Different Growth Rates of Swarm Chondrosarcoma in Lewis and Wistar Rats Correlate with Different Thyroid Hormone Levels

Abstract

The transplantable Swarm rat chondrosarcoma grew to twice the weight in 5 weeks in Lewis strain rats (∼80g) as it did in Wistar strain rats (∼40g). Wistar tumor passaged into Lewis rats adopted the accelerated growth rate of the Lewis tumor on the second passage. Conversely Lewis tumor passaged into Wistar rats grew like Wistar lineage chondrosarcoma after two passages. Lewis and Wistar tumors had a similar histological appearance. The extracellular matrix composition of the two tumors was very similar. Tumor explant cultures synthesized about the same amount of ³⁵S-proteoglycans and the same proportion of ³H-hyaluronate: ³H-chondroitin sulfate. Serum levels of growth hormone and insulin were the same in the two strains but T₃ and T₄ levels were 50% higher in Lewis rats compared to Wistar rats. It is likely that accelerated tumor growth in Lewis strain rats is related to the higher thyroid hormone levels.