Letter: PH1 translocation involving chromosomes 21 and 22

Radiation exposure and chromosome abnormalities. Human cytogenetic studies at the National Institute of Radiological Sciences, Japan, 1963-1988

The results of human cytogenetic studies performed at the National Institute of Radiological Sciences (NIRS), Chiba, Japan for about 25 years are described. The studies were pursued primarily under two major projects: one involving people exposed to radiation under various conditions and the other involving patients with malignant diseases, especially leukemias. Whereas chromosome abnormalities in radiation-exposed people are excellent indicators of radiation exposure, their behavior in bone marrow provide useful information for a better understanding of chromosome abnormalities in leukemias and related disorders. The role of chromosome abnormalities in the genesis and development of leukemia and related disorders is considered, suggesting a view for future studies in this field.

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.

Genomic diversity of Philadelphia-positive chronic myelogenous leukemia

The incidence of breakpoints in CML patients with variant translocations was investigated. There was no relationship between the length of various chromosomes with breakpoint frequency. However, a significantly higher (p less than 0.05) incidence of breaks were seen on the long arms as compared to the short arms due mainly to the involvement of 9q and 22q in these translocations. Chromosome 17 showed a significantly (p less than 0.005) higher involvement in these translocations, however only when 9q34-qter was not cytogenetically involved. A total of 683 breaks were found in 225 cases. 362 of these were located at c-abl and c-sis, while 110 were at other oncogenetic sites. The prognostic and hematologic features of patients with variant translocations are not significantly different from those of CML cases with the typical 9q;22q translocation. Some of these complex translocation, where the breakpoints are correlated with oncogenetic sites, are further discussed in molecular terms.

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.

Chronic myelogenous leukemia with translocations (3q-;9q+) and (17q-;22q+). Possible crucial cytogenetic events in the genesis of CML

Two reciprocal translocations involving chromosomes 3, 9, 17, and 22 were found in a patient with seemingly Ph1-negative chronic myelogenous leukemia (CML). The two translocations were t(3;9)(q21;q34) and t(17;22)(q21;q11); the breakage in chromosomes 9 and 22 apparently occurred at the same point as in the usual Ph1 translocation, t(9;22)(q34;11). From the present evidence and a review of the literature it appears that the breakage on both chromosomes 9 and 22 at the special regions and the separation of the fragments are present in practically all standard and variant Ph translocations, even those in which the terminal region of the long arm of chromosome 9 and (9q) does not seem to be involved in the rearrangement; however, a translocation between chromosomes 9 and 22 is not an obligatory result of the rearrangement, as seen in the present case. Thus, we postulate that the breakage on both chromosomes 9 and 22 at the special regions and separation of the fragments are the crucial cytogenetic events in the genesis of CML and stress the importance of paying careful attention to the terminal region of 9q, particularly when chromosome 9 does not seem to be involved in the rearrangement.

Chromosomes and causation of human cancer and leukemia: XL. The Ph1 and other translocations in CML

To date, 85 cases with unusual Ph1 translocations have been described and are summarized in the present work. Of the 85 translocations, 41 were simple and 44 complex. Only chromosomes #1, #4, #8, and #20 and the Y have not been found to be involved in simple translocations and #12, #16, #18, #20 and the Y in complex ones. Chromosomes #18, #20, and Y have not been involved to date in either complex or simple Ph1 translocations. Four cases have been reported in whom more tan three chromosomes were involved in the Ph1 translocation and only four cases in whom the #9 was not involved in complex Ph1 translocations. The chromosomal changes, in addition to the Ph1, accompanying unusual Ph1 translocations in CML are not different from those seen in cases with the standard type of Ph1 translocation. Translocations (other than the Ph1) in CML occur in less than 1% of the cases and, to date, have found to involve all the chromosomes except the X and Y. With rare exceptions, in complex Ph1 translocations 1) the distal end of #22 is translocated to a third chromosome (i.e., other than #9), a part of which is translocated to #9, #2) the breaks in the involved chromosomes probably occur concomitantly, and 3) a characteristic PH1 chromosome is present. The survival of patients with CML and unusual or complex Ph1 translocations does not differ significantly from that of patients with the standard Ph1-translocation.

New complex Ph' translocation t (10; 14; 22) in bone marrow cells and in PHA-stimulated peripheral blood cultures in chronic myelocytic leukaemia

A patient with chronic myelocytic leukaemia (CML) and a new complex Philadelphia chromosome (Ph') translocation, t (10; 14; 22), is described. This three way Ph' translocation not involving chromosome 9 was present in the majority of the bone marrow cells, as well as in a great proportion of metaphases from phytohaemagglutinin (PHA) stimulated peripheral blood cultures. The possibility that the Ph' translocation was present also in lymphocytes is discussed and at this regard the involvement of chromosome 14 is of interest considering the documented non random involvement of chromosome 14 in lymphoid malignancies.

The chromosomes and causation of human cancer and leukemia: XXXVIII. Cytogenetic experience in Ph1-negative chronic myelocytic leukemia (CML)

Among 300 patients with chronic myelocytic leukemia (CML) followed at our institute during the last ten years, 36 (12%) were thought to have Ph1-negative CML. In eight of these patients, chromosomal abnormalities were found in the leukemic cells; in four, the karyotypic abnormalities were established with banding techniques. The data of the present study and a review of the literature regarding chromosomal changes in Ph1-negative CML indicate that: 1) no characteristic or consistent karyotypic change is present in Ph1-negative CML and that diploidy is more common in this than any other leukemia; 2) the most common changes involve group C chromosomes (particularly +8); and 3) a missing Y is less common in Ph1-negative CML than in its Ph1-positive counterpart. The karyotypic changes in Ph1-negative CML resemble more those encountered in Ph1-positive CML than in acute myeloblastic leukemia (AML). The much shorter survival of the Ph1-negative CML patients vs that of the Ph1-positive group was again substantiated, and some of the previously reported clinical and laboratory findings unique to Ph1-negative CML were confirmed. On the basis of the cytogenetic findings it is concluded that Ph1-negative CML appears to be an entity unto itself.

Transposition of 9q34 and 22 (q11toqter) regions has a specific role in chronic myelocytic leukemia

Six cases are reported of variant Ph' translocations found among 240 patients with Ph'-positive CML. Five cases had a three-chromosome rearrangement involving, in addition to chromosomes 9 and 22, chromosomes 7, 4, 2(two), and 3, respectively, and one case had a two-chromosome rearrangement 22/5. A review of the literature revealed that three- and two-chromosome variant Ph' translocations are observed with equal frequency. It is postulated that all variant translocations are indeed three-chromosome rearrangements, that the specific event for the formation of the Ph' chromosome is the reciprocal translocation 9/22, and that the transposition of regions 9q34 and 22 (q11toqter), plays a major role in the development of CML.

Evolution of karyotypes in Philadelphia (Ph1) chromosome-negative chronic myelogenous leukemia

Ten of 55 patients with chronic myelogenous leukemia (CML) diagnosed between 1972 and 1977 were found to lack the Philadelphia (Ph1) chromosome. Serial clinical, morphologic, and cytogenetic studies of patients with Ph1-negative CML showed that 30% of them had chromosomal abnormalities. Two had an extra chromosome No. 8 at the time of blast crisis, with a morphological picture of myeloblasts in the bone marrow. A third patient had a 6:14 translocation initially Abnormalities of chromosome No. 14 are frequently seen in lymphoproliferative disorders, and the bone marrow and peripheral blood contained a significant population of lymphoblasts as well as myeloblasts. The median survival for the 10 patients was 19 months. The exact nature of Ph1-negative CML is not yet clear; disease appears to be a distinct entity among the myeloproliferative disorders.

Chromosome abnormalities in leukemia

The consistent occurrence of nonrandom chromosome changes in human malignancies suggests that they are not trivial epiphonomena. Whereas we do not understand their significance at present, one possible role which they may fulfill is to provide the chromosomally aberrant cells with a proliferative advantage as the result of alteration in the number or location of genes related to nucleic acid biosynthesis. The proliferative advantage provided by various chromosome aberrations is likely to differ in patients with different genetic constitutions.

Atypical chronic myelogenous leukemia with Philadelphia (Ph') chromosome and an additional translocation

A case of chronic myelogenous leukemia in which the disease pursued an atypical course is described. The presence of a previously unreported translocation t(1;20), in addition to a Ph' chromosome t(9;22), is demonstrated, and its possible significance and relationship to the disease are discussed.

Evidence that chromosome band 22q12 is concerned with cell proliferation in chronic myeloid leukaemia

A man and two of his three children carried an abnormally short chromosome 22 resembling the Philadelphia chromosome (Ph1). Giemsa banding showed that the abnormal chromosome resulted from a translocation t(11;22) (q25;q13). The breakpoint on chromosome 22 was at the q12/q13 band interface compared with the breakpoint of Ph1 at the q11/q12 band interface. The absence of leukaemia or haematological disorder in members of this family suggests that the critical genetic site on chromosome 22 concerned with abnormal myeloid cell proliferation in human leukaemia is contained in the 22q12 band.

Non-random karyotypic evolution in chronic myeloid leukemia

The chromosome banding pattern was analyzed in bone-marrow cells and/or spleen cells of 10 patients in the blastic phase of chronic myeloid leukemia (CML). It was obvious from the karyotype analysis that the chromosome aberrations occurring addition to the Philadelphia chromosome (Ph1) were strictly non-random. An extra Ph1, trisomy 8 and/or trisomy for the long arm of chromosome 17 were observed in all cases. This consistent pattern of chromosome involvement in CML was confirmed in 57 cases from the literature studied with banding techniques. In 88% of the total number of cases with further changes at least one of the three main chromosomal aberrations was found ("major route" of karyotypic evolution).

Chromosome banding studies in Philadelphia chromosome positive myeloid leukaemia

A cytogenetic study of Ph1 positive myeloid leukaemia in both chronic and acute phases had been made by a chromosome banding technique. The translocation (t(9;22)(q34;q11), designated t(Ph1) was present in the myeloid cells of 43 of 44 patients; the exceptional case had normal number 9 chromosomes and a different translocation (t(19;22)(q13;q11)). A translocation additional to that involving the Ph1 was found as a stable abnormality present in all myeloid cells in 4 patients, chromosome 17 being involved in 2. The association of isochromosome number 17 with blast crisis was confirmed. New data were obtained concerning the significance of duplicated or dicentric Ph1 chromosomes and their relationship with the 9q+ anomaly. Monoclonal origin of Ph1 was confirmed in cases with polymorphic number 22 or 9 chromosomes.

Chromosomes and causation of human cancer and leukemia. XVI. Banding studies of chronic myelocytic leukemia, including five unusual Ph11 translocations

Forty-two Ph1-positive cases of chronic myelocytic leukemia (CML) were examined with chromosomal banding techniques. Thirty-seven of these cases had the "standard" type of Ph1 translocation between chromosomes No. 9 and No. 22 [t(9;22)(q34;q11)] in the Ph1-positive marrow cells; 5 cases had unusual types of Ph1 translocation. Of the 37 cases, 21 had additional numerical and/or structural chromosomal changes, 2 had a missing Y chromosome, and 1 had an extra Ph1 in the Ph1-positive cells. In the 5 cases with unusual types of Ph1 translocation, chromosomes No. 2, No. 9 No. 10, and No. 13 were involved. The clinical picture in these 5 patients did not differ materially from that of the other Ph1-positive patients with CML, probably indicating that the recipient chromosome, with which the translocation from No. 22 takes place, does not play a crucial role in the course of the CML. In the 21 cases with abnormal karyotypes, nonrandom chromosomal changes were observed. Most of the changes were related to events occurring at the centromeric region. The prognosis of cases with only an extra No. 8 or Ph1 appears to be better than that for cases with an iso-17q [I(17a)] chromosome or other extra chromosomes. The presence of the Ph1 (delected No. 22) in every case points to the essentiality of this karyotypic findings in the diagnosis of CML and possibly in the genesis of the disease.

A new translocation associated with the Ph1 chromosome and an acute course of chronic granulocytic leukaemia

Images