Comprehensive assessment of cytochromes P450 and transporter genetics with endoxifen concentration during tamoxifen treatment.

OBJECTIVES: Tamoxifen bioactivation to endoxifen is mediated primarily by CYP2D6; however, considerable variability remains unexplained. Our aim was to perform a comprehensive assessment of the effect of genetic variation in tamoxifen-relevant enzymes and transporters on steady-state endoxifen concentrations. PATIENTS AND METHODS: Comprehensive genotyping of CYP enzymes and transporters was performed using the iPLEX ADME PGx Pro Panel in 302 tamoxifen-treated breast cancer patients. Predicted activity phenotype for 19 enzymes and transporters were analyzed for univariate association with endoxifen concentration, and then adjusted for CYP2D6 and clinical covariates. RESULTS: In univariate analysis, higher activity of CYP2C8 (regression ß=0.22, P=0.020) and CYP2C9 (ß=0.20, P=0.04), lower body weight (ß=-0.014, P<0.0001), and endoxifen measurement during winter (each ß<-0.39, P=0.002) were associated with higher endoxifen concentrations. After adjustment for the CYP2D6 diplotype, weight, and season, CYP2C9 remained significantly associated with higher concentrations (P=0.02), but only increased the overall model R by 1.3%. CONCLUSION: Our results further support a minor contribution of CYP2C9 genetic variability toward steady-state endoxifen concentrations. Integration of clinician and genetic variables into individualized tamoxifen dosing algorithms would marginally improve their accuracy and potentially enhance tamoxifen treatment outcomes.

Wntless spatially regulates bone development through ß-catenin-dependent and independent mechanisms.

BACKGROUND: Canonical and noncanonical Wnt signaling pathways both play pivotal roles in bone development. Wntless/GPR177 is a chaperone protein that is required for secretion of all Wnt ligands. We previously showed that deletion of Wntless within mature osteoblasts severely impaired postnatal bone homeostasis. RESULTS: In this study, we systemically evaluated how deletion of Wntless in different stages of osteochondral differentiation affected embryonic bone development, by crossing Wntless (Wls)-flox/flox mice with strains expressing cre recombinase behind the following promoters: Osteocalcin, Collagen 2a1, or Dermo1. Ex vivo µCT and whole-mount skeletal staining were performed to examine skeletal mineralization. Histology and immunohistochemistry were used to evaluate cellular differentiation and alterations in Wnt signaling. In this work, we found that Wntless regulated chondrogenesis and osteogenesis through both canonical and noncanonical Wnt signaling. CONCLUSIONS: These findings provide more insight into the requirements of different Wnt-secretion cell types critical for skeletal development.

Accelerated and increased joint damage in young mice with global inactivation of mitogen-inducible gene 6 after ligament and meniscus injury.

INTRODUCTION: Ligament and meniscal damage can cause joint disease. Arthritic joints contain increased amounts of epidermal growth factor receptor (EGFR) protein, and polymorphisms in EGFR are associated with arthritis risk. The role of endogenous EGFR regulation during joint disease due to ligament and meniscal trauma is unknown. Mitogen-inducible gene 6 (MIG-6) can reduce EGFR phosphorylation and downstream signaling. We examined the effect of EGFR modulation by MIG-6 on joint disease development after ligament and meniscus injury. METHODS: Knee ligament transection and meniscus removal were performed surgically on mice homozygous for a global inactivating mutation in MIG-6 (Mig-6⁻/⁻) and in wild-type (WT) animals. RESULTS: Two weeks after surgery, Mig-6⁻/⁻mice had bone erosion as well as greater fibrous tissue area and serum RANKL concentration than WT mice. Four weeks after surgery, Mig-6⁻/⁻mice had less cartilage and increased cell proliferation relative to contralateral control and WT knees. Increased apoptotic cells and growth outside the articulating region occurred in Mig-6⁻/⁻mice. Tibia trabecular bone mineral density (BMD) and the number of trabeculae were lower in surgically treated knees relative to the respective control knees for both groups. BMD, as well as trabecular thickness and number, were lower in surgically treated knees from Mig-6⁻/⁻mice relative to WT surgically treated knees. Phosphorylated EGFR staining in surgically treated knees decreased for WT mice and increased for Mig-6⁻/⁻mice. Fewer inflammatory cells were present in the knees of WT mice. CONCLUSION: Mig-6⁻/⁻mice have rapid and increased joint damage after ligament and meniscal trauma. Mig-6 modification could lessen degenerative disease development after this type of injury.

Interaction of the fluoroquinolone antibiotic, ofloxacin, with titanium oxide nanoparticles in water: adsorption and breakdown.

The mobility and fate of fluoroquinolone antibiotics in natural waters, soil-water systems and wastewater are controlled in part by surface interactions with nanometer (10⁻9 m) metal oxide particles. Experiments were performed by mixing solutions of ofloxacin (OFL), a common, fluoroquinolone-class human and veterinary antibiotic, with 25 nm-TiO2 (anatase) nanoparticles at different pH conditions. Both sorption and degradation of OFL were observed in the drug-nanoparticle solutions with initial OFL concentrations of ~3 to 690 µM. Though overall isotherm behavior is logarithmic, OFL removal from the solution can be approximated by linear removal coefficients (K(r)). At pH 4, K(r)=42±8 L kg⁻¹, at pH 6 K(r)=1288±217 L kg⁻¹, and at pH 9 K(r)=26±7 L kg⁻¹. Rinsing of substrates at pH 4 resulted in desorption of approximately 11% of the original OFL removed from the solution by TiO2 nanoparticles. Less than 1% of the removed OFL at pH 6 was recovered by rinsing the substrate; and, at pH 9 about 39% of the OFL removed by nanoparticles during the initial mixing experiment was desorbed during rinsing. Mass spectral analysis of OFL solutions after the removal of the solid nanoparticles yielded ions that indicate the presence of de-methylated and de-carboxylated fluoroquinolone species, resulting from the degradation of OFL at the TiO2 surface.