Table 2. Genotyping and distribution of p53 codon72 Arg>Pro polymorphism in NPC cases and healthy controls of north-eastern Indian populations.
| Genotype or allele | Case (n=70) | Control (n=70) | P-value | OR (95% CI) |
|---|---|---|---|---|
| Genotype | ||||
| ArgArg | 14 (20) | 34 (48.57) | 1 | Ref. |
| ArgPro | 33 (47.14) | 20 (28.57) | 0.03 | 0.39 (0.18–0.97) |
| ProPro | 23 (32.86) | 16 (22.86) | 0.008 | 0.28 (0.11–0.69) |
| Allele | ||||
| Arg | 61 (43.57) | 88 (62.86) | 1 | Ref. |
| Pro | 79 (56.43) | 52 (37.14) | 0.001 | 0.45 (0.28–0.73) |
Abbreviations: CI, 95% confidence interval; OR, odds ratio. Data are number (%) of participants unless otherwisespecified. For genotyping, blood samples collected from each individual were processed and genomic DNA was extracted using the GenElute Blood Genomic DNA Kit (Sigma, St Louis, MO, USA; cat no. NA2020). PCR for genotyping of p53 codon72 Arg>Pro polymorphisms was performed as described earlier.50 Primers were obtained from Integrated DNA Technologies (Coralville, IA, USA): one pair of primers (p53 codon72 Arg Forward: TCC CCC TTG CCG TCC CAA; P53 codon72 Arg Reverse: CTG GTG CAG GGG CCA CGC) specific for the Arg allele and the other pair (p53 codon72 Pro Forward: GCC AGA GGC TGC TCC CCC, p53 codon72 Pro Reverse: CGT GCA AGT CAC AGA CTT) for the Pro allele. PCR was performed using a PCR amplification kit (cat no. RO11; TaKaRa, Shiga, Japan) with the following reaction conditions: genomic DNA extracted from blood was amplified in a PCR reaction containing 1 × PCR buffer, 200 μm of each dNTP, 10 pmole of each primer and 0.5 unit of Taq polymerase in a final volume of 20 μl. The detection of the two polymorphic variants was carried out in two separate tubes. The amplification was performed as follows: initial denaturation at 94 °C for 3 min, amplification for 35 cycles at 94 °C for 30 s, at 60 °C for the Arg allele and at 54 °C for the Pro allele for 30 s, extension at 72 °C for 30 s, followed by a final extension at 72 °C for 5 min. The PCR product obtained was 141 bp for the Arg allele and 177 bp for the Pro allele. Heterozygous samples showed the presence of both PCR products, whereas homozygous samples exhibited only one of the two products. In each PCR reaction one blank sample containing water in place of genomic DNA was taken as the negative control. Fisher's exact test was used to examine the distribution of allele and genotype frequencies among NPC patients and healthy controls.51