Two novel germline mutations of MLH1 and investigation of their pathobiology in hereditary non-polyposis colorectal cancer families in China.
OBJECTIVE
To detect germline mutations of MLH1, and investigate microsatellite instability and expression of MLH1 in tumor tissues of hereditary non-polyposis colorectal cancer (HNPCC) with two novel germline mutations, and further investigate the pathobiology of the two novel mutations of MLH1.


METHODS
RNA was extracted from the peripheral blood of 12 patients from 12 different families that fulfilled the Amsterdam II Criteria for HNPCC. Germline mutations of MLH1 were determined by RT-PCR, followed by cDNA sequencing analysis. PCR-GeneScan analysis was used to investigate microsatellite instability with a panel of five microsatellite markers (BAT26, BAT25, D5S346, D2S123 and mfd15), along with immunohistochemical staining to detect the expression of MLH1 protein in two patients' tumor tissues with novel mutations.


RESULTS
Three germline mutations were found in four patients, one of the mutations has previously been reported, but the other two, CGC right arrow TGC at codon 217 of exon 8 and CCG right arrow CTG at codon 581 of exon 16, have not been reported. The two patients' tumor tissues with novel mutations had high-frequency microsatellite instability that showed more than two unstable loci, and both tumors lost their MLH1 protein expression.


CONCLUSIONS
The two novel germline mutations of MLH1 in HNPCC families i.e. CGC right arrow TGC at codon 217 of exon 8 and CCG right arrow CTG at codon 581 of exon 16, are very likely to have pathological significance.
Wang
Chao-Fu
CF
Department of Pathology, Cancer Hospital of Fudan University, 270 Dongan Road, Shanghai 200032, China.
Zhou
Xiao-Yan
XY
Zhang
Tai-Ming
TM
Xu
Ye
Y
Cai
San-Jun
SJ
Shi
Da-Ren
DR
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000328:Adult; D044466:Asian People / Q000208:ethnology* / Q000235:genetics*; D002681:China; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000208:ethnology* / Q000235:genetics* / Q000473:pathology; D018076:DNA, Complementary / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D018095:Germ-Line Mutation / Q000235:genetics*; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics*; D012313:RNA / Q000235:genetics; D017422:Sequence Analysis, DNA
D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D012313:RNA; D000070957:MutL Protein Homolog 1