Abstract
We have established a new cell line, KM-5, which is derived from human squamous cell carcinoma of the lower gingiva. KM-5 cell line is characterized by monolayer growth and polygonal cell shape; the doubling time is approximately 23 hours. Cytokeratin and epithelial membrane antigen (EMA) were immunohistochemically positive, indicating that KM-5 cells were derived from epithelial cells.
The histological appearance of tumors transplanted into nude mice were similar to that of the original tumor, but the nucleus/cytoplasm (N/C) ratio, hyperchromatism and nuclear polymorpholism changed slightly during the process of culture. DNA content and chromosome number were investigated from the origin to 50th passage of KM-5 using flow cytometry and fluorescence in situ hybridization method with centromere specific DNA probes of chromosomes 1, 4, 11, and 17.
DNA index of the original tumor was 1.0, which indicated DNA diploidy; however, those of cell lines from the 2nd to 50th passages were consistently around 1.3, which indicated DNA aneuploidy. DNA index apparently did not change dramatically during cell culture. Numerical aberrations of chromosomes 1, 4, 11, and 17 were observed in each passage. Interestingly, the percentage of monosomy of chromosomes 1 and 11 markedly increased in early phase of cell culture. After the 30th passage, however, this percentage decreased, and the variation of chromosomal aberrations seemed to be the same in these chromosomes. To summarize our results, the time of stabilization seemed to be the 2nd passage for the DNA index, and the 30th passage for numerical aberrations of chromosomes 1, 4, 11, and 17.
