CHROMOSOMES AND CAUSATION OF HUMAN CANCER AND LEUKEMIA .37. NUCLEOLUS ORGANIZERS ON THE PH1-CHROMOSOME IN CHRONIC MYELOCYTIC-LEUKEMIA

In the light of reported evidence that Ag staining of nucleolar organizers (NOR) may reflect the transcriptionally active state of rDNA during the preceding interphase period, the present study addressed the question as to what kind of Ag-staining profiles are displayed by the secondary constrictions on Philadelphia (Ph1) chromosomes in chronic myelocytic leukemia (CML). The average number of Ag-stained NOR regions (Ag-NOR) in bone marrow cells was 5.10±0.89 per cell for CML patients and 4.84±0.30 per cell for controls, indicating that the active NOR in normal and CML bone marrow cells are equal in number. The distribution of Ag-NOR in the Ph1 chromosomes in CML was significantly lower (P < 0.005) than the expected value. There was no CML case where the Ph1 chromosome showed a higher incidence of Ag-NOR than expected. The results indicate that the NOR (or rDNA) on the Ph1 chromosomes may undergo transcriptionally inactive states. This phenomenon is further discussed in relation to other genetic mechanisms based on chromosome changes. © 1979.