Establishment and characterization of a rat lung adenocarcinoma cell line with low malignant potential

To investigate characteristic of lung adenocarcinoma growth behavior, we have established a cell line (rat lung cancer in Nara (RLCNR)) from a tumor induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in a rat. This clone shows an epithelial cell morphology and grows as sheets in culture with an approximate doubling time of 19.2 h. Ultrastructurally, the RLCNR contains lamellar bodies in cytoplasm and the microvilli are present at the free cell surfaces. The line features well-developed desmosomes. The modal chromosome number of 42 is the same as for normal rat cells and its frequency was established to be 80.5%. To evaluate tumorigenicity, appropriate numbers of the cells were transplanted into syngeneic rats, but no tumor formation occurred. Genetic analyses revealed the RLCNR to have a GGT to GAT mutation at codon 12 of Ki-ras, but no p53 alteration. p16 gene expression was lost, associated with hypermethylation of CpG sites in the 5′ upstream region of the gene. These results indicate that the present newly established cell line originated from an alveolar type II lesion of the lung. It should be useful for further investigation of in vivo growth mechanisms, especially tumor progression, of lung adenocarcinomas, since it has low malignant potential.