Transcript Jonathan Fletcher

Cytogenetic Insights in
Mesenchymal Tumors
Jonathan A. Fletcher, M.D.
Pathology & Pediatrics
Brigham & Women’s Hospital
Dana-Farber Cancer Institute
Harvard Medical School
Boston, MA
How it is done!
Mince, then disaggregate cells by
overnight treatment with collagenase
Disaggregated
cells are plated
as monolayer
cultures on glass
slides or in
plastic flasks
All cultures are inspected daily, to determine
whether tumor cells are growing, and when
metaphase harvests should be performed
Leiomyoma: simple karyotype with t(12;14)
HMGA2
(HMGIC)
Leiomyosarcoma: G-banded karyotype
Complex!
Clonal (arrows) and
nonclonal aberrations
Example 1
Novel biologic mechanisms revealed
through indentification of recurrent
cytogenetic abnormalities in
mesenchymal tumors
Aneurysmal Bone Cyst
and the fusion fusion oncogene
Aneurysmal Bone Cyst
and the fusion fusion oncogene
Aneurysmal Bone Cyst
• Patients are generally < 20 years old
• Can recur locally, but do not become
malignant
• “Primary ABC” have been generally
regarded as nonneoplastic
• “Secondary ABC” associated with
–
–
–
–
osteoblastoma
chondroblastoma
giant cell tumor
osteosarcoma
Aneurysmal Bone Cyst
• 1999: Panoutsakopoulos et al.
reported translocation t(16;17) in two
ABC
– neoplastic basis
– recurrent oncogenic mechanism
Aneurysmal Bone Cyst
• 17p13 rearrangements in:
– “solid variants” of ABC
– soft-tissue ABC
• 25% of ABC have t(16;17)
• >25% of ABC have alternate
translocations, involving 17p13, but
not 16q22
Aneurysmal Bone Cyst
• t(16;17)
– 17p13 gene = USP6 (Ewing’s oncogene)
– 16q22 gene = CDH11 (aka “osteoblastic
cadherin”)
– promoter swapping between CDH11 and
USP6
• fusion of highly active CDH11 promoter to the
5’ UTR of USP6
Aneurysmal Bone Cyst
Corroboration of “promoter swapping”
mechanism in USP6 fusions
Translocation
Gene
Promoter
Swapping?
t(9;17)
osteomodulin
YES
t(17;17)
COL1A1
YES
t(1;17)
TRAP150
YES
t(3;17)
ZNF9
YES
Aneurysmal Bone Cyst
What is the neoplastic cell?
Mechanisms in secondary ABC?
USP6 oncogene in ABC
spindle-cells
USP6 oncogene is not found in
“secondary ABC”
Secondary ABC
Associated Chondroblastoma
USP6 or CDH11
Rearrangement in ABC
• 36 of 52 (69%) primary ABC
• 0 of 17 secondary ABC
– giant cell tumor
– osteoblastoma
– chondroblastoma
– fibrous dysplasia
USP6 is an evolutionarily-recent fusion of
the PRC17 and USP32 genes
(hominoid specific)
PRC17
USP32
TBC (rabGAP)
UBP
>95% identity
TBC (rabGAP)
USP6
UBP
USP6 Function: regulates
endocytosis/destruction of
activated proteins
CDH
11
TBC (rabGAP)
UBP
- inactivates rab family
members
-UBP protease reverses
ubiquitination
-rab function required for
endocytosis of activated
EGFR
- ?synergize with rabGAP
function to inhibit
endocytosis/proteolysis
USP6 Expression
• Normal expression restricted to
embryonic tissues and testis
• Neoplastic expression restricted to
mesenchymal tumors:
– 2 of 2 osteoblastomas
– 1 of 4 myofibromas
– 1 of 3 Ewing’s sarcomas
Conclusions
• USP6 is overexpressed due to promoter
swapping mechanisms in most primary ABC
• USP6 overexpression may stabilize
oncogenic proteins
• USP6 is an evolutionarily recent gene, with
likely relevance in sarcoma
• Useful models of mesenchymal tumor
biology can come from unlikely places
Example 2
Smooth Muscle Tumors
• Use of cytogenetic clues to identify
clinically-relevant biologic pathways in
a genetically complex disease
Leiomyoma: simple karyotype with t(12;14)
HMGA2
(HMGIC)
Leiomyosarcoma: G-banded karyotype
How do leiomyomas progress to
malignancy?
???
Intravenous Leiomyomatosis
t(12;14) with:
partial trisomy 12q
partial deletion 14q
Typical uterine leiomyoma
Balanced t(12;14)
Intravenous leiomyomatosis
Unbalanced t(12;14)
Partial trisomy 12q
Paola Dal Cin
Brad Quade
Cynthia Morton
Cytogenetic correlates for
leiomyoma progression
• Vascular invasion
– intravenous leiomyomatosis
– unbalanced t(12;14)
• Increased proliferation
– cellular leiomyoma
– deletion 1p (also common in lms)
• Distant metastases
– “benign metastasizing leiomyoma”
– deletions of 19q and 22q
Pulmonary Chondroid Hamartoma
(HMAG2 & HMGA1 oncogenes)
PCH: primitive mesenchymal, fat, chondroid
PCH: primitive mesenchymal, fat, chondroid,
smooth muscle
Leiomyosarcoma/Leiomyoma: where do they
start?
Is there proof that any sarcoma arises
from a differentiated mesenchymal cell?
•
•
•
•
•
•
•
osteo – bone
chondro – cartilage
lipo – fat
leiomyo – smooth muscle
rhabdo – skeletal muscle
fibro – myofibroblast
“GIST” – interstitial cell of Cajal
NO
Andre Oliveira
George Demetri
Antonio Perez-Atayde
Paola Dal Cin
Christopher Fletcher
Mark Gebhardt
Cynthia Morton
Sam Singer
Andrew Rosenberg
Marisa Nucci
Anette Duensing
Chang-Jie Chen
Nora Joseph
Bryna Mcconarty
Felicity Smith
Lynn Yu
Christopher Hubert
Maureen Thyne
Vicki Derr
Stana Weremowicz
Julia Bridge
THANK YOU!!!