Effects of neuraminidase on apoptosis of blood lymphocytes in rats with implanted Morris tumor.

In this study we examined the influence of neuraminidase on apoptosis of peripheral blood lymphocytes in rats with an implanted Morris tumor. The main objectives of the study were to determine whether the percentage of apoptotic blood lymphocytes would depend on the dosing regimen of neuraminidase and whether neuraminidase would affect caspase-3 activity, a marker of the apoptosis, in blood lymphocytes. A total of 51 rats were used for the study. In three groups, totalling 39 animals, Morris tumor was implanted and neuraminidase was injected intravenously using two dosing regimens: 10 units three times on Day 4, Day 7, and Day 14 and 5 units as a single dose on Day 4 of the experiment or was skipped (control). The remaining 12 rats constituted a reference group of healthy animals. At the end of the experimental period on Day 21, blood was drawn from the heart, and mononuclear cells were separated and cultured. Apoptosis of blood lymphocytes was assessed in cell cultures from fluorescence spectra generated by a Sybr Green I dye forming bonds with nuclear DNA. Caspase-3 activity was measured colorimetrically in homogenates of lymphocyte cultures using a CASP-3-C kit (Sigma, St. Louis, MO). On the whole, the results demonstrate that the bigger, but not the smaller, dose of neuraminidase was markedly effective in preserving the vitality of blood lymphocytes and in decreasing both the number of apoptotic lymphocytes and capsase-3 activity in the rats with Morris tumor. Neuraminidase treatment failed, however, to lessen the tumor size. In conclusion, the study demonstrates that neuraminidase caused an appreciable decline in apoptosis of blood lymphocytes in rats with the Morris tumor; the effect was dose-dependent. Although neuraminidase failed to influence the local cancer development in terms of tumor size, its anti-apoptotic effect toward the cells of the immune system of a cancer host is of research interest as it may potentially offer a way to strengthen the host's immune response.