Book of abstract 2008

Immunohistochemistry in oncology: a tool for diagnosis, prognosis and
treatment
Paule Opolon
CNRS UMR 8121, Institut Gustave-Roussy, Villejuif 94805, France
Immunohistochemistry enables the visualization of specific antigens tissue distribution.
It localizes protein targets of interest by applying specific monoclonal or polyclonal
antibodies to tissue surfaces in a process called antibody incubation. This technique was
developed since the 1940’s, when Coons and colleagues from Harvard Medical School
described the identification of tissue antigens by using a direct fluorescence protocol.
Detection of reliable fluorescent signals was initiated by pharmaceutical chemists, such
as Riggs, in 1961, who replaced the toxic and unstable compound isocyanate by a more
stable dye, fluorescein isothiocyanate (FITC). The first applications of this method were
bacteriology and the diagnosis of autoimmune diseases. The availability of numerous
specific monoclonal antibodies in the 1970’s provided major advances in pathology,
internal medicine and oncology. Immunohistoenzymology coupled with transmission
microscopy (vs immunofluorescence), is the elective method for many surgical pathologists
since it makes it possible to visualise at once signals and adjacent structures.
In the field of oncology, histological markers (which are not always correlated to seric
markers) allowed major advances in basic research and clinical science: for example
estrogen receptors detection on histological slides in breast cancer is a validated routine
tool for therapy. In fundamental research, visualisation of growth factors, cytokines,
apoptosis inhibitors, oncogenic proteins, hypoxia markers, endothelial cells and other cell
types involved in angiogenesis, combined with various methods, such as those derived
from molecular biology is a very valuable tool for the understanding of cancerogenesis
mechanisms.
However, interpretation of immunohistochemistry has to take into account the pitfalls
of this method: poor specificity of some antibodies, discrepancies between hospitals often
related to the
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heterogeneity of fixation procedures and, during many years, the drawback
of an exclusively morphological approach. Early adepts of quantification of these signals
spent longs hours counting manually histological structures such as blood vessels, with a
poor intra-observer and inter-observer reproducibility.
Since 2004, quantification of stained signals is performed at Gustave Roussy Institute in
Villejuif with a system combining a dedicated slide scanner and a computer-assisted image
analysis: PIXCYT is a software package designed by the Groupe Régional d’Etudes sur
le Cancer, Centre François Baclesse, Caen) and represents a revolutionary approach of
markers interpretation on histological slides for experimental pathology applications,
such as the count of immunostained microvessels, nuclear or cytoplasmic stainings in
tumor cells.
Automation with a dedicated script implemented to PIXCYT proved to be very helpful
for measurement of lung metastases surface in a model of B16F10 tumors xenografted
in nude mice. This software is also currently used to assess tumor microvessel density
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