Eline BeertCatholic University of Leuven

Belgium

To investigate the malignant transformation

of a pre-existing (plexiform) neurofibroma towards an MPNST

(sub)cutaneous neurofibroma isolated tumour in or under the skin mostly asymptomatic

plexiform neurofibroma spreads along a peripheral nerve disfiguring, difficult to remove

atypical neurofibroma symptomatic

painful, actively growing increased glucose uptake (FDG-PET scan)

pathology no mitoses ~ benign neurofibroma BUT! hypercellular regions and atypical

cells

MPNST 8-13% life time risk difficult to detect in early phase

(→ bad prognosis if detected late) metastasize often five year survival of only 25%

33 NF1 patients → 52 PNSTs 8 (sub)cutaneous neurofibromas 7 plexiform neurofibromas 11 atypical neurofibromas 2 low grade MPNSTs 2 intermediate grade MPNSTs 22 high grade MPNSTs

genetic analysis high resolution 244K oligonucleotide aCGH

(Agilent Technologies) CDKN2A (9p21.3) and TP53 (17p13.1)

mutation analysis

243 504 oligonucleotide probes 60-mer each spotted once

overall median probe spacing of 8,9 kb

average resolution of ± 10kb

neurofibroma atypical neurofibroma high grade MPNST

9p21.3 → CDKN2A

• neurofibromas→ no deletion

• atypical neurofibromas→ 10/11 deletion (1 homozygous)

• MPNSTs:• low grade

→ 2/2 deletion(1 homozygous)

• intermediate grade → 1/2 deletion

• high grade → 15/22 deletion(10 homozygous)

17p13.1 → TP53

• neurofibromas→ no deletion

• atypical neurofibromas→ no deletion

• MPNSTs:• low grade

→ no deletion• intermediate grade

→ 1/2 deletion• high grade

→ 11/22 deletion

neurofibroma atypical neurofibroma high grade MPNST

8 (sub)cut. neurofibr.

7 plexif. neurofibr.

11 atyp. neurofibr.

MPNSTs

2 Low gr.

2 Int. gr.

22High gr.

CDKN2A

Deletion (homozyg.)

0/8 0/710/11 (1)

2/2 (1)

1/215/22 (10)

Mutation 0/8 0/7 0/11 1/2 0/2 1/22

TP53

Deletion (homozyg.)

0/8 0/7 0/11 0/2 1/211/22 (0)

Mutation 0/8 0/7 0/11 0/2 0/2 3/22

Chr.

Overlapping region

Atypical neurofibr.

MPNST Tumor-suppressorgenesLow gr. Int.

Gr.High gr.

1 1p33 0/11 0/2 1/2 12/22 CDKN2C

9 9pter-p24.1 4/11 1/2 1/2 14/22 ?

9p21.3 10/11 (1) 2/2 (1) 1/2 15/22 (10)

CDKN2A,CDKN2B

10 10p13-p11.1

2/11 0/2 2/2 14/22 (2) ?

10q23.31 0/11 0/2 1/2 9/22 PTEN

11 11q23.1-qter

1/11 0/2 1/2 16/22 (1)

?

13 13q14.2 1/11 0/2 2/2 8/22 RB1

17 17p13.3-p12

0/11 0/2 1/2 11/22 TP53

18 18p 0/11 0/2 0/2 13/22 ?

18q23 0/11 0/2 1/2 13/22 ?

20 20p12.2-p12.1

0/11 0/2 0/2 11/22 ?

22 22q11.22 0/11 0/2 0/2 11/22 ?

Chr. Overlapping region

Atypical neurofibr.

MPNST Oncogenes

Low gr. Int. Gr.

High gr.

3 3q26.32 0/11 0/2 0/2 5/22 PIK3CA

4 4q12 0/11 0/2 1/2 9/22 PDGFRA, KIT

7 7p11.2 0/11 0/2 0/2 15/22 EGFR

7q21.2 0/11 0/2 1/2 10/22 CDK6

7q31.2 0/11 0/2 1/2 14/22 MET

8 8q 1/11 0/2 0/2 18/22 MYC

12 12p13.32 0/11 0/2 0/2 10/22 CCND2

12q14.1 0/11 0/2 0/2 8/22 CDK4

12q15 1/11 0/2 0/2 10/22 MDM2

17 17q24.3-25.3

1/11 0/2 1/2 13/22 BIRC5

20 20q13.33 0/11 0/2 1/2 11/22 ?

Chr. Overlapping region

High grade MPNST

Oncogenes

4 4q12 5/22 PDGFRA, KIT

7 7p11.2 6/22 EGFR

8 8q24.21 9/22 MYC

12 12q15 6/22 MDM2

17 17q25.3 6/22 BIRC5

Signaling pathways possibly involved in malignant transformation RB pathway

CDKN2A (p16INK4A), CDKN2B (p15), CDKN2C (p18) CDK4/6 RB1

p53 pathway CDKN2A (p14ARF) MDM2 TP53

RTK/RAS and effector pathways RTKs: EGFR, PDGFRA, MET RAS/MAPK pathway RAS/PI3K pathway (PIK3CA)

atypical neurofibromas→ already multiple chromosomal aberrations compared to high grade MPNST

smaller and less frequent deletions and duplications in lower percentage of cells

role for inactivation of CDKN2A no difference between atypical

neurofibromas and low grade MPNSTs (! small sample size)

aCGH = a good tool to investigate genomic imbalances in tumours

if possible: detection and resection of atypical neurofibromas before further evolution

Prof. Dr. Eric Legius Prof. Dr. Raf Sciot Bruno Daniëls Hilde Brems Prof. Dr. Ivo De Wever Prof. Dr. Frank Van Calenbergh Prof. Dr. Maria Debiec-Rychter