Two different Philadelphia chromosomes in a cell line from an AML-M0 patient.
A second Philadelphia (Ph) chromosome is one of the most common nonrandom secondary chromosome changes in leukemias with 9;22 translocations. It has been suggested, and observed in two studies of masked t(9;22), that the second Ph chromosome is an exact duplication of the entire derivative chromosome 22. In a cytogenetic study of bone marrow cells from an acute myelogenous leukemia patient, a cell line carrying two different Ph chromosomes evidenced by a chromosome 22 centromeric heteromorphism was found. From this observation arose the question whether the second der(22) was a true Ph chromosome or whether it was a deleted chromosome derived from the normal chromosome 22 that did not contain the bcr-abl rearrangement. A fluorescent in situ hybridization (FISH) study with the t(9;22) probe revealed two bcr-abl positive signals on 60 of 100 interphase nuclei. The second Ph could have resulted from a mitotic crossing over; or, analogously to late-appearing Philadelphia chromosomes, it may be derived from a new chromatid translocation between the chromosomes 9 and 22 not involved in the initial t(9;22).
González García
J R
JR
División de Genética, Centro Médico Nacional de Occidente, Institituto Mexicano del Seguro Social, Guadalajara, Jalisco, Mexico.
Garcés Ruíz
O M
OM
Delgado Lamas
J L
JL
Ramírez-Dueñas
M L
ML
D000293:Adolescent; D002869:Chromosome Aberrations; D002892:Chromosomes, Human, Pair 22; D016044:Fusion Proteins, bcr-abl / Q000235:genetics; D015321:Gene Rearrangement; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000235:genetics*; D015470:Leukemia, Myeloid, Acute / Q000235:genetics*; D008297:Male
D016044:Fusion Proteins, bcr-abl