REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION FOR BCR ABL FUSION INCHRONIC MYELOGENOUS LEUKEMIA/

Reverse transcriptase-polymerase chain reaction (RT-PCR) has shown pro mise as a means of detecting low levels of cells bearing the Philadelp hia chromosome (Ph1) and for detecting cytogenetically inapparent (''m asked'') Ph1 in patients with chronic myelogenous leukemia (CML). For detection by karyotyping, dividing cells must be used, precluding use of peripheral blood samples in cases with low peripheral blood blast c ounts. Reverse transcriptase-polymerase chain reaction was performed i n 83 bone marrow and 30 peripheral blood samples from patients with CM L to compare results with karyotyping and to evaluate utility of this test on peripheral blood samples. Using isolated total cellular RNA an d a single primer pair, cDNA was transcribed, amplified, electrophores ed, and probed for bcr/abl fusion involving M-bcr exons 2 and 3 of the bcr gene. Fifty-three samples were from untreated or conventionally t reated patients (pre-BMT), and 60 were from patients who had undergone bone marrow transplantation (post-BMT). Fifty of 53 pre-BMT samples w ere positive by RT-PCR. Two samples, negative by RT-PCR, had complex t ranslocations, t(9;16;22) and t(4;14;22). One case was indeterminate b y RT-PCR, but positive on retesting. Forty-five of 53 had Ph1 by karyo typing; 8 were negative, including 5 peripheral blood samples, 2 bone marrow samples with ''masked'' Ph1, and 1 bone marrow sample with poor growth. Thirty-five of 60 post-BMT samples were positive by RT-PCR. F ourteen of 60 post-BMT samples had Ph1 by karyotyping. Of the RT-PCR+/ Ph1-cases, most showed a weak but definite band by RT-PCR, suggesting a low level of the bcr/abl fusion gene. Nineteen patients had concurre nt peripheral blood and bone marrow samples analyzed by RT-PCR and kar yotyping. Of 16 patients with satisfactory RNA extraction, 15 had conc ordant results by RT-PCR. Five patients had adequate metaphase cells f or karyotypic analysis. All had Phl in bone marrow, but were negative in peripheral blood. Our results indicate that RT-PCR for detection of bcr/abl fusion is more sensitive than karyotyping in pre- and post-BM T samples. Furthermore, RT-PCR can be successfully performed on periph eral blood, yielding excellent correlation with bone marrow samples.