Chromosome abnormalities in acute promyelocytic leukemia (APL)

CHROMOSOME ABNORMALITIES IN ACUTE PROMYELOCYTIC LEUKEMIA (APL)

H. VAN DEN BERGHE, MD, A. LOUWAGIE, MD, A. BROECKAERT-VAN ORSHOVEN, MD, G. DAVID, MD, R. VERWILGHEN, MD, J. L. MICHAUX, MD, A N D G. SOKAL, MD

Sixteen patients, 15 adults and one child, with APL have been studied cytogenetically; 14 of these had an abnormal karyotype (87%). Eleven of these consistently showed a t(15;17)(q26;q22) structural anomaly, one patient showed a 47,+8 karyotype, one a rearrangement of chromosomes #15 and #17, apparently different from that in the other patients, and one a #I7 deletion without a demonstrable translocation. As an additional chromosome change trisomy #8 was found in 5 cases and monosomy #7 in two. The t(15;17)(q26;q22) structural anomaly is highly characteristic of APL, is found in APL of children and adults, but it is apparently not associated with a clinically different form of APL.

Cancer 43558-562, 1979.

T HAS BEEN RECENTLY shown that a t(15q+, I 17q-) chromosome anomaly may occur in some cases of acute promyelocytic leukemia (APL)( 1-4). We wish to report chromosome findings in a series of patients with this disorder.

MATERIALS AND METHODS

During the last 5 years, 29 patients with APL have been diagnosed at our clinics. Of these, 18 (62%) were cytogenetically examined with 2 failures; results are thus available for 16 (55%) patients. The distribution according to sex, age, presence of disseminated intravascu- lar coagulation (DIG), remission obtained and survival of the karyotyped and non-karyotyped cases is similar (Table 1); It is, thus, un- likely that a sampling bias was present in this series. The criteria for the diagnosis of APL were those for acute nonlymphocytic leukemia (ANLL) with more than 50% promyelocytes in the bone marrow. Patients with less

From The Divisions of Human Genetics and Hematol- ogy, Departments of Human Biology and Medical Re- search, University of Leuven, and the Division of Hematology, Department of Internal Medicine, Univer- sity of Louvain, Belgium.

Supported in part by a grant from the ASLK-Can- cer Fund, Belgium. G.D. is an Aspirant of NFWO, Belgium.

Address for reprints: Dr. H. Van Den Berghe, Divi- sion of Human Genetics, Minderbroedersstraat 12, B- 3000 Leuven, Belgium.

T h e authors thank Dr. A. A. Sandberg, Roswell Park Memorial Institute, Buffalo, N. Y., for help and en- couragement and for revising the manuscript.

Accepted for publication April 9, 1978.

than 50% promyelocytes were not included, regardless of whether they presented DIC o r not. Promyelocytes were identified on the basis of their characteristic granules, as evalu- ated with light microscopy only. All patients except one were adults, the reason for this being that children with leukemia are treated in a different hospital.

Cytogenetic investigations were carried out on bone marrow and peripheral blood cells, using short term incubation (24 hours) or cul- turing without PHA for 48 hours. Chromo- some preparations were processed for R- banding; Q-banding was routinely performed on the cells of male patients and whenever possible, 100 metaphases were looked at to evaluate possible Y chromosome loss. At least 10 metaphases, and usually many more, were fully karyotyped.

RE s u LT s

Suitable chromosome preparations were obtained in all patients investigated, except for 2 cases in whom no mitoses were found. Among the 16 successfully karyotyped cases, 2 had a normal karyotype. Data about the patients with abnormal karyotypes are detailed in Table 2. Of these 14 patients, 11 (79%) showed a deletion in the long arm of #1’7 (17q-) and translocation of this material onto the long arm of #15 (Fig. 1). The deletion in # 17 appears to be in band q22, or in the inter- band region between q21 and q22.

The brightly fluorescent 92 1 band seems to be preserved in toto, and no material foreign

0008-543X/79/0200/0558 $0.70 0 American Cancer Society

558

No. 2 CHROMOSOME ABNORMALITIES IN APL . Van Den Berghe et al.

TABLE 1. Summary of Some Important Clinical Parameters in the Patients with APL

559

Survival in days or

months at Chromosome Nature Case Age at DIC on Remission last analysis o f t h e t(15q+, 17q-) no. Sex diagnosis admission obtained follow up done karyotype present

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

M 58 F 52 F 68 M 63 F 42 F 47 F 50 M 50 M 49 F 19 F 56 M 25 M 34 M 2 F 54 M 60 M 30 F 23 M 46 F 38 M 45 F 35 F 42 M 67 F 57 M 65 F 36 F 40 M 19

+ + + + + + +

-

- + + + + + + + + - + ?

+ + + ? + + ? +

-

Yes Yes no no Yes no no Yes no Yes no no Yes

treatment Yes no Yes no no yes no no Yes no Yes no ? ? no

39 months 24 months 19 days 10 days Alive >39m 8 days 23 days Alive >14m 36 days Alive >8m 47 days 9 days Alive >3m Alive > l m Alive >7m 22 days 2 months 24 days 3 months 28 months 13 days 1 day ? 36 days 8 months 2 days ? ? 29 days

abnormal abnormal abnormal abnormal abnormal abnormal abnormal abnormal abnormal abnormal abnormal abnormal a bnormal abnormal normal normal unknown unknown unknown unknown unknown unknown unknown unknown unknown unknown unknown unknown unknown

yes yes yes no Yes yes no yes* yes yes Yes yes Yes Yes no no no no no no no no no no no no no no no

~ ~~ ~

* Probably different anomaly (see Results).

to #17 was recognized in its long arm. The deleted segment q22 -+ qter, of which the fluorescent bands q22 and q24 are smaller and less bright than 15q24 and q26, and of which the R-negative band q22 is considerably big- ger than the R-negative 15q25, seems to be translocated onto the distal end on the 15q, in which no deletion was seen. N o reciprocity of the translocation could be observed in our material, but it is difficult to make a firm statement on this issue. In a considerable number of metaphases the quality of the banding did not allow for a detailed analysis, and in those the only statement that can be made was that some material from the long arm of # 17 was missing, and that quite often the long arm of # 15 was longer than usual. In metaphases of excellent quality, however, the structural anomaly was apparently similar in all cases. Hence, the structural anomaly which 11 of 14 cases have in common can be tentatively identified as t( 15; 17)(q26;q22). In 3 patients, this anomaly was not found (Nos. 1 , 4 and 8).

In case No. 1, a deletion of a #17 was consistently present, but we were unable to demonstrate a translocation. In case No. 4 no structural anomalies were found; the patient had a 47,XY,+8 karyotype. In case No. 8, one # I 7 and one #I5 were abnormal, but we could not detect a deletion of the #17. In- stead, it appeared as if one of the #15 chromosomes was considerably smaller than normal, whereas the abnormal # 17 seemed to have extra material on its long arm, indicating, that in this case, the structural anomaly in- volving chromosomes # 15 and # 17 could be a 15q-;17q+ translocation. In some patients additional anomalies were found (Table 2).

Case No. 7 is interesting in that besides cells with the 15/17 anomaly, other cells were found in the marrow as well as in the blood, in which the only anomaly was a +8. In the bone marrow, a combination of both anomalies was found, i.e., (47,XX,+8, t(15; 17)(q26;q22)). A similar situation was seen in Case No. 8, in which some cells with +9 rather than #8

560 CANCER February 1979 Vol. 43

TABLE 2. Cytogenetic Investigations in 14 Patients with APL and Abnormal Karyotype

Case Time of Total no. no. investig. mar./BI. cells Karyotype

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

Adm. Adm. Rem. Rem. Rel.

Rel.

Adm. Adm.

Adm.

Adm.

Adm.

Rem. Rem.

Adm.

Adm.

Ther.

Ther.

Adm.

Rem.

Adm.

Ther.

Adm. Ther. Rem.

Adm.

Ther.

Adm.

Adm. Rem.

Adm. Adm.

M B M M M

M

M B

M

M

B

M M

M

M

M

B

M

M

M

B

M M M

M

M

M

M M

M B

20 21 65 16 -

23

42 22

25

23

24

42 40

39

15

15

16

20

60

15

9

15 6

15

15

14

19

15 14

15 15

45,X(-Y)15%/46,XY,de1( 17)((122) 85% 46,XY,del( 17)(q22) 100% 46,XY ,normal 46,XY,norma1,70%/46,XY,del( 12)(ql1) 30% Failure

46,XX,t(15; 17)(q26;q22)

46,XX,normal,2 1%/46,XX,t( 15; 17)(q26;q22) 79% 46,XX,normal, 10%/46,XX,t( 15; 17)(q26;q22) 90%

47,XY,+8, 100%

46,XX,t( 15,17)(q26;q22),35%/46,XX,de1(7)(q33 or q35),t( 15; 17) (q26;u22) 65%

46,XX,ti15; 17)(q26;q22)25%(46,XX,de1(7)(q33 or q35),t( l5;17)

46,XX,normal 46,XX,norma1,80%/46,XX,t( 15; 17)(q26;q22) 20%

46,XX,t(15; 17)(q26;q22)

(q26;q22) 75%

47,XX,+8,12%/47,XX,+8,t( 15;17)(q26;q22), 68%/46,XX,-7,+8,t( 15; 17) (q26;q22), 20%

4n-normal 14% 46,XX,norma1,40%/47,XX,+8,26%/4'7,XX,+R,t( 15; 17)(q26;q22)20%/

46,XX,t( 15; 17)(q26;q22)24%/47,XX,+S,t( 15; 17)(q26;q22) 76%

46,XX,t( 15; 17)(q2 l?;q25?)20%/47,XY,+8,t( 15; 17)(q2 l?;q25?)50Y0/

48,XY,+8,+9,t(q2 l?;q25?) 18% 46,XY,normal

46,XY,norma1,26%'/46,XY ,t( 15; 17)(q26;q22), 13% 47,XY, +8,20%/47,Xk', +8,t( 15; 17)(q26;q22), 40% 46,XY,del( l)(q 12),20%'/46,XY,t( 15; 17)(q26;q22) 20% 47,XY,+8,10%/47,XY,del( I)(q 12)+8,10%/47,XY,+8,t( 15; 17)(q26;q22),

20%/46,XY,normal, 20%

46,XX,t( 15; 17)(q26;q22) 100% 46,XX,normal, 100% 46,XX,normal 100%

46,XX,t(15; 17)(q26;q22),15%/47,XX,-7,+8;- lO,t(15;17)(q26;q22)

47,XY,+S,t( 15; 17)(q21?;q25?) 12%

+ mar + mar,35%/47,XX,-7,-9,t( 15; 17)(q26;q22),+2 mar 15%/45, XX,- 10,t( 15;17)(q26;q22) 35%

46,XX,normal,57%/46,XX,t( 15; 17)(q26;q22) 43%

46,XY,norma1,30%/46,XY,t( 15; 17)(q26;q22), 20% 47,XY,t( 15; 17)(q26;q22)30%/various anomalies 20%

46,XY,t(15; 17)(q26;q22), 100% 46,XY,normal, 100%

46,XY,t(15; 17)(q26;q22) 100% 46,XY,norma1,13%/46,XY,t( 15; 17)(q26;q22) 87%

mar. M-Bone Marrow; bl. B-Blood; Adm.-Admission; Rem.-Remission; ReL-Relapse; Ther.-Therapy.

trisomy in combination with the 15/17 anomaly were present; in another cell line 48 chromosomes were found, in which besides the un- usual 15/ 17 translocation + 8 as well as trisomy of #9 were found. In Case No. 9 again some cells were found in which trisomy #8 was present as the sole anomaly before any treat-

ment. During the initial phase of the treatment, a structural anomaly of chromosome #1 ( lq- ) appeared in two otherwise normal cells, and also in one cell with a trisomy #8 without the 15/17 anomaly. In Case No. 1 1 several cell lines were found in the marrow before treatment. They included a 47,XX,

No. 2 CHROMOSOME ABNORMALITIES IN APL * Van Den Berghe et al. 56 1

FIG. 1. Characteristic karyotype in APL. Interpretation is as follows: A deletion occurred in band q22 or in the inter- band region between q21 and q22 of one chromosome # 17. T h e brightly fluorescent band q21 seems to be preserved in toto. T h e deleted segment q22 + qter is translocated upon the distal end (?) of chromosome # 15 (q) i .e. , Karyotype: 46,XX,t( 15; 17)(q26?;q22).

-7, + 8 , - 10,t( 15; 17)(q26;q22)+mar,+ mar cell line; a 47,XX,- 10,t( 15; 17)(q26;q22) +mar, +mar cell line, and a hypodiploid 45, XX,- 10,t(15; 17)(q26;q22) cell line. Finally, in Case No. 12, trisomy #8 was found in combination with the 15/17 translocation.

DISCUSSION To the best of our knowledge, 5 cases of

APL, studied with banding techniques, and showing a 15/17 anomaly have been pub- lished.'-* It was not known, however, whether this apparently characteristic anomaly occurred only sporadically or characterized a substantial number of cases of APL. The present paper contributes some answers to this question.

From the data presented, it appears that 14 out of 16 cases of APL showed an abnormal karyotype. There is no reason to assume that a sampling bias is responsible for the high proportion of anomalies in this series. We must, therefore, accept that about 90% of our APL cases have a major karyotypic anomaly at diag-

nosis. This, apparently, is a high proportion unknown sofar in acute leukemia, and only equalled by the proportion of chromosomal abnormalities in CML. Even more astonishing is the fact that this high proportion of anomalies is almost exclusively due to the 15/17 anomaly. Out of the 14 cases with abnormal karyotypes, 11 (79%) presented an apparently similar type of deletion and translocation. Of the three other cases, one was a 47 (+a), one showed a deleted #17 without a demonstrable translocation, and one was a 15/17 anomaly which may be different from the other 15/17 cases. Nevertheless, it is clear that the overwhelming majority of adult cases of APL present a standard type chromosome anomaly. It also appears from the data presented, that, as in other acute leukemias, some normal cells may still be found in the marrow and that the characteristic abnormality disappears during remission, to reap- pear before or during clinical relapse. That the anomaly is not confined to adult APL is shown by Case No. 14. The precise nature of

562 CANCER February 1979 VOl. 43

the 15/17 anomaly is not clear. Rowley et ~ 1 . ~ assumed that a break occurred in the region of band 15q22, with insertion of band 17q21 into the break on #15, ie., [46, ins (15;17)-

Okada et u Z . , ~ as well as Kaneko and Sak- urai,2 interpreted their cases as being the result of a reciprocal translocation of the distal parts of chromosome #15 and #17 [46, t(15; 17)(q22;q21)]. Our analysis does not favor the insertion hypothesis and, for the reasons explained in Results, we interpret the structural abnormality as being a t( 15; 17)-

Whatever its precise nature may be, this 15/17 anomaly is probably highly characteristic for APL. It has not been consistently found, thus far, in other myeloproliferative qr lym- phoproliferative disorders; generally, deletions of #17, apart from APL, seem to occur r.,ther infrequently. Only a few cases of #17 deletions have beeg seen in more than 500 cases with hematological disorder studied in our laboratory. A 17q- without demonstrable translocation has been found in single cases of myelosclerosis, polycythemia or pancyto- penia. A ( 1 1; 17)(q22;q21) translocation was present in a case of acute monoblastic leukemia, in one case of AL a 46,XX,t( 1 ; 17)(q44; q22), t(9;22)(q34;qll) karyotype was found and a t(5; 17)(q35?;q22) translocation appeared as an additional anomaly in a case of lymphoma. We have never seen the 15/17 anomaly in cases other than APL.

With regard to the additional anomalies, trisomy #8 was found in 5 cases, and the only case without a #17 abnormality, had a trisomy

(q22?;q21?)].

(q26;q22).

#8 as the sole anomaly. In two cases, monosomy #7, either occurring alone or as an additional chromosomal change, was present. Monosomy #7 is frequently encountered in ANLL, and trisomy #8 has been reported in almost every type of malignant hematological disorder. It is noteworthy that in 2 cases of the present series, both with the 15/17 anomaly, trisomy #8 not only occurred as an additional anomaly, but in some cells was the only chromosome change present. A #7q- was found in case No. 5 and was also present in one of Rowley’s patient^,^ but the breakpoints in the two cases were different. Two deletions, # lq- and #12q-, occurred later during the course of the disease, after treatment had been given. The # 12q- anomaly was found on two different occasions during clinical remission, without any other chromosomal change being present in these cells.

Finally, it appears that the 15/17 anomaly is not necessarily accompanied by DIC, and that both short and long survivals can be found in these cases. It is doubtful whether this characteristic anomaly may be of any help to the clinician in establishing the diagnosis of APL. Because of the DIC, many APL show a ful- minant course, and death of the patient may occur even before the chromosome investigation is finished. As in other leukemias, however, the chromosome investigation in APL will undoubtedly be of considerable help during remission, as the abnormal clone may re- appear in the marrow before any clinical signs of relapse are evident.

REFERENCES

1. Golomb, H. M., Rowley, J. D., Vardiman, J., Baron, J. M., Locker, G., and Krasnow, S.: Partial deletion of long arm of chromosome 17. Arch. Intern. Med. 136: 1:961, 1977. 825-828, 1976.

acute promyelocytic leukemia. Lancet 1 :961, 1977.

3. Okada, M., Miyazaki, T., and Kumota, K.: 15/17 Translocation in acute promyelocytic leukemia. Lancet

4 . Rowley, J. D.. Golomb, H. M., and Dougherty , C.: 15/17 Translocation, a consistent chromosomal change in acute promyelocytic leukemia. Lancet 1:549-550, 1977.

2. Kaneko, Y., and Sakurai, M.: 15/17 Translocation in

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Chromosome abnormalities in acute promyelocytic leukemia (APL)