Breast Cancer Research - Latest Articles

Amphiregulin mediates progesterone-induced mammary ductal development during puberty

Mark Aupperlee — 2013-05-25T00:00:00Z

IntroductionPuberty is a period of increased susceptibility to factors that cause increased breast cancer risk in adulthood. Mammary end buds (EB) that develop during puberty are believed to be the targets of breast cancer initiation. While the role of estrogen (E) has been extensively studied in pubertal mammary gland development, the role of progesterone (P) during puberty is less defined. Methods: Pubertal and pre-pubertal ovariectomized mice were treated with vehicle control (C), E, P or E+P. Mammary glands from these mice were analyzed for changes in morphology, proliferation, and expression of the downstream targets amphiregulin (AREG) and Receptor Activator of NF-kB Ligand (RANKL). Results: P, acting specifically through the progesterone receptor, induced increases in mammary gland proliferation and EB formation that were associated with increased AREG expression in ducts and EBs. E, acting specifically through the estrogen receptor, produced similar responses also mediated by AREG. Blocking AREG action by treatment with an epidermal growth factor receptor (EGFR) inhibitor completely abrogated the effect of P on EB formation and proliferation and significantly reduced proliferation within ducts. P also increased expression of RANKL, primarily in ducts. Treatment with RANK-Fc, an inhibitor of RANKL, reduced P-dependent proliferation in ducts and to a lesser extent in EB, but did not cause EB regression. Conclusions: These results demonstrate a novel P-specific effect through AREG to cause EB formation and proliferation in the developing mammary gland both prior to and during puberty. Thus, hormones and/or factors in addition to E that up-regulate AREG can promote mammary gland development and have the potential to affect breast cancer risk associated with pubertal mammary gland development.

Mammographic density and breast cancer: a comparison of related and unrelated controls in the breast cancer family registry

Linda Linton — 2013-05-25T00:00:00Z

IntroductionPercent mammographic density (PMD) is a strong and highly heritable risk factor for breast cancer. Studies of the role of PMD in familial breast cancer may require controls, such as the sisters of cases, selected from the same "risk set" as the cases. The use of sister controls would allow control for factors that have been shown to influence risk of breast cancer such as race/ethnicity, socio-economic status and a family history of breast cancer, but may introduce "overmatching" and attenuate case-control differences in PMD. Methods: To examine the potential effects of using sister controls rather than unrelated controls in a case-control study we examined PMD in triplets, each comprised of a case with invasive breast cancer, an unaffected full sister control, and an unaffected unrelated control. Both controls were matched to cases on age at mammogram. Total breast area and dense area in the mammogram were measured in the unaffected breast of cases and a randomly selected breast in controls, and the non-dense area and PMD calculated from these measurements. Results: The mean difference in PMD between cases and controls, and the standard deviation (SD) of the difference, were slightly less for sister controls (4.2% (SD=20.0)) than for unrelated controls (4.9% (SD=25.7)). We found statistically significant correlations in PMD between cases (n=228) and sister controls (n=228) (r= 0.39 (95% CI: 0.28, 0.50; p<0.0001)), but not between cases and unrelated controls (n=228) (r= 0.04 (95% CI: -0.09, 0.17; p=0.51)). After adjusting for other risk factors, square root transformed PMD was associated with an increased risk of breast cancer when comparing cases to sister controls (adjusted odds ratio (inter-quintile odds ratio (IQOR) = 2.19, 95% CI= 1.20, 4.00) or to unrelated controls (adjusted IQOR= 2.62, 95% CI= 1.62, 4.25). Conclusions: The use of sister controls in case-control studies of PMD resulted in a modest attenuation of case-control differences and risk estimates, but showed a statistically significant association with risk and allowed control for race/ethnicity, socio-economic status and family history.

Serum microRNA expression as an early marker for breast cancer risk in prospectively collected samples from the Sister Study cohort

Ashley Godfrey — 2013-05-24T00:00:00Z

IntroductionMicroRNAs (miRNAs) are small, non-coding, single-stranded RNAs between 18-22 nucleotides long that regulate gene expression. Expression of miRNAs is altered in tumors compared to normal tissue; there is some evidence that these changes may be reflected in the serum of cancer cases compared to healthy individuals. This has yet to be examined in a prospective study where samples are collected before diagnosis. Methods: We used Affymetrix arrays to examine serum miRNA expression profiles in 410 participants in the Sister Study, a prospective cohort study of 50,884 women. All women in the cohort had never been diagnosed with breast cancer at the time of enrollment. We compared global miRNA expression patterns in 205 women who subsequently developed breast cancer and 205 women who remained breast cancer-free. In addition within the case group we examined the association of miRNA expression in serum with different tumor characteristics, including hormone status (Estrogen Receptor, ER; Progesterone Receptor, PR; Human Epidermal Growth Factor Receptor 2, HER-2) and lymph node status. Results: Overall, 414 of 1,105 of the human miRNAs on the chip were expressed above background levels in 50 or more women. When the average expression among controls was compared to cases using conditional logistic regression, 21 miRNAs were found to be differentially expressed (P[less than or equal to].05). Using qRT-PCR on a small, independent sample of 5 cases and 5 controls we verified overexpression of the 3 highest expressing miRNAs among cases, miR-18a, miR-181a, and miR-222; the differences were not statistically significant in this small set. The 21 differentially expressed miRNAs are known to target at least 82 genes; using the gene list for pathway analysis we found enrichment of genes involved in cancer-related processes. In a separate case-case analyses restricted to the 21 miRNAs, we found 7 miRNAs with differential expression for women whose breast tumors differed by HER-2 expression, and 10 miRNAs with differential expression by nodal status. Conclusions: miRNA levels in serum show a number of small differences between women who later develop cancer versus those who remain cancer-free.

Overdiagnosis in breast cancer screening: the importance of length of observation period and lead time

Stephen Duffy — 2013-05-16T00:00:00Z

IntroductionOverdiagnosis in breast cancer screening is a controversial topic. One difficulty in estimation of overdiagnosis is the separation of overdiagnosis from lead time that is the advance in the time of diagnosis of cancers, which confers an artificial increase in incidence when a screening programme is introduced. Methods: We postulated a female population aged 50-79 with a similar age structure and age-specific breast cancer incidence as in England and Wales before the screening programme. We then imposed a two-yearly screening programme; screening women aged 50-69, to run for twenty years, with exponentially distributed lead time with an average of 40 months in screen-detected cancers. We imposed no effect of the screening on incidence other than lead time. Results: Comparison of age- and time-specific incidence between the screened and unscreened populations showed a major effect of lead time, which could only be adjusted for by follow-up for more than two decades and including ten years after the last screen. From lead time alone, twenty-year observation at ages 50-69 would confer an observed excess incidence of 37%. The excess would only fall below 10% with 25 years or more follow-up. For the excess to be nullified, we would require 30 year follow-up including observation up to 10 years above the upper age limit for screening. Conclusions: Studies using shorter observation periods will overestimate overdiagnosis by inclusion of cancers diagnosed early due to lead time among the nominally overdiagnosed tumours.

Illuminating Luminal B: QSOX1 as a subtype-specific biomarker

Padmalaya Das — 2013-05-15T00:00:00Z

Breast cancer is a complex and heterogeneous disease that affects about one out of every eight women. In the last decade, several advancements have been made that have increased our understanding of breast cancer and have allowed us to more accurately diagnose and treat this disease in a more targeted manner. For example, gene expression profiling enabled the classification of breast cancers into four main subtypes - basal-like, HER2+ (human epidermal growth factor receptor 2-positive), luminal A and luminal B - and this classification is used to direct the use of targeted therapies such as tamoxifen or trastuzumab. The luminal subtypes are generally characterized as being estrogen receptor-positive and targetable with anti-hormone therapies. However, whereas luminal A cancers have a good prognosis, luminal B cancers are associated with early relapse following endocrine therapy and a prognosis that is similar to that of the aggressive basal subtype. It is thus imperative that luminal B cancers be better characterized so that therapeutic targets and biomarkers for this disease type can be realized. In the previous issue of Breast Cancer Research, Katchman and colleagues address this need by demonstrating that quiescin sulfydryl oxidase 1 (QSOX1), a secreted enzyme involved in post-translational modifications, is associated with poor prognosis in patients with luminal B breast cancer. The authors further determined that this protein promotes breast cancer proliferation and invasion. Collectively, these studies suggest that QSOX1 is a predictive biomarker for luminal cancers and that it may be a useful target for elusive luminal B disease.

High mammographic density in women of Ashkenazi Jewish descent

Jennifer Caswell — 2013-05-13T00:00:00Z

IntroductionPercent mammographic density (PMD) adjusted for age and BMI is one of the strongest risk factors for breast cancer and is known to be approximately 60 percent heritable. Here we report a finding of an association between genetic ancestry and adjusted PMD. Methods: We selected self-identified Caucasian women in the California Pacific Medical Center Research Institute Cohort whose screening mammograms placed them in the top or bottom quintiles of age- and body mass index-adjusted PMD. Our final data set included 474 women with the highest adjusted PMD and 469 with the lowest genotyped on the Illumina 1M platform. Principal component analysis (PCA) and identity-by-descent (IBD) analyses allowed us to infer the women's genetic ancestry and correlate it with adjusted PMD. Results: Women of Ashkenazi Jewish ancestry, as defined by the first principal component (PC1) of PCA and identity-by-descent analyses, represented approximately 15 percent of the sample. Ashkenazi Jewish ancestry, defined by PC1, was associated with higher adjusted PMD (p = 0.004). Using multivariate regression to adjust for epidemiologic factors associated with PMD, including age at parity and use of postmenopausal hormone therapy, did not attenuate the association. Conclusion: Women of Ashkenazi Jewish ancestry based on genetic analysis are more likely to have high age- and BMI-adjusted PMD. Ashkenazi Jews may have a unique set of genetic variants or environmental risk factors that increase mammographic density.

The expression and significance of insulin-like growth factor-1 receptor and its pathway on breast cancer stem/progenitors

Wen-Wei Chang — 2013-05-12T00:00:00Z

IntroductionDysregulation of the insulin-like growth factor-1 receptor (IGF-1R)/ PI3K/Akt pathway was shown to correlate with breast cancer disease progression. Cancer stem cells (CSCs) are a subpopulation within cancer cells which participate in tumor initiation, radio/chemoresistance and metastasis. In breast cancer, breast CSCs (BCSCs) were identified as CD24-CD44+ cells or cells with high intracellular aldehyde dehydrogenase activity (ALDH+). Elucidation of the role of IGF-1R in breast cancer stem cells (BCSCs) is crucial to the design of breast cancer therapies targeting BCSCs. Methods: IGF-1R expression in BCSCs and non-CSCs sorted from xenografts of human primary breast cancers was examined by FACS, western blot analysis and immunoprecipitation (IP). The role of IGF-1R in BCSCs was assessed by IGF-1R blockade with chemical inhibitor and gene silencing. The involvement of PI3K/Akt/mTOR as downstream pathway was studied by their phosphorylation status upon IGF-1R inhibition and the effects of chemical inhibitors of these signaling molecules on BCSCs. We also studied 16 clinical specimens of breast cancer for the expression of phosphor-Akt in the BCSCs by FACS. Results: Expression of phosphorylated IGF-1R was greater in BCSCs than in non-BCSCs from xenografts of human breast cancer which were supported by western blot and IP experiments. The sorted IGF-1R expressing cells displayed features of cancer stem/progenitors such as mammosphere formation in vitro and tumorigenicity in vivo, both of which were suppressed by knockdown of IGF-1R. A specific inhibitor of the IGF-1R, PPP, suppressed the phospho-AktSer473 and preferentially decreased ALDH+ BCSC populations of human breast cancer cells. Furthermore, PPP inhibited the capacity of CD24-CD44+ BCSCs to undergo epithelial-mesenchymal transition process with downregulation of mesenchymal markers. Inhibitors of signal molecules downstream of IGR-1R including PI3K/Akt/mTOR also reduced the ALDH + population of breast cancer cells. Furthermore, the mTOR inhibitor, rapamycin, suppressed BCSCs in vitro and in vivo. Conclusions: Our data support the notion that IGF-1R is a marker of stemness, and IGF-1R and its downstream PI3K/Akt/mTOR pathway are attractive targets for therapy directed against breast cancer stem/progenitors.

Progesterone metabolites regulate induction, growth and suppression of estrogen- and progesterone receptor-negative human breast cell tumors

John Wiebe — 2013-05-11T00:00:00Z

IntroductionOf the nearly 1.4 million new cases of breast cancer diagnosed each year, a large proportion is characterized as hormone receptor negative, lacking estrogen receptors (ER) and/or progesterone receptors (PR). Patients with receptor-negative tumors do not respond to current steroid hormone based therapies and generally have significantly higher risk of recurrence and mortality compared to patients with tumors that are ER- and/or PR-positive. Previous in vitro studies had shown that the progesterone metabolites, 5alpha-dihydroprogesterone (5alphaP) and 3alpha-dihydroprogesterone (3alphaHP), respectively, exhibit pro-cancer and anti-cancer effects on receptor-negative human breast cell lines. Here in vivo studies were conducted to investigate the ability of 5alphaP and 3alphaHP to control initiation, growth and regression of ER/PR-negative human breast cell tumors. Methods: ER/PR-negative human breast cells (MDA-MB-231) were implanted into mammary fat pads of immunosuppressed mice and the effects of 5alphaP and 3alphaHP treatments on tumor initiation, growth, suppression/regression and histopathology were assessed in five separate experiments. Specific radioimmunoassays and gas chromatography-mass spectrometry were used to measure 5alphaP, 3alphaHP and progesterone in mouse serum and tumors. Results: Onset and growth of ER/PR-negative human breast cell tumors were significantly stimulated by 5alphaP and inhibited by 3HP. When both hormones were applied simultaneously, the stimulatory effects of 5P were abrogated by the inhibitory effects of 3alphaHP and vice versa. Treatment with 3alphaHP subsequent to 5alphaP-induced tumor initiation resulted in suppression of further tumorigenesis and regression of existing tumors. The levels of 5alphaP in tumors, regardless of treatment, were about 10-fold higher than the levels of 3alphaHP and the 5alphaP:3alphaHP ratios were about 5-fold higher than in serum, indicating significant changes in endogenous synthesis of these hormones in tumorous breast tissues. Conclusions: The studies showed that estrogen/progesterone insensitive breast tumors are sensitive to, and controlled by, the progesterone metabolites 5alphaP and 3alphaHP. Tumorigenesis of ER/PR-negative breast cells is significantly enhanced by 5alphaP and suppressed by 3alphaHP, the outcome depending upon the relative concentrations of these two hormones in the microenvironment in the breast regions. The findings show that the production of 5alphaP greatly exceeds that of 3alphaHP in ER/PR-negative tumors and that treatment with 3alphaHP can effectively block tumorigenesis and regress existing tumors. The results provide the first hormonal theory to explain tumorigenesis of ER/PR-negative breast tissues and support the hypothesis that a high 3alphaHP-to-5alphaP concentration ratio in the microenvironment may foster normalcy in non-cancerous breast regions. The findings suggest new diagnostics based on the relative levels of these hormones and new approaches to prevention and treatment of breast cancers based on regulating the levels and action mechanisms of anti- and pro-cancer progesterone metabolites.

Molecular apocrine breast cancers are aggressive estrogen receptor negative tumors overexpressing either HER2 or GCDFP15

Jacqueline Lehmann-Che — 2013-05-11T00:00:00Z

IntroductionMolecular apocrine (MA) tumors are estrogen receptor (ER) negative breast cancers characterized by androgen receptor (AR) expression. We analysed a group of 58 transcriptionally defined MA tumors and proposed a new tool to identify these tumors. Methods: We performed quantitative reverse transcription PCR (qRT-PCR) for ER, AR, FOXA1 and AR-related genes, and immunohistochemistry (IHC) for ER, PR, HER2, CK5/6, CK17, EGFR, Ki67, AR, FOXA1 and GCDFP15 and we analysed clinical features. Results: MA tumors were all characterized by ER(-) AR(+) FOXA1(+) and AR-related genes positive mRNA profile. IHC staining on these tumors showed 93% ER(-), only 58% AR(+) and 90% FOXA1(+). 67% and 57% MA tumors were HER2(3+) and GCDFP15(+), respectively. Almost all MA tumors (94%) had the IHC signature "HER2(3+) or GCDFP15(+)" but none of 13 control basal-like (BL) tumors did. Clinically, MA tumors were rather aggressive, with poor prognostic factors. Conclusion: MA tumors could be better defined by their qRT-PCR-AR profile than by AR IHC. In addition, we found that "HER2 or GCDFP15" protein overexpression is a sensitive and specific tool to differentiate MA from BL in the context of ER negative tumors. A composite molecular and IHC signature could therefore help to identify MA tumors in the daily practice.

Delivery of gene silencing agents for breast cancer therapy

Haifa Shen — 2013-05-08T00:00:00Z

The discovery of RNA interference has opened the door for the development of a new class of cancer therapeutics. Small inhibitory RNA oligos are being designed to specifically suppress expression of proteins that are traditionally considered nondruggable, and microRNAs are being evaluated to exert broad control of gene expression for inhibition of tumor growth. Since most naked molecules are not optimized for in vivo applications, the gene silencing agents need to be packaged into delivery vehicles in order to reach the target tissues as their destinations. Thus, the selection of the right delivery vehicles serves as a crucial step in the development of cancer therapeutics. The current review summarizes the status of gene silencing agents in breast cancer and recent development of candidate cancer drugs in clinical trials. Nanotechnology-based delivery vectors for the formulation and packaging of gene silencing agents are also described.