TDK conference 2008

MDR1 transporter, which is the P (permeability) glycoprotein (Pgp) and multidrug resistance associated protein-1 (mrp1) are ones of the most important factors of the chemotherapy resistance of neoplasms. The higher expression of Pgp and mrp1 of tumour cells is considered as a negative prognostic factor. Int he veterinary practice the importance of these therapy resistance proteins is thought to be primarily important in the treatment of canine non-Hodgkin lymphoma, as this disease can only be tretaed by cytostatic drugs. Aim of our study was to find out whether the Pgp and mrp1 mRNA expression in lymphoid cells derived from lymph nodes of control healthy dogs (n=8) is different from the dogs with lymphoma (n=43), and whether the quantity of mRNA-expression in the patients is correlated with the clinical outcome of the chemotherapy.

All the patients were at advanced stage of the disease, with generalized peripheral lymphadenopathy, and all but one dog had hepato- or splenomegaly, and lymphadenopathy in the abdominal cavity, and lymphoma-associated radiographic alterations in the thoracic cavity. The entire left prescapular lymph node of the dogs was surgically removed. One part of the lymph node specimens was used for histopathological and immunohistochemical examinations, and the other part was stored at -80 oC, and used later for mRNA examinations. The lymph node samples were homogenised with protease and RNA-ase inhibitors then the RNAs were isolated. After this procedure a part of this samples were electrophoretised on agarose gel in order to detect the contamination of them with DNAs. For safety reasons DNA-ase was added to the samples. We synthesized cDNA, then DNAs by using real time (polymerase chain reaction-) PCR instrument. The quantity of synthesied DNA corresponded to the mRNA quantity of the tissues. For the statistical analysis we fomed three groups of lymph node samples according to their origin: control (healthy) dogs (n=8), dogs with lymphoma before undergoing to chemotherapy (n=39) and dogs with relapse after chemotherapy (n=8).

According to our findings the mRNA expression of the lymph node samples taken from healthy dogs was the smallest, more mRNA experssion was detected in dogs with lymphoma before therapy and even more in lymh nodes of dogs after relapse.