Nonspecific In Situ Hybridization Reaction in Neuroendocrine Cells and Tumors of the Gastrointestinal Tract Using Oligonucleotide Probes

Oligonucleotides used in in situ hybridization (ISH). regardless of their sequence specificity, bind to neuroendocrine (NE) cells in normal gastrointestinal mucosa and tumors. This nonspecific binding, presumably related to the presence in NE cells of hidden NH2groups of obscure origin, can be prevented by acetic anhydride treatment of the sections. This is a routine step in several ISH protocols but not in all. This study emphasizes the need to establish safe protocols and controls to check the specificity of ISH procedures.