Separation and characterization of the neoplastic and stromal elements of the R3230AC mammary adenocarcinoma.

The purification of the various types of cells in solid tumors is necessary for study of their biochemical and immunological functions. The R3230AC adenocarcinoma contains both a variety of stromal cells and well-differentiated neoplastic cells that possess many of the biosynthetic capabilities of normal rat mammary cells. Suspensions of cells from tumors weighing less than 1.2 g consisted of 70.4 +/- 7.2% (S.D.) malignant cells by morphology, 6.8 +/- 3.0% lymphocytes, 6.3 +/- 3.2% macrophages, 15.2 +/- 5.2% red blood cells, 0.8 +/- 0.5% granulocytes, and 0.5 +/- 0.6% unidentified cells. Sedimentation of the cells from the R3230AC tumor in a previously described isokinetic gradient resulted in a 5- to 6-fold purification of lymphocytes and macrophages. The modal fraction of malignant cells contained 95.3 +/- 2.9% malignant cells. Detection of alpha-lactalbumin by the direct peroxidase conjugate technique gave vacuolar staining of malignant cells, in contrast to the indirect and peroxidase-antiperoxidase techniques which stained ducts from normal lactating mammary gland and a wide variety of cells without vacuoles in the tumor. The best fixative for frozen sections, paraffin-embedded tissue, and cell suspensions was 50% ethanol-50% acetone. The suspensions of tumor cells contained 14.4 +/- 9.4% cells with histochemically demonstrable alpha-lactalbumin. Squamous metaplasia was commonly observed in tumors than lactating rats.