Abstract 3472: Mesodissection of slide mounted tissue: Applications including tumor tissue enrichment, expression analysis, and FISH on tissue fragments
Authors: Adey Nils , Emery Dale , Bosh Derek , Parry Robert 
Published: May 2015

Abstract
We previously reported the development of a mill based instrument for dissection of slide-mounted tissue sections. This instrument employs a specialized disposable mill bit that simultaneously dispenses liquid, cuts tissue from the slide surface using rotary motion, and aspirates the liquid along with the displaced tissue fragments. An accompanying software package is capable of transferring digital annotations between images of serially cut tissue sections to guide dissection and generate an electronic record of the process. Since the original report, a new instrument and software package has been developed with a computer controlled stage for automatic dissection of tissue. Here we report three applications using this mesodissection system. The first application investigated the relationship between dissection resolution and percent tumor tissue recovered. Areas of high tumor content were indicated on digital images of lung tumor samples. The areas of highest concentration were dissected at 400 micron resolution, the remaining areas of tumor dissected at 800 micron resolution, and then surrounding areas that would typically be recovered using manual macrodissection were dissected at 2 mm resolution. The percent mutant DNA, determined using the Sequenom OncoCarta panel, was greater than 60% for the 400 micron resolution dissections, about 45% for the 800 micron resolution dissections, and less than 10% for the remaining regions. The second application investigated the effect of various dissection related parameters on expression analysis, as assayed by Reverse Transcription and Quantitative PCR (RT-qPCR). These parameters included placing freshly microtomed FFPE tissue sections directly on slides vs. first floating on water, dissection of deparaffinized vs. paraffinized tissue, the use of crude lysates vs. purified RNA for the reverse transcription reactions, and manual dissection vs. mesodissection of the same areas on serial sections. RT-qPCR results were robust and equivalent for all parameters except those derived from crude lysates, which were equivalent to the no template controls. The third application investigated if mesodissected tissue fragments could be re-adhered to glass slides and used for FISH analysis. This application has the potential to automate and increase the throughput of FISH on tissue sections while reducing sample consumption. The preliminary results demonstrate that tissue fragments can produce good FISH signals, but a more detailed comparison to undissected tissue sections is ongoing. A significant concern is the loss of context of these fragments. This concern can be somewhat minimized by adjusting dissection conditions to obtain fragments larger than 1 mm in diameter and by mapping the dissected area onto the corresponding area a serial H&E stained tissue section using the mesodissection software.
Citation Format: Nils Adey, Dale Emery, Derek Bosh, Robert Parry. Mesodissection of slide mounted tissue: Applications including tumor tissue enrichment, expression analysis, and FISH on tissue fragments. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3472. doi:10.1158/1538-7445.AM2014-3472