142 Chapter 5 oropharyngeal squamous cell carcinoma or differs between these cancers’ center and periphery (variable staining) (17). It was also shown that MET ECD shedding occurs in OSCC (18). Both C-terminal MET uniform staining and ECD shedding were found to be associated with poor patient prognosis (17, 18). Seen the potential diagnostic value of these findings, the goal of this study is to investigate the feasibility of extrapolating the TMA results to whole-tissue sections (WTSs). Therefore, a novel scoring system was developed that addresses tumor heterogeneity by discriminating between immunoreactivities observed in the center and periphery of cancer fields. It was also examined if the scoring system is informative with respect to biological processes such as MET ECD shedding and EMT and whether it is prognostically informative. Materials and Methods Ethics statement Human tissues and patient data were used as per The Code of Conduct for Responsible Use and The Code of Conduct for the Used of Data in Health Research as stated by the Federation of Dutch Medical Scientific Societies (19). Patient tissues Formalin-fixed paraffin-embedded tissue blocks representative for 203 primary OSCCs – surgically removed between 1984 and 2010 – were retrieved from the tissue bank of the department of Pathology of the Leiden University Medical Center. Histopathological characteristics were retrieved from the pathology reports and annotated as per the 7th Edition of the Cancer Staging Manual (20). Using a microtome, 3 mm thick WTSs were cut in view of immunohistochemical analyses. Antibodies and immunohistochemistry D1C2 (Cell Signaling Technology®; Danvers, MA, USA) detected C-terminal MET as described in the study by De Herdt et al. (17). A2H2-3 (Eli Lilly and Company; Indianapolis, USA) detected N-terminal MET as described in the study by De Herdt et al. (18). Endothelial cells lining veins were used as internal positive controls (18). NCH-38 detected E-cadherin (1:50; Agilent Dako Products; Amstelveen, Noord-Holland, The Netherlands) using essentially the same protocol described for D1C2 (17). Differences were as follows: antigen retrieval under 0.9 bar and secondary antibody E0413 (1:150; Agilent Dako Products). Squamous epithelium adjacent to the cancer was used as an internal positive control. Two observers (M.J.D.H. and B.v.d.S.) pre-
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