Epithelial to Mesenchymal Transition in CTCs from breast cancer patients: MGH paper published in Science

Circulating tumor cells get wanderlust

Science 1 February 2013: 
Vol. 339 no. 6119 pp. 580-584DOI:10.1126/science.1228522
Key highlights of the paper:

• Both mesenchymal & epithelial markers were expressed  in rare primary tumor cells but mesenchymal cells were highly enriched in CTCs. 
• An association of mesenchymal CTCs with disease progression was observed by serial monitoring of 11 patients
• Reversible shifts between these epithelial & mesenchymal cell fates accompanied each cycle of response to therapy and disease progression in an index patient
• Provides evidence of EMT in human breast cancer specimens, both in rare cells within primary tumors and more abundantly in CTCs. 
• The researchers found a striking association between expression of mesenchymal markers and clusters of CTCs, rather than single migratory cells.
• The proposal that mesenchymal transformation of epithelial cells is mediated by TGF-β released from platelets is supported by the researchers who note of strong TGF-β signatures in mesenchymal CTC clusters, many of which carry attached platelets
• human primary breast tumors contain rare cancer cells that coexpress mesenchymal and epithelial markers

Methods used:
Herringbone chip using an antibody cocktail (EpCAM, EGFR and Her2). Dual-colorimetric RNA–in situ hybridization (ISH) assay was used to examine tumor cells for expression of  epithelial (E) transcripts: [keratins (KRT) 5, 7, 8, 18, and 19; EpCAM (epithelial cell adhesion molecule); and CDH1 (cadherin 1)] and mesenchymal (M) transcripts: [FN1 (fibronectin 1), CDH2 (cadherin 2), and SERPINE1/PAI1 (serpin peptidase inhibitor, clade E)].

Focus review 2013: Label free microfluidic technologies for isolation of circulating tumor cells (CTCs)

Label-free isolation of circulating tumor cells in microfluidic devices: Current research and perspectives

This paper is quite comprehensive in covering the many label free approaches to CTC isolation reported so far, including, filters, accoustophoresis, magnetophoresis, etc.

The general recommendation of the paper is towards adoption of these technologies for clinical use.

undoubtedly, there are several advantages to label-free isolation of CTCs, specially filtration techniques, which are simple, inexpensive, fast and easy to use. However, there are some important limitations that need to be considered,  which I was hoping the paper would shed light upon, but didnt.

the general limitations of filtration techniques are listed here.

It was also recently reported that the deformability of tumor initiating cells is less differentiated from normal blood cells. This makes the sized and deformability based techniques vulnerable to missing these important subtypes of CTCs. This is covered here