A highly polymorphic CA repeat marker at the EBAG9/RCAS1 locus on 8q23 that detected frequent multiplication in breast cancer

Abstract

Background : Cloning of CpG binding sites in the human genome initially identified EBAG9 (estrogen receptor-binding fragment-associated gene 9), an estrogen-responsive gene mapped to chromosome 8q23. Its product was later found to be identical to RCAS1 (receptor-binding cancer antigen expressed on SiSo cells 1). RCAS1 was recently described as a cancer-surface antigen, implicated in immune escape in a human uterine adenocarcinoma cell line, which turned out to be identical to the EBAG9 molecule. Aim : The study seeks to isolate a highly polymorphic dinucleotide repeat at this locus that detects frequent multiplication of the EBAG9/RCAS1 gene. Subject and methods : A fragment containing CA repeat was identified by Southern blotting of bacterial artificial chromosome (BAC) clone containing the EBAG9/RCAS1 gene digested by Hae III, Sau 3A or Rsa I with (GT)20 probe, subcloned and sequenced. Results : We isolated a polymorphic dinucleotide (CA) repeat sequence from a genomic clone containing the EBAG9/RCAS1 gene located at 8q23. High heterozygosity (0.859) makes this polymorphism a useful marker in genetic studies. This marker detected frequent multiplication of the EBAG9/RCAS1 gene in primary breast cancers (27 of 129 tumours). Conclusion : This marker is useful for detecting frequent multiplication of the EBAG9/RCAS1 gene in primary breast cancers and other cancers.