The allele frequency and genotype distribution of the SULT1A1 Arg213His variant in newborns and adult individuals are shown in Table 2. Since a significant difference was observed between the two groups, they were grouped as normal controls (n = 200) for subsequent comparison with the colorectal cancer patient group. The genotype frequencies in newborns, adults and pooled controls followed the Hardy-Weinberg equilibrium. The overall allele frequency of the SULT1A1*His allele (0.37) was similar to that recorded in several Caucasian and African populations, as well as Caucasian, Chinese and African-American populations [19,20].
The allele frequencies and genotype distributions of patient and control groups are compared in Table 3. The frequency of the SULT1A1*His allele was significantly lower in the patient group than in the control group (0.27 vs. 0.37, respectively, p = 0.02). This was more pro­nounced in homozygotes [odds ratio (OR) 2.35, 95% confidence interval (CI) (1.0465<OR<5.3013)] than in heterozygotes [OR 1.52, 95% CI (0.9411<OR<2.4703)], indicating that this variant is transmitted as a recessive trait.
Analyses of different clinical, molecular and histo­pathological parameters showed that the negative association of the SULT1A1*His allele with CRC was primarily due to the lower frequency of this variant in female patients >60 years of age (Table 4). Other parameters [localization, Dukes’ stage, family history, microsatellite instability (MSI) status] did not influence the association between the SULT1A1*His allele and CRC in the patient group (p >0.05 in all comparisons).

Table 2. Allele frequency and genotype distribution of SULT1A1 Arg213His variant in the control group(s).

^a Arg®Arg vs. Arg®His + His®His.

^b Arg®Arg + Arg®His vs. His®His.

Table 3. Allele frequency and genotype distribution of SULT1A1 Arg213His in CRC patient and control groups

^a Arg®Arg vs. Arg®His + His®His.

^b Arg®Arg + Arg®His vs. His®His.

^a Arg®Arg vs. Arg®His + His®His.

^b Arg®Arg + Arg®His vs. His®His.