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1.  Sequencing of breast cancer stem cell populations indicates a dynamic conversion between differentiation states in vivo 
Introduction
The cancer stem cell model implies a hierarchical organization within breast tumors maintained by cancer stem-like cells (CSCs). Accordingly, CSCs are a subpopulation of cancer cells with capacity for self-renewal, differentiation and tumor initiation. These cells can be isolated through the phenotypic markers CD44+/CD24-, expression of ALDH1 and an ability to form nonadherent, multicellular spheres in vitro. However, controversies to describe the stem cell model exist; it is unclear whether the tumorigenicity of CSCs in vivo is solely a proxy for a certain genotype. Moreover, in vivo evidence is lacking to fully define the reversibility of CSC differentiation.
Methods
In order to answer these questions, we undertook exome sequencing of CSCs from 12 breast cancer patients, along with paired primary tumor samples. As suggested by stem classical cell biology, we assumed that the number of mutations in the CSC subpopulation should be lower and distinct compared to the differentiated tumor cells with higher proliferation.
Results
Our analysis revealed that the majority of somatic mutations are shared between CSCs and bulk primary tumor, with similar frequencies in the two.
Conclusions
The data presented here exclude the possibility that CSCs are only a phenotypic consequence of certain somatic mutations, that is a distinct and non-reversible population of cells. In addition, our results imply that CSCs must be a population of cells that can dynamically switch from differentiated tumor cells, and vice versa. This finding increases our understanding of CSC function in tumor heterogeneity and the importance of identifying drugs to counter de-differentiation rather than targeting CSCs.
doi:10.1186/bcr3687
PMCID: PMC4227057  PMID: 24998755
2.  Breast Cancer in Young Women: Poor Survival Despite Intensive Treatment 
PLoS ONE  2009;4(11):e7695.
Background
Breast cancer is uncommon in young women and correlates with a less favourable prognosis; still it is the most frequent cancer in women under 40, accounting for 30–40% of all incident female cancer. The aim of this study was to study prognosis in young women, quantifying how much stage at diagnosis and management on the one hand, and tumour biology on the other; each contribute to the worse prognosis seen in this age group.
Methodology/Principal Findings
In a registry based cohort of women aged 20–69 (n = 22 017) with a primary diagnosis of invasive breast cancer (1992–2005), women aged 20–34 (n = 471), 35–39 (n = 858) and 40–49 (n = 4789) were compared with women aged 50–69 years (n = 15 899). The cumulative 5-year relative survival ratio and the relative excess mortality (RER) were calculated. The cumulative 5-year relative survival ratio was lowest in women aged 20–34. The RER was 2.84 for women aged 20–34 and decreased with increasing age (RER 1.76 and 1.17 for women aged 35–39 and 40–49, respectively). The excess risk was, however, present only in disease stages I and II. For women aged 20–34 with stage I disease RER was 4.63, and 6.70 in the subgroup with tumour size 1–10 mm. The absolute difference in stage I between the youngest and the reference groups amounted to nearly 8%, with a 90% 5-year survival in women aged 20–34. In stages IIa and IIb, the relative excess risk was not as dramatic, but the absolute differences approached 15%. The youngest women with small tumours generally received more aggressive treatment than women in older age groups.
Conclusions
After correction for stage, tumour characteristics and treatment, age remained an independent risk factor for breast cancer death in women <35 years of age. The excess risk for young women was only seen in early stages of disease and was most pronounced in women with small tumours. Young women affected by breast cancer have a high risk of dying compared to their middle-aged counterparts even if diagnosed early and receiving an intense treatment.
doi:10.1371/journal.pone.0007695
PMCID: PMC2770847  PMID: 19907646
3.  Gene expression profiling in primary breast cancer distinguishes patients developing local recurrence after breast-conservation surgery, with or without postoperative radiotherapy 
Introduction
Some patients with breast cancer develop local recurrence after breast-conservation surgery despite postoperative radiotherapy, whereas others remain free of local recurrence even in the absence of radiotherapy. As clinical parameters are insufficient for identifying these two groups of patients, we investigated whether gene expression profiling would add further information.
Methods
We performed gene expression analysis (oligonucleotide arrays, 26,824 reporters) on 143 patients with lymph node-negative disease and tumor-free margins. A support vector machine was employed to build classifiers using leave-one-out cross-validation.
Results
Within the estrogen receptor-positive (ER+) subgroup, the gene expression profile clearly distinguished patients with local recurrence after radiotherapy (n = 20) from those without local recurrence (n = 80 with or without radiotherapy). The receiver operating characteristic (ROC) area was 0.91, and 5,237 of 26,824 reporters had a P value of less than 0.001 (false discovery rate = 0.005). This gene expression profile provides substantially added value to conventional clinical markers (for example, age, histological grade, and tumor size) in predicting local recurrence despite radiotherapy. Within the ER- subgroup, a weaker, but still significant, signal was found (ROC area = 0.74). The ROC area for distinguishing patients who develop local recurrence from those who remain local recurrence-free in the absence of radiotherapy was 0.66 (combined ER+/ER-).
Conclusion
A highly distinct gene expression profile for patients developing local recurrence after breast-conservation surgery despite radiotherapy has been identified. If verified in further studies, this profile might be a most important tool in the decision making for surgery and adjuvant therapy.
doi:10.1186/bcr1997
PMCID: PMC2397536  PMID: 18430221

Results 1-3 (3)