Abstract #5414: Epithelial mesenchymal transition (EMT) is involved in bone marrow dissemination of breast cancer cells

Abstract

Background: Disseminated tumour cells (DTC) in the bone marrow are regarded as a surrogate for minimal residual disease in breast cancer. Epithelial-mesenchymal transition (EMT) is a process that is supposed to facilitate tumor dissemination. The aim of this study was to determine the expression of EMT genes in DTC isolated from breast cancer patients. Methods: Bone marrow (BM) aspirations obtained from 32 primary breast cancer patients between August and October 2008 are included in this study. Eighteen patients received neoadjuvant chemotherapy. BM aspirates were reacted with anti-CD326 coated immunomagnetic beads and separated into CD326-enriched (CD326⁺) and CD326-depleted (CD326^-) fractions using the AutoMACS cell separator. Expression levels of gene transcripts for TWIST1, SNAIL1 and SLUG in the CD326⁺ fraction were compared with those of CD326^- fractions using quantitative reverse transcription-PCR. The expression profiles of genes from CD326⁺ fraction relative to CD326^- fraction were correlated with tumor characteristics of the patients. Expression of oestrogen and progesterone receptors, HER2, Notch-1, and Numb were evaluated in CD326⁺ cells as well. Results: The median age of the patients at the time of BM aspirations was 51 years (range; 28-76 years). Mean expression ± SEM of TWIST1, SNAIL1 and SLUG in CD326⁺ fractions relative to those of the CD326^- fractions were 28.4 ± 27.4; 136.3 ± 68.4 and 116.2 ± 111.5, respectively. At least two-fold increases in expression of TWIST1, SNAIL1 and SLUG in CD326⁺ fractions were detected in 10%, 48% and 19% of patients, respectively. There was a correlation between TWIST1 expression and high grade of tumor, preferentially in patients treated by neoadjuvant chemotherapy (Spearman\#8217;s correlation r = 0.99, p<0.0001), while expression of all three genes correlated with ER expression in CD326⁺ fraction (Spearman\#8217;s correlation r = 0.4, p < 0.05). Conclusions: The EMT associated genes are often overexpressed in DTC and are probably associated with tumor biology. Functional characterization of these genes in DTCs could help better understand the known limitations of neoadjuvant and adjuvant therapies.

Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 5414.