Cell division in medium lacking serum growth factor: comparison of lines transformed by different agents.

Abstract

CELLS of the permanent lines derived from mouse embryo tissue, 3T3 and Balb/c 3T3, exhibit density dependent inhibition of cell division1,2 anchorage dependence3,4, and also require a factor in serum to initiate DNA synthesis5–8, but these growth controls4,6,9–11 are lost in transformed cells. It has been suggested that loss of density dependent inhibition is a consequence of the loss of a requirement for serum factor6, in which case it would be expected that transformed lines derived from 3T3 would lack both growth controls. We have therefore tested various transformed lines of Balb/c 3T3 lacking the density dependent inhibition for the ability to grow without this serum factor or factors. Both virus-transformed lines of Balb/c 3T3 and independent isolates of Balb/c 3T12 (see ref. 2) grow well in medium lacking the serum growth factor(s), but most non-virus-transformed variants of Balb/c 3T3 grew poorly if at all. These observations suggest that the loss of density dependent inhibition of growth does not necessarily depend on the loss of the need for serum growth factor.