DNA-PLOIDY AND CELL KINETIC CHARACTERISTICS IN CANINE NON-HODGKINS-LYMPHOMA

Malignant lymphoma in the dog is frequently postulated and used as a t herapeutic model for non-Hodgkin's lymphoma (NHL) in humans. In this s tudy DNA ploidy and the cell kinetic characteristics of canine maligna nt lymphoma were studied by flow cytometric (FCM) nuclear DNA measurem ents on fresh frozen tumor tissue from 94 dogs with NHL and on materia l from non-neoplastic lymph nodes from 20 dogs. The results were corre lated with histomorphology, immunophenotype and survival. All non-neop lastic tissues were diploid, whereas of the 94 lymphomas 74 were diplo id or near-diploid and 20 aneuploid. Of the aneuploid lymphomas, 1 con tained a hypoploid cell population. DNA indices of the aneuploid peaks ranged from 0.87 to 1.21 (mean 1.11). The mean S-phase fraction (8.2% , SD 4.8) was significantly lower in the non-neoplastic tissues than i n the lymphomas (11.4%, SD 5.1). A linear correlation was observed bet ween ECM S-phase fractions and bromodeoxyuridine (BrdU) labeling indic es (r=0.78; p<0.001) determined in paraffin-embedded tissue sections f rom 18 dogs with NHL after in vivo BrdU labeling. DNA ploidy status di d not correlate to the S-phase fraction. There were no differences in S-phase fraction and DNA ploidy between B cell and T cell lymphomas or between different histological classes using the Working Formulation. No correlation was found between S-phase fraction or DNA ploidy and s urvival in a series of 59 dogs treated with a combination chemotherapy protocol. It is concluded that the frequency of DNA aneuploidy in can ine malignant lymphoma is similar to that in human NHL. In contrast to findings in human NHL, however, no relationship was found between DNA ploidy or cell kinetic features and histomorphology or prognosis.