Functional variants at the 11q13 risk locus for breast cancer regulate cyclin D1 expression through long-range enhancers

Analysis of 4,405 variants in 89,050 European subjects from 41 case-control studies identified three independent association signals for estrogen-receptor-positive tumors at 11q13. The strongest signal maps to a transcriptional enhancer element in which the G allele of the best candidate causative variant rs554219 increases risk of breast cancer, reduces both binding of ELK4 transcription factor and luciferase activity in reporter assays, and may be associated with low cyclin D1 protein levels in tumors. Another candidate variant, rs78540526, lies in the same enhancer element. Risk association signal 2, rs75915166, creates a GATA3 binding site within a silencer element. Chromatin conformation studies demonstrate that these enhancer and silencer elements interact with each other and with their likely target gene, CCND1.

Abstract P2-11-01: Molecular Profiling Identifies Differentially Expressed Genes between Normal Breast Tissue from BRCA Carriers and Women at Population Risk

Background: Women found to carry a BRCA1 or BRCA2 gene mutation are at significant risk of future breast cancer (BC). Prophylactic mastectomy (PM) remains the most effective risk reducing strategy in that setting. Thus far, there are no data available identifying changes in gene expression profiles prior to the onset of BC in these women using microarray technology.

Material and methods : In this pilot study, we prospectively collected PM specimens from BRCA1/2 mutation carriers (n=21), and reduction mammoplasty (RM) specimens from healthy controls at population risk of breast cancer (n=13). Samples were collected from all 4 quadrants (fresh frozen) and careful histological examination was conducted. Selected samples (most dense parenchymal tissue) were sent for microarray analyses (19K chip, http://www.uhnres.utoronto.ca/facilities/index.htm). We compared the molecular profiles of breast tissue obtained from these two groups using two approaches: 1) microarray analysis for a global assessment of gene expression, and 2) gene set analysis to identify differences based on cellular function and biologic themes. Results: Women in each group were of similar age (p=NS). No invasive cancer was identified. In histologically normal breast tissue, class comparison identified differential gene expression between RM and PM tissues. Gene set analysis of five collections including MSigDB C2, C4, cytobands, Stanford 5Mb chromosomal tiles and KEGG database identified 22 significant gene sets. Nine sets were overexpressed and 13 sets were underexpressed in PM tissues (FDR < 0.2; p < 0.012). We found overexpression of genes relating to proliferation and transcription specifically in the PM tissues enriched for Gene Ontology annotations. The top 200 genes ranked by SAM were also examined by pathway analysis that showed high enrichment for cancer related pathways. All three approaches implicated T cell receptor signaling and a TSG101-stathmin breast cancer related pathway as contributing to the differential molecular profiles between RM and PM tissues.

Discussion: We have shown differential expression of single genes as well as cancer related biologic pathways (using microarray and gene set analyses) between normal breast tissue from BRCA1/2 mutation carriers (at high risk of BC) and healthy controls (at population risk of BC). These differences may represent early molecular defects of genetic pathways potentially involved in the early stages of breast carcinogenesis in women at hereditary high risk or may represent the result of BRCA1/2 haploinsufficiency. These results support the hypothesis that molecular pathways leading to BC formation are unique to BRCA1/2 carriers. This information may help the development of innovative preventive strategies for BRCA carriers in the future.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-11-01.

A Genomic Biomarker for Breast Cancer Development in High-Risk Women

BackgroundFamily history is an important factor contributing to a woman's risk of breast cancer development. This increased risk reflects the participation of inherited genetic components such as breast cancer susceptibility genes. However, many of the genetic components contributing to breast cancer remain unknown, and a number of women with a family history of breast cancer never develop breast cancer despite their high-risk status, while other high-risk woman go on to develop breast cancer. Thus, it is clear that we lack crucial pieces of information to help define a person's true risk of developing breast cancer.Methods and FindingsWe hypothesize that there are many undiscovered germline variations in genes that lead to altered gene expression patterns predictive of breast cancer development in high-risk women. We have developed a genomic model capable of predicting which high-risk women, both BRCA1/2 mutation carriers and BRCAX women, will actually develop breast cancer. Specifically, we use exon-level genome-wide expression profiling of peripheral blood mononuclear cells (PBMCs) to develop a model of disease risk (n=118 samples of either control or high-risk women). From this data, we generate a biomarker consisting of genes that most correlate to cancer development in women with strong family histories of breast cancer. Using an internal independent dataset, our biomarker can predict the high-risk women who will or will not develop cancer with over 85% accuracy. Further, we have validated this model on an independent external cohort (n=36) which was obtained and processed at sites unique to our training dataset. Our genomic biomarker can accurately predict breast cancer development in high-risk women with over 78% accuracy using this external dataset. Therefore, from our analyses, we can calculate with high accuracy an individual woman's true risk of developing breast cancer. This method provides a personalized approach to hereditary breast cancer risk assessment that is not currently available. This personalized risk assessment will aide clinicians in counseling their patients regarding specific management options based on a patient's individual risk of breast cancer. Lastly, these studies have also identified novel genes associated with breast cancer risk, which may provide a basis for targeted therapies that may help modify the risk of breast cancer development in high risk patients.ConclusionsTogether, these studies deliver both a non-invasive biomarker for hereditary breast cancer risk and a characterization of genes that contribute to breast cancer development. Overall, we expect these experiments to identify the genetic changes that underlie breast cancer predisposition, and assist clinicians and patients in determining the appropriate preventative measures based on their personal risk of developing breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4059.

Prognosis in BRCA1, BRCA2 associated breast cancer (BC): a prospective Breast Cancer Family Registry (BCFR) international population-based cohort study

Abstract #2072

Hereditary BC occurs at a younger age and is associated with more adverse tumor-related features than sporadic breast cancer (BC) (defined here as BC in those with no 1st or 2nd degree family history of breast or ovarian cancer). Using pre-specified criteria, we assembled a population-based cohort of newly diagnosed BC at 3 centers: Ontario, Canada (1996-98), San Francisco Bay area, USA (1995-2000), Melbourne/Sydney, Australia (1991-1998). Medical information was obtained from medical records; women were followed prospectively for recurrence, new cancers and death. Pathology data were obtained from central review or pathology reports. BRCA1 and BRCA2 mutation testing was performed on 77% and 70% of cases, respectively (sporadic BC cases were not tested at 2 centers). Hereditary and sporadic BC cases were compared using Cox proportional hazards (stratified by center). 3215 eligible cases were enrolled in the BCFR, with a mean age at diagnosis of 46.9 years. Median follow-up was 7.61 years; 565 women had distant recurrences and 547 died. There were 92 cases with BRCA1 and 72 with BRCA2 mutations; 1549 (48.2%) had sporadic BC; the remainder had familial BC as defined above. BRCA1 mutations were associated with young age, estrogen and progesterone receptor (ER and PgR) negativity and high grade; BRCA2 mutations were associated with node positivity and high grade. Distant disease-free survival (DDFS) and overall survival (OS) did not differ significantly between BRCA1 carriers and sporadic cases in univariate or multivariate analyses. DDFS and OS were worse in BRCA2 carriers than in sporadic cases (HR 1.6, p=0.04 and HR 1.8, p=0.01, respectively) in univariate analyses but not in multivariate analyses (DDFS HR 1.0, p=0.98; OS HR 1.13, p=0.61). The small group of BRCA2 carriers who did not receive adjuvant chemotherapy had a significantly worse OS (multivariate HR 3.63, p = 0.005). Furthermore, BRCA2 carriers who received adjuvant tamoxifen had significantly worse OS than women with sporadic BC (HR=2.0, p=0.03). We conclude that BRCA1 and BRCA2 mutations do not independently impact DDFS or OS. Significantly worse outcomes were seen in BRCA2 carrier subgroups defined by adjuvant treatment; this requires further investigation and may have implications for clinical practice.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2072.

Oral contraceptive use and ovarian cancer risk among carriers of BRCA1 or BRCA2 mutations

Women with mutations of the genes BRCA1 or BRCA2 are at increased risk of ovarian cancer. Oral contraceptives protect against ovarian cancer in general, but it is not known whether they protect against the disease in carriers of these mutations. We obtained self-reported lifetime histories of oral contraceptive use from 451 women who carried mutations of BRCA1 or BRCA2. We used conditional logistic regression to estimate the odds ratios associated with oral contraceptive use, comparing the histories of 147 women with ovarian cancer (cases) to those of 304 women without ovarian cancer (controls) who were matched to cases on year of birth, country of residence and gene (BRCA1 vs BRCA2). Reference ages for controls had to exceed the ages at diagnosis of their matched cases. After adjusting for parity, the odds-ratio for ovarian cancer associated with use of oral contraceptives for at least 1 year was 0.85 (95 percent confidence interval, 0.53–1.36). The risk decreased by 5% (1–9%) with each year of use (P for trend=0.01). Use for 6 or more years was associated with an odds-ratio of 0.62 (0.35–1.09). These data support the hypothesis that long-term oral contraceptive use reduces the risk of ovarian cancer among women who carry mutations of BRCA1 or BRCA2.

Comparison of HER2/neu status assessed by quantitative polymerase chain reaction and immunohistochemistry

We prospectively evaluated a series of 254 breast cancers by quantitative polymerase chain reaction (PCR) and immunohistochemistry using 3 antibodies: HercepTest, CB11, and TAB250. DNA was extracted from a 10-micron tumor section for PCR, and 4-micron serial sections were taken from the same block for immunohistochemistry. The immunohistochemical results were scored using a semiquantitative immunohistochemical system. A positive tumor by immunohistochemistry had a score of 5 or more. The manufacturer's recommended scoring system was used for the HercepTest. Tumors were positive for gene amplification if the ratio of the HER2/neu gene to control gene after normalization was 2 or more. Of 254 cases, 61 showed gene amplification. For immunohistochemistry, 23% of tumors were positive with CB11, 27% with TAB250, and 37% with the HercepTest. Results for each antibody were compared with PCR results. The overall concordance for the HercepTest was 82%, which was significantly lower than that for CB11 (88%) or TAB250 (87%). The specificity for the HercepTest was 80% compared with 90% for TAB250 and 93% for CB11, while the positive predictive value for the HercepTest was 57% compared with 71% and 76% for TAB250 and CB11, respectively.

Methylation of the BRCA1 promoter is associated with decreased BRCA1 mRNA levels in clinical breast cancer specimens

Functional inactivation of BRCA1 is an important mechanism involved in breast cancer pathogenesis. Mutation is often responsible for BRCA1 inactivation in familial breast cancer, but is not responsible for the decreased levels of BRCA1 seen in a subset of sporadic breast cancer patients. To determine if aberrant cytosine methylation of the BRCA1 promoter is associated with decreased BRCA1 gene expression in human breast cancer, high resolution bisulfite sequence analysis was used to analyze the cytosine methylation status of the BRCA1 promoter in 21 axillary node negative breast cancer patients with known levels of BRCA1 expression. Aberrant cytosine methylation of the BRCA1 promoter was detected in three of 21 patient specimens. These three specimens also expressed the lowest levels of BRCA1. Results from this analysis show that aberrant cytosine methylation of the BRCA1 promoter is directly correlated with decreased levels of BRCA1 expression in human breast cancer, and suggest that epigenetic silencing may be one mechanism of transcriptional inactivation of BRCA1 in sporadic mammary carcinogenesis.

Molecular alterations in bone and soft-tissue sarcoma

Understanding the molecular alterations evident in human cancer offers the potential for more meaningful diagnosis and more accurate prediction of cancer risk as well as the hope of developing novel therapies. In this review, several of the molecular abnormalities identified in both bone and soft-tissue sarcoma are outlined. Some sarcomas exhibit consistent gene translocations, which produce a unique oncoprotein that can serve as a molecular fingerprint for the sarcoma subtype. Mutations in tumour suppressor genes result in cell proliferation that is not regulated by normal cell cycle control genes. Amplification (multiple copies) of genes that act as positive controls on cell division have a similar effect on increasing cell proliferation. Finally, the understanding of drug resistance and sarcoma response to signalling systems such as IGF ligand and receptors may help in designing new therapies based on molecular changes in the cancer.

Phase II study of dexverapamil plus anthracycline in patients with metastatic breast cancer who have progressed on the same anthracycline regimen

The purpose of this study is to evaluate whether metastatic breast cancer that has progressed on an anthracycline-containing drug regimen will subsequently respond to that identical regimen if dexverapamil, a modulator of P-glycoprotein-mediated drug resistance, is given concomitantly. Eligible patients received 180 mg/m2 dexverapamil every 6 h for 15 doses with the anthracycline administered 30 min after the seventh dose. Blood for dexverapamil levels was drawn before and 30 min after this dose. When possible, biopsies were obtained to measure mdr-1 expression by reverse transcription-PCR and by image cytometry. Of the 21 patients entered onto the trial, 20 were evaluable for response. There were two partial responses (10%) that both lasted for 6 months, and two additional patients had stable disease. Seven patients had asymptomatic cardiotoxicity consisting of hypotension (24%), bradycardia (5%), or prolongation of the P-R interval (14%). Two patients developed acute congestive heart failure, one on dexverapamil and one 10 days after stopping it. Dexverapamil did not seem to increase anthracycline toxicity. The median trough dexverapamil plus norverapamil level on day 3 was 1110 ng/ml (range, 186-3385 ng/ml), and the median peak level was 2164 ng/ml (range, 964-8382 ng/ml). There was poor correlation between reverse transcription-PCR and image cytometry for the level of mdr-1 expression. Because dexverapamil has been shown to affect doxorubicin pharmacokinetics subsequent to the initiation of this trial, it cannot be concluded that the responses seen were necessarily due to P-glycoprotein inhibition. Additional studies are necessary to determine whether mdr-1 modulators can reverse clinical drug resistance in breast cancer patients. The intrinsic cardiotoxicity of dexverapamil makes it less suitable for such studies than several other available agents.

EWS-FLI1 fusion transcript structure is an independent determinant of prognosis in Ewing's sarcoma

PURPOSE

More than 90% of Ewing's sarcomas (ES) contain a fusion of the EWS and FLI1 genes, due to the t(11;22)(q24;q12) translocation. At the molecular level, the EWS-FLI1 rearrangements show great diversity. Specifically, many different combinations of exons from EWS and FLI1 encode in-frame fusion transcripts and result in differences in the length and composition of the chimeric protein, which functions as an oncogenic aberrant transcription factor. In the most common fusion type (type 1), EWS exon 7 is linked in frame with exon 6 of FLI1. As the fundamental pathogenetic lesion in ES, the molecular heterogeneity of these fusion transcripts may have functional and clinical significance.

PATIENTS AND METHODS

We performed a clinical and pathologic analysis of 112 patients with ES in which EWS-FLI1 fusion transcripts were identified by reverse-transcriptase polymerase chain reaction (RT-PCR). Adequate treatment and follow-up data were available in 99 patients treated with curative intent. Median follow-up in these 99 patients was 26 months (range, 1 to 140 months). Univariate and multivariate survival analyses were performed that included other prognostic factors, such as age, tumor location, size, and stage.

RESULTS

Among the 99 patients suitable for survival analysis, the tumors in 64 patients contained the type 1 fusion and in 35 patients contained less common fusion types. Stage at presentation was localized in 74 patients and metastatic in 25. Metastases (relative risk [RR] = 2.6; P = .008), and type 1 EWS-FLI1 fusion (RR = 0.37; P = .014) were, respectively, independent negative and positive prognostic factors for overall survival by multivariate analysis. Among 74 patients with localized tumors, the type 1 EWS-FLI1 fusion was also a significant positive predictor of overall survival (RR = 0.32; P = .034) by multivariate analysis.

CONCLUSION

EWS-FLI1 fusion type appears to be prognostically relevant in ES, independent of tumor site, stage, and size. Further studies are needed to clarify the biologic basis of this phenomenon.

Metastatic behavior of the RIF-1 murine fibrosarcoma: inhibited by hypophysectomy and partially restored by growth hormone replacement

BACKGROUND

We recently demonstrated that hypophysectomy profoundly inhibits metastatic behavior in the MGH-OGS murine osteosarcoma model and speculated that this effect is related at least in part to ablation of the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis.

PURPOSE

In this study, we determined whether the administration of GH to animals rendered GH and IGF-I deficient by hypophysectomy attenuates the inhibitory effects of hypophysectomy on metastatic behavior.

METHODS

Metastatic behavior was assayed by counting visible metastases in lungs 3 weeks after tail vein injection of RIF-I fibrosarcoma cells to control mice (n = 29), hypophysectomized mice (n = 19), and hypophysectomized mice administered 0.05 microgram/g body weight recombinant human GH twice daily (n = 21).

RESULTS

Twenty of 21 hypophysectomized mice receiving GH, eight of 19 hypophysectomized mice not receiving GH, and 26 of 29 controls had grossly visible pulmonary metastases 3 weeks after intravenous injection of 5 x 10(5) cells; mean numbers +/- SD of gross metastases were 38.4 +/- 11.3, 6.4 +/- 2.2, and 13.1 +/- 2.8 in the three groups, respectively. The presence (P < .005, chi-square test) and number (P = .0003, Mann-Whitney U test) of metastases were significantly reduced in hypophysectomized hosts compared with control hosts and were significantly higher in hypophysectomized, GH-replaced hosts compared with hypophysectomized hosts (P < .001, chi-square test; P = .011, Mann-Whitney U test), while the difference in presence and extent of metastases between control and hypophysectomized, GH-replaced hosts was not statistically significant.

CONCLUSIONS

These data support the hypothesis that the status of the host with respect to GH and/or GH-dependent factors such as IGF-I influences the metastatic behavior of certain neoplasms.

IMPLICATIONS

Our results raise the possibility that compounds that reduce GH output or interfere with GH action, such as somatostatin analogues, GH antagonists, IGF antagonists, and GH-releasing hormone antagonists, may suppress metastatic behavior of certain neoplasms.

Expression and amplification of neu oncogene in pleomorphic adenomas of salivary gland

Amplification of the neu oncogene and overexpression of its product was found to be a potential marker for aggressive biological behavior in breast cancer. However, the expression of the neu oncoprotein in normal breast ducts and myoepithelial cells has also been demonstrated. Hence, we examined normal salivary gland tissue and 15 cases of pleomorphic adenoma for the expression of the neu oncoprotein by immunohistochemistry using two polyclonal antibodies and 12 cases for the amplification of the neu oncogene using slot blot hybridization. Immunohistochemistry in the normal salivary gland revealed positive staining of all ductal cells. In the pleomorphic adenomas all cellular elements stained to a variable degree. The positive staining was seen in the ductal cells, in the solid sheets, and in chondroid, myxoid, and metaplastic foci. The normal salivary gland and 11 of 12 cases of pleomorphic adenoma showed no increase in copy number of the neu oncogene, whereas one case showed threefold amplification. These results indicate that the neu oncoprotein is expressed but the neu copy number is not increased in normal salivary gland epithelium and in most pleomorphic adenomas. The threefold amplification of the gene in one case may indicate an aggressive biological behavior.

Distribution and patterns of staining of Neu oncogene product in benign and malignant breast diseases

Amplification of the Neu oncogene (c-erbB-2) has been reported by various researchers as a marker for poor clinical outcome in patients with breast cancer. We have performed immunohistochemical staining using a polyclonal antibody to the Neu oncoprotein on formalin-fixed material from normal breast, benign breast lesions, and 102 stage I node-negative breast cancers. Hybridization studies were also performed on 66 of the breast cancer cases. In the cancers 33% of cases showed positive staining of the in situ and invasive component, whereas only 25% of cases showed amplification of the Neu oncogene. The staining pattern in the tumor cells was cytoplasmic with plasma membrane accentuation. Focal positive cytoplasmic staining was noted in some cases of fibrocystic disease, fibroadenoma, and normal breast duct epithelium. Myoepithelial cells and smooth muscle of blood vessels also showed a positive reaction. This study shows that the Neu oncoprotein can be demonstrated on formalin-fixed material from normal, benign, and malignant breast lesions. In the breast cancers the differences in the number of cases showing amplification and those showing a positive immunohistochemical reaction could be due to increased transcriptional activity. It is possible that the node-negative patients whose tumors express the Neu oncogene may correspond to the group of patients who are expected to have a poor prognosis.