identification of specific subtypes of circulating tumor cells in the peripheral blood of cancer patients can provide important prognostic information , but to be effective , the method used must recognize all tumor cell types . the subtype of 19 well - characterized breast cancer cell lines was obtained by use of gene expression profiling , including normal - like , basal - like , her2-positive , and luminal a and b. cells from each line were mixed with blood from a healthy donor and subjected to the cellsearch circulating tumor cell assay . the cellsearch assay , which uses epithelial cell adhesion molecules on the cell surface , did not recognize normal - like breast cancer cells , although other subtypes were recognized . normal - like breast cancer cells have especially aggressive features , and so assays that recognize this subtype would provide valuable prognostic information . new assays are needed that include antibodies that specifically recognize this breast cancer subtype but not other cell types , including those of hematopoietic origin . identification of specific subtypes of circulating tumor cells in the peripheral blood of cancer patients can provide important prognostic information , but to be effective , the method used must recognize all tumor cell types . the subtype of 19 well - characterized breast cancer cell lines was obtained by use of gene expression profiling , including normal - like , basal - like , her2-positive , and luminal a and b. cells from each line were mixed with blood from a healthy donor and subjected to the cellsearch circulating tumor cell assay . the cellsearch assay , which uses epithelial cell adhesion molecules on the cell surface , did not recognize normal - like breast cancer cells , although other subtypes were recognized . normal - like breast cancer cells have especially aggressive features , and so assays that recognize this subtype would provide valuable prognostic information . new assays are needed that include antibodies that specifically recognize this breast cancer subtype but not other cell types , including those of hematopoietic origin . this study was in part financially supported by the netherlands genomic initiative / netherlands organisation for scientific research .
identification of specific subtypes of circulating tumor cells in peripheral blood of cancer patients can provide information about the biology of metastasis and improve patient management . however , to be effective , the method used to identify circulating tumor cells must detect all tumor cell types . 
 we investigated whether the five subtypes of human breast cancer cells that have been defined by global gene expression profiling  normal - like , basal , her2-positive , and luminal a and b  were identified by cellsearch , a us food and drug administration  approved test that uses antibodies against the cell surface 
 expressed epithelial cell adhesion molecule ( epcam ) to isolate circulating tumor cells . 
 we used global gene expression profiling to determine the subtypes of a well - defined panel of 34 human breast cancer cell lines ( 15 luminal , nine normal - like , five basal - like , and five her2-positive ) . 
 we mixed 50 - 150 cells from 10 of these cell lines with 7.5 ml of blood from a single healthy human donor , and the mixtures were subjected to the cellsearch test to isolate the breast cancer cells . 
 we found that the cellsearch isolation method , which uses epcam on the surface of circulating tumor cells for cell isolation , did not recognize , in particular , normal - like breast cancer cells , which in general have aggressive features . 
 new tests that include antibodies that specifically recognize normal - like breast tumor cells but not cells of hematopoietic origin are needed .