Lack of correlation of growth attenuation of murine lymphoma caused by in vitro passage with loss of lactate dehydrogenase virus.

Previous studies demonstrated that 6C3HED, a transplantable murine lymphosarcoma, could be modulated by long-term in vitro culture to yield cell lines with attenuated growth characteristics in vivo. The present studies examine the role of lactate dehydrogenase virus (LDV) infection in this phenomenon. LDV, a potentially immunosuppressive virus, was present in the parent tumor maintained by serial transfer in vivo. Explantation and serial propagation in vitro eliminated the virus. Two LDV-free in vitro lines (6C3HED/A and 6C3HED/B) were examined by being grafted into LDV-negative mice. Line 6C3HED/A behaved virulently, growing in a similar fashion as the parent tumor. In contrast, line 6C3HED/B demonstrated the same initial growth rate as the parent tumor, but it was rapidly and regularly rejected by grafted mice. Prior infection of mice with LDV did not affect the growth characteristics of these lines. Thus the growth characteristics of the parent, 6C3HED/A, or 6C3HED/B tumor were not correlated with infection with LDV.