DNA PROBE ASSAY FOR THE PHILADELPHIA TRANSLOCATION

LEUKEMIC CELLS OF APPROXIMATELY 96 PERCENT OF PATIENTS WITH CHRONIC MYELOGENOUS LEUKEMIA (CML) AND 10 TO 25 PERCENT OF ACUTE LYMPHOCYTIC LEUKEMIA (ALL) PATIENTS ARE CHARACTERIZED BY A MARKER CHROMOSOME. THIS CHROMOSOME, DESIGNATED THE PHILADELPHIA (PH') CHROMOSOME, IS THE RESULT OF A RECIPROCALTRANSLOCATION BETWEEN CHROMOSOMES 9 AND 22; ITS PRESENCE HASIMPORTANT DIAGNOSTIC AND PROGNOSTIC IMPLICATIONS. A SPECIFIC REGION OF CHROMOSOME 22, 5.8 KB IN LENGTH, IS DESIGNATED THE BREAKPOINT CLUSTER REGION (BCR) AND HAS BEEN SHOWN TO ENCOMPASS PH' TRANSLOCATION BREAK-POINTS OF EACH OFA SERIES OF CML DNAS. USING A RELATIVELY COMPLEX SERIES OF THREE BCR-SPECIFIC PROBES, PH' POSITIVE LEUKEMIAS CAN BE IDENTIFIED BY GEL ELECTROPHORESIS AND SOUTHERN HYBRIDIZA- TION. THE RECENT DEMONSTRATION OF A BCR-SPECIFIC MRNA SPECIES OF AROUND 6.0KB INDICATES THAT BCR REPRESENTS A FUNCTIONAL GENE. IN PHASE I, RESEARCHERS WILL CHARACTERIZE A BCR-SPECIFIC CDNA CLONE. THIS INFORMATION SHOULD ENABLE THE ISOLATION OF A CDNA-SPECIFIC PROBE THAT WILL ENCOMPASS 2TO 3 EXONS 5' AND 2 TO 3 EXONS 3' OF THE PH' BREAKPOINT. THIS SINGLE, IMPROVED PROBE WOULD DETECT THE PH' TRANSLOCA- TION IN LEUKEMIC CELLS THAT CARRY THIS CHROMOSOMAL ABNORMALITY. USING THIS PROBE , A SERIES OF PH' POSITIVE LEUKEMIAS WILL BE ANALYZED FOR THE BCR BREAKPOINT. IN PHASEII, THE LEUKEMIC CELLS FROM AN EXPANDED SERIES OF PATIENTS WITH CLINICALLY DIAGNOSED CML AND ALL WILL BE ANALYZED. IN ADDITION TO THE BCR CDNA PROBE WILL BE FORMATTED INTO A NONISOTOPIC, SOLID-PHASE ASSAY TO PROVIDE A RAPID AND COST EFFECTIVE MEANS FOR THE DIAGNOSIS OF PH' POSITIVE LEUKEMIAS.