Aim
To investigate the activity and expression of P-glycoprotein (P-gp) and multidrug resistance-associated proteins (MRPs) in biopsy samples from lymph nodes of 22 dogs at the time of lymphoma diagnosis. Materials and
Conclusion
Low transporter activity and lack of correlation with expression suggest that spontaneous up-regulation of P-gp or MRP is not a common phenomenon in canine lymphoma.
Methods
Protein activity and expression were investigated by flow cytometry. Expression was assessed with monoclonal antibodies (C494 for P-gp and MRPm6 for MRP1). P-gp activity was determined by rhodamine 123 (Rho 123) efflux inhibited by verapamil and MRP by 5(6) carboxyfluorescein diacetate (CFDA) efflux inhibited by probenecid. Cell lineage was determined based on the expression of CD79α, CD21, CD3, CD4 and CD8.
Results
P-gp and MRP1 were expressed in all samples. Relative activity was low for both transporters and no correlation was found between transporter activity and expression. The majority of lymphomas were of B-cell origin.