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Surface Membrane Nucleoside Triphosphatase Activity and Tumorigenicity of Cultured Liver Epithelial Cells¹

Institut du Cancer de Montréal, Centre Hospitalier Notre-Dame, Montréal, H2L 4M1 and Département d'Anatomie, Université de Montréal, Canada [S. K.], and Pasadena Foundation of Medical Research, Pasadena, California 91101 [T. O.]

A cell surface-located nucleoside triphosphatase activity can be assayed in liver epithelial cultures in situ with the incubation of intact cells in a medium containing [-³²P]adenosine triphosphate and correlated with the tumorigenicity of these cells in neonatal Wistar rats. The ectoenzyme activity of normal diploid cell lines is minimal, whereas a considerably high activity has been found in all tumorigenic cell lines tested. The optimum condition for the adenosinetriphosphatase activity is physiological with regard to osmolarity, ionic composition, pH, and substrate concentration in the medium. The enzyme is significantly stimulated by Ca²⁺, and its activation is controlled by Mg²⁺. Histochemical examinations indicate that glutaraldehyde-fixed cells of tumorigenic lines have Ca²⁺-stimulated adenosinetriphosphatase activity on the external surface. The isotopic assay of adenosine triphosphate hydrolysis by intact cells may provide a rapid method for screening oncogenesis in vitro of liver epithelial cells.

¹ This work was supported by grants from the National Cancer Institute of Canada, le Ministère des Affaires Sociales du Québec, La Fondation J. H. Biermans, Les Fondations J. Rhéaume, and by USPHS Grant CA-13376.

² Research Associate of the National Cancer Institute of Canada. To whom requests for reprints should be addressed, at Institut du Cancer de Montréal, Centre Hospitalier Notre-Dame, Montréal, Canada H2L 4M1.

Received 5/ 4/76. Accepted 9/ 1/76.

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