The overall goal of this protocol is to enable clinical support staff in a dermatology practice to effectively process and store cutaneous tumor samples for downstream laboratory applications, without interfering with routine clinical operations. This protocol was designed to enable medical assistants and Mohs histotechnicians to collect and store cutaneous tumor samples for future biomedical research projects, as part of their daily clinical operations. The main advantage of this protocol is that excised tissues that are normally discarded and destroyed are instead collected and preserved for research, using procedures, which minimally impact routine clinical operations.
The variety of samples collected enables correlations between protein and RNA biomarkers in the tissue and plasma samples with patient outcome data. In principle, this protocol, once slightly modified is applicable to any surgical practice, that routinely discards patient samples, gathered in the course of patient treatment. Demonstrating the procedure will be Stefani Fawks, a Mohs histotechnician, and Dr.Mitchell Manway, a research fellow in our practice.
To begin, use the tissue received from the Mohs surgeon and with a scalpel, excise a 10 to 50 milligram sample from the center of the apical side of the tissue. With tweezers, transfer the viable tissue to a labeled 1.5 milliliter tube, prefilled with culture medium. Make sure the tissue is entirely immersed in the medium.
Place the sample in a refrigerator and store it at four degrees Celsius, for no longer than 24 hours before further processing. Harvest at least a 10 cubic millimeter tissue fragment from the apical side of the excised tissue, when the tumor sample is large enough, and such removal will not interfere with routine Mohs processing. Next, place the remaining unprocessed tumor sample on a cryostat tissue holder.
Embed the tissue in an optimal cutting temperature compound, and freeze it within the holder to prepare histological slides. Using a cryostat, cut the tissue into seven micron thick sections, and layer up to three sections over a slide. After sectioning, fix the tissue by immersing the slides in acetone for one to two seconds.
Then, allow the slides to air dry. Keeping the remaining sample in a cryostat chamber, pry the tissue from the cryo embedding medium, and transfer it to a labeled cryogenic tube. Immediately transfer the labeled vial into liquid nitrogen.
Transfer of the tissue to a cryo vial after Mohs processing must be performed in the negative 20 degrees Celsius cryostat chamber. If performed properly and the tissue is kept frozen, this step will enable the successful extraction of RNA from post-Mohs tissue samples. Next, obtain adjacent normal tissue from the Mohs surgeon.
Excise a sample from the apical side of the adjacent normal tissue. Then, using tweezers, transfer the excised sample to a labeled 1.5 milliliter tube filled with culture medium. Immerse the tissue in the same culture medium.
Place it into an appropriate sample bag, and store at four degrees Celsius, until subsequent processing. Collect approximately 10 milliliters of venous blood into EDTA-coated collection tubes. Combine the blood samples in a sterile 15 milliliter centrifuge tube.
Then, transfer approximately one milliliter of the blood sample into a 1.5 milliliter cryogenic tube, avoiding bubbles. Store this whole blood sample at minus 80 degrees Celsius, until subsequent genotyping and tissue matching. Next, centrifuge the remaining blood sample at 1000 times G for 30 minutes to obtain blood plasma.
After spinning, collect and divide the plasma until one milliliter aliquots in 1.5 milliliter cryogenic tubes. And store the samples at minus 80 degrees Celsius for use during future liquid biopsy analyses. Enter the data from the checklist of patient samples, along with patient information and diagnosis, subtracted from the patient chart to the biorepository database.
Finally, record the localization of the de-identified samples in the biorepository database, and move the samples to the research lab. Immediately after, transfer the tissue samples into 1.5 milliliter tubes, prefilled with appropriate extraction solutions, making sure the tissue is completely immersed. Store the samples at minus 80 degrees Celsius until further processing.
Presented here are the images of representative Western blots of known squamous cell carcinoma markers, mucin one, FHL-one, and p40, obtained for adjacent normal tissue and a tumor sample. The quality of the RNA isolated from Mohs samples was first assessed using gel electrophoresis, followed by RNA integrity analysis. RNA integrity number values achieved for normal and tumor samples indicate that high quality and intact RNA was obtained.
Cytometry profiles of the bands were plotted as fluorescence units versus nucleotide number for representative RNA samples from tumor and normal patient tissue. A squamous cell carcinoma tissue explant was imaged using phase contrast microscopy and shown to be a mixed keratinocyte and fibroblast culture, that might be subcultured or used for future cell line development. Finally, in the squamous cell carcinoma tissue sections, positive staining for the epithelial to mesenchymal transition marker was shown.
Once mastered, this protocol will extend the standard work flow of the clinic staff to less than 30 minutes, if it is performed properly. The majority of the steps are performed by the existing clinical staff after patient care is completed. While attempting this protocol, it is important to maintain accurate record keeping, linking the samples with the patient's history and diagnosis.
As this information is often needed for downstream applications. This technique will help pave the way for researchers in the field of dermatology for the development of liquid biopsies and biomarkers in squamous cell carcinomas and melanoma. After watching this video, you should have a good understanding of how to implement a clinic-based biorepository for cutaneous cancer samples, generated as part of daily practice.
