Influence of clinical factors on the protective or deleterious impact of genetic variants in orthodontically induced external root resorption: an observational study.

BACKGROUND: Prediction of susceptibility to Orthodontically Induced External Apical Root Resorption (OIEARR) has been hampered by the complex architecture of this multifactorial phenotype. The aim of this study was to analyze the impact of the interaction of multiple variables in the susceptibility to OIEARR. METHODS: The study evaluated 195 patients requiring orthodontic treatment. Nine clinical and treatment variables, single nucleotide polymorphisms (SNPs) from five genes and variables interactions were analyzed as risk factors for OIEARR using a multiple linear regression model. RESULTS: The model explained 29% of OIEARR variability (ANOVA: p < 0.01). Duration of treatment was the most important predictor and gender was the second, closely followed by premolar extraction. For genes encoding osteoprotegerin (OPG), the receptor activator of nuclear factor κ B (RANK) and the IL1 receptor antagonist (IL1RN), the effect of analyzed variants changed from protective to deleterious depending on the duration of treatment and the age of the patient. CONCLUSIONS: This work shows that in OIEARR the impact of genetic susceptibility factors is dynamic changing according to clinical variables.

Promoting advanced medical services in the framework of 3PM-a proof-of-concept by the "Centro" Region of Portugal.

Multidisciplinary team from three universities based in the "Centro" Region of Portugal developed diverse approaches as parts of a project dedicated to enhancing and expanding Predictive, Preventive, and Personalized Medicine (3PM) in the Region. In a sense, outcomes acted as a proof-of-concept, in that they demonstrated the feasibility, but also the relevance of the approaches. The accomplishments comprise defining a new regional strategy for implementing 3PM within the Region, training of human resources in genomic sequencing, and generating good practices handbooks dedicated to diagnostic testing via next-generation sequencing, to legal and ethical concerns, and to knowledge transfer and entrepreneurship, aimed at increasing literacy on 3PM approaches. Further approaches also included support for entrepreneurship development and start-ups, and diverse and relevant initiatives aimed at increasing literacy relevant to 3PM. Efforts to enhance literacy encompassed citizens across the board, from patients and high school students to health professionals and health students. This focus on empowerment through literacy involved a variety of initiatives, including the creation of an illustrated book on genomics and the production of two theater plays centered on genetics. Additionally, authors stressed that genomic tools are relevant, but they are not the only resources 3PM is based on. Thus, they defend that other initiatives intended to enable citizens to take 3PM should include multi-omics and, having in mind the socio-economic burden of chronic diseases, suboptimal health status approaches in the 3PM framework should also be considered, in order to anticipate medical intervention in the subclinical phase. Supplementary Information: The online version contains supplementary material available at 10.1007/s13167-024-00353-9.

Clinical and Genetic Risk Factors for Drug-Induced Liver Injury Associated with Anti-Tuberculosis Treatment-A Study from Patients of Portuguese Health Centers.

Drug-induced liver injury (DILI) is an unpredictable and feared side effect of antituberculosis treatment (AT). The present study aimed to identify clinical and genetic variables associated with susceptibility to AT-associated hepatotoxicity in patients with pulmonary tuberculosis treated with a standard protocol. Of 233 patients enrolled, 90% prospectively, 103 developed liver injury: 37 with mild and 66 with severe phenotype (DILI). All patients with mild hepatitis had a RUCAM score ≥4 and all patients with DILI had a RUCAM score ≥ 6. Eight clinical variables and variants in six candidate genes were assessed. A logistic multivariate regression analysis identified four risk factors for AT-DILI: age ≥ 55 years (OR:3.67; 95% CI:1.82−7.41; p < 0.001), concomitant medication with other hepatotoxic drugs (OR:2.54; 95% CI:1.23−5.26; p = 0.012), NAT2 slow acetylator status (OR:2.46; 95% CI:1.25−4.84; p = 0.009), and carriers of p.Val444Ala variant for ABCB11 gene (OR:2.06; 95%CI:1.02−4.17; p = 0.044). The statistical model explains 24.9% of the susceptibility to AT-DILI, with an 8.9 times difference between patients in the highest and in the lowest quartiles of risk scores. This study sustains the complex architecture of AT-DILI. Prospective studies should evaluate the benefit of NAT2 and ABCB11 genotyping in AT personalization, particularly in patients over 55 years.

Lack of association of vitamin D receptor gene polymorphisms with susceptibility to type 1 diabetes mellitus in the Portuguese population.

The vitamin D receptor (VDR) gene is a candidate gene for susceptibility to autoimmune disorders. Association studies of VDR polymorphisms and risk of type 1 diabetes often produced conflicting results in different ethnic backgrounds. The aim of this study was to test for association between common VDR polymorphisms and the genetic susceptibility to type 1 diabetes in the Portuguese population. We genotyped 207 patients with type 1 diabetes and 249 controls for the FokI T>C (rs10735810), BsmI A>G (rs1544410), ApaI G>T (rs7975232), and TaqI C>T (rs731236) single nucleotide polymorphisms by polymerase chain reaction and restriction fragment length polymorphism analysis. The distribution of VDR genotype, allele, and haplotype frequencies did not differ significantly between patients and controls. These data suggest that the single nucleotide polymorphisms of the VDR gene are unlikely to contribute significantly to type 1 diabetes susceptibility in the Portuguese population.

The phenotypical and functional characteristics of cord blood monocytes and CD14(-/low)/CD16(+) dendritic cells can be relevant to the development of cellular immune responses after transplantation.

Umbilical cord blood (UCB) has been used as an alternative source of haematopoietic progenitors for transplantation presenting advantages over bone marrow (BM) that are related with known shortages of newborns' immune system at adaptive and innate levels. Using flow cytometry, we studied the expression of Toll-like receptors (TLRs) and chemokine receptors (CKRs) and the production of pro-inflammatory cytokines by monocytes and CD14(-/low)/CD16(+)DCs from peripheral blood (PB; n=10), and umbilical cord blood (UCB; n=10). CKRs and cytokines were studied before and after stimulation of cells with LPS plus IFN-gamma. We also identified the two populations in normal bone marrow samples (BM; n=5). BM presented lower frequencies of both studied populations when compared to UCB and PB. CD14(-/low)/CD16(+)DCs presented a pattern of TLR expression different from mature monocytes reflecting distinct functions for these two populations. UCB cells presented reduced expression of TLR-4 and lower capability to produce cytokines prior stimulation. The populations studied presented different patterns of CKR expression reflecting distinct migratory pathways. Moreover, UCB cells presented higher expressions of CXCR4 and CCR7 that may be involved in immune system maturation and stem cell homing. Monocytes and CD14(-/low)/CD16(+)DCs present functional and phenotypical characteristics that may contribute to the lower incidence and severity of GVHD.

Antagonistic effect of IL1 variants in periodontitis and external apical root resorption: Evidence from a literature review.

External apical root resorption (EARR) induced by orthodontic treatment and chronic periodontitis (CP) are complex phenotypes dependent on the interaction of multiple genetic and non-genetic risk factors. Apart from different environmental triggers, these phenotypes are caused by antagonistic biological mechanisms involving local immunoinflammatory reaction and alveolar bone metabolism, for which IL1 have a prominent role. Whereas EARR benefits from bone remodelling, CP is characterized by osteolytic damaged. Our aim was to verify if these two phenotypes have opposite genetic profiles, considering the most frequently analysed polymorphisms for both diseases. A review of the literature was performed searching for the association of rs1800587 from Interleukin-1 alpha (IL1A) gene and rs1143634 from interleukin-1 beta (IL1B) gene with EARR and CP. The electronic search included MEDLINE/PubMed, EBSCOhost, Cochrane and Web of Science databases. Twenty four articles met the inclusion and exclusion criteria. For IL1B polymorphism, two out of seven studies found a significant statistical association between EARR and CC genotype, whether for CP, there were eighth out of fifteen references describing a statistically significant associations with T allele. For IL1A variant, no significant association with EARR was described. In conclusion, literature review suggests that for IL1B SNP rs1143634, EARR and CP have an opposite genetic profile. For IL1A SNP, our hypothesis could not be confirmed.

Molecular detection of EGFRvIII-positive cells in the peripheral blood of breast cancer patients.

The aim of this study is to evaluate epidermal growth factor receptor variant III, EGFRvIII, a cancer specific mutant, as a possible marker for the diagnosis of breast cancer occult systemic disease. EGFRvIII mRNA was identified by an RT-nested PCR with a high sensitivity. In 102 women studied, the mutant was detected in the peripheral blood of 30% of 33 low risk, early stage patients, in 56% of 18 patients selected for neoadjuvant chemotherapy, in 63.6% of 11 patients with disseminated disease and 0% of 40 control women. In low risk, early stage patients, the presence of one or more tumour characteristics predicting recurrence such as the absence of oestrogen receptors and the presence of ERBB2 or histologic grades G2/G3 was significantly associated with EFGRvIII detection (p<0.05). EGFRvIII mRNA has characteristics to be a useful marker for the diagnosis of occult systemic disease in breast cancer. Follow-up studies will evaluate its clinical value as a decision criterion for systemic therapy.

BRCA1 and BRCA2 germline mutational spectrum and evidence for genetic anticipation in Portuguese breast/ovarian cancer families.

We present the first characterisation of the mutational spectrum of the entire coding sequences and exon-intron boundaries of the BRCA1 and BRCA2 genes as well as large BRCA1 rearrangements in Portuguese families with inherited predisposition to breast/ovarian cancer. Of the 100 probands studied, pathogenic mutations were identified in 22 (24.7%) of 89 breast and/or ovarian cancer families with more than one affected member (15 in BRCA1 and seven in BRCA2), but in none of the 11 patients without family history of cancer. One (6.7%) of the BRCA1 mutations is a large deletion involving exons 11-15. Seven pathogenic point mutations are novel: 2088C>T, 2156delinsCC, and 4255_4256delCT in BRCA1 and 4608_4609delTT, 5036delA, 5583_5584insT, and 8923C>T in BRCA2. The novel 2156delinsCC was identified in three probands from different families and probably represents a founder mutation in our population. We also found a previously reported 3450_3453del4 mutation in three unrelated patients. In addition to the 22 pathogenic mutations, we identified 19 missense mutations of uncertain pathogenic significance, three of them (5241G>C in BRCA1 and IVS6+13C>T and 3731T>C in BRCA2) previously undescribed. The percentage of cases with truncating mutations in BRCA1 and BRCA2 was higher in breast/ovarian cancer (37.0%, mostly BRCA1) and male breast cancer (40%, all BRCA2) families than in families with only female breast cancer (17.5%). Interestingly, we found evidence for genetic anticipation regarding age at diagnosis of both breast and ovarian cancer in those families presenting affected members in more than one generation. These findings should be taken into consideration while planning screening and prophylactic measures in families with inherited predisposition to breast and ovarian cancer.

Germline MUTYH (MYH) mutations in Portuguese individuals with multiple colorectal adenomas.

Germinal mutations in the base excision repair (BER) gene MUTYH (MYH) have recently been described in association with predisposition to multiple colorectal adenomas and cancer. In contrast to the classic dominant condition of familial adenomatous polyposis (FAP) due to germinal mutations in the APC gene, the MYH polyposis is an autosomal recessive disease. The identification of individuals affected by MYH polyposis brings new and important implications for the diagnostic, screening, genetic counseling, follow up and therapeutic options in these patients. In this study, screening for germinal mutations in the MYH gene was performed in 53 Portuguese individuals with multiple colorectal adenomas or classic adenomatous polyposis, in whom no mutation had been identified in the APC gene. The results revealed the presence of biallelic germline MYH mutations in 21 patients. In addition, we here report 3 mutations (c.340T>C [p.Y114H]; c.503G>A [p.R168H]; and c.1186_1187insGG [p.E396fsX437]) which, to our knowledge, have not been previously described.

Molecular diagnosis of Huntington disease in Portugal: implications for genetic counselling and clinical practice.

Huntington disease (HD) is a neurodegenerative, autosomal dominant disorder of late-onset, caused by the expansion of a CAG repeat in the coding region of the gene. Ours is the reference laboratory for genetic testing in HD, in Portugal, since 1998; 90.1% of all 158 families known were identified for the first time, including patients with unusual presentation or without family history. A total of 338 genetic tests were performed: 234 for diagnosis, 96 for presymptomatic and four for prenatal testing (four were done for family studies). Most referring physicians were neurologists (90.6%); 82.8% of all clinical diagnosis were confirmed, while 83.1% of those sent for exclusion were in fact excluded. In presymptomatic testing, an excess of female subjects (59.4%) was again verified; 37.5% of the consultands were found to be carriers. None of the foetuses, in four prenatal tests, were mutation carriers. One juvenile case was inherited from her mother. Our patient population is very similar to others described so far, namely in terms of mean age at onset and (CAG)(n) distribution, except perhaps for a higher frequency of large normal (class 2) alleles (3.7%). We also identify cases posing particular problems for genetic counselling, such as, 'homozygosity' that can pose a serious ethical dilemma, carriers of large normal alleles, and 'homoallelism' for a normal gene, which will demand further procedures and may delay results in presymptomatic and prenatal testing.

E-Cadherin (CDH1) and p53 rather than SMAD4 and Caspase-10 germline mutations contribute to genetic predisposition in Portuguese gastric cancer patients.

Approximately 30% of all hereditary diffuse gastric cancer (HDGC) families carry CDH1 germline mutations. The other two thirds remain genetically unexplained and are probably caused by alterations in other genes. Using polymerase chain reaction (PCR)/single-strand conformation polymorphism (SSCP)/sequencing, we screened 32 Portuguese families with a history of gastric cancer and 23 patients with early onset gastric cancer for CDH1 germline mutations. In probands negative for CDH1 mutations, we screened genes involved in hereditary cancer syndromes in which gastric cancer may be one of the component tumours, namely p53 (Li-Fraumeni Syndrome) and hMLH1 and hMSH2 (HNPCC). We also screened in these patients for mutations in Caspase-10, a gene inactivated in sporadic gastric cancer, and SMAD4, a gene whose inactivation in mice is associated with signet-ring cell carcinoma of the stomach. One of the families fulfilling the HDGC criteria harboured a CDH1 germline mutation, and one of the families with incomplete criteria harboured a p53 germline mutation. No mutations were identified in hMLH1 and hMSH2, and only sequence variants were found in SMAD4 and Caspase-10. The present work reports for the first time CDH1 germline mutations in Portuguese gastric cancer families, and highlights the need for p53 mutation screening in families lacking CDH1 germline mutations, in a country with one of the highest incidences of gastric cancer in the world. No evidence was found for a role of germline mutations in SMAD4 and Caspase-10 in families lacking CDH1 mutations.

Immunophenotypic and functional characterization of cord blood dendritic cells.

Dendritic cells (DCs) play a pivotal role in the activation of T cells, which are effector cells in graft-versus-host disease (GVHD). A low incidence of GVHD following cord blood (CB) transplantation has long been reported; despite this, little information is currently available on the characteristics of CB DCs. The goal of the present study was to investigate the immunophenotypic characteristics and distribution of CB DCs and their subsets. For that purpose we have analyzed 15 CB samples as compared to normal peripheral blood (PB) (n = 7) and blood from patients submitted to an allogeneic PB stem cell transplantation (allo-PBSCT) (n = 6). Our results show an overall decreased frequency of DCs in CB due to the presence of significantly lower numbers of CD123inter./CD33inter./CD16+ DCs. Phenotypically, CB DCs displayed a tendency to express lower levels of the gamma-chain interleukin-2 (IL-2) receptor (CD132) and of the CD86 co-stimulatory molecule, supporting a higher degree of immaturity for CB as compared to PB DCs. After activation of CB DCs with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) higher frequencies of cytokine-producing cells were found among CD123inter./CD33inter./CD16+ and CD123dim/CD33bright/CD16- DCs; however, when only the cytokine-producing DCs were considered, a significant decrease in the amount of different cytokine (e.g., IL-1beta and IL-6) produced per cell was observed especially for CD16+ CB DCs. These findings support a higher degree of immaturity for CB as compared to PB DCs that might contribute to explain, at least in part, the low incidence and severity of GVHD observed after CB transplantation.

Early onset of medullary thyroid carcinoma in a kindred with multiple endocrine neoplasia type iia associated with cutaneous lichen amyloidosis.

OBJECTIVE: To describe the molecular characterization of a kindred affected by the rare variant of multiple endocrine neoplasia type IIA (MEN IIA) associated with cutaneous lichen amyloidosis and to discuss the clinical implications in the management of this syndrome. METHODS: A kindred with four affected family members was identified, and DNA analysis was performed by sequencing exon 11 of the RET proto-oncogene. Presymptomatic genetic screening was offered to all first-degree relatives. RESULTS: Sequencing analysis of the RET proto-oncogene revealed a Cys634Trp (TGC->TGG) mutation in all clinically affected family members and in an asymptomatic 5-year-old child who, after thyroidectomy, was found to have multicentric medullary thyroid carcinoma and C-cell hyperplasia. A Gly691Ser (GGT->AGT) polymorphism was also detected in this family but did not segregate with the disease. CONCLUSION: To our knowledge, this is the earliest detection of medullary thyroid carcinoma reported thus far in a kindred with MEN IIA associated with cutaneous lichen amyloidosis, and this finding suggests that prophylactic thyroidectomy, in kindreds with this variant, should be performed before the age of 5 years.

Impairment of breast cancer cell invasion by COX-2-specific inhibitor NS398: roles of CXCR4 and of uPA system.

Inhibition of cyclooxygenase-2 (COX-2) is known to impair cancer cell metastatic behaviour, but the mechanisms involved largely remain elusive. We aimed to analyse whether the antimetastatic effect of COX-2 inhibition in breast cancer cells could be explained by variations in the expression levels of chemokine receptor CXCR4, vascular endothelium growth factor (VEGF) and UPA/UPAR components of the urokinase plasminogen activator system (uPAR). Breast cancer cell line MDA-MB-231 was exposed to COX-2-specific inhibitor NS398. Experimental data were assessed using Matrigel invasion tests, qRT-PCR, ELISA, flow cytometry and MTT test. Exposure to NS398 had no major effect on cell viability, apoptosis or VEGF production. Cell invasion was significantly decreased with reductions ranging from of 3.6% with 10 µM NS398 to 81.04% with 100 µM NS398. CXCR4 membrane expression was significantly reduced by 18% (P < 0.05) when cells were treated with 100 µM of NS398 for 72 h. UPA mRNA levels were significantly reduced to 78 and 63% after treatment with 10 µM NS398 for 48 and 72 h, respectively (P < 0.05). UPAR mRNA levels also decreased with mild NS398 concentrations, reaching the lowest level of 56% with 50 µM of NS398 for 48 h (P < 0.05). With NS398 higher concentrations, UPAR and UPA expression levels increased. According to our results, impairment of expression of CXCR4, UPA and UPAR differentially contribute to the antimetastatic effect of COX-2 inhibitors depending on drug concentration.

CYP1A1 m1 and m2 polymorphisms: genetic susceptibility to lung cancer.

Lung cancer is considered an environment-related disease that develops as a consequence of exposure to mutagenic agents, namely those present in tobacco. The CYP1A1 gene codifies the phase I enzyme aryl hydrocarbon hydroxilase (AHH) belonging to the cytochrome P450 system that plays a major role in the bio-activation of tobacco procarcinogenes. Two CYP1A1 polymorphisms, m1 (T6235C transition) and m2 (A4889G transition), are associated with greater enzymatic activity and have been described as genetic susceptibility factors for lung cancer. The aim of this study was to verify if this association holds true in blood samples of 175 lung cancer patients and 217 non-cancer patients from Portugal's midlands region. The samples were studied by restriction fragment length polymorphism (RFLP) assay. The allelic frequencies of the mutant alleles were 0.12 for allele C and 1.14 for allele G in the control population. The results were not statistically different from those alleles in the patient population. There was also no statistically significant difference in genotype distribution in lung cancer patients and controls even when combining high risk genotypes. In our control sample, as in other populations of different ethnic origin, both polymorphisms also seem to be in linkage disequilibrium. We conclude that in this sample of the Portuguese population, CYP1A1 m1 and m2 polymorphisms are too rare to be of clinical relevance, and do not seem to be associated with susceptibility to lung cancer.

TP53 germline mutations in Portugal and genetic modifiers of age at cancer onset.

The Li-Fraumeni syndrome (LFS) is a rare, autosomal dominant disease caused by TP53 germline mutations. This study aimed to characterize the TP53 mutational spectrum in patients suspected to have LFS in Portugal and to evaluate the influence of the MDM2-SNP309 and TP53-72Arg variants and of telomere length on age of tumor onset. Probands were primarily selected using the classical LFS criteria (two cases) or the more sensitive Chompret Li-Fraumeni-like (LFL) criteria (13 cases), but 12 additional patients that did not comply with those LFS or LFL criteria were included in the analysis based on clinical suspicion (LFS suspects). Nine of the 27 probands (33.3%) presented germline TP53 mutations, two of them occurring de novo and two of them being novel. Three of the nine TP53 mutations were found in families that did not comply with any of the commonly used criteria for TP53 testing, leaving room to recommend the use of less stringent criteria. An association was found between the presence of the TP53-72Arg (but not the MDM2-SNP309) variant and earlier age of onset in TP53 carriers. A negative correlation between telomere length and age of cancer onset was found in patients with germline TP53 mutation, whereas no such correlation was found in controls or in patients with wild-type TP53.

Genetic polymorphism of CYP2D6 influences susceptibility to papillary thyroid cancer.

OBJECTIVE: Xenobiotic-metabolizing enzymes are widely polymorphic and confer interindividual variation in the ability to detoxify carcinogens or to activate pro-carcinogens. A common polymorphism of cytochrome P450 2D6 (CYP2D6) results in lack of enzyme activity and has been associated with an altered susceptibility to several cancers. The aim of this study was to investigate the association between the CYP2D6 poor metaboliser genotype and the risk of papillary thyroid cancer (PTC). DESIGN: Retrospective case-control study. PATIENTS: One hundred and eighty-seven patients with PTC and 256 controls. MEASUREMENTS: Genotyping was performed by PCR and restriction enzyme analysis to detect the presence of the common CYP2D6*4 poor metaboliser allele. RESULTS: The frequency of individuals with the homozygous poor metaboliser genotype was lower in the patient group [1.6 vs. 5.5%, P = 0.037, OR = 0.28 (95% CI 0.09-0.93)]. The CYP2D6*4 allele frequency was also lower in the patient group [13.4 vs. 21.7%, P = 0.002, OR = 0.56 (95% CI 0.39-0.80)]. CONCLUSIONS: The results suggest that the poor metaboliser genotype is associated with a protective effect against PTC. This could be explained by a possible role of CYP2D6 on the metabolic activation of putative environmental chemical thyroid carcinogens or by linkage to another cancer-causing gene. Further research may allow the identification of metabolic risk factors and contribute towards understanding the molecular mechanisms involved in thyroid carcinogenesis.

PROP1 gene analysis in Portuguese patients with combined pituitary hormone deficiency.

OBJECTIVE: Mutations of the PROP1 gene lead to combined pituitary hormone deficiency (CPHD), which is characterized by a deficiency of GH, TSH, LH/FSH, PRL and, less frequently, ACTH. This study was undertaken to investigate the molecular defect in a cohort of patients with CPHD. DESIGN, PATIENTS AND MEASUREMENTS: A multicentric study involving 46 cases of CPHD (17 familial cases belonging to seven kindreds and 29 sporadic cases) selected on the basis of clinical and hormonal evidence of GH deficiency, central hypothyroidism and hypogonadotrophic hypogonadism, in the absence of an identified cause of hypopituitarism. Mutations of PROP1 were investigated by DNA sequencing. Clinical, hormonal and neuroradiological data were collected at each centre. RESULTS: PROP1 mutations were identified in all familial cases: five kindreds presented a c. 301-302delAG mutation, one kindred presented a c. 358C --> T (R120C) mutation and one presented a previously unreported initiation codon mutation, c. 2T --> C. Of the 29 sporadic cases, only two (6.9%) presented PROP1 germline mutations (c. 301-302delAG, in both). Phenotypic variability was observed among patients with the same mutations, particularly the presence and age of onset of hypocortisolism, the levels of PRL and the results of pituitary imaging. One patient presented a sellar mass that persisted into adulthood. CONCLUSIONS: This is the first report of a mutation in the initiation codon of the PROP1 gene and this further expands the spectrum of known mutations responsible for CPHD. The low mutation frequency observed in sporadic cases may be due to the involvement of other unidentified acquired or genetic causes.

CYP2D6 genetic polymorphisms are associated with susceptibility to pituitary tumors.

Several polymorphisms of drug-metabolizing enzymes have been implicated in the susceptibility to tumor development. The role of the CYP2D6, GSTM1 and GSTT1 genes has been extensively studied, with alleles conferring different metabolic efficiencies and tumor risk. We studied the relationship between the main polymorphisms of these genes and the susceptibility to develop pituitary tumors, by performing a case-control study comprising 235 patients and 256 controls which were genotyped by means of PCR-RFLP based assays. Frequencies of the CYP2D6*1 and of the poor metabolizer allele CYP2D6*4, were determined along with the frequencies of the GSTM1 and GSTT1 null genotypes. CYP2D6 genotype frequencies were similar in patients and controls (p=0.087). CYP2D6*1 and CYP2D6*4 allele frequencies were 83.8%, 16.2% in cases and 78.3%, 21.7% in controls, showing a significant difference between the two groups (p=0.012). There were no significant differences between the frequencies of the GSTM1 and GSTT1 null genotypes in both groups. No association was found between histological type and any of the studied polymorphisms. Our data suggest an association of the CYP2D6*1 allele and the susceptibility to pituitary adenomas, which could be due to an increased metabolism of unidentified procarcinogens or to linkage disequilibrium with another gene involved in pituitary tumorigenesis.