This paper describes two autonomous variants derived from originally androgen/estrogen-induced and hormone-dependent leiomyosarcomas of ductuli deferentia of Syrian hamsters. The selection of autonomous variants from an assumed heterogeneous population of tumor cells with varying degrees of hormone dependency was facilitated by withdrawal of hormone support from transplanted tumors, thereby handicapping proliferation and survival on the part of the most dependent cells. Neither long-term storage in liquid nitrogen nor repetitive in vivo-in vitro cultivation facilitated such selection.

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This investigation was supported by USPHS Research Grant CA-04516 from the National Cancer Institute.

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