RCAS1, also known as EBAG9, is a tumor-associated antigen that is expressed at high frequency in a variety of cancers. RCAS1 gene was identified as an estrogen-responsive gene. Regulation of transcription by estrogen is mediated by estrogen receptor which binds to the estrogen-responsive element (ERE) found in the 5'-flanking region of RCAS1 gene. Two transcript variants differing in the 5' UTR, but encoding the same protein, have been identified for RCAS1 gene. EBAG9 may participate in suppression of cell proliferation and induces apoptotic cell death through activation of interleukin-1-beta converting enzyme (ICE)-like proteases.