ABSTRACT
By differential-display-PCR a subclone of the SK-BR-3 cell line with high in vitro transendothelial invasiveness was identified to express increased levels of a new alternative splice variant of decay-accelerating factor (DAF). DAF seems to play an important role in some malignant tumours since on the one hand the expression of complement inhibitors on the surface of tumour cells prevents the accumulation of complement factors and in consequence cell lysis. On the other hand, DAF has been identified as a ligand for the CD97 surface receptor which induces cell migration. Immunofluorescence procedures, Western blot analyses, and cDNA clone sequencing were employed to confirm the expression of DAF restricted to invasive tumour cells. Using a radioactive RNA-in situ hybridisation on freshly frozen tissue microarrays and RT-PCR on native tumour tissue, the expression of alternative spliced DAF mRNA was demonstrated in invasive breast cancer. Due to the fact that it could thereby not be detected in normal mammary tissues, it has to be confirmed in larger studies that the DAF splice variant might be a specific tumour marker for invasive breast cancer.
Subject(s)
Alternative Splicing , Breast Neoplasms/metabolism , CD55 Antigens/biosynthesis , CD55 Antigens/chemistry , Gene Expression Regulation, Neoplastic , Receptor, ErbB-2/biosynthesis , Antigens, CD , Base Sequence , Biomarkers, Tumor , Blotting, Western , Cell Movement , Cloning, Molecular , Complement Inactivator Proteins/chemistry , Complement System Proteins/metabolism , DNA, Complementary/metabolism , Electrophoresis, Agar Gel , Endothelium, Vascular/cytology , Gene Expression Profiling , Humans , Immunohistochemistry , In Situ Hybridization , Ligands , Membrane Glycoproteins/biosynthesis , Microscopy, Fluorescence , Molecular Sequence Data , Neoplasm Invasiveness , Oligonucleotide Array Sequence Analysis , Polymerase Chain Reaction , RNA/metabolism , RNA, Messenger/metabolism , Receptor, ErbB-2/metabolism , Receptors, G-Protein-Coupled , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
By differential-display PCR a subclone of the SKBR3 cell line with high in vitro transendothelial invasiveness was identified to express increased levels of the INSL-4 gene. This new member of the insulin-like growth factor family encodes for a peptide, designated early placenta insulin-like (EPIL), being expressed in the so-called "invasive" phase of the placental development. Immunohistochemistry on tissue microarrays revealed a heterogeneous expression of EPIL in breast cancer tissue and no expression in the surrounding stroma cells. A coexpression of pro-EPIL and c-erbB-2 could be observed predominantly in cell clusters at the infiltrating edge of the tumor. Our results give new suggestions for the presence of a signaling network of receptor tyrosine kinases underlying breast cancer invasion and metastasis.
