Accumulation of chromosomal changes in human glioma progression

ELSEVIER

Accumulation of Chromosomal Changes in Human Glioma Progression A Cytogenetic Study of 50 Cases Maria Dgbiec-Rychter, Janusz Alwasiak, Pawe] P. Liberski, Bogus|aw Nedoszytko, Ma]gorzata Babihska, Krzysztof Mr6zek, Brunon Imielifiski, Jolanta Borowska-Lehman, and Janusz Limon ABSTRACT: Cytogenetic studies of 50 human gliomas, including three oligodendrogliomas, 16 grade I-III astrocytomas, and 31 glioblastomas multiforme, were performed using the short-term tissue culture method. The most common numerical chromosome aberrations were +Z -9, -10, -14, and loss of a sex chromosome. Structural changes involved predominantly the following chromosome arms: lq, 2q, 6q, 7q, 9p, 14q, 17p, and 18p. Losses of chromosomes 9, 10, and 14, often occurring simultaneously and in polyploid clones, were observed almost exclusively in high-grade gliomas, and appear to constitute important events during glioma progression. INTRODUCTION Brain tumors of glial orig:in constitute a very heterogeneous group of neoplastic lesions with respect to both histopathologic and clinical features One of the most characteristic features of these tumors is their predilection to recur in a more malignant form. This malignant progression has been associated with specific genetic events that seem to be correlated with various stages of malignancy [1-3]. Cytogenetically, the majority of low-grade gliomas are characterized by a normal karyotype or simple numerical changes, in particular trisomy 7, monosomy 10 and 22, or loss of a gonosome [4-10]. On the other hand, some anaplastic astrocytomas and most glioblastomas displayed highly complex karyotypes, with numerous structural and numerical aberrations, the presence of double minutes (dmin), as well as differences in a ploidy level [11-16]. Cytogenetic abnormalities revealed in gliomas may prove to be of significant prognostic value as a sign of tumor progression [17, 18]. In this report we present the results of cytogenetic analysis of 50 gliomas, including eight low-grade and 42 malig-

From the Laboratory of Electron Microscopy (M. D.-R., P. P. L.), and Department of Tumor Pathology (J. A.), Medical Academy of /Adz; Departments of Biology and Genetics (B. N., M. B., K. M., J. L.), Neurosurgery (B. I.), and Pathology (J. B-L.), Medical Academy of Gdattsk, Poland. Dr. KrzysztofMr6zek'spresent address is: Cytogenetics Research Laboratory, Division of Medicine, Boswell Park Cancer Institute, Buffalo, NY 14263. Address reprint requests to: Dr. Maria Dgbiec-nychter, Laboratory of Electron Microscopy, Department of Oncology, Medical Academy of L6dz, 4 Paderewski St, 93-509 t,6dz, Poland. Received December 28, 1994; accepted May 26, 1995. Cancer Genet Cytogenet 85:61-67 (1995) © Elsevier Science Inc., 1995 655 Avenue of the Americas, New York, NY 10010

nant tumors. Low-grade tumors had either a normal karyotype or simple numerical changes, whereas most malignant gliomas displayed complex chromosome aberrations. Polyploidy and a combination of monosomy 10 with total or partial monosomy of chromosomes 14 or 9 were relatively frequent findings in our series, and they appear to constitute important events during glioma progression. MATERIALS AND METHODS Cytogenetic analyses were performed on 47 newly diagnosed and three recurrent cerebral gliomas consisting of one pilocytic astrocytoma, four fibrillary astrocytomas, three oligodendrogliomas, 11 anaplastic astrocytomas (AA), and 31 glioblastomas (GM). All lesions were classified morphologically according to the WHO classification [19]. The specimens were obtained by routine craniotomy and delivered immediately to the cytogenetic laboratory. The chromosomes were obtained from primary, short-term (from 1-14 days) tissue cultures as previously described [20], and G-banded. The description of the karyotypes followed the recommendations of the ISCN (1991) [21]. RESULTS From the total group of 50 patients (32 men and 18 women), successful cytogenetic analysis was performed in 46 cases. A summary of the clinical, histopathologic, and cytogenetic data of these cases is presented in Table 1. In 10 cases (22%), including two oligodendrogliomas, three fibrillary astrocytomas, three AAs, and two GMs, exclusively normal karyotypes were found. Among 36 gliomas with an abnormal

0165-4608/95/$9.50 SSDI 0165-4608(95)00129-D

M. D ~ b i e c - R y c h t e r et al.

62

Table

1

S u m m a r y of c l i n i c a l a n d c y t o g e n e t i c d a t a of t h e 46 g l i o m a c a s e s

No./culture number

Age/sex

Histology Type Grade

Oligodendroglial tumors 1/T46 52/M Olig 2/T63 3/Tl10

21/M 25/M

Astrocytomas 4/T51 32/F 5/G131 6/G206 7/G748 8/T54

9/F 45/F 34/M 12/F

Clinical stage

Postoperative survival (months)

II

GIT2IB

AI(6)

Olig AO

II III

GIT3IB GIT3IIIB

Al(3) Al(9)

PA

I

GITIIA

A1(18)

FA FA FA FA(r)

II II II II

G2T3IIB G2T3IIB G2T3IIB G4TIIV

D(4) D(6) ND A1(46)

III III III

G3T3IIIB G3T3IIIB G3T2IIIB

A1(12) D(56) Al(5)

Anaplastic astroctyomas 9/G650 40/M AA 10/G453 18/M AA 11/T145 29/F AA 12/T124

36/M

AA

III

G3T4IIIB

D(7)

13/G305

35/F

AA

III

G3T2IIIB

A1(24)

14/T38

10/F

AA

III

G3TIIII

A1(18)

15/G104

37/F

AA

III

G3T3IIIB

AI(17)

16/G656

54/M

AA

III

G3T3IIIB

Al(5)

Karyotype [number of cells] Q 46,XY[7] Nonclonal[5] 46,XY[20] 44-46,XY,del(1)(q21),add(1)(q44),add(13)(p13), - 16, - 17, - 19[cp9] 46,XY[7] 47,XX, + 7[8] 46,XX[17] 46,XX[10] 46,XX[11] 46,XY[10] 45,X, - X[4] 46,XX[16] 46,XY[10] 46,XY[20] 46,XX,inv(9)(p 13q13)c[15] Nonclonal[5] 46,XY,dmin[11] 46,XY[12] 45,X, - X[3] 46,XX[13] 47,XX, + 7[3] 47,XX, + marl[2] 46,XX[11] Nonclonal, + mar2[5] 40-45,XX,del(3)(q11.2),der(4)t(4; 15)(p13;q13),add(11)(p11.2), add(16)(q22),der(?)t(?;1)(?;q21)[17] 90-104<4n>XXYY,

+ 2,add(2)(p21),del(3)(p23),

- 6, + 7, - 9, - 9,

- 10, - 10, + 12,inc[6]

17/T75 18/T138

56/M 40/F

AA AA

III III

G4T3IIIB G4T3IV

D(17) D(
45-46,XY,der(1)t(1;2)(p36;q13), + 7,del(11)(q13),dmin[cp12] 90-95<4n>XXXX,

+ 1,del(4)(qal)x2,

- 8, + 15, - 22, - 22,

dmin[cplO]

46,XX[8] Nonclonal with different markers [5] Glioblastomas 19/G161 20/G163 21/Tl13

multiforme 28/M GM 64/M GM 40/F GM

IV IV IV

G4T2IV G3T3IIIB G4T2IV

D(8) D(6) AI(10)

22/G457

49/F

GM

IV

G4T4IV

D(
23/G200

33/M

GM

IV

G4T2IV

D(6)

24/T73

46/M

GM

IV

G4TIIV

D(9)

25/G183

56/F

GM

IV

G3T3IIIB

D(
26/G227

44/M

GM

IV

G4T4IV

D(14)

27/G454

4/F

GM

IV

G3T31IIB

D(1)

49/M

GM

IV

G4T2IV

28/T4

D(
46,XY[15] 46,XYIsl 45,X, - X[31 46,XX[12] Nonclonal[7] 47,XX, + 7[3] 46,XX[23] 45,X, - Y[5] 46,XY[15] 45,X, - Y[10] 46,XY[10] 44,X, - X, - 9,add(14)(p11.2)[20] 46,XX[4] 44-45,X, - Y, - 1,del(1)(p13),der(1)t(1;2)(q12;q21.2),der(1)t(1;3) (q21;p12),der(2)t(2;2)(p23;q21),del(3)(p22), - 5,der(8)t(3;6) (p13;q21),add(10)(p13), - 11, - 14,der(19)t(14;19)(q11.2;p13.1) [cp19] 43,X, - X, - 3,del(B)(q13),der(9)del(9)(p13)add(9)(q34) - 16,der(20) t(7;20)(ql 1.2;q13.3)[13] 48,XY,del(6)(q23),der(10)t(7;10)(q22;q22),add(14)(q11.2), + 20, + mar[9] Nonclonal[11] 46,XY[3]

(continued)

63

Cytogenetics of Human Gliomas Table 1 Continued No./culture number

Histology

Clinical

Postoperative survival

stage

(months)

Age/sex

Type

Grade

29/T22

44/F

GM

IV

G4T21V

D(7)

30/T24

' 59/M

GMIr )

IV

G4TIIV

D(9)

31/T35

34/M

GM[r)

1V

G4TIIV

D(14)

32/T72

63/M

GM

IV

G4TIW

AI(4)

33/Tl19

38/M

GM

IV

G4T2IV

Al(9)

34/T125

51/M

GM

IV

G4T2IV

A1(11}

35/T64

64/M

GM

IV

G4T4IV

D(2)

36/T66

62/M

GM

IV

G4TIIV

Al(3)

37/T20

65/F

GM

IV

G4T2W

D(4)

K a r y o t y p e [ n u m b e r of cells] a 45-46,XX,del(6)(q22),del(7)(p15],add(14](q13), - 18[cp14] 44,X, - X, - 22[4] 39-63,XY,der(2)t(2;5)(q31;q13), - 4, - 6,i(6}(p10), - 10,der(17) t(4;17)(q21;q25),i(18)(q10), + 5mar,inc[cp19] 41-45,XY, - 1,dic(1;6)(q21;q27),add(2)(p13), + 3,add(3)(p25},add(3) (p11), + 7,del(9)(p13),dic(11;22)(p15;p11), - 14,der(18)t(17;18) (q11.2;p11.3),der(19)t(14;19)(q13;q13.1), + 20,der(20)t(9;20) (q13;q13),der(22)t(2;22)(q13;q13)[cp20] N o n c l o n a l w i t h different m a r k e r s [6] 46-47,XY,del(6)(q25), + 11,del(11)(p11),dic(13;22)(p11;p11)[cp15] 46,XY[5] 44-45,X,del(Y)(q12),der(2)t(2;5)(p21;q21}, - 5,add(9)(q13), - 11, i(17)(q10)[cp8] 4 3 - 4 4 , X , - Y, - 3,der(3)t(3;17)(p12;q11),add(9)(p22)[cp5] 46,XY[10] 42-44,XY, + 7,add(7)(p15),der(8)t(7;8}(q11;p23),der(?)t(?;9)(?;q13), - 10,der(11;17)(q10;q10),add(13}(q22), - 14, - 15,add(18)(p11.3), + 22,add(22)(p11)[cp18] 48-52,XY, - 2,add(2)(q37),der(?)t(?;2)(?;q21), + 5, + 6, + 7,add(7) (p12), + 8,del(9)(q12), - 10, + 12, + 13, - 15, + 17,der(18)t(18;22) (p11.2;q11),der(19)t(1; 19)(q21;q13),der(22)(12;22)(q14;p12), der(22)t(14;22)(q13;p12), + r[cp21] - 2, - 2,t(2;10)(p10;qlO),

81-92<4n>XXXX,

+ 7,del(7)(q22)x2,

- 9,

- 9, - 10, - 10, - 14, - 14, - 18, - 21,del(22)(q12)x2,dmin[cp10]

38/T32

54/M

GM

IV

G4T2IV

D(11)

47,XX, + 7,del(7)(q22)[3] 46,XX[3] 47,XY, + 7[5] 85-91<4n>XXY,

- Y, + 7, + 7, - 10, - 10, - 17, - 17, - 20, - 20[cp5]

46,XY[5] 39/T48

40/T49

49/F

60/M

GM

GM

IV

IV

G4T4W

G4T2W

A1(16)

D(4)

89-99<4n>XXXX,

+ 7, + 7, - 14, - 14, + 7mar,dmin[cplO]

47,XX, + 7[5] Nonclonal,dmin[4] 46,XX[12] 47-51,XY, + 5, + 7, + 8, + 22[cp16] 69-94<4n>XY,del(X)(q13),

- Y, + 7,add(7)(p12)x2,

+ 8, - 10, - 10,

- 13, - 14, - 14, + 20,del(20)(q13),dmin[cp11]

41/T79

52/M

GM

IV

G4TIIV

D(13)

47,XY, + 7,del(9](p12][13] 90-94<4n>XXYY,

+ 7, + 7,del(9)(p12)x2,add(10)(q22),

- 22,

- 22[cp11]

42/T84

42/M

GM

IV

G4T2IV

D(6)

46,XY[17] 45-49,XY, + 1, - 4, + 5, - 6,del(8)(p11.2),del(9}(p12], - 10, + 12, del(17)(p11.2)[cp11] 94-96<4n~idemx2, add(20)

- 14, - 14,der(14)t(14;14)(p11;q13}x2,

(p12)x2,dmin[cp4]

46,XY, + 7, - 10, + 11, - 13,drain[3] 46,XY[8] 43/Tl12

69/M

GM

IV

G4T21V

D(13)

87-90~4n>XXY,

- Y, - 9, - 9, - 10, - 10,der(10;14)(q10;qlO)x2,

- 14, - 14[cp7] 46,XY[18]

44/T129

43/M

GM

IV

G4T2IV

Al(6}

94<4n>XXYY,

+ 7, + 7,dmin[5]

46,XY[15] Nonclonal[7] 45/G148 46/T31

59/M 64/M

GM GI~I

IV IV

G3T3IIIB G4TIIV

D(10) D(12)

61-74,XXY<3n>, 81-89<4n>XXYY,

+ 7,add(9)(q13),

+ mar,inc[cp8]

+ 1,der(1)t{1;11)(q42;q23)x2,

der(11)t(11;21)(qla;q21)x2,

+ 7, + 7, - 10, - 10,

- 13, - 13, - 15, - 18, - 19, - 21, - 21,

+ mmrx2,dmin[cp15] 88-92<4n>XXY,

- Y, - 1, - 1, - 10, - 10, - 22, - 22, + mm'[cpS]

Abbreviations: PA, pilocytic astrocytoma; FA, fibrillary astrocytoma; AA, anaplastic astrocytoma; Olig, oligodendroglioma; AO, anaplastic oligodendroglioma; GM, glioblastoma; (1:), recurrence; AI, alive; D, deceased; ND, no data. ° Bold type indicates polyploid cells.

64

M. D~biec-Rychter et al.

karyotype, four had two or more unrelated clones and three contained variant subclones. In 61% of karyotypically abnormal tumors, the presence of normal metaphases was also revealed. Polyploid clones occurred in 12 tumors; in three of them the polyploid cell line was the only abnormal clone observed. In three other tumors, variant polyploid subcloues evolved from the existing near-diploid cells. Table 2 presents correlations between the cytogenetic results and the tumor grade and morphology.

Oligodendrogliomas Among the three oligodendrogliomas examined (all men, mean age 32.6 years, range 21-52 years), only a grade III tumor with anaplastic components (case 3/Tl10) had an abnormal, near-diploid clone with losses of chromosomes 16, 17, and 19, and structural aberrations of chromosomes 1 and 13.

Astrocytomas Grade I - I I Five tumors obtained from four women and one man (mean age 26.2 years, range 9-45 years) were investigated. In the only grade I tumor, pilocytic astrocytoma, trisomy 7 was a sole abnormality. Three of four grade II fibrillary astrocytomas had a normal karyotype; the remaining one showed an X chromosome loss in a small number of cells.

Anaplastic Astrocytomas Grade III Among the 10 investigated AAs (five women and five men, mean age 35.5 years, range 10-56 years), 3 had a normal karyotype (one with the constitutional inversion of chromosome 9), one showed double minutes in approximately one-half of the metaphases, two had simple, and four had complex clonal abnormalities. Simple abnormalities included loss of chromosome X in one case, and trisomy 7 and an unidentified marker chromosome found as the sole changes in separate clones in one tumor. Trisomy 7 was found as part of a complex karyotype in two other tumors. Double minutes were observed in three cases. None of the 12 breakpoints in structural aberrations of chromosomes 1, 2, 3, 4, 11, 15, and 16 was observed in two tumors in this group.

Gliohlastomas Among the successfully analyzed glioblastomas (22 men and six women, mean age 51.3 years, range 4-69 years), two had a normal karyotype, five had simple, and 21 had complex clonal abnormalities (Table 2). In cases 30/T24 and 45/G148, the low quality of chromosome banding precluded complete characterization of the karyotype. Twenty-five tumors had mainlines in the near-diploid range, and three GMs had mainlines in the triploid-tetraploid range. Seven tumors in the former group displayed the presence of near-tetraploid sidelines as well. The most prevalent abnormality among glioblastomas were gains of chromosome 7, seen in 12 cases (43%) (in five clones as a sole change), followed by loss of chromosome 10 detected in nine cases (32 %). The latter abnormality was observed only in polyploid clones in four cases. Other recurrent numerical deviations included loss of the following chromosomes: 14 (in five cases), X (in four cases), Y (in three cases), 9 (in three cases), 22 (in three cases), and 13 (in two cases). The distribution of total or partial losses of chromosomes 9, 10, and 14 encountered in the individual clones of 18 GMs and one AA is shown in Table 3. Total or partial losses of chromosomes 9 or 14 were associated with the total/partial loss of chromosome 10 in nine of these tumors, in five of them in polyploid clones. Moreover, the simultaneous loss of chromosome 10 or 10q/10p and chromosome 14 or 14q/14p was seen in seven cases. Double minutes were observed in varying size and number in six glioblastomas. Figure I summarizes the numerical and structural changes encountered in all 36 tumors with clonal chromosome aberrations. The most frequently identified structural abnormalflieswere deletions and translocations of chromosome 9. The breakpoints were localized at 9q13 in four tumors, and at 9p13 and 9p12 in two tumors each. Seven tumors displayed structural aberrations involving chromosome 14, with the breakpoints at 14q13 in four cases and at 14q11.2 in two tumors. Chromosome I was rearranged in four GMs; in three tumors the breaks occurred in lq21. The following bands were found as breaksites in two cases: 2p21, 2q13, 2q21, 7p15, 7p22, 17q11, 18p11, 19q13.1, and 22p11. As a consequence of chromosome

Table 2 Correlation between histologic grade, tumor morphology, and cytogenetic results from 46 cerebral gliomas Clonal chromosomal abnormalities (%) Normal or nonclonal abnormalities (%)

Near-diploid Simple Complex

Polyploid complex

Total

2(19) 10(36)

1 6 11 28

2(20) 10(36) 12(26)

3 5 10 28 46

Grade

I n III IV Histologic type Oligodendroglioma Astrocytoma Anaplastic astrocytoma Glioblastoma Total

5(83) 3(27) 2(7)

1(100) 1(17) 3(27) 4(14)

2(67) 3(60) 3(30) 2(7) 10(22)

2(40) 3(30) 4(14) 9(20)

3(27) 12(43) 1(33) 2(20) 12(43} 15(33)

Cytogenetics of H u m a n Gliomas

65

deletions and unbalanced translocations, partial monosomies or trisomies were observed, and these engaged specific parts of particular chromosomes with higher frequency than others (Fig. 1). Specifically, the most frequently lost was genetic material from 6q (six tumors), 9p (five tumors), 17p (five tumors), 14p (four tumors), and 18p (four tumors).

ti

li!r "ii" 'iii l!,tJ.,jilr '"

"

3

DISCUSSION The cytogenetic investigation of the present series of glial tumors confirms previous observations that high-grade tumors are more likely to ]have detectable genetic alterations than low-grade gliomas [2, 4, 6, 12-16]. We have found a normal karyotype or only n o n c l o n a l changes in five of seven (71%) grade I-II tumors, in three of 11 (27%) grade III astrocytomas, and in two of 28 [17%) grade IV glioblastomas. Twenty-six percent of tumors karyotyped revealed the presence of near-triploid/near-tetraploid clones, the frequency similar to that seerL by others [6, 9, 10, 12, 13]. In three tumors, all cells studied were polyploid. The short-term culture method provides the opportunity to assess the karyotype of the tumor itself and reduces the likelihood of artifacts caused by a long-term in vitro culture. Therefore, we believe that the polyploid cells originated in vivo. The presence of related subclones in 6% of our tumors, as well as independent clones in 9 % of cases, reflects genetic diversity that appears to characterize a substantial subset of glial tumors.

Table 3

Clone number

27/T454 34/T125 30/T24 36/T66 38/T32 29/T22 39/T48 16/G656" 25/G183 31fr34 26/G227 28fr4 35fr64 40/T49 37/'I"20 43fr112 46/1"31

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 la lb la lb 2

42/T84

Nillllll}ilillii,, ii

7

8

iiiii °

i

19

ii ,!i!ilili!

i

20

9

il

'

iHHHH~ 10

.

21

6

.........

."

HI!H!,IH!!!I!iii

"

5

'"i

11

22

Y

Figure I

X

Distribution of numerical and structural chromosomal abnormalities in 36 gliomas that contain clonal changes. Total and partial (being a consequence of structural abnormalities) monosomies and trisomies of specific chromosomes are shown on the left and right sides of the chromosomes, respectively.

Chromosome change(s) present in the clone(s) - 9/9p -

12

i

Chromosomes 9, 10, and 14 total or partial losses in karyotypically abnormal clones of 18 glioblastomas and one anaplastic astrocytoma a

Tumor number

41/T79

4

- 10/10q -/10p -

- 14/14q -/14p -

p p T T T q T T T p

T T

p p p p

T

p q T T T T T T q T T T

p p,q p q T T T T

p,q

Abbreviations: T, whole chromosomeloss; p, partial monosomyof the short arm; q, partial monosomyof the long arm; bold, poly-

ploid clones; a and b, related subcloneswith the same chromosomalmarkers.

66 Earlier cytogenetic analyses of glial tumors have identified nonrandom structural and numerical changes, including extra copies of chromosome 7, loss of chromosomes 10, 17, 22, or one of the sex chromosomes, and structural abnormalities of 9p and 19q [4-6, 9, 10, 12-14, 18]. Monosomy 13, 14, or 18 was found less frequently. Chromosomes 1, 3p, 6q, 8p, 11, 17p, and 20 were involved predominantly in structural abnormalities. The nature of individual cytogenetic abnormalities observed in our study was in general similar to that in previously reported series. However, the relative frequencies of some of these abnormalities were different than those reported before. In the present study, the most frequent autosomal abnormalities were total or partial trisomy 7 (46%) and total or partial monosomy 10 (26%). Less common numerical abnormalities included monosomy 9, 14, or 22, and sex chromosome losses. Chromosomes lq, 2, 6q, 9, 11, 14q, 17p, 18p, and 22 were also involved in structural aberrations, mainly deletions and translocations. Deletions, duplications, and translocations of chromosome 1 with breakpoints on lp, sometimes resulting in trisomy of lp, lq, or both arms, were frequently observed in glial tumors as well as in many other malignancies [22]. Structural abnormalities of chromosome 1 occurred in six tumors studied by us. In our series, abnormalities of chromosome 6, leading to partial monosomy of its long arm, were found in six tumors. However, each break occurred at a different site. Involvement of 6q in the brain tumorigenesis had been implicated previously by others [6, 13, 23]. These findings suggest that loss of a putative tumor suppressor gone or genes located on 6q may be an important event in the tumorigenesis of some gliomas, as it is in many other types of solid tumors and nonHodgkin's lymphoma [22, 24]. Structural abnormalities of chromosome 11, with the hreakpoints at 11p11.2, 11p15, 11q13, and 11q23, occurred in six patients in our series. Anomalies of chromosome 11 were reported in gliomas [7, 13, 18] and other neurogenic tumors, ependymomas and medulloblastomas [8, 25]. Cytogenetic studies and restriction fragment length polymorphism analyses have shown losses of chromosomes 13, 17, and 22 in subgroups of gliomas [2, 14, 23, 26]. In most instances, losses on chromosome 17 have been associated with the early stages of astrocytoma formation and losses of chromosome 10 with progression to a more malignant phenotype. Structural rearrangements of chromosome 17 leading to the loss of its short arm were seen in five of our tumors, all of which were clinically advanced glioblastomas. Loss of chromosome 22 was found in four cases, in three of them in near-tetraploid metaphases. Structural rearrangements of this chromosome were detected in additional four tumors. The trisomy 7 has been indicated to he highly associated with human gliomas by different authors [11-13]. While some authors postulated that trisomy 7 and gonosomal losses reflect normal in vivo organ mosaicism, others suggested that these abnormalities indeed might be the markers of neoplastic transformation [18, 27-30]. In the current series, trisomy 7 was revealed as a solitary abnormality in five tumors; one of them (14/T38) displayed another unrelated clone with an unidentified marker, and two others (38/T32 and 39/T48) had additional polyploid clones with trisomy 7 and further nu-

M. D~biec-Rychter et el. merical aberrations. In the two other tumors (37/T20 and 41/T79), clonal evolution of cells with trisomy 7 had taken place as estimated by the presence of the same chromosomal markers in the original, near-diploid clone and in the related polyploid one. On the other hand, in two tumors (46fF31 and 42/T84), trisomy 7 was present in only one of the two independent, cytogenetically abnormal clones. Since the possibility that both abnormal clones, with and without trisomy 7, originated from the common, cytogenetically normal ancestor cannot be ruled out, the relevance of trisomy 7 to the pathogenesis of gliomas still remains unclear. Structural rearrangements or loss of genetic material from the short arm of chromosome 9 have already been reported by several authors to be associated with glioblastomas [6, 12, 13]. Recently, gliomas with 9p deletions have proven to be hemi- or nullizygous for the interferon [~-1and interferon a gene cluster; these changes were associated specifically with the malignant phenotype [31, 32]. In our series, abnormalities of the 9p arm were found in five gliomas. Four tumors had a deletion: two displayed del(9)(p12) and two had del(9)(p13). Monosomy 10 was described as typical for glioblastomas by different investigators (for review see [1, 3]). We found total or partial loss of chromosome 10 in 13 tumors. It is of interest that in our series, loss of chromosome 10 often was found in polyploid clones of highly malignant tumor forms, and that it was associated frequently with total or partial monosomy of chromosome 14 or 9 (Table 3). Thus, total loss or deletion of chromosome 14 and 9 were seen together with the chromosome 10 abnormality in seven and five tumors, respectively. In five cases, these associations were observed in polyploid clones only. These findings, not previously described in gliomas, suggest that monosomy 14 and 9, together with monosomy 10, may constitute the progressive genetic events in glioma development and contribute to the process of histologic trasformation that often is seen in astrocytomas [33]. Chromosome 14 was only rarely indicated as a possible candidate for being a marker of progressive disease. Thus Houri et el. [34] reported cytogenetic analysis of six gliomas, two of which displayed abnormalities of chromosome 14 and resulted in patients' rapid death. Others described monosomy 14 or structural abnormalities with lower frequency in malignant gliomas [4, 9, 16, 18]. Abnormalities of this chromosome were seen mainly in sidelines or in polyploid cells [5, 6]. However, the loss of heterozygosity for chromosome 14 in subpopulation of malignant astrocytomas was shown recently by Fults and co-workers [23], and Ransom et el. [14]. These findings and our results suggest that chromosome 14 harbors a tumor suppressor gone, inactivation of which may contribute to the late stages of glioma development. Whether this gene is identical to a candidate tumor suppressor gene(s), located at 14q32, which is involved in the progression of colorectal carcinomas [35], awaits further study. In future, we are planning to apply interphase cytogenetics to paraffin sections to ascertain the cell origin and frequency of chromosome 14 loss in vivo, as well as its relationship with monosomy 10 and tumor ploidy level. In conclusion, our results are in agreement with previous observations that clonal evolution of gliomas involves

Cytogenetics of H u m a n Gliomas predominantly loss of genetic material, and that cytogenetic changes in gliomas become increasingly more complex with tumor progression. A c o m b i n a t i o n of monosomy 10 and 14 may be involved in such progression. However, the variability of genetic alterations ,occurring in gliomas suggest that there may be several pathways of tumor progression. Consequently, further cytogenetic and molecular genetic studies are required to specify those changes of the genome that influence clinical behavior of gliomas a n d may become clinically useful prognostic indicators.

67

17.

18.

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