Growth of leukemias and lymphoid tumors in solid organs: demonstration of multiphasic proliferative activity

Tumors derived from lymphocytes, i.e., leukemias and lymphomas, generally grow diffusely in blood and bone marrow in the natural situation. However, they can also grow in "pseudo-solid" form in solid organs such as the liver, spleen and lymph nodes where the organs' capsule becomes a limiting barrier. We have studied tumor growth in these latter situations, i.e., in liver and spleen, tracing the tumor growth process by mass changes, protein, DNA and RNA content changes. We have also studied DNA-S activity by determining uptake of H3-TdR into DNA. These show that after large cell doses, i.e., 1 x 10(6) cells, a single sustained burst of DNA-S activity occurred and terminated with host death. With smaller cell doses, i.e., 1 x 10(4) cells, where a more prolonged growth period occurred, multiphasic growth was observed, i.e., a period of high DNA-S activity during a "silent" period where no organ growth was observed. A separate burst of DNA-S activity occurred with a delayed rapid organ increase phase. With it, organ enlargement and cell proliferation was marked, i.e., 2-8 fold, and ended with host death. It appears that a normal mechanism of organ enlargement by capsular relaxation allowed further tumor cell proliferation to occur.