Turnover in Neoplastic Tissue

If the phosphatide molecules of carcinomatous tissue were replaced at a high rate by labeled molecules, and such molecules were given off by the tumor to the circulation shortly after the administration of labeled phosphate, the presence of carcinomatous tissue could possibly be diagnosed by determination of the activity of plasma phosphatides. The facts, however, that the phosphatide turnover of neoplastic tissue is much slower than turnover in liver and intestinal mucosa and that phosphatide molecules in the circulation were to a very large extent built up in the liver frustrate this possibility. 

No appreciable difference is found in labeled phosphatide formation of spontaneous and transplanted tumors (80). In both cases, it is appreciably larger than that occurring in muscles, but smaller than that found in 

A detailed investigation of phosphatide metabolism in mammary carcinoma, l5Tnphoma, lymphosarcoma, and sarcoma 180 was carried out by Jones, Chaikoff, and Lawrence (99-101). Four tumors were transplanted into mice. They differed with respect to cell type and rate of growth. Two of the tumors produced metastases in distant parts, whereas the two others remained entirely localized at the place of inoculation. Uniform phosphatide activity was not found in the several types of tumor examined. The activity of lymphoma was only about one-third of that found in mammary carcinoma or lymphosarcoma. Cell type is apparently not a decisive factor in determining extent of phosphatide activity. Each tumor possesses a characteristic phosphatide turnover, which is independent of the host. 

The maximum deposition of phosphatide P in neoplastic tissues may last from 10 to 50 hours. 

In carcinosarcoma 256 the turnover of lecithin is somewhat more rapid than that of cephalin. The mode of behavior of the sphingomyelin fraction was found to be similar to that of cephalin but unlike that of the lecithin fraction of the same tumor (74). The specific activity of sphingomyelin phosphorus increases to a maximum at 48 hours after feeding labeled phosphate. Cephalin shows the same behavior in contrast to lecithin (95). 

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