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Stimulation of Mammary Tumor Virus Production in a Mouse Mammary Tumor Cell Line¹

Department of Cytological Biophysics, Institute for Medical Research, Camden, New Jersey 08103

A mouse mammary tumor cell line (MMT), which has shown since its isolation in 1962 a limited, but continuous, budding of B particles, was stimulated to high production by alternate passages of the cells through mice or rats and tissue culture. Newborn C57BL, Af, and A mice and Amsterdam/IMR rats have been used as transient hosts. Detection and semiquantitative estimations of virus production in the cultures were made by thin-section electron microscopy, whole-cell-mount electron microscopy, membrane immunofluorescence, and immunodiffusion.

Passage of the MMT cells into mice and back to tissue culture stimulated a 4-fold increase of B particle production but remained subject to variations in successive subcultures. Passage of the MMT cells into rats stimulated a 25- to 30-fold increase; budding of the virions remained constant and the tumor-inducing capabilities were high through multiple subcultures. The greater stability in pH and even rate of growth of the rat-passaged cells opens the possibility of producing in tissue culture a mammary tumor virus of greater reliability and purity than that obtained from milk or tumor extracts.

¹ Presented in part at the 59th Annual Meeting of the American Association for Cancer Research, Atlantic City, N. J., March 1968. Supported by USPHS Grants CA-08515 and CA-08740 from the National Cancer Institute.

Received 8/ 1/69. Accepted 12/ 5/69.