Qualitative PCR analyses of cellular DNA obtained from various tissues by microdissection. Cellular DNA used as a template in these PCR reactions was obtained from microdissected cells as described in “Materials and methods,” and PCR products resolved electrophoretically in 1.2% agarose gels. Cellular DNA from mouse gastric and lung cells were processed in an identical manner to exclude the possibility that the human-specific primer pair cross-reacted with mouse DNA.