Irene Rodriguez-Hernandez

The human Tp53 Arg72Pro polymorphism explains different functional prognosis in stroke

Poor prognosis after ischemic stroke or intracerebral hemorrhage is linked to a particular polymorphism in the human gene encoding p53.

The p53 codon 72 polymorphism (rs1042522) is associated with proliferative vitreoretinopathy: the Retina 4 Project.

PURPOSE To compare the distribution of a p53 gene polymorphism among European subjects undergoing primary retinal detachment (RD) surgery in relation to the development of proliferative vitreoretinopathy (PVR). DESIGN Case-controlled gene association study conducted as a component of the Retina 4 Project (a European multicenter study). PARTICIPANTS AND CONTROLS Five hundred fifty DNA samples, 134 with PVR secondary to primary RD and 416 with RD without PVR. METHODS The p53 codon 72 polymorphism (rs1042522) was analyzed using allele-specific primer polymerase chain reaction. Proportions of genotypes and the proline (Pro-P) homozygote groups between subsamples from different countries were analyzed in 2 phases. In the first, subsamples from Spain and Portugal were analyzed. After significant results were found, samples from the United Kingdom (UK) and The Netherlands were analyzed (second phase). Genotypic and allelic frequencies were compared between cases and controls in the global sample. MAIN OUTCOME MEASURES Single significant associations with PVR. RESULTS A significant difference (P<0.05, Fisher exact test) was observed regarding the p53 genotype frequencies at codon 72 between the PVR cases and the non-PVR controls in Spain and Portugal (phase I), but not in the UK or The Netherlands (phase II). Analysis of Pro homozygote carriers between cases and controls revealed differences in Spain (29.01-42.18 and 2.29-10.20, respectively), Portugal (10.49-29.50 and 1.35-8.89, respectively), and The Netherlands (16.49-31.70 and 4.51-15.09, respectively), but no differences in the UK (7.68-18.1 and 4.85-13.94, respectively). The odds ratio of Pro carriers from Spain and Portugal together was 8.12 (95% confidence interval [CI], 3.72-17.69; P<0.05), whereas the odds ratio of Pro carriers from the UK and The Netherlands was 2.12 (95% CI, 0.96-4.68; P = 0.07). All control samples were in Hardy-Weinberg equilibrium. Considering the entire sample, significant differences were found in genotype frequencies between cases (RR, 30.59%; RP, 43.28%; PP, 26.11% [R = Arg; P = Pro]) and controls (RR, 39.66%; RP, 52.64%; PP, 7.69%) and in Pro homozygote carriers between controls (Pro homozygote 95% CI, 18.67-33.52) and cases (Pro homozygote 95% CI, 5.1-10.2). CONCLUSIONS Results indicate that the Pro variant of p53 codon 72 polymorphism is associated with a higher risk of PVR developing after a primary RD. Further studies are necessary to understand the role of this polymorphism in the development of PVR.

Analysis of DNA repair gene polymorphisms in glioblastoma

BACKGROUND Glioblastoma is the most common and aggressive primary brain tumor in adults. Despite several factors such as ionizing radiation exposure or rare genetic syndromes have been associated with the development of glioblastoma, no underlying cause has been identified for the majority of cases. We thus aimed to investigate the role of DNA repair polymorphisms in modulating glioblastoma risk. METHODS Genotypic and allelic frequencies of seven common polymorphisms in DNA repair genes involved in nucleotide excision repair (ERCC1 rs11615, ERCC2 rs13181, ERCC6 rs4253079), base excision repair (APEX1 rs1130409, XRCC1 rs25487), double-strand break repair (XRCC3 rs861539) and mismatch repair (MLH1 rs1800734) pathways were analyzed in 115 glioblastoma patients and 200 healthy controls. Haplotype analysis was also performed for ERCC1 rs11615 and ERCC2 rs13181 polymorphisms, located on the same chromosomal region (19q13.32). RESULTS Our results indicated that carriers of the ERCC2 Gln/Gln genotype were associated with a lower glioblastoma risk (OR=0.32, 95% CI 0.12-0.89; P=0.028), whereas carriers of the MLH1 AA genotype were associated with an increased risk of glioblastoma (OR=3.14, 95% CI 1.09-9.06; P=0.034). Furthermore, the haplotype containing the C allele of ERCC2 rs13181 polymorphism and the T allele of ERCC1 rs11615 polymorphism was significantly associated with a protective effect of developing glioblastoma (OR=0.34, 95% CI 0.16-0.71; P=0.004). CONCLUSIONS These results pointed out that MLH1 rs1800734 and ERCC2 rs13181 polymorphisms might constitute glioblastoma susceptibility factors, and also suggested that the chromosomal region 19q could be important in glioblastoma pathogenesis.

The T309G MDM2 gene polymorphism is a novel risk factor for proliferative vitreoretinopathy.

Proliferative vitreoretinopathy (PVR) is still the major cause of failure in retinal detachment (RD) surgery. It is believed that down-regulation in the p53 pathway could be an important key in PVR pathogenesis. The purpose was to evaluate the impact of T309G MDM2 polymorphism (rs2279744) in PVR. Distribution of T309G MDM2 genotypes among European subjects undergoing RD surgery was evaluated. Proportions of genotypes between subsamples from different countries were analyzed. Also, a genetic interaction between rs2279744 in MDM2 and rs1042522 in p53 gene was analyzed. Significant differences were observed comparing MDM2 genotype frequencies at position 309 of intron 1 between cases (GG: 21.6%, TG: 54.5%, TT: 23.8%) and controls (GG: 7.3%, TG: 43.9%, TT: 48.7%). The proportions of genotypes between sub-samples from different countries showed a significant difference. Distribution of GG genotype revealed differences in Spain (35.1–53.0)/(22.6–32.9), Portugal (39.0–74.4)/(21.4–38.9), Netherlands (40.6–66.3)/(25.3–38.8) and UK (37.5–62.4)/(23.3–34.2). The OR of G carriers in the global sample was 5.9 (95% CI: 3.2 to 11.2). The OR of G carriers from Spain and Portugal was 5.4 (95% CI: 2.2–12.7), whereas in the UK and the Netherlands was 7.3 (95% CI: 2.8–19.1). Results indicate that the G allele of rs2279744 is associated with a higher risk of developing PVR in patients undergoing a RD surgery. Further studies are necessary to understand the role of this SNP in the development of PVR.

Integrated Analysis of Mismatch Repair System in Malignant Astrocytomas

Malignant astrocytomas are the most aggressive primary brain tumors with a poor prognosis despite optimal treatment. Dysfunction of mismatch repair (MMR) system accelerates the accumulation of mutations throughout the genome causing uncontrolled cell growth. The aim of this study was to characterize the MMR system defects that could be involved in malignant astrocytoma pathogenesis. We analyzed protein expression and promoter methylation of MLH1, MSH2 and MSH6 as well as microsatellite instability (MSI) and MMR gene mutations in a set of 96 low- and high-grade astrocytomas. Forty-one astrocytomas failed to express at least one MMR protein. Loss of MSH2 expression was more frequent in low-grade astrocytomas. Loss of MLH1 expression was associated with MLH1 promoter hypermethylation and MLH1 -93G>A promoter polymorphism. However, MSI was not related with MMR protein expression and only 5% of tumors were MSI-High. Furthermore, the incidence of tumors carrying germline mutations in MMR genes was low and only one glioblastoma was associated with Lynch syndrome. Interestingly, survival analysis identified that tumors lacking MSH6 expression presented longer overall survival in high-grade astrocytoma patients treated only with radiotherapy while MSH6 expression did not modify the prognosis of those patients treated with both radiotherapy and chemotherapy. Our findings suggest that MMR system alterations are a frequent event in malignant astrocytomas and might help to define a subgroup of patients with different outcome.

BAX and BCL-2 polymorphisms, as predictors of proliferative vitreoretinopathy development in patients suffering retinal detachment: the Retina 4 project.

To compare the distribution of BCL‐2 ‐938C>A (rs2279115) and BAX ‐248G>A (rs4645878) genotypes among European subjects undergoing rhegmatogenous retinal detachment (RRD) surgery in relation to the further development of proliferative vitreoretinopathy (PVR).

VRK2 identifies a subgroup of primary high-grade astrocytomas with a better prognosis.

BackgroundMalignant astrocytomas are the most common primary brain tumors and one of the most lethal among human cancers despite optimal treatment. Therefore, the characterization of molecular alterations underlying the aggressive behavior of these tumors and the identification of new markers are thus an important step towards a better patient stratification and management.Methods and resultsVRK1 and VRK2 (Vaccinia-related kinase-1, -2) expression, as well as proliferation markers, were determined in a tissue microarray containing 105 primary astrocytoma biopsies. Kaplan Meier and Cox models were used to find clinical and/or molecular parameters related to overall survival. The effects of VRK protein levels on proliferation were determined in astrocytoma cell lines. High levels of both protein kinases, VRK1 or VRK2, correlated with proliferation markers, p63 or ki67. There was no correlation with p53, reflecting the disruption of the VRK-p53-DRAM autoregulatory loop as a consequence of p53 mutations. High VRK2 protein levels identified a subgroup of astrocytomas that had a significant improvement in survival. The potential effect of VRK2 was studied by analyzing the growth characteristics of astrocytoma cell lines with different EGFR/VRK2 protein ratios.ConclusionHigh levels of VRK2 resulted in a lower growth rate suggesting these cells are more indolent. In high-grade astrocytomas, VRK2 expression constitutes a good prognostic marker for patient survival.

Functional characterization of rs2229094 (T>C) polymorphism in the tumor necrosis factor locus and lymphotoxin alpha expression in human retina: the Retina 4 project

Purpose The objective of this study is to determine the expression and localization of lymphotoxin alpha (LTA) in human retinas and the functionality of one of its polymorphisms rs2229094 (C13R) (T>C), previously associated with proliferative vitreoretinopathy (PVR) development. Materials and methods Total RNA from three healthy human retinas were extracted and subjected to reverse transcription-polymerase chain reaction (RT-PCR) analysis, using flanking primers of LTA cDNA. In addition, three human eyes with retinal detachment (RD) and three healthy control eyes were subjected to immunohistochemistry (IHC) with a specific antibody against LTA. The functionality of T and C alleles was assessed by using pCEFL-Flag expression vector and transient transfection assays in COS-1 cell line. In addition, expression analysis by RT-PCR, Western blot and subcellular localization of both alleles and by immunofluorescence assay was performed. Results RT-PCR analysis revealed no significant levels of messenger RNA (mRNA) LTA in healthy human retinas. Sequential IHC staining showed differences between healthy human and RD retinas. No differences in mRNA and protein expression levels and in subcellular localization between both alleles were found. Both alleles were located in the cytoplasm of COS-1 cells. Conclusion Although results suggest lack of functionality, the differences found in IHC study and its strong association with PVR and its relationship with tumor necrosis factor locus, warrant further studies and could justify the use of this polymorphism as a valid biomarker to identify high-risk patients to develop PVR after RD.