Abstract
The relationship of cytogenetic changes with the acquisition of an indefinite life span in vitro, the ability of cells to grow in soft agar and their tumourigenicity in syngeneic animals has been studied in control, trans-7,8-dihydrodiolbenzo(a)pyrene and 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)-pyrene-treated secondary cultures derived from Chinese hamster embryonic lung. Karyotype analysis revealed a sequence of chromosome changes as the cells progressed through culture. Aneuploidy, namely trisomy of chromosome 4, the long arm in particular, was an early dominant change. The possible association of this trisomy with the acquisition of immortality in vitro is implicated, although the involvement of other nonrandom chromosome changes cannot be eliminated, implying that there may be several genomic sites in the Chinese hamster which may potentially be involved with the acquisition of unlimited growth potential. Neither the ability of cells to grow in soft agar nor as tumours could be associated with any specific chromosome(s). Double minutes were observed in metaphases from the cell lines, agar colonies and tumours; their possible relationship with growth advantage is discussed.
Highlights
MethodsPrimary cultures were initiated from small fragments of foetal lung pooled from nine Chinese hamster embryos isolated on the 14th day of gestation
Neither the ability of cells to grow in soft agar nor as tumours could be associated with any specific chromosome(s)
Double minutes were observed in metaphases from the cell lines, agar colonies and tumours; their possible relationship with growth advantage is discussed
Summary
Primary cultures were initiated from small fragments of foetal lung pooled from nine Chinese hamster embryos isolated on the 14th day of gestation. The cultures were initiated in 75 cm plastic culture flasks (Nunclon, Roskilda, Denmark) in Dulbecco's minimal essential medium (DMEM) supplemented with 10% foetal bovine. Cultures were maintained at pH7.2+0.2 by gassing with 10% CO2 in air and were cultured at 37°C. The culture medium (CM) was changed every day until the first subculture. Following the initial subculture the cultures were termed 'secondary cultures'; and when they had obviously overcome senescence and had expressed unlimited growth potential in vitro, they were termed 'cell-lines'. The cultures were screened, using the method of Chen (1977), on a regular basis for mycoplasma contamination.
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