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Elevation of Peptidylproline Hydroxylase Activity and Collagen Synthesis in Spontaneous Primary Mammary Cancers of Inbred Mice¹

Department of Cell and Molecular Biology, Medical College of Georgia, Augusta, Georgia 30902

Parameters of collagen biosynthesis were determined in mammary cancer tissue. Peptidylproline hydroxylase (PPH) activity was determined in spontaneous primary mammary cancer tissue and normal mammary gland in fat pad. The enzyme was located in the 105,000 x g supernatant of whole-tissue homogenates. Ascorbate, -ketoglutarate, and ferrous ion were required for enzyme activity of cancerous and control tissues. The activity of PPH of cancer tissue from five high-mammary-cancer strains of inbred mice was 3- to 5-fold higher than the level of enzyme activity in normal mammary gland in fat pad of animals of comparable age. As a second parameter of collagen-biosynthetic rate of cancer tissue and specifically the PPH step, the rate of formation of hydroxyproline-¹⁴C from uniformly labeled proline-¹⁴C was determined in vitro. A positive correlation was observed between elevation of enzyme activity and collagen-biosynthetic capacity of cancerous tissue from the C3H⁺ strain of inbred mice. The elevation of collagen biosynthesis and PPH activity during spontaneous mammary gland carcinogenesis support further investigations of the collagen-biosynthetic pathway as a possible biochemical target for chemotherapy of this disease and the activity of PPH activity as a possible biochemical parameter of mammary gland tumorigenesis.

¹ This investigation was supported by USPHS Research Grant AM 16216-01 from the National Institute of Arthritis and Metabolic Diseases and grants from Research Corporation and the Southern Medical Association. Some of the data in this manuscript were presented at the 1972 Spring meeting of the American Association for Cancer Research held in Boston, Mass., and appear in abstract form (3).

Received 6/21/72. Accepted 9/14/72.