Relation of DNA ploidy and proliferation rate to radiation sensitivity in squamous carcinoma cell lines.

OBJECTIVE

According to some clinical reports, DNA aneuploidy of squamous cell carcinomas is related to a more favorable response to radiotherapy than DNA diploidy, but it is not known whether this depends on differences in intrinsic cellular radiation sensitivity or on other factors involved during the course of radiotherapy.

DESIGN

Using flow cytometry, we analyzed 30 newly established squamous carcinoma cell lines derived from head and neck carcinoma, and compared the nuclear DNA content with the inherent radiosensitivity and with the average doubling time determined from the in vitro growth curves.

RESULTS

The nuclear DNA content expressed as the ratio between the Go/G1 peak of the cell line and the peak formed by chicken red blood cells varied from 3.13 to 6.41. The DNA content of cells obtained from nonmalignant lesions by fine-needle aspiration biopsy was from 2.66 to 2.80. No correlation was found between the nuclear DNA content and the inherent radiosensitivity of the carcinoma cells.

CONCLUSIONS

The result suggests that the intrinsic cellular radiosensitivity of carcinomas does not increase in parallel with an increasing nuclear DNA content. Nor does the in vitro proliferation rate associate with either the nuclear DNA content or inherent radiosensitivity.