Comparison of the sulforhodamine B assay and the clonogenic assay for in vitro chemoradiation studies

Cancer Chemother Pharmacol. 2003 Mar;51(3):221-6. doi: 10.1007/s00280-002-0557-9. Epub 2003 Jan 22.


Purpose: Since there is a growing interest in preclinical research on interactions between radiation and cytotoxic agents, this study focused on the development of an alternative to the very laborious clonogenic assay (CA).

Methods: The colorimetric sulforhodamine B (SRB) assay was compared to the clonogenic assay for radiosensitivity testing in two lung cancer cell lines (A549, H292), one colon cancer cell line (HT-29) and one breast cancer cell line (MCF-7). In addition, the combination of the radiosensitizing agent gemcitabine and radiation was investigated with both assays.

Results: The dose-response curves obtained with the SRB assay and the CA were very similar up to 6 Gy. The radiosensitivity parameters (SF(2), alpha, beta, MID and ID(50)) obtained from the SRB assay and the CA were not significantly different between H292, A549 and MCF-7 cells. The radiation dose-response curves for A549 and H292 cells pretreated with 4 n M gemcitabine for 24 h clearly showed a radiosensitizing effect with both assays. The dose-enhancement factors obtained with the SRB assay and the CA were 1.80 and 1.76, respectively, for A549 cells, and 1.52 and 1.41 for H292 cells.

Conclusions: The SRB assay was shown to be as useful as the more traditional CA for research on chemotherapy/radiotherapy interactions in cell lines with moderate radiosensitivity. This assay will be used for more extensive in vitro research on radiosensitizing compounds in these cell lines.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Breast Neoplasms / pathology
  • Colonic Neoplasms / pathology
  • Colony-Forming Units Assay / methods*
  • Colorimetry
  • Combined Modality Therapy
  • Deoxycytidine / analogs & derivatives*
  • Deoxycytidine / pharmacology*
  • Fluorescent Dyes
  • Gemcitabine
  • Humans
  • Lung Neoplasms / pathology
  • Radiation-Sensitizing Agents / pharmacology*
  • Radiotherapy*
  • Rhodamines
  • Sensitivity and Specificity
  • Tumor Cells, Cultured


  • Fluorescent Dyes
  • Radiation-Sensitizing Agents
  • Rhodamines
  • Deoxycytidine
  • lissamine rhodamine B
  • Gemcitabine