Abstract
Summary
Two tumors, medullary carcinomas from human thyroid glands, were used to establish tissue culture lines. These lines were assayed for alkaline phosphatase activity and were found to be consistently positive. Following transformation of the cell lines with SV40, the alkaline phosphatase levels were markedly depressed or undetectable. When hydrocortisone was added to the in vitro system, the enzyme activity returned to preinfection levels. This increase in alkaline phosphatase was dependent on the continuous presence of steroid; when steroid was withdrawn there was a loss of activity to pretreatment levels. No increase in enzyme levels was detected in uninfected tumor cells treated with hydrocortisone.
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