Takaaki Ishihara

CHROMOSOMAL DIFFERENCES AMONG THE ACUTE LEUKEMIAS.

Spurred by recent developments in the technique of and knowledge in the examination of human mitotic, somatic chromosomes, many workers have investigated a variety of human diseases for specific and consistent karyotypic abnormalities. To date, several congenital anomalies have been shown to be characterized by definite chromosomal aberrations. In the area of malignant disease, only the abnormal Phl (“Philadelphia”) chromosome, belonging to the autosomal groups G21-G22, has been shown to occur with high frequency in chronic myelocytic leukemia (CML).’B~ On the other hand, the examination of cells from human cancer or cancerous effusions has failed to reveal a consistent abnormality at the karyotypic l e ~ e l . ~ , ~ In this paper we wish to report on the chromosomal differences between the lymphoblastic and myeloblastic forms of acute l e ~ k e m i a . ~ Other karyotypic findings will be presented to indicate that chromosomal changes may characterize the various acute leukemias, these changes being of potential aids in the diagnosis and therapy of acute leukemia.

A summary of cytogenetic studies on 534 cases of chronic myelocytic leukemia in Japan

Cytogenetic and clinical data on 534 patients with chronic myelocytic leukemia (CML) were collected from 10 institutions in Japan. The results of the analysis of the data were in substantial accord with those of the First International Workshop on Chromosomes in Leukemia and other published data, but certain differences were noted in the frequency of Philadelphia chromosome (Ph1)-negative cases, unusual and complex Ph1 translocations, and additional chromosome changes. Some of the findings are discussed with respect to the origin of unusual and complex Ph1 translocations, the relationship between chromosome abnormalities and survival, and geographic differences in chromosome abnormalities.

The Philadelphia chromosome. Considerations based on studies of variant Ph translocations.

The nature of the Philadelphia (Ph) translocation and the process of its formation were studied by attempting various chromosome banding analyses of variant Ph translocations among 210 patients with Ph-positive chronic myelocytic leukemia examined at the National Institute of Radiological Sciences, Chiba. The following assumptions could be drawn from the results of the analyses: 1) The involvement of specific regions of chromosomes #9 and #22, q34 and q11, respectively, is an indispensable condition of the Ph translocation. 2) The so-called variant Ph translocations are all complex and are derived from a standard Ph translocation. 3) The Ph translocations, both standard and complex ones, are not always stable. The complex translocations are subject to further chromosome evolution, as is the conversion of the standard translocation to complex translocations. There seems to be no fundamental difference between the standard and complex Ph translocations, with the latter being merely a more progressed form of the former. Analyses at the molecular level of the same cases employed in this study are yielding results that support the above assumptions.

Translocation (8;21) and its variants in acute nonlymphocytic leukemia: The relative importance of chromosomes 8 and 21 to the genesis of the disease☆

Chromosome analysis was performed in 25 patients with acute nonlymphocytic leukemia (ANLL), mostly of the M2 type. Eighteen had the standard translocation, t(8;21)(q22;q22), four had complex translocations involving 1p36, 11p13, 17p11, and 17p23, respectively, with chromosomes 8 and 21, and the remaining three patients had simple translocations, one with t(3;21)(p14;q22) and two with t(16;21)(p11;q22), without involving chromosome 8. Chromosome abnormalities additional to t(8;21) and its variants that were most frequently observed were -X, -Y, and del(9). Complex translocations are thought to be derived from the standard translocation and to be essentially similar in nature. The finding that chromosome 21 was involved in all of the standard, simple, and complex translocations, and that chromosome 8 was not involved in simple variants suggest a greater weight of chromosome 21 in the relative importance of the two chromosomes to the genesis of ANLL.

A summary of cytogenetic, morphologic, and clinical data on t(8q−;21q+) and t(15q+;17q−) translocation leukemias in Japan

Cytogenetic, morphologic, and clinical data of 33 acute nonlymphocytic leukemia (ANLL) patients with t(8q - ;21q+) and 19 patients with acute promyelocytic leukemia (APL) were collected from seven laboratories in Japan. The latter class included 18 patients with t(15q + ;17q-) and one with a normal karyotype. The t(8q - ;21q+) and t(15q + ;17q-) translocations were each shown to be associated with a specific type of ANLL, namely, AML-M2 and APL-M3, respectively. No patient with APL had the M3 variant. The t(8q - ;21q+) translocation seems to be more common as an abnormality in ANLL in Japan as compared to findings in other countries. The high incidence of t(15q + ;17q-) among Japanese patients with APL indicated in this study, however, still awaits confirmation.

A new rare distamycin a-inducible fragile site, fra(11)(p15.1), found in two acute nonlymphocytic leukemia (ANLL) patients with t(7;11)(p15-p13;p15)

SummaryFragile sites were analyzed in normal peripheral lymphocytes from two acute nonlymphocytic leukemia patients with t(7;11)(p15-p13;p15) leukemic cells. To induce expression of fragile sites, cultures were exposed to folate deprivation (M-F10), BrdU, distamycin A, or Hoechst 33258. Fragility at 11p15.1 was induced by distamycin A and Hoechst 33258 but was not seen in M-F10, BrdU, and control cultures. Fra(11)(p15.1) was found neither in healthy Japanese subjects (0 in 845) nor in patients with leukemia or other hematologic disorders without the t(7;11) (0 in 126). From these results, fra(11)(p15.1) can now be calssified as a rare distamycin A-inducible fragile site. Furthermore, this fra(11)(p15.1) coincided with one of the breakpoints of the t(7;11)(p15-p13;p15).

A culture technique for chromosome analysis in human myeloid leukemias

A simple culture technique for the study of cells from myeloid leukemias and other blood disorders of myeloid series is described. The procedure is the same with that of the ordinary cultures, except for the addition of colony stimulating factor. A large number of mitotic cells can be obtained, and they are quite suitable for banding treatments. Clear banding patterns are consistently obtained.

Distamycin A-inducible fragile sites and cancer proneness

To determine the baseline frequency of autosomal rare fragile sites in cancer patients, we conducted a population cytogenetic study of 370 patients with leukemias, solid tumors, and other neoplastic disorders. Twenty carriers of rare fragile sites were detected in this patient group. The rare autosomal fragile sites were at fra(8)(q24), fra(11)(p15), fra(16)(p12.1), fra(16)(q22), and fra(17)(p12). All of these fragile sites were found to be distamycin A inducible. Compared with a population incidence in healthy subjects (44 of 845, 5.21%), the overall incidence of distamycin A-inducible fragile sites was not higher in the patient group (20 of 370, 5.41%). Analysis of these individual fragile sites and particular diseases, however, suggests that the distamycin A-inducible fragile sites may play a role in the etiology of leukemia, myeloproliferative disorders, and benign tumors.

Heritable fragile sites and cancer: fra(16)(q22) in lymphocytes of an acute nonlymphocytic leukemia patient with inv(16)(p13q22).

Fragile site testing was performed on normal peripheral blood lymphocytes from three acute nonlymphocytic leukemia patients who carried inv(16)(p13q22) in malignant cells. Cultures were treated with BrdU, distamycin A, Hoechst 33258, or folic acid deprivation to induce fragile site expression. One patient was found to be a carrier of fra(16)(q22), but the expression was observed only by Hoechst 33258 treatment.

Heritable rare fragile sites in patients with leukemia and other hematologic disorders

Fragile site studies were performed on a total of 126 patients with leukemia and other hematologic disorders including myelodysplastic syndrome (MDS) and polycythemia vera (PV). Compared with an incidence (6.0%) of heritable rare fragile sites in the healthy population, the frequency was not higher in the patient group (3.2%), as a whole. However, two cases of fra(17)(p12) in MDS appeared fourfold larger than expected for this group of patients. In one case, a homozygous carrier of fra(17)(p12) in PV was also very rarely expected from its population incidence. These findings suggested a possible role of rare fragile sites, at least in the etiology of these preleukemic or myeloproliferative disorders.