Transformation of rat embryo cells in culture by polyoma virus

Abstract

This chapter describes some of the methods of observation which have been used to detect and quantitate changes in cultured cells infected by known tumor viruses. The longest and perhaps best known examples of tumor viruses are found among the C-type RNA-containing group. Structurally, these viruses consist of an inner nucleoprotein core, containing approximately 10 million daltons of RNA, and an outer membrane envelope. Avian and murine viruses of this group are well established as agents causing various leukemias and sarcomas in their natural hosts. In contrast to the RNA tumor viruses which form a single structural class, DNA-containing tumor viruses are known from several distinct families possessing marked differences in size and structure. Herpes and poxviruses form the two major classes of enveloped DNA viruses. Five general properties reflecting alterations in regulation and patterns of cell growth have been particularly useful in detecting, isolating, and characterizing cells transformed by tumor viruses: (1) morphological alterations, (2) decreased density dependent inhibition of growth, (3) decreased serum requirement for growth, (4) ability to grow in semisolid suspension cultures, and (5) tumorigenicity. Changes in one or some combination of the first four properties form the bases for essentially all viral transformation assays with DNA and RNA viruses.