Correlation of in vitro Properties and Tumourigenicity of Hamster Kidney Cells Transformed by BK Virus

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Abstract
Hamster kidney cells transformed by BK virus (HKBK cells) were studied at low passage (.apprx. 30 subcultures) after transformation and at high passage (.apprx. 130 subcultures) after transforming. Several in vitro properties (rescue of virus; presence of T antigen; colony formation on plastic, in soft agar and on monolayers of normal cells; and serum dependency of growth) and tumorigenicity of these cells for newborn and adult hamsters were compared. HKBK cells at low passage showed high levels of T antigen, the growth properties of normal cells and low tumor-producing ability; HKBK cells at high passage showed low levels of T antigen, the growth properties of transformed cells and high tumor-producing ability. Cellular transformation by BK virus may thus be initiated, but not maintained, by the expression of genes regulating T antigen. The maintenance of the transformed state evidently is due to complicated cellular and viral gene interactions occurring during cell life.