Lysyl Oxidase Gene G473A Polymorphism and Cigarette Smoking in Association with a High Risk of Lung and Colorectal Cancers in a North Chinese Population

Abstract

The relationship among the lysyl oxidase (LOX) G473A single nucleotide polymorphism (SNP), cigarette smoking and lung, colorectal, colon and rectum cancer susceptibility was studied in 200 cases of lung cancer, 335 cases of colorectal cancer including 130 cases of colon cancer and 205 cases of rectum cancer, and 335 healthy people in Tangshan, China. Peripheral blood DNA samples were collected, DNA sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) performed, followed by multivariate logistic regression analysis. In comparison to LOX473GG genotype carriers, individuals with LOX473AA exhibited a higher susceptibility to lung, colon-rectum, colon, and rectum cancers with OR values amounting to 3.84-, 2.74-, 2.75-, and 2.74-fold of the control, respectively. In the LOX 473AA-positive population, females were more susceptible than males to carcinogenesis with OR values (female vs. male): 5.25 vs. 3.23, 2.29 vs. 1.51, 2.27 vs. 1.45, and 2.25 vs. 1.53, respectively, for lung, colon-rectum combined, colon, and rectum cancers. LOX G473A polymorphism apparently elevated human sensitivity to cigarette smoking carcinogens for eliciting cancers in the lung and colon only. Thus, LOX G473A polymorphism positively correlates with carcinogenesis and it may be used as an ideal intrinsic biomarker for prediction or diagnosis of carcinogenesis in humans.

Keywords: cigarette smoking; colon cancer; colorectal cancer; lung cancer; lysyl oxidase (LOX); rectal cancer; single nucleotide polymorphism (SNP).

Figure 1

Gene sequence assay indicating LOX G473A polymorphism. GG, the homozygous GG genotype; GA, the heterozygous GA genotype; AA, the homozygous AA genotype. Three genotypes: GG, a black wave in (A); GA, a short black wave overlaid with a shorter green wave in (B); and AA, a green wave in (C) are marked by *.

Figure 1

Gene sequence assay indicating LOX G473A polymorphism. GG, the homozygous GG genotype; GA, the heterozygous GA genotype; AA, the homozygous AA genotype. Three genotypes: GG, a black wave in (A); GA, a short black wave overlaid with a shorter green wave in (B); and AA, a green wave in (C) are marked by *.

Figure 2

PCR- restriction fragment length polymorphism (PCR-RFLP) analysis for LOX G473A. Total DNA was extracted from the blood sample followed by PCR-amplification using the primers as shown in the text. The PCR product with 214 bp was treated with a specific restriction endonuclease Not I with the CG site targeting and analyzed on a 2% agarose gel, stained with ethidium bromide for visualization under ultraviolet light. After electrophoresis, homozygous G alleles which contain the CG site were recognized by DNA bands at 100 and 114 bp in length. An uncut fragment of 214 bp indicated the homozygous A alleles free of the CG site and the heterozygous GA genotype was displayed as a combination of 214, 100, and 114 bp bands. Due to 114 bp and 100 bp DNA being close in the MW, they were smeared as one band in the gel electrophoresis.