Background: The management of breast cancer has been significantly advanced by the identification of specific protein profiles, to which specific therapies can be directed. Currently used technologies do not allow for the simultaneous quantification of multiple protein biomarkers on individual breast cancer sections.. We have developed an assay, by conjugating antibodies to semiconductor, multicolor nanoparticles, which allows the quantification of estrogen receptor (ER), progesterone receptor (PR) and HER2/neu on single breast cancer sections, and correlates well with Western blotting and immunohistochemistry (IHC). We have now expanded this assay to allow the detection and quantification of 5 breast cancer-related proteins in single sections of breast cancers and breast cancer cell lines. Methods: We directly conjugated multicolored QDs (525nm, 565nm, 605nm, 655nm, 705nm) to primary antibodies (QD-Abs) for ER, PR, HER2/neu, mTOR (mammalian target of rapamycin) and EGFR (epidermal growth factor receptor) respectively, and stained paraffin embedded sections of breast cancer cell lines (MCF-7, BT474, MDA-231) and human breast tumors. . Results: The use of QD-Abs allowed the detection of all 5 proteins simultaneously on single sections of breast cancer cell lines and breast tumors. Using hyper-spectral imaging and wavelength-resolved spectroscopy, we quantified the expression of each protein, detected using QD-Abs. Our results correlated well with standard methods of detection, including Western blotting. Conclusions: The use of QD-Abs allows the visualization and quantification of 5 clinically important biomarkers simultaneously in single breast cancer sections. The use of multiplex QDs offers the possibility of quantifying many more proteins in single tumor sections, allowing determination of an individual cancer’s proteome. These results raise new possibilities for nano technology applications in molecular pathology and clinical oncology, particularly in linking multiplexed cancer biomarkers with clinical outcome, and allowing the possibility of individualized therapy.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]