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TP53 gene R72P polymorphism analysis in patients with Barrett esophagus
Cancer Genetics and Cytogenetics 170 (2006) 76e77
Letter to the editor
TP53 gene R72P polymorphism analysis in patients with Barrett esophagus At least 20 polymorphisms have been described in the TP53 gene, both in coding and noncoding regions [1]. Among these, the R72P, encoding arginine (CGC) and proline (CCC) alleles, appear to be functionally equivalent [1]. The R72P polymorphism has been extensively studied with regard to its involvement in increased risk for cancer development, but results have been inconsistent [2e5]. Our study aimed to estimate the frequency of R72P polymorphism in control individuals, who represent the population of Porto Alegre, and in individuals with Barrett esophagus from the southernmost region of Brazil. The analysis of blood and tissue obtained from the same individuals allowed us to check for the existence of loss of heterozygosity in this region of the gene. Eighty unidentified controls were obtained from the Blood Bank of the Hospital de Clı´nicas of Porto Alegre and 23 individuals diagnosed with Barrett esophagus, confirmed by elective upper digestive endoscopy and biopsy. Amplification of exon 4 of the TP53 gene was carried out with a polymerase chain reaction (PCR) technique. The PCR product was then digested with 10U of AccII restriction enzyme. The statistical analysis of results was performed by Pearson’s chi-square method in the EPI-INFO 6.1 software. In the statistical analysis, the genotype frequency found in controls and BE patients was not significantly different ( p Z 0.7208). The analysis of frequency of arginine and proline alleles in controls and BE patients did not show significant differences either ( p Z 0.8103). In the loss of heterozygosity (LOH) study, only one case (8.33% of the sample) presented a homozygous pattern in the tissue. The individual who presented LOH in the tissue had a transition from heterozygosity to homozygosity for the proline allele. We have also observed that 4 of the 11 individuals homozygous for proline (n Z 2) or arginine (n Z 9) in their blood cells presented a heterozygous pattern in the tissue (22.2%), indicating the ‘‘gain’’ of an allele and suggesting the presence of genomic instability in this region. Soulitzis et al. [2] published the first study correlating TP53 codon 72 polymorphism with bladder cancer, providing evidence that this polymorphism is implicated in bladder carcinogenesis. The Arg/Arg genotype has an increased 0165-4608/06/$ e see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2006.03.017
risk of developing this kind of cancer. Apparently, however, there are no reports relating this polymorphism to Barrett esophagus. In the other hand, Guimaraes et al. [6] indicated that the most common allele in central China is the one encoding proline, in contrast to the majority of the populations tested to-date. These results indicate that polymorphism at codon 72 in TP53 is not associated with risk of esophageal cancer, even when associated with HPV infection. In our study, it was not possible to correlate the genotype frequencies and arginine and proline alleles with increased predisposition to Barrett esophagus. In the case of instability in the individual homozygous for proline in DNA extracted from blood cells, who presented a heterozygous pattern in the tissue, we can affirm that this individual replaced proline (CCC) with arginine (CGC), for this would be the only alternative through which the restriction enzyme would recognize the cleavage site. For the individual homozygous for blood cell arginine but heterozygous for tissue arginine, however, we do not know if the allele was actually replaced with proline. Any alteration in the cleavage site may have occurred, thus preventing recognition by restriction enzyme AccII. However, the alteration can only be confirmed by sequencing the individuals under consideration. Sandra Leistner-Segal Ana Paula Bohn Kaspary Patrı´cia Lopez Molecular Genetics Laboratory Medical Genetics Service Hospital de Clı´nicas de Porto Alegre RS, Brazil Diogo Andre´ Pilger Postgraduate Program in Medical Sciences Faculty of Medicine of the Federal University of Rio Grande do Sul Brazil Fa´bio Segal Institute of the Digestive Tract Instituto do Aparelho Digestiv e IAD Brazil
Letter to the editor / Cancer Genetics and Cytogenetics 170 (2006) 76e77
References [1] IARC Homepage. International Agency for Research no Cancer. p53 polymorphisms. Available at: http://www.iarc.fr/p53/index.html. Accessed April 22, 2005. [2] Soulitzis N, Sourvinos G, Dokianakis DN, Spandidos DA. p53 codon 72 polymorphism and its association with bladder cancer. Cancer Lett 2002;179:175e83. [3] Malcolm EK, Baber GB, Boyd James C, Stoler MH. Polymorphism at codon 72 of p53 is not associated with cervical cancer risk. Mod Pathol 2000;13:373e8.
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[4] Gottschlich S, Maune S, Preugschat J, Hoffmann M, Werner JA, Maass JD, Gorogh T, Heidorn K, Rudert H. p53 analysis of laryngeal cancer in exons 4 to 9. Anticancer Res 2000;20:2613e6. [5] Nakano Y, Naoe T, Kiyoi H, Kunishima S, Minami S, Miyawaki S, Asou N, Kuriyama K, Saito H, Ohno R. Poor clinical significance of p53 gene polymorphism in acute myeloid leukemia. Leuk Res 2000;24:349e52. [6] Guimaraes DP, Lu SH, Snijders P, Wilmotte R, Herrero R, Lenoir G, Montesano R, Meijer CJLM, Walboomers J, Hainaut P. Absence of association between HPV DNA, TP53 codon 72 polymorphism, and risk of oesophageal cancer in a high-risk area of China. Cancer Lett 2001;162:231e5.
Letter to the editor
TP53 gene R72P polymorphism analysis in patients with Barrett esophagus At least 20 polymorphisms have been described in the TP53 gene, both in coding and noncoding regions [1]. Among these, the R72P, encoding arginine (CGC) and proline (CCC) alleles, appear to be functionally equivalent [1]. The R72P polymorphism has been extensively studied with regard to its involvement in increased risk for cancer development, but results have been inconsistent [2e5]. Our study aimed to estimate the frequency of R72P polymorphism in control individuals, who represent the population of Porto Alegre, and in individuals with Barrett esophagus from the southernmost region of Brazil. The analysis of blood and tissue obtained from the same individuals allowed us to check for the existence of loss of heterozygosity in this region of the gene. Eighty unidentified controls were obtained from the Blood Bank of the Hospital de Clı´nicas of Porto Alegre and 23 individuals diagnosed with Barrett esophagus, confirmed by elective upper digestive endoscopy and biopsy. Amplification of exon 4 of the TP53 gene was carried out with a polymerase chain reaction (PCR) technique. The PCR product was then digested with 10U of AccII restriction enzyme. The statistical analysis of results was performed by Pearson’s chi-square method in the EPI-INFO 6.1 software. In the statistical analysis, the genotype frequency found in controls and BE patients was not significantly different ( p Z 0.7208). The analysis of frequency of arginine and proline alleles in controls and BE patients did not show significant differences either ( p Z 0.8103). In the loss of heterozygosity (LOH) study, only one case (8.33% of the sample) presented a homozygous pattern in the tissue. The individual who presented LOH in the tissue had a transition from heterozygosity to homozygosity for the proline allele. We have also observed that 4 of the 11 individuals homozygous for proline (n Z 2) or arginine (n Z 9) in their blood cells presented a heterozygous pattern in the tissue (22.2%), indicating the ‘‘gain’’ of an allele and suggesting the presence of genomic instability in this region. Soulitzis et al. [2] published the first study correlating TP53 codon 72 polymorphism with bladder cancer, providing evidence that this polymorphism is implicated in bladder carcinogenesis. The Arg/Arg genotype has an increased 0165-4608/06/$ e see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.cancergencyto.2006.03.017
risk of developing this kind of cancer. Apparently, however, there are no reports relating this polymorphism to Barrett esophagus. In the other hand, Guimaraes et al. [6] indicated that the most common allele in central China is the one encoding proline, in contrast to the majority of the populations tested to-date. These results indicate that polymorphism at codon 72 in TP53 is not associated with risk of esophageal cancer, even when associated with HPV infection. In our study, it was not possible to correlate the genotype frequencies and arginine and proline alleles with increased predisposition to Barrett esophagus. In the case of instability in the individual homozygous for proline in DNA extracted from blood cells, who presented a heterozygous pattern in the tissue, we can affirm that this individual replaced proline (CCC) with arginine (CGC), for this would be the only alternative through which the restriction enzyme would recognize the cleavage site. For the individual homozygous for blood cell arginine but heterozygous for tissue arginine, however, we do not know if the allele was actually replaced with proline. Any alteration in the cleavage site may have occurred, thus preventing recognition by restriction enzyme AccII. However, the alteration can only be confirmed by sequencing the individuals under consideration. Sandra Leistner-Segal Ana Paula Bohn Kaspary Patrı´cia Lopez Molecular Genetics Laboratory Medical Genetics Service Hospital de Clı´nicas de Porto Alegre RS, Brazil Diogo Andre´ Pilger Postgraduate Program in Medical Sciences Faculty of Medicine of the Federal University of Rio Grande do Sul Brazil Fa´bio Segal Institute of the Digestive Tract Instituto do Aparelho Digestiv e IAD Brazil
Letter to the editor / Cancer Genetics and Cytogenetics 170 (2006) 76e77
References [1] IARC Homepage. International Agency for Research no Cancer. p53 polymorphisms. Available at: http://www.iarc.fr/p53/index.html. Accessed April 22, 2005. [2] Soulitzis N, Sourvinos G, Dokianakis DN, Spandidos DA. p53 codon 72 polymorphism and its association with bladder cancer. Cancer Lett 2002;179:175e83. [3] Malcolm EK, Baber GB, Boyd James C, Stoler MH. Polymorphism at codon 72 of p53 is not associated with cervical cancer risk. Mod Pathol 2000;13:373e8.
77
[4] Gottschlich S, Maune S, Preugschat J, Hoffmann M, Werner JA, Maass JD, Gorogh T, Heidorn K, Rudert H. p53 analysis of laryngeal cancer in exons 4 to 9. Anticancer Res 2000;20:2613e6. [5] Nakano Y, Naoe T, Kiyoi H, Kunishima S, Minami S, Miyawaki S, Asou N, Kuriyama K, Saito H, Ohno R. Poor clinical significance of p53 gene polymorphism in acute myeloid leukemia. Leuk Res 2000;24:349e52. [6] Guimaraes DP, Lu SH, Snijders P, Wilmotte R, Herrero R, Lenoir G, Montesano R, Meijer CJLM, Walboomers J, Hainaut P. Absence of association between HPV DNA, TP53 codon 72 polymorphism, and risk of oesophageal cancer in a high-risk area of China. Cancer Lett 2001;162:231e5.