Identification of RAI3 as a therapeutic target for breast cancer

We have been investigating gene-expression profiles in estrogen receptor (ER)-negative breast cancers to identify molecules involved in breast carcinogenesis and to select genes or gene products that might be useful as diagnostic markers or targets for new molecular therapies. Here we report evidence that the gene encoding retinoic acid-induced protein 3 (RA13) is a potential molecular target for treatment of breast cancers. Using quantitative reverse transcription-PC R (RTPCR), we documented increased expression of RA13 in 19 of 25 primary breast cancers and in 6 of 11 breast-cancer cell lines examined, by comparison with normal mammary-gland tissue. Treatment of human embryonic kidney (HEK293) cells with siRNA against RA13 suppressed expression of RA13 and also suppressed cell growth. Transfection of siRNA into breast-cancer cell lines MCF7 and T47D also suppressed RA13 mRNA and growth of the cancer cells. Because our data imply that up-regulation of RA13 function is a frequent feature of breast carcinogenesis, we suggest that selective suppression of signal from RA13 might hold promise for development of a new strategy for treating breast cancers.