Automated, multiplex assay for high-frequency microsatellite instability in colorectal cancer.
OBJECTIVE
In a series of hereditary nonpolyposis colorectal cancer (HNPCC) patients, we evaluated the sensitivities of the individual microsatellites recommended by the National Cancer Institute (NCI) consensus workshop for detection of high-frequency microsatellite instability (MSI-H). On the basis of this evaluation, we developed a three-marker assay that assigns microsatellite instability (MSI) in a multiplex polymerase chain reaction.


METHODS
Individual marker sensitivity was assessed in 18 HNPCC tumors. Multiplex and NCI assays were then assessed in a series of 120 patients with early-onset colon cancer.


RESULTS
The sensitivity of microsatellite markers BAT25, BAT26, D2S123, D5S346, and D17S250 for ASI in HNPCC cancers was 100%, 94%, 72%, 50%, and 50%, respectively. The three most accurate markers were combined and optimized in a multiplex assay that assigned MSI-H whenever at least two of three markers revealed ASI. In early-onset colon cancers, the prevalence of MSI-H determined by the multiplex assay and by the NCI assay was 16% and 23%, respectively. The additional MSI-H tumors and patients with MSI-H identified by the NCI assay lacked the traits characteristic of MSI-H seen in tumors and patients identified by the multiplex assay: retention of heterozygosity (NCI additional 22% v multiplex 84%; P =.003), characteristic tumor morphology (0% v 64%; P =.006), and 5-year cancer survival rate (44% v 100%; P =.0003).


CONCLUSIONS
The multiplex assay identifies colon cancers with MSI-H by assessing three highly accurate microsatellite markers. This assay identifies a smaller MSI-H cohort with more homogeneous clinical features and is superior as a marker of favorable prognosis. It merits prospective evaluation as a marker of prognosis and as a screening test for HNPCC.
Nash
G M
GM
Department of Surgery, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10021, USA.
Gimbel
M
M
Shia
J
J
Culliford
A T
AT
Nathanson
D R
DR
Ndubuisi
M
M
Yamaguchi
Y
Y
Zeng
Z S
ZS
Barany
F
F
Paty
P B
PB
D000230:Adenocarcinoma / Q000235:genetics*; D002869:Chromosome Aberrations; D015179:Colorectal Neoplasms / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods*; D018572:Disease-Free Survival; D006801:Humans; D018895:Microsatellite Repeats; D008875:Middle Aged; D016133:Polymerase Chain Reaction