LOW-FREQUENCY OF C-KIT EXPRESSION AND DETECTION OF AN ABERRANT KIT MESSAGE AMONG HONG-KONG CHINESE MYELOGENOUS LEUKEMIA PATIENTS

The c-kit proto-oncogene encodes a transmembrane tyrosine kinase recep tor. It is expressed by the primitive CD34 positive haemopoietic stem cells and interacts with the Kit ligand for signal transduction. It wa s reported to be expressed in over 80% of acute myelogenous leukaemia (AML) patients in North America and Japan. We analyzed 20 AML patients for c-kit expression using either Northern blot analysis or flow cyto metry with the YB5.B8 anti-c-kit antibodies. Only 6 out of 20 AML pati ents expressed the c-kit mRNA or protein product. However, a previousl y unreported abnormal sized 1.7-1.9 kb transcript was detected in the blast cells of 1 AML patient, 1 acute mixed lineage leukaemia patient and 1 chronic myelogenous leukaemia (CML) patient in myeloblastic tran sformation. Our data suggested that in most Hong Kong Chinese AML pati ents, leukaemia transformation may have occurred at a c-kit negative s tage. Alternatively, the abnormal sized c-kit transcript that was dete cted in some Chinese myeloid leukaemia patients may represent an aberr ant c-kit receptor that plays an important role in leukaemogenesis. (C ) 1997 Elsevier Science Ireland Ltd.