LACK OF CORRELATION BETWEEN ABL-BCR EXPRESSION AND RESPONSE TO INTERFERON-ALPHA IN CHRONIC MYELOID-LEUKEMIA

Interferon-alpha (IFN-alpha) is useful in the treatment of Philadelphi a (Ph)-positive chronic myeloid leukaemia (CML). There is, however, a marl;ed heterogeneity among CML patients in relation to their response to IFN-alpha treatment, the reasons for which are unknown, Since the reciprocal ABL-BCR gene is transcriptionally active in only a proporti on of Chit patients, it has been suggested that response to IFN-alpha may correlate with ABL-BCR expression. In the present study we have te sted 209 Ph-positive CML patients for expression of ABL-BCR, BCR-ABL a nd the normal BCR and ABL genes by reverse transcriptase/polymerase ch ain reaction (RT/PCR). Whereas BCR-ABL, BCR and ABL transcripts were d etected in all the patients, ABL-BCR expression was observed in 59% of the cases. A group of 105 patients within this series was treated wit h IFN-alpha: 33% achieved a complete or major cytogenetic response (< 35% Ph-positive metaphases) and the remaining 67% showed minimal or no response to IFN-alpha. The proportions of patients who were ABL-BCR p ositive (63%) and ABL-BCR negative (37%) were the same for good respon ders and poor responders, suggesting that there is no correlation betw een ABL-BCR expression and cytogenetic response to IFN-alpha in CML.