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Epithelial cancer cells are likely to undergo epithelial-mesenchymal transition (EMT) prior to entering the peripheral circulation. By undergoing EMT, circulating tumor cells (CTCs) lose epithelial markers and may escape detection by conventional methods. Therefore, we conducted a pilot study to investigate mRNA transcripts of EMT-inducing transcription factors (TFs) in tumor cells from the peripheral blood (PB) of patients with primary breast cancer (PBC). PB mononuclear cells were isolated from 52 patients with stages I-III PBC and 30 healthy donors (HDs) and were sequentially depleted of EpCAM(+) cells and CD45(+) leukocytes, henceforth referred to as CD45(-). The expression levels of EMT-inducing TFs (TWIST1, SNAIL1, SLUG, ZEB1 and FOXC2) in the CD45(-) cells were determined using quantitative real-time polymerase chain reaction. The highest level of expression by the CD45(-) cell fraction of HD was used as "cutoff" to determine if samples from patients with PBC overexpressed any EMT-inducing TFs. In total, 15.4% of patients with PBC overexpressed at least one of the EMT-inducing TF transcripts. Overexpression of any EMT-inducing TF transcripts was more likely to be detected in patients with PBC who received neoadjuvant therapies (NAT) than patients who received no NAT (p = 0.003). Concurrently, CTCs were detected in 7 of 38 (18.4%) patients by CellSearch® and in 15 of 42 (35.7%) patients by AdnaTest™. There was no association between the presence of CTCs measured by CellSearch® or AdnaTest™. In summary, our results demonstrate that CTCs with EMT phenotype may occur in the peripheral circulation of patients with PBC and that NAT is unable to eliminate CTCs undergoing EMT.
Mego et al. (Tue,) studied this question.