Alterations in growth phenotype and radiosensitivity after fractionated irradiation of breast carcinoma cells from a single patient

Int J Radiat Oncol Biol Phys. 1993 Apr 30;26(1):81-8. doi: 10.1016/0360-3016(93)90176-v.


Purpose: To investigate growth regulation and radiosensitivity in surviving clonogens after fractionated irradiation.

Methods and materials: Four breast carcinoma cell lines isolated from the primary tumor (21NT, 21PT) and metastases (21MT-1, 21MT-2) of a single patient were exposed to cumulative radiation doses of 30 Gy yielding cell lines designated-IR with respect to their parent. The irradiated lines were then compared to their parent for serum-and growth factor-requirements under defined media conditions, ability to proliferate in soft agar, concentration of TGF-alpha in conditioned medium, and radiosensitivity.

Results: The irradiated lines showed no change in proliferative doubling times under serum- and growth factor-supplemented media conditions. A single line, 21MT-1-IR, acquired a limited ability to proliferate in serum-and growth factor-deplete medium with a day 2-4 doubling time of 44.5 hr. Three lines, 21MT-1-IR, 21MT-2-IR, and 21NT-IR, formed colonies in soft agar in contrast to none of the unirradiated parent lines. There were significant 6-8 fold increases in conditioned media TGF-alpha concentrations for 21MT-2-IR and 21NT-IR cells. The 21MT-1-IR and 21NT-IR cells were significantly less radiosensitive than their respective parent lines. This decrease in radiosensitivity appeared to be at least partially mediated by a released factor as the radiosensitivity of 21MT-1 cells was significantly decreased by pre-incubation with conditioned medium from 21MT-1-IR cells.

Conclusion: Radiation-induced changes in growth phenotype vary with respect to clonal origin of the cell line and may influence the radiosensitivity of surviving clonogens after fractionated treatment.

MeSH terms

  • Breast Neoplasms / pathology*
  • Cell Division / radiation effects*
  • Dose-Response Relationship, Radiation
  • Female
  • Humans
  • In Vitro Techniques
  • Phenotype
  • Radiation Tolerance / physiology*
  • Transforming Growth Factor alpha / metabolism
  • Tumor Cells, Cultured / radiation effects*


  • Transforming Growth Factor alpha