Transcript Diapositiva 1

Evaluation of p16 expression in
Gastrointestinal Stromal Tumors (GIST):
A Tissue Microarray Study.
V. Mambelli, F. Corini, A. D’Angelo, A. Braccischi, L. Diamanti,
M. Del Vecchio, R. Taborro, R. Zamparese
U.O. Anatomia Patologica
Osp. C.G. Mazzoni
Ascoli Piceno
1
Genetics alterations involving p16 gene have been shown
to drive the patogenic development of GISTs, the most
common mesenchymal tumour of the gastrointestinal
tract. Losses on chromosome 14q and 22q are common
in borderline tumors, while additional losses on
chromosome 1p and 9p are overrepresented in malignant
lesions.
2
These losses often comprise 9p21 locus which contains the
clusters of ARF/INK4a gene.
9p21
locus
w
3
p16 is a tumor suppressor that inhibits cell cycling by arresting
cell in G1 before entry into S phase.
4
Genetics alterations results in diminished p16 levels, related
to proliferation and progression of cancer cells.
cancerous cell
normal cell
upregulation;
downregulation
5
Tissue MicroArrays (TMAs) are a relatively new innovation in
pathology.
Tissue Microarray Advantages
High throughput:
Uniform reaction conditions
Built-in controls
Economize use of reagents o
Facilitates data recording and linking to clinical
data
TMAs
represent
understanding
the
an
increasingly
clinical
impact
validated
of
means
of
diagnostic-related,
prognostic-related, and therapy-related markers..
6
7
The arrayed tissue cores are histologically guided samples
from representative regions of standard formalin-fixed
paraffin-embedded.
8
For TMA construction, tissue cylinders, 0.3 mm in diameter, were
punched from the marked tumor regions of each donor tissue block.
Tissue core punches were organized in four TMAs.
9
To overcome the problem of tissue variability, we replicated the
TMAs by punching the donor tissue blocks at least three times.
A
B
C
A
B
C
10
To validate our TMA data, we compared the
immunohistochemical staining results of p16 protein
on whole tissue sections of
10 cases found
completely concordance.
Full section
core 1
core 2
11
The studied group consisted of 31 cases of GISTs (14 gastric tumors,
14 small and large bowel tumors, 1 peritoneal tumor, 1 retroperitoneal
tumor and 1 duodenal tumor).
We observed p16 protein expression in 19 of 31 GISTs (61.2%).
x 40
x 40
x 20
x 20
12
Of 12 GISTs with loss of p16 expression, five GISTs (41.6%) were found
to have worse prognosis (death for disease)
x 20
x 40
13
A previuos study conducted on 284 cases of GISTs showed that
a negative p16 expression is more likely to be associated with
high-risk GISTs.
A recent Norway study conducted on 434 cases of GISTs showed
that a positive p16 phenotype is more likely to be associated with
malignant GISTs
14
Our results suggest that expression of p16 correlated significatly with
favorable prognosis.
However, we found strongly p16 expression in one GIST case with
higher mitotic counts.
Alternative changes in cell-cycle control could lead to a compensatory
upregolation of p16.
There was an excellent concordance of p16 evaluation between
conventional sections and TMAs.
This indicates that the TMA technology can be applied to highthroughput analysis of immunohistochemical expression studies.
15