Abstract 3380: Loss of immunorecognition of selected molecules during long-term storage of paraffin blocks

Introduction: Archival paraffin blocks frequently are touted as a resource for studies in translational research; however, there are few studies of the stability of immunorecognition in paraffin blocks after long term storage. Previously, we reported that immunorecognition of Bcl-2 and mutated p53 was stable in blocks stored for 10 years, but recent observations of decreases in immunorecognition of several molecules in paraffin blocks stored over 10 years necessitated additional studies. Because molecules in tumors are quite variable, it was decided that normal tissues not associated with disease processes as well as related cancers and uninvolved tissues should be studied. Methods: The immunorecognition of multiple molecules in fallopian tubes removed for fertility, in papillary serous adenocarcinomas (PSAC) and in uninvolved fallopian tubes associated with PSAC were evaluated. Multi-age (year) blocks from 2014 to 1976 were constructed and the following antigens were studied: smooth muscle actin (SMA, Thermo Fischer, MS-113-P, 1A4, 0.026 μg/mL, AR pH 9) in arteries; E-cadherin (E-CAD, Thermo Fischer, RM-2100-S, EP700Y, dilution 1:200, AR pH 9) in ciliated and separately secretory cells of relatively normal and uninvolved fallopian tubes and the cells of PSAC; vimentin (VIM, Thermo Fischer, RM-9120-S, SP20, dilution 1:500, AR pH 9), in endothelial cells; □-tubulin (GTUB, Santa Cruz Biotechnology, SC-17788, D-10, 0.028 μg/mL, AR pH 9) in ciliated cells of normal and uninvolved fallopian tubes, and cytokeratins, 18 (Cyk18, Epitomics, 1433-1, dilution 1:200, AR pH 9), and AE1/AE3 (Millipore, MAB3412, 4 μg/mL, AR pH 9) in ciliated and separately secretory cells of normal and uninvolved fallopian tubes. These molecules were stained in the multi-year blocks and were evaluated by a pathologist without knowledge of block age. Results: Consistently, in normal fallopian tubes, the antigens, SMA, VIM, GTUB and E-CAD, were relatively stable for at least 10 years, (i.e., < 20% decrease). In blocks from 1999, there were small decreases in the immunorecognition of SMA (11%) and a modest decrease in immunorecognition of VIM (18%); however, there were larger decreases in GTUB (34%) and in E-CAD (63% and 72%) in ciliated and secretory cells respectively. Decreases of all these antigens were even larger in blocks older than 1999. Evaluations of these antigens in PSACs and uninvolved fallopian tubes and of cytokeratins in the three tissues types are currently underway. Conclu