Analysis of Ki-ras gene mutations associated with DNA diploid, aneuploid, and multiploid colorectal carcinomas using a crypt isolation technique.
OBJECTIVE
Current evidence suggests a possible relationship between DNA ploidy status and Ki-ras gene mutations in human cancers. However, the conventional method does not enable accurate determination of DNA ploidy status of a tumor cell. The present study attempts to clarify whether Ki-ras gene mutations are associated with DNA ploidy status in sporadic colorectal carcinomas using a crypt isolation technique coupled with DNA cytometric sorting.


METHODS
Polymerase chain reaction and single-strand conformation polymorphism and direct sequencing were used to analyze Ki-ras gene mutations in 82 sporadic colorectal carcinomas: 21 diploid, 12 aneuploid, and 49 multiploid. In addition, microsatellite instability (MSI) was assessed using seven microsatellite markers to study the relationship to Ki-ras mutations.


RESULTS
Ki-ras mutations were found in 12 of 21 diploid carcinomas and in 8 of 12 aneuploid carcinomas. In contrast, Ki-ras gene mutations were detected infrequently in the 34 multiploid carcinomas examined, 8 of which were seen in diploid populations and 10 in aneuploid populations. On the other hand, Ki-ras gene mutations were inversely correlated with MSI, which was found in diploid carcinomas only.


CONCLUSIONS
The low frequency of Ki-ras gene mutations that we observed in multiclonal colorectal carcinomas suggests that development of multiclonal colorectal carcinoma may involve a mechanism different from that involved in the development of diploid or aneuploid colorectal carcinomas.
Sugai
T
T
Division of Pathology, Central Clinical Laboratory, School of Medicine, Iwate Medical University, Morioka, Japan. tsugai@cocoa.ocn.ne.jp
Habano
W
W
Nakamura
S
S
Jiao
Y F
YF
Higuchi
T
T
Inomata
M
M
Chiba
T
T
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000782:Aneuploidy; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000648:ultrastructure; D004273:DNA, Neoplasm / Q000032:analysis* / Q000145:classification; D004171:Diploidy; D005260:Female; D005434:Flow Cytometry; D011905:Genes, ras; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D009154:Mutation; D011123:Polyploidy
D004273:DNA, Neoplasm