Detection and quantitation of low numbers of chromosomes containing bcl-2 oncogene translocations using semi-nested PCR

A PCR assay has been optimized for the detection of one or a few molecules of a translocation-containing human DNA sequence in the presence of a vast excess (7 micrograms) of the normal human genome. This procedure avoids blot hybridization by the use of two rounds of PCR with 20-22 cycles of amplification per round and by the replacement of one of the two primers from the first round of PCR with a different primer in the second round (semi-nested PCR). We demonstrate that very low numbers of the target DNA molecules can be quantitated by this semi-nested PCR. This method can be used to detect a single DNA molecule from one mutant cell displaying a translocation between the bcl-2 proto-oncogene region and a JH immunoglobulin gene sequence [t(14;18)] in a background of normal human DNA from 10(6) cells.