IN-SITU POLYMERASE-CHAIN-REACTION - FOUNDATION OF THE TECHNOLOGY AND TODAYS OPTIONS

''In situ PCR'' is the marriage of two established technologies in mol ecular genetics, the polymerase chain reaction (PCR) and in situ hybri dization (ISH). It is based on the amplification within intact cells o r tissue sections of specific gene sequences, or mRNA species, to leve ls detectable by ISH and/or immunohistochemistry. Methods to achieve i n situ PCR, while sharing fundamental steps, have differed between dif ferent laboratories. On the basis of our own experience, in situ PCR a ppears to be best suited for the detection of DNA in single cell prepa rations, in which fixation and pre-treatments can be optimally control led. Emphasis is placed on the requirement for appropriate and meaning ful controls at the multiple steps involved. It is instructive to the view the emergence of this new technology in perspective. In situ PCR has not developed in isolation and is just one of several creative app roaches that have been employed in recent years to study nucleic acids (DNA and RNA) intracellularly. Some approaches are more suitable for detection of mRNA, or viral RNA, while others are more easily applied to chromosomal DNA. Some further techniques, such as the isothermal se lf-sustained sequence replication (3SR), refined in-situ transcription (PRINS), or high sensitivity histochemical detection systems, will co mplement or even add to the potential of situ PCR. It is highly probab le that tests will emerge, based on investigation of unique genetic ma rkers, with important roles in specialized diagnostic laboratories for the evaluation of viral diseases, as well as hematological and other malignancies.