PGR and breast cancer: A similar demonstration of this graduation strategy by Lee et al. employed MNPs conjugated to anti-HER2 antibodies to target breast cancer cells; once captured from culture media (capture efficiency >99%), CTCs were sorted based on a magnetic gradient into ‘HER2 positive’ and ‘HER2 negative’ regions (Fig. 5A), allowing near instantaneous grading and readout of CTC phenotype based on the expression of the oestrogen receptor (OR) and progesterone receptor (PR).