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Collagen Synthesis by Cloned Mouse Mammary Tumor Cells¹

Department of Cell and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30902 [R. A. R., D. F. S., E. F. H.] and Department of Biochemistry, School of Medicine, University of Vermont, Burlington, Vermont 05401 [K. R. C.]

Neoplasms require stroma to support their growth. Collagen is the major protein of stroma, and its biosynthesis is an important event in the development and growth of tumors. Collagen synthesis is generally considered to be a property of fibroblasts. However, the cell type responsible for collagenous stroma formation in neoplastic tissue has not been fully identified. In an attempt to answer this question, we compared the collagen-synthetic activity of three cloned cell lines that were derived from mouse mammary carcinomas with that of cultured mouse fibroblasts. Cells were analyzed for activity of prolyl hydroxylase, the enzyme responsible for the formation of hydroxyproline in collagen. The cells were also incubated with L-[U-¹⁴C]proline in the presence of 2 x 10^-4 M sodium ascorbate, and the amount of collagenase-digestible protein was determined. In addition, the rate of hydroxyproline formation was determined. All three parameters of collagen synthetic activity indicated that the mammary tumor cell lines synthesize collagen. However, the amount of collagen synthesized relative to noncollagen protein was lower than in the fibroblast cultures. Cells from solid tumors derived after the s.c. injection of the tumorigenic cell lines into isogeneic mice were obtaiend, and prolyl hydroxylase activity and collagenase-digestible protein were determined. The results indicated that the primary cells derived from the solid tumors synthesized approximately the same amount of collagen relative to noncollagen protein as did their respective cell lines growing in culture. The primary cells also had a similar level of prolyl hydroxylase activity, as did the cultured cells.

¹ Supported by Program Project Research Grant CA-17059 from the National Cancer Institute and also Grant AM-16216. A preliminary report of this work has been published (28).

² Some of this work was done in partial fulfillment of the requirements for the Ph.D. degree at the Medical College of Georgia. To whom requests for reprints should be addressed at the Medical College of Georgia, Box 420, Augusta, Ga. 30902.

³ Recipient of Research Career Development Award AM 00120.

Received 3/13/78. Accepted 6/27/78.