c-myc protein in normal tissue. Effects of fixation on its apparent subcellular distribution

The c-myc protein is thought to be a DNA-associated nuclear protein. However, immunohistochemical studies on normal or tumor tissues have shown conflicting findings on its subcellular distribution. By using various fixation procedures on cytospin preparations of HL60 cells, the authors found the subcellular distribution of the c-myc protein to be dependent on the method of fixation. When studying mouse tissues in frozen sections using a biotinylated monoclonal antibody against the c-myc protein, they found the protein to be widely distributed in various normal adult mouse tissues, in most cases localized to the nucleus. However, when these tissues were studied after formalin fixation and paraffin embedding, a loss of nuclear staining was observed concurrent with the appearance of c-myc protein immunoreactivity in the cytoplasm. It is concluded that immunohistochemical studies on the expression of this oncogene should take into consideration the effects of fixation when its subcellular distribution is being examined.