BackgroundWhile tamoxifen activity is mainly due to endoxifen and the concentration of this active metabolite is, in part, controlled by CYP2D6 metabolic status, clinical correlative studies have produced mixed results.FindingsIn an exploratory study, we determined the CYP2D6 metabolic status and plasma concentrations of endoxifen among 224 Filipino and Vietnamese women participating in a clinical trial of adjuvant hormonal therapy for operable breast cancer. We further conducted a nested-case–control study among 48 women (half with recurrent disease, half without) investigating the relationship of endoxifen concentrations and recurrence of disease.We found a significant association of reduced endoxifen plasma concentrations with functionally important CYP2D6 genotypes. High endoxifen concentrations were associated with higher risk of recurrence; with a quadratic trend fitted to a stratified Cox proportional hazards regression model, the likelihood ratio p-value was 0.002. The trend also showed that in 8 out of 9 pairs with low endoxifen concentrations, the recurrent case had lower endoxifen levels than the matched control.ConclusionsThis exploratory analysis suggests that there is an optimal range for endoxifen concentrations to achieve favorable effects as adjuvant therapy. In particular, at higher concentrations (>70 ng.ml), endoxifen may promote recurrence.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-52) contains supplementary material, which is available to authorized users.
BackgroundThe Plasmodium falciparum NA+/H+ exchanger (pfnhe1, gene PF13_0019) has recently been proposed to influence quinine (QN) susceptibility. However, its contribution to QN resistance seems to vary geographically depending on the genetic background of the parasites. Here, the role of this gene was investigated in in vitro QN susceptibility of isolates from Viet Nam.MethodNinety-eight isolates were obtained from three different regions of the Binh Phuoc and Dak Nong bordering Cambodia provinces during 2006-2008. Among these, 79 were identified as monoclonal infection and were genotyped at the microsatellite pfnhe1 ms4760 locus and in vitro QN sensitivity data were obtained for 51 isolates. Parasite growth was assessed in the field using the HRP2 immunodetection assay.ResultsSignificant associations were found between polymorphisms at pfnhe1 microsatellite ms4760 and susceptibility to QN. Isolates with two or more DNNND exhibited much lower susceptibility to QN than those harbouring zero or one DNNND repeats (median IC50 of 682 nM versus median IC50 of 300 nM; p = 0.0146) while isolates with one NHNDNHNNDDD repeat presented significantly reduced QN susceptibility than those who had two (median IC50 of 704 nM versus median IC50 of 375 nM; p < 0.01). These QNR associated genotype features were mainly due to the over representation of profile 7 among isolates (76.5%). The majority of parasites had pfcrt76T and wild-type pfmdr1 (> 95%) thus preventing analysis of associations with these mutations. Interestingly, area with the highest median QN IC50 showed also the highest percentage of isolates carrying the pfnhe1 haplotype 7.ConclusionsThe haplotype 7 which is the typical Asian profile is likely well-adapted to high drug pressure in this area and may constitute a good genetic marker to evaluate the dissemination of QNR in this part of the world.
The major changes in hormone levels that occur through the menstrual cycle have been postulated to affect the expression of hormone-regulated and proliferation-associated genes (PAGs) in premenopausal ER+ breast cancer. Whilst previous studies have demonstrated differences in gene expression, here, we investigated if there are within patient changes in the expression of oestrogen- and progesterone-regulated genes (ERGs and PRGs) and PAGs in ER+ breast cancer during the menstrual cycle. Samples from 96 patients in two independent prospective studies of the effect of menstrual cycle on ER+ breast cancer were used. Plasma hormone measurements were used to assign tumours to one of three pre-defined menstrual cycle windows: W1 (days 27–35 and 1–6; low oestradiol and low progesterone), W2 (days 7–16; high oestradiol and low progesterone) and W3 (days 17–26; intermediate oestradiol and high progesterone). RNA expression of 50 genes, including 27 ERGs, 11 putative PRGs and seven PAGs was measured. The AvERG (geomean of PGR, GREB1, TFF1 and PDZK1) was used as a composite measure of ERG expression and showed significant changes between the three windows of the menstrual cycle increasing over 2.2-fold between W1 and W2 and decreasing between W2 and W3 and between W3 and W1. Proliferation gene expression also varied significantly, following the same pattern of changes as ERG expression, but the changes were of lower magnitude (1.4-fold increase between W1 and W2). Significant changes in the expression of eight individual ERGs, including GREB1, PGR and TFF1, and two PAGs were observed between W1 and either W2 or W3 with all genes showing higher levels in W2 or W3 (1.3–2.4-fold; FDR 0.016–0.05). The AvProg, a composite measure of PRG expression, increased significantly (1.5-fold) in W3 compared to W1 or W2 but no significant changes were observed for individual PRGs. In conclusion, we observed significant changes in ERG, PRG and PAG expression in ER+ breast tumours during the menstrual cycle that may affect the assessment and interpretation of prominent biomarkers (e.g. PgR) and commonly used multigene prognostic signatures in premenopausal ER+ breast cancer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.