No association between MDR1 (ABCB1) 2677G>T and 3435C>T polymorphism and sporadic colorectal cancer among Bulgarian patients.
OBJECTIVE
Variation in genetic factors together with xenobiotic exposure may result in increased risk of colorectal cancer. The P-glycoprotein (P-gp) is highly expressed in the apical membrane of enterocytes, where it pumps xenobiotics from the enterocytes back into the intestinal lumen. Thus, polymorphisms that reduce the activity of the MDR1 (ABCB1) efflux pump are potential risk factors for colorectal carcinogenesis. The aim of the present study is to genotype the MDR1 2677G>T (rs2032582) and 3435C>T (rs1045642) polymorphism in patients with colorectal cancer and controls and to identify a possible association between individual genetic variation and susceptibility to colorectal cancer.


METHODS
In the present study, 146 Bulgarian patients with sporadic colorectal cancer and 160 healthy Bulgarian volunteers were evaluated for the two polymorphisms in MDR1. Polymorphisms were identified using rapid-cycle real-time amplification with allele-specific probes and subsequent melting curve analyses on a LightCyclertrade mark (Roche Diagnostics, Mannheim, Germany).


RESULTS
No differences were found between the frequencies of the two mutant alleles in the tumor tissue from the cases and lymphocytes from the controls [frequencies of 2677T: 43.5% in patients and 44.1% in controls; frequencies of 3435T: 48.3% in patients and 50.9% in controls (both P > 0.05)]. The MDR1 polymorphic sequence of the tumor tissue always matched that of normal intestinal tissue from the same patient. Consequently, genotyping of DNA from archived tumor tissues is a valid alternative to the use of leukocyte DNA.


CONCLUSIONS
The present study suggests that MDR1 2677G>T and 3435C>T polymorphism is not a risk factor for sporadic colon cancer among Bulgarians and that somatic mutation at these sites is not involved in the genesis of colon tumors. Further examination using larger number of samples must be necessary to reach to more reliable conclusions.
Department of Medical Genetics, Medical University Sofia, 2, Zdrave Str., 1431 Sofia, Bulgaria. darinka_petrova@abv.bg
Darinka Todorova
DT
Petrova
Petya
P
Nedeva
Svilen
S
Maslyankov
Svetoslav
S
Toshev
Nikolay
N
Yaramov
Srebrena
S
Atanasova
Draga
D
Toncheva
Michael
M
Oellerich
Nicolas
N
von Ahsen
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D000368:Aged; D002031:Bulgaria; D015179:Colorectal Neoplasms / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D008297:Male; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D012307:Risk Factors
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1