DNA content of human squamous cell carcinoma cell lines. Analysis by flow cytometry and chromosome enumeration

R. A. Roa, T. E. Carey, P. P. Passamani, J. H. Greenwood, S. Hsu, E. O. Ridings, D. R. Schwartz, G. T. Wolf and J. L. Hudson

Fifteen squamous cell carcinoma cell lines derived from nine patients were examined for DNA content by flow cytometry and chromosome counts. Using human peripheral blood leukocytes and nucleated trout and chicken red blood cells as standards, the DNA indexes of the squamous cell carcinoma cell lines were found to range from 1.1 to 3.3. The DNA content was a stable characteristic of individual cell lines in multiple passages over a seven-month period. Although flow cytometry could detect abnormal DNA content even in diploid tumor lines, the chromosome number correlated well with the DNA content by flow cytometry. In cases in which more than one cell line was established from the same patient, the individual cell lines were found to differ in their DNA content. The cell lines established from metastatic or recurrent tumors usually had a lower DNA content and chromosome number and exhibited a more aggressive in vitro growth pattern than the primary tumor or earlier recurrence. We hypothesize that "streamlined" and aggressive cell populations may evolve in vivo from more slowly growing hyperploid precursor tumor cell populations when in the course of random loss of DNA or chromosomes those that confer no growth advantage are lost, while those that do confer growth advantage are retained.