Circulating tumor cells (CTCs) and epithelial mesenchymal transition (EMT) in primary breast cancer.

Abstract

e22023 Background: CTCs are prognostic in breast cancer (BC) patients and represent a heterogeneous population of cells with different phenotypes and biological value. EMT gives rise to cells with stem cell-like properties with increased chemotherapy resistance and may be responsible for under detection of CTCs by currently approved assays. The aim of this study was to characterize CTCs based on the expression of epithelial and mesenchymal markers in non-metastatic BC patients. Methods: This prospective ongoing study included 124 patients (pts) with non-metastatic BC enrolled from March 2012 to December 2012. CTCs were detected before surgery (124 pts), before 1st cycle (28 pts) and before 2nd cycle (23 pts) of adjuvant therapy. Isolated peripheral blood mononuclear cells (PBMC) were depleted of hematopoietic cells using RossetteSep kit negative selection with anti-CD45 antibody. RNA extracted from CD45-depleted (CD45-) PBMC was interrogated for expression of EMT-inducing transcription factors (TWIST1, SNAIL1, SLUG, ZEB1) and epithelial (CK19) gene transcripts by qRT-PCR. Expressions of gene transcripts in CD45- PBMC of patients were compared to those of CD45- PBMC of 60 healthy donors. Results: CTCs were detected in 26.6% pts before surgery, in 21.4% pts before 1st cycle and in 43.5% of pts before 2nd cycle of adjuvant therapy. Before surgery, CTCs exhibiting only epithelial makers were present in 12.9% pts, whereas CTCs with only EMT markers were observed in 12.1% of pts and CTCs coepressing both markers were detected in 1.6% pts. There was a trend for higher CTC positivity in high grade, triple negative tumors and in the presence of lymphovascular invasion. We detected CTCs with only an EMT phenotype more often in pts with N+ than in N0 disease (20.4% vs. 10.2%; p = 0.03) and in pts after 1stcycle of adjuvant chemotherapy compared to before surgery (30.4% vs. 12.1%; p = 0.03). There was no association between epithelial CTCs and analyzed clinico-pathological variables. Conclusions: Our data suggest that CTCs with EMT phenotype are involved in tumor dissemination and treatment resistance, and support the role of EMT in cancer pathogenesis. Moreover, these results underlay the concept of CTCs heterogeneity.