Representative examples of allelic loss at the 9p21 region. The presence of allelic loss in tumor (T) in comparison with matched normal (N) DNA is shown by arrows. Case BL16 showed HD in microsatellites IFN-α, D9S1749, and D9S1748 detected by multiplex PCR with the microsatellite marker D9S934; and LOH at the D9S171 marker. Case BL323 also showed HD at microsatellites D9S1749 and D9S1748. Case LB8 showed HD at the D9S1752 marker, but there was retention of both alleles in the other microsatellites studied, such as the marker shown here, ie, D9S1749. Case BL88 showed LOH at the D9S1749 locus.