Changes in tumor cell adhesiveness affecting speed of dissemination and mode of metastatic growth

Abstract

Adhesion variants can be isolated from suspension growing highly metastatic murine ESb tumor cells under reproducible conditions from uncloned as well as from cloned ESb tumor cells. One such variant, ESb-MP, has been analyzed in detail. In vitro it had similar growth properties and high invasive capacity as the parental ESb cells. In vivo, ESb-MP cells showed a reduced growth capacity as compared to ESb cells. This was seen at the site of tumor cell transplantation (increased latency period) as well as at the site of secondary tumor growth in internal organs. ESb-MP tumor cells disseminated much later than ESb cells from the primary tumor into the blood stream. Both tumor lines metastasized to the liver but they affected liver functions in a different way: ESb cells infiltrated the liver diffusely and exerted toxic effects on liver parenchyma very quickly. This resulted in early increase of liver enzyme activity in the blood. In contrast, liver infiltrated by ESb-MP cells showed a more focal type of colonization and the organs seemed to be functioning for much longer periods. In fact, animals inoculated with ESb-MP cells subcutaneously or intravenously had an increased life expectancy compared to ESb-tumor-bearing animals of about 300%. The organotropism of both tumor lines remained similar although there were kinetic and quantitative differences, especially with regard to the kidney. In late stages of tumor growth, ESb-MP-tumor-bearing animals developed a high percentage of metastases in the kidney and around and within the spinal cord, thereby causing a syndrome of hind-leg paralysis. This syndrome was remarkable in its reproducibility, especially after intravenous tumor cell inoculation. The changed adhesiveness thus seemed to have affected the tumor latency period, the speed of dissemination into blood and internal organs, the mode of organ infiltration (focal vs. diffuse) and of metastatic growth, parameters which all might contribute to the greatly reduced overall malignancy.