(HealthDay News) – Gene expression of circulating tumor cells (CTCs), rare cells in the blood of patients with solid tumors, is heterogeneous and is distinct from the profiles of single cells from cancer cell lines commonly used to study cancer.

Ashley A. Powell, PhD, from the Stanford University School of Medicine in California, and colleagues used an immunomagnetic enrichment device that isolates live tumor cells from unfractionated blood, the MagSweeper, to purify CTCs. They examined the expression of 87 cancer-associated and reference genes in single CTCs from patients with primary and metastatic breast cancer.

The researchers found that gene expression was heterogeneous in the single CTCs. Based on 31 genes that were highly expressed, CTCs were divided into two major subgroups. In contrast, the single cells from seven breast cancer cell lines were tightly clustered, with expression profiles distinct from the CTCs.

“For the first time, we directly measured high dimensional gene expression in individual CTCs without the common practice of pooling such cells,” Powell and colleagues conclude. “Our findings demonstrate that profiling CTCs on a cell-by-cell basis is possible and may facilitate the application of ‘liquid biopsies’ to better model drug discovery.”

Several authors disclosed financial ties to the MagSweeper technology (licensed to Illumina, where one author is an employee). Another author is a co-founder of the Fluidigm Corporation, manufacturer of the chips used in the study.

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