Yazan: admin Tarih: Ağu 6th, 2008 | Kategori::
Gene polymorphisms
Am J Hematol. 2005 Sep;80(1):26-34.
Department of Biology, Middle East Technical University, Ankara, Turkey.
Multidrug-resistance (MDR) phenotype is a serious limitation to the effective chemotherapeutic treatment of many cancer types, including leukemia. One of the most important proteins, the over-expression of which is responsible for the multidrug-resistance phenotype in many cancer types, is P-glycoprotein. This protein is the product of the MDR1 gene. In previous studies, single-nucleotide polymorphisms (SNPs) C3435T, G2677T, and T-129C in the MDR1 gene were shown to be correlated with lower P-glycoprotein expression in normal tissues. It was suggested that this might have an advantage in cancer chemotherapy by resulting in a low drug-resistance phenotype. The frequencies of these SNPs were studied in 45 acute leukemia patients (25 of which were primary refractory and 20 of which were drug-sensitive) and 17 healthy individuals, forming a Turkish population of 62 individuals. In the first part of the study, these polymorphisms were compared with other populations. Marked differences were apparent between African and Turkish populations for the C3435T polymorphism. On the other hand, similarities were found between other Caucasian/Asian and Turkish populations (P < 0.001). However, for the G2677T polymorphism, the Turkish population is different than Japanese and German populations (P < 0.001). For the T-129C polymorphism, all individuals in the studied population were homozygous for the T/T genotype. In the second part of this study, drug-resistant and drug-sensitive acute leukemia patients were compared for these SNPs. These polymorphisms did not seem to have a significant effect on P-glycoprotein-mediated drug resistance in the patients studied.
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Department of Medical Biology and Genetics, Faculty of Medicine, Gazi University, 06500 Besevler, Ankara, Turkey.
BACKGROUND: DNA sequence variations in HIF-1 alpha gene might yield changes both in the production outcomes and in the activities of the gene. Overexpression of the HIF-1 alpha subunit, resulting from intratumoral hypoxia and genetic alterations, has been demonstrated in common human cancers and is correlated with tumor angiogenesis and patient mortality. In this study, we aimed to determine how the three single nucleotide polymorphisms (SNPs, C1772T and G1790A exon 12, C111A exon 2) in the HIF-1 alpha gene coding regions affect the ovarian, cervical and endometrial cancer patients in the Turkish population. A study on this relationship has not been conducted to date. METHOD: 102 gynecologic cancer patients and 107 healthy controls were studied. Genotypes of the three polymorphisms were analyzed by PCR-RFLP. RESULTS: There was no significant difference between ovarian cancer patients and controls in terms of the distribution of C1772T genotypes and alleles (P>0.05). However, there was a highly significant increase in the frequency of both CT 1772 and TT 1772 genotypes in patients with cervical and endometrial cancers compared with healthy controls. In fact, 1772T allele-carriers (CT+TT genotypes) showed an association with the risk of cervical and endometrial cancers compared to the wild type (OR=3.84, 95% CI: 1.65-8.93; OR=7.41, 95% CI: 2.33-23.59, respectively). C1772T polymorphism was not associated with family history concerning gynecologic and/or other cancer types, stages (I-IV) and grades of tumor, smoking habits and existence of other diseases that generate a hypoxic microenvironment even after multivariable logistic regression analysis. As for HIF-1 alpha G1790A genotypes, the frequencies of G alleles were 98% in ovarian patients and 100% in the control group. We found no significant difference in the genotype distribution and allele frequencies between the ovarian patients and healthy control subjects. There were no GA and AA genotypes among the cervical and endometrial cancer patients. As for HIF-1 alpha C111A polymorphism, we did not find CA and AA variants of the gene in controls or in any of the three types of patients. CONCLUSION: Our results suggest that the C1772T polymorphism of the HIF-1 alpha may be associated with cervical and endometrial cancers.
