Upregulation and overexpression of human X-box binding protein 1 (hXBP-1) gene in primary breast cancers.
BACKGROUND
Human X-box binding protein 1 (hXBP-1) is a transcription factor essential for hepatocyte growth as well as for plasma cell differentiation. hXBP-1 also binds to cis-elements of human T cell leukemia virus and human major histocompatibility complex genes. In order to clarify the role of XBP-1 in breast cancer, here we investigated the expression of XBP-1 in 11 primary breast cancers and 5 breast cancer cell lines.


METHODS
The study population consisted of eleven patients who were underwent surgery for breast cancer from 2000 to 2002. Five breast cancer cell lines (MDA-MB-453, CRL1500, YMB-1-E, MCF7 and HBL100) were analyzed for XBP-1 expression. Reverse transcription polymerase chain reaction was performed on 6 primary breast cancers. Then we investigated XBP-1 expression by immunohistochemically on archived paraffin-embedded sections.


RESULTS
hXBP-1 mRNA expression was increased in all 11 primary breast cancers we examined, as well as 5 breast cancer cell lines, but hardly detectable in non-cancerous breast tissue. Immunohistochemical staining demonstrated that hXBP-1 protein stained strongly in the cytoplasm of cancer cells but was unreactive in the normal breast ductal epithelial and myoepithelial cells.


CONCLUSIONS
These data indicate that increased expression of the hXBP-1 gene may play some role in human breast carcinogenesis through impairment of cell differentiation regulation.
Fujimoto
Takashi
T
Department of Molecular Biology, Institute of Gerontology, Nippon Medical School, 1-396, Kosugi-cho, Nakahara-ku, Kawasaki 211-8533, Japan.
Onda
Masamitsu
M
Nagai
Hisaki
H
Nagahata
Takemitsu
T
Ogawa
Kenji
K
Emi
Mitsuru
M
D000368:Aged; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D044584:Carcinoma, Ductal / Q000235:genetics* / Q000473:pathology*; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D004273:DNA, Neoplasm / Q000032:analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D004721:Endoplasmic Reticulum; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D000071701:Regulatory Factor X Transcription Factors; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics*; D015854:Up-Regulation; D000071717:X-Box Binding Protein 1
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human