Abstract
The literature contains numerous reports of attempts to isolate from various normal tissues substances which are inhibitory to the growth of malignant tumors. The majority of these reports indicate highly variable results. Since it is generally known that malignant tumors rarely originate in the small intestine, the present work has been concerned primarily with efforts to derive inhibitory material from this organ. Previous work with this tissue has involved chemical extraction of material from the whole organ(1). In the present studies, ultracentrifugal fractionation has been employed. Similar methods have been used successfully in the separation of hemolytic and antihemolytic substances from liver(2).
Results of preliminary investigations based on centrifugal fractionation are reported in this communication.
Materials and methods. Small intestinal tissue of normal mice or rats was frozen on dry ice, then thawed and ground with sand. A saline suspension of this homogenate was fractionated in the following manner. A fraction corresponding to the mitochondrial-nuclear fraction of normal tissue(3) was separated by centrifugation for 10 to 20 minutes at 4000 x g (Fraction 4). The supernate from this was further centrifuged for 45 to 60 minutes at 90000 x g to yield a microsomal fraction (Fraction 90). The fractions were prepared for use by resuspending in saline. Fractions 4 and 90 and the supernatant from the latter were tested for inhibitory action on lymphosarcoma (Gardner). Lymphosarcoma cells in saline suspension were incubated in vitro at 5°C for 10 to 20 minutes with an equal volume of the tissue fraction suspensions described above. Two-tenths ml of these tissue fraction-tumor cell incubates was inoculated subcutaneously in CBA mice (Strong). Controls received saline-tumor cell inoculations.
Results. Results are summarized in Tables I and 11. The technic employed yielded 100% takes of the tumor in 124 control mice. Tumors developed to palpable size in 4 to 7 days and death ensued in 17 to 2 7 days after inoculation.
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