Improved anti-emetic efficacy of 5-HT3 receptor antagonists in cancer patients with genetic polymorphisms of ABCB1 (MDR1) drug transporter.

Chemotherapy-induced nausea and vomiting (CINV) remains a major adverse effect decreasing quality of life in patients with cancer. Genetic variations among patients may be responsible for part of the lack of efficacy of anti-emetic drugs. The aim of this study was to investigate how the genetic variants of the drug transporter ABCB1 (MDR1) gene affect anti-emetic treatment with 5-HT3 receptor antagonists. Patients (n = 239) receiving moderately or highly emetogenic chemotherapy and ondansetron or granisetron were included in the study. Anti-emetic responses were recorded daily. The primary end-point of the assessment was the total control rates of CINV in the acute and delayed phases after chemotherapy. Genotyping was performed by PCR-RFLP. In the acute phase, patients with ABCB13435TT, 1236TT or 2677TT genotypes had a higher control rate of CINV than other genotype groups: (64.7% in 3435TT versus 45.7% in 3435CC+CT, p = 0.016; 65.1% in 1236TT versus 46.4% in 1236CC+CT, p = 0.027; 66.7% in 2677TT versus 46.5% in other genotypes, p = 0.021). Subjects carrying homozygous variant alleles together (TT-TT-TT) showed a significantly higher protection from nausea and vomiting (67.7% in TT-TT-TT versus 47.1% in other genotypes, p = 0.032). After the logistic regression analysis with adjustment for other known covariates, the total control rate was significantly higher in the 3435TT genotype group during the acute phase (p = 0.021). No significant change was found between the total control rates among genotypes in the delayed phase. Each of three 3435TT, C1236TT, 2677TT genotypes of ABCB1 and their combination was associated with about 50% higher anti-emetic response to 5-HT3 receptor antagonists in the acute phase of chemotherapy in patients with cancer receiving moderately or highly emetogenic chemotherapy. ABCB1 (MDR1) genotypes may contribute to predict the anti-emetic efficacy of 5-HT3 antagonists.

Association between ADH1C and ALDH2 polymorphisms and alcoholism in a Turkish sample.

BACKGROUND: Polymorphisms in the genes encoding alcohol metabolizing enzymes are associated with alcohol dependence. AIM: To evaluate the association between the alcohol dehydrogenase 1C (ADH1C) Ile350Val and aldehyde dehydrogenase 2 (ALDH2) Glu504Lys polymorphisms and alcohol dependence in a Turkish sample. METHODS: 235 individuals (115 alcohol-dependent patients and 120 controls) were genotyped for ADH1C and ALDH2 with PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism). Association between the polymorphisms and family history, daily and maximum amount of alcohol consumed was investigated. The associations between alcohol dependence, severity of consumption and family history and the polymorphisms were analyzed by chi-square or Fisher's exact test where necessary. Relationship between genotypes and dependence related features was evaluated using analysis of variance (ANOVA). RESULTS: The -350Val allele for ADH1C (ADH1C*2) was increased in alcohol-dependent patients (P = 0.05). In individuals with a positive family history, the genotype distribution differed significantly (P = 0.031) and more patients carried the Val allele compared with controls (P = 0.025). Genotyping of 162 participants did not reveal the -504Lys allele in ALDH2. CONCLUSIONS: These findings suggest that ADH1C*2 is associated with alcohol dependence in the Turkish population displaying a dominant inheritance model. ADH1C*2 allele may contribute to the variance in heritability of alcohol dependence. The ALDH2 -504Lys/Lys or Glu/Lys genotypes were not present in alcohol-dependent patients, similar to that seen in European populations and in contrast to the findings in the Asian populations.

Postnatal establishment of allelic Gαs silencing as a plausible explanation for delayed onset of parathyroid hormone resistance owing to heterozygous Gαs disruption.

Pseudohypoparathyroidism type-Ia (PHP-Ia), characterized by renal proximal tubular resistance to parathyroid hormone (PTH), results from maternal mutations of GNAS that lead to loss of α-subunit of the stimulatory G protein (Gαs) activity. Gαs expression is paternally silenced in the renal proximal tubule, and this genomic event is critical for the development of PTH resistance, as patients display impaired hormone action only if the mutation is inherited maternally. The primary clinical finding of PHP-Ia is hypocalcemia, which can lead to various neuromuscular defects including seizures. PHP-Ia patients frequently do not present with hypocalcemia until after infancy, but it has remained uncertain whether PTH resistance occurs in a delayed fashion. Analyzing reported cases of PHP-Ia with documented GNAS mutations and mice heterozygous for disruption of Gnas, we herein determined that the manifestation of PTH resistance caused by the maternal loss of Gαs, ie, hypocalcemia and elevated serum PTH, occurs after early postnatal life. To investigate whether this delay could reflect gradual development of paternal Gαs silencing, we then analyzed renal proximal tubules isolated by laser capture microdissection from mice with either maternal or paternal disruption of Gnas. Our results revealed that, whereas expression of Gαs mRNA in this tissue is predominantly from the maternal Gnas allele at weaning (3 weeks postnatal) and in adulthood, the contributions of the maternal and paternal Gnas alleles to Gαs mRNA expression are equal at postnatal day 3. In contrast, we found that paternal Gαs expression is already markedly repressed in brown adipose tissue at birth. Thus, the mechanisms silencing the paternal Gαs allele in renal proximal tubules are not operational during early postnatal development, and this finding correlates well with the latency of PTH resistance in patients with PHP-Ia.

Intracellular transactivation of epidermal growth factor receptor by α1A-adrenoceptor is mediated by phosphatidylinositol 3-kinase independently of activation of extracellular signal regulated kinases 1/2 and serine-threonine kinases in Chinese hamster ovary cells.

Transactivation of epidermal growth factor receptor (EGFR) by α1-adrenoceptor (α1-AR) is implicated in contraction and hypertrophy of vascular smooth muscle (VSM). We examine whether all α1-AR subtypes transactivate EGFR and explore the mechanism of transactivation. Chinese hamster ovary (CHO) cells stably expressing one subtype of α1-AR were transiently transfected with EGFR. The transactivation mechanism was examined both by coexpression of a chimeric erythropoietin (EPO)-EGFR with an extracellular EPO and intracellular EGFR domain, and by pharmacologic inhibition of external and internal signaling routes. All three α1-AR subtypes transactivated EGFR, which was dependent on the increase in intracellular calcium. The EGFR kinase inhibitor AG1478 [4-(3'-chloroanilino)-6,7-dimethoxyquinazoline] abrogated α1A-AR and α1D-AR induced phosphorylation of EGFR, but both the inhibition of matrix metalloproteinases by GM6001 [(R)-N4-hydroxy-N(1)-[(S)-2-(1H-indol-3-yl)-1-methylcarbamoyl-ethyl]-2-isobutyl-succinamide] or blockade of EGFR by cetuximab did not. Stimulation of α1A-AR and α1D-AR also induced phosphorylation of EPO-EGFR chimeric receptors. Moreover, α1A-AR stimulation enhanced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 and serine-threonine kinases (Akt), which were both unaffected by AG1478, indicating that ERK1/2 and Akt phosphorylation is independent of EGFR transactivation. Accordingly, inhibitors of ERK1/2 or Akt did not influence the α1A-AR-mediated EGFR transactivation. Inhibition of calcium/calmodulin-dependent kinase II (CaMKII), phosphatidylinositol 3-kinase (PI3K), and Src, however, did block EGFR transactivation by α1A-AR and α1D-AR. These findings demonstrate that all α1-AR subtypes transactivate EGFR, which is dependent on an intracellular signaling route involving an increase in calcium and activation of CaMKII, PI3K, and Src, but not the of ERK1/2 and Akt pathways.

Functional effects of endothelial nitric oxide synthase genetic polymorphisms on haemorheological parameters in healthy human individuals.

The constitutive endothelial nitric oxide synthase (eNOS) plays a major role in circulatory homoeostasis and shows genetic polymorphism. eNOS is expressed and functional in blood cells, including erythrocytes. There is limited knowledge about the consequences of eNOS genetic variability in haemorheological parameters and erythrocyte functioning. The purpose of this study was to investigate the effects of three eNOS genetic polymorphisms, namely exonic G894T (Glu298Asp), intronic VNTR (27-bp repeat) and 5'-flanking T(-786)C polymorphisms on haemorheological variables, such as erythrocyte deformability and erythrocyte aggregation (rouleaux formation) in healthy non-smoking volunteers. Sixty subjects (19 women, 41 men) were examined for genotypes and haemorheological variables. Genotypes were determined by polymerase chain reaction and restriction analysis. Haemorheological variables were measured by means of a laser-assisted optical rotational cell analyser (LORCA). Erythrocyte aggregation was significantly decreased in individuals with 894TT genotype when compared to subjects with the (G) allele. Aggregation indices (AI) were 54.7±3.2% versus 61.0±0.9% (p=0.026), and the half-lives (t(1/2) ) for aggregation formation were 3.43±0.43 versus 2.55±0.12 sec. (p=0.024), respectively. Similarly, VNTR-bb genotype significantly altered erythrocyte aggregability. AI values were 58.7±1.1% in subjects with VNTR-a allele versus 63.7±1.2% in subjects with bb genotype (p=0.011); t(1/2) values were 2.86±0.16 versus 2.20±0.13 sec., respectively (p=0.016). T(-786)C polymorphism did not change any haemorheological parameters. These findings suggest that eNOS 894TT genotype is associated with decreased erythrocyte aggregation, while VNTR-bb genotype increases aggregability in healthy human individuals. eNOS genetic variants may contribute in the pathogenesis of microvascular disorders by altering erythrocyte functions in human beings.