In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.
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Question: Application of stem cell biology to breast cancer research has been limited by the lack of simple methods for identification and isolation of normal and malignant stem cells. Utilizing in vitro and in vivo experimental systems, we show that normal and cancer human mammary epithelial cells with increased aldehyde dehydrogenase activity (ALDH) have stem/progenitor properties. These cells contain the subpopulation of normal breast epithelium with the broadest lineage differentiation potential and greatest growth capacity in a xenotransplant model. In breast carcinomas, high ALDH activity identifies the tumorigenic cell fraction, capable of self-renewal and of generating tumors that recapitulate the heterogeneity of the parental tumor. In a series of 577 breast carcinomas, expression of ALDH1 detected by immunostaining correlated with poor prognosis. These findings offer an important new tool for the study of normal and malignant breast stem cells and facilitate the clinical application of stem cell concepts.

Answer: ALDH1 is a marker of normal and malignant human mammary stem cells and a predictor of poor clinical outcome.

Question: The gene-of-the-oligodendrocyte lineage (Golli)-MBP transcription unit contains three Golli-specific exons together with eight exons of the "classical" myelin basic protein (MBP) gene, yielding alternatively spliced proteins which share amino acid sequence with MBP. Unlike MBP, a late antigen expressed only in the nervous system, Golli gene products are expressed pre- and post-natally at many sites. In this study, we determined the sequence of Golli in rat by RT-PCR and 5' RACE and showed that Golli sequences are expressed in primary lymphoid organs as early as e16.5, which could explain the anergic rat T cell response we previously observed in Golli-induced meningitis.

Answer: Expression of Golli mRNA during development in primary immune lymphoid organs of the rat

Question: Allelic exclusion underpins antigenic variation and immune evasion in African trypanosomes. These bloodstream parasites use RNA polymerase-I (pol-I) to transcribe just one telomeric variant surface glycoprotein (VSG) gene at a time, producing superabundant and switchable VSG coats. We identified trypanosome VSG exclusion-1 (VEX1) using a genetic screen for defects in telomere-exclusive expression. VEX1 was sequestered by the active VSG and silencing of other VSGs failed when VEX1 was either ectopically expressed or depleted, indicating positive and negative regulation, respectively. Positive regulation affected VSGs and nontelomeric pol-I-transcribed genes, whereas negative regulation primarily affected VSGs. Negative regulation by VEX1 also affected telomeric pol-I-transcribed reporter constructs, but only when they contained blocks of sequence sharing homology with a pol-I-transcribed locus. We conclude that restricted positive regulation due to VEX1 sequestration, combined with VEX1-dependent, possibly homology-dependent silencing, drives a "winner-takes-all" mechanism of allelic exclusion.

Answer:
VEX1 controls the allelic exclusion required for antigenic variation in trypanosomes.