Formalin-fixed, paraffin-embedded FFPE tissue sections

In 1991 Shi et al. published their seminal observation that high-temperature incubation of formalin-fixed, paraffin-embedded (FFPE) tissue sections in buffers for short periods led to improved immunohistochemical staining.1 However, more than 15 years later, heat-induced antigen retrieval (AR) remains largely an empirical procedure, requiring the optimization of several critical parameters by trial and error.2,3 Further improvements in AR will require an in-depth understanding of the chemistry of formaldehyde fixation and the molecular mechanism(s) underlying the AR method. 

As documented by numerous publications, the key factor of heat-induced AR is high temperature heating formalin-fixed, paraffin-embedded (FFPE) tissue sections in water solution. For some antigens, certain optimized pH value of the AR solution and/or adjusted temperature may be required to reach the best result by the use of the test battery approach mentioned above. In 2005, Namimatsu et al. reported a novel AR solution containing 0.05% citraconic anhydride, pH 7.4, for heating FFPE tissue sections at 98°C for 45 min to... 

Compound (Miles Laboratories, Elkhart, IN), snap-frozen, and cut into sections for comparison with paraffin-embedded cell sections (3) FFPE Cell Blocks Six cell pellets were fixed in 10% neutral buffered formalin immediately after harvest, at room temperature for 6,12,24h, 3,7, and 30 days, respectively. For further comparison with the cell model system, recently collected sample of human breast cancer tissues were processed by OCT-embedding and snap-freezing the corresponding routine FFPE block that was obtained from the Norris Cancer Hospital and Research Institute at the University of Southern California Keck School of Medicine (USC). This tissue block was processed routinely (formalin-fixed 24h and processed by automatic equipment). 

---