A long distance-PCR derived FISH probe detects a deletion between p15 and p16 in CML and T-ALL patients

The tumor suppressor genes p15(INK4B) and p16(INK4A), located in the chromo somal region 9p21, are frequently inactivated by homo- or hemizygous deleti ons, point mutation or promotor methylation in various types of cancer. No commercial probe is yet available that allows the detection of such deletio ns by FISH. Long distance (LD)-PCR was successfully used to generate a FISH probe, that covers a sequence stretch of 11.68 kb, located between the tum or suppressor genes p15 and p16. The LD-PCR amplicon was cloned and biotiny lated by DOP-PCR (degenerated oligonucleotide primed-PCR) or nick translati on. The FISH probe was hybridized on different samples of 16 patients with leukemia (3 T-ALL, 13 CML) and normal controls. Loss of at least one FISH-s ignal was found in 2/3 (67%) of the T-ALL-and 2/13 (15%) of the CML-cases. The new FISH probe presented here was proven to be advantageous for the det ection of deletions in chromosomal region 9p21, especially between p15 and p16.