The clinical and cytogenetic significance of C-banding on chromosome #9 in patients with Ph1-positive chronic myeloid leukemia.

The C-band polymorphism of chromosome #9 in 18 patients with chronic myeloid leukemia (CML) with a Philadelphia chromosome (Ph1) translocation between chromosomes #9 and #22 was examined using C- and Q-banding techniques on the same metaphases and the classification proposed by Patil and Lubs [1]. The C-band polymorphism of chromosome #9 in CML was found not to differ in leukemic cells with the Ph1 and phytohemagglutinin-stimulated lymphocytes without the Ph1 and to have a clonal origin, i.e., to arise from a single cell in which the Ph1 translocation has taken place. A comparison of the C-band polymorphism of chromosome #9, survival after diagnosis of the disease, and abnormal chromosomes in addition to the Ph1 indicates some interesting aspects. Patients with the smallest C-band (level 1) on chromosome #9 not involved in the Ph1 translocation and with a relatively large C-band (level 2) on chromosome #9 with the Ph1 translocation (C9-1,2) tend to have no clonal evolution and short survival after diagnosis of the disease. On the other hand, patients with other types of C-band patterns tend to have evidence of clonal evolution and long survival. This study suggests that the C-banding pattern in Ph1-positive CML might be utilized as a prognostic parameter in the disease and that the C-segment might have biological activity.