YB-1 provokes breast cancer through the induction of chromosomal instability that emerges from mitotic failure and centrosome amplification.

YB-1 protein levels are elevated in most human breast cancers, and high YB-1 levels have been correlated with drug resistance and poor clinical outcome. YB-1 is a stress-responsive, cell cycle-regulated transcription factor with additional functions in RNA metabolism and translation. In this study, we show in a novel transgenic mouse model that human hemagglutinin-tagged YB-1 provokes remarkably diverse breast carcinomas through the induction of genetic instability that emerges from mitotic failure and centrosome amplification. The increase of centrosome numbers proceeds during breast cancer development and explanted tumor cell cultures show the phenotype of ongoing numerical chromosomal instability. These data illustrate a mechanism that might contribute to human breast cancer development.

The St. Gallen surrogate classification for breast cancer subtypes successfully predicts tumor presenting features, nodal involvement, recurrence patterns and disease free survival.

AIMS: To evaluate how the St. Gallen intrinsic subtype classification for breast cancer surrogates predicts disease features, recurrence patterns and disease free survival. MATERIALS AND METHODS: Subtypes were classified by immunohistochemical staining according to St. Gallen subtypes classification in a 5-tyre system: luminal A, luminal B HER2-neu negative, luminal B HER2-neu positive, HER2-neu non luminal or basal-like. Data were obtained from the records of patients with invasive breast cancer treated at our institution. Recurrence data and site of first recurrence were recorded. The chi(2) test, analysis of variance, and multivariate logistic regression analysis were used to determine associations between surrogates and clinicopathologic variables. RESULTS: A total of 2.984 tumors were classifiable into surrogate subtypes. Significant differences in age, tumor size, nodal involvement, nuclear grade, multicentric/multifocal disease (MF/MC), lymphovascular invasion, and extensive intraductal component (EIC) were observed among surrogates (p < 0.0001). After adjusting for confounding factors surrogates remained predictive of nodal involvement (luminal B HER2-neu pos. OR = 1.49 p = 0.009, non-luminal HER2-neu pos. OR = 1.61 p = 0.015 and basal-like OR = 0.60, p = 0.002) while HER2-neu positivity remained predictive of EIC (OR = 3.10, p < 0.0001) and MF/MC (OR = 1.45, p = 0.02). Recurrence rates differed among the surrogates and were time-dependent (p = 0.001) and site-specific (p < 0.0001). CONCLUSION: The St. Gallen 5-tyre surrogate classification for breast cancer subtypes accurately predicts breast cancer presenting features (with emphasis on prediction of nodal involvement), recurrence patterns and disease free survival.

YB-1 as a cell cycle-regulated transcription factor facilitating cyclin A and cyclin B1 gene expression.

Expression of the Y-box protein YB-1 is increased in proliferating normal and cancer cells, but its role in cell proliferation and cell cycle progression is unclear. We have identified a cell cycle-dependent relocalization of YB-1 from the cytoplasm to the nucleus at the G1/S phase transition and demonstrate that both the charged zipper and the cold shock domain are involved in regulating this process. Using cell lines that constitutively overexpress YB-1, we show that nuclear accumulation of YB-1 is associated with increased cyclin A and cyclin B1 mRNA and protein expression. We provide evidence that deregulated YB-1 expression is linked to adhesion-independent cell proliferation through the induction of cyclin A. Thus, we have identified YB-1 as a cell cycle stage-specific transcription factor important for cell proliferation.