“…Label free LC-MS approaches have been used to study several cancers like head and neck squamous cell carcinomas (Baker et al, 2005), esophageal cancer (Hatakeyama et al, 2006), dysplasic cervical cells TISSUE PROTEOMICS 5 (Gu et al, 2007), breast carcinoma tumors (Hill et al, 2011;Johann et al, 2009), tamoxifen-resistant breast cancer cells (Umar et al, 2009), ER + / -breast cancer cells (Rezaul et al, 2010), Barretts esophagus (Stingl et al, 2011), and ovarian endometrioid cancer (Alkhas et al, 2011). Different isotope labeling methods have been used in order to compare proteins expression.…”