REVIEW Emerging applications of fluorescent nanocrystals quantum dots for micrometastases detection Wael Mahmoud 1 , Alyona Sukhanova 1,4 , Vladimir Oleinikov 2 , Yury P. Rakovich 3 , John F. Donegan 3 , Michel Pluot 1 , Jacques H. M. Cohen 1 , Yuri Volkov 3 and Igor Nabiev 1,4,5 1 EA n13798 De ´ tection et Approches The ´ rapeutiques Nanotechnologiques dans les Me ´ canismes Biologiques de De ´ fense, Universite ´ de Reims Champagne-Ardenne, Reims, France 2 Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russian Federation 3 Trinity College Dublin and CRANN, Dublin, Ireland 4 CIC nanoGUNE Consolider Research Centre, Tolosa Hiribidea, Donostia–San Sebastian, Spain 5 IKERBASQUE, Basque Foundation for Science, Bilbao, Spain Received: August 1, 2009 Accepted: September 24, 2009 The occurrence of metastases is one of the main causes of death in many cancers and the main cause of death for breast cancer patients. Micrometastases of disseminated tumour cells and circulating tumour cells are present in more than 30% of breast cancer patients without any clinical or even histopathological signs of metastasis. Low abundance of these cell types in clinical diagnostic material dictates the necessity of their enrichment prior to reliable detection. Current micrometastases detection techniques are based on immunocytochemical and molecular methods suffering from low efficiency of tumour cells enrichment and observer-dependent interpretation. The use of highly fluorescent semiconductor nanocrystals, also known as ‘‘quantum dots’’ and nanocrystal-encoded microbeads tagged with a wide panel of antibodies against specific tumour markers offers unique possibilities for ultra- sensitive micrometastases detection in patients’ serum and tissues. The nanoparticle-based diagnostics provides an opportunity for highly sensitive parallel quantification of specific proteins in a rapid and low-cost method, thereby providing a link between the primary tumour and the micrometastases for early diagnosis. Keywords: Antibody / Breast cancer / Micrometastases / Multiplexing / Nanoproteomics / Quantum dot 1 Introduction Prognostic information about solid cancers is based, in clinical practice, on the analysis of pathological staging: tumour size and type, lymphatic and vascular depth of invasion, auxiliary lymph node involvement and steroid receptor status [1]. This approach does not allow prediction of metastatic relapse after a locoregional treatment. The main cause of this problem is the presence of overall rare disseminated tumour cells and circulating tumour cells (CTC), also termed micrometastases (MMs), which are the intermediate pathogenetic link between the primary tumour and metastases in all solid cancers. More than 30% of breast cancer patients without clinical or even histo- pathological signs of metastasis have MMs [2]. The occur- rence of distant metastases is the main cause of death for breast cancer patients. The variation of MMs occurrence during treatment of metastatic breast cancers was identified as a strong predictive indicator for evaluation of clinical response in these patients [3, 4]. There is increasing evidence, that the detection of MMs may provide additional Abbreviations: Ab, antibody; CK, cytokeratin; CTC, circulating tumour cells; EpCAM, epithelial cell–cell adhesion molecule; FISH, fluorescence in situ hybridization; HER2, human epidermal growth factor receptor 2; MM, micrometastases; MUC1, mucin 1; QD, quantum dot Correspondence: Professor Igor Nabiev, Laboratory of Nano- biotechnology, CIC nanoGUNE Consolider Research Centre, Tolosa Hiribidea 76, 20018 Donostia–San Sebastian, Spain E-mail: i.nabiev@nanogune.eu Fax: +34-943-574-001 & 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.proteomics-journal.com 700 Proteomics 2010, 10, 700–716 DOI 10.1002/pmic.200900540