CHANGES IN DNA CONTENT OF RAT TRACHEAL EPITHELIAL-CELLS DURING NEOPLASTIC PROGRESSION INVITRO

Flow cytometric DNA analysis was used to compare nuclear DNA content of carcinogen [7,12-dimethylbenz[a]anthracene, N-methyl-N''-nitro-N-nitrosoguanidine, 12-O-tetradecanoylphorbol-13-acetate]-induced F-344 rat tracheal epithelial cell lines [1000W cells, 165D cells, 165(2-4) cells, 165(3-5) cells, 8-10-2 cells, 8-1-2 cells, 2-10-1 cells, 3F3 cells] as they progressed from non-tumorigenic (preneoplastic) to tumorigenic (neoplastic) populations in vitro. Normal tracheal cell populations were used as diploid reference cells. All of the tracheal epithelial cell lines established from carcinogen-treated tracheas showed increases in nuclear DNA content compared to normal cell populations. For 5 cell lines, measurements were made during the preneoplastic state and after conversion to the neoplastic state. Four of the 5 cell lines showed a major shift in DNA content as the culture progressed from preneoplastic to neoplastic populations. There was no consistent change in DNA content as cultures progressed to neoplastic populations in vitro. Two cell lines showed shifts to higher levels as the cultures became tumorigenic, while 2 showed shifts to lower levels. Two cell lines (3F3 and 165D) had DNA distribution profiles indicative of mixed cell populations during the neoplastic phase. Cloning experiments of cell line 3F3 confirmed that those cells having a model DNA value the same as that of their preneoplastic progenitor populations were non-tumorigenic. Evidence that such shifts in DNA content correlate with comparable changes in chromosome number was presented for the 3F3 cell line. The transition from preneoplastic tracheal epithelial cells to neoplastic populations is often associated with a change in DNA content. The malignant cell type probably emerges as a new cell type from preneoplatic progenitor populations.