Evaluation of Pgp (MDR1) immunohistochemistry in canine lymphoma – prognostic and clinical aspects

Permeability glycoprotein (P-glycoprotein, Pgp) immunohistochemistry (IHC) was evaluated in dogs with multicentric lymphoma treated with cyclophosphamide– doxorubicin–vincristine–prednisolone with or without L-Asparaginase. Lymph nodes of 33 untreated dogs were immunophenotyped: Ki67% and Pgp analyses (with anti-Pgp, monoclonal mouse C494 clone) were performed. Pgp positivity rate and intensity were determined microscopically (by manual counting done by two blinded authors in two parallel specimens). The median overall survival time (OST) was 333 days and the relapse-free period (RFP) 134 days. Pgp expressions were positive in 18 out of 33 (54.5%) of tumour cells. T-cell types stained more intensively. Lower OST and RFP were found with Pgp positivity ≥ 35% (OST: 240 days, RFP: 95 days) compared to Pgp positivity < 35% (OST: 428 days, RFP: 232 days). Intensive staining was associated with a lower OST and RFP (240 and 103 days, respectively) than weak staining (428 and 221 days, respectively). Death due to adverse drug reactions was best predicted at Pgp positivity ≤ 6.5% (sensitivity/specificity: 0.55/0.81) and ≤ 123 days (sensitivity/ specificity: 0.55/0.86). Pgp evaluation by IHC can have prognostic value with a properly established Pgp% positivity cut-off value in dogs treated with Pgp substrate drugs

Celecoxib Prevents Doxorubicin-Induced Multidrug Resistance in Canine and Mouse Lymphoma Cell Lines

Background: Treatment of malignancies is still a major challenge in human and canine cancer, mostly due to the emergence of multidrug resistance (MDR). One of the main contributors of MDR is the overexpression P-glycoprotein (Pgp), which recognizes and extrudes various chemotherapeutics from cancer cells. Methods: To study mechanisms underlying the development of drug resistance, we established an in vitro treatment protocol to rapidly induce Pgp-mediated MDR in cancer cells. Based on a clinical observation showing that a 33-day-long, unplanned drug holiday can reverse the MDR phenotype of a canine diffuse large B-cell lymphoma patient, our aim was to use the established assay to prevent the emergence of drug resistance in the early stages of treatment. Results: We showed that an in vitro drug holiday results in the decrease of Pgp expression in MDR cell lines. Surprisingly, celecoxib, a known COX-2 inhibitor, prevented the emergence of drug-induced MDR in murine and canine lymphoma cell lines. Conclusions: Our findings suggest that celecoxib could significantly improve the efficiency of chemotherapy by preventing the development of MDR in B-cell lymphoma

Celecoxib Prevents Doxorubicin-Induced Multidrug Resistance in Canine and Mouse Lymphoma Cell Lines.

BACKGROUND: Treatment of malignancies is still a major challenge in human and canine cancer, mostly due to the emergence of multidrug resistance (MDR). One of the main contributors of MDR is the overexpression P-glycoprotein (Pgp), which recognizes and extrudes various chemotherapeutics from cancer cells. METHODS: To study mechanisms underlying the development of drug resistance, we established an in vitro treatment protocol to rapidly induce Pgp-mediated MDR in cancer cells. Based on a clinical observation showing that a 33-day-long, unplanned drug holiday can reverse the MDR phenotype of a canine diffuse large B-cell lymphoma patient, our aim was to use the established assay to prevent the emergence of drug resistance in the early stages of treatment. RESULTS: We showed that an in vitro drug holiday results in the decrease of Pgp expression in MDR cell lines. Surprisingly, celecoxib, a known COX-2 inhibitor, prevented the emergence of drug-induced MDR in murine and canine lymphoma cell lines. CONCLUSIONS: Our findings suggest that celecoxib could significantly improve the efficiency of chemotherapy by preventing the development of MDR in B-cell lymphoma

Celecoxib Prevents Doxorubicin-Induced Multidrug Resistance in Canine and Mouse Lymphoma Cell Lines

Background: Treatment of malignancies is still a major challenge in human and canine cancer, mostly due to the emergence of multidrug resistance (MDR). One of the main contributors of MDR is the overexpression P-glycoprotein (Pgp), which recognizes and extrudes various chemotherapeutics from cancer cells. Methods: To study mechanisms underlying the development of drug resistance, we established an in vitro treatment protocol to rapidly induce Pgp-mediated MDR in cancer cells. Based on a clinical observation showing that a 33-day-long, unplanned drug holiday can reverse the MDR phenotype of a canine diffuse large B-cell lymphoma patient, our aim was to use the established assay to prevent the emergence of drug resistance in the early stages of treatment. Results: We showed that an in vitro drug holiday results in the decrease of Pgp expression in MDR cell lines. Surprisingly, celecoxib, a known COX-2 inhibitor, prevented the emergence of drug-induced MDR in murine and canine lymphoma cell lines. Conclusions: Our findings suggest that celecoxib could significantly improve the efficiency of chemotherapy by preventing the development of MDR in B-cell lymphoma