A biological assay using the chorioallantoic membrane (CAM) of the chicken egg as an in vitro culture system has been developed and standardized in order to assess the androgen responsiveness of normal and abnormal prostatic tissue. In this assay, test tissue is implanted onto the CAM of chicken eggs in the presence or absence of exogenous testosterone treatment, with subsequent serum levels of 45 ng./dl. and > 5,000 ng./dl., respectively. The responsiveness of test tissue to low versus high androgen levels was evaluated in this CAM assay using both cellular morphology and mitotic index as response criteria. Both androgen responsive and unresponsive tissues from the rat were grown on the CAM and demonstrated appropriate morphologic and proliferative responses to the presence and absence of testosterone supplementation. Human prostatic adenocarcinoma and benign hyperplastic tissues were also grown successfully on the CAM. Documentation of human tissue survival was performed by immunocytochemical analysis for prostate specific antigen and prostate specific acid phosphatase. The human prostatic adenocarcinomas studied demonstrated a two to four-fold increase in mitotic index with androgen augmentation. In conclusion, the ability of this assay to determine androgen responsiveness as measured by morphologic and proliferative criteria has been documented in rat tissues. Human prostatic adenocarcinoma has been grown consistently on the chick chorioallantoic membrane for the first time using newly developed techniques. Therefore, this technique shows promise in the clinical application for the determination of the androgen responsiveness of human prostatic carcinomas.
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