Proof-of-concept study: Evaluation of plasma and urinary electrolytes as markers of response to L-asparaginase therapy in dogs with high-grade lymphoma.

Response to chemotherapy is one of the most important prognostic factors in dogs with lymphoma. The objective of this feasibility study was to evaluate if clinical responses to a specific cytotoxic agent (L-asparaginase) could be anticipated by measuring analyte concentrations in plasma and urine concentrations of lymphoma-bearing dogs. We hypothesized that potassium and phosphate concentrations in plasma and urine would be higher in dogs that completely responded to therapy. Plasma and urine samples of dogs with lymphoma were obtained before 12 and 24 hours after intramuscular L-asparaginase injections. Peripheral lymph node volumes were evaluated according to the Veterinary Cooperative Oncology Group standardized criteria. Plasma and urine electrolyte, calcium, phosphate, creatinine, urea, total protein, and albumin concentrations were measured, and the fractional excretions of each electrolyte were calculated. Statistical analyses compared complete vs partial responders using a linear regression model. Contrast analyses were also performed to differentiate the mean of each group, with adjustments made with the Benjamini-Hochberg procedure. Fourteen dogs were included, eight with complete responses, and six with partial responses. Plasma phosphate concentrations were significantly higher at 12 hours (P = .0003) and 24 hours (P = .009) after complete responses to therapy. This study demonstrates the potential use of plasma and urine analyte monitoring after chemotherapy induction. Plasma phosphate measurements represent a potential indicator of early responses to L-asparaginase therapy. Larger population studies are warranted to confirm these preliminary results.

Role of ABC transporters in trans-epithelial transport of vitamin K antagonists.

Vitamin K antagonists (VKAs) remain the oral anticoagulant of choice in venous thromboembolic disease. These drugs are characterized by a large inter-individual variability requiring frequent dose tailoring. Genetic polymorphisms for cytochrome CYP2C9 and VKORC1 explain some of the variability, especially in warfarin and acenocoumarol responses. The aim of this study was to assess, in cell models, the role of ABC transporters in the intestinal transfer of the main coumarin derivatives (warfarin, acenocoumarol) and indanedione derivatives (phenindione, fluindione). The results show a basal to apical polarized transport for fluindione, phenindione and acenocoumarol only. Experimental studies using specific inhibitors of transport protein demonstrate the implication of MRPs and BCRP proteins and to a lesser extent P-gp. Warfarin and acenocoumarol seem to be poor inhibitors of MRPs protein, whereas fluindione and phenindione have a slight or no effect. The regulation of the expression of ABC transporters by exposure to VKAs was also investigated in Caco-2 cells. The expression of mRNA P-gp, MRP1, MRP2 and BCRP was weakly or not modified after 24 h of VKAs exposure. In conclusion, the intestinal transfer of indanedione derivatives and acenocoumarol could be influenced by transport proteins of the ABC superfamily. Coumarin derivatives are poor inhibitors of these proteins and AVKs have a slight effect on the mRNA ABC transporter expression level. Copyright © 2016 John Wiley & Sons, Ltd.