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The
expression of p53 in different human
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cancers or in
tumor cell lines has long been
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under study by
several different
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investigators.
This expression is often high,
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but no precise
explanations exist for this
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phenomenon
because apart from the case of
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several
osteosarcomas, no gene
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rearrangements,
detectable by Southern
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blotting, have
been detected. Genetic
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analysis of
colorectal cancer reveals a very
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high rate of
heterozygous loss of the short
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arm of
chromosome 17, which carries the
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p53 gene
(Vogelstein et al. 1988). PCR
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analysis and
sequencing of the remaining
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p53 allele
shows that it often contains a
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point
mutation (Baker et al. 1989). Similar
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observations
have been made in the case of
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lung cancer
(Takahashi et al. 1989). On the
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heels of
these initial observations have come
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several
hundred reports of alterations of the
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p53 gene in
all types of human cancer (see
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below). In
many cases these mutations are
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accompanied
by a heterozygous loss of the
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short arm of
chromosome 17
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