2
Basic Cytogenetics and the Role of Genetics in Cancer Development
Fig. 2.4 G banded karyotype showing
a t(9;22)(q34;q11) translocation
corresponding to the so-called F
’hiladelphia (ph)
chromosome. Arrows indicate the derivative
chromosomes 9 and 22 involved in the
translocation.
Different types of probes, including the centromeric, the locus
specific, and the whole chromosome probes, are described:
• Centromeric probes are the most sensitive. They bind
to highly repetitive juxtacentromeric heterochromatin.
Their strong signal remains very easily detectable on
tissue sections. They are preferentially used for detect-
ing gains and losses of entire chromosomes, namely
aneusomies.
• Locus-specific probes are designed to detect unique
sequences spanning specific genomic loci. They are
used to detect specific gene amplifications, duplica-
tions, deletions, or chromosomal translocations. These
latter can be revealed by fusion of colors with the use
of dual-colour probes flanking chromosomal break-
points involved in translocations.
• Whole chromosome probes, known as chromo-
some painting, reveal the whole chromosome except
the centromeric region. They are used to identify
the origin of chromosomal markers such as ring
chromosomes and to refine complex chromosomal
translocations.
In congenital diseases, the use of probes has advantageously
circumvented the metaphase search for frequent trisomies or
microdeletion syndromes. Although banding analysis remains
the standard for identifying acquired chromosome abnor-
malities in cancer, FISH is now used as an easy and reliable
technical substitute to search for well-documented specific
chromosomal abnormalities in metaphase or interphase cells.
Nowadays, FISH is used on a regular basis as a complementary
tool to conventional cytogenetics, justifying the term "molecu-
lar cytogenetics."
The FICTION Technique
Fluorescent immunophenotyping and interphase cytogenetics
as a tool for the investigation of neoplasms (FICTION) is a
combination of fluorescent immunophenotyping and in situ
hybridization, making it possible to study genetic abnormalities
Fig. 2.5 G-banding karyotype compared to the ideogram
according to
ISCN 1985.
in phenotypically selected cells.9 The technical principle and
main practical applications of this method will be discussed
later in this chapter. Suffice to say it is currently used to detect
recurrent chromosomal abnormalities in multiple myeloma at
diagnosis. This method may be applied to any type of tumor cell
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