Association with <i>TP53</i> codon 72 polymorphism and the risk of non‐Hodgkin lymphoma
Authors: Hee Nam Kim, Li Yu, Nan Young Kim, Il‐Kwon Lee, Yeo‐Kyeoung Kim, Deok‐Hwan Yang, Je‐Jung Lee, Min–Ho Shin, Kyeong‐Soo Park, Jin‐Su Choi, Hyeoung‐Joon Kim
Journal: American Journal of Hematology (2010)

Polymorphism of TP53 Arg72Pro is associated with many different cancers [1-4]. Few studies have investigated its role in the susceptibility to non-Hodgkin lymphoma (NHL) [5, 6]. To examine the association between this polymorphism and NHL risk, we conducted a Korean large-scale, population-based case–control study (945 cases and 1,700 controls). The TP53 72 CC genotype was associated with increased risk of NHL (P = 0.04) and diffuse large B-cell lymphoma (P = 0.04). Our findings provide evidence that the TP53 Arg72Pro is associated with an increased risk of NHL in Korea. TP53 is a well-known tumor suppressor gene, encoding p53, which plays a critical role in diverse cellular stresses to regulate target genes inducing cell-cycle arrest, apoptosis, senescence, DNA repair, or changes via the complex signal transduction network known as the p53 pathway [7, 8]. The TP53 gene is the most commonly mutated gene in human malignancies [9, 10], and loss of TP53 function because of damage to its DNA-binding and transcription factor function contributes to the progression of cancer. TP53 mutations are reported to be associated with risks of various cancers [11, 12]. The most common single nucleotide polymorphism (G412C, rs1042522) at codon 72 of exon 4, an arginine (Arg; CGC) to a proline (Pro; CCC) substitution, appears to alter the structure and biochemical function of the product [13, 14]. The G allele (Arg variant) induces more apoptosis efficiently, increases the localization of mitochondria, and induces the release of cytochrome c into the cytosol when compared with the C allele [15], whereas the C allele (Pro variant) appears to induce a higher level of G1 arrest [16]. This TP53 Arg72Pro polymorphism has been associated with risk factor for many different cancers [1-4]. In this study, we evaluated the distribution of the TP53 codon 72 genotypes in a Korean large-scale, population-based case–control study to identify whether this polymorphism alters the risks of non-Hodgkin lymphoma (NHL) and diffuse large B-cell lymphoma (DLBCL). To our knowledge, this is the largest study to investigate the effect of the TP53 polymorphism on lymphomagenesis. The genotype distributions among NHL cases and controls for the TP53 Pro72Arg polymorphism are shown in Table I. The genotype frequency in the controls was in Hardy–Weinberg equilibrium (P = 0.553) and was not significantly different between men and women (P = 0.891). CC and the combined GC or CC genotypes were associated with increased risks of NHL [odds ratio (OR)CC = 1.32, 95% confidence interval (CI) = 1.02–1.72; ORGC or CC = 1.21, 95% CI = 1.02–1.42] and DLBCL (ORCC = 1.41, CI = 1.02–1.96). The C allele was also associated with increased risks of NHL (OR = 1.15, CI = 1.02–1.30) and DLBCL (OR = 1.18, CI = 1.01–1.37). A few association studies have examined this polymorphism and hematological malignancies, including NHL [5, 6], acute myeloid leukemia [17-19], chronic myelogenous leukemia [20], and chronic lymphocytic leukemia [21] when compared with various solid tumors [22, 23]. The associations between this polymorphism and cancer risk are controversial [24]. The C allele induces less apoptosis and a higher level of G1 arrest than the G allele [15, 16]; therefore, failure in DNA repair leads to genomic instability, which has plausible a role in carcinogenesis. In agreement with this hypothesis, our findings showed that the C allele is associated with increased risks of NHL and DLBCL and is similar to previous reports on the risks of NHL [5]. Conversely, no association was found this polymorphism and the risk of adult T-cell leukemia/lymphoma [6]. Some studies have shown a strong association between TP53 mutations and the incidence, inferior overall survival, and resistance to chemotherapy despite the very low frequency of p53 mutations in hematological malignancy [25, 26]. The C allele of the TP53 codon 72 also might be more effectively correlated with lymphomagenesis. The difference between previous studies and our results may be due to different genotype frequencies for polymorphisms in different ethnic groups, different lymphoma subtypes, and differences in sample sizes. In conclusion, this large-scale, population-based study showed that TP53 codon 72 C allele plays a role in an increased risk of NHL. Further, large population-based studies in various geographical areas should be conducted to confirm the role of TP53 codon 72 C allele in lymphomagenesis. The study population consisted of 945 NHL patients and 1,700 population-based controls. The patients enrolled in the study were adults (median age, 58 years, range, 14–89 years) who had been diagnosed histologically with NHL at Chonnam National University Hwasun Hospital in Hwasun, Korea, between 1997 and 2009. The blood specimens of NHL cases were collected at diagnosis. The subtypes of NHL were defined according to the World Health Organization classification [27]. The NHL cases included 494 patients with DLBCL, 182 patients with T-cell lymphoma, and 269 with other lymphomas. The 182 cases of T-cell lymphoma included peripheral T-cell lymphoma-unspecified, extranodal natural killer cell/T-cell lymphoma, anaplastic large cell lymphoma, angioimmunoblastic T-cell lymphoma, T-cell type lymphoblastic lymphoma, and cutaneous T-cell NHL. The 268 cases of other lymphomas included all other subtypes, including follicular lymphoma. The control group (n = 1,700) consisted of participants in the Thyroid Disease Prevalence Study conducted from July 2004 to January 2006 in the Yeonggwang and Muan counties of Jeollanam-do Province and in Namwon City of Jeollabuk-do province, Korea [28]. At the time of peripheral blood collection, all case and control subjects provided their informed consent to participate in this study. This study was approved by the Institutional Review Board of the Chonnam National University Hwasun Hospital in Hwasun, Korea. Genomic DNA was extracted from peripheral blood using a QIAamp DNA Blood Mini Kit (QIAGEN, Valencia, CA), according to the manufacturer's protocol. The genotyping for TP53 Arg72 Pro was performed using a TaqMan allelic discrimination assay in a real-time PCR assay. The PCR primers and probes were designed and synthesized by Sigma (Sigma-Proligo, The Woodlands, TX). The PCR primers producing a 122-bp amplicon were as follows: 5′-TCCA GATGAAGCTCCCAGAATG-3′ and 5′-GGGAAGGGACAGAAGATGACAG-3′. The dual-labeled probes were 5′-FAM-CTGCTCCCCCCGTGGCCCC-BHQ1- 3′ for the C allele and 5′-HEX-CTGCTCCCCGCGTGGCCCC-BHQ2-3′ for the G allele. Real-time PCR was performed using a Rotor-Gene 6000 multiplex system (Corbett Research, Sydney, Australia) in 10 μL reaction volumes with 200 nM PCR primer (Bioneer, Daejeon, Korea), 100 nM probe, 0.5 U f-Taq polymerase (SolGent, Daejeon, Korea), and 40 ng genomic DNA. The genotyping by a TaqMan allelic discrimination assay was confirmed by direct sequencing reactions of 36 independent samples. The genotypes between assays were 100% concordant. The statistical significance of the differences between the patient and control groups was estimated by logistic regression analysis. The expected frequency of the control genotypes was checked using the Hardy–Weinberg equilibrium test. The adjusted ORs and their 95% CIs were calculated using logistic regression models after adjusting for age and sex to estimate the association between each genotype and NHL. All analyses were performed using SPSS software version 11.0 (SPSS, Chicago, IL). Hee Nam Kim*, Li Yu*, Nan Young Kim*, Il-Kwon Lee*, Yeo-Kyeoung Kim , Deok-Hwan Yang , Je-Jung Lee , Min–Ho Shin , Kyeong-Soo Park§, Jin-Su Choi , Hyeoung-Joon Kim* , * Genome Research Center for Hematopoietic Diseases, Chonnam National University Hwasun Hospital, Jeollanamdo, Korea, Department of Hematology/Oncology, Chonnam National University Hwasun Hospital, Jeollanamdo, Korea, Department of Preventive Medicine, Chonnam National University Medical School, Gwangju, Korea, § Department of Preventive Medicine, College of Medicine, Seonam University, Namwon, Korea.