense mutation, both of germline origin. The novel BRCA1 mutation induced abnormal splicing, mRNA instability, resulting in the absence of BRCA1 protein. None of the cell lines harbor mutations in KRAS or BRAF, which are characteristic of other EOC subtypes. SNP arrays showed that all of the cell lines exhibited structural chromosomal abnormalities, copy number alterations and regions of loss of heterozygosity, consistent with those described for HGS. Four cell lines were able to produce 3D-spheroids, two exhibited anchorage-independent growth, and three (including the BRCA1 and BRCA2 mutated cell lines) formed tumors in SCID mice. These novel HGS EOC cell lines and their detailed characterization provide new research tools for investigating the most common and lethal form of EOC.

A targeted analysis identifies a high frequency of BRCA1 and BRCA2 mutation carriers in women with ovarian cancer from a founder population.

BACKGROUND: The frequency of BRCA1 and BRCA2 mutations in ovarian cancer patients varies depending on histological subtype and population investigated. The six most commonly recurring BRCA1 and BRCA2 mutations previously identified in a founder French Canadian population were investigated in 439 histologically defined ovarian, fallopian tube and primary peritoneal cancer cases that were ascertained at one hospital servicing French Canadians. To further assess the frequency of BRCA1/BRCA2 mutations, a defined subgroup of 116 cases were investigated for all mutations previously reported in this population. METHODS: A PCR-based assay was used to screen 439 ovarian, fallopian tube or extra-ovarian cancers comprised of serous, high grade endometrioid and mixed cell adenocarcinomas with serous components for specific BRCA1: C4446T and 2953delGTAinsC and BRCA2: 8765delAG, G6085T, 3398del5 and E3002K mutations. A multiplex bead-array-based Luminex assay was used to evaluate 19 specific mutations that have ever been reported in French Canadians, which included the six mutations assayed by PCR, in 116 cases representing all women ascertained within a defined 3-year window. RESULTS: A targeted analysis of six mutations identified 34/439 (7.7%) mutation carriers and at least two mutation carriers for each mutation screened were found. The BRCA1:C4446T mutation was the most frequently identified variant (15/34, 44.1%) among mutation-positive cases. The expanded mutation screen that also included 13 additional variants identified 19/116 (16.4%) mutation carriers, where C4446T was the most common variant (8/19, 42.1%) identified among mutation-positive carriers in this subgroup. Mutations were identified in women with serous, endometrioid, mixed cell, and undifferentiated adenocarcinomas. Within this subgroup there were 73 high-grade (G3) serous ovarian carcinomas, the most common subtype, with mutations identified in 19.2% (n = 14) serous cases. CONCLUSIONS: Our results reaffirm that specific BRCA1 and BRCA2 mutations found previously to recur in French Canadian breast cancer and breast-ovarian cancer families, also recur in women with ovarian cancer not selected for family history of cancer. The high frequency of mutation carriers rationalizes genetic testing of ovarian cancer patients in this demographically defined population.

Analysis of genomic abnormalities in tumors: a review of available methods for Illumina two-color SNP genotyping and evaluation of performance.

Several methods have recently been proposed for identifying copy number alterations (CNAs) in genomic DNA from tumors, using the signals arising from two-color genotyping technologies. Although copy number estimation in normal tissue has been well studied, methods developed for normal tissue tend to perform poorly when applied to tumors, due to normal cell contamination, varying levels of ploidy, and genetic heterogeneity within the tumor. Here we compare the performance of seven methods (DNA-Chip Analyzer software (dCHIP), GenoCNA software, allele-specific copy number analysis of tumors (ASCAT), OncoSNP software, genome alteration print (GAP) visualization, CNVpartition software plug-in for the Genome Studio software, and Partek Genomics Suite software) that have been established for two-color CNA analysis on the Illumina platform, using two ovarian cancer cell lines where spectral karyotyping analysis has also been performed, and two tissue samples, one from a highly malignant ovarian cancer and one from a benign ovarian tumor, all of which harbor significantly different genomic abnormalities. ASCAT shows very stable estimates of CNAs, as does OncoSNP when jointly analyzing paired normal DNA. We found the best performance, in general to be from ASCAT.

Small cell ovarian carcinoma: genomic stability and responsiveness to therapeutics.

BACKGROUND: The biology of small cell ovarian carcinoma of the hypercalcemic type (SCCOHT), which is a rare and aggressive form of ovarian cancer, is poorly understood. Tumourigenicity, in vitro growth characteristics, genetic and genomic anomalies, and sensitivity to standard and novel chemotherapeutic treatments were investigated in the unique SCCOHT cell line, BIN-67, to provide further insight in the biology of this rare type of ovarian cancer. METHOD: The tumourigenic potential of BIN-67 cells was determined and the tumours formed in a xenograft model was compared to human SCCOHT. DNA sequencing, spectral karyotyping and high density SNP array analysis was performed. The sensitivity of the BIN-67 cells to standard chemotherapeutic agents and to vesicular stomatitis virus (VSV) and the JX-594 vaccinia virus was tested. RESULTS: BIN-67 cells were capable of forming spheroids in hanging drop cultures. When xenografted into immunodeficient mice, BIN-67 cells developed into tumours that reflected the hypercalcemia and histology of human SCCOHT, notably intense expression of WT-1 and vimentin, and lack of expression of inhibin. Somatic mutations in TP53 and the most common activating mutations in KRAS and BRAF were not found in BIN-67 cells by DNA sequencing. Spectral karyotyping revealed a largely normal diploid karyotype (in greater than 95% of cells) with a visibly shorter chromosome 20 contig. High density SNP array analysis also revealed few genomic anomalies in BIN-67 cells, which included loss of heterozygosity of an estimated 16.7 Mb interval on chromosome 20. SNP array analyses of four SCCOHT samples also indicated a low frequency of genomic anomalies in the majority of cases. Although resistant to platinum chemotherapeutic drugs, BIN-67 cell viability in vitro was reduced by > 75% after infection with oncolytic viruses. CONCLUSIONS: These results show that SCCOHT differs from high-grade serous carcinomas by exhibiting few chromosomal anomalies and lacking TP53 mutations. Although BIN-67 cells are resistant to standard chemotherapeutic agents, their sensitivity to oncolytic viruses suggests that their therapeutic use in SCCOHT should be considered.

VGLL3 expression is associated with a tumor suppressor phenotype in epithelial ovarian cancer.

Previous studies have implicated vestigial like 3 (VGLL3), a chromosome 3p12.3 gene that encodes a putative transcription co-factor, as a candidate tumor suppressor gene (TSG) in high-grade serous ovarian carcinomas (HGSC), the most common type of epithelial ovarian cancer. A complementation analysis based on microcell-mediated chromosome transfer (MMCT) using a centric fragment of chromosome 3 (der3p12-q12.1) into the OV-90 ovarian cancer cell line haploinsufficient for 3p and lacking VGLL3 expression was performed to assess the effect on tumorigenic potential and growth characteristics. Genetic characterization of the derived MMCT hybrids revealed that only the hybrid that contained an intact VGLL3 locus exhibited alterations of tumorigenic potential in a nude mouse xenograft model and various in vitro growth characteristics. Only stable OV-90 transfectant clones expressing low levels of VGLL3 were derived. These clones exhibited an altered cytoplasmic morphology characterized by numerous single membrane bound multivesicular-bodies (MVB) that were not attributed to autophagy. Overexpression of VGLL3 in OV-90 was achieved using a lentivirus-based tetracycline inducible gene expression system, which also resulted in MVB formation in the infected cell population. Though there was no significant differences in various in vitro and in vivo growth characteristics in a comparison of VGLL3-expressing clones with empty vector transfectant controls, loss of VGLL3 expression was observed in tumors derived from mouse xenograft models. VGLL3 gene and protein expression was significantly reduced in HGSC samples (>98%, p < 0.05) relative to either normal ovarian surface epithelial cells or epithelial cells of the fallopian tube, possible tissues of origin of HGSC. Also, there appeared to be to be more cases with higher staining levels in stromal tissue component from HGSC cases that had a prolonged disease-free survival. The results taken together suggest that VGLL3 is involved in tumor suppressor pathways, a feature that is characterized by the absence of VGLL3 expression in HGSC samples.

The genomic landscape of TP53 and p53 annotated high grade ovarian serous carcinomas from a defined founder population associated with patient outcome.

High-grade ovarian serous carcinomas (HGSC) are characterized by TP53 mutations and non-random patterns of chromosomal anomalies, where the nature of the TP53 mutation may correlate with clinical outcome. However, the frequency of common somatic genomic events occurring in HGSCs from demographically defined populations has not been explored. Whole genome SNP array, and TP53 mutation, gene and protein expression analyses were assessed in 87 confirmed HGSC samples with clinical correlates from French Canadians, a population exhibiting strong founder effects, and results were compared with independent reports describing similar analyses from unselected populations. TP53 mutations were identified in 91% of HGSCs. Anomalies observed in more than 50% of TP53 mutation-positive HGSCs involved gains of 3q, 8q and 20q, and losses of 4q, 5q, 6q, 8p, 13q, 16q, 17p, 17q, 22q and Xp. Nearly 400 regions of non-overlapping amplification or deletion were identified, where 178 amplifications and 98 deletions involved known genes. The subgroup expressing mutant p53 protein exhibited significantly prolonged overall and disease-free survival as compared with the p53 protein null subgroup. Interestingly, a comparative analysis of genomic landscapes revealed a significant enrichment of gains involving 1q, 8q, and 12p intervals in the subgroup expressing mutant p53 protein as compared with the p53 protein null subgroup. Although the findings show that the frequency of TP53 mutations and the genomic landscapes observed in French Canadian samples were similar to those reported for samples from unselected populations, there were differences in the magnitude of global gains/losses of specific chromosomal arms and in the spectrum of amplifications and deletions involving focal regions in individual samples. The findings from our comparative genomic analyses also support the notion that there may be biological differences between HGSCs that could be related to the nature of the TP53 mutation.