Biomedical subjects

Suzanna L Arcand

Publications and source records attributed to Suzanna L Arcand.

5 recordsLinked to original sources

PubMed2007

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.

Cell Line, Tumor↗

PubMed2006

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.

Adult↗

PubMed2005

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.

Allelic Imbalance↗

PubMed2004

Significant proportion of breast and/or ovarian cancer families of French Canadian descent harbor 1 of 5 BRCA1 and BRCA2 mutations.

In 1998, we reported that a significant proportion of breast and/or ovarian cancer families of French Canadian descent harbor specific germline mutations in BRCA1 or BRCA2 attributed to common founders. Here we report the frequency of previously described mutations (n = 7) and 13 mutations identified in French Canadian families since 1998, in a new group of families (n = 88). Four of the previously described mutations, 4446C>T, 2953delGTAinsC, 8765delAG and 6085C>T, account for 72% and 69% of mutation-positive families in previously (n = 81) and recently ascertained groups, respectively. Only 2 of 13 recently identified mutations were found in more than 1 family: 3875delGTCT (n = 2) and 3398delAAAAG (n = 4). The 2 groups (ascertained pre- and post-gene discovery) did not differ significantly when distribution of mutations based on cancer syndrome phenotype and age of diagnosis or number of breast cancer cases were compared. Five common mutations accounted for a significant proportion (84%) of all mutation-positive families. The age of diagnosis of female breast cancer in mutation-negative families was significantly higher than that of the mutation-positive families (p<0.0001). The total number of cases of cancer per family was significantly lower in mutation-negative than mutation-positive families (p<0.001). Our results define a new mutation panel for screening BRCA1/2 mutations and the phenotype of mutation-positive families harboring the common mutations in the French Canadian population.

Adult↗

PubMed2004

Gene expression microarray analysis and genome databases facilitate the characterization of a chromosome 22 derived homogeneously staining region.

Karyotype and fluorescence in situ hybridization (FISH) analyses previously identified a homogeneously staining region (HSR) derived from chromosome 22 in OV90, an epithelial ovarian cancer (EOC) cell line. Affymetrix expression microarrays in combination with the UniGene and Human Genome Browser databases were used to identify the candidate genes comprising the amplicon of the HSR, based on comparison of expression profiles of OV90, EOC cell lines lacking HSRs and primary cultures of normal ovarian surface epithelial (NOSE) cells. A group of probe sets displaying a minimum 3-fold overexpression with a high reliability score (P-call) in OV90 were identified which represented genes that mapped within a 1-2 Mb interval on chromosome 22. A large number of probe sets, some of which represent the same genes, displayed no evidence of overexpression and/or low reliability scores (A-call). An investigation of the probe set sequences with the Affymetrix and Sanger Institute Chromosome 22 Group databases revealed that some of the probe sets displaying discordant results for the same gene were complementary to intronic sequences and/or the antisense strand. Microarray results were validated by RT-PCR. Genomic analysis suggests that the HSR was derived from the amplification of a 1.1 Mb interval defined by the chromosomal map positions of ZNF74 and Hs.372662, at 22q11.21. The deduced amplicon is derived from a complex region of chromosome 22 that harbors low-copy repeats (LCRs). The amplicon contains 18 genes as likely targets for gene amplification. This study illustrates that large-scale expression microarray analysis in combination with genome databases is sufficient for deducing target genes associated with amplicons and stresses the importance of investigating probe set design before engaging in validation studies.

Cell Line, Tumor↗