Radiation Response and Characteristics of a Cell Line Derived from a Mouse Mammary Adenocarcinoma

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Abstract
Cells derived from a primary explant of a C3H/Bi mouse mammary adenocarcinoma (MADCAP 37) were grown continuously in culture. The cells have a doubling time of 24 h and retained their carcinomatous character. They have a large degree of aneuploidy. The plating efficiency in McCoy''s 5A media alone is 6%. It is increased to 38% with addition of an irradiated feeder layer. The average number of cells required to produce tumors in 50% of the sites injected (TD50) is 732 cells compared to the TD50 of 2500 cells for source tumor cells. The tumor produced is an invasive, undifferentiated carcinoma consisting of anaplastic, hyperchromatic epithelial cells which is histologically similar to the source tumor. The radiation response of tumor cells irradiated and assayed in vitro is characterized by a Do of 120 rad, a Dq of 100 rad and an extrapolation number of 2.3. When the cells were assayed in vivo, the Do was increased to 220 rad. The radiosensitivity of the MADCAP 37 tumor and the C3H tumor of origin, evaluated by TCD50 studies, was similar.