Introduction

Drug resistance is associated with cellular mechanisms and factors that affect the bioavailability and efficacy of drugs. One of the most studied mechanisms are the overexpression of P-gp, p53 gene and MDM2 oncogene.

Objectives

Correlating at diagnosis immunophenotyping with the expression of P-gp, MDM2 and p53, by immunohistochemistry in lymph nodes of dogs with lymphoma.

Methodology

Twenty dogs with multicentric lymphoma treated in the Veterinary Hospital - UNESP/Jaboticabal were studied. Antibodies to p53 (CM1 clone), MDM2 (ab38618 clone) and P-gp (C494 clone) were used.

Results

Nuclear positive immunostaining of p53 was observed in 25% (5/20) of the samples, while 75% (15/20) were negative. Regarding reactivity of MDM2, it was possible to identify nuclear and cytoplasmatic immunostaining in 30% (6/20) of the samples, while 70% (17/20) were negative. Patients expressing both markers (p53 and MDM2) had a shorter survival rate (p<0.05). When evaluating the expression of P-gp, it was possible to identify positive cytoplasmatic immunostaining in 80% (16/20) of the samples, and only 20% (4/20) were negative. It was not possible to identify significant difference in the survival curve (p=0.5238).

Conclusion

Patients who simultaneously expressed P53 and MDM2 had a lower survival rate. p53 and MDM2 activity during neoplastic processes negatively affects the treatment and prognosis of animals affected by lymphoma. P-gp expression had no difference in the survival of patients.