Cell hybrid analysis of the presence of G1 in early and late passage ‘lung’ and ‘liver’ cells

Previous studies have shown that when different naturally occurring cells that display a measurable G1 during logarithmic growth (G1⁺ cells) were hybridized, the resulting hybrids often lacked G1 (G1⁻ cells). This has been termed complementation. Four established G1⁺ lines of Chinese hamster were found to define three G1⁺ complementation groups. Three of these lines have been hybridized with early and late passage fibroblast-like cells from the lung and liver of a Chinese hamster newborn. The complementation tests indicate: 1. that the basis for the expression of G1 of the ‘lung’ cultures is different than that of the ‘liver’ cells 2. that late passage (transformed) cells retain the same basis for G1 as their ‘ancestral’ early passage cells. These results show that presumably different cells can express G1 for different reasons, which in turn might be related to cellular differentiation.