A haplotype variation affecting the mitochondrial transportation of hMYH protein could be a risk factor for colorectal cancer in Chinese.
BACKGROUND
The human MutY homolog (hMYH), a DNA glycolsylase involved in the excision repair of oxidative DNA damage, is currently studied in colorectal cancer (CRC). We previously demonstrated a haplotype variant c.53C>T/c.74G>A of hMYH (T/A) increasing the risk for gastric cancer in Chinese. However, most investigations on correlation between hMYH and CRC are conducted in Western countries and the underlying mechanism has been poorly understood.


METHODS
To determine whether the haplotype T/A variant of hMYH was related to colorectal carcinogenesis, we performed a case-control study in 138 colorectal cancer (CRC) patients and 343 healthy controls in a Chinese population. Furthermore, the C/G for wild-type, C/A or T/G for single base variant and T/A for haplotype variant hMYH cDNAs with a flag epitope tag were cloned into pcDNA3.1+ vector and transfected into cos-7 cell line. Their subcellular localizations were determined by immunofluorescence assay.


RESULTS
It was found that the frequency of haplotype variant allele was statistically higher in CRC patients than that in controls (P = 0.02, odds ratio = 5.06, 95% confidence interval = 1.26 - 20.4). Similarly, significant difference of heterozygote frequency was indicated between the two groups (P = 0.019), while no homozygote was found. In addition, immunofluorescence analysis showed that hMYH protein with haplotype T/A variation presented in both nucleus and mitochondria, in contrast to the wild-type protein only converging in mitochondria. However, neither of the single missense mutations alone changed the protein subcelluar localization.


CONCLUSIONS
Although preliminarily, these results suggest that: the haplotype variant allele of hMYH leads to a missense protein, which partly affects the protein mitochondrial transportation and results as nuclear localization. This observation might be responsible for the increased susceptibility to cancers, including CRC, in Chinese.
Chen
Huimei
H
Department of Medical Genetics, Medical School, Nanjing University, Nanjing, PR China. chenhuimei@nju.edu.cn
Xu
Lizhi
L
Qi
Qiufeng
Q
Yao
Yanweng
Y
Zhu
Ming
M
Wang
Yaping
Y
D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D001483:Base Sequence; D002277:Carcinoma / Q000235:genetics* / Q000378:metabolism; D002681:China; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D045647:DNA Glycosylases / Q000235:genetics* / Q000378:metabolism*; D004252:DNA Mutational Analysis; D005260:Female; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D006801:Humans; D008297:Male; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism*; D020641:Polymorphism, Single Nucleotide / Q000502:physiology; D021381:Protein Transport / Q000235:genetics; D012307:Risk Factors
D045647:DNA Glycosylases; C061738:mutY adenine glycosylase