OBJECTIVE We aimed identification of cell surface molecules,which might serve as diagnostic biomarkers or useful targets fortherapies, in breast cancer.METHODS We developed unique DNA microarray coupledwith spherical self-organizing map (sSOM) analysis to characterizecells and tissues by the cell surface markers. In the microarray 1,797probes for human genes coding membrane bound proteins werespotted. With this microarray the gene expression profiles of eightbreast carcinoma cell lines were compared to identify the genesthat were commonly expressed in breast carcinomas but not innormal cells.RESULTS The gene expression profiles of sSOM from the eightbreast carcinoma cell lines were successfully distinguished fromthat of normal breast tissue derived cells suggesting the presenceof genes of interest. sSOM on the data extensively filtered revealedseveral candidate genes, of which expression was significant incarcinoma cells but low in normal cells. Finally, TM9SF2 wasnominated through validations of PCR procedures together withCD24 and ErbB3, which are known breast carcinoma markers.TM9SF2 expression was further confirmed by immunologicalstaining. Interestingly, TM9SF2 was found to be expressed in allthe cell lines evaluated while CD24 and ErbB3 were not in allof the carcinoma cells, supporting their relationship in sSOM.Although physiological significance of TM9SF2 is unknown yet,siRNA treatment significantly inhibited the growth of MDA-MB-231 cells.CONCLUSION We propose TM9SF2 as a novel and usefuldiagnostic marker as well as a potential molecular target specificto breast carcinoma cells covering wide range of breast cancer.
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