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Expression profiling of peripheral blood gene expression of women with hereditary breast cancer and controls (set 1)

ABSTRACT: We obtained peripheral blood samples for women from Utah (USA) and Ontario (Canada) who had a family history of breast cancer (or did not), who carried a BRCA1/2 mutation (or did not), and who had developed breast cancer (or had not). We classified the women into two groups: [1] those who had a family history of breast cancer (irrespective of BRCA1/2 mutation status) and had developed an early-onset breast tumor and [2] those who had a family history of breast cancer but had not developed a breast tumor or who did not have a family history of breast cancer (some of whom had developed sporadic breast cancer and and others who had not). We then used machine-learning methods to assess how well we could classify these women into either group. The Utah samples served as a training set, and the Ontario samples served as an independent validation set from a geographically distinct population. For the Utah cohort, there are 124 samples total: 16 who had a family history of breast cancer and carried a BRCA mutation and had developed breast cancer, 23 with a family history of breast cancer but did not carry a BRCA1/2 mutation and had developed breast cancer, 22 with a family history of breast cancer and carried a BRCA1/2 mutation but had not developed breast cancer, 22 with a family history of breast cancer but did not carry a BRCA1/2 mutation and had not developed breast cancer, 22 with no family history of breast cancer and had developed breast cancer, and 19 with no family history of breast cancer and had not developed breast cancer. The Ontario cohort included 73 samples: 11 who had a family history of breast cancer and carried a BRCA mutation and had developed breast cancer, 17 with a family history of breast cancer but did not carry a BRCA1/2 mutation and had developed breast cancer, 14 with a family history of breast cancer and carried a BRCA1/2 mutation but had not developed breast cancer, 18 with a family history of breast cancer but did not carry a BRCA1/2 mutation and had not developed breast cancer, 8 with no family history of breast cancer and had developed breast cancer, and 5 with no family history of breast cancer and had not developed breast cancer. 36 of the Ontario samples were scanned and processed at Duke University; the remaining 37 samples were handled at Boston University. The batch-adjustment process was repeated twice independently: [1] all 124 Utah samples were adjusted jointly with the 36 Ontario samples that had been processed at Duke University (set 1) and [2] all 124 Utah samples were adjusted jointly with the 37 Ontario samples that had been processed at Boston University (set 2). This dataset represents set 1.

ORGANISM(S): Homo sapiens

SUBMITTER: Andrea Bild

PROVIDER: E-GEOD-47860 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:In more than 70% of families with a strong history of breast and ovarian cancers, pathogenic mutation in BRCA1 or BRCA2 cannot be identified, even though hereditary factors are expected to be involved. It has been proposed that tumors with similar molecular phenotypes also share similar pathophysiological mechanisms. Grouping into molecularly homogeneous subsets may therefore be of potential value for further genetic analysis in order to identify new high penetrance breast cancer genes. In the current study, the aim was to investigate if global RNA profiling can be used to identify functional subgroups within breast tumors from families tested negative for BRCA1/2 germline mutations and how these subgroupings relate to different breast cancer patients within the same family. By analyzing a collection of 70 breast tumor biopsies from 58 families, we show that distinct functional subgroupings, similar to the intrinsic molecular breast cancer subtypes, exist. The distribution of subtypes was markedly different from the distribution found among BRCA1/2 mutation carriers. From 11 breast cancer families, breast tumor biopsies from more than one affected family member were included in the study. Notably, in 8 of these families we found that patients from the same family shared the same tumor subtype, showing a tendency of familial aggregation of tumor subtypes (p-value = 1.7e-3). Our finding indicates involvement of hereditary factors in these families in which family members may carry genetic susceptibility not just to breast cancer but to a particular subtype of breast cancer. Using our previously developed BRCA1/2-signatures, we identified 7 non-BRCA1/2 tumors with a BRCA1-like molecular phenotype and provide evidence for epigenetic inactivation of BRCA1 in three of the tumors. In addition, 7 BRCA2-like tumors were found. This is the first study to provide a biological link between breast cancers from family members of high risk non-BRCA1/2 families in a systematic manner, suggesting that future genetic analysis may benefit from subgrouping families into molecularly homogeneous subtypes in order to identify new high penetrance susceptibility genes. Gene expression profiling of 253 breast tumor samples. Breast tumor tissue from 125 patients with germline mutations in BRCA1 (n = 33) or BRCA2 (n = 22) or with no detectable germline mutation in BRCA1 or BRCA2 (n = 70) were included in the study. Serving as a representative control group, primary breast tumor samples (n = 128) were randomly selected among available samples originating from the same department and time period as for the hereditary samples. The study was conducted using Agilent-029949 Custom SurePrint G3 Human GE 8x60K Microarray platform.

Project description:We have analyzed, using DNA microarrays, putative differences in gene-expression level between hereditary BRCA1 mutation-linked and sporadic breast cancer. Our results show that a previously reported marked difference between BRCA1-mutation linked and sporadic breast cancer was probably due to uneven stratification of samples with different ER status and basal-like versus luminal-like subtype. We observed that apparent difference between BRCA1-linked and other types of breast cancer found in univariate analysis was diminished when data were corrected for ER status and molecular subtype in multivariate analyses. In fact, the difference in gene expression pattern of BRCA1-mutated and sporadic cancer is very discrete. These conclusions were supported by the results of Q-PCR validation. We also found that BRCA1 gene inactivation due to promoter hypermethylation had similar effect on general gene expression profile as mutation-induced protein truncation. This suggests that in the molecular studies of hereditary breast cancer, BRCA1 gene methylation should be recognized and considered together with gene mutation. We analyzed 35 breast cancer specimens. Surgical samples obtained during mastectomy were flash-frozen in liquid nitrogen and stored at -80°C. Only samples from patients without neoadjuvant chemotherapy were used in this study as chemotherapy may seriously affect gene expression profile. All tissue samples were collected at the Pomeranian Medical University in Szczecin. Seventeen tumor samples were collected from patients with hereditary breast cancer: 12 were derived from tumors affecting women with hereditary BRCA1 mutation, the only one from a woman with BRCA2 mutation, while another eight cases had familial history of breast/ovarian cancer, but were negative for the BRCA1/2 mutations (so called BRCAx cases). Proportion of BRCA1 and BRCA2 mutated tumors was typical for the Polish population. Ten samples were derived from patients with apparently sporadic disease (no familial history of cancer) while 4 patients had a history of familial cancer aggregation (FCA) but without prevalence of breast/ovarian cancers. Thus, these samples were merged with sporadic samples in most of the analyses. All BRCA1 mutation-linked tumors in our study were negative for estrogen receptor (by immunohistochemistry, standard procedures for ER, PGR and HER2 staining were applied), while the only BRCA2-mutated tumor was ER-positive. There were 26 ductal and 5 medullary carcinomas within the study group, which is consistent with the distribution of histopathological types in BRCA1 mutation carriers. Patients were diagnosed at stage T1-2, N0-1 and M0. Caution: this submission contains the data from 6 microarrays done on the normal/pathologically unchanged breast tissue from breast cancer patiets. The data from normal tissues was not analyzed in the paper BRCA1-related gene signature in breast cancer is strongly influenced by ER status and molecular type by Lisowska et al., 2011, Front Biosci (Elite Ed). 2011 Jan 1;3:125-36

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Expression profiling of peripheral blood gene expression of women with hereditary breast cancer and controls (set 1)

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