Transcription profiling of human breat cancer cell lines reveals XBP1 confers estrogen independence and antiestrogen resistance

ABSTRACT: Human X-box binding protein-1 (XBP1) is an alternatively spliced transcription factor that participates in the unfolded protein response (UPR), a stress signaling pathway that allows cells to survive the accumulation of unfolded proteins in the endoplasmic reticulum lumen. We have previously demonstrated that XBP1 expression is increased in antiestrogen-resistant breast cancer cell lines, and is co-expressed with estrogen receptor alpha (ER) in breast tumors. The purpose of this study is to investigate the role of XBP1 and the UPR in estrogen and antiestrogen responsiveness in breast cancer. Overexpression of spliced XBP1 (XBP1(S)) in ER-positive breast cancer cells leads to estrogen-independent growth and reduced sensitivity to growth inhibition induced by the antiestrogens Tamoxifen and Faslodex in a manner independent of functional p53. Data from gene expression microarray analyses imply that XBP1(S) acts through regulating the expression of ER, the anti-apoptotic gene BCL2, and several other genes associated with control of the cell cycle and apoptosis. Experiment Overall Design: Total RNA was isolated from six independent cultures (cell populations grown on different days from different stocks); three from MCF7/XBP1 cultures and three from the vector control cultures. MIAME 1.1 compliant data were collected as recommended by the Microarray Gene Expression Data (MGED) Society. RNA concentrations were determined by comparing the optical density ratios (260:280 nm) , and data on RNA quality was obtained using an Agilent 2100 Bioanalyzer and RNA 6000 LabChip kits (Agilent Technologies, New Castle, DE). RNA quality was assessed by visual inspection of the electropherograms from the Bioanalyzer data, and by the calculated RNA integrity numbers (RIN) and Degradometer values . Only high quality total RNA was labeled and hybridized to U133A Affymetrix GeneChips using manufacturer recommended procedures (Affymetrix, Santa Clara, CA). Standard “spiked-in” controls also were included in each hybridization.

ORGANISM(S): Homo sapiens

SUBMITTER: Gomez BP 

PROVIDER: S-ECPF-GEOD-8562 | biostudies-other | 2007 Dec

REPOSITORIES: biostudies-other