K. Obara et al., Evaluation of myc and chromosome 8 copy number in colorectal cancer using interphase cytogenetics, INT J ONCOL, 18(2), 2001, pp. 233-239
To reveal the significance of genetic abnormalities of the c-myc gene, 56 c
olorectal tumors (43 colorectal carcinomas, 5 recurrent or metastatic tumor
s, and 8 adenomatous polyps) were analyzed using fluorescence in situ hybri
dization (FISH). Two probes specific for c-myc and the chromosome 8 centrom
ere were used for dual color FISH. In each case, 100-200 nuclei were observ
ed for signals from the probes. The percent of nuclei with c-myc amplificat
ion (PMA) was defined as the proportion of nuclei representing the ratio of
c-myc/chromosome 8 >1.0, and the percent of nuclei with the greater number
of c-myc (PGNM) was defined as the proportion of nuclei representing the r
atio of c-myc/chromosome 8 greater than or equal to2.0. Low level amplifica
tion was defined as a case with PMA greater than or equal to 10% and PGNM <
10%. High level amplification was defined as a case with PGNM <greater than
or equal to>10%. While adenomatous polyps and in situ carcinomas showed no
c-myc amplification, the low level amplification and high level amplificat
ion of c-myc were observed in 48.8% (21/43) and 20.9% (9/43) of primary col
orectal carcinomas. In addition, the group including cases of stage IIIb an
d IV exhibited significantly higher average copy numbers of c-myc (CN-myc),
PMA and PGNM than the other group of earlier stages. FISH was thought a us
eful cytogenetic method to detect genetic abnormalities in solid tumors. It
was shown that the c-myc gene amplification identified using FISH was asso
ciated with the aggressiveness of colorectal carcinoma.