T. Ikenoue et al., Frameshift mutations at mononucleotide repeats in RAD50 recombinational DNA repair gene in colorectal cancers with microsatellite instability, JPN J CANC, 92(6), 2001, pp. 587-591
To identify additional genes targeted for microsatellite instability (MSI),
we search for human genes which contain mononucleotide repeats in their co
ding region, selected 7 genes (RAD50, DNA-PKcs, FLASH, Apaf-1, XPG, CtIP, a
nd MLSN1), and analyzed frameshift mutations in them. Here we report that 6
0% (3 out of 5) of human colorectal cancer cell lines exhibiting a high fre
quency of MSI (MSI-H) and 46% (6 out of 13) of MSI-H primary colorectal tum
ors had mutations in the (A)9 repeat of RAD50 recombinational repair gene.
In contrast, no frameshift mutations were found in any of the 5 MSI-negativ
e colorectal cancer cell lines, 8 colorectal tumors exhibiting a low freque
ncy of MSI (MSI-L), or 28 MSI-negative colorectal tumors. No mutations were
found in the mononucleotide repeats of 6 other genes, even in MSI-H cancer
s. These results suggest that RAD50 frameshift mutations may play a role in
the tumorigenesis of MSI-H colorectal cancers.